ORBITAL SCIENCES CORP /DE/
8-K, 1995-11-02
GUIDED MISSILES & SPACE VEHICLES & PARTS
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               SECURITIES AND EXCHANGE COMMISSION

                     Washington, D.C. 20549


                    ________________________



                            FORM 8-K

                         CURRENT REPORT


                Pursuant to Section 13 or 15(d)
             of the Securities Exchange Act of 1934


Date of Report (Date of earliest event reported):  August 31, 1995



                    ________________________



                  ORBITAL SCIENCES CORPORATION

    Delaware             0-18287             06-1209561
   (State of         (Commission File     (I.R.S. Employer
 incorporation)          Number)             I.D. No.)

                  21700 Atlantic Boulevard
                   Dulles, Virginia 20166
                       (703) 406-5000
                (Address and telephone number
               of principal executive offices)



Item 5.   Other Events

     On August 31, 1995, Orbital Sciences Corporation ("Orbital"
or  the  "Company")  executed an agreement to acquire  MacDonald,
Dettwiler and Associates Ltd. ("MDA"), a high technology  company
specializing  in the design, manufacture and marketing  of  space
remote  sensing  ground stations capable of  handling  all  major
optical and radar imaging for Earth observation satellites.   MDA
is  also  a  major provider of advanced space-qualified software,
air  navigation systems, defense electronics systems and  network
communications training and consulting.  MDA's Common Shares  are
publicly  traded on the Vancouver Stock Exchange and The  Toronto
Stock Exchange.

The acquisition is expected to be concluded by December 31, 1995.
Pursuant  to  the  terms of the agreement, a  newly  established,
wholly   owned   Canadian  subsidiary  of  Orbital   will   issue
Exchangeable   Shares  in  exchange  for  all  the   issued   and
outstanding  MDA Common Shares.  These Exchangeable  Shares  will
have voting and economic rights with respect to Orbital identical
to  Orbital  Common Stock, and will be exchangeable into  Orbital
Common  Stock  at the option of the holders, subject  to  certain
regulatory restrictions.

The  actual  number  of shares of Orbital Common  Stock  issuable
pursuant  to the agreement is based on the average closing  sales
price of Orbital's Common Stock for the 20 trading days ending on
the date four trading days prior to closing.  Assuming an average
closing sales price of $17.25 per share for Orbital Common  Stock
and  an  exchange ratio of .31 Orbital Common Stock to  1.00  MDA
Common  Share, Orbital expects to issue approximately 3.9 million
shares  of  its  Common  Stock  for  all  of  MDA's  issued   and
outstanding  voting  common shares and  employee  share  options.
Pursuant  to  the  agreement, Orbital will assume  all  of  MDA's
outstanding common share options, which vest in variable  amounts
over the next four years.

The acquisition will be accounted for using the pooling of
interests method of accounting.

Item 7.   Financial Statements and Exhibits

     (a)       (i)  Consolidated Financial Statements of
MacDonald, Dettwiler and Associates Ltd., together with report of
the independent auditors, as of March 31, 1995, 1994 and 1993;
and

          (ii)  Unaudited Consolidated Financial Statements of
MacDonald, Dettwiler and Associates Ltd. as of June 30, 1995 and
for the three-month periods ended June 30, 1995 and 1994.

     (b)  Pro Forma Financial Information of Orbital Sciences
Corporation

          (i)  as of and for the six-month period ended June 30,
1995; and

          (ii)  for the years ended December 31, 1994, 1993 and
1992.

     (c)  Exhibits.  The following exhibits are filed as part of
this report:

     Exhibit
     No.

          2    Combination Agreement dated as of August
          31, 1995 among Orbital Sciences Corporation,
          3173623 Canada Inc. and MacDonald, Dettwiler
          and Associates Ltd. (transmitted herewith)

          2.1  Plan of Arrangement under Section 192 of
          the Canada Business Corporations Act
          (transmitted herewith)

          2.2  Voting and Exchange Trust Agreement
          between Orbital Sciences Corporation,
          MacDonald Dettwiler Holdings Inc. And State
          Street Bank and Trust Company (transmitted
          herewith)

          2.3  Support Agreement between Orbital
          Sciences Corporation and MacDonald, Dettwiler
          Holdings, Inc. (transmitted herewith)

          2.4  Notice of Special Meeting of
          Shareholders and Holders of the 1988 Employee
          Share Options and the 1988 Key Employee Share
          Options of MacDonald, Dettwiler and
          Associates Ltd. and Management Information
          Circular dated as of October 6, 1995
          (transmitted herewith)

          23   Consent of KPMG Peat Marwick Thorne
          (transmitted herewith)
                                
                                
                                
                                
            MACDONALD, DETTWILER AND ASSOCIATES LTD.
                CONSOLIDATED FINANCIAL STATEMENTS
                                
        For the Years ended March 31, 1995, 1994 and 1993
                                
              (including Auditors' Report thereon)
                                
                                
        For the Three Months ended June 30, 1995 and 1994
                           (Unaudited)
<PAGE>
                    MDA FINANCIAL STATEMENTS

               AUDITORS' REPORT TO THE DIRECTORS


We  have  audited the consolidated balance sheets  of  MacDonald,
Dettwiler and Associates Ltd. as at March 31, 1995 and  1994  and
the  consolidated statements of earnings, retained  earnings  and
changes in financial position for each of the years in the  three
year period ended March 31, 1995.  These financial statements are
the    responsibility   of   the   Company's   management.    Our
responsibility  is  to  express an  opinion  on  these  financial
statements based on our audits.

We  conducted  our  audits in accordance with generally  accepted
auditing  standards.  Those standards require that  we  plan  and
perform  an  audit  to  obtain reasonable assurance  whether  the
financial statements are free of material misstatement.  An audit
includes  examining,  on  a test basis, evidence  supporting  the
amounts  and disclosures in the financial statements.   An  audit
also  includes  assessing  the  accounting  principles  used  and
significant  estimates made by management, as well as  evaluating
the overall financial statement presentation.

In  our  opinion, these consolidated financial statements present
fairly, in all material respects, the financial position  of  the
Company  as  at  March 31, 1995 and 1994 and the results  of  its
operations and the changes in its financial position for each  of
the  years  in  the  three year period ended March  31,  1995  in
accordance with generally accepted accounting principles.







Vancouver, Canada               (signed) KPMG Peat Marwick Thorne
May 25, 1995, except as to                  Chartered Accountants
Note 8(d) which is as
at September 29, 1995
<PAGE>
<TABLE>
<CAPTION>
             MACDONALD, DETTWILER AND ASSOCIATES LTD.

                   Consolidated Balance Sheets
                    (In thousands of Canadian dollars)

                                                  
                                         June 30,            March 31,
                                           1995          1995        1994
                                        (Unaudited)     _____        _____
<S>                                    <C>             <C>          <C> 
                  Assets
Current assets:                                                   
     Cash and term deposits                 $16,845       $ 9,463     $12,008
     Receivables                             22,518        30,484      33,104
     Recoverable income taxes                   275           221       1,443
     Inventories                                817           486         488
     Prepaid expenses                         1,193         1,011       1,407
         Total current assets                41,648        41,665      48,450
                                                                             
Lease receivable                              1,171         1,186       1,415
Investment                                      586           586         586
Fixed assets (Note 2)                        10,597        10,939      10,342
Goodwill                                      7,865         8,005       2,339
Deferred income taxes                           191           184           -
                                            $62,058       $62,565     $63,132
                                                                             
                                                                             
 Liabilities and Shareholders' Equity                                        
                                                                             
Current liabilities:                                                         
     Accounts payable and accrued           $11,803       $12,118     $14,655
     liabilities
     Deferred revenue                        19,813        21,204      26,553
     Current portion of long-term                                            
     debt and obligations under                                              
     capital leases (Note 3)                  1,224         1,143       1,043
                                                                             
     Deferred income taxes                        -             -         297
          Total current liabilities          32,840        34,465      42,548
                                                                  
Long-term debt and obligations under                                         
     capital leases (Note 3)                  8,197         8,052       4,334
                                                                             
Shareholders' equity:                                                        
     Capital stock (Note 4)                   8,107         8,052       7,969
     Contributed surplus                      2,050         2,050       2,050
     Retained earnings                       10,549         9,539       6,065
     Cumulative translation                                                  
     adjustment                                 315           407         166
          Total shareholders' equity         21,021        20,048      16,250
                                            $62,058       $62,565     $63,132
Contingencies and commitments (Note 8)                                       
</TABLE>

On behalf of the Board:



  (signed) John W. Pitts            (signed) J. S. MacDonald
         Director                           Director

   See accompanying notes to consolidated financial statements.

<PAGE>
<TABLE>
<CAPTION>
             MACDONALD, DETTWILER AND ASSOCIATES LTD.

               Consolidated Statements of Earnings
         (In thousands of Canadian dollars, except per share data)




                                            Three months               Year  ended March 31
                                            ended June 30
                                          1995        1994        1995        1994          1993
                                             (Unaudited)                                
                                                  
<S>                                      <C>          <C>       <C>          <C>            <C>
Revenues                                   $23,611     $27,605   $109,955     $101,417       $85,156
                                                                                                    
Expenses (Note 7):                                                                                  
     Cost of sales                          15,769      20,459     80,063       75,294        59,705
     General and administrative              2,253       1,941      7,761        6,673         6,689
     Marketing                               3,388       2,687     12,098       10,096         9,448
     Research and development                  438         656      2,381        3,421         4,378
     Interest on long-term debt                 85         102        387          524           488
      and capital lease obligations
     Goodwill amortization                     109         107        435          127           136
                                            22,042      25,952    103,125       96,135        80,844
                                                                                                    
Operating earnings                           1,569       1,653      6,830        5,282         4,312
Other income                                   232         115        637          532              
                                                                                                 634
Earnings before income taxes                 1,801       1,768      7,467        5,814         4,946
Income taxes (Note 6)                          793         778      3,502        2,557         2,177
Net earnings                              $  1,008   $     990  $   3,965     $  3,257     $   2,769
                                                                                                    
Net earnings per common share                                                                       
(Note 5):
     Basic                               $     .09  $      .09 $      .36   $      .29    $      .25
     Fully diluted                       $     .09  $      .08 $      .34   $      .28    $      .24

</TABLE>


   See accompanying notes to consolidated financial statements
<PAGE>
<TABLE>
<CAPTION>


             MACDONALD, DETTWILER AND ASSOCIATES LTD.

           Consolidated Statements of Retained Earnings
                    (In thousands of Canadian dollars)



                                        Three months                     Year ended March 31,
                                       ended June 30,
                                    1995           1994           1995           1994           1993
                                        (Unaudited)                                                      

<S>                                 <C>            <C>            <C>            <C>             <C>
Retained earnings, beginning         $  9,539       $  6,065       $  6,065       $  3,624        $11,820
  of period
Net earnings                            1,008            990          3,965          3,257          2,769
Excess of cost of shares                                                                                 
  purchased and cancelled over
  average issuance price                    2              -          (491)          (816)              -
Dividends on common shares                  -              -              -              -       (10,965)
Retained earnings, end of             $10,549        $ 7,055        $ 9,539        $ 6,065        $ 3,624
  period

</TABLE>
   See accompanying notes to consolidated financial statements
<PAGE>
<TABLE>
<CAPTION>
             MACDONALD, DETTWILER AND ASSOCIATES LTD.

     Consolidated Statements of Changes in Financial Position
                    (In thousands of Canadian dollars)



                                           Three months          Year ended March 31,
                                          ended June 30,
                                         1995       1994       1995       1994      1993
                                          (Unaudited)                   
<S>                                     <C>       <C>       <C>         <C>         <C>    
Operating activities:
    Net earnings                        $  1,008   $    990  $  3,965   $  3,257    $ 2,769
     Items not affecting cash:                                                             
         Depreciation and amortization     1,031        921     3,949      3,384      2,823
         Deferred income taxes               (7)       (19)     (481)      (283)        155
         Loss on disposal of fixed             -          -         5          7          7
          assets
     Net change in non-cash working                                                        
        capital balances relating to       5,635    (2,294)   (3,189)      9,909    (5,259)
          operations
        Cash provided by (applied to)      7,667      (402)     4,249     16,274        495
          operations
                                                                                           
Financing activities:                                                                      
                                                                                           
 Net increase (decrease) in long-term        226      3,908     3,818      (296)         27
        debt and obligations under capital
        leases
     Decrease in other receivables             -          -         -        685        961
     Decrease (increase) in lease             15         13        51    (1,470)          -
        receivable
     Issue of capital stock                   53         11       185        205        358
     Purchase of capital stock                 -      (468)     (593)      (967)          -
     Dividends paid on common shares           -          -         -         -    (10,965)
     Cash provided by (applied to)           294      3,464     3,461    (1,843)    (9,619)
        financing activities
                                                                                           
                                                                                           
       Total cash generated for            7,961      3,062     7,710     14,431    (9,124)
         investing activities
                                                                                           
Investing activities:                                                                      
     Purchase of fixed assets              (579)      (904)   (3,928)    (3,631)    (4,133)
     Acquisition of subsidiary                 -    (6,345)   (6,327)          -          -
     Investment, net                           -          -          -                 (221)
                                                                            (66)
         Cash applied to investing         (579)    (7,249)  (10,255)    (3,697)    (4,354)
           activities
                                                                                           
Increase (decrease) in cash during the     7,382    (4,187)   (2,545)     10,734   (13,478)
        period
Cash, beginning of period                  9,463     12,008    12,008      1,274     14,752
Cash, end of period                      $16,845    $ 7,821  $  9,463    $12,008    $ 1,274

</TABLE>
   See accompanying notes to consolidated financial statements
<PAGE>
1.   Significant accounting policies:

     (a)       Consolidation:

               The consolidated financial statements include  the
        accounts    of   the   Company   and   its   wholly-owned
        subsidiaries.   The Company accounts for  its  investment
        in  Radarsat  International  Inc.  (RSI)  on  the  equity
        basis.    The  Company  considers  RSI  to  be   in   the
        development stage and is capitalizing its share of start-
        up expenditures until commencement of operations.

        All intercompany balances and transactions are eliminated
on consolidation.

     (b)       Recognition of revenue:

               Contract  revenue is recognized on the  percentage
        of  completion basis.  A provision for loss is made  when
        estimated  total  costs are in excess of  total  contract
        revenue.

     (c)       Fixed assets:

               Fixed  assets are stated at cost less  accumulated
        depreciation.     Depreciation   is    applied    on    a
        straight-line basis at the following rates:

               Computers                 20% - 33%
               Equipment                       20%
               Furniture and fixtures          20%
               Software                        25%
               Leasehold improvements   Term of lease

     (d)       Research and development:

               Research  costs are expensed in the year incurred.
        Development  costs  are expensed  in  the  year  incurred
        unless  the Company believes a development project  meets
        generally  accepted accounting criteria for deferral  and
        amortization.   The Company interprets the  criteria  for
        deferral  of development costs on a very stringent  basis
        under  which  interpretation, few,  if  any,  development
        costs  qualify  for  deferral.  In the  current  year  no
        development costs were deferred.

               Research  and  development costs  are  reduced  by
        related government assistance.

     (e)       Investment tax credits:

               Investment tax credits are accounted for using the
        cost  reduction  method and are applied against  cost  of
        sales.

     (f)       Foreign currency translation:

               Foreign operations which are considered integrated
        (financially and operationally dependent on  the  parent)
        are  translated to Canadian dollars using  current  rates
        of   exchange   for  monetary  assets  and   liabilities.
        Historical  rates  of exchange are used for  non-monetary
        assets  and  liabilities and average rates for  the  year
        for  revenues  and  expenses.  Gains or losses  resulting
        from  these  translation  adjustments  are  included   in
        income.

                 Foreign    operations   which   are   considered
        self-sustaining     (financially    and     operationally
        independent  of  the parent) are translated  to  Canadian
        dollars  using the current rates of exchange  for  assets
        and  liabilities and using average rates for the year for
        revenues  and  expenses.  Gains or losses resulting  from
        these  translation adjustments are deferred in a separate
        component    of    shareholders'   equity    ("Cumulative
        translation  adjustment")  until  there  is  a   realized
        reduction  in the parent's net investment in the  foreign
        operation.

               The  Company  considers the  operations  of  Earth
        Observation   Sciences  Limited  to  be  self-sustaining.
        Operations   of   all  other  foreign  subsidiaries   are
        integrated.

     (g)       Goodwill:

               Goodwill  represents the excess  of  the  cost  of
        shares  in  subsidiaries over amounts assigned  to  their
        net identifiable assets. The excess cost is amortized  on
        a straight-line basis over a period of twenty years.

2.   Fixed assets:
<TABLE>
<CAPTION>
                                              June 30, 1995
                                                          
                                                Unaudited
                                Cost            Accumulated             Net
                                                Depreciation
                                 (000's)          (000's)                (000's)
<S>                           <C>             <C>                  <C>
Computers                          $13,507            $10,141          $  3,366
Equipment                            2,831              1,975               856
Furniture and fixtures               3,096              2,403               693
Leasehold improvements               7,630              2,828             4,802
Software                             2,640              1,760               880
                                   $29,704            $19,107           $10,597
<CAPTION>

                                                 March 31, 1995

                                 Cost            Accumulated              Net
                                                 Depreciation
                                                                                    
                               (000's)             (000's)             (000's)
<S>                            <C>              <C>                    <C>
Computers                          $13,124            $ 9,557           $ 3,567
Equipment                            2,734              1,906               828
Furniture and fixtures               3,095              2,344               751
Leasehold improvements               7,632              2,678             4,954
Software                             2,513              1,674               839
                                   $29,098            $18,159           $10,939
<CAPTION>                                                                                    
                                              March 31, 1994

                                Cost             Accumulated            Net
                                                 Depreciation
                                                                   
                               (000's)           (000's)               (000's)
                              <C>               <C>                   <C>                                                
Computers                          $10,408            $ 7,160           $ 3,248
Equipment                            2,248              1,663               585
Furniture and fixtures               2,795              2,103               692
Leasehold improvements               7,343              2,128             5,215
Software                             2,008              1,406               602
                                   $24,802            $14,460           $10,342
</TABLE>

     Total assets under capital leases included above have a cost
     of   $2,400,000  at  March  31,  1995  (March  31,  1994   -
     $2,513,000) and a net book value of $1,721,000 at March  31,
     1995 (March 31, 1994 - $1,785,000).

3.   Long-term debt:
<TABLE>
<CAPTION>
                                               June 30,        March 31,
                                                 1995       1995      1994
                                              (Unaudited            
                                                (000's)    (000's)   (000's)
<S>                                           <C>          <C>       <C>
Promissory note payable, interest at
  6.8%, principal and interest repayable                                     
   at $35,000 monthly                               $2,428  $2,490     $2,730
Western Economic Diversification                                             
  loan, non-interest bearing, repayable                                      
  in annual installments commencing June                                     
  30, 1996 and ending June 30, 2005                  1,230   1,188        802
Term loan, interest at 10.5%, payable                                        
  monthly, principal repayable in full on                                    
  or before July 15, 1996                            3,750   1,850          -
Obligations under capital leases.                    2,013   1,667      1,845
                                                                             
                                                     9,421   9,195      5,377
Deduct current portion                               1,224   1,143      1,043
                                                                             
                                                    $8,197  $8,052     $4,334

</TABLE>

     Long-term debt is secured by a fixed and floating charge  on
     all  Company assets and by charges and chattel mortgages  on
     specific equipment.

        (a)    Future  minimum lease payments due  under  capital
        leases at March 31, 1995 are as follows:

                                                  (000's)
               1996                               $ 1,023
               1997                                   588
               1998                                   257
               Total minimum lease payments         1,868
               Less amount representing interest      201
                                                  $ 1,667

        (b)Principal  repayments on long-term debt at  March  31,
        1995 are as follows:
                                                  (000's)
               1996                               $ 1,143
               1997                                 4,778
               1998                                   657
               1999                                   433
               2000                                   455
               Thereafter                           1,729
                                                  $ 9,195
4.   Capital stock:

        (a)   Common shares:

          The  authorized capital of the Company consists  of  an
        unlimited  number  of common shares  without  par  value,
        205,000  Class  A  preference  shares  of  no  par  value
        (issued nil) and 27,000 Class B preference shares  of  no
        par value (issued nil).


<TABLE>
<CAPTION>
                                               (Dollar amounts in thousands)
                                                              
                                             Common Shares         Contributed
                                                                     Surplus
<S>                                          <C>                   <C>
Number of shares issued, and to be issued                                         
April  1,  1992,  net of 82,798  treasury                                         
shares                                             11,089,843                    -
                                                                                  
Balance, April 1, 1992                               $  7,557             $  2,050
                                                                                  
Issuance of 181,844 shares for cash                       358                    -
Adjustment of 79,066 shares to be  issued                                         
in exchange for 49.9% interest in EOS                       -                    -
                                                                                  
Balance, March 31, 1993                                 7,915                2,050
                                                                                  
Issuance of 107,866 shares for cash                       205                    -
Repurchased 251,100 shares for cash                     (151)                    -
Balance, March 31, 1994                                 7,969                2,050
                                                                                  
Issuance of 94,343 shares for cash                        185                    -
Repurchased 158,600 shares for cash                     (102)                    -
Balance, March 31, 1995                                 8,052                2,050
                                                                                  
Issuance   of  29,785  shares  for   cash                                         
(unaudited)                                                55                    -
                                                                                  
Balance, June 30, 1995 (unaudited)                   $  8,107              $ 2,050
                                                                                  
                                                                                  
Number of shares issued, and to be issued                                         
June 30, 1995 (unaudited)                          11,173,047                    -


</TABLE>

        (b)   Share option plans:

          Under  four  share  option plans, employees are  entitled  to  acquire
        common  shares  in quantities and prices as determined by the  directors
        of  the Company. The number of common shares available for allocation is
        as follows:
<TABLE>
<CAPTION>
                                        June 30,              March 31,
                                          1995          1995          1994
                                        (Unaudited)                            
<S>                                    <C>             <C>            <C>
Reserved at beginning of the period         868,477      935,717        869,806
Exercised during the period                (29,785)     (33,605)       (86,586)
Options allocated during the period         246,000            -        254,000
Options expired during the period           (7,135)     (33,635)      (101,503)
Remainder   reserved   for    future      1,077,557      868,477        935,717
        periods
</TABLE>

4.   Capital stock, continued:

          Under  the  plans, any share options  granted  must  be
        exercised  and  purchased  within  nine  years  of  being
        granted.   The  remaining  1,077,557  shares  have   been
        allocated for issue at prices ranging from $.90 to  $4.40
        per common share.

        (c)   Shares to be issued:

          The  common  shares to be issued are consideration  for
        the  1992  acquisition of the remaining  10.4%  of  Earth
        Observation  Sciences Limited (EOS).  At June  30,  1995,
        the  shareholders of EOS have an option,  exercisable  at
        any  time  to exchange their interest in EOS  for  79,214
        shares of the Company.  In addition, the Company has  the
        right to require the exchange of these EOS shares.   This
        right  may be exercised at any time, but will take  place
        no   later  than  October  31,  2001.   As  the  purchase
        consideration  is fixed, and the purchase will  occur  no
        later  than  October 31, 2001, the transaction  has  been
        treated  for  accounting purposes as  an  acquisition  of
        100% of the outstanding shares of EOS.


5.   Net earnings per common share:

     Basic earnings per common share is computed by dividing  net
     earnings  by  the weighted average number of  common  shares
     outstanding during the year.  Weighted average common shares
     are as follows:

        June 30, 1995 (unaudited)           11,148,378
        June 30, 1994 (unaudited)           11,158,572

        March 31, 1995                      11,142,811
        March 31, 1994                      11,315,231
        March 31, 1993                      11,292,881

6.   Income taxes:

        (a)    The  income  tax  provision is  comprised  of  the
        following:

<TABLE>
<CAPTION>
                                Three months           Year ended,
                               ended June 30             March 31,
                               1995      1994     1995     1994     1993
                                (Unauditied)                       
                                      
                             (000's)   (000's)  (000's)  (000's)   (000's)
<S>                         <C>       <C>      <C>      <C>       <C>

Current income tax expense   $  800    $  797   $ 3,983  $ 2,840   $ 2,022
Deferred income tax expense     (7)      (19)     (481)    (283)       155
                             $  793    $  778   $ 3,502  $ 2,557   $ 2,177

</TABLE>

6.   Income taxes, continued:

       (b)    Investment tax credits:

       At  March 31, 1995, the Company had unused investment  tax
       credits expiring March 31:

                                            (000's)

               1996                         $ 1,271
               1997                           1,895
               1998                             286
               1999                             865
               2000                             761
               2001                             975
               2002                           2,348
               2003                           2,000
               2004                           2,430
               2005                           2,500
                                            $15,331


       (c)     A  reconciliation  of income  taxes  at  statutory
       rates to actual income taxes is:
<TABLE>
<CAPTION>

                             Three months ended          Year ended
                                  June 30,               March 31,
                              1995       1994      1995     1994    1993
                                 Unaudited)                               
<S>                          <C>          <C>      <C>      <C>     <C>                                      
Combined basic income tax       45.3%      45.3%    45.3%    44.8%   44.5%
rate
                               (000's)    (000's)   (000's) (000's)  (000's)
                                                                   
Income tax expense prior to    $  816     $  801  $ 3,383  $ 2,605  $ 2,201
the following increases                                              
(reductions)
                                                                          
Non-deductible expenditures        18         20       92       50      79
Reduction of deferred tax                                                 
credits at rates in excess                                                
of the current period rate        (1)        (1)      (3)     (19)      (3)
Differing statutory rates                                                 
in foreign jurisdictions           25         33      130       70      10
Net foreign losses not tax                                                
effected                           45         67      466      294     152
Manufacturing and                                                         
processing rate reduction       (107)      (138)    (553)    (338)    (137)
Other                             (3)        (4)     (13)    (105)    (125)     
                                                                     
                               $  793      $ 778  $ 3,502  $ 2,557  $2,177
</TABLE>

7.   Supplementary information to the consolidated statements  of
     earnings:

        (a)     Research  and  development  expenses  have   been
        reduced by government assistance as follows:
<TABLE>
<CAPTION>

                             Three months             Year ended
                             ended June 30,            March 31,
                            1995       1994     1995     1994     1993
                              (Unaudited)                           
                           (000's)   (000's)  (000's)  (000's)   (000's)
<S>                        <C>       <C>      <C>      <C>       <C>
Research and development    $ 1,136   $ 1,128  $ 4,747  $4,319   $ 6,701
        expenses                                                  
Government assistance         (698)     (472)  (2,366)    (898)   (2,323)
                                                                         
                            $   438   $   656  $ 2,381  $ 3,421   $ 4,378
</TABLE>

               The above expenditures represent internally funded
        research  and development.  In addition, during the  year
        ended  March  31, 1995, the Company incurred  $29,320,000
        (1994  - $29,281,000 1993 - $26,507,000) of research  and
        development  which  was performed  as  part  of  customer
        contracts.  Customer contractual research and development
        expenditures have been included in cost of sales.

        (b)    Investment  tax credits earned in the  year  ended
        March  31, 1995 on scientific research expenditures  have
        been  applied  to reduce the cost of sales by  $1,850,000
        (1994 - $1,150,000 1993 - $1,050,000).


8.   Contingencies and commitments:

        (a)    At March 31, 1995, the Company was committed under
        operating   leases  for  the  following  minimum   annual
        rentals:

                                                (000's)

               1996                            $ 2,926
               1997                              3,134
               1998                              3,155
               1999                              3,159
               2000                              2,931
               Subsequent years                 12,440
                                               $27,745

        (b)The   Company's   bankers  have  issued   letters   of
        guarantee  to  certain customers of the  Company  in  the
        amount  of  $9,459,000  (1994  -  $15,378,000)  of  which
        $2,438,000   (1994  - $6,791,000) is  guaranteed  by  the
        Federal  Government of Canada.  If the Company failed  to
        perform  as  agreed  with  these  customers  and  if  the
        letters  of guarantee were called, the $7,021,000   (1994
        -  $8,587,000) due the Company's bankers would be secured
        by  the  existing general assignment of  book  debts  and
        assignment  of  inventories.   Inventories  relating   to
        contracts  with  the  Government of Canada  are  excluded
        from  the  assignment.  The Federal Government of  Canada
        is  secured under a general recourse agreement, which  is
        secondary to the Company's bankers.
8.   Contingencies and commitments, continued:

        (c)Certain  government assistance may be repayable  based
        on  future sales levels related to the  projects  funded.
        At  March  31, 1995 this amount approximated  $12,109,000
        (1994  -  $10,716,000).  Amounts, if  any,  that  may  be
        repayable would be accounted for in the period  in  which
        conditions that cause repayment arise.

        (d)In  April  1995, the Company signed  a  memorandum  of
        agreement  to  acquire 300,000 Series B Preferred  Shares
        of  EarthWatch,  Incorporated for cash  consideration  of
        U.S.   $3,000,000,   payable  by  six   equal   quarterly
        installments.  Payments  are to  commence  once  a  stock
        purchase  agreement  between the  parties  is  finalized.
        Each Preferred Share may be converted at any time into  a
        fully-paid Common Share of EarthWatch, Incorporated on  a
        one-for-one  basis.  The Company is  accounting  for  the
        investment on the cost basis.

          EarthWatch,  Incorporated is developing high-resolution
        commercial   imaging  satellites.  The  first   satellite
        launch is scheduled for 1996.

9.   Segmented information:

     The  Company's  principal business activity relates  to  the
     design,   development  and  integration  of   computer-based
     systems.   Sales to customers in foreign countries  amounted
     to:

                                              (000's)

        Three months ended:
                June 30, 1995 (unaudited)     $ 10,362
                June 30, 1994 (unaudited)       12,158

        Year ended:   March 31, 1995            48,331
                      March 31, 1994            37,135
                      March 31, 1993            40,366


10.  Acquisition:

     On   April  6,  1994,  the  Company  acquired  100%  of  the
     outstanding  shares  of  The PSC Communications  Group  Inc.
     (PSC), for cash consideration of $5,176,000 and a maximum of
     250,000  common shares of the Company.  The issue of  shares
     is  contingent upon PSC achieving certain income  levels  in
     the year ending March 31, 1996.

     The  total  net  assets acquired, accounted  for  using  the
     purchase method are as follows:

                                                (000's)
        Net non-cash assets acquired,
           at assigned values:
          Working capital                      $   215
          Fixed assets                             188
          Net non-cash assets acquired             403
        Excess of cost of net assets
            over assigned values (goodwill)      5,924
                                                 6,327

          Bank indebtedness of
               acquired operations              (1,151)
        Total cash consideration               $ 5,176


11.  Reconciliation of Accounting Principles

     The Company historically reports its financial results using
     generally  accepted accounting principles in Canada  ("GAAP-
     C").  The  major  differences between GAAP-C  and  generally
     accepted accounting principles in the United States  ("GAAP-
     US"), as applied to the Company, are as follows:


                                     Year ended March 31,
                                  1995      1994       1993
                                (000's)    (000's)    (000's)
                                                         
     Net Income, as reported     $  3,965  $  3,257    $  2,769
     GAAP-US adjustments            (869)   (1,657)      (1,088)
                                            
     Net Income, as adjusted     $  3,096  $  1,600    $  1,681

        (a)     The   Company  has  an  approximate  25%   equity
        investment  in  RSI that is accounted  for  under  GAAP-C
        using  the  equity method of accounting for  investments.
        RSI  is in its development stage and, pursuant to GAAP-C,
        MDA   is   capitalizing  its  share  of  RSI's   start-up
        operating  expenses  until  the  commencement  of   RSI's
        intended    operations.   Accordingly,   the    Company's
        historical  statements of operations do not report  as  a
        current  expense  the Company's share of  RSI's  start-up
        expenses.   GAAP-US  would  require  RSI  to  charge   to
        earnings  all  such  operating expenses  incurred  during
        RSI's development stage.

               In converting to GAAP-US, the Company's method  of
        accounting   for  costs  incurred  by  RSI   during   the
        development  stage  would be adjusted,  resulting  in  an
        increase to research and development expenses of  $66,000
        and  $221,000  for  the years ended March  31,  1994  and
        1993,  respectively. No adjustment was required  for  the
        year ended March 31, 1995.

        (b)    The  Company  has historically  received  Canadian
        Government   assistance   for   certain   research    and
        development  projects  that may  be  repayable  based  on
        future sales levels or other benefits achieved by MDA  as
        a  result  of  the  projects.  In  the  event  that  such
        projects  do  not result in future benefits to  MDA,  the
        repayment  obligation is relieved.  Pursuant  to  GAAP-C,
        the   Company's  historical  financial  statements   have
        recorded the receipt of such government assistance  as  a
        current  period  reduction  in research  and  development
        expenses,  disclosing  a  contingent  liability  for  the
        potential  repayment  obligation. GAAP-US  would  require
        postponing  the  recognition of a gain contingency  until
        the contingency is resolved.

               In converting to GAAP-US, the Company's method  of
        accounting  for  such  government  assistance  would   be
        adjusted  by  recording a liability  for  the  government
        assistance  received  (as  opposed  to  a  reduction   in
        current period research and development expenses) in  the
        amounts  (on  a pre-tax basis) of $1,598,000,  $2,839,000
        and  $1,549,000 for the years ended March 31, 1995,  1994
        and   1993,   respectively,  reflecting   the   repayment
        obligation.

        (c)    The  Company has historically received  investment
        tax   credits  for  Canadian  tax  purposes  for  certain
        qualifying  research and development  projects.  Pursuant
        to  GAAP-C, the Company's historical financial statements
        have recorded the receipt of investment tax credits as  a
        current period reduction in costs of sales.

               In converting to GAAP-US, the Company's method  of
        accounting  for investment tax credits would be  adjusted
        by  recording the credit as a reduction in current period
        income  tax expense (as opposed to a reduction in current
        period  costs  of  sales) of $1,850,000,  $1,150,000  and
        $1,050,000 for the years ended March 31, 1995,  1994  and
        1993, respectively.



                  ORBITAL SCIENCES CORPORATION
                 Pro Forma Financial Information

All  references to dollars in the following Pro Forma  Statements
and  the  related  notes  thereto are  to  U.S.  dollars,  unless
otherwise noted.

On  August  31, 1995, Orbital signed an agreement to acquire  MDA
(the "MDA Acquisition").  MDA's Common Shares are publicly traded
on  the  Vancouver Stock Exchange and The Toronto Stock Exchange.
The  MDA Acquisition is expected to be concluded by December  31,
1995.

Pursuant  to  the  terms of the agreement, a  newly  established,
wholly   owned   Canadian  subsidiary  of  Orbital   will   issue
Exchangeable   Shares  in  exchange  for  all  the   issued   and
outstanding  MDA Common Shares.  These Exchangeable  Shares  will
have voting and economic rights with respect to Orbital identical
to  Orbital  Common Stock, and will be exchangeable into  Orbital
Common  Stock  at the option of the holders, subject  to  certain
regulatory restrictions.  For purposes of the following pro forma
presentation,  Orbital  has  assumed  that  conversion   of   the
Exchangeable  Shares  occurred  contemporaneously  with   closing
(i.e.,  that Orbital issued Common Stock directly for MDA  Common
Shares).

The  actual  number  of shares of Orbital Common  Stock  issuable
pursuant  to the agreement is based on the average closing  sales
price of Orbital's Common Stock for the 20 trading days ending on
the date four trading days prior to closing.  Assuming an average
closing sales price of $17.25 per share for Orbital Common  Stock
and  an  exchange ratio of .31 Orbital Common Stock to  1.00  MDA
Common  Share, Orbital expects to issue approximately 3.9 million
shares  of  its  Common  Stock  for  all  of  MDA's  issued   and
outstanding voting common shares and employee share options.   As
part  of  the MDA Acquisition, Orbital will assume all  of  MDA's
outstanding common share options, which vest in variable  amounts
over  the  next four years. The MDA Acquisition will be accounted
for  using  the  pooling of interests method of  accounting  and,
accordingly, MDA's assets and liabilities will be carried forward
at their historical recorded amounts.

The   following  unaudited  condensed  consolidated   pro   forma
financial  information consists of Unaudited Pro Forma  Condensed
Consolidated  Statements of Operations for the six  months  ended
June 30, 1995 and for the year ended December 31, 1994, 1993  and
1992,  and the Unaudited Pro Forma Condensed Consolidated Balance
Sheet   as  of  June  30,  1995  (collectively,  the  "Pro  Forma
Statements").   The  Unaudited Pro Forma  Condensed  Consolidated
Statement  of Operations for the six months ended June  30,  1995
gives  effect  to  the MDA Acquisition as if it had  occurred  on
January  1, 1995.  The Unaudited Pro Forma Condensed Consolidated
Statements of Operations for the years ended December  31,  1994,
1993  and  1992 give effect to the MDA Acquisition as if  it  had
occurred  on January 1, 1992.  The Unaudited Pro Forma  Condensed
Consolidated Balance Sheet gives effect to the MDA Acquisition as
if it had occurred on June 30, 1995.


                  ORBITAL SCIENCES CORPORATION
                 Pro Forma Financial Information

Management believes that, on the basis set forth herein, the  Pro
Forma  Statements  reflect  a  reasonable  estimate  of  the  MDA
Acquisition  based on currently available information.   The  pro
forma  financial  data  do  not purport  to  represent  what  the
Company's  financial  position or  results  of  operations  would
actually  have been had the MDA Acquisition in fact  occurred  on
June  30, 1995, January 1, 1995 or January 1, 1992, or to project
the Company's financial position or results of operations for any
future date or period indicated.  The Pro Forma Statements should
be read in conjunction with the consolidated financial statements
of each of the Company and MDA and related notes thereto.

<TABLE>
<CAPTION>
                                                     ORBITAL SCIENCES      
                                                       CORPORATION
                                                   UNAUDITED PRO FORMA     
                                                  CONDENSED CONSOLIDATED
                                                      BALANCE SHEET
                                                      JUNE 30, 1995        
                                                       (thousands)

                             Historical     Historical      Conversion            Converted        Pro Forma      Pro Forma 
                              Orbital        MacDonald     Adjustments           Historical       Adjustments      Results
                              Sciences       Dettwiler      (B) Debit             MacDonald                         (US$)
                            Corporation         and          (Credit)           Dettwiler and
                               (US$)        Associates                         Associates Ltd.
                                             Ltd. (C)                             (C) (US$)
                                               (C$)
<S>                        <S>            <C>             <C>                  <C>                 <C>           <C>
ASSETS                                                                                                                      
                                                                                                                            
CURRENT ASSETS:                                                                                                             
                                                                                                                            
 Cash and cash equivalents   $   18,377    $    16,845     $   (4,571)     1    $      12,274                    $   30,651 

 Short-term investments          21,440               -              -                      -                        21,440

 Receivables, net                83,376          22,518        (6,110)     1           16,408                        99,784

 Inventories, net                28,320             817          (222)     1              595                        28,915

 Other current assets             8,145           1,468          (399)     1            1,069                         9,214

   Total current assets         159,658          41,648                                30,346                       190,004
                                                                                                                            
PROPERTY, PLANT AND             101,882          10,597        (2,875)     1            7,722                       109,604 
  EQUIPMENT, net
                                                                                                                            
INVESTMENTS IN AFFILIATES,       64,093             586          (586)  2(a)                -                        64,093 
  net
                                                                                                                            
EXCESS OF PURCHASE PRICE         67,464           7,865        (2,134)     1            5,731                        73,195 
 OVER NET ASSETS ACQUIRED,
 net
                                                                                                                            
 DEPOSITS AND OTHER ASSETS       15,737           1,362             19  2(b)            1,006                        16,743 
                                                                                                                            
                                                                                                                            
     TOTAL ASSETS            $  408,834    $     62,058                         $      44,805                    $  453,639 
                                                                                                                            
</TABLE>
<TABLE>
<CAPTION>
                                                                                                                            
                                                                                                                            
                                                     ORBITAL SCIENCES                                               
                                                       CORPORATION
                                                   UNAUDITED PRO FORMA                                              
                                                  CONDENSED CONSOLIDATED
                                                      BALANCE SHEET
                                                      JUNE 30, 1995                                                 
                                                       (thousands)

                             Historical     Historical      Conversion            Converted        Pro Forma      Pro Forma 
                              Orbital        MacDonald,    Adjustments           Historical       Adjustments      Results
                              Sciences       Dettwiler      (B) Debit             MacDonald,                        (US$)
                            Corporation         and          (Credit)           Dettwiler and
                               (US$)        Associates                         Associates Ltd.
                                             Ltd. (C)                             (C) (US$)
                                               (C$)
<S>                        <C>           <C>             <C>                <C>                  <C>            <C>
                                                                                                                               
LIABILITIES AND
STOCKHOLDERS' EQUITY
                                                                                                                            
CURRENT LIABILITIES:                                                                                                        
                                                                                                                            
Short-term borrowings and    $  11,752     $     1,224   $       332     1  $            892                 $       12,644
current portion of long-
term obligations
 
  Accounts payable and           43,463          11,803          3,203     1            8,600                        52,063 
    accrued expenses

Deferred revenue and other       11,557          19,813          5,377     1           14,436                        25,993 
    liabilities

Total current liabilities        66,772          32,840                                23,928                        90,700 
                                                                                                                            
LONG-TERM OBLIGATIONS,           95,203           8,197       (13,382)  2(b)           15,724                       110,927 
net of current portion                                           5,855     1                                                
                                                                                                                            
DEFERRED INCOME TAXES                                                                                                       
AND OTHER LIABILITIES            11,245               -                                     -                        11,245 
                                                                                                                            
TOTAL LIABILITIES               173,220          41,037                                39,652                       212,872 
                                                                                                                            
STOCKHOLDERS' EQUITY                                                                                                        
Preferred Stock                       -               -                                     -                             - 
Common Stock                        227           8,107          1,117     1            6,990         (6,990) A         266 
                                                                                                           39 A              
  Cumulative Translation              -             315          3,886     1          (3,571)                       (3,571) 
   Adjustment (1)

Other equity accounts           235,387          12,599            586  2(a)            1,734         (1,734) A     244,072 
                                                                  (19)  2(b)                            8,685 A              

 TOTAL STOCKHOLDERS EQUITY      235,614          21,021                                 5,153                       240,767
                                                                                                                            
                                                                                                                            
TOTAL LIABILITIES AND        $   408,834   $     62,058                         $      44,805                    $  453,639 
STOCKHOLDERS' EQUITY
                                                                                                                            
</TABLE>

<TABLE>                                                                                                                            
<CAPTION>                                                                       
                                                     ORBITAL SCIENCES                                               
                                                       CORPORATION
                                                   UNAUDITED PRO FORMA                                              
                                                  CONDENSED CONSOLIDATED
                                                 STATEMENT OF OPERATIONS
                                                SIX MONTHS ENDED JUNE 30,                                           
                                                           1995
                                             (in thousands, except share data)

                             Historical     Historical      Conversion            Converted        Pro Forma      Pro Forma 
                              Orbital        MacDonald,    Adjustments           Historical       Adjustments      Results
                              Sciences       Dettwiler      (B) Debit             MacDonald,                        (US$)
                            Corporation         and          (Credit)           Dettwiler and
                               (US$)        Associates                         Associates Ltd.
                                             Ltd. (C)                             (C) (US$)
                                               (C$)
<S>                        <C>             <C>             <C>                <C>                 <C>            <C>
Revenues                     $   132,930   $      52,503   $    14,692     1    $      37,811                    $  170,741 
                                                                                                                            
Costs of Goods Sold              97,293          34,519          1,234  2(c)           25,750                       123,043 
                                                                                                                            
                                                                                                                            
Gross Profit                     35,637          17,984                                12,061                        47,698 
                                                                                                                            
  Research and Development        8,764           1,747            442  2(b)            1,570                        10,334 
      Expenses

  Selling, General &             22,707          11,099        (3,097)     1            8,002                        30,709 
   Administrative Expenses
                                                                                                                            
 Amortization of Excess of        1,400             219           (61)     1              158                         1,558 
   Purchase Price Over Net
   Assets Acquired
                                                                                                                            
                                                                                                                            
Income (Loss) from Operations     2,766           4,919                                 2,331                         5,097 
                                                                                                                            
Net Interest Income             (1,887)             249             69     1              180                       (1,707) 
(Expense)
                                                                                                                            
Equity in Earnings of               362               -                                     -                           362 
Affiliate
                                                                                                                            
 Income Before Provision          1,241           5,168                                 2,511                         3,752 
  for Income Taxes
                                                                                                                            
Provision for Income Taxes            -           2,491          (220)  2(b)              745                           745 
                                                                                                                            
Net Income (F)               $     1,241   $       2,677                        $        1,766                         3,007 
                                                                                                                            
Net Income per Common and    $      0.06                                                                         $      0.12 D
Common Equivalent Share:
                                                                                                                            
                                                                                                                            
  Shares Used in Computing    20,954,359                                                             3,920,290 A   24,874,649 D
 Net Income per Common and
   Common Equivalent Share
                                                                                                                            
Net Income per Common                                                                                          
Share Assuming
Full Dilution:               $        0.06                                                                        $       0.12 D
                                                                                                                            
Shares Used in Computing      24,863,449                                                             3,920,290 A   28,783,739 D
Net Income per Common
Share, Assuming Full
  Dilution
                                                                                                                            
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
                                                                                                                            
                                                     ORBITAL SCIENCES                                               
                                                       CORPORATION
                                                   UNAUDITED PRO FORMA                                              
                                                  CONDENSED CONSOLIDATED
                                                 STATEMENT OF OPERATIONS
                                                   TWELVE MONTHS ENDED                                              
                                                    DECEMBER 31, 1994
                                                 (thousands, except share data)                                          


                             Historical     Historical      Conversion            Converted        Pro Forma      Pro Forma
                              Orbital        MacDonald,    Adjustments           Historical       Adjustments      Results
                              Sciences       Dettwiler      (B) Debit             MacDonald,                        (US$)
                            Corporation         and          (Credit)           Dettwiler and
                               (US$)        Associates                         Associates Ltd.
                                             Ltd. (C)                             (C) (US$)
                                               (C$)
<S>                        <C>            <C>              <C>                 <C>                <C>           <C>
Revenues                     $   221,946   $     109,955   $    30,325     1    $      79,630                    $  301,576 
                                                                                                                            
Costs of Goods Sold             157,066          80,063          1,850  2(c)           59,351                       216,417 
                                                               (22,562)    1                                                
                                                                                                                            
Gross Profit                     64,880          29,892                                20,279                        85,159 
                                                                                                                            
  Research and Development       14,389           2,381          1,598  2(b)            2,870                        17,259 
   Expenses
                                                               (1,109)     1                                                
   Selling, General &            39,749          19,859        (5,478)     1           14,381                        54,130 
   Administrative Expenses
                                                                                                                            
 Amortization of Excess of        2,045             435          (120)     1              315                         2,360 
   Purchase Price Over Net
   Assets Acquired
                                                                                                                            
                                                                                                                            
Income from Operations            8,697           7,217                                 2,713                        11,410 
                                                                                                                            
Net Interest Income                  37             250             69     1              181                           218 
(Expense)
                                                                                                                            
   Equity in Earnings           (1,264)               -                                     -                       (1,264) 
   (Losses) of Affiliate
                                                                                                                            
                                                                                                                            
Income Before Provision           7,470           7,467                                 2,894                        10,364 
   for Income Taxes
                                                                                                                            
Provision for Income Taxes        2,081           3,502          (729)  2(b)              663                         2,744 
                                                                                                                            
                                                                                                                            
Net Income                   $     5,389   $       3,965                        $        2,231                   $     7,620 
                                                                                                                            
Net Income per Common and    $      0.28                                                                         $      0.33 D
Common Equivalent Share:
                                                                                                                            
 Shares Used in Computing     19,104,427                                                             3,920,290 A   23,024,717 D
  Net Income per Common and
  Common Equivalent Share
                                                                                                                            
Net Income per Common        $      0.28                                                                                     
 Share, Assuming Full
 Dilution:
                                                                                                                            
 Shares Used in Computing     22,222,210                                                             3,920,290 A   27,142,500 D
  Net Income per Common
  Share, Assuming Full
  Dilution
                                                                                                                            
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
                                                                                                                            
                                                     ORBITAL SCIENCES                                               
                                                       CORPORATION
                                                   UNAUDITED PRO FORMA                                              
                                                  CONDENSED CONSOLIDATED
                                                 STATEMENT OF OPERATIONS
                                                   TWELVE MONTHS ENDED                                              
                                                    DECEMBER 31, 1993
                                               (thousands, except share data)                                          

                             Historical     Historical      Conversion            Converted        Pro Forma      Pro Forma
                              Orbital        MacDonald,    Adjustments           Historical       Adjustments      Results
                              Sciences       Dettwiler      (B) Debit             MacDonald,                        (US$)
                            Corporation         and          (Credit)           Dettwiler and
                               (US$)        Associates                         Associates Ltd.
                                             Ltd. (C)                             (C) (US$)              
                                               (C$)
<S>                         <C>           <C>             <C>                  <C>
Revenues                     $   223,087   $     101,417   $    24,320     1    $      77,097                    $  300,184 
                                                                                                                            
Costs of Goods Sold             170,204          75,294          1,150  2(c)           58,085                       228,289 
                                                               (18,359)     1                                                
                                                                                                                            
                                                                                                                            
Gross Profit                     52,883          26,123                                19,012                        71,895 
                                                                                                                            
  Research and Development       14,885           3,421             66  2(a)            4,818                        19,703 
   Expenses
                                                                 2,839  2(b)                                                
                                                               (1,508)     1                                                
   Selling, General &           25,897          16,769        (3,991)     1           12,778                        38,675 
   Administrative Expenses
                                                                                                                            
 Amortization of Excess of        1,537             127           (30)     1               97                         1,634 
  Purchase  Price Over Net
  Assets Acquired
                                                                                                                            
                                                                                                                            
Income from Operations           10,564           5,806                                 1,319                        11,883 
                                                                                                                            
Net Interest Income                 356               8              3     1                5                           361 
(Expense)
                                                                                                                            
  Equity in Earnings            (2,436)               -                                     -                       (2,436) 
   (Losses) of Affiliate
                                                                                                                            
                                                                                                                            
 Income Before Provision          8,484           5,814                                 1,324                         9,808 
  for Income Taxes
                                                                                                                            
Provision for Income Taxes        2,288           2,557        (1,248)  2(b)              115                         2,403 
                                                               (1,150)  2(c)                                                
                                                                  (44)     1                                                

Net Income (F)               $     6,196   $       3,257                        $        1,209                   $     7,405
                                                                                                                            
Net Income per Common and    $      0.43                                                                         $      0.40 D
Common Equivalent Share:
                                                                                                                            
 Shares Used in Computing     14,641,854                                                             3,920,290 A   18,562,144 D
 Net Income per Common and
  Common Equivalent Share
                                                                                                                            
Net Income per Common        $      0.38                                                                         $      0.37 D
Share, Assuming Full
Dilution:
                                                                                                                            
 Shares Used in Computing     18,256,276                                                             3,920,290 A   22,176,566 D
  Net Income per Common
  Share, Assuming Full
  Dilution
                                                                                                                            
</TABLE>
<PAGE>
<TABLE>
<CAPTION>
                                                     ORBITAL SCIENCES                                               
                                                       CORPORATION
                                                   UNAUDITED PRO FORMA                                              
                                                  CONDENSED CONSOLIDATED
                                                 STATEMENT OF OPERATIONS
                                                   TWELVE MONTHS ENDED                                              
                                                       DECEMBER 31, 1992
                                                 (thousands, except share data)                                           


                             Historical     Historical      Conversion            Converted        Pro Forma      Pro Forma 
                              Orbital        MacDonald,    Adjustments           Historical       Adjustments      Results
                              Sciences       Dettwiler      (B) Debit             MacDonald,                        (US$)
                            Corporation         and          (Credit)           Dettwiler and
                               (US$)        Associates                         Associates Ltd.
                                             Ltd. (C)                             (C) (US$)
                                               (C$)
<S>                        <C>            <C>             <C>                  <C>                <C>           <C>
Revenues                     $   204,190   $      85,156   $    16,175     1    $      68,981                    $  273,171 
                                                                                                                            
Costs of Goods Sold             158,661          59,705          1,050  2(c)           49,173                       207,834 
                                                              (11,582)     1                                                
                                                                                                                            
Gross Profit                     45,529          25,451                                19,808                        65,337 
                                                                                                                            
  Research and Development       10,586           4,378            221  2(a)            4,979                        15,565 
                  Expenses
                                                                 1,549  2(b)                                                
                                                               (1,169)     1                                                
   Selling, General &           28,615          16,137        (3,029)     1           13,108                        41,723 
   Administrative Expenses
                                                                                                                            
 Amortization of Excess of        1,495             136           (25)     1              111                         1,606 
  Purchase  Price Over Net
  Assets Acquired
                                                                                                                            
                                                                                                                            
Income (Loss) from                4,833           4,800                                 1,610                         6,443 
  Operations
                                                                                                                            
Net Interest Income                 738             146             24     1              122                           860 
  (Expense)
                                                                                                                            
Income (Loss) Before                                                                                                        
 Provision for Income             5,571           4,946                                 1,732                         7,303 
 Taxes
                                                                                                                            
 Provision (Benefit) for          1,630           2,177          (682)  2(b)              367                         1,997 
  Income Taxes
                                                               (1,050)  2(c)                                                
                                                                  (78)     1                                                
                                                                                                                            
Net Income                   $     3,941   $       2,769                        $        1,365                   $     5,306 
                                                                                                                            
Net Income per Common                                                                                                       
 and Common Equivalent       $      0.27                                                                         $      0.29 D
 Share:
                                                                                                                            
                                                                                                                            
 Shares Used in Computing     14,404,933                                                             3,920,290 A   18,325,223 D
 Net Incomeper Common and
 Common Equivalent Share
                                                                                                                            
                                                                                                                            
Net Income per Common        $      0.27                                                                         $     $0.29 D
Share,  Assuming Full
Dilution:
                                                                                                                            
                                                                                                                            
 Shares Used in Computing     14,404,933                                                             3,920,290 A   18,325,223 D
  Net Income per Common
  Share, Assuming Full
  Dilution
</TABLE>
<PAGE>

                   ORBITAL SCIENCES CORPORATION
               Notes to Pro Forma Adjustments to the
                   Unaudited Pro Forma Condensed
                 Consolidated Financial Statements
                        
(A)  On August 31, 1995, the Company signed an agreement  to
acquire  MDA.   The  MDA  Acquisition  is  expected  to   be
concluded  by  December 31, 1995.  The Pro Forma  Statements
assume  Orbital issues approximately 3.9 million  shares  of
its  Common  Stock for all of MDA's issued  and  outstanding
voting Common Shares and employee share options.  As part of
the  MDA  Acquisition,  Orbital will  assume  all  of  MDA's
outstanding  employee share options, which vest in  variable
amounts over the next four years.

The  MDA Acquisition will be accounted for using the pooling
of  interests  method  of accounting and,  accordingly,  the
issuance  of the Company's Common Stock was recorded  in  an
amount  equal  to MDA's historical net assets  at  June  30,
1995.

(B)   The  Pro  Forma  Statements convert  MDA's  historical
financial  statements  to  conform  to  generally   accepted
accounting standards in the United States and the provisions
of  Regulation S-X promulgated under the Securities Exchange
Act  of  1934.  Certain reclassifications have been made  to
the  historical MDA financial statements to conform  to  the
historical Orbital financial statement presentation.

(C)   The  Company  historically presented its  consolidated
financial   statements  on  a  calendar  year  basis.    MDA
historically presented its consolidated financial statements
on a fiscal year March 31 basis.

MDA's  historical consolidated financial statements included
in the pro forma condensed consolidated financial statements
for  the six months ended June 30, 1995 have been recast  to
include the three-month period ended March 31, 1995 and  the
three-month period ended June 30, 1995, to coincide with the
Company's calendar year basis of presentation.

The  pro  forma condensed consolidated financial  statements
for  the  calendar years ended December 31, 1994,  1993  and
1992  include MDA's historical financial statements for  its
fiscal  years  ended  March 31,  1995,  1994  and  1993  and
Orbital's  historical consolidated financial statements  for
its  calendar years ended December 31, 1994, 1993 and  1992.
The   effect  of  recasting  MDA's  historical  consolidated
financial statements as presented in the pro forma condensed
consolidated  financial statements for the six months  ended
June  30, 1995 has been charged to retained earnings  as  of
January 1, 1995 in the Pro Forma Financial Statements.   The
charge  to  retained  earnings  eliminates  the  effect   of
including  MDA's  results of operations for the  three-month
period  ending  March 31, 1995 of $1,050,000  (after  giving
effect  to  the  conversions and translations  described  in
these  notes)  in both the pro forma condensed  consolidated
statements of operations for the six months ending June  30,
1995  and  for  the year ending December  31,  1994.   MDA's
revenues  for  the three-month period ended March  31,  1995
were approximately $20,634,000.


                ORBITAL SCIENCES CORPORATION
            Notes to Pro Forma Adjustments to the
                Unaudited Pro Forma Condensed
              Consolidated Financial Statements

(D)  Pro forma income per common and common equivalent share
and pro forma income per common share assuming full dilution
are  both  calculated based on the aggregate of the weighted
average  number  of common and common equivalent  shares  of
both  Orbital and MDA, adjusted to equivalent shares of  the
combined company for all periods presented, assuming all MDA
outstanding stock options are outstanding and "in the money"
for  all  periods  presented.  Pro forma income  per  common
share assuming full dilution for the periods presented  also
includes  the  effects  of  an  assumed  conversion  of  the
Company's  convertible subordinated debentures (issued,  and
assumed  converted,  on  February 25,  1993),  after  giving
effect to all net income adjustments that would result  from
the assumed conversion.

   (E)  Approximately  $3,000,000  of  nonrecurring  charges
directly  attributable  to  the MDA  Acquisition,  including
legal,  accounting  and  investment banking  fees,  will  be
included  in Orbital's consolidated statement of  operations
in  the period the MDA Acquisition is consummated, currently
expected to be during the quarter ending December 31,  1995.
Such  charges were not considered in the Unaudited Pro Forma
Condensed Consolidated Statements of Operations.

(F)   The  Company adopted SFAS 121 as of January  1,  1995.
The  Company's adoption of SFAS 121 resulted in a cumulative
effect  adjustment of $4,160,000 which decreased net  income
for   the  six-month  period  ended  June  30,  1995.    The
cumulative  effect of the change in accounting principle  is
not   included  in  the  accompanying  Unaudited  Pro  Forma
Condensed Consolidated Statement of Operations for  the  six
months ended June 30, 1995.

The  Company  adopted SFAS 109 as of January 1,  1993.   The
Company's  adoption  of SFAS 109 resulted  in  a  cumulative
effect adjustment of $200,000 which increased net income for
the year ended December 31, 1993.  The cumulative effect  of
the  change in accounting principle is not included  in  the
accompanying  Unaudited  Pro  Forma  Condensed  Consolidated
Statement of Operations for the twelve months ended December
31, 1993.

                ORBITAL SCIENCES CORPORATION
           Notes to Conversion Adjustments to the
                Unaudited Pro Forma Condensed
              Consolidated Financial Statements

(1)   MDA  operates with, and has historically reported  its
financial  results  using,  the  Canadian  dollar   as   its
functional currency.  Orbital operates with, and reports its
financial results using, the U.S. dollar.  Accordingly,  the
Pro   Forma  Statements  report  the  consolidated  entity's
financial  results using the U.S. dollar as  its  functional
currency,  and  MDA's  historical  financial  results   have
accordingly  been  translated to the U.S. dollar  using  the
appropriate  exchange rates for the appropriate  periods  as
follows (Canadian dollars to U.S. dollars):

     Date or Period                     Exchange Rate
      at June 30, 1995                              1.37 to 1.00
      for  the six months ended June 30, 1995       1.38  to 1.00
      for  the year ended December 31, 1994         1.38  to 1.00
      for  the year ended December 31, 1993         1.31  to 1.00
      for  the year ended December 31, 1992         1.23  to 1.00

The  economic  effects  of an exchange  rate  change  on  an
operation  that is relatively self-contained and  integrated
within  a  foreign country relate to the net  investment  in
that  operation.   Translation adjustments that  arise  from
consolidating  that  foreign operation do  not  impact  cash
flows  and are not included in net income.  Since MDA  is  a
self-contained entity integrated within Canada, the  impacts
of   cumulative  translation  adjustments  that  arise  from
consolidating  MDA  with  Orbital have  been  excluded  from
determining  net  income  and  have  been  reported   within
stockholders' equity.

(2)   MDA  has  historically reported its financial  results
using  generally  accepted accounting principles  in  Canada
("GAAP-C").   Orbital  reports its financial  results  using
generally  accepted  accounting  principles  in  the  United
States  ("GAAP-US").   The Pro Forma Statements  report  the
consolidated  entity's  financial  results  using   GAAP-US.
Accordingly,  MDA's historical financial results  have  been
converted to GAAP-US.

The  major  differences between GAAP-C and  GAAP-US,  as  it
applies to MDA, are as follows:

(a)   MDA  has  an  approximate 25% equity investment  in  a
Canadian  company ("Investee") that is accounted  for  under
GAAP-C   using   the   equity  method  of   accounting   for
investments.   Investee  is in its  development  stage  and,
pursuant   to   GAAP-C,  MDA's  historical   statements   of
operations do not report as a current expense MDA's share of
Investee's start-up expenses.  GAAP-US would require MDA  to
charge  to  earnings  all such operating  expenses  incurred
during Investee's development stage.  In converting to GAAP-
US,  the  Pro  Forma  Statements  adjust  MDA's  method   of
accounting for costs

                ORBITAL SCIENCES CORPORATION
           Notes to Conversion Adjustments to the
                Unaudited Pro Forma Condensed
              Consolidated Financial Statements

incurred by Investee during the development stage, resulting
in  a  cumulative reduction in the carrying amount of  MDA's
investment.

(b)   MDA  has  historically  received  Canadian  Government
assistance  for  certain research and  development  projects
that  may be repayable based on future sales levels or other
benefits  achieved by MDA as a result of the  projects.   In
the  event  that  such  projects do  not  result  in  future
benefits  to  MDA,  the  repayment obligation  is  relieved.
Pursuant  to  GAAP-C, MDA's historical financial  statements
have recorded the receipt of such government assistance as a
current   period  reduction  in  research  and   development
expenses,   disclosing  a  contingent  liability   for   the
potential  repayment obligation.  In converting to  GAAP-US,
the  Pro  Forma Statements adjust MDA's method of accounting
for  such government assistance by recording a liability for
the   government  assistance  received  (as  opposed  to   a
reduction   in  current  period  research  and   development
expenses)  reflecting the repayment obligation.  The  amount
of  government assistance will be recorded as an  adjustment
to  research  and  development expenses in  the  period  the
contingency is resolved.

(c)   MDA  has historically received investment tax  credits
for  Canadian  tax purposes for certain qualifying  research
and   development  projects.   Pursuant  to  GAAP-C,   MDA's
historical financial statements have recorded the receipt of
investment  tax  credits as a current  period  reduction  in
costs  of  sales.  In converting to GAAP-US, the  Pro  Forma
Statements  adjust MDA's method of accounting for investment
tax  credits  by  recording the credit  as  a  reduction  in
current period income tax expense (as opposed to a reduction
in current period costs of sales).






     Pursuant to the requirements of the Securities Exchange
Act  of 1934, the registrant has duly caused this report  to
be  signed  on its behalf by the undersigned thereunto  duly
authorized.


                              ORBITAL SCIENCES CORPORATION


DATED:  November __, 1995      By   /s/ David W. Thompson

                                    David   W.   Thompson,
                                    President and   Chief   Executive
                                    Officer





                                                                 












                   COMBINATION AGREEMENT

                dated as of August 31, 1995

                           among

               ORBITAL SCIENCES CORPORATION,

                    3173623 CANADA INC.

                            and

          MACDONALD, DETTWILER AND ASSOCIATES LTD.




















<PAGE>



ARTICLE 1  DEFINITIONS                                             1
          1.1.  CROSS REFERENCE TABLE OF CERTAIN DEFINED TERMS     1
          1.2.  DEFINITIONS OF CERTAIN ADDITIONAL TERMS            3
                 1.2.1.  CODE                                      3
                 1.2.2.  CONSOLIDATED TAX                          3
                 1.2.3.  EFFECTIVE DATE                            3
                 1.2.4.  EXCHANGE ACT                              3
                 1.2.5.  MDA MATERIAL ADVERSE EFFECT               3
                 1.2.6.  ORBITAL MATERIAL ADVERSE EFFECT           3
                 1.2.7.  RETURN                                    3
                 1.2.8.  SECURITIES ACT                            3
                 1.2.9.  SEC                                       3
                 1.2.10.  SUBSIDIARY                               3
                 1.2.11.  TAX                                      4

ARTICLE 2  GENERAL                                                 4
          2.1.  PLAN OF ARRANGEMENT                                4
          2.2.  VOTING AND EXCHANGE TRUST AGREEMENT                5
          2.3.  SUPPORT AGREEMENT                                  6
          2.4.  CLOSING, CLOSING DATE AND EFFECTIVE TIME           6
          2.5.  HOLDING COMPANY AGREEMENTS.                        6
          2.6.  CONTEMPORANEOUS TRANSACTIONS                       6

ARTICLE 3  REPRESENTATIONS AND WARRANTIES OF MDA                   6
          3.1.  DUE ORGANIZATION, AUTHORIZATION AND GOOD STANDING
          OF MDA                                                   6
          3.2.  NO VIOLATION OR APPROVAL                           7
          3.3.  CAPITAL STOCK                                      7
          3.4.  SUBSIDIARIES                                       8
          3.5.  SECURITIES LAW FILINGS.                            8
          3.6.  FINANCIAL STATEMENTS, ETC.                         9
          3.7.  ABSENCE OF CHANGES; OPERATIONS IN THE ORDINARY
          COURSE                                                   9
          3.8.  TAXES                                             11
          3.9.  PROPERTIES                                        12
          3.10.  CUSTOMERS, DISTRIBUTORS AND SUPPLIERS            12
          3.11.  OPERATIONS IN CONFORMITY WITH LAW, ETC           13
          3.12.  LITIGATION                                       13
          3.13.  EMPLOYEE MATTERS; BENEFIT PLANS                  14
          3.14.  LABOR RELATIONS                                  15
          3.15.  GOVERNMENT CONTRACTS AND SUBCONTRACTS            15
          3.16.  LICENSES, ETC.                                   15
          3.17.  ENVIRONMENTAL MATTERS                            16
          3.18.  CONTRACTUAL OBLIGATIONS, ETC                     16
          3.19.  EARTHWATCH AGREEMENT.                            17
          3.20.  AFFILIATED TRANSACTIONS                          18
          3.21.  PATENTS, TRADEMARKS, ETC                         18
          3.22.  INSURANCE                                        18
          3.23.  CUSTOMER WARRANTY COVERAGE                       18
          3.24.  POOLING                                          18
          3.25.  CERTAIN AGREEMENTS                               18
          3.26.  OPINION OF FINANCIAL ADVISOR                     19
          3.27.  BROKERS, FINDERS, ETC                            19
          3.28.  DISCLOSURE; PROVISION OF INFORMATION             19

ARTICLE 4  REPRESENTATIONS AND WARRANTIES OF ORBITAL AND
               ACQUISITION                                        20
          4.1.  DUE ORGANIZATION, AUTHORIZATION AND GOOD STANDING
          OF ORBITAL AND ACQUISITION                              20
          4.2.  NO VIOLATION OR APPROVAL                          21
          4.3.  CAPITAL STOCK                                     21
          4.4.  SEC REPORTS                                       22
          4.5.  FINANCIAL STATEMENTS, ETC.                        22
          4.6.  ABSENCE OF CHANGES                                23
          4.7.  POOLING                                           23
          4.8.  OPERATIONS IN CONFORMITY WITH LAW, ETC.           23
          4.9.  LITIGATION                                        23
          4.10.  GOVERNMENT CONTRACTS AND SUBCONTRACTS            23
          4.11.  ENVIRONMENTAL MATTERS                            24
          4.12.  DISCLOSURE                                       24

ARTICLE 5  CERTAIN COVENANTS                                      25
          5.1.  PREPARATION OF PROXY STATEMENT AND NO ACTION
          REQUEST; OTHER FILINGS AND SUBMISSIONS                  25
          5.2.  SHAREHOLDERS' MEETING                             26
          5.3.  EXCLUSIVITY; ACQUISITION PROPOSALS                26
          5.4.  AMENDMENT TO PLAN OF ARRANGEMENT                  27
          5.5.  PUBLIC ANNOUNCEMENTS                              27
          5.6.  NOTIFICATION OF CERTAIN MATTERS                   27
          5.7.  OTHER LIMITATIONS ON CONDUCT OF BUSINESS PRIOR TO
          THE EFFECTIVE TIME                                      28
          5.8.  EXERCISE OF CALL RIGHT                            28
          5.9.  ACCESS TO INFORMATION                             28
          5.10.  POST EFFECTIVE DATE REPORTING                    28
          5.11.  NO ACTION REQUEST                                29
          5.12.  INDEMNIFICATION                                  29
          5.13.  TAX FILINGS.                                     30
          5.14.  FURTHER ASSURANCES                               30

ARTICLE 6  CONDITIONS PRECEDENT                                   31
          6.1.  CONDITIONS PRECEDENT TO MDA'S OBLIGATION TO
          EFFECT THE ARRANGEMENT                                  31
                 6.1.1.  REPRESENTATIONS; COVENANTS; CERTIFICATE  31
                 6.1.2.  OPINION OF COUNSEL FOR ORBITAL           31
                 6.1.3.  PRICE OF ORBITAL STOCK                   31
          6.2.  CONDITIONS PRECEDENT TO OBLIGATIONS OF ORBITAL    31
                 6.2.1.  REPRESENTATIONS; COVENANTS; CERTIFICATE  31
                 6.2.2.  OPINION OF COUNSEL FOR MDA               32
                 6.2.3.  MDA RIGHTS PLAN.                         32
                 6.2.4.  AFFILIATE AGREEMENTS                     32
                 6.2.5.  EMPLOYMENT AGREEMENTS                    32
                 6.2.6.  APPRAISAL RIGHTS                         32
                 6.2.7.  POOLING OF INTERESTS ACCOUNTING
                 TREATMENT                                        32
                 6.2.8.  REQUIRED CONSENTS                        32
                 6.2.9  PRICE OF ORBITAL STOCK                    33
          6.3.  CONDITIONS PRECEDENT TO THE OBLIGATIONS OF EACH
                PARTY                                             33
                 6.3.1.  SHAREHOLDER APPROVAL                     33
                 6.3.2.  GOVERNMENTAL AND COURT APPROVALS         33
                 6.3.3.  NO ACTION REQUEST/REGISTRATION STATEMENT 33
                 6.3.4.  INJUNCTIONS                              34
                 6.3.5.  NASDAQ/NMS LISTING APPROVAL              34

ARTICLE 7  MISCELLANEOUS                                          34
          7.1.  TERMINATION                                       34
          7.2.  AMENDMENTS AND SUPPLEMENTS                        35
          7.3.  SURVIVAL OF REPRESENTATIONS, WARRANTIES AND
                AGREEMENTS                                        36
          7.4   OTHER PAYMENTS                                    36
          7.5.  EXPENSES                                          36
          7.6.  GOVERNING LAW                                     36
          7.7.  NOTICE                                            36
          7.8A.  ENTIRE AGREEMENT, ASSIGNABILITY, ETC             38
          7.8.  COUNTERPARTS                                      39
          
          
          
                          EXHIBITS

EXHIBIT 2.1         FORM OF PLAN OF ARRANGEMENT

EXHIBIT 2.1.2       FORM OF HOLDING COMPANY AGREEMENT

EXHIBIT 2.2         FORM OF VOTING AND EXCHANGE TRUST AGREEMENT

EXHIBIT 2.3         FORM OF SUPPORT AGREEMENT

EXHIBIT 3.18        FORM OF EMPLOYMENT AGREEMENTS

EXHIBIT 6.2.4(A)    FORM OF AFFILIATES AGREEMENT -- GENERAL

EXHIBIT 6.2.4(B)    FORM OF AFFILIATES AGREEMENT -- SPAR
                    AEROSPACE LIMITED

EXHIBIT 6.2.5       FORM OF CHANGE OF CONTROL AGREEMENT

EXHIBIT 7.1(H)      FORM OF VOTING AGREEMENT AND IRREVOCABLE
                    PROXY
</PAGE>
                   COMBINATION AGREEMENT

     COMBINATION AGREEMENT (the "Agreement") dated as of August
31, 1995, among Orbital Sciences Corporation, a corporation
incorporated under the laws of the State of Delaware ("Orbital"),
3173623 Canada Inc., a corporation incorporated under the laws of
Canada and a wholly owned subsidiary of Orbital ("Acquisition"),
and MacDonald, Dettwiler and Associates Ltd., a corporation
incorporated under the laws of Canada ("MDA").

     WHEREAS, the respective Boards of Directors of Orbital,
Acquisition  and MDA have approved the transactions contemplated
by this Agreement and the Board of Directors of MDA has agreed to
submit the Plan of Arrangement (as defined in Section 2.1) and
the other transactions contemplated hereby to its shareholders
and holders of certain employee stock options for approval;

     WHEREAS, Orbital, Acquisition and MDA intend the
transactions described in the Plan of Arrangement to be treated
as a "pooling of interests" under generally accepted accounting
principles in the United States; and

     WHEREAS, it is the current intention of Orbital to operate
MDA as a separate division of Acquisition.

     NOW, THEREFORE, in consideration of the mutual covenants,
representations, warranties and agreements set forth herein, and
intending to be legally bound hereby, Orbital, Acquisition and
MDA hereby agree as follows:


                         ARTICLE 1
                        DEFINITIONS

     Certain terms are used in this Agreement as specifically
defined herein.

     1.1  Cross Reference Table of Certain Defined Terms.  The
following terms are defined in the Sections set forth below, and
shall have the respective meanings therein defined:

     Term                               Section

     "Acquisition"                      Preamble
     "Acquisition Transaction"          Section 5.3
     "Affiliate"                        Section 6.2.4
     "Affiliate Agreements"             Section 6.2.4
     "Agreement"                        Preamble
     "Arrangement"                      Section 2.1
     "Average Closing Price"            Section 2.1.2
     "CBCA"                             Section 2.1
     "Canadian GAAP"                    Section 3.6
     "Charter Documents"                Section 3.1
     "Class B Preferred Shares"         Section 2.1.4
     "Closing"                          Section 2.4
     "Closing Date"                     Section 2.4
     "Contract"                         Section 3.18
     "Contractual Obligations"          Section 3.18
     "Court"                            Section 2.1
     "EarthWatch Agreement"             Section 3.19
     "Effective Time"                   Section 2.4
     "Employment Agreements"            Section 3.18
     "EOS"                              Section 3.3
     "ERISA"                            Section 3.13
     "Exchange Ratio"                   Section 2.1.2
     "Exchangeable Shares"              Section 2.1.1
     "Final Order"                      Section 2.1
     "Financial Statements"             Section 3.5
     "Government Contract"              Section 3.16
     "Government Subcontract"           Section 3.16
     "Hazardous Substance"              Section 3.17
     "Holding Company Agreement"        Section 2.1.2
     "Intellectual Property Rights"     Section 3.21
     "Interim Order"                    Section 2.1
     "Lien"                             Section 3.4
     "MDA"                              Preamble
     "MDA Common Shares"                Section 2.1.2
     "MDA Disclosure Schedule"          Section 3.1
     "MDA Options"                      Section 2.1.3
     "MDA 1988 Options"                 Section 2.1
     "Multiemployer Plan"               Section 3.13
     "No Action Request"                Section 3.28
     "Orbital"                          Preamble
     "Orbital Common Shares"            Section 2.1.3
     "Orbital Disclosure Schedule"      Section 4.2
     "Orbital Financial Statements"     Section 4.5
     "PCBs"                             Section 3.17
     "PSC"                              Section 3.3
     "Plans"                            Section 3.13
     "Plan of Arrangement"              Section 2.1
     "Pooling of Interests"             Preamble
     "Proxy Circular"                   Section 3.28
     "Registration Statement"           Section 3.28
     "Replacement Options"              Section 2.1.3
     "Rights"                           Section 2.1.2
     "SEC Reports"                      Section 4.4
     "Securities Reports"               Section 3.5
     "Shareholder Meeting"              Section 5.2
     "Shareholders' Meeting Date"       Section 5.2
     "Support Agreement"                Section 2.3
     "Trustee"                          Section 2.2
     "US GAAP"                          Section 4.5
     "Voting Trust Agreement"           Section 2.2
     
     1.2.  Definitions of Certain Additional Terms.  The
following terms shall have the meanings set forth below:

          1.2.1.  "Code" means the United States Internal Revenue
     Code of 1986, as amended.

          1.2.2.  Consolidated Tax" means any Canadian and United
     States Federal income Tax and any provincial, state, local
     or foreign income or corporate franchise Tax imposed on any
     affiliated, combined or unitary group of corporations (or
     the common parent of any such group of corporations) that
     included or was required to include MDA for any taxable year
     ending on or before the Closing Date.

          1.2.3.  "Effective Date" shall mean the date on which
     the Effective Time occurs.

          1.2.4.  "Exchange Act" shall mean the United States
     Securities Exchange Act of 1934, as amended.

          1.2.5.  "MDA Material Adverse Effect" shall mean an
     effect that does or would reasonably be expected to have a
     material adverse effect on the financial condition or
     results of operations of MDA and its Subsidiaries, taken as
     a whole.

          1.2.6.  "Orbital Material Adverse Effect" shall mean an
     effect that does or would reasonably be expected to have a
     material adverse effect on the financial condition or
     results of operations of Orbital and its Subsidiaries, taken
     as a whole.

          1.2.7.  "Return" means any return, amended return,
     declaration, report, estimate, information return (e.g.
     United States Internal Revenue Service Form 1099 and 5500),
     closing agreement, or statement required or permitted to be
     filed under the laws of any jurisdiction in respect of any
     Tax.

          1.2.8.  "Securities Act" shall mean the United States
     Securities Act of 1933, as amended.

          1.2.9.  "SEC" shall mean the United States Securities
     and Exchange Commission.

          1.2.10.  "Subsidiary" shall mean, with respect to any
     corporation, any other corporation, association, or other
     business entity a majority (by number of votes) of the
     shares of capital stock (or other voting interests) of which
     is owned directly or indirectly by such corporation.

          1.2.11.  "Tax" means any Canadian or United States
     Federal, provincial, state or local tax or any foreign tax
     (including, without limitation, any net income, gross
     income, profits, premium, estimated, excise, sales, value
     added, services, use, occupancy, gross receipts, franchise,
     license, ad valorem, severance, capital levy, production,
     stamp, transfer, withholding, employment, unemployment,
     payroll or property tax, customs duty, or any other
     governmental charge or assessment), together with any
     interest, addition to tax, or penalty.


                         ARTICLE 2
                          GENERAL

     2.1.  Plan of Arrangement.  MDA agrees that it shall, as
soon as reasonably practical, apply to the Supreme Court of
British Columbia (the "Court") pursuant to Section 192 of the
Canada Business Corporations Act, as amended (the "CBCA") for an
interim order in form and substance reasonably satisfactory to
Orbital (the "Interim Order") providing for, among other things,
the calling and holding of a special meeting of  the shareholders
of MDA (voting together as one class) and the holders of options
to purchase MDA Common Shares pursuant to the MDA Key Employee
Stock Option Plan 1988 or the MDA Employee Stock Option Plan 1988
(collectively, the "MDA 1988 Options") (voting separately from
the shareholders of MDA as a second class) for the purpose of
considering and, if deemed advisable, approving a plan of
arrangement involving MDA and Acquisition substantially in the
form attached as Exhibit 2.1 (the "Arrangement" or "Plan of
Arrangement"), the principal terms of which include:

          2.1.1.  the designation and authorization of a class of
     preferred stock of Acquisition (the "Exchangeable Shares")
     that will have the rights, privileges and restrictions, and
     be subject to the conditions, set forth in Appendix A of the
     Plan of Arrangement;

          2.1.2.  an exchange of shares whereby (i) all
     outstanding common shares of MDA  ("MDA Common Shares"),
     other than MDA Common Shares held by holding companies
     referred to in clause (ii) of this subsection, together with
     all rights (the "Rights") associated with such MDA Common
     Shares under that certain Amended and Restated Shareholder
     Protection Rights Plan Agreement dated as of August 27, 1992
     as amended through the date hereof, between MDA and Montreal
     Trust Company of Canada, shall be exchanged for the number
     of Exchangeable Shares per MDA Common Share equal to the
     quotient (the "Exchange Ratio") of U.S.$5.41 divided by the
     average closing sales price of Orbital common stock, par
     value U.S.$ .01 per share (the "Orbital Common Shares"), for
     the twenty trading days ending on the date four trading days
     prior to the Effective Date, as reported on the Nasdaq
     National Market System (the "Average Closing Price"),
     provided, however, that in no event shall the Exchange Ratio
     be less than .2705 or greater than .3607; and (ii) all
     outstanding shares of each newly formed holding company with
     no assets other than MDA Common Shares (together with all
     Rights) and all of the shares of which are owned by a party
     who has entered into an agreement with Acquisition
     substantially in the form of Exhibit 2.1.2 hereto (a
     "Holding Company Agreement") pursuant to the provisions of
     Section 2.5 hereof and has performed such agreement to the
     satisfaction of Acquisition in its sole discretion, will be
     exchanged for a number of Exchangeable Shares equal to the
     product of  the Exchange Ratio multiplied by the number of
     MDA Common Shares owned by such holding company; in each
     case such Exchangeable Shares to be thereafter exchangeable
     for Orbital Common Shares on a one-for-one basis (subject to
     certain adjustments pursuant to the Plan of Arrangement), at
     the option of the holder, during the periods, at the times
     and subject to the conditions set forth in Article 2 of the
     Plan of Arrangement;

          2.1.3.  the conversion of each outstanding MDA employee
     stock option, including the MDA 1988 Options, (collectively
     the "MDA Options"), into an option (collectively, the
     "Replacement Options") to purchase a number of Orbital
     Common Shares determined by multiplying the number of MDA
     Common Shares subject to such MDA Option times the Exchange
     Ratio, each Replacement Option having an exercise price per
     share equal to the exercise price per share of such MDA
     Option immediately prior to the Effective Time divided by
     the Exchange Ratio, and having the same vesting, expiration
     and other terms as such MDA Option, all in accordance with
     the terms of the plan governing such MDA Option or the Plan
     of Arrangement; and

          2.1.4.  the issuance of 10,000 Class B Preferred Shares
     of Acquisition (the "Class B Preferred Shares") to Canadian
     Imperial Bank of Commerce as partial consideration for
     investment banking services rendered in connection with the
     Arrangement.

     The foregoing is only a summary of the Plan of Arrangement.
The terms, conditions and procedures for accomplishing the
exchange of shares are set forth in the Plan of Arrangement and
the Appendices thereto and the foregoing is qualified by
reference thereto.

     If approval of the Plan of Arrangement by the shareholders
of MDA and the holders of MDA 1988 Options is obtained, MDA shall
promptly take the necessary steps to submit the Arrangement to
the Court and apply for a final order of the Court approving such
Arrangement (the "Final Order").

     2.2.  Voting and Exchange Trust Agreement.  Prior to the
Closing, Orbital, Acquisition and The First National Bank of
Boston or a bank or trust company to be selected by Orbital and
approved by Acquisition and MDA as trustee (the "Trustee"), shall
execute and deliver a Voting and Exchange Trust Agreement in
substantially the form set forth as Exhibit 2.2 hereto, with such
changes and additions thereto as may be reasonably requested by
the Trustee (as so executed, the "Voting Trust Agreement").
Orbital shall deposit with the Trustee one share of a newly
created class of Orbital preferred stock having such voting
rights, privileges and preferences as may be required to secure
the voting rights relating to the Orbital Common Shares granted
for the benefit of the holders of the Exchangeable Shares, such
share to be held by the Trustee in accordance with the Voting
Trust Agreement.

     2.3.  Support Agreement.  Prior to the Closing, Orbital and
Acquisition shall execute and deliver the Support Agreement (the
"Support Agreement") in substantially the form set forth as
Exhibit 2.3.

     2.4.  Closing, Closing Date and Effective Time.  The
execution and delivery of the documents required to effectuate
the transactions contemplated by this Agreement (the "Closing")
shall take place at the offices of Farris, Vaughan, Wills &
Murphy, 700 West Georgia Street, Vancouver, British Columbia,
Canada or at such other place and at such time as the parties
hereto may agree; provided, however, such Closing shall take
place no later than the fifth business day after satisfaction or
waiver of the last to be fulfilled of the conditions set forth in
ARTICLE 6 that by their terms are not to occur at the Closing
(the "Closing Date").  The Arrangement shall become effective as
provided for in the Plan of Arrangement (the "Effective Time").

     2.5.  Holding Company Agreements.  The Proxy Circular shall
stipulate that those shareholders of MDA who wish to contribute
their MDA Common Shares (together with all Rights) to a holding
company and exchange the shares of such holding company for
Exchangeable Shares pursuant to clause (ii) of Section 2.1.2 must
notify MDA of their desire to do so not less than five business
days prior to the Shareholder Meeting and must have entered into
the Holding Company Agreement with Acquisition prior to the date
of the Shareholder Meeting.  Acquisition shall enter into a
Holding Company Agreement with each shareholder of MDA who
provides the aforementioned notification to MDA.  Any shareholder
of MDA who has not entered into a Holding Company Agreement with
Acquisition on or before the date of the Shareholder Meeting or
who has entered into such agreement but has failed to perform
such agreement to the satisfaction of Acquisition in its sole
discretion shall, subject to the Plan of Arrangement receiving
all necessary approvals, exchange his or her MDA Common Shares
and all Rights for Exchangeable Shares in accordance with clause
(i) of Section 2.1.2

     2.6.  Contemporaneous Transactions.  The parties hereby
agree that each of the transactions contemplated by this
Agreement that is in fact consummated shall, to the extent
permitted by applicable law and not otherwise provided for herein
or in the Plan of Arrangement, be deemed consummated
substantially contemporaneously with any other transaction that
is in fact consummated pursuant to this Agreement.


                         ARTICLE 3
           REPRESENTATIONS AND WARRANTIES OF MDA

     In order to induce Orbital and Acquisition to enter into
this Agreement, MDA hereby represents and warrants as follows:

     3.1.  Due Organization, Authorization and Good Standing of
MDA.  MDA is a corporation duly organized, validly existing and
in good standing under the CBCA and each Subsidiary of MDA is a
corporation duly organized, validly existing and in good standing
under the laws of the jurisdiction of its incorporation as listed
in Section 3.1 of the disclosure schedule prepared by MDA and
provided to Orbital concurrently with the execution of this
Agreement (the "MDA Disclosure Schedule").  MDA has the requisite
corporate power and authority to execute, deliver and perform its
obligations under this Agreement and, upon receipt of any
approvals required by the Interim Order and receipt of the Final
Order, to consummate all transactions contemplated hereby.  The
execution, delivery and performance by MDA of this Agreement, and
the consummation by MDA of the transactions contemplated hereby,
have been duly and validly authorized and approved by all
necessary corporate action in respect thereof on the part of MDA,
subject only to any approvals required by the Interim Order and
receipt of the Final Order.  This Agreement constitutes the valid
and binding obligation of MDA, enforceable in accordance with its
terms, subject to bankruptcy, insolvency, moratorium,
reorganization and similar laws of general applicability
affecting the rights and remedies of creditors and to general
principles of equity, regardless of whether enforcement is sought
in proceedings in equity or at law.  Each of  MDA and its
Subsidiaries has full corporate power and authority to carry on
its business as now conducted and to own or lease and to operate
its properties and assets where such properties and assets are
now owned, leased or operated by it and where such business is
now conducted by it.  Each of MDA and its Subsidiaries is duly
qualified to do business and is in good standing as a foreign
corporation and licensed or qualified to transact business in the
jurisdictions set forth in Section 3.1 of the MDA Disclosure
Schedule, which are the only jurisdictions where such
qualification is required by reason of the nature of the business
conducted by it or the properties or assets owned, operated or
leased by it, other than such failures to be so licensed or
qualified that in the aggregate would not have a MDA Material
Adverse Effect.  True, complete and correct copies of the
charter, By-laws and other analogous organizational documents
(the "Charter Documents") of MDA and each of its Subsidiaries as
in effect on the date hereof have heretofore been delivered to
Orbital.

     3.2.  No Violation or Approval.  Except as set forth in
Section 3.2 of the MDA Disclosure Schedule, the execution,
delivery and performance by MDA of this Agreement and the
consummation of the transactions contemplated hereby will not
result in a breach or violation of, or a default under, or the
acceleration of any payment obligation pursuant to, any law, rule
or regulation applicable to MDA and its Subsidiaries, any
material agreement or instrument to which any of them is a party
or by which any of them or any of their properties are bound, or
any order, judgment or decree of any court or any governmental
agency or body having jurisdiction over any of them or their
properties or in a breach or a default under any of their Charter
Documents.  No consent, approval, order or authorization of,
declaration or filing with, any governmental authority or entity
or other party is required to be obtained or made by MDA and its
Subsidiaries in connection with the execution and delivery of
this Agreement or the consummation by MDA of the transactions
contemplated hereby other than (i) any approvals required by the
Interim Order, (ii) the Final Order, (iii) filings with the
Director under the CBCA and filings with and approvals required
by provincial securities commissions and stock exchanges, (iv)
those approvals set forth in Section 3.2 of the MDA Disclosure
Schedule and (v) such failures to obtain or make such other
consents, approvals, orders, authorizations, declarations or
filings as in the aggregate would not have a MDA Material Adverse
Effect.

     3.3.  Capital Stock.  The authorized capital stock of MDA
consists of an unlimited number of MDA Common Shares and 232,000
Preference Shares, of which 205,000 shares have been designated
as Class A Preference Shares and 27,000 shares  have been
designated as Class B Preference Shares.  As of July 31, 1995,
there were 11,103,296 MDA Common Shares outstanding, 1,073,856
MDA Common Shares reserved for issuance upon the exercise of
outstanding MDA Options, 79,215 MDA Common Shares issuable to
shareholders of  Earth Observation Sciences Limited ("EOS") and
up to 250,000 MDA Common Shares issuable to former shareholders
of PSC Communications Group, Inc. ("PSC").  Since July 31, 1995,
MDA has not issued or obligated itself to issue (other than (i)
pursuant to MDA Options granted on or before July 31, 1995, (ii)
upon exchange of shares of common stock of EOS, or (iii) to
former shareholders of PSC in the event certain financial
performance targets are achieved), any shares of capital stock or
any outstanding options, warrants, rights, other agreements or
commitments obligating it to issue or sell shares of its capital
stock or any securities or obligations convertible into, or
exchangeable for, any shares of its capital stock.  No MDA Common
Shares are held as treasury stock or by any Subsidiary of MDA,
and no Preference Shares are outstanding.   All of the
outstanding MDA Common Shares have been, and any MDA Common
Shares issued upon exercise of any MDA Options or to shareholders
of EOS or former shareholders of PSC will be, validly issued,
fully paid and nonassessable and free of preemptive rights.
Except for the MDA Options (more fully described as to exercise
price and exercise period in Section 3.3 of the MDA Disclosure
Schedule) and the obligation to issue shares to EOS and to former
shareholders of PSC as described above, neither MDA nor any of
its Subsidiaries has any outstanding options, warrants, rights,
other agreements or commitments obligating it to issue or sell
shares of its capital stock or any securities or obligations
convertible into, or exchangeable for, any shares of its capital
stock.  Neither MDA nor any of its Subsidiaries has outstanding
any bonds, debentures, notes or other indebtedness the holders of
which have the right to vote (or that are convertible or
exercisable into securities having the right to vote) with
holders of MDA Common Shares or holders of the MDA 1988 Options
on any matter.  None of the outstanding shares of capital stock
of MDA or of its Subsidiaries was issued in violation of
Canadian provincial securities laws, the Securities Act or the
rules and regulations promulgated thereunder or the securities or
blue sky laws of any state or other jurisdiction, which
violations would have in the aggregate a MDA Material Adverse
Effect.

     3.4.  Subsidiaries.   Except for the equity investments set
forth in Section 3.4 of the MDA Disclosure Schedule, MDA does not
own, directly or indirectly, any capital stock, any partnership
or equity or other ownership interest in, or any security issued
by, any other corporation, organization, association, entity or
business enterprise, and Section 3.4 of the MDA Disclosure
Schedule indicates which such equity investments are Subsidiaries
of MDA and which are minority ownership interests.  Except as set
forth in Section 3.4 of the MDA Disclosure Schedule, MDA owns,
directly or indirectly,  all of the outstanding shares of each of
the entities listed thereon and identified as Subsidiaries of MDA
(except for directors' qualifying shares or such shares as may be
required by local laws to be owned by residents of the
jurisdiction of incorporation) free and clear of all liens,
pledges, security interests, mortgages, claims, charges and
encumbrances ("Liens").  All shares of capital stock owned by MDA
in any of its Subsidiaries are duly authorized, validly issued,
fully paid and nonassessable.

     3.5.  Securities Law Filings.  MDA has filed all proxy
circulars, reports and other documents required to be filed by it
after March 31, 1995 pursuant to the CBCA and all applicable
Canadian provincial securities laws or any rule or order of a
stock exchange on which MDA Common Shares are listed.  MDA has
provided to Orbital copies of MDA's Annual Report and its Annual
Information Form for the fiscal year ended March 31, 1995, and
all final proxy circulars, reports and other documents filed by
MDA pursuant to all such securities laws and/or stock exchange
rules or orders (collectively, the "Securities Reports").  Each
Securities Report was, as of the date of filing such report, in
compliance in all material respects with all applicable
requirements of its respective form and none of the Securities
Reports, as of their respective filing dates, contained any
untrue statement of a material fact or omitted to state a
material fact required to be stated therein or necessary to make
the statements therein, in light of the circumstances under which
they were made, not misleading.

     3.6.  Financial Statements, etc.  MDA has previously
furnished Orbital with true and complete copies of the following
financial statements (collectively, the "Financial Statements"):
(i) consolidated financial statements for the fiscal years ended
March 31, 1993, 1994 and 1995 audited by KPMG Peat Marwick
Thorne, and (ii) unaudited statements of income and cash flows
for the fiscal quarter ended June 30, 1995 and the accompanying
balance sheet as of June 30, 1995, each prepared from the books
and records of MDA and its consolidated Subsidiaries.  The
Financial Statements present fairly, in all material respects,
the consolidated financial position of MDA and the results of its
operations and its cash flows as of the respective dates and for
the periods presented therein in conformity with generally
accepted accounting principles in Canada as in effect on the
applicable dates of such financial statements ("Canadian GAAP")
and applied on a consistent basis, except as noted therein and
except that in the case of the unaudited financial statements, no
notes are included and such unaudited financial statements may be
subject to normal, recurring adjustments that would be made in
the course of an audit and that would not be material.  Except as
and to the extent reflected or reserved against in the balance
sheet as of  June 30, 1995 included in the Financial Statements
or as set forth in Section 3.6 of the MDA Disclosure Schedule,
MDA and its Subsidiaries, taken as a whole, do not have any
material liabilities or obligations of any nature.

     3.7.  Absence of Changes; Operations in the Ordinary Course.
Except as set forth in the Securities Reports or in Section 3.7
of the MDA Disclosure Schedule, since March 31, 1995 neither MDA
nor any of its Subsidiaries has undergone any adverse change in
its financial condition, or suffered any damage, destruction or
loss (whether or not covered by insurance) that adversely affects
its financial condition, the condition of its assets or the
ability to conduct its business other than such changes in
financial condition, damage, destruction or loss as in the
aggregate would not have a MDA Material Adverse Effect; and since
March 31, 1995, except as set forth in the Securities Reports or
in Section 3.7 of the MDA Disclosure Schedule, there has been no
adverse change in the condition of the business of MDA or any of
its Subsidiaries, whether as a result of any change as to
accounts receivable, inventory or other assets, any loss of
competitive position, any natural disaster, accident, strike,
sabotage, or confiscation of property, or any other event or
condition directly affecting or relating to MDA, whether or not
related to any of the foregoing, except for such changes as would
not in the aggregate have a MDA Material Adverse Effect and such
changes as are the result of changes in general economic or
industry wide conditions.  Since March 31, 1995, with the
exception of actions taken at the request of Orbital or otherwise
necessary to the consummation of the transactions contemplated by
this Agreement or the Plan of Arrangement, and except as set
forth in the Securities Reports or in Section 3.7 of the MDA
Disclosure Schedule, MDA and each of its Subsidiaries has
operated its business in the ordinary course, consistent in all
material respects with past practice.  Without limiting the
generality of the foregoing, since March 31, 1995, neither MDA
nor any of its Subsidiaries has:

     (a)  amended the terms of any outstanding indebtedness or
incurred any indebtedness for borrowed money that has not been
repaid in full, or issued or sold any of its debt or equity
securities, except in the ordinary course of business consistent
with past practice;

     (b)  subjected to any Lien or lease any of its properties,
tangible or intangible, except in the ordinary course of business
consistent with past practice;

     (c)  forgiven or canceled any debts owed to MDA or any of
its Subsidiaries or claims of MDA or any of its Subsidiaries, or
waived any rights, except in the ordinary course of business
consistent with past practice;

     (d)  incurred any liability or obligation (whether absolute,
accrued, contingent or otherwise) or made any payment in respect
of (i) any acquisition or disposition of any assets or properties
in any transaction with any officer, director, shareholder or
employee of MDA or any of its Subsidiaries, or any relative by
blood or marriage or any "affiliate" or "associate" of MDA or any
of its Subsidiaries (as such terms are defined in Rule 405
promulgated under the Securities Act), (ii) except as set forth
in Section 3.7 of the MDA Disclosure Schedule, any other
transaction with any such affiliate or associate of MDA or any of
its Subsidiaries, other than salaries paid to officers; or (iii)
any declaration, setting aside or payment of dividends or other
distributions in respect of, or purchases or redemptions
(directly or indirectly) of, any shares of its capital stock;
     
     (e)  proposed or adopted any amendments to its Charter
Documents except as contemplated by this Agreement or the Plan of
Arrangement;

     (f)  entered into or publicly announced an intention to
enter into any agreement (including, without limitation, an
agreement in principle) with respect to, any acquisition of a
material amount of assets or securities or any release or
relinquishment of any material contract rights not in the
ordinary course of business;

     (g)  made any capital expenditures other than in the
ordinary course of business consistent with past practice or as
necessary to maintain existing assets in good repair;

     (h)  entered into any line of business not described or
contemplated in MDA's Annual Report for the fiscal year ended
March 31, 1995;

     (i)  committed any act or omission that constitutes a
material breach or default by MDA or any of its Subsidiaries
under any material contract or material license to which MDA or
any of its Subsidiaries is a party or by which any of them or
their respective properties is bound;

     (j)  made any investment or commitment to make such an
investment in real estate or in any real estate development
project;

     (k)  except as disclosed in the Financial Statements or in
Section 3.7 of the MDA Disclosure Schedule:  (i) granted to any
officer or employee any increase in compensation in any form
(including without limitation any increase in value of any
benefits) in excess of the amount thereof in effect as of  March
31, 1995 other than increases in base salary or hourly wages of
employees other than officers of MDA in the ordinary course of
business in amounts consistent with past practice, or any
severance or termination pay, or entered into any employment
agreement with any employee that is not terminable by the
employer, without cause and without penalty, upon notice of 30
days or less, (ii) adopted or amended any bonus, profit-sharing,
compensation, stock option, pension, retirement, deferred
compensation or other plan, agreement, trust, fund or arrangement
for the benefit of employees (whether or not legally binding),
(iii) hired any employee who shall have total expected annual
compensation in excess of U.S.$100,000, or (iv) paid or incurred
any obligation to pay any bonus or fee to any employee (including
any officer) of MDA or any of its Subsidiaries or in connection
with the transactions contemplated by this Agreement; or

     (l)  agreed in writing or otherwise to do any of the
foregoing.

     3.8.  Taxes.

     (a)  For each of its taxation or taxable years or periods
ending on or prior to the date hereof :  (i)  all Tax Returns
that are required to have been filed by or with respect to MDA or
any of its Subsidiaries have been duly and timely filed and are
correct and complete in all material respects; (ii)  all income,
capital and corporate franchise Taxes with respect to or required
to have been paid by MDA or any of its Subsidiaries or for which
MDA or any of its Subsidiaries is or may otherwise be liable
(including without limitation all Consolidated Taxes), whether or
not shown on any Tax Return, have been paid in full if due or
accrued for in accordance with Canadian GAAP in the Financial
Statements through the date thereof and in the books and records
of MDA or the relevant Subsidiary in respect of subsequent
periods; and (iii)  all Taxes other than those described in
clause (ii) with respect to or required to have been paid by MDA
or any of its Subsidiaries or for which MDA or any of its
Subsidiaries is or may otherwise be liable, whether or not shown
on any Tax Return, have been paid in full if due or accrued for
in accordance with Canadian GAAP in the Financial Statements
through the date thereof and in the books and records of MDA or
the relevant Subsidiary in respect of subsequent periods except
for such amounts the nonpayment of which, in the aggregate, would
not result in a MDA Material Adverse Effect.

     (b)  Except as set forth in Section 3.8 of the MDA
Disclosure Schedule, (i) there are no audits, proceedings, or
litigation in respect of Taxes relating to MDA or any of its
Subsidiaries pending, in progress, or to MDA's knowledge,
threatened, (ii) there are no Tax Liens upon any property or
assets of MDA or any of its Subsidiaries other than Liens for
Taxes that are not yet due and payable, and (iii) neither MDA nor
any of its Subsidiaries has consented to any extension of any
statute of limitations pertaining to Taxes.

     (c)  Neither MDA nor any of its Subsidiaries is obligated as
a result of the transactions contemplated by this Agreement to
make a payment that would be a "parachute payment" to a
"disqualified individual" as those terms are defined in Section
280G of the Code without regard to whether such payment is
reasonable compensation for personal services performed or to be
performed in the future.

     (d)  MDA and each of its Subsidiaries has collected or
withheld all amounts required to be collected or withheld by it
on account of Taxes or otherwise, and has remitted the same to
the appropriate governmental authority in the manner and within
the time required under any applicable legislation or, if it is
not yet due, has set it aside in appropriate accounts for payment
when due.

     (e)  The liability for Taxes under the Income Tax Act
(Canada) of each of MDA and its Subsidiaries has been assessed by
Revenue Canada for all taxation years up to and including the
taxation years ending March 31, 1994.  True and complete copies
of the federal and provincial Tax Returns for MDA and each
Subsidiary for the taxation year ending March 31, 1994 and copies
of all assessments and reassessments relating to the most recent
taxation year for which the same are available have been provided
to Orbital.

     (f)  There are no circumstances that exist and would result,
or that have existed and resulted, in section 80 of the Income
Tax Act (Canada) applying to MDA or any of its Subsidiaries.

     3.9.  Properties.  MDA and each of its Subsidiaries do not
own any real property.  MDA and each of its Subsidiaries has good
and marketable title to all tangible personal property reflected
in the March 31, 1995 balance sheet included in the Financial
Statements or acquired since such date  (except for property
disposed of since such date in the ordinary course of business
consistent with past practice), and valid leasehold interests in
all real and tangible personal properties leased by it, in each
case free and clear of Liens, easements or title imperfections
except (a) Liens for current Taxes not yet due and payable, (b)
encumbrances and easements that do not materially detract from
the value or interfere with the use by MDA or any of its
Subsidiaries, as the case may be, of the properties affected
thereby, (c) Liens reflected in the Financial Statements, (d)
Liens of customers on property purchased by MDA in connection
with its performance of contracts to provide products or services
to such customers and which in the aggregate would not have a MDA
Material Adverse Effect,  and (e) Liens set forth in Section 3.9
of the MDA Disclosure Schedule.  MDA or its Subsidiary  as lessee
thereof enjoys peaceful and undisturbed possession under all
material leases under which it operates.  All tangible personal
property material for the conduct of the business of MDA and its
Subsidiaries as presently conducted is in satisfactory operating
condition and repair, subject to ordinary wear and tear.

     3.10.  Customers, Distributors and Suppliers.  Except as set
forth in Section 3.10 of the MDA Disclosure Schedule, neither MDA
nor any of its Subsidiaries has received notice from any person
or entity with which it has an existing agreement, oral or
written, for the purchase or distribution of products or services
from MDA or any of its Subsidiaries that it intends to reduce
significantly such purchases or terminate such agreement, whether
as a result of the transactions contemplated hereby or otherwise,
other than such reductions and actions as in the aggregate would
not have a MDA Material Adverse Effect.

     3.11.  Operations in Conformity With Law, etc.  Neither MDA
nor any of its Subsidiaries has been or is in violation of, or in
default under, any law, rule, regulation, order, judgment or
decree relating in any manner or applicable to the business or
assets of MDA or any of its Subsidiaries or any of their
respective employees, except for such violations or defaults that
in the aggregate would not have a MDA Material Adverse Effect.
Neither MDA or any of its Subsidiaries, nor, to the knowledge of
MDA or any of its Subsidiaries, any of their respective officers,
employees or agents has (a) directly or indirectly given or
agreed to give any illegal gift, contribution, payment or similar
benefit to any supplier, customer, governmental official or
employee or other person who was, is or may be in a position to
help or hinder MDA or any of its Subsidiaries (or assist in
connection with any actual or proposed transaction) or made or
agreed to make any illegal contribution, or reimbursed any
illegal political gift or contribution made by any other person,
to any candidate for Canadian or United States Federal,
provincial, state or local, or foreign public office
(collectively, a "Restricted Activity") that (i) would subject
MDA or any of its Subsidiaries to any damage or penalty in any
civil, criminal or governmental litigation or proceeding that
would have, in the aggregate, a MDA Material Adverse Effect,
(ii), if such Restricted Activity had occurred after the
Effective Date, would subject Orbital to any damage or penalty in
any civil, criminal or governmental litigation or proceeding that
would have, in the aggregate, a MDA Material Adverse Effect, or
(iii) if such Restricted Activities were to cease as of the date
hereof, such cessation would have a MDA Material Adverse Effect.
 .

     3.12. Litigation.  Except as set forth in Section 3.12 of
the MDA Disclosure Schedule, there are no actions, claims, suits,
investigations or proceedings pending or to MDA's knowledge
threatened against MDA or any of its Subsidiaries pertaining to
the business or assets of MDA or any of its Subsidiaries that, in
the aggregate, if adversely determined, would have a MDA Material
Adverse Effect or that question the validity of this Agreement or
any action taken or to be taken pursuant to or in connection with
the provisions of this Agreement, nor to the knowledge of MDA or
its Subsidiaries is there any basis for any such action, claim,
suit, proceeding or investigation.  There are no judgments,
orders, decrees, citations, fines or penalties heretofore
assessed (and not discharged or otherwise satisfied) against MDA
or any of its Subsidiaries under any Canadian or United States
Federal, provincial, state or local, or foreign law except for
such judgments, orders, decrees, citations, fines or penalties
that in the aggregate would not have a MDA Material Adverse
Effect.

     3.13.  Employee Matters; Benefit Plans.

     (a)  All plans, agreements, policies and arrangements
(including those sponsored by the Federal or any provincial
government of Canada), whether or not reduced to writing and
whether or not legally binding, to which MDA or any of its
Subsidiaries contributes or is obligated to contribute, or under
which MDA or any of its Subsidiaries has or may have any
liability for premiums or benefits, and which benefits any
active, former or retired employee, outside director, consultant
or other independent contractor who provides or provided services
to or for the benefit of MDA and its Subsidiaries, are listed in
Section 3.13 of the MDA Disclosure Schedule (the "Plans").  MDA
has delivered to Orbital, a true, correct and complete copy of
each written Plan (or a written summary of the material terms of
any Plan that has not been reduced to writing) any related trust
agreement and annuity or insurance contract, if any,  each Plan's
most recent annual report filed with the Internal Revenue Service
or Revenue Canada, if any, and all summary plan descriptions,
employee handbooks, or other similar employee communications with
respect to the Plans.

     (b)  Each Plan has been maintained and administered in
material compliance with its terms and with the requirements
prescribed by any and all applicable statutes, orders, rules and
regulations, and is, to the extent required by applicable law or
contract, fully funded without having any deficit or unfunded
actuarial liability; all required employer contributions under
any such Plans have been made and the applicable funds have been
funded in accordance with the terms thereof and no past service
funding liabilities exist thereunder; and all material
contributions, reserves or premium payments required to be made
as of the date hereof to the Plans have been made or provided
for.

     (c)  Each Plan that is required or intended to be qualified
under applicable law (including to the extent applicable, the
Employee Retirement Income Security Act of 1974, as amended
("ERISA"), and the Code, including without limitation Section
401(a) of the Code) or registered or approved by a government
agency or authority has been so qualified, registered or approved
by the appropriate governmental agency or authority, and nothing
has occurred since the date of the last qualification,
registration or approval to cause the appropriate governmental
agency or authority to revoke, or otherwise adversely affect,
such qualification, registration or approval.

     (d)  Except as set forth in Section 3.13 of the MDA
Disclosure Schedule, there are no pending or, to MDA's knowledge,
anticipated  claims against or otherwise involving any of the
Plans and no suit, action or other litigation (excluding claims
for benefits incurred in the ordinary course of Plan activities)
has been brought against or with respect to any such Plan.

     (e)  No Plan currently maintained by MDA is covered by Title
IV of ERISA.  Neither MDA nor any Subsidiary has incurred any
liability under Subtitle C or D of Title IV of ERISA with respect
to any "single-employer plan," within the meaning of Section
4001(a)(15) of ERISA, currently or formerly maintained by MDA,
any of its Subsidiaries or any entity that is considered one
employer with MDA under Section 4001 of ERISA.  Neither MDA nor
any such Subsidiary has incurred any withdrawal liability under
Subtitle E of Title IV of ERISA with respect to any
"multiemployer plan" within the meaning of Section 4001(a)(3) of
ERISA.

     (f)  Except as set forth in Section 3.13 of the MDA
Disclosure Schedule, neither MDA nor any of its Subsidiaries has
any obligations for retiree health and life benefits under any
Plan, and there are no restrictions on the rights of MDA or any
of its Subsidiaries to amend or terminate any such Plan without
incurring any liability thereunder.
     
     3.14.  Labor Relations.  There is no existing dispute or
controversy between MDA or any of its Subsidiaries and any of
MDA's or such Subsidiary's employees that would have a MDA
Material Adverse Effect.  Neither MDA nor any of its Subsidiaries
is a party to any collective bargaining agreement with respect to
any of its employees, none of such employees is represented by a
labor union and, to MDA's knowledge, there is no labor union
organizing activity by or among such employees.

     3.15.  Government Contracts and Subcontracts.  Except as and
to the extent reflected or reserved against in the balance sheet
dated as of March 31, 1995 included in the Financial Statements,
there are no claims, penalties, or causes of action against MDA
or any of its Subsidiaries the basis of which is an actual or
alleged violation of, or noncompliance with, any applicable law,
regulation or order  (a) related to a contract between MDA or any
of its Subsidiaries and the Canadian or United States Federal
government or the province of British Columbia or any other
provincial, state or local, or foreign government or any division
or agency of any of the foregoing (a "Government Contract"), or
(b) related to a contract between MDA or any of its Subsidiaries
and any other party which contract renders MDA or any of its
Subsidiaries a subcontractor at any tier to a prime contract with
the Canadian or the United States Federal government or the
province of British Columbia or any other provincial, state or
local, or foreign government or any division or agency of any of
the foregoing (a "Government Subcontract").  To the knowledge of
MDA and its Subsidiaries, there is no basis for a claim, penalty,
or cause of action against MDA or any of its Subsidiaries
alleging a violation of, or noncompliance with, any applicable
law, regulation or order related to any Government Contract or
Government Subcontract to which MDA or any of its Subsidiaries is
a party, except for such claims, penalties or causes of action as
do not, in the aggregate, have a MDA Material Adverse Effect.
For purposes of this Section 3.15, claims, penalties, and causes
of action alleging a violation of, or noncompliance with, any
applicable law, regulation or order include, but are not limited
to, those purporting to be based on failure to comply with cost
accounting standards, allowable costs, allocation of costs,
omissions or errors in disclosure statements, or defective
pricing.

     3.16.  Licenses, etc.   MDA and each of its Subsidiaries has
all governmental and regulatory licenses and permits necessary
for the conduct of its business as presently conducted except
where the failure to obtain or maintain such licenses and permits
would not, in the aggregate, have a MDA Material Adverse Effect.
All such licenses and permits are in full force and effect, and
no violations have been recorded in respect thereof.  Neither MDA
nor any of its Subsidiaries is in violation of any such license
or permit, and no proceeding or investigation is pending or, to
MDA's or any of its Subsidiaries' knowledge, threatened that
would have the effect, directly or indirectly, of revoking or
limiting in any way any such licenses or permits.

     3.17.  Environmental Matters.  MDA and each of its
Subsidiaries is and has at all times been in compliance in all
material respects with all applicable Canadian and United States
Federal, provincial, state and local, and foreign laws,
regulations, by-laws, ordinances, orders, directives and
decisions relating to environmental, natural resources, health
and safety matters.  There is no suit, claim, action or
proceeding pending or threatened against MDA or any of its
Subsidiaries or, to MDA's and each Subsidiary's knowledge, any
basis therefor, in respect of (i) noncompliance by MDA or any of
its Subsidiaries with any such laws, regulations, by-laws,
ordinances, orders, directives or decisions (ii) personal injury,
wrongful death, other tortious conduct, or relating to materials,
commodities or products held, used, sold, transferred,
manufactured or disposed of by or on behalf of MDA or any of its
Subsidiaries, containing or incorporating any hazardous or toxic
materials, commodities or substances, or (iii) the presence or
release or threatened release into the environment of any
pollutant, contaminant, deleterious or toxic or hazardous
material, substance or waste, whether solid, liquid or gas (each
a "Hazardous Substance"), whether generated by MDA or any of its
Subsidiaries or located at or about a site leased or otherwise
used by MDA or any of its Subsidiaries or heretofore owned,
leased or otherwise used by MDA or any of its Subsidiaries or any
predecessor entity.  To MDA's and each Subsidiary's knowledge,
there have been no Hazardous Substances of or generated by MDA or
any Subsidiary that have been disposed of or come to rest at any
site that has been included in any published United States
Federal, state or local "superfund" site list or any other list
of hazardous or toxic waste sites published by any governmental
authority in Canada or the United States.  To MDA's and each
Subsidiary's knowledge there are and have been no underground
storage tanks located on, no polychlorinated biphenyls ("PCBs")
or PCB-containing equipment used or stored on, and no hazardous
waste, as defined by the Resource Conservation and Recovery Act,
as amended, stored on, any site, leased or otherwise used by MDA
or any Subsidiary.  To MDA's and each Subsidiary's knowledge,
there have been no emissions or releases or threatened emissions
or releases of Hazardous Substances on, upon, into or from any
site leased or otherwise used by MDA or any of its Subsidiaries
or heretofore owned, leased or otherwise used by MDA or any of
its Subsidiaries or any predecessor entity.

     3.18.  Contractual Obligations, etc.  Section 3.18 of the
MDA Disclosure Schedule contains a true and complete list of all
contracts, agreements, deeds, mortgages, leases (whether or not
capitalized), licenses, instruments, commitments, sales orders,
purchase orders, quotations, bids, undertakings, arrangements or
understandings, written or oral (each, a "Contract") to which or
by which MDA or any of its Subsidiaries is a party or otherwise
bound or to which or by which any of MDA's or its Subsidiaries'
assets are subject of the types described below and in effect on
the date hereof (Contracts of the type described below,
collectively, the "Contractual Obligations").

     (a)  All Contracts relating to noncompetition;

     (b)  All Contracts to which any employee is a party, other
than option agreements relating to the MDA Options and employment
offer letters that are terminable by MDA at will (subject only to
reasonable notice) and the employment agreements to be entered
into, pursuant to Section 6.2.5 hereof, in substantially the form
of Exhibit 3.18 (the "Employment Agreements");

     (c)  All Contracts relating to the provision of consulting
services that involve liabilities or obligations of MDA or any of
its Subsidiaries in excess of C$150,000 or that have a term
extending more than one year after the Closing Date;

     (d)  All Contracts (including without limitation options) to
sell (other than sales of products) or lease (as lessor) any
property or asset owned or leased by MDA or any of its
Subsidiaries, other than property or assets having individual
values less than C$50,000 and an aggregate value less than
C$300,000;

     (e)  All Contracts pursuant to which MDA or any of its
Subsidiaries possesses or uses (including as lessee) any
properties or assets in its business the loss of use of which
would have a MDA Material Adverse Effect, or pursuant to which
MDA pays, accrues expenses of or incurs charges of at least
C$50,000 per annum;

     (f)  All Contracts for the sale of products or provision of
services by MDA or any of its Subsidiaries that individually
involve products or services having a value of at least C$250,000
or that have a term extending more than one year after the
Closing Date;

     (g)  All Contracts with suppliers or providers of goods or
services (other than cleaning, trash removal, facilities
maintenance or repair, or similar services and other than agent
or representation agreements terminable upon no more than one
year's notice) to MDA or any of its Subsidiaries, including
without limitation purchase orders, that individually involve
liabilities in excess of C$100,000; and

     (h)  Each other Contract (other than Contracts of the type
described in (a) through (g) of this Section 3.18) that involves
liabilities or obligations of MDA or any of its Subsidiaries in
excess of C$150,000 or that has a term extending more than one
year after the Closing Date.

MDA shall make available to Orbital upon request a true and
complete copy of each of the Contractual Obligations referred to
in (a) through (h) except as otherwise  provided in Section 3.19
below.  Other than defaults resulting from claims, penalties or
causes of action disclosed in Section 3.15 or Section 3.18 of the
MDA Disclosure Schedule, neither MDA nor any of its Subsidiaries
nor, to the knowledge of MDA or its Subsidiaries, any other party
is in default under or in breach or violation of, nor has an
event occurred that (with or without notice, lapse of time or
both) would constitute a default by MDA or any of its
Subsidiaries or to MDA's knowledge by any other party, under any
Contractual Obligations which defaults, in the aggregate, have a
MDA Material Adverse Effect.

     3.19.  EarthWatch Agreement.  MDA has executed one or more
contracts with EarthWatch, Inc. ("EarthWatch") (collectively, the
"EarthWatch Agreement") which provides, among other things, that
MDA shall make an equity investment in EarthWatch and build a
portion of EarthWatch's image data archival and processing
facility.  In lieu of providing to Orbital a copy of the
EarthWatch Agreement, Section 3.19 of the Disclosure Schedule
describes,  to MDA's belief, all of MDA's material obligations
(financial or otherwise) under the EarthWatch Agreement.

     3.20.  Affiliated Transactions.  Except for Contracts
described in Section 3.18(b), none of the directors, officers,
shareholders or employees of MDA or any of its Subsidiaries, or
any relative by blood or marriage or any "affiliate" or
"associate" (as such terms are defined in Rule 405 promulgated
under the Securities Act) of any of the foregoing, is currently a
party to any Contractual Obligation.

     3.21.  Patents, Trademarks, etc.  Section 3.21 of the MDA
Disclosure Schedule contains a complete and correct list of all
patents, patent applications, trade names, trademarks, trademark
applications, service marks, copyrights and copyright
applications owned or used by MDA or any of its Subsidiaries.
MDA and each of its Subsidiaries owns, or pursuant to license
agreements possesses adequate rights to use, all patents, trade
names, trademarks, copyrights, inventions, processes, designs,
formulas, trade secrets, know-how and other intellectual property
and proprietary rights (collectively, the "Intellectual Property
Rights") used in or necessary in all material respects for the
conduct of its business with no known conflict with or
infringement of the asserted rights of others.  With respect to
any such Intellectual Property Right owned by MDA or any of its
Subsidiaries, MDA or such Subsidiary is the sole and exclusive
owner of, with all right, title and interest in and to, free and
clear of any Lien, such Intellectual Property Right and MDA and
its Subsidiaries have sole and exclusive rights (and except as
reflected in the Financial Statements, are not contractually
obligated to pay any compensation to any third party in respect
thereof) to the use thereof.  To the best of MDA's knowledge (i)
all inventions, processes, designs, formulas, trade secrets, know-
how and other intellectual property that are material and have
not been patented or copyrighted have been kept confidential and
(ii) no third party is currently infringing or has infringed the
rights of MDA or any of its Subsidiaries under any patent, trade
name, trademark or copyright owned by MDA or any of its
Subsidiaries.

     3.22.  Insurance.  Section 3.22 of the MDA Disclosure
Schedule contains a summary description of all insurance policies
maintained by MDA or its Subsidiaries, all of which policies are
in full force and effect.

     3.23.  Customer Warranty Coverage.  Section 3.23 of the MDA
Disclosure Schedule contains a description of all warranty
coverages (including terms of such coverages, expiration dates,
and estimated amounts of liability) extended by MDA or any of its
Subsidiaries for repair or replacement of defective products or
service to its customers as of the date indicated thereon.  The
estimated liability for warranty claims is fairly reflected in
the Financial Statements.

     3.24.  Pooling.  Neither MDA nor, to MDA's knowledge, any of
its "affiliates" (as defined in Opinion No. 16, as amended, of
the Accounting Principles Board of the American Institute of
Certified Public Accountants and the interpretive rulings issued
thereunder) has taken or agreed to take any action that would
prevent Orbital from accounting for the business combination to
be effected by the Plan of Arrangement as a pooling-of-interests.

     3.25.  Certain Agreements.  Except as set forth in Section
3.25 of the MDA Disclosure Schedule, neither the execution and
delivery of this Agreement nor the consummation of the
transactions contemplated hereby or by the Plan of Arrangement
will (i) result in any payment (including, without limitation,
severance, unemployment compensation, parachute payment, bonus or
otherwise) becoming due to any director, employee or independent
contractor of MDA or its Subsidiaries, from MDA or any of its
Subsidiaries under any Plan, agreement or otherwise, (ii) except
as contemplated by the Employment Agreements, increase any
benefits otherwise payable under any Plan or agreement, or (iii)
result in the acceleration of the time of payment or vesting of
any such benefits.

     3.26.  Opinion of Financial Advisor.  MDA has received the
opinion of Nesbitt Burns, dated the date hereof, to the effect
that, as of such date, the consideration to be received in the
Arrangement by MDA's shareholders and the holders of the MDA 1988
Options is fair to MDA's shareholders and the holders of the MDA
1988 Options from a financial point of view, a copy of which
opinion has been provided to Orbital.

     3.27.  Brokers, Finders, etc.  All negotiations relating to
this Agreement and the transactions contemplated hereby have been
carried on without the intervention of any person acting on
behalf of MDA in such manner as to give rise to any valid claim
against MDA or Orbital for any brokerage or finder's commission,
fee or similar compensation, except for fees payable to Nesbitt
Burns pursuant to the engagement letter between it and MDA, dated
June 16, 1995, a copy of which has been provided to Orbital.

     3.28.  Disclosure; Provision of Information. This Agreement,
including the Exhibits hereto and the MDA Disclosure Schedule,
the certificates delivered or to be delivered in connection
herewith and the Securities Reports, taken as a whole, do not
contain any untrue statement of a material fact or omit to state
a material fact necessary to make the statements herein or
therein not misleading.   The proxy circular or other disclosure
document and any amendment or supplement thereto to be
distributed in connection with MDA's meeting of its shareholders
and the holders of the MDA 1988 Options to vote upon the
Arrangement (the "Proxy Circular") will, at the time of the
mailing thereof and at the time of such meeting, not contain any
misrepresentation (within the meaning of any applicable Canadian
or United States Federal, provincial or state securities laws) or
any untrue statement of a material fact or omit to state a
material fact necessary to be stated therein or necessary to make
the statements therein, in light of the circumstances in which
they are made, not misleading and comply as to form in all
material respects with the provisions of all applicable laws,
including the provisions of the CBCA and the rules and
regulations thereunder, except that no representation is made by
MDA with respect to information supplied by or on behalf of
Orbital or Acquisition specifically for inclusion therein.  None
of the information supplied or to be supplied by or on behalf of
MDA or its Subsidiaries for inclusion in (i) the Plan of
Arrangement, (ii) the request for a "no action letter" submitted
by Orbital to the SEC seeking to confirm the availability of an
exemption under Section 3(a)(10) of the Securities Act for the
issuance of the Exchangeable Shares and an exemption under
Section 3(a)(9) or 3(a)(10) of the Securities Act for the
issuance of Orbital Common Shares in exchange for the
Exchangeable Shares and any requests to Canadian securities
regulators for rulings or orders to permit the Arrangement and
related transactions to be carried out without prospectus or
registration requirements (collectively, the "No Action
Request"); or (iii) any registration statement and any amendment
thereto required to be filed under the Securities Act by Orbital
in connection with the issuance of the Exchangeable Shares or the
Orbital Common Shares in or as a result of the Arrangement (a
"Registration Statement") will (a) in the case of the Plan of
Arrangement, at the time the Plan of Arrangement is considered by
the Court, (b) in the case of the No Action Request, at the time
the No Action Request, as amended or supplemented, is acted on by
the SEC or Canadian securities regulators, as the case may be, or
(c) in the case of any Registration Statement, at the time it
becomes effective and at the time of any post-effective amendment
thereto, contain any misrepresentation (within the meaning of any
applicable Canadian or United States Federal, provincial or state
securities laws) or any untrue statement of a material fact or
omit to state any material fact required to be stated therein or
necessary to make the statements therein, in light of the
circumstances in which they are made, not misleading.


                         ARTICLE 4
         REPRESENTATIONS AND WARRANTIES OF ORBITAL
                         AND ACQUISITION


     In order to induce MDA to enter into this Agreement, each of
Orbital and Acquisition jointly and severally represents and
warrants as follows:

     4.1.  Due Organization, Authorization and Good Standing of
Orbital and Acquisition.  Orbital is a corporation duly
organized, validly existing and in good standing under the laws
of the State of Delaware.  Acquisition is a corporation duly
organized, validly existing and in good standing under the CBCA.
Each other Subsidiary of Orbital is a corporation or limited
partnership duly organized or formed, validly existing and in
good standing under the laws of the jurisdiction of its
organization or formation.  Each of Orbital and Acquisition has
the requisite corporate power and authority to execute, deliver
and perform its obligations under this Agreement and to
consummate all transactions contemplated hereby.  The execution,
delivery and performance of this Agreement by each of them, and
the consummation of the transactions contemplated hereby have
been duly and validly authorized and approved by all necessary
corporate action in respect thereof on the part of each of
Orbital and Acquisition.  This Agreement constitutes the valid
and binding obligation of each of Orbital and Acquisition,
enforceable in accordance with its terms, subject to bankruptcy,
insolvency, moratorium, reorganization and similar laws of
general applicability affecting the rights and remedies of
creditors and to general principles of equity, regardless of
whether enforcement is sought in proceedings in equity or at law.
Each of Orbital, Acquisition and each other Subsidiary of Orbital
has full corporate or partnership power and authority to carry on
its business as now conducted and to own or lease and to operate
its properties and assets where such properties and assets are
now owned, leased or operated by it and where such business is
now conducted by it.  Each of Orbital, Acquisition and each other
Subsidiary of Orbital is duly qualified to do business and in
good standing as a foreign corporation or limited partnership and
licensed or qualified to transact business in each jurisdiction
in which the nature of the business conducted by it or the
properties or assets owned, operated or leased by it requires it
to be so licensed or qualified, other than such failures to be so
licensed or qualified that, in the aggregate, would not have an
Orbital Material Adverse Effect.  True, complete and correct
copies of the Charter Documents of Orbital and Acquisition as in
effect on the date hereof have heretofore been delivered to MDA.

     4.2.  No Violation or Approval.  Except as set forth in
Section 4.2 of the disclosure schedule prepared by Orbital and
provided to MDA concurrently with the execution of this Agreement
(the "Orbital Disclosure Schedule"),the execution, delivery and
performance by Orbital and Acquisition of this Agreement and the
consummation of the transactions contemplated hereby will not
result in a breach or violation of, or a default under, any law,
rule or regulation, order, judgment or decree applicable to
Orbital, Acquisition or any other Subsidiary of Orbital, any
material agreement or instrument to which any of them is a party
or by which any of them or any of their respective properties are
bound, or any order, judgment or decree of any court or any
governmental agency or body having jurisdiction over any of them
or their properties or in a breach or a default under their
Charter Documents other than any breach, violation or default
that would not have an Orbital Material Adverse Effect.  No
consent, approval, order or authorization of, or declaration or
filing with, any governmental authority or entity or other party
is required of and has not been obtained or made by Orbital or
Acquisition in connection with the execution and delivery of this
Agreement or the consummation of the transactions contemplated
hereby other than (i) any approvals required by the Interim
Order, (ii) the Final Order, (iii) filings with the Director
under the CBCA and filings with and approvals required by
provincial securities commissions and stock exchanges, (iv) the
filing and effectiveness of any required Registration Statement
and (v) such failures to obtain or make consents, approvals,
orders, authorizations, declarations or filings as in the
aggregate would not have an Orbital Material Adverse Effect.

     4.3.  Capital Stock.  The authorized capital stock of
Orbital consists of (i) 40,000,000 shares of Orbital Common
Shares, of which, as of August 10, 1995, approximately 22,662,618
shares are outstanding; and (ii) 10,000,000 shares of Preferred
Stock, U.S.$.01 par value per share, of which, as of the date
hereof, no shares are outstanding.  Upon issuance of the Orbital
Common Shares in exchange for the Exchangeable Shares as provided
in the Plan of Arrangement, such shares shall be validly issued,
fully paid and nonassessable, free of preemptive rights and free
of all Liens other than such as arise under applicable securities
laws.  The Orbital Common Shares to be issued pursuant to the
Plan of Arrangement will be issued in full compliance with all
Canadian provincial securities laws and the Securities Act and
the rules and regulations promulgated thereunder and all other
relevant securities or blue sky laws of any state or other
jurisdiction.  No class of capital stock of Orbital is entitled
to preemptive rights.  As of the date hereof, there are no
outstanding options, warrants, rights or other agreements or
commitments obligating Orbital to issue or sell shares of its
capital stock or any securities or obligations convertible into
or exchangeable for any shares of its capital stock, except (i)
up to 3,895,692 shares of Common Stock issuable upon conversion
of Orbital's Convertible Subordinated Debentures due 2003; (ii)
the Orbital Common Shares to be issued in exchange for the
Exchangeable Shares and upon exercise of the Replacement Options
in accordance with the terms of this Agreement and the Plan of
Arrangement and (iii) up to 2,025,000 shares of Orbital Common
Shares authorized for issuance under Orbital's stock option plans
(true and complete copies of which plans have been made available
to MDA by Orbital).  None of the outstanding shares of capital
stock of Orbital was issued in violation of the Securities Act or
the securities or blue sky laws of any state or jurisdiction
which violation would have an Orbital Material Adverse Effect.

     The authorized capital stock of Acquisition consists of an
unlimited number of shares of common stock of which, as of the
date hereof, 1,000 shares are outstanding and all of which are
owned by Orbital.  All of the outstanding shares of common stock
of Acquisition have been, and any Class B Preferred Shares and
Exchangeable Shares issued pursuant to the Plan of Arrangement
will be, validly issued, fully paid and nonassessable, and free
of preemptive rights.  The Class B Preferred Shares and
Exchangeable Shares to be issued pursuant to the Plan of
Arrangement will be issued in full compliance with all applicable
Canadian provincial securities laws and with the Securities Act
and the rules and regulations promulgated thereunder and all
other relevant securities or blue sky laws of any state.
Acquisition does not have any outstanding options, warrants,
rights, other agreements or commitments obligating Acquisition to
issue or sell shares of its capital stock or any securities or
obligations convertible into, or exchangeable for, any shares of
its capital stock.  None of the outstanding shares of capital
stock of Acquisition was issued in violation of any applicable
Canadian provincial securities laws, the Securities Act or the
rules and regulations promulgated thereunder or the securities or
blue sky laws of any state which violation would have an Orbital
Material Adverse Effect.

     4.4.  SEC Reports.  Orbital has filed all proxy statements,
reports and other documents required to be filed by it under the
Exchange Act after December 31, 1994, and Orbital has made
available to MDA copies of Orbital's Annual Report on Form 10-K
for the fiscal year ended December 31, 1994, and all final proxy
statements and reports filed by Orbital under the Exchange Act
after such date, each as filed with the SEC (collectively, the
"SEC Reports").  Each SEC Report was, as of the date of filing of
such report, in compliance in all material respects with the
requirements of its respective form and none of the SEC Reports,
as of their respective dates, contained any untrue statement of a
material fact or omitted to state a material fact required to be
stated therein or necessary to make the statements therein, in
the light of the circumstances under which they were made, not
misleading.

     4.5.  Financial Statements, etc.  Orbital has previously
furnished MDA with true and complete copies of the following
financial statements (collectively, the "Orbital Financial
Statements"):  (i) consolidated financial statements for the
fiscal years ended December 31, 1992, 1993 and 1994 audited by
KPMG Peat Marwick, and (ii) unaudited statements of income and
cash flows for the fiscal quarters ended March 31 and June 30,
1995 and the accompanying balance sheets as of such dates each
prepared from the books and records of Orbital and its
consolidated Subsidiaries.  The Orbital Financial Statements
present fairly, in all material respects, the consolidated
financial position of Orbital and the results of its operations
and its cash flows as of the respective dates and periods thereof
in conformity with generally accepted accounting principles in
the United States as in effect on the applicable dates of such
financial statements ("US GAAP") and applied on a consistent
basis, except as noted therein and except that in the case of the
unaudited financial statements, no notes are included and such
unaudited financial statements may be subject to normal,
recurring adjustments that would be made in the course of an
audit and that would not be material.  Except as and to the
extent reflected or reserved against in the balance sheet as of
June 30, 1995 included in the Orbital Financial Statements,
Orbital and its Subsidiaries, taken as a whole, do not have any
material liabilities or obligations of any nature.

     4.6.  Absence of Changes.  Since December 31, 1994, except
as set forth in the SEC Reports (copies of which have all been
provided by Orbital to MDA), neither Orbital nor any of its
Subsidiaries has undergone any adverse change in its financial
condition, or suffered any damage, destruction or loss (whether
or not covered by insurance) that adversely affects its financial
condition, the condition of its assets or the ability to conduct
its business other than such changes in condition, damage,
destruction or loss as in the aggregate would not have an Orbital
Material Adverse Effect or that are the result of changes in
general economic or industry wide conditions; and since December
31, 1994, except as set forth in the SEC Reports, there has been
no adverse change in the condition of the business of Orbital or
any of its Subsidiaries, whether as a result of any change as to
accounts receivable, inventory or other assets, any loss of
competitive position, any natural disaster, accident, strike,
sabotage, or confiscation of property, or any other event or
condition directly affecting or relating to Orbital, whether or
not related to any of the foregoing (including without limitation
labor disputes, environmental audits or disclosures, and
intellectual property disputes), except for such changes as would
not in the aggregate have an Orbital Material Adverse Effect and
such changes as are the result of changes in general economic or
industry wide conditions.

     4.7.  Pooling.  Neither Orbital nor, to Orbital's knowledge,
any of its "affiliates" (as defined in Opinion No. 16, as
amended, of the Accounting Principles Board of the American
Institute of Certified Public Accountants and the interpretive
rulings issued thereunder) has taken or agreed to take any action
that would prevent the parties from accounting for the business
combination to be effected by the Plan of Arrangement as a
pooling of interest.

     4.8.  Operations in Conformity With Law, etc.  Neither
Orbital nor any of its Subsidiaries has been or is in violation
of, or in default under, any law, rule, regulation, order,
judgment or decree relating in any manner or applicable to the
business or assets of Orbital or any of its Subsidiaries or any
of their respective employees, except for such violations or
defaults that in the aggregate would not have an Orbital Material
Adverse Effect.

     4.9.  Litigation.  Except as set forth in the Section 4.9 of
the Orbital Disclosure Schedule, there are no actions, claims,
suits, investigations or proceedings pending or to Orbital's
knowledge threatened against Orbital or any of its Subsidiaries
pertaining to the business or assets of Orbital or any of its
Subsidiaries that, in the aggregate, if adversely determined,
would have an Orbital Material Adverse Effect or that question
the validity of this Agreement or  any action taken or to be
taken pursuant to or in connection with the provisions of this
Agreement, nor to the knowledge of Orbital or its Subsidiaries is
there any basis for any such action, claim, suit, proceeding or
investigation.  There are no judgments, orders, decrees,
citations, fines or penalties heretofore assessed (and not
discharged or otherwise satisfied) against Orbital or any of its
Subsidiaries under any Canadian or United States Federal,
provincial, state or local, or foreign law except for such
judgments, orders, decrees, citations, fines or penalties that in
the aggregate would not have an Orbital Material Adverse Effect.

     4.10.  Government Contracts and Subcontracts.  Except as and
to the extent reflected or reserved against in the balance sheet
dated as of December 31, 1994 included in the Orbital Financial
Statements, there are no known claims, penalties, or causes of
action against Orbital or any of its Subsidiaries the basis of
which is an actual or alleged violation of, or noncompliance
with, any applicable law, regulation or order, related to a
Government Contract or a Government Subcontract to which Orbital
or any of its Subsidiaries is a party, except for such claims,
penalties or causes of action which would not, in the aggregate
have an Orbital Material Adverse Effect.  To the knowledge of
Orbital and its Subsidiaries, there is no basis for a claim,
penalty, or cause of action against Orbital or any of its
Subsidiaries alleging a violation of, or noncompliance with, any
applicable law, regulation or order related to any Government
Contract or Government Subcontract to which Orbital or any of its
Subsidiaries is a party except for such claims, penalties or
causes of action as would not have in the aggregate an Orbital
Material Adverse Effect.  For purposes of this Section 4.10,
claims, penalties, and causes of action alleging a violation of,
or noncompliance with, any applicable law, regulation or order
include, but are not limited to, those purporting to be based on
failure to comply with cost accounting standards, allowable
costs, allocation of costs, omissions or errors in disclosure
statements, or defective pricing.

     4.11.  Environmental Matters. Orbital and its Subsidiaries
have obtained all permits, licenses and other authorizations that
are required under all federal, state, local and foreign
statutes, laws, regulations, ordinances, rules, judgments,
orders, decrees, permits, concessions, grants, franchises,
licenses, agreements or other governmental restrictions relating
to the environment or to emissions, discharges or releases of
pollutants, contaminants, petroleum or petroleum products,
chemicals or industrial, toxic or hazardous substances or wastes
into the environment including, without limitation, ambient air,
surface water, ground water, or land, or otherwise relating to
the manufacture, processing, distribution, use, treatment,
storage, disposal, transport or handling of pollutants,
contaminants, petroleum or petroleum products, chemicals or
industrial, toxic or hazardous substances or wastes or the clean-
up or other remediation thereof (the "Environmental Laws"),
except to the extent failure to have any such permit, license or
authorization would not have an Orbital Material Adverse Effect
and (ii) Orbital and its Subsidiaries are in compliance with the
terms and conditions of all such permits, licenses and
authorizations, and are also in compliance with all other
provisions of any applicable Environmental Law or any order,
judgment, injunction, notice or demand letter issued or entered
thereunder, except to the extent failure to comply would not have
an Orbital Material Adverse Effect.

     4.12.  Disclosure. This Agreement, including the Exhibits
hereto and the Orbital Disclosure Schedule, the certificates
delivered or to be delivered in connection herewith and the SEC
Reports referenced hereby, taken as a whole, does not contain any
untrue statement of a material fact or omit to state a material
fact necessary to make the statements herein or therein not
misleading.   The Registration Statement will, at the time it
becomes effective and at the time of any post-effective amendment
thereto, not contain any misrepresentation (within the meaning of
any applicable Canadian or United States Federal, provincial or
state securities laws) or any untrue statement of a material fact
or omit to state a material fact required to be stated therein or
necessary to make the statements therein, in light of the
circumstances in which they are made, not misleading, and comply
as to form in all material respects with the provisions of all
applicable laws, including the provisions of the Securities Act
and the Exchange Act and the rules and regulations of the SEC
thereunder, except that no representation is made by Orbital with
respect to information supplied by or on behalf of MDA
specifically for inclusion therein.   None of the information
supplied or to be supplied by or on behalf of Orbital or its
Subsidiaries for inclusion in (i) the Plan of Arrangement, (ii)
the No Action Request; or (iii) the Proxy Circular, will (a) in
the case of the Plan of Arrangement, at the time the Plan of
Arrangement is considered by the Court, (b) in the case of the No
Action Request, at the time the No Action Request, as amended or
supplemented, is acted on by the SEC or Canadian securities
regulators, as the case may be, or (c) in the case of the Proxy
Circular and any amendment or supplement thereto, at the time of
the mailing of the Proxy Circular and any amendment or supplement
thereto, and at the time of the meeting of shareholders of MDA
and the holders of the MDA 1988 Options to vote upon the
Arrangement, contain any misrepresentation (within the meaning of
any applicable Canadian or United States Federal, provincial or
state securities laws) or any untrue statement of a material fact
or omit to state any material fact required to be stated therein
or necessary to make the statements therein, in light of the
circumstances in which they are made, not misleading.
     
     
                         ARTICLE 5
                     CERTAIN COVENANTS

     5.1.  Preparation of Proxy Statement and No Action Request;
Other Filings and Submissions.  Orbital, Acquisition and MDA
shall cooperate in (i) the preparation of the Proxy Statement,
the No Action Request and any required Registration Statement and
any other documents reasonably deemed by Orbital or MDA to be
necessary to discharge their respective obligations under United
States and Canadian securities laws in connection with the
Arrangement and the other transactions contemplated hereby, (ii)
the taking of all such action as may be required under any
applicable provincial or state securities laws (including "blue
sky laws") in connection with the issuance of the Exchangeable
Shares and the Orbital Common Shares in the Arrangement;
provided, however, that with respect to United States blue sky
and Canadian provincial qualifications none of Orbital,
Acquisition or MDA shall be required to register or qualify as a
foreign corporation or to take any action that would subject it
to service of process in any jurisdiction where any such entity
is not now so subject, except as to matters and transactions
arising solely from the offer and sale of the Exchangeable Shares
and the Orbital Common Shares, (iii) the taking of all such
action as may be required under the CBCA in connection with the
transactions contemplated by this Agreement and the Plan of
Arrangement, and (iv) the preparation of a Registration Statement
of Orbital on Form S-8 covering issuances of Orbital Common
Shares upon exercise of the Replacement Options.  Orbital,
Acquisition and MDA shall each use all reasonable efforts to list
the Exchangeable Shares on a stock exchange in Canada, unless in
connection with obtaining a favorable response to the No Action
Request, Orbital is advised by the staff of the SEC that in their
view the listing of such shares will in and of itself preclude
the granting of the requested exemptions from registration
requested in the No Action Request.  Orbital, Acquisition and MDA
shall each furnish to one another all such information as may be
required for the effectuation of the foregoing actions, and each
covenants that no information furnished in connection with such
actions or otherwise in connection with the consummation of the
Arrangement and the other transactions contemplated by this
Agreement will contain any untrue statement of a material fact or
omit to state a material fact required to be stated in order to
make any information so furnished not misleading.  Orbital and
MDA shall each promptly notify the other if at any time before or
after the Effective Time it becomes aware that the Proxy Circular
or Registration Statement (or any prospectus related thereto), if
required, contains any untrue statement of a material fact or
omits to state a material fact required to be stated therein or
necessary to make the statements contained therein not
misleading.  In any such event, Orbital and MDA shall cooperate
in the preparation of a supplement or amendment to the Proxy
Circular or Registration Statement (and any prospectus related
thereto), if required, as the case may be, that corrects such
misstatement or omission, and shall cause the same to be
distributed to shareholders of MDA or Acquisition, as the case
may be, and, if required, filed with (and shall use its best
efforts to have the same declared effective by) the SEC.

     5.2.  Shareholders' Meeting. MDA shall duly call, give
notice of, convene and hold a meeting of its shareholders and the
holders of the MDA 1988 Options as promptly as practicable for
the purpose of voting upon the Arrangement (the "Shareholder
Meeting").  Subject to Section 5.3, MDA shall, through its Board
of Directors, recommend to its shareholders and the holders of
the MDA 1988 Options approval of the Arrangement and shall use
all reasonable efforts to hold such meeting as soon as
practicable after the date hereof ("Shareholder Meeting Date"),
and shall use all reasonable efforts to secure the approval by
its shareholders, the holders of the MDA 1988 Options and the
Court of the Arrangement.

     5.3.  Exclusivity; Acquisition Proposals.  Unless and until
this Agreement shall have been terminated by either party
pursuant to Section  7.1 hereof, except as required by law, MDA
shall not (and it shall use its best efforts to ensure that none
of its officers, directors, agents, representatives or
affiliates) take or cause or permit any Subsidiary to take,
directly or indirectly, any of the following actions with any
party other than Orbital and its designees or agents:  (i)
solicit, encourage, initiate or participate in any negotiations,
inquiries or discussions with respect to any offer or proposal to
acquire all or any significant part of its business, assets or
capital shares whether by arrangement, amalgamation, merger,
consolidation, other business combination, purchase of assets,
tender or exchange offer or otherwise (each of the foregoing an
"Acquisition Transaction"); (ii) disclose any information not
customarily disclosed to any person concerning its business or
properties or afford to any person or entity access to its
properties, books or records, except in the ordinary course of
business consistent with past practice and as required pursuant
to a governmental request for information; (iii) enter into or
execute any agreement relating to an Acquisition Transaction,
plan of reorganization, or other agreement calling for the sale
of all or any significant part of its business and properties; or
(iv) make or authorize any public statement, recommendation or
solicitation with respect to any Acquisition Transaction or any
offer or proposal relating to an Acquisition Transaction other
than with respect to the Arrangement; provided, however, that
nothing contained herein shall limit the power of the MDA Board
of Directors to withdraw or modify any recommendation with
respect to the Plan of Arrangement if an adverse material change
occurs in the business or affairs of Orbital or in any of the
information provided by Orbital on which the MDA Board of
Directors has based any recommendation.  Further, if any person
proposes an unsolicited bona fide Acquisition Transaction that in
the opinion of MDA's Board of Directors (having consulted its
financial advisors) offers terms that may be more favorable to
the MDA shareholders than pursuant to this Agreement or the Plan
of Arrangement, MDA shall have seven business days to consider
such proposal, following which time the MDA Board of Directors
may withdraw or modify any recommendation with respect to the
Plan of Arrangement only if to do so would, in the opinion of the
Board of Directors (having consulted outside counsel), acting
reasonably, be a proper exercise of the directors' fiduciary
duty.  Notwithstanding the provisions of Section 5.2, if such
unsolicited bona fide Acquisition Transaction is proposed within
the seven-business-day period preceding the Shareholder Meeting,
then the MDA Board of Directors may recommend or support a
proposal to postpone or adjourn such meeting for not more than 10
business days, provided that  nothing shall entitle MDA or its
Board of Directors to terminate this Agreement (except pursuant
to and in accordance with the provisions of Section 7.1 hereof),
not to proceed with the Shareholder Meeting or to withdraw from
the MDA shareholders the vote on the Plan of Arrangement.  In the
event MDA shall be required by law to take any action described
in the two immediately preceding sentences or receives any offer
or proposal, directly or indirectly, of the type referred to in
clause (i) above, or any request for disclosure or access with
respect to information of the type referred to in clause (ii)
above, it shall immediately, and prior to taking any action in
response thereto, inform Orbital as to all material facts
concerning any such offer, proposal or request (to the extent not
otherwise restricted by confidentiality obligations), including
the identity of the party making the offer, proposal or request,
and will thereafter cooperate with Orbital by informing Orbital
of additional material facts as they arise and furnishing to
Orbital any additional information as is furnished to any third
party making such proposal or requesting information to the
extent not otherwise restricted by confidentiality obligations.

     5.4 .  Amendment to Plan of Arrangement.  In the event a
favorable response to the No Action Request is received such that
it is not necessary for Orbital to maintain the effectiveness of
any Registration Statement covering the issuance of the Orbital
Common Shares upon exchange of the Exchangeable Shares, each of
MDA and Orbital shall take all necessary steps to amend the Plan
of Arrangement and the provisions of the Exchangeable Shares so
as to permit the Exchangeable Shares to be redeemed at the option
of the holder at any time before the fifth anniversary of the
Effective Date and so that the Automatic Redemption Date (as
defined in the Plan of Arrangement) will become the fifth
anniversary of the Effective Date.

     5.5.  Public Announcements.  Neither Orbital nor MDA shall,
nor shall either permit any of its Subsidiaries to (and each such
party shall use all commercially reasonable efforts to cause its
affiliates, directors, officers, employees, agents and
representatives not to), issue any press release, make any public
announcement or public filing or furnish any written statement to
its employees or shareholders generally concerning the
transactions contemplated by this Agreement without the consent
of the other party (which consent shall not be unreasonably
withheld), except to the extent required by applicable law, rule
or regulation or the applicable requirements of the National
Association of Securities Dealers, Inc. with respect to issuers
whose securities are quoted on the Nasdaq National Market System,
or, in the case of MDA, the applicable requirements of the
Toronto Stock Exchange or the Vancouver Stock Exchange (and in
any such case such party shall, to the extent consistent with
timely compliance with such requirement, consult with the other
party prior to making the required release, announcement, filing
or statement).

     5.6.  Notification of Certain Matters.  Between the date
hereof and the Effective Time, each party shall give prompt
notice in writing to the other parties of:  (i) any information
that indicates that any of its representations or warranties
contained herein was not true and correct as of the date hereof
or will not be true and correct at and as of the Effective Time
with the same force and effect as if made at and as of the
Effective Time (except for changes permitted or contemplated by
this Agreement); (ii) the occurrence of any event that will
result, or has a reasonable prospect of resulting, in the failure
of any condition specified in ARTICLE 6 hereof to be satisfied
and; (iii) any notice or other communication from any third party
alleging that the consent of such third party is or may be
required in connection with the transactions contemplated by this
Agreement or that such transactions otherwise may violate the
rights of or confer remedies upon such third party.

     5.7.  Other Limitations on Conduct of Business Prior to the
Effective Time.  MDA hereby covenants and agrees with Orbital
that, prior to the Effective Time: (i) unless the prior written
consent of Orbital shall have been obtained and except as
otherwise contemplated herein, it shall operate its business, and
it shall cause each of its Subsidiaries to operate its business,
only in the usual, regular and ordinary course of business
consistent with past practices; (ii) use its reasonable efforts
to preserve intact its and each of its Subsidiaries' business
organization and assets and maintain their rights and franchises;
(iii) not authorize for issuance, issue or obligate itself to
issue any shares of its capital stock or any options, warrants or
rights, or enter into any other agreements or commitments
obligating it to issue or sell shares of its capital stock or any
securities or obligations convertible into, or exchangeable for,
any shares of its capital stock, other than the issuance of MDA
Common Shares pursuant to MDA Options outstanding on July 31,
1995, to shareholders of EOS in accordance with Section 5.8 or to
former shareholders of PSC in the event certain financial
performance targets are achieved; and (iv) to take no action that
would (a) materially adversely affect the ability of Orbital or
MDA to obtain any necessary approvals of any third parties or any
governmental authorities required for the transactions
contemplated hereby or materially increase the period of time
necessary to obtain such approvals, or (b) materially adversely
affect its ability to perform its covenants and agreements under
this Agreement.

     5.8.  Exercise of Call Right.  MDA shall, on or before the
Shareholder Meeting, exercise its right to call all options to
purchase MDA Common Shares granted pursuant to the Agreement
dated as of October 31, 1991 between MDA and certain shareholders
of EOS named therein, pursuant to Sections 2.2 and 3.2 of such
agreement.

     5.9. Access to Information.  MDA shall, subject to
applicable law, afford Orbital and its accountants, counsel and
other representatives reasonable access during the period prior
to the Effective Time to (a) all of MDA's and its Subsidiaries'
financial statements, properties, books, contracts, commitments
and records, and (b) all other information concerning the
business, properties and personnel of MDA and its Subsidiaries,
as Orbital may reasonably request.  No information or knowledge
obtained after the date hereof in any investigation pursuant to
this Section 5.9 shall affect or be deemed to modify any
representation or warranty contained herein or the conditions to
the obligations of the parties to consummate the Arrangement.

     5.10.  Post Effective Date Reporting.  Orbital shall use its
best efforts to release publicly the combined financial results
of Orbital and MDA for the first full month for which such
results are available not later than thirty days after the end of
such month, provided that Orbital shall have the right not to
release such financial results, if it determines in its sole
discretion that such release would not be in the best interests
of Orbital.

     5.11.  No Action Request; Registration.  Unless the staff of
the SEC has confirmed the availability of an exemption from
registration under the Securities Act as to the issuance of the
Exchangeable Shares and/or the issuance of the Orbital Common
Shares in exchange for the Exchangeable Shares in response to the
No Action Request or Orbital has received an opinion of counsel
reasonably satisfactory to MDA to such effect, then in each case
in which no exemption is available, Orbital and Acquisition shall
cause such issuance to be registered under the Securities Act,
and shall file a Registration Statement covering such issuance
with the SEC and use all commercially reasonable efforts to cause
such registration statement to become effective as soon as
practicable and remain effective (i) in the case of  a
registration statement covering the issuance of the Exchangeable
Shares, through the Effective Date, (ii) in the case of a
Registration Statement covering the issuance of the Orbital
Common Shares in exchange for the Exchangeable Shares, throughout
the period during which the Exchangeable Shares may be exchanged
in accordance with the Plan of Arrangement and (iii) in the case
of a Registration Statement covering the issuance of the Orbital
Common Shares upon exercise of the Replacement Options,
throughout the period that the Replacement Options are
exercisable.  Orbital and Acquisition agree to file any such
required Registration Statement as soon as reasonably practicable
and, in the case of a registration statement covering the
issuance of the Orbital Common Shares, no later than one week
after the Proxy Circular is mailed to MDA's shareholders and the
holders of the MDA 1988 Options.  Orbital and Acquisition shall
use all reasonable efforts to obtain all orders required from the
applicable Canadian securities authorities to permit the issuance
of the Exchangeable Shares and the Orbital Common Shares upon
exchange of the Exchangeable Shares without registration or
qualification with or approval of or the filing of any document
including any prospectus or similar document or the taking of any
proceeding with or the obtaining of any order, ruling or consent
from any governmental or regulatory authority under any Canadian
Federal, or provincial law or regulation or pursuant to the rules
and regulations of any regulatory authority or the fulfillment of
any other legal requirement before such shares may be issued and
delivered by Acquisition or Orbital to the holder thereof or in
order that such shares may be freely traded thereafter (other
than any restrictions on transfer by reason of a holder being a
"control person" of Acquisition or Orbital for purposes of
Canadian Federal or provincial securities law or an "affiliate"
for purposes of United States Federal or state securities law).
Notwithstanding the foregoing, Acquisition shall not be obligated
to list the Exchangeable Shares on a stock exchange in Canada if
in connection with obtaining a favorable response to the No
Action Request, Orbital is advised by the SEC that the listing of
such shares will in and of itself preclude the granting of the
requested exemptions from registration requested in the No Action
Request.

     5.12.  Indemnification.  Orbital and Acquisition hereby
agree that after the Effective Date, (a) the provisions of the
Charter Documents of MDA providing for indemnification of
directors and officers shall not be amended, repealed or
otherwise modified for a period of six years from the Effective
Date in any manner that would adversely affect the rights
thereunder of directors and officers and former directors and
former officers who immediately prior to the Effective Date were
covered by such provisions, unless such modification is required
by law and (b) Orbital and Acquisition shall continue in effect
with respect to any claims arising out of conduct prior to the
Effective Date, for a period of six years following the Effective
Date, director and officer insurance policies providing coverage
of substantially the same scope as is maintained by MDA and
covering the same persons as are covered by such policies as in
effect on March 31, 1995; provided, however, Orbital may amend,
repeal or otherwise modify the Charter Documents of MDA and/or
terminate such director and officer liability insurance policies
if Orbital indemnifies and holds harmless each person covered by
the indemnification provisions of MDA's Charter Documents on the
Effective Date and MDA's director and officer liability insurance
policy as in effect on March 31, 1995 against all expenses
(including attorneys' fees), judgments, fines and amounts paid in
settlement actually and reasonably incurred by reason of the fact
that such person was a director or officer of MDA, in connection
with any threatened, pending or completed action, suit or
proceeding, whether civil, criminal, administrative or
investigative provided that, such expenses were incurred by such
person in connection with such action, suit or proceeding and
provided that such person acted in good faith and in a manner he
or she reasonably believed to be in or not opposed to MDA's best
interests and had no reasonable cause to believe his or her
conduct was unlawful.

     5.13.  Tax Filings.  Orbital covenants to cause Acquisition
after the Effective Date to agree with each person who was a
holder of MDA Common Shares, or the holder of shares of a holding
company referred to in Section 2.1.2 hereof, immediately prior to
the Effective Time who wishes to do so to jointly make an
election under subsection 85(1) or 85(2) of the Income Tax Act
(Canada) in the prescribed form in respect of the exchange of the
MDA Common Shares or such holder's holding company shares, as the
case may be, and to specify therein as the holder's proceeds of
disposition and Acquisition's cost of the MDA Common Shares or
holding company shares such amount as is determined by the holder
, subject to the several limitations of subsection 85(1) or
85(2), as the case may be, of the Income Tax Act (Canada).
Acquisition shall complete the election form within 30 days of
receipt from such persons of an election form fully completed
other than with respect to information relating to Acquisition.

     5.14.  Further Assurances.  Subject to the terms and
conditions herein provided, and subject to its fiduciary
obligations under law, each of the parties agrees to use all
reasonable efforts to take, or cause to be taken, all actions and
to do, or cause to be done, all things necessary, proper or
advisable under applicable laws and regulations to consummate and
make effective the Arrangement and the other transactions
contemplated by this Agreement, including without limitation the
taking of all reasonable actions necessary to satisfy each
condition precedent set forth in ARTICLE 6, to comply promptly
with all legal requirements that may be imposed on any of them
with respect to the Arrangement or to procure any consent,
approval, order or authorization of, or any exemption by, any
governmental entity, or other third party, required to be
obtained or made in connection with the Arrangement or the taking
of any action contemplated thereby or by this Agreement.



                         ARTICLE 6
                    CONDITIONS PRECEDENT

     6.1.  Conditions Precedent to MDA's Obligation to Effect the
Arrangement.  The obligations of MDA to effect the Arrangement
and other transactions contemplated by this Agreement shall be
subject to the satisfaction, prior to or substantially
contemporaneously with the Effective Time, of the following
conditions, compliance with which, or the occurrence of which,
may be waived in whole or in part by MDA in writing.

          6.1.1.  Representations; Covenants; Certificate.  The
     representations and warranties of Orbital contained in
     ARTICLE 4 hereof (except for clause (i) of the first
     sentence of Section 4.3 to the extent it refers to the
     number of issued and outstanding shares of Orbital Common
     Shares and except that Orbital shall have authorized a newly
     created class of preferred stock, one share of which shall
     be issued to the Trustee on the Effective Date pursuant to
     the Voting Trust Agreement) shall be true in all material
     respects as of the date of this Agreement and as of the
     Effective Date with the same effect as though made as of the
     Effective Time; Orbital shall in all material respects have
     performed all obligations and complied with all covenants
     required by this Agreement to be performed or complied with
     by it prior to the Effective Time; and Orbital shall have
     delivered to MDA a certificate, dated the Effective Date and
     signed by its President or a Vice President, to each such
     effect.

          6.1.2  Opinion of Counsel for Orbital.  MDA shall have
     received from Ropes & Gray, counsel for Orbital, a legal
     opinion, dated the Effective Date, with respect to legal
     matters related to this Agreement and the transactions
     contemplated hereby and in form and substance reasonably
     acceptable to MDA.

          6.1.3.  Price of Orbital Stock.  The Average Closing
     Price shall be equal to or greater  than U.S.$12.775.

     6.2.  Conditions Precedent to Obligations of Orbital.  The
obligations of Orbital to effect the Arrangement and the other
transactions contemplated by this Agreement shall be subject to
the satisfaction, prior to or substantially contemporaneously
with the Effective Time, of the following conditions, compliance
with which, or the occurrence of which, may be waived in whole or
in part by Orbital in writing:

          6.2.1.  Representations; Covenants; Certificate.  The
     representations and warranties of MDA contained in ARTICLE 3
     hereof shall be true in all material respects as of the date
     of this Agreement (except for clause (i) of the first
     sentence of Section 3.3 to the extent the number of issued
     and outstanding MDA Common Shares has increased solely
     because of the exercise of any of the MDA Options and the
     issuance of MDA Common Shares required by Section 5.8) and
     the Effective Time with the same effect as though made as of
     the Effective Time; MDA shall in all material respects have
     performed all obligations and complied with all covenants
     required by this Agreement to be performed or complied with
     by it prior to the Effective Time; and MDA shall have
     delivered to Orbital a certificate, dated the Effective Date
     and signed by its President or a Vice President, to each
     such effect.

          6.2.2.  Opinion of Counsel for MDA.  Orbital shall have
     received from Farris, Vaughan, Wills & Murphy, counsel for
     MDA, a legal opinion, dated the Effective Date, with respect
     to legal matters related to this Agreement and the
     transactions contemplated hereby and in form and substance
     reasonably acceptable to Orbital.

          6.2.3.  MDA Rights Plan.  The Board of Directors of MDA
     shall have waived the provisions of the Amended and Restated
     Shareholder Protection Rights Plan Agreement, dated as of
     August 27, 1992 as amended through the date hereof, between
     MDA and Montreal Trust Company of Canada, pursuant to
     Section 5.1(b) of such agreement, such that the Arrangement
     and the other transactions contemplated hereby shall be
     wholly exempt from such agreement.

          6.2.4.  Affiliate Agreements.  Orbital shall have
     received executed affiliate agreements (the "Affiliate
     Agreements") (i) in substantially the form attached as
     Exhibit 6.2.4(a), from each director, the President, the
     Group Managers and the Controller of MDA, all holders of ten
     percent or more of the MDA Common Shares issued and
     outstanding on the date hereof (other than Spar Aerospace
     Limited) and all entities controlled by any of the foregoing
     (including without limitation, Ventures West) and (ii) in
     substantially the form attached as Exhibit 6.2.4(b) from
     Spar Aerospace Limited (together with those referenced in
     clause (i), the "Affiliates").

          6.2.5.  Employment Agreements.  MDA shall have entered
     into an Employment Agreement and a Change of Control
     Agreement in substantially the form attached as Exhibit
     6.2.5 with the President, Chairman and each Group Manager of
     MDA, and copies of such agreements shall have been delivered
     to Orbital.

          6.2.6.  Appraisal Rights.  The holders of MDA Common
     Shares or MDA 1988 Options in the aggregate entitled to
     receive no more than 10% of the sum of the Orbital Common
     Shares issuable pursuant to the Plan of Arrangement and the
     Orbital Common Shares reserved for issuance upon the
     exercise of Replacement Options shall have dissented and be
     entitled to be paid the fair value of their shares or
     options, as the case may be, pursuant to the Plan of
     Arrangement.

          6.2.7.  Pooling of Interests Accounting Treatment.
     Orbital shall have been advised in writing by KPMG Peat
     Marwick, its independent public accountants that in their
     opinion the transactions contemplated herein meet the
     requirements for pooling-of-interests treatment under U.S.
     GAAP as set forth in Opinion No. 16, as amended, of the
     Accounting Principles Board of the American Institute of
     Certified Public Accountants.

          6.2.8  Required Consents.  MDA and Orbital shall have
     received all necessary consents, waivers or amendments
     listed by MDA and Orbital in Sections 3.2 and 4.2 of the MDA
     Disclosure Schedule and Orbital Disclosure Schedule,
     respectively, as being required (other than the consent of
     EarthWatch). The representation made by MDA and Orbital in
     the first sentence of Section 3.2 and 4.2, respectively,
     hereof construed without reference to any exceptions noted
     in the MDA or Orbital Disclosure Schedule (other than MDA's
     failure to obtain the consent of EarthWatch) shall be true
     and correct.

          6.2.9.  Price of Orbital Stock.  The Average Closing
     Price shall be equal to or less than U.S.$25.00.

     6.3.  Conditions Precedent to the Obligations of Each Party.
The obligations of the parties to effect the Arrangement and the
other transactions contemplated by this Agreement shall be
subject to the satisfaction prior to or substantially
contemporaneously with the Effective Time of the following
additional conditions, compliance with which, or the occurrence
of which, may be waived in whole or in part by a writing executed
by each of MDA and Orbital:

          6.3.1.  Shareholder Approval.  The holders of the
     requisite number, as specified by the Court in its Interim
     Order, of outstanding shares of MDA Common Shares and the
     MDA 1988 Options shall have duly approved the Plan of
     Arrangement and the transactions contemplated thereby and
     hereby, all in accordance with the requirements of the CBCA
     and such Interim Order.

          6.3.2.  Governmental and Court Approvals.  Consents
     legally required from any governmental authority with
     respect to the consummation of the Arrangement and the
     transactions contemplated by this Agreement, including the
     Final Order shall have been filed, occurred, or been
     obtained, other than such consents, the failure to obtain
     which would not have any MDA or Orbital Material Adverse
     Effect or any material adverse effect on the consummation of
     the Arrangement.

          6.3.3.  No Action Request/Registration Statement.  The
     staff of the SEC shall have confirmed the availability of an
     exemption from registration to the issuance of the
     Exchangeable Shares, Orbital Common Shares and Replacement
     Options pursuant to the Arrangement in response to the No
     Action Request or Orbital shall have received an opinion of
     counsel reasonably satisfactory to it and MDA to such effect
     or a Registration Statement with respect to such issuances
     shall have become effective under the Securities Act and
     shall not be the subject of any stop order or proceedings
     seeking a stop order and the Proxy Circular shall not be at
     the Effective Time subject to any proceedings commenced or
     threatened by the SEC or any Canadian or provincial
     securities authority.  Canadian provincial securities
     regulators in those provinces of Canada considered necessary
     by Canadian counsel to MDA and Canadian counsel to Orbital
     shall have granted rulings or orders, satisfactory to both
     of such counsel acting reasonably, so that the registration
     and prospectus provisions of applicable Canadian securities
     laws will not be applicable to any of the issuance of
     securities contemplated by the Arrangement and such
     securities (other than the Class B Preferred Shares to be
     issued to Canadian Imperial Bank of Commerce) will be freely
     tradable by holders resident in such provinces.

          6.3.4.  Injunctions.  No temporary restraining order,
     preliminary or permanent injunction or other order by any
     Canadian or United States Federal or provincial or state
     court or governmental body prohibiting the consummation of
     the transactions contemplated by this Agreement shall have
     been issued and shall not have expired or been withdrawn or
     reversed and there shall be no pendent or threatened
     litigation or other proceeding seeking to prohibit or impose
     any material limitations on the consummation of such
     transactions.

          6.3.5.  Nasdaq/NMS Listing Approval.  Orbital shall
     have filed with the National Association of Securities
     Dealers, Inc. a notice of listing of additional shares for
     the Orbital Common Shares issuable pursuant to the
     Arrangement.


                         ARTICLE 7
                       MISCELLANEOUS

     7.1.  Termination.  Anything herein or elsewhere to the
contrary notwithstanding, this Agreement may be terminated and
abandoned at any time before the Effective Time, whether before
or after adoption and approval of the Arrangement by the
shareholders of MDA and the holders of the MDA 1988 Options as
herein provided:

     (a)  By the mutual consent of Orbital and MDA;

     (b) By either MDA or Orbital, if (i) there has been a
material breach on the part of the other party of any
representation, warranty, covenant or agreement contained herein
that cannot be or has not been cured within ten days after
written notice of such breach to the breaching party or (ii)
MDA's shareholders or the holders of the MDA 1988 Options fail to
approve the Plan of Arrangement, provided, however such failure
is not due to MDA's breach of its covenants contained in Article
5;

     (c) By Orbital, if the Board of Directors of MDA shall have
withdrawn or modified in a manner adverse to Orbital its support
of the transaction, or shall fail to affirm such support upon the
request of Orbital;

     (d) By MDA, if MDA shall have received a bona fide offer to
consummate an Acquisition Transaction for consideration per MDA
Common Share having a fair market value of at least U.S.$5.95
(based on the currency exchange rate on the date the offer is
made);

     (e) By MDA on or before the date on which the Proxy Circular
is mailed to MDA shareholders and holders of the MDA 1988
Options, if by such date Teleglobe Mobile Partners ("Teleglobe
Mobile") has not committed to increase its investment in ORBCOMM
Development Partners, L.P. on substantially the terms reflected
in the Master Agreement dated June 30, 1993 between Orbital,
Orbital Communications Corporation, Teleglobe, Inc. and Teleglobe
Mobile or on such other terms as do not have an Orbital Material
Adverse Effect.
     
     (f)  By the Board of Directors of MDA, if the Effective Time
shall not have occurred by December 31, 1995 other than as a
result of the failure of MDA to satisfy its obligations
hereunder.

     (g)  By the Board of Directors of Orbital, if the Effective
Time shall not have occurred by December 31, 1995 other than as a
result of the failure of Orbital to satisfy its obligations
hereunder.
     
     (h)  By Orbital, if Spar has not executed the voting
agreement and affiliate agreements, in substantially the forms
attached as Exhibits 7.1(h) and 6.2.4(b), respectively, by
September 6, 1995.

In the event of both (i) a termination by EarthWatch, in whole or
in part, of its agreement with MDA pursuant to which MDA is to
build a portion of EarthWatch's image data archival and
processing facility, which termination was solely as a result of
the public announcement of MDA's and Orbital's agreement to
consummate the Arrangement, and (ii) a termination of this
Agreement because of (a) the failure to satisfy the conditions
precedent to Closing set forth in Section 6.1.3 or Section 6.2.7,
or (b) either party has exercised its right to terminate pursuant
to paragraph (f) or (g) of this Section 7.1; then Orbital shall
(x) use all commercially reasonable efforts to notify MDA as soon
as practicable at any time Orbital (or any entity that was a
Subsidiary of Orbital on July 31, 1995) has determined to solicit
third party bids for the construction of satellite ground
stations and (y) afford MDA the opportunity to participate in
such bidding; provided, however, such actions would not be
required if to do so would result in the breach of a currently
existing contract or if otherwise prohibited by any applicable
rules or regulations, including, but not limited to, rules or
regulations governing bidding procedures with respect to
Government Contracts and export controls; and provided further
that this obligation to provide notice and afford MDA an
opportunity to bid shall terminate three years from the earlier
of (A) the date of termination of such EarthWatch agreement and
(B) December 31, 1995.  In the event of termination and
abandonment under this Section 7.1, this Agreement shall
forthwith become null and void and there shall be no liability on
the part of any of MDA, Orbital or Acquisition or any of their
respective officers and directors; provided, however, that the
provisions of the immediately preceding sentence, Section 7.3 and
Section 7.4 hereof shall survive any termination of this
Agreement as provided therein and in the event of a termination
pursuant to Section 7.1(b)(i) the breaching party shall be liable
for all out-of-pocket costs and expenses incurred in connection
with the transactions contemplated hereby.

     7.2.  Amendments and Supplements.  At any time before or
after approval and adoption of this Agreement and the Plan of
Arrangement by the shareholders of MDA and the holders of the MDA
1988 Options and prior to the Effective Time, this Agreement and
the Plan of Arrangement may be amended or supplemented (including
without limitation, any amendment to the Plan of Arrangement
required to be made pursuant to Section 5.4 hereof) by a written
instrument signed by MDA, Orbital and approved by their
respective Boards of Directors, except that, after the
shareholders of MDA and the holders of the MDA 1988 Options shall
have approved the Plan of Arrangement, there shall be no
amendment that (i) changes the consideration into which the MDA
Common Shares or the MDA Options are entitled to be converted
upon consummation of the Arrangement as provided in the Plan of
Arrangement or (ii)  otherwise would require the approval of the
shareholders of MDA or the holders of the 1988 MDA Options in
accordance with the CBCA.

     7.3.  Survival of Representations, Warranties and
Agreements.  The respective representations, warranties and
agreements of MDA, Orbital and Acquisition contained in Articles
3 and 4 hereof and except with respect to Sections 5.10, 5.11
5.12 and 5.13, their respective agreements contained in Article 5
hereof shall expire with, and be terminated by, the consummation
of the Arrangement, and neither Orbital nor MDA shall have any
liability whatsoever with respect to such representations,
warranties or agreements after the Effective Time.

     7.4  Other Payments.  MDA covenants and agrees that if MDA
terminates this Agreement pursuant to Section 7.1(d) hereof and
the transaction that gives rise to such termination is completed,
then MDA shall pay to Orbital a fee of $750,000.

     7.5.  Expenses.  Subject to the provisions of Section 7.1
and 7.4, whether or not the Arrangement is consummated, all costs
and expenses incurred in connection with this Agreement and the
transactions contemplated hereby shall be paid by the party
incurring such expenses.

     7.6.  Governing Law.  This Agreement shall be governed by
and construed in accordance with the domestic substantive laws of
the province of British Columbia without giving effect to any
choice or conflict of laws rule or provision that would cause the
application of the domestic substantive laws of any other
jurisdiction.

     7.7.  Notice.  All notices and other communications required
or permitted hereunder shall be in writing (including any
facsimile transmission or similar writing), and shall be sent
either by telecopy, hand delivery, or reputable overnight
courier, addressed as follows or to such other address or
addresses of which the respective party shall have notified the
other party.  Each such notice or other communication shall be
effective (i) if given by telecopy, when such telecopy is
transmitted and the appropriate answerback is received, (ii) if
given by reputable overnight courier, one business day after
being delivered to such courier or (iii) if given by any other
means, when received at the address specified in this Section.

     To Orbital or Acquisition:

          21700 Atlantic Boulevard
          Dulles, Virginia  20166
          Telecopier:  (703) 406-5572
          Attention:  General Counsel

     With a copy to:

          Ropes & Gray
          One International Place
          Boston, Massachusetts  02110
          Telecopier:  (617) 951-7050
          Attention:  Daniel S. Evans, Esq.

     To MDA:

          13800 Commerce Parkway
          Richmond, British Columbia V6V 2J3
          Canada
          Telecopier:  (604) 273-9830
          Attention:  President

     With a copy to:

          Farris, Vaughan, Wells & Murphy
          26th Floor, 700 West Georgia Street
          Vancouver, British Columbia V7Y 1B3
          Canada
          Telecopier:  (604) 661-9349
          Attention:  Elizabeth J. Harrison, Q.C.

     7.8a.  Entire Agreement, Assignability, Etc.  This Agreement
(including the Schedules and Exhibits attached hereto) and
together with the confidentiality agreement dated June 23, 1995
and paragraph 9 of the letter of intent dated July 31, 1995, each
entered into by Orbital and MDA, (i) constitutes the entire
agreement, and supersedes all other prior agreements and
understandings, both written and oral, among the parties, or any
of them, with respect to the Arrangement, (ii) is not intended to
confer upon any person other than the parties hereto any rights
or remedies hereunder and (iii) shall not be assignable by
operation of law or otherwise.

     7.9.  Counterparts.  This Agreement may be executed in any
number of counterparts, each of which shall be deemed an original
but all of which together shall constitute but one and the same
instrument.

     IN WITNESS WHEREOF, the parties have duly executed this
Agreement as of the date first above written.


Attest:                            ORBITAL SCIENCES CORPORATION


/s/ Susan Herlick                  By: /s/ Carlton B. Crenshaw
Name:  Susan Herlick                  Name:  Carlton B. Crenshaw
Title:  Assistant Secretary           Title:  Senior Vice President/Finance
                                               and Administration


Attest:                            3173623 CANADA INC.


/s/ Susan Herlick                  By /s/ Carlton B. Crenshaw
Name:  Susan Herlick                  Name: Carlton B. Crenshaw
Title:  Assistant Secretary           Title:   Vice President


Attest:                            MACDONALD, DETTWILER AND
                                     ASSOCIATES LTD.


/s/ Robert B. Wallis               By /s/ Daniel E. Friedmann
Name: Robert B. Wallis                Name: Daniel E. Friedmann
Title:  Secretary                     Title: President and Chief Executive
                                            Officer



                      PLAN OF ARRANGEMENT
                       UNDER SECTION 192
            OF THE CANADA BUSINESS CORPORATIONS ACT


                           ARTICLE 1

                         INTERPRETATION

1.1  Definitions

           In  this Plan of Arrangement unless there is something
in  the  subject  matter or context inconsistent  therewith,  the
following terms shall have the respective meanings set out  below
and grammatical variations of such terms shall have corresponding
meanings:

      (a)   "Affiliate"  of  any person means  any  other  person
directly  or  indirectly  controlling, controlled  by,  or  under
common  control  with,  that person.  For the  purposes  of  this
definition, "control" (including, with correlative meanings,  the
terms  "controlling", "controlled by" and "under  common  control
with"), as applied to any person, means the possession by another
person,  directly or indirectly, of the power to direct or  cause
the  direction  of  the  management and policies  of  that  first
mentioned  person,  whether  through  the  ownership  of   voting
securities, by contract or otherwise;

      (b)  "Arrangement" means the arrangement under section  192
of the CBCA on the terms and subject to the conditions set out in
this  Plan of Arrangement, subject to any amendments thereto made
in  accordance with section 6.1 or made at the direction  of  the
Court in the Final Order;

      (c)  "Automatic Redemption Date" means November     , 2000,
unless  such date shall be accelerated at any time to a specified
earlier  date  by the Board of Directors upon at  least  75  days
prior  written  notice to the registered holders of  Exchangeable
Shares, in which case the Automatic Redemption Date shall be such
earlier date; provided, however, that the Board of Directors  may
so  accelerate the Automatic Redemption Date only at such time as
there are outstanding fewer than 400,000 Exchangeable Shares held
by holders other than Orbital and its Affiliates;

     (d)  "Average Closing Price" means the average closing sales
price of Orbital Common Shares for the 20 trading days ending  on
the  date  four  trading  days prior to the  Effective  Date,  as
reported on NASDAQ;

      (e)   "Board of Directors" means the board of directors  of
the Corporation;

      (f)  "Business Day" means any day other than a Saturday,  a
Sunday or a day when banks are not open for business in either or
both  of  the  Commonwealth of Virginia, and  Vancouver,  British
Columbia;

      (g)   "Canadian Dollar Equivalent" means in respect  of  an
amount  expressed  in a foreign currency (the  "Foreign  Currency
Amount") at any date the product obtained by multiplying (a)  the
Foreign  Currency  Amount by (b) the noon spot exchange  rate  on
such date for such foreign currency expressed in Canadian dollars
as  reported  by  the Bank of Canada or, in the event  such  spot
exchange  rate is not available, such exchange rate on such  date
for such foreign currency expressed in Canadian dollars as may be
deemed  by  the  Board  of Directors to be appropriate  for  such
purpose;

      (h)   "Capital  Reorganization" has  the  meaning  ascribed
thereto in section 5.7;

      (i)  "CBCA" means the Canada Business Corporations Act,  as
amended from time to time;

      (j)  "Class B Preferred Shares" means the Class B Preferred
Shares   of   the  Corporation  having  the  rights,  privileges,
restrictions and conditions set out in Appendix A annexed hereto.

      (k)   "Combination Agreement" means the  agreement  by  and
among  Orbital, the Corporation and MDA, dated as of  August  31,
1995,  as  the  same may be amended and restated, providing  for,
among other things, the Arrangement;

      (l)  "Corporation" means 3173623 Canada Inc., a corporation
existing under the CBCA;

     (m)  "Court" means the Supreme Court of British Columbia;

      (n)  "Current Market Price" means, in respect of an Orbital
Common  Share on any date, the Canadian Dollar Equivalent of  the
closing  sale price of Orbital Common Shares on such day (or,  if
no  trades of Orbital Common Shares occurred on such day, on  the
last  trading  day  prior thereto on which such trades  occurred)
reported on NASDAQ, or, if the Orbital Common Shares are not then
quoted  on  NASDAQ,  on  such other stock exchange  or  automated
quotation system on which the Orbital Common Shares are listed or
quoted,  as the case may be, as may be selected by the  Board  of
Directors  for such purpose; provided, however, that  if  in  the
opinion  of  the  Board of Directors the public  distribution  or
trading activity of Orbital Common Shares during such period does
not  create  a market that reflects the fair market value  of  an
Orbital Common Share, then the Current Market Price of an Orbital
Common Share shall be determined by the Board of Directors  based
upon  the advice of such qualified independent financial advisors
as  the  Board  of  Directors may deem  to  be  appropriate,  and
provided   further   that   any  such   selection,   opinion   or
determination  by the Board of Directors shall be conclusive  and
binding;

     (o)  "Current Orbital Common Share Equivalent" means, on any
date,  the equivalent as at such date of one Orbital Common Share
as  at  the  Effective  Date, expressed to four  decimal  places,
determined  by  applying  on  a cumulative  basis  the  following
adjustments,   to  the  extent  applicable  by  reason   of   any
transactions  occurring  in  respect  of  Orbital  Common  Shares
between  the  Effective Date and such date, the  Current  Orbital
Common Share Equivalent as at the Effective Date being 1.0000:

                           (i)         if   Orbital   shall   (A)
               subdivide, redivide or change its then outstanding
               Orbital  Common  Shares into a greater  number  of
               Orbital  Common Shares, unless the Corporation  is
               permitted under applicable law without a  vote  of
               its shareholders to make, and shall simultaneously
               make,  the  same  or  an  economically  equivalent
               change   to   the   rights  of  the   holders   of
               Exchangeable   Shares,   (B)   reduce,    combine,
               consolidate or change its then outstanding Orbital
               Common  Shares  into a lesser  number  of  Orbital
               Common Shares, unless the Corporation is permitted
               under  applicable  law  without  a  vote  of   its
               shareholders  to  make, and  shall  simultaneously
               make,  the  same  or  an  economically  equivalent
               change   to   the   rights  of  the   holders   of
               Exchangeable  Shares, or (C) issue Orbital  Common
               Shares  (or securities exchangeable or convertible
               into Orbital Common Shares) to the holders of  all
               or  substantially  all  of  its  then  outstanding
               Orbital Common Shares by way of stock dividend  or
               other  distribution  (other  than  to  holders  of
               Orbital  Common Shares who exercise an  option  to
               receive stock dividends in lieu of receiving  cash
               dividends),  unless the Corporation  is  permitted
               under  applicable  law  without  a  vote  of   its
               shareholders  to  issue or distribute,  and  shall
               simultaneously  issue  and distribute,  equivalent
               numbers   of  Orbital  Common  Shares   or   other
               securities  (adjusted if necessary  in  accordance
               with the Current Orbital Common Share Equivalent),
               or  the  economic equivalent on a per share basis,
               to  the holders of the Exchangeable Shares (any of
               such events being herein called an "Orbital Common
               Share Reorganization"), the Current Orbital Common
               Share   Equivalent  shall  be  adjusted  effective
               immediately  after the record date  at  which  the
               holders  of  Orbital Common Shares are  determined
               for  the  purpose  of  the  Orbital  Common  Share
               Reorganization by multiplying the Current  Orbital
               Common  Share Equivalent in effect on such  record
               date by the quotient obtained when:

                                    (I)   the  number of  Orbital
                    Common    Shares   outstanding   after    the
                    completion  of  such  Orbital  Common   Share
                    Reorganization (but before giving  effect  to
                    the issue of any Orbital Common Shares issued
                    after such record date otherwise than as part
                    of  such Orbital Common Share Reorganization)
                    including,   in  the  case  where  securities
                    exchangeable  or  convertible  into   Orbital
                    Common Shares are distributed, the number  of
                    Orbital  Common Shares that would  have  been
                    outstanding   had   such   securities    been
                    exchanged  for  or  converted  into   Orbital
                    Common Shares on such record date,

               is divided by

                                    (II)  the  number of  Orbital
                    Common Shares outstanding on such record date
                    before  giving  effect to the Orbital  Common
                    Share Reorganization;

                     (ii)            if at any time Orbital shall
               fix  a  record  date for the issuance  of  rights,
               options  or  warrants to the  holders  of  all  or
               substantially  all  of the Orbital  Common  Shares
               entitling  them  to subscribe for or  to  purchase
               Orbital  Common Shares (or securities  of  Orbital
               convertible into Orbital Common Shares) at a price
               per  Orbital Common Share (or having a  conversion
               price  per Orbital Common Share) of less than  the
               Pre-Dilution  Market Price on  such  record  date,
               unless   the   Corporation  is   permitted   under
               applicable  law without a vote of its shareholders
               to   issue,   and   shall  simultaneously   issue,
               equivalent  numbers  of such  rights,  options  or
               warrants, adjusted if necessary in accordance with
               the  Current  Orbital Common Share  Equivalent  at
               such  record  date,  or  the  economic  equivalent
               thereof  on  a per share basis, to the holders  of
               Exchangeable  Shares (any such event being  herein
               referred  to  as  a "Rights Offering"),  then  the
               Current  Orbital Common Share Equivalent  then  in
               effect  shall be adjusted immediately  after  such
               record  date  by  multiplying the Current  Orbital
               Common  Share Equivalent in effect on such  record
               date by the quotient obtained when:

                                          (A)   the  sum  of  the
                    number  of  Orbital Common Shares outstanding
                    on   such  record  date  and  the  number  of
                    additional Orbital Common Shares offered  for
                    subscription  or  purchase under  the  Rights
                    Offering  (or  the number of  Orbital  Common
                    Shares  into which the securities so  offered
                    are convertible)

             is divided by

                                          (B)   the  sum  of  the
                    number  of  Orbital Common Shares outstanding
                    on such record date and the number determined
                    by  dividing the aggregate price of the total
                    number  of  additional Orbital Common  Shares
                    offered  for  subscription or purchase  under
                    the   Rights   Offering  (or  the   aggregate
                    conversion    price   of   the    convertible
                    securities  so  offered) by the  Pre-Dilution
                    Market Price on such record date.

          Any  Orbital  Common Share owned by  or  held  for  the
          account   of  Orbital  shall  be  deemed  not   to   be
          outstanding  for  the purpose of any such  computation.
          If  such rights, options or warrants are not so  issued
          or  if, at the date of expiry of the rights, options or
          warrants subject to the Rights Offering, less than  all
          the  rights,  options or warrants have been  exercised,
          then  the Current Orbital Common Share Equivalent shall
          be  readjusted effective immediately after the date  of
          expiry  to  the Current Orbital Common Share Equivalent
          which would have been in effect if such record date had
          not  been fixed or to the Current Orbital Common  Share
          Equivalent which would then be in effect on the date of
          expiry  if the only rights, options or warrants  issued
          had been those that were exercised, as the case may be;

                          (iii)     if Orbital shall fix a record
               date for the making of a distribution (including a
               distribution  by  way of stock  dividend)  to  the
               holders   of   all   or  substantially   all   its
               outstanding Orbital Common Shares of

                                        (A)  shares of Orbital of
                    any  class  other than Orbital Common  Shares
                    (or  shares  convertible into Orbital  Common
                    Shares referred to in (i) (C) above),

                                         (B)  rights, options  or
                    warrants (excluding a Rights Offering),

                                         (C)   evidences  of  its
                    indebtedness      (excluding     indebtedness
                    convertible   into  Orbital   Common   Shares
                    referred to in (i) (C) above) or

                                         (D)   any  other  assets
                    (other than any of the distributions referred
                    to  in (A), (B) or (C), dividends paid in the
                    ordinary  course or an Orbital  Common  Share
                    Reorganization)

                                                  unless      the
                    Corporation is permitted under applicable law
                    without   a  vote  of  its  shareholders   to
                    distribute,    and    shall    simultaneously
                    distribute,  the  same  number   of   shares,
                    rights,  options  or warrants,  evidences  of
                    indebtedness or other assets, as the case may
                    be,  adjusted if necessary in accordance with
                    the  Current Orbital Common Share  Equivalent
                    as  at  such  record date,  or  the  economic
                    equivalent thereof on a per share  basis,  to
                    the  holders of Exchangeable Shares (any such
                    event  being herein referred to as a "Special
                    Distribution") then, in each such  case,  the
                    Current Orbital Common Share Equivalent shall
                    be  adjusted effective immediately after  the
                    record  date at which the holders of  Orbital
                    Common Shares are determined for the purposes
                    of  the  Special Distribution by  multiplying
                    the  Current Orbital Common Share  Equivalent
                    in effect on such record date by the quotient
                    obtained when:

                                               (I)   the  product
                         obtained  when  the  number  of  Orbital
                         Common  Shares outstanding on the record
                         date  is  multiplied by the Pre-Dilution
                         Market Price on such date,

               is divided by

                                    (II)  the difference obtained
                    when  the amount by which the aggregate  fair
                    market  value (as determined by the Board  of
                    Directors,  which  determination   shall   be
                    conclusive)  of the shares, rights,  options,
                    warrants,   evidences  of   indebtedness   or
                    assets,  as  the case may be, distributed  in
                    the  Special  Distribution exceeds  the  fair
                    market  value (as determined by the Board  of
                    Directors,  which  determination   shall   be
                    conclusive)  of  the consideration,  if  any,
                    received  therefor by Orbital, is  subtracted
                    from the product obtained when the number  of
                    Orbital  Common  Shares  outstanding  on  the
                    record date is multiplied by the Pre-Dilution
                    Market Price on such date,

                                         provided  that  no  such
               adjustment  shall be made if the  result  of  such
               adjustment  would  be  to  decrease  the   Current
               Orbital   Common   Share  Equivalent   in   effect
               immediately before such record date.  Any  Orbital
               Common  Share owned by or held for the account  of
               Orbital shall be deemed not to be outstanding  for
               the   purpose  of  any  such  computation.    Such
               adjustment  shall  be  made successively  whenever
               such  a record date is fixed.  To the extent  that
               such  distribution  is not so  made,  the  Current
               Orbital   Common   Share   Equivalent   shall   be
               readjusted  effective immediately to  the  Current
               Orbital  Common Share Equivalent which would  then
               be  in  effect based upon such shares  or  rights,
               options  or  warrants or evidences of indebtedness
               or assets actually distributed;

      (p)   "Depositary"  means Montreal  Trust  Company  at  its
principal  offices  in Vancouver, British Columbia  and  Toronto,
Ontario;

       (q)   "Effective  Date"  means  the  date  shown  on   the
certificate of arrangement issued by the Director under the  CBCA
giving effect to the Arrangement;

      (r)   "Effective  Time" means 12:01 a.m. on  the  Effective
Date;

      (s)  "Exchange Ratio" is equal to U.S. $5.41 divided by the
Average Closing Price, provided that in no event shall it be less
than 0.2705 or greater than 0.3607;

      (t)   "Exchangeable  Share Provisions"  means  the  rights,
privileges,   restrictions  and  conditions  attaching   to   the
Exchangeable Shares, which are set forth in Appendix A hereto;

     (u)  "Exchangeable Shares" means the Exchangeable Non-Voting
Shares   of   the  Corporation  having  the  rights,  privileges,
restrictions  and conditions set forth in the Exchangeable  Share
Provisions;

      (v)   "Final  Order"  means the final order  of  the  Court
approving  the  Arrangement as such order may be amended  by  the
Court at any time prior to the Effective Time;

      (w)  "Lien" means any lien, pledge, adverse claim, security
interest, mortgage, claim, charge or encumbrance;

      (x)   "Liquidation  Call Purchase Price"  has  the  meaning
ascribed thereto in subsection 5.2(a);

      (y)   "Liquidation  Call Right" has  the  meaning  ascribed
thereto in subsection 5.2(a);

      (z)  "Liquidation Date" has the meaning ascribed thereto in
section 4.1 of the Exchangeable Share Provisions;

     (aa) "MDA" means MacDonald, Dettwiler and Associates Ltd., a
corporation existing under the CBCA;

      (bb)  "MDA  Common Shares" means the common shares  in  the
capital  of  MDA,  including  all  rights  associated  therewith,
including  without  limitation all rights  associated  with  such
common shares pursuant to the Shareholder Protection Rights  Plan
Agreement  dated as of August 27, 1992 between MDA  and  Montreal
Trust Company of Canada, as Rights Agent, as amended from time to
time;

      (cc) "MDA 1988 Options" has the meaning ascribed thereto in
subsection 2.1(l);

     (dd) "Meeting" means the Special Meeting of the shareholders
of MDA (voting together as one class) and the holders of MDA 1988
Options  (voting separately from the shareholders  of  MDA  as  a
second class) to be held to consider the Arrangement;

     (ee) "NASDAQ" means the NASDAQ National Market System;

      (ff)  "Options" means options, whether vested or  unvested,
granted by MDA prior to the Effective Date to purchase MDA Common
Shares  pursuant  to  the  1988 Key Employee  Share  Option  Plan
("KESOP  88"), the 1988 Employee Share Option Plan  ("ESOP  88"),
the  Key  Employee Share Option Plan and the Amended and Restated
Key Employee Share Option Plan;

       (gg)  "Orbital"  means  Orbital  Sciences  Corporation,  a
corporation existing under the laws of the State of Delaware;

      (hh) "Orbital Call Notice" has the meaning ascribed thereto
in subsection 5.1(b);

      (ii)  "Orbital Common Share Reorganization" has the meaning
ascribed thereto in subsection 1.1(o);

      (jj)  "Orbital Common Shares" means the common  stock,  par
value $.01 per share, of Orbital;

      (kk)  "Pre-Dilution Market Price" means, in respect  of  an
Orbital  Common Share on any date, the Canadian Dollar Equivalent
of  the  average of the closing sale prices as reported on NASDAQ
of  such  shares during a period of 20 consecutive  trading  days
ending  on the fourth trading day prior to such date, or, if  the
Orbital  Common  Shares are not then quoted on  NASDAQ,  on  such
other  stock exchange or automated quotation system on which  the
Orbital Common Shares are listed or quoted as may be selected  by
the  Board of Directors for such purpose; provided, however, that
if   in  the  opinion  of  the  Board  of  Directors  the  public
distribution or trading activity of Orbital Common Shares  during
such  period  does  not create a market that  reflects  the  fair
market  value  of an Orbital Common Share, then the  Pre-Dilution
Market  Price  of an Orbital Common Share shall be determined  by
the  Board  of Directors based upon the advice of such  qualified
independent financial advisors as the Board of Directors may deem
to  be appropriate, and provided further that any such selection,
opinion  or  determination by the Board  of  Directors  shall  be
conclusive and binding;

     (ll) "Qualifying Holdco" means a corporation that shall have
become  a party to this Plan of Arrangement prior to the date  of
the  Meeting  pursuant to subsection 6.1(b) hereof  and  that  is
listed in Appendix B;

      (mm)  "Redemption  Call  Purchase Price"  has  the  meaning
ascribed thereto in subsection 5.3(a);

      (nn)  "Redemption  Call  Right" has  the  meaning  ascribed
thereto in subsection 5.3(a);

      (oo) "Retracted Shares" has the meaning ascribed thereto in
section 5.1 of the Exchangeable Share Provisions;

      (pp)  "Retraction  Call  Purchase Price"  has  the  meaning
ascribed thereto in subsection 5.1(a);

      (qq)  "Retraction  Call  Right" has  the  meaning  ascribed
thereto in subsection 5.1(a);

      (rr) "Retraction Date" has the meaning ascribed thereto  in
section 5.2 of the Exchangeable Share Provisions;

      (ss)  "Retraction Request" has the meaning ascribed thereto
in section 5.1 of the Exchangeable Share Provisions;

      (tt)  "Revised  Exercise Price"  of  an  Option  means  the
exercise price of such Option in effect immediately prior to  the
Effective Time divided by the Exchange Ratio;

     (uu) "Transfer Agent" means Montreal Trust Company of Canada
or  such  other person as may from time to time be the  Registrar
and Transfer Agent for the Exchangeable Shares; and

      (vv) "Voting and Exchange Trust Agreement" means the Voting
and Exchange Trust Agreement between the Corporation, Orbital and
State  Street  Bank and Trust Company, made as of  the  Effective
Date.

1.2  Sections and Headings

           The division of this Plan of Arrangement into sections
and the insertion of headings are for reference purposes only and
shall  not affect the interpretation of this Plan of Arrangement.
Unless  otherwise  indicated,  any  reference  in  this  Plan  of
Arrangement  to a section or an Appendix refers to the  specified
section of or Appendix to this Plan of Arrangement.

1.3  Number, Gender and Persons

           In  this  Plan  of  Arrangement,  unless  the  context
otherwise  requires, words importing the singular number  include
the plural and vice versa, words importing any gender include all
genders   and   words  importing  persons  include   individuals,
corporations,  partnerships, associations, trusts, unincorporated
organizations,  governmental bodies and other legal  or  business
entities of any kind.

1.4       Withholding Tax

          All amounts required to be paid, deposited or delivered
under  this  Plan  of  Arrangement shall be  paid,  deposited  or
delivered  after deduction of any amount required  by  applicable
law  to  be  deducted  or  withheld on account  of  tax  and  the
deduction  of  such amounts and remittance to the applicable  tax
authorities   shall,   to  the  extent  thereof,   satisfy   such
requirement to pay, deposit or deliver hereunder.


                           ARTICLE 2

                          ARRANGEMENT

2.1  Arrangement

           At  the  Effective  Time on the  Effective  Date,  the
following  shall  occur  and shall be  deemed  to  occur  in  the
following order without any further act or formality:

          (a)   The  authorized share capital of the  Corporation
          shall  be  amended to authorize an unlimited number  of
          Exchangeable  Shares  and  10,000  Class  B   Preferred
          Shares;  as  a result of such amendment the Corporation
          shall  have three classes of authorized share  capital,
          namely,  an  unlimited  number  of  Common  Shares,  an
          unlimited  number  of Exchangeable  Shares  and  10,000
          Class  B  Preferred  Shares,  the  rights,  privileges,
          restrictions and conditions attaching to each of  which
          classes shall be as set out in Appendix A.

          (b)   The  Corporation  shall  issue  10,000  Class   B
          Preferred Shares to Canadian Imperial Bank of  Commerce
          in  partial consideration for services rendered to  the
          Corporation in connection with the Arrangement.

          (c)   The  Corporation shall add to its stated  capital
          account  in respect of the Class B Preferred Shares  an
          amount  in  respect  of the Class  B  Preferred  Shares
          issued pursuant to subsection 2.1(b) equal to $10,000.

          (d)  Schedule A and paragraphs 1 and 2 of Schedule B to
          the  Articles of the Corporation shall be  deleted  and
          the sentence "The annexed Schedule A is incorporated in
          this form." contained in paragraph 4 of the Articles of
          the  Corporation shall be deleted and replaced with the
          words "not applicable".

          (e)   All of the outstanding MDA Common Shares,  except
          MDA  Common Shares owned beneficially and of record  by
          the  Qualifying Holdcos and MDA Common Shares  held  by
          holders  who have exercised their rights of dissent  in
          accordance  with  section  3.1  hereof  and   who   are
          ultimately  entitled  to be paid fair  value  for  such
          shares  (hereinafter, "Dissenters") shall be  exchanged
          by  the  holders thereof for Exchangeable  Shares,  the
          number of which shall be the product of such number  of
          MDA  Common  Shares being exchanged  and  the  Exchange
          Ratio.   Each former holder of MDA Common Shares (other
          than  the  Qualifying  Holdcos  and  Dissenters)  shall
          receive   the  whole  number  of  Exchangeable   Shares
          resulting from the exchange of such holder's MDA Common
          Shares  for the consideration set out in the  foregoing
          sentence.   In lieu of fractional Exchangeable  Shares,
          each  holder of an MDA Common Share who otherwise would
          be  entitled  to receive a fraction of an  Exchangeable
          Share   on  the  exchange  shall  be  paid  an   amount
          determined as set forth in section 4.3 hereto.

          (f)  Upon the exchange referred to in subsection 2.1(e)
          above, each holder of exchanged MDA Common Shares shall
          cease  to be such a holder, shall have his name removed
          from  the register of holders of MDA Common Shares  and
          shall  become  a  holder of the number  of  fully  paid
          Exchangeable Shares to which he is entitled as a result
          of  such exchange and such holder's name shall be added
          to  the  register  of  holders of  Exchangeable  Shares
          accordingly.

          (g)   All  of  the outstanding shares of  each  of  the
          Qualifying  Holdcos shall be exchanged by  the  holders
          thereof  for Exchangeable Shares, the number  of  which
          shall be the product of the number of MDA Common Shares
          owned  beneficially  and of record by  each  respective
          Qualifying Holdco and the Exchange Ratio.  Each  former
          holder  of shares of a Qualifying Holdco shall  receive
          the  whole number of Exchangeable Shares resulting from
          the   exchange  of  all  such  holder's  shares  of   a
          Qualifying Holdco for the consideration set out in  the
          foregoing sentence.  In lieu of fractional Exchangeable
          Shares,  each  holder of shares of a Qualifying  Holdco
          who  otherwise would be entitled to receive a  fraction
          of  an Exchangeable Share on the exchange shall be paid
          an  amount  determined  as set  forth  in  section  4.3
          hereto.

          (h)  Upon the exchange referred to in subsection 2.1(g)
          above,  each  holder  of  exchanged  Qualifying  Holdco
          shares shall cease to be such a holder, shall have  his
          name removed from the register of holders of Qualifying
          Holdco  shares and shall become a holder of the  number
          of  fully  paid  Exchangeable Shares  to  which  he  is
          entitled as a result of such exchange and such holder's
          name  shall  be  added to the register  of  holders  of
          Exchangeable Shares accordingly.

          (i)   The  Corporation shall add to its stated  capital
          account  in  respect  of  Exchangeable  Shares   issued
          pursuant to subsections 2.1(e) and (g) an amount  equal
          to  the  aggregate fair market value of the MDA  Common
          Shares exchanged pursuant to subsection 2.1(e) and  the
          shares  of  Qualifying  Holdcos exchanged  pursuant  to
          subsection  2.1(g)  and  immediately  thereafter   such
          stated  capital shall be reduced to an amount equal  to
          the  aggregate  of (i) the cost, for  purposes  of  the
          Income  Tax  Act  (Canada), to the Corporation  of  the
          shares of the Qualifying Holdcos exchanged pursuant  to
          subsection  (g)  and,  (ii) the  paid-up  capital,  for
          purposes  of the Income Tax Act (Canada),  of  the  MDA
          Common Shares exchanged pursuant to subsection (e), all
          as   determined  by  the  Board  of  Directors  of  the
          Corporation.

          (j)   Each of the Qualifying Holdcos shall be dissolved
          into and its assets distributed to the Corporation  and
          for  the  purposes  of  such dissolution  each  of  the
          Qualifying Holdcos is authorized and directed  to  file
          articles  of  dissolution with the Director  under  the
          CBCA  at  such  time as the board of directors  of  the
          Corporation shall determine.  The Corporation, and each
          of  the  Qualifying Holdcos are authorized and directed
          to   create   and   deliver  all  such  documents   and
          instruments  as  may  be necessary  or  appropriate  to
          implement the dissolution.

          (k)   The name of each of the Qualifying Holdcos  shall
          be  removed from the register of holders of MDA  Common
          Shares  and the Corporation shall be registered as  the
          holder  of all of the issued and outstanding MDA Common
          Shares.

          (l)   Except for Options granted pursuant to the  KESOP
          88  or the ESOP 88 ("MDA 1988 Options") to holders  who
          have  exercised their rights of dissent  in  accordance
          with section 3.1 hereof and who are ultimately entitled
          to be paid fair value for the MDA Common Shares subject
          to such MDA 1988 Options, each outstanding Option shall
          become an option to purchase a number of Orbital Common
          Shares  equal  to the product (rounded to  the  nearest
          whole number) of the Exchange Ratio times the number of
          MDA Common Shares subject to such Option and having  an
          exercise price equal to the Revised Exercise Price  and
          having the same vesting, expiration and other terms  as
          in  effect  immediately prior to  the  Effective  Time,
          subject to subsection (m).

          (m)   The KESOP 88 and the ESOP 88 shall be amended  by
          deleting  the words in subsection 9.1 of the  KESOP  88
          and  the  words in subsection 8.1 of the  ESOP  88  and
          replacing each of them with the words following:

                "In  the  event  that  the  outstanding
          Shares  of the Company shall be changed  into
          or  exchanged  for a different number  or  of
          kind  of  securities of  the  Company  or  of
          another   corporation,  whether  through   an
          arrangement,  amalgamation or  other  similar
          statutory    procedure,    or     a     share
          capitalization,        sub-division        or
          consolidation,    then   there    shall    be
          substituted  for each Share  subject  to  any
          such  Option,  for each share authorized  for
          issuance  pursuant to the Plan  but  not  yet
          covered  by  an  Option and for  the  maximum
          number of Shares issuable under the Plan with
          respect  to any year, the number and kind  of
          securities into which each outstanding  Share
          shall  be  so changed or for which each  such
          Share shall be exchanged.

                In  the event that there shall  be  any
          change,  other  than  as  specified  in  this
          subsection,  in  the  number   or   kind   of
          outstanding Shares of the Company or  of  any
          securities into which such Shares shall  have
          been  changed or for which Shares shall  have
          been  exchanged, then an equitable adjustment
          shall be made in the number or kind of Shares
          or any such securities theretofore authorized
          for issuance pursuant to the Plan but not yet
          covered  by an Option, of the Shares  or  any
          such securities then subject to an Option  or
          Options,  and  the maximum of Shares  or  any
          such  securities issuable under the Plan with
          respect  to any year, such adjustment  to  be
          reasonably determined by the Directors and to
          be effective and binding for all purposes.

                In the case of any such substitution or
          adjustment   as   provided   for   in    this
          subsection, the Option price for  each  share
          option   agreement  for  each  Share  covered
          thereby   prior   to  such  substitution   or
          adjustment   will   be  proportionately   and
          appropriately  varied.  Such variation  shall
          generally   require  that   the   number   of
          securities  covered by the Option  after  the
          relevant  event  multiplied  by  the  revised
          Option price shall equal the number of shares
          covered  by the Option prior to the  relevant
          event   multiplied  by  the  original  Option
          price.    No   adjustment   or   substitution
          provided for in this subsection shall require
          the Company in any share option agreement  to
          issue   a  fractional  Share  and  the  total
          substitution  or adjustment with  respect  to
          each  share option agreement shall be limited
          accordingly."

          (n)   The  name of the Corporation shall be changed  to
          "MacDonald Dettwiler Holdings Inc."


                           ARTICLE 3

                       RIGHTS OF DISSENT

3.1  Rights of Dissent

          Holders of MDA Common Shares or of MDA 1988 Options may
exercise rights of dissent with respect to such MDA Common Shares
or the MDA Common Shares subject to such MDA 1988 Options, as the
case  may  be  ("Dissenters' Shares").  In order to dissent  with
respect  to  MDA  1988 Options, such MDA 1988  Options  shall  be
deemed to have been exercised for the purpose of exercising  such
dissent  rights and the exercise price under each such  MDA  1988
Option  shall  be deemed to be satisfied by set-off  against  the
fair  value  paid  for  the Dissenters' Shares  subject  thereto,
provided  that  if  the holder of any such  MDA  1988  Option  is
ultimately not entitled to be paid fair value for the Dissenters'
Shares subject thereto, such MDA 1988 Option shall be deemed  not
to  have  been exercised and shall become an option  to  purchase
Orbital Common Shares in accordance with subsection 2.1(l).   All
such rights of dissent shall be exercised pursuant to and in  the
manner set forth in section 190 of the CBCA and this section  3.1
(the "Dissent Procedures") in connection with the Arrangement and
holders who duly exercise such rights of dissent and who:

          (a)   are ultimately entitled to be paid fair value for
          their  Dissenters'  Shares  shall  be  deemed  to  have
          transferred  such  Dissenters'  Shares   to   MDA   for
          cancellation on the Effective Date; or

          (b)  are ultimately not entitled, for any reason, to be
          paid  fair value for their Dissenters' Shares shall  be
          deemed  to have participated in the Arrangement on  the
          same  basis as any non-dissenting holder of MDA  Common
          Shares  or  Options,  as the case  may  be,  and  shall
          receive Exchangeable Shares on the basis determined  in
          accordance  with subsection 2.1(e) or  options  on  the
          basis  provided in subsection 2.1(l), as the  case  may
          be.

In  no  case  shall MDA be required to recognize such holders  as
holders of MDA Common Shares or MDA 1988 Options, as the case may
be,  on  and  after  the Effective Date, and the  names  of  such
holders of MDA Common Shares or MDA 1988 Options, as the case may
be,  shall be deleted from the register of holders of MDA  Common
Shares  and all records of Options maintained by the Corporation,
respectively, on the Effective Date.


                           ARTICLE 4

               CERTIFICATES AND FRACTIONAL SHARES

4.1  Issuance of Certificates Representing Exchangeable Shares

            At   or  promptly  after  the  Effective  Time,   the
Corporation shall deposit with the Depositary, for the benefit of
the   holders   of  MDA  Common  Shares  exchanged  pursuant   to
subsection  2.1(e)  and the holders of shares of  the  Qualifying
Holdcos  exchanged  pursuant to subsection  2.1(g),  certificates
representing   the   Exchangeable  Shares  issued   pursuant   to
subsections 2.1(f) and (h).  Upon surrender to the Depositary for
cancellation  of  a certificate which immediately  prior  to  the
Effective   Time  represented  outstanding  MDA   Common   Shares
exchanged pursuant to subsection 2.1(e) or outstanding shares  of
Qualifying  Holdcos exchanged pursuant to subsection  2.1(g),  as
the   case  may  be,  together  with  such  other  documents  and
instruments as would have been required to effect the transfer of
the  shares  formerly represented by such certificate  under  the
CBCA  and  the  articles and by-laws of MDA or  of  the  relevant
Qualifying  Holdco,  as  the case may  be,  and  such  additional
documents  and  instruments  as  the  Depositary  may  reasonably
require,  the  holder  of such surrendered certificate  shall  be
entitled  to  receive in exchange therefor,  and  the  Depositary
shall  deliver  to  such holder, a certificate representing  that
number (rounded down to the nearest whole number) of Exchangeable
Shares which such holder has the right to receive (together  with
any  dividends or distributions with respect thereto pursuant  to
section  4.2  and  any  cash in lieu of  fractional  Exchangeable
Shares   pursuant  to  section  4.3),  and  the  certificate   so
surrendered  shall forthwith be cancelled.  In  the  event  of  a
transfer  of  ownership  of  MDA  Common  Shares  which  is   not
registered   in  the  transfer  records  of  MDA,  a  certificate
representing  the  proper number of Exchangeable  Shares  may  be
issued  to a transferee if the certificate representing such  MDA
Common Shares is presented to the Depositary, accompanied by  all
documents  required to evidence and effect such transfer.   Until
surrendered as contemplated by this section 4.1, each certificate
which   immediately  prior  to  the  Effective  Time  represented
outstanding MDA Common Shares or outstanding shares of Qualifying
Holdcos,   as   the  case  may  be,  that  were   purchased   for
consideration consisting of Exchangeable Shares shall  be  deemed
at  any time after the Effective Time to represent only the right
to  receive  upon such surrender (i) the certificate representing
Exchangeable Shares as contemplated by this section 4.1,  (ii)  a
cash  payment  in lieu of any fractional Exchangeable  Shares  as
contemplated   by  section  4.3  and  (iii)  any   dividends   or
distributions  with  a  record  date  after  the  Effective  Time
theretofore  paid or payable with respect to Exchangeable  Shares
as contemplated by section 4.2.

4.2  Distributions with Respect to Unsurrendered Certificates

           No  dividends or other distributions declared or  made
after the Effective Time with respect to Exchangeable Shares with
a  record  date  after the Effective Time shall be  paid  to  the
holder of any unsurrendered certificate which, immediately  prior
to  the Effective Time, represented outstanding MDA Common Shares
or  shares of Qualifying Holdcos that were exchanged pursuant  to
section  2.1,  and  no cash payment in lieu of fractional  shares
shall  be paid to any such holder pursuant to section 4.3, unless
and  until  such certificate shall be surrendered  in  accordance
with  section 4.1.  Subject to applicable law and to section 4.5,
at the time of such surrender of any such certificate (or, in the
case  of  clause  (iii) below, at the appropriate payment  date),
there  shall  be  paid to the record holder  of  the  certificate
representing  whole  Exchangeable Shares into  which  the  shares
represented  by  the  surrendered  certificate  were   exchanged,
without interest, (i) the amount of any cash payable in lieu of a
fractional  Exchangeable Share to which such holder  is  entitled
pursuant  to section 4.3, (ii) the amount of dividends  or  other
distributions  with  a  record  date  after  the  Effective  Time
theretofore paid with respect to such whole Exchangeable  Shares,
and  (iii) the amount of dividends or other distributions with  a
record date after the Effective Time but prior to surrender and a
payment date subsequent to surrender payable with respect to such
whole Exchangeable Shares.

4.3  No Fractional Shares

            No  certificates  or  scrip  representing  fractional
Exchangeable  Shares  shall  be issued  upon  the  surrender  for
exchange of certificates pursuant to section 4.1 and no dividend,
stock  split  or  other change in the capital  structure  of  the
Corporation shall relate to any such fractional security and such
fractional interests shall not entitle the owner thereof to  vote
or   to  exercise  any  rights  as  a  security  holder  of   the
Corporation.   In  lieu of any such fractional  securities,  each
person entitled to a fractional interest in an Exchangeable Share
will  receive  an  amount of cash (rounded to the  nearest  whole
cent),  without interest, equal to the Canadian Dollar Equivalent
as  of  the  Effective Date of the product of (i) such  fraction,
multiplied by (ii) the Average Closing Price.

4.4  Lost Certificates

           If  any  certificate  that immediately  prior  to  the
Effective  Time  represented outstanding MDA Common  Shares  that
were  exchanged pursuant to section 2.1 has been lost, stolen  or
destroyed,  upon the making of an affidavit of that fact  by  the
person claiming such certificate to be lost, stolen or destroyed,
the  Depositary will issue in exchange for such lost,  stolen  or
destroyed  certificate,  certificates  representing  Exchangeable
Shares  (and any dividends or distributions with respect  thereto
and  any  cash  pursuant to section 4.3) deliverable  in  respect
thereof  as  determined  in accordance with  section  2.1.   When
authorizing  such  payment in exchange for any  lost,  stolen  or
destroyed   certificate,   the  person   to   whom   certificates
representing  Exchangeable Shares are to be issued  shall,  as  a
condition  precedent  to  the  issuance  thereof,  give  a   bond
satisfactory to MDA or the Corporation, as the case  may  be,  in
such  sum  as  MDA  or  the Corporation may direct  or  otherwise
indemnify MDA or the Corporation in a manner satisfactory to  the
Corporation  and MDA against any claim that may be  made  against
MDA or the Corporation with respect to the certificate alleged to
have been lost, stolen or destroyed.

4.5  Extinguishment of Rights

          Any certificate that immediately prior to the Effective
Time  represented  outstanding MDA Common Shares  or  outstanding
shares  of  a  Qualifying Holdco that were purchased pursuant  to
section  2.1  and  not  deposited,  with  all  other  instruments
required by section 4.1, on or prior to the sixth anniversary  of
the  Effective Date shall cease to represent a claim or  interest
of  any  kind  or  nature as a shareholder of MDA,  the  relevant
Qualifying  Holdco  or  the  Corporation.   On  such  date,   the
Exchangeable Shares to which the former registered holder of  the
certificate referred to in the preceding sentence was  ultimately
entitled  shall  be  deemed  to  have  been  surrendered  to  the
Corporation   together  with  all  entitlements   to   dividends,
distributions  and  interests  thereon  held  for   such   former
registered holder for no consideration.


                           ARTICLE 5

    CERTAIN RIGHTS OF ORBITAL TO ACQUIRE EXCHANGEABLE SHARES

5.1  Orbital Retraction Call Right

       (a)    Orbital  shall  have  the  overriding  right   (the
"Retraction Call Right"), notwithstanding the proposed redemption
of  Retracted Shares by the Corporation on a Retraction Date,  to
purchase  from  the  holder  of  the  Retracted  Shares  on   the
Retraction  Date the Retracted Shares upon payment by Orbital  to
the holder of an amount per share equal to (a) the Current Market
Price  multiplied by the Current Orbital Common Share Equivalent,
in  each  case determined on the Retraction Date, which shall  be
satisfied  in full in respect of the Retracted Shares by  causing
to  be  delivered  to such holder such whole  number  of  Orbital
Common  Shares as is equal to the product obtained by multiplying
the  number  of  Retracted Shares by the Current  Orbital  Common
Share  Equivalent  (together  with  an  amount  in  lieu  of  any
fractional  Orbital Common Share resulting from such  calculation
payable  in accordance with section 5.5), plus (b) the  aggregate
of  all  dividends  declared and unpaid on such  Retracted  Share
(collectively  the  "Retraction Call Purchase  Price").   In  the
event  of  the exercise of the Retraction Call Right by  Orbital,
the holder of the Retracted Shares shall be obligated to sell  to
Orbital,  and  Orbital  shall  be  obligated  to  purchase,   the
Retracted  Shares on the Retraction Date upon payment by  Orbital
to  such  holder of the Retraction Call Purchase Price  for  each
Retracted Share.

     (b)  In order to exercise the Retraction Call Right, Orbital
must notify the Transfer Agent in writing of its determination to
do  so  (the  "Orbital Call Notice") prior to the expiry  of  the
third Business Day after the receipt by the Transfer Agent of the
Retraction  Request.  If Orbital does not so notify the  Transfer
Agent,  the  Transfer Agent will notify the  holder  as  soon  as
possible thereafter that Orbital will not exercise the Retraction
Call  Right.  If Orbital delivers the Orbital Call Notice  before
the end of such three Business Day period, the Retraction Request
shall  thereupon be considered only to be an offer by the  holder
to  sell  the Retracted Shares to Orbital in accordance with  the
Retraction Call Right.  In such event, the Corporation shall  not
redeem the Retracted Shares and Orbital shall purchase from  such
holder  and  such holder shall sell to Orbital on the  Retraction
Date  the Retracted Shares for the Retraction Call Purchase Price
for each Retracted Share.

      (c)   For  the  purposes of completing a  purchase  of  the
Retracted  Shares pursuant to the Retraction Call Right,  Orbital
shall  deposit  with  the  Transfer  Agent,  on  or  before   the
Retraction  Date,  certificates representing the  Orbital  Common
Shares  to be delivered to the holder of the Retracted Shares  in
payment  of  the  total Retraction Call Purchase  Price  for  the
Retracted  Shares  (or  the portion thereof  payable  in  Orbital
Common Shares, as the case may be) and a cheque in the amount  of
the  remaining  portion,  if any, of the  total  Retraction  Call
Purchase  Price (or, if any part of the Retraction Call  Purchase
Price consists of dividends payable in property, such property or
property that is the same as or economically equivalent  to  such
property).   Provided  that such total Retraction  Call  Purchase
Price  has been so deposited with the Transfer Agent, the closing
of  the purchase and sale of the Retracted Shares pursuant to the
Retraction Call Right shall be deemed to have occurred as of  the
close  of  business  on  the Retraction  Date  and,  for  greater
certainty,  no  redemption by the Corporation of  such  Retracted
Shares  shall  take place on the Retraction Date.  Orbital  shall
cause  the  Transfer  Agent  to deliver  to  the  holder  of  the
Retracted Shares, at the address of such holder recorded  in  the
securities  register  of  the Corporation  for  the  Exchangeable
Shares  or  at  the address specified in the holder's  Retraction
Request or by holding for pick-up by the holder at the office  of
the Transfer Agent to which the Retraction Request was delivered,
in   payment  of  such  total  Retraction  Call  Purchase  Price,
certificates  representing  the  Orbital  Common  Shares  to   be
delivered in respect of such payment (which shares shall be  duly
issued  as  fully paid and non-assessable and shall be  free  and
clear  of any Liens) registered in the name of the holder  or  in
such other name as the holder may request in payment of such and,
if applicable, a cheque of Orbital payable at par and in Canadian
dollars  at  any  branch  of  the  bankers  of  Orbital  or   the
Corporation  in  Canada (or, if any part of the  Retraction  Call
Purchase  Price  consists of dividends payable in property,  such
property  or  property  that  is  the  same  as  or  economically
equivalent  to  such  property),  and  such  delivery   of   such
certificates and cheque (and property, if any) to the  holder  on
behalf  of  Orbital by the Transfer Agent shall be deemed  to  be
payment of and shall satisfy and discharge all liability for  the
total Retraction Call Purchase Price to the extent that the  same
is  represented  by  such  share  certificates  and  cheque  (and
property,  if  any),  unless  such cheque  is  not  paid  on  due
presentation.   On  and  after  the  close  of  business  on  the
Retraction  Date, the holder of the Retracted Shares shall  cease
to be a holder of such Retracted Shares and shall not be entitled
to  exercise  any  of the rights of a holder in respect  thereof,
other  than  the  right to receive the Retraction  Call  Purchase
Price, unless upon presentation and surrender of certificates  in
accordance  with the foregoing provisions, payment of  the  total
Retraction  Call Purchase Price shall not be made, in which  case
the rights of such holder shall remain unaffected until the total
Retraction  Call  Purchase Price has  been  paid  in  the  manner
hereinbefore provided.  On and after the close of business on the
Retraction  Date,  provided that presentation  and  surrender  of
certificates  and payment of the total Retraction  Call  Purchase
Price  has been made in accordance with the foregoing provisions,
the  holder of the Retracted Shares so purchased by Orbital shall
thereafter  be  considered and deemed for all purposes  to  be  a
holder of the Orbital Common Shares delivered to such holder.

5.2  Orbital Liquidation Call Right

       (a)    Orbital  shall  have  the  overriding  right   (the
"Liquidation  Call  Right"), in the event of and  notwithstanding
the  proposed  liquidation,  dissolution  or  winding-up  of  the
Corporation, to purchase from all but not less than  all  of  the
holders  (other than Orbital and its Affiliates) of  Exchangeable
Shares  on the Liquidation Date all but not less than all of  the
Exchangeable  Shares  held  by each such  holder  on  payment  by
Orbital  of  an amount per share equal to (a) the Current  Market
Price  multiplied by the Current Orbital Common Share Equivalent,
in  each case determined on the Liquidation Date, which shall  be
satisfied  in  full in respect of all of the Exchangeable  Shares
held  by  such holder by Orbital causing to be delivered to  such
holder such whole number of Orbital Common Shares as is equal  to
the   product  obtained  by  multiplying  the  number   of   such
Exchangeable   Shares  by  the  Current  Orbital   Common   Share
Equivalent  (together with an amount in lieu  of  any  fractional
Orbital  Common Share resulting from such calculation payable  in
accordance  with  section 5.5), plus (b)  the  aggregate  of  all
dividends  declared and unpaid on such Exchangeable Share  up  to
the Liquidation Date (collectively the "Liquidation Call Purchase
Price").   In  the event of the exercise of the Liquidation  Call
Right by Orbital, each holder shall be obligated to sell all  the
Exchangeable  Shares  held  by  the  holder  to  Orbital  on  the
Liquidation  Date  on payment by Orbital to  the  holder  of  the
Liquidation Call Purchase Price for each such share.

      (b)   To exercise the Liquidation Call Right, Orbital  must
notify  the  Transfer  Agent  and the  Corporation  of  Orbital's
intention  to  exercise such right at least 30  days  before  the
Liquidation   Date  in  the  case  of  a  voluntary  liquidation,
dissolution  or winding up of the Corporation and at  least  five
Business  Days  before the Liquidation Date in  the  case  of  an
involuntary  liquidation,  dissolution  or  winding  up  of   the
Corporation.   The  Transfer Agent will  notify  the  holders  of
Exchangeable  Shares as to whether or not Orbital  has  exercised
the Liquidation Call Right forthwith after the expiry of the date
by  which  the  same  may be exercised by  Orbital.   If  Orbital
exercises  the  Liquidation Call Right, on the  Liquidation  Date
Orbital  will  purchase and the holders  will  sell  all  of  the
Exchangeable Shares then outstanding for a price per share  equal
to the Liquidation Call Purchase Price.

      (c)   For  the purposes of completing the purchase  of  the
Exchangeable  Shares  pursuant to  the  Liquidation  Call  Right,
Orbital  shall deposit with the Transfer Agent, on or before  the
Liquidation Date, certificates representing the aggregate  number
of  Orbital  Common Shares deliverable by Orbital  (which  shares
shall  be duly issued as fully paid and non-assessable and  shall
be  free  and  clear  of  any Liens)  in  payment  of  the  total
Liquidation  Call Purchase Price (or the portion thereof  payable
in  Orbital  Common Shares, as the case may be) and a  cheque  or
cheques  in the amount of the remaining portion, if any,  of  the
total  Liquidation Call Purchase Price (or, if any  part  of  the
Liquidation Call Purchase Price consists of dividends payable  in
property,  such  property or property that  is  the  same  as  or
economically  equivalent to such property).  Provided  that  such
total Liquidation Call Purchase Price has been so deposited  with
the  Transfer Agent, on and after the Liquidation Date the rights
of  each  holder  of  Exchangeable  Shares  will  be  limited  to
receiving   such  holder's  proportionate  part  of   the   total
Liquidation   Call  Purchase  Price  payable  by   Orbital   upon
presentation   and  surrender  by  the  holder  of   certificates
representing the Exchangeable Shares held by such holder and  the
holder shall on and after the Liquidation Date be considered  and
deemed  for  all purposes to be the holder of the Orbital  Common
Shares delivered to it.  Upon surrender to the Transfer Agent  of
a  certificate or certificates representing Exchangeable  Shares,
together  with  such other documents and instruments  as  may  be
required  to effect a transfer of Exchangeable Shares  under  the
CBCA  and  the articles and by-laws of the Corporation  and  such
additional  documents and instruments as the Transfer  Agent  may
reasonably require, the holder of such surrendered certificate or
certificates  shall be entitled to receive in exchange  therefor,
and the Transfer Agent on behalf of Orbital shall deliver to such
holder,  certificates representing the Orbital Common  Shares  to
which  the holder is entitled and a cheque or cheques of  Orbital
payable  at  par  and in Canadian dollars at any  branch  of  the
bankers of Orbital or of the Corporation in Canada in payment  of
the  remaining  portion,  if any, of the total  Liquidation  Call
Purchase  Price (or, if any part of the Liquidation Call Purchase
Price consists of dividends payable in property, such property or
property that is the same as or economically equivalent  to  such
property).   If  Orbital does not exercise the  Liquidation  Call
Right in the manner described above, on the Liquidation Date  the
holders of the Exchangeable Shares will be entitled to receive in
exchange therefor the Liquidation Amount otherwise payable by the
Corporation  in  connection with the liquidation, dissolution  or
winding-up of the Corporation pursuant to sections 4.1 to 4.3  of
the Exchangeable Share Provisions.

5.3  Orbital Redemption Call Right

       (a)    Orbital  shall  have  the  overriding  right   (the
"Redemption Call Right"), notwithstanding the proposed redemption
of  the  Exchangeable Shares by the Corporation on the  Automatic
Redemption  Date, to purchase from all but not less than  all  of
the   holders   (other  than  Orbital  or  its   Affiliates)   of
Exchangeable Shares on the Automatic Redemption Date all but  not
less than all of the Exchangeable Shares held by each such holder
on  payment by Orbital to the holder of an amount per share equal
to (a) the Current Market Price multiplied by the Current Orbital
Common Share Equivalent, in each case determined on the Automatic
Redemption  Date, which shall be satisfied in full in respect  of
all of the Exchangeable Shares held by such holder by causing  to
be  delivered to such holder such number of Orbital Common Shares
as  is equal to the product obtained by multiplying the number of
such  Exchangeable  Shares by the Current  Orbital  Common  Share
Equivalent  (together with an amount in lieu  of  any  fractional
Orbital  Common Share resulting from such calculation payable  in
accordance  with  section 5.5), plus (b)  the  aggregate  of  all
dividends   declared  and  unpaid  on  such  Exchangeable   Share
(collectively  the  "Redemption Call Purchase  Price").   In  the
event  of  the exercise of the Redemption Call Right by  Orbital,
each  holder  shall be obligated to sell to Orbital, and  Orbital
shall be obligated to purchase, all the Exchangeable Shares  held
by  the  holder  on the Automatic Redemption Date on  payment  by
Orbital  to the holder of the Redemption Call Purchase Price  for
each such share.

      (b)   To  exercise the Redemption Call Right, Orbital  must
notify  the  Transfer  Agent, as agent for  the  holders  of  the
Exchangeable  Shares, and the Corporation of Orbital's  intention
to  exercise  such  right at least 75 days before  the  Automatic
Redemption  Date.  The Transfer Agent will notify the holders  of
the  Exchangeable  Shares  as  to  whether  or  not  Orbital  has
exercised the Redemption Call Right forthwith after the  date  by
which the same may be exercised by Orbital.  If Orbital exercises
the  Redemption  Call  Right, on the  Automatic  Redemption  Date
Orbital  will  purchase and the holders  will  sell  all  of  the
Exchangeable Shares then outstanding for a price per share  equal
to the Redemption Call Purchase Price.

      (c)   For  the purposes of completing the purchase  of  the
Exchangeable  Shares  pursuant  to  the  Redemption  Call  Right,
Orbital  shall deposit with the Transfer Agent, on or before  the
Automatic   Redemption   Date,  certificates   representing   the
aggregate number of Orbital Common Shares deliverable by  Orbital
(which   shares   shall  be  duly  issued  as  fully   paid   and
non-assessable  and  shall be free and clear  of  any  Liens)  in
payment  of  the  total Redemption Call Purchase  Price  (or  the
portion thereof payable in Orbital Common Shares, as the case may
be)  and  a  cheque  or cheques in the amount  of  the  remaining
portion, if any, of the total Redemption Call Purchase Price (or,
if  part  of  the  Redemption  Call Purchase  Price  consists  of
dividends payable in property, such property or property the same
as  or economically equivalent to such property).  Provided  that
such  total Redemption Call Purchase Price has been so  deposited
with  the  Transfer Agent, on and after the Automatic  Redemption
Date  the  rights of each holder of Exchangeable Shares  will  be
limited  to  receiving such holder's proportionate  part  of  the
total  Redemption  Call Purchase Price payable  by  Orbital  upon
presentation   and  surrender  by  the  holder  of   certificates
representing the Exchangeable Shares held by such holder and  the
holder  shall  on  and  after the Automatic  Redemption  Date  be
considered  and deemed for all purposes to be the holder  of  the
Orbital  Common Shares delivered to such holder.  Upon  surrender
to   the   Transfer  Agent  of  a  certificate  or   certificates
representing  Exchangeable  Shares,  together  with  such   other
documents and instruments as may be required to effect a transfer
of  Exchangeable  Shares  under the CBCA  and  the  articles  and
by-laws  of  the  Corporation and such additional  documents  and
instruments  as  the Transfer Agent may reasonably  require,  the
holder  of such surrendered certificate or certificates shall  be
entitled to receive in exchange therefor, and the Transfer  Agent
on  behalf  of Orbital shall deliver to such holder, certificates
representing  the Orbital Common Shares to which  the  holder  is
entitled and a cheque or cheques of Orbital payable at par and in
Canadian  dollars at any branch of the bankers of Orbital  or  of
the Corporation in Canada in payment of the remaining portion, if
any, of the total Redemption Call Purchase Price (or, if part  of
the  Redemption Call Purchase Price consists of dividends payable
in   property,  such  property  or  property  the  same   as   or
economically equivalent to such property).  If Orbital  does  not
exercise the Redemption Call Right in the manner described above,
on  the Automatic Redemption Date the holders of the Exchangeable
Shares  will  be  entitled to receive in  exchange  therefor  the
redemption   price  otherwise  payable  by  the  Corporation   in
connection  with  the  redemption  of  the  Exchangeable   Shares
pursuant  to  sections  6.1  and 6.2 of  the  Exchangeable  Share
Provisions.

5.4  Consideration for Call Rights of Orbital

           The  Retraction Call Right, the Liquidation Call Right
and  the  Redemption Call Right are granted  to  Orbital  by  the
holders  of Exchangeable Shares in consideration of the grant  by
Orbital  of  the  Voting Rights, Automatic  Exchange  Rights  and
Exchange  Right  (as such terms are respectively defined  in  the
Voting  and Exchange Trust Agreement) to the Trustee (as  defined
in  the  Exchangeable Share Provisions) for the  benefit  of  the
holders of Exchangeable Shares.

5.5  Fractional Orbital Common Shares

            No  certificates  or  scrip  representing  fractional
Orbital   Common  Shares  shall  be  delivered  to   holders   of
Exchangeable Shares pursuant to the provisions hereof.   In  lieu
of  any  such  fractional security, each  person  entitled  to  a
fractional  interest in an Orbital Common Share will  receive  an
amount  of  cash  (rounded to the nearest  whole  cent),  without
interest,  equal  to  the Canadian Dollar Equivalent  as  of  the
fourth  Business Day prior to the relevant date  of  delivery  of
certificates representing Orbital Common Shares (the  "Fractional
Share  Calculation  Date") of the product of (i)  such  fraction,
multiplied  by  (ii)  the closing sale price  of  Orbital  Common
Shares  as reported on NASDAQ on the Fractional Share Calculation
Date.

5.6  Economic Equivalence

           The  Board of Directors shall determine, in good faith
and in its sole discretion (with the assistance of such reputable
and qualified independent financial advisors and/or other experts
as  the Board of Directors may require) economic equivalence  for
the  purposes  of  any  provision herein  that  requires  such  a
determination and each such determination shall be conclusive and
binding on Orbital and the holders of Exchangeable Shares,  where
applicable.

5.7  Capital Reorganization of Orbital

           If  at  any time there is a capital reorganization  of
Orbital  that  is  not  provided for in subsection  1.1(o)  or  a
consolidation, merger, arrangement or amalgamation (statutory  or
otherwise) of Orbital with or into another entity (any such event
being   called  a  "Capital  Reorganization"),  any   holder   of
Exchangeable  Shares  whose Exchangeable  Shares  have  not  been
exchanged  for  Orbital  Common Shares  in  accordance  with  the
provisions  hereof  prior to the record  date  for  such  Capital
Reorganization  shall be entitled to receive  and  shall  accept,
upon  any  such  exchange occurring pursuant  to  the  provisions
hereof  at  any  time  after the record  date  for  such  Capital
Reorganization,  in  lieu of the Orbital Common  Shares  that  he
would  otherwise  have been entitled to receive pursuant  to  the
provisions  hereof, the number of shares or other  securities  of
Orbital  or  of  the  body  corporate  resulting,  surviving   or
continuing  from  the Capital Reorganization, or other  property,
that  such holder would have been entitled to receive as a result
of  such  Capital Reorganization if, on the record date,  he  had
been the registered holder of the number of Orbital Common Shares
to   which  he  was  then  entitled  upon  any  exchange  of  his
Exchangeable Shares into Orbital Common Shares in accordance with
the  provisions hereof, subject to adjustment thereafter  in  the
same manner, as nearly as may be possible, as is provided for  in
subsection  1.1(o); provided that no such Capital  Reorganization
shall  be  carried into effect unless all necessary  steps  shall
have  been taken so that each holder of Exchangeable Shares shall
thereafter  be  entitled to receive, upon  any  exchange  of  his
Exchangeable  Shares  pursuant to  the  provisions  hereof,  such
number  of shares or other securities of Orbital or of  the  body
corporate  resulting, surviving or continuing  from  the  Capital
Reorganization, or other property.

5.8  Other Change in Orbital Common Shares

          In the case of any reclassification of, or other change
in,  the  outstanding Orbital Common Shares other than  a  Common
Share  Reorganization or a Capital Reorganization,  such  changes
shall be made in the rights attaching to the Exchangeable Shares,
without  any action on the part of the Corporation or the holders
of  the Exchangeable Shares to the extent permitted by applicable
law,  effective immediately following the record  date  for  such
reclassification  or  other change, to the  extent  necessary  to
ensure  that holders of Exchangeable Shares shall be entitled  to
receive,  upon the occurrence at any time after such record  date
of  any  event  whereby they would receive Orbital Common  Shares
pursuant  to  the provisions hereof, such shares,  securities  or
rights  as they would have received if their Exchangeable  Shares
had  been  exchanged for Orbital Common Shares  pursuant  to  the
provisions hereof immediately prior to such record date,  subject
to  adjustment thereafter in the same manner, as nearly as may be
possible, as is provided for in subsection 1.1(o).


                           ARTICLE 6

                           AMENDMENT

6.1  Plan of Arrangement Amendment

      (a)   By instrument in writing the Corporation and MDA  may
amend,  modify and/or supplement this Plan of Arrangement at  any
time  and  from  time to time provided that any  such  amendment,
modification,  or supplement must be (i) agreed  to  by  Orbital,
(ii)  filed  with the Court and, if made following  the  Meeting,
approved  by the Court and (iii) communicated to holders  of  MDA
Common Shares and Options in the manner required by the Court (if
so required).

      (b)   Notwithstanding subsection 6.1(a), by  instrument  in
writing  the Corporation and MDA may modify this Plan up to,  but
not  after,  the termination of the Meeting to add as  Qualifying
Holdcos  any  corporations  that, in the  sole  judgment  of  the
Corporation,  meet  the  requirements of  Section  2.1.2  of  the
Combination  Agreement,  such modification  to  be  evidenced  by
adding  the  name of each such Qualifying Holdco  to  Appendix  B
hereto.

      (c)  Any amendment, modification or supplement to this Plan
of  Arrangement  that  is  approved by the  Court  following  the
Meeting shall be effective only if (i) it is consented to by each
of  the Corporation, MDA and Orbital and (ii) it is consented  to
by  the holders of the MDA Common Shares, the holders of the  MDA
1988  Options  and  the holders of the shares of  any  Qualifying
Holdcos, in each case to the extent so required by the Court.





               APPENDIX A TO PLAN OF ARRANGEMENT


        PROVISIONS ATTACHING TO THE EXCHANGEABLE SHARES

            The  Exchangeable  Shares  in  the  capital  of   the
Corporation   shall   have  the  following  rights,   privileges,
restrictions and conditions.


                           ARTICLE 1

                         INTERPRETATION

1.1       For the purposes of these share provisions:

          (a)   "Affiliate" of any person means any other  person
          directly or indirectly controlling, controlled  by,  or
          under  common  control  with,  that  person.   For  the
          purposes of this definition, "control" (including, with
          correlative    meanings,   the   terms   "controlling",
          "controlled  by" and "under common control  with"),  as
          applied  to any person, means the possession by another
          person, directly or indirectly, of the power to  direct
          or  cause  the direction of the management and policies
          of  that  first mentioned person, whether  through  the
          ownership   of  voting  securities,  by   contract   or
          otherwise.

          (b)   "Automatic Redemption Date" means November      ,
          2000, unless such date shall be accelerated at any time
          to  a  specified earlier date by the Board of Directors
          upon  at  least  75 days prior written  notice  to  the
          registered  holders of Exchangeable  Shares,  in  which
          case  the  Automatic  Redemption  Date  shall  be  such
          earlier  date;  provided, however, that  the  Board  of
          Directors  may  so accelerate the Automatic  Redemption
          Date  only at such time as there are outstanding  fewer
          than  400,000 Exchangeable Shares held by holders other
          than Orbital and its Affiliates.

          (c)   "Board of Directors" means the board of directors
          of the Corporation.

          (d)   "Business  Day"  means  any  day  other  than   a
          Saturday, a Sunday or a day when banks are not open for
          business in one or both of the Commonwealth of Virginia
          and Vancouver, British Columbia.

          (e)   "Canadian Dollar Equivalent" means in respect  of
          an amount expressed in a foreign currency (the "Foreign
          Currency  Amount") at any date the product obtained  by
          multiplying (a) the Foreign Currency Amount by (b)  the
          noon  spot exchange rate on such date for such  foreign
          currency  expressed in Canadian dollars as reported  by
          the  Bank of Canada or, in the event such spot exchange
          rate  is not available, such exchange rate on such date
          for such foreign currency expressed in Canadian dollars
          as  may  be  deemed  by the Board of  Directors  to  be
          appropriate for such purpose.

          (f)   "Capital Reorganization" has the meaning ascribed
          thereto in section 9.2 of these share provisions.

          (g)  "CBCA" means the Canada Business Corporations Act,
          as amended from time to time.

          (h)   "Corporation" means MacDonald Dettwiler  Holdings
          Inc.  (formerly  known  as  3173623  Canada  Inc.),   a
          corporation incorporated under the CBCA.

          (i)   "Current  Market Price" means, in respect  of  an
          Orbital  Common Share on any date, the Canadian  Dollar
          Equivalent of the closing sale price of Orbital  Common
          Shares  on such day (or, if no trades of Orbital Common
          Shares  occurred on such day, on the last  trading  day
          prior  thereto on which such trades occurred)  reported
          on  NASDAQ,  or, if the Orbital Common Shares  are  not
          then quoted on NASDAQ, on such other stock exchange  or
          automated quotation system on which the Orbital  Common
          Shares are listed or quoted, as the case may be, as may
          be selected by the Board of Directors for such purpose;
          provided, however, that if in the opinion of the  Board
          of   Directors  the  public  distribution  or   trading
          activity  of  Orbital Common Shares during such  period
          does  not create a market that reflects the fair market
          value  of  an  Orbital Common Share, then  the  Current
          Market  Price  of  an  Orbital Common  Share  shall  be
          determined  by  the Board of Directors based  upon  the
          advice of such qualified independent financial advisors
          as  the  Board of Directors may deem to be appropriate,
          and  provided further that any such selection,  opinion
          or  determination  by the Board of Directors  shall  be
          conclusive and binding.

          (j)   "Current Orbital Common Share Equivalent"  means,
          on  any  date, the equivalent as at such  date  of  one
          Orbital   Common  Share  as  at  the  Effective   Date,
          expressed   to  four  decimal  places,  determined   by
          applying   on   a   cumulative  basis   the   following
          adjustments, to the extent applicable by reason of  any
          transactions  occurring in respect  of  Orbital  Common
          Shares  between the Effective Date and such  date,  the
          Current  Orbital  Common Share  Equivalent  as  at  the
          Effective Date being 1.0000:

                           (i)         if   Orbital   shall   (A)
               subdivide, redivide or change its then outstanding
               Orbital  Common  Shares into a greater  number  of
               Orbital  Common Shares, unless the Corporation  is
               permitted under applicable law without a  vote  of
               its shareholders to make, and shall simultaneously
               make,  the  same  or  an  economically  equivalent
               change   to   the   rights  of  the   holders   of
               Exchangeable   Shares,   (B)   reduce,    combine,
               consolidate or change its then outstanding Orbital
               Common  Shares  into a lesser  number  of  Orbital
               Common Shares, unless the Corporation is permitted
               under  applicable  law  without  a  vote  of   its
               shareholders  to  make, and  shall  simultaneously
               make,  the  same  or  an  economically  equivalent
               change   to   the   rights  of  the   holders   of
               Exchangeable  Shares, or (C) issue Orbital  Common
               Shares  (or securities exchangeable or convertible
               into Orbital Common Shares) to the holders of  all
               or  substantially  all  of  its  then  outstanding
               Orbital Common Shares by way of stock dividend  or
               other  distribution  (other  than  to  holders  of
               Orbital  Common Shares who exercise an  option  to
               receive stock dividends in lieu of receiving  cash
               dividends),  unless the Corporation  is  permitted
               under  applicable  law  without  a  vote  of   its
               shareholders  to  issue or distribute,  and  shall
               simultaneously  issue  and distribute,  equivalent
               numbers   of  Orbital  Common  Shares   or   other
               securities  (adjusted if necessary  in  accordance
               with the Current Orbital Common Share Equivalent),
               or  the  economic equivalent on a per share basis,
               to  the holders of the Exchangeable Shares (any of
               such events being herein called an "Orbital Common
               Share Reorganization"), the Current Orbital Common
               Share   Equivalent  shall  be  adjusted  effective
               immediately  after the record date  at  which  the
               holders  of  Orbital Common Shares are  determined
               for  the  purpose  of  the  Orbital  Common  Share
               Reorganization by multiplying the Current  Orbital
               Common  Share Equivalent in effect on such  record
               date by the quotient obtained when:

                                          (I)    the  number   of
                    Orbital  Common Shares outstanding after  the
                    completion  of  such  Orbital  Common   Share
                    Reorganization (but before giving  effect  to
                    the issue of any Orbital Common Shares issued
                    after such record date otherwise than as part
                    of  such Orbital Common Share Reorganization)
                    including,   in  the  case  where  securities
                    exchangeable  or  convertible  into   Orbital
                    Common Shares are distributed, the number  of
                    Orbital  Common Shares that would  have  been
                    outstanding   had   such   securities    been
                    exchanged  for  or  converted  into   Orbital
                    Common Shares on such record date,

             is divided by

                                          (II)   the  number   of
                    Orbital  Common  Shares outstanding  on  such
                    record  date  before  giving  effect  to  the
                    Orbital Common Share Reorganization;

                          (ii)       if at any time Orbital shall
               fix  a  record  date for the issuance  of  rights,
               options  or  warrants to the  holders  of  all  or
               substantially  all  of the Orbital  Common  Shares
               entitling  them  to subscribe for or  to  purchase
               Orbital  Common Shares (or securities  of  Orbital
               convertible into Orbital Common Shares) at a price
               per  Orbital Common Share (or having a  conversion
               price  per Orbital Common Share) of less than  the
               Pre-Dilution  Market Price on  such  record  date,
               unless   the   Corporation  is   permitted   under
               applicable  law without a vote of its shareholders
               to   issue,   and   shall  simultaneously   issue,
               equivalent  numbers  of such  rights,  options  or
               warrants, adjusted if necessary in accordance with
               the  Current  Orbital Common Share  Equivalent  at
               such  record  date,  or  the  economic  equivalent
               thereof  on  a per share basis, to the holders  of
               Exchangeable  Shares (any such event being  herein
               referred  to  as  a "Rights Offering"),  then  the
               Current  Orbital Common Share Equivalent  then  in
               effect  shall be adjusted immediately  after  such
               record  date  by  multiplying the Current  Orbital
               Common  Share Equivalent in effect on such  record
               date by the quotient obtained when:

                                          (A)   the  sum  of  the
                    number  of  Orbital Common Shares outstanding
                    on   such  record  date  and  the  number  of
                    additional Orbital Common Shares offered  for
                    subscription  or  purchase under  the  Rights
                    Offering  (or  the number of  Orbital  Common
                    Shares  into which the securities so  offered
                    are convertible)

          is divided by

                                          (B)   the  sum  of  the
                    number  of  Orbital Common Shares outstanding
                    on such record date and the number determined
                    by  dividing the aggregate price of the total
                    number  of  additional Orbital Common  Shares
                    offered  for  subscription or purchase  under
                    the   Rights   Offering  (or  the   aggregate
                    conversion    price   of   the    convertible
                    securities  so  offered) by the  Pre-Dilution
                    Market Price on such record date.

                                   Any Orbital Common Share owned
               by  or  held for the account of Orbital  shall  be
               deemed  not  to be outstanding for the purpose  of
               any such computation.  If such rights, options  or
               warrants are not so issued or if, at the  date  of
               expiry  of the rights, options or warrants subject
               to  the Rights Offering, less than all the rights,
               options or warrants have been exercised, then  the
               Current  Orbital Common Share Equivalent shall  be
               readjusted effective immediately after the date of
               expiry   to  the  Current  Orbital  Common   Share
               Equivalent which would have been in effect if such
               record  date had not been fixed or to the  Current
               Orbital  Common Share Equivalent which would  then
               be  in  effect on the date of expiry if  the  only
               rights, options or warrants issued had been  those
               that were exercised, as the case may be;

                          (iii)     if Orbital shall fix a record
               date for the making of a distribution (including a
               distribution  by  way of stock  dividend)  to  the
               holders   of   all   or  substantially   all   its
               outstanding Orbital Common Shares of

                                        (A)  shares of Orbital of
                    any  class  other than Orbital Common  Shares
                    (or  shares  convertible into Orbital  Common
                    Shares referred to in (i) (C) above),

                                         (B)  rights, options  or
                    warrants (excluding a Rights Offering),

                                         (C)   evidences  of  its
                    indebtedness      (excluding     indebtedness
                    convertible   into  Orbital   Common   Shares
                    referred to in (i) (C) above) or

                                         (D)   any  other  assets
                    (other than any of the distributions referred
                    to  in (A), (B) or (C), dividends paid in the
                    ordinary  course or an Orbital  Common  Share
                    Reorganization)

                                     unless  the  Corporation  is
               permitted under applicable law without a  vote  of
               its   shareholders   to  distribute,   and   shall
               simultaneously  distribute,  the  same  number  of
               shares, rights, options or warrants, evidences  of
               indebtedness or other assets, as the case may  be,
               adjusted  if  necessary  in  accordance  with  the
               Current Orbital Common Share Equivalent as at such
               record date, or the economic equivalent thereof on
               a  per share basis, to the holders of Exchangeable
               Shares (any such event being herein referred to as
               a "Special Distribution") then, in each such case,
               the  Current Orbital Common Share Equivalent shall
               be adjusted effective immediately after the record
               date at which the holders of Orbital Common Shares
               are  determined  for the purposes of  the  Special
               Distribution  by  multiplying the Current  Orbital
               Common  Share Equivalent in effect on such  record
               date by the quotient obtained when:

                                        (I)  the product obtained
                    when  the  number  of Orbital  Common  Shares
                    outstanding on the record date is  multiplied
                    by  the  Pre-Dilution Market  Price  on  such
                    date,

             is divided by

                                          (II)   the   difference
                    obtained   when  the  amount  by  which   the
                    aggregate fair market value (as determined by
                    the  Board  of Directors, which determination
                    shall  be conclusive) of the shares,  rights,
                    options,  warrants, evidences of indebtedness
                    or assets, as the case may be, distributed in
                    the  Special  Distribution exceeds  the  fair
                    market  value (as determined by the Board  of
                    Directors,  which  determination   shall   be
                    conclusive)  of  the consideration,  if  any,
                    received  therefor by Orbital, is  subtracted
                    from the product obtained when the number  of
                    Orbital  Common  Shares  outstanding  on  the
                    record date is multiplied by the Pre-Dilution
                    Market Price on such date,

                provided that no such adjustment shall be made if
          the  result of such adjustment would be to decrease the
          Current  Orbital  Common  Share  Equivalent  in  effect
          immediately  before  such  record  date.   Any  Orbital
          Common  Share  owned  by or held  for  the  account  of
          Orbital  shall be deemed not to be outstanding for  the
          purpose of any such computation.  Such adjustment shall
          be  made  successively whenever such a record  date  is
          fixed.  To the extent that such distribution is not  so
          made, the Current Orbital Common Share Equivalent shall
          be  readjusted  effective immediately  to  the  Current
          Orbital Common Share Equivalent which would then be  in
          effect  based  upon such shares or rights,  options  or
          warrants   or  evidences  of  indebtedness  or   assets
          actually distributed.

          (k)   "Effective Date" has the meaning ascribed thereto
          in the Plan of Arrangement.

          (l)    "Exchangeable  Shares"  mean  the   Exchangeable
          Non-Voting Shares of the Corporation having the rights,
          privileges,  restrictions  and  conditions  set   forth
          herein.

          (m)   "Lien"  has the meaning ascribed thereto  in  the
          Plan of Arrangement.

          (n)   "Liquidation  Amount" has  the  meaning  ascribed
          thereto in section 4.1 of these share provisions.

          (o)   "Liquidation Call Right" has the meaning ascribed
          thereto in section 5.2 of the Plan of Arrangement.

          (p)  "NASDAQ" means the NASDAQ National Market System;

          (q)    "Liquidation  Date"  has  the  meaning  ascribed
          thereto in section 4.1 of these share provisions.

          (r)   "Orbital"  means Orbital Sciences Corporation,  a
          corporation  organized and existing under the  laws  of
          the State of Delaware, and any successor corporation.

          (s)   "Orbital  Call Notice" has the  meaning  ascribed
          thereto   in   subsection  5.1(b)  of   the   Plan   of
          Arrangement.

          (t)   "Orbital  Common  Share Reorganization"  has  the
          meaning ascribed thereto in subsection 1.1(j) of  these
          share provisions.

          (u)   "Orbital Common Shares" mean the shares of common
          stock  of  Orbital, with a par value  of  U.S.$.01  per
          share  and  having one vote per share,  and  any  other
          securities into which such shares may be changed.

          (v)  "Orbital Dividend Declaration Date" means the date
          on which the Board of Directors of Orbital declares any
          dividend on the Orbital Common Shares.

          (w)   "Orbital  Special Share" means the one  share  of
          Special  Voting Preferred Stock of Orbital with  a  par
          value  of U.S.$.01 and having voting rights at meetings
          of holders of Orbital Common Shares equal to the number
          of  Exchangeable Shares outstanding from time  to  time
          (other than Exchangeable Shares held by Orbital and its
          Affiliates) to be issued to, and voted by, the  Trustee
          pursuant to the Voting Trust and Exchange Agreement.

          (x)    "Plan   of  Arrangement"  means  the   plan   of
          arrangement   relating  to  the  arrangement   of   the
          Corporation  under section 192 of the  CBCA,  to  which
          plan these share provisions are attached.

          (y)   "Pre-Dilution Market Price" means, in respect  of
          an  Orbital  Common  Share on any  date,  the  Canadian
          Dollar  Equivalent of the average of the  closing  sale
          prices  as reported on NASDAQ of such shares  during  a
          period  of  20 consecutive trading days ending  on  the
          fourth  trading  day prior to such  date,  or,  if  the
          Orbital Common Shares are not then quoted on NASDAQ, on
          such other stock exchange or automated quotation system
          on which the Orbital Common Shares are listed or quoted
          as  may be selected by the Board of Directors for  such
          purpose;  provided, however, that if in the opinion  of
          the  Board  of  Directors  the public  distribution  or
          trading  activity of Orbital Common Shares during  such
          period does not create a market that reflects the  fair
          market value of an Orbital Common Share, then the  Pre-
          Dilution Market Price of an Orbital Common Share  shall
          be  determined by the Board of Directors based upon the
          advice of such qualified independent financial advisors
          as  the  Board of Directors may deem to be appropriate,
          and  provided further that any such selection,  opinion
          or  determination  by the Board of Directors  shall  be
          conclusive and binding;

          (z)   "Redemption Call Right" has the meaning  ascribed
          thereto in section 5.3 of the Plan of Arrangement.

          (aa)   "Redemption  Price"  has  the  meaning  ascribed
          thereto in section 6.1 of these share provisions.

          (bb)   "Retracted  Shares"  has  the  meaning  ascribed
          thereto in section 5.1 of these share provisions.

          (cc)  "Retraction Call Right" has the meaning  ascribed
          thereto in section 5.1 of the Plan of Arrangement.

          (dd) "Retraction Date" has the meaning ascribed thereto
          in section 5.2 of these share provisions.

          (ee)   "Retraction  Price"  has  the  meaning  ascribed
          thereto in section 5.1 of these share provisions.

          (ff)  "Retraction  Request" has  the  meaning  ascribed
          thereto in section 5.1 of these share provisions.

          (gg) "Rights Offering" has the meaning ascribed thereto
          in subsection 1.1(j) of these share provisions.

          (hh)  "Special  Distribution" has the meaning  ascribed
          thereto in subsection 1.1(j) of these share provisions.

          (ii)  "Support  Agreement" means the Support  Agreement
          between  Orbital and the Corporation, made  as  of  the
          Effective Date.

          (jj)  "Transfer Agent" means Montreal Trust Company  of
          Canada or such other person as may from time to time be
          the  registrar and transfer agent for the  Exchangeable
          Shares.

          (kk)  "Trustee"  means  State  Street  Bank  and  Trust
          Company, and any successor trustee appointed under  the
          Voting and Exchange Trust Agreement.

          (ll)  "Voting and Exchange Trust Agreement"  means  the
          Voting   and  Exchange  Trust  Agreement  between   the
          Corporation, Orbital and the Trustee, made  as  of  the
          Effective Date.

1.2       All amounts required to be paid, deposited or delivered
hereunder  shall be paid, deposited or delivered after  deduction
of  any  amount  required by applicable law  to  be  deducted  or
withheld on account of tax and the deduction of such amounts  and
remittance to the applicable tax authorities shall, to the extent
thereof,  satisfy  such requirement to pay,  deposit  or  deliver
hereunder.


                           ARTICLE 2

                 RANKING OF EXCHANGEABLE SHARES

2.1        The  Exchangeable  Shares shall  rank  senior  to  the
Class  B  Preferred Shares and the Common Shares  and  any  other
shares ranking junior to the Exchangeable Shares, with respect to
the  payment of dividends and the distribution of assets  in  the
event  of  the  liquidation, dissolution  or  winding-up  of  the
Corporation,  whether  voluntary or  involuntary,  or  any  other
distribution  of  the  assets  of  the  Corporation   among   its
shareholders for the purpose of winding up its affairs.


                           ARTICLE 3

                           DIVIDENDS

3.1       A holder of an Exchangeable Share shall be entitled  to
receive  and the Board of Directors shall, subject to  applicable
law,  declare a dividend on each Exchangeable Share  (a)  in  the
case of a cash dividend declared on the Orbital Common Shares, in
an  amount  in  cash  for each Exchangeable Share  equal  to  the
Canadian  Dollar  Equivalent on the Orbital Dividend  Declaration
Date  of  the  cash dividend declared on such number  of  Orbital
Common  Shares  as is equal to the Current Orbital  Common  Share
Equivalent on the Orbital Dividend Declaration Date or (b) in the
case of a stock dividend declared on the Orbital Common Shares to
be  paid  in  Orbital  Common Shares, in  such  whole  number  of
Exchangeable  Shares  for the Exchangeable Shares  held  by  each
holder as is equal to the number of Orbital Common Shares  to  be
paid as a dividend per Orbital Common Shares (if such calculation
results in a fraction of an Exchangeable Share, the holder  shall
receive in lieu of such fraction an amount in cash equal  to  the
product  obtained by multiplying the amount that would be payable
in  respect of an equal fraction of an Orbital Common Share as at
the  Orbital Dividend Declaration Date, calculated in  accordance
with  section 9.4, by the Current Orbital Common Share Equivalent
as at such date) or (c) in the case of a dividend declared on the
Orbital  Common Shares to be paid in property other than cash  or
Orbital   Common  Shares  (including  without  limitation   other
securities  of Orbital), in such type and amount of property  for
each  Exchangeable  Share  as  is the  same  as  or  economically
equivalent (as determined by the Board of Directors in accordance
with  section 9.1) to the type and amount of property to be  paid
as a dividend on such number of Orbital Common Shares as is equal
to  the  Current Orbital Common Share Equivalent on  the  Orbital
Dividend Declaration Date.  Such dividends shall be paid  out  of
money,  assets or property of the Corporation properly applicable
to  the  payment of dividends, or out of authorized but  unissued
Exchangeable Shares.

3.2       Cheques of the Corporation payable at par at any branch
of  the bankers of the Corporation shall be issued in respect  of
any cash dividends contemplated by subsection 3.1(a) hereof or in
respect  of  any  cash  amount payable in lieu  of  a  fractional
Exchangeable  Share  in  connection  with  any  stock   dividends
contemplated by subsection 3.1(b) hereof and the sending of  such
a  cheque  to each holder of an Exchangeable Share shall  satisfy
the  cash dividend represented thereby unless the cheque  is  not
paid on presentation.  Certificates registered in the name of the
registered  holder  of Exchangeable Shares  shall  be  issued  or
transferred  in  respect of any stock dividends  contemplated  by
subsection 3.1(b) hereof and the sending of such a certificate to
each  holder  of  an Exchangeable Share shall satisfy  the  stock
dividend  represented thereby.  Such other  type  and  amount  of
property   in   respect   of   any  dividends   contemplated   by
subsection   3.1(c)  hereof  shall  be  issued,  distributed   or
transferred  by  the  Corporation in  such  manner  as  it  shall
determine  and the issuance, distribution or transfer thereof  by
the  Corporation  to each holder of an Exchangeable  Share  shall
satisfy  the  dividend  represented thereby.   No  holder  of  an
Exchangeable  Share  shall be entitled to recover  by  action  or
other legal process against the Corporation any dividend that  is
represented by a cheque that has not been duly presented  to  the
Corporation's  bankers  for  payment or  that  otherwise  remains
unclaimed  for a period of six years from the date on which  such
dividend was payable.

3.3       The record date for the determination of the holders of
Exchangeable  Shares  entitled to receive  payment  of,  and  the
payment  date  for,  any dividend declared  on  the  Exchangeable
Shares  under section 3.1 hereof shall be the same dates  as  the
record date and payment date, respectively, for the corresponding
dividend declared on the Orbital Common Shares.

3.4        If  on any payment date for any dividends declared  on
the  Exchangeable Shares under section 3.1 hereof  the  dividends
are  not  paid  in  full on all of the Exchangeable  Shares  then
outstanding, any such dividends that remain unpaid shall be  paid
on  a  subsequent  date  or  dates determined  by  the  Board  of
Directors on which the Corporation shall have sufficient  moneys,
assets  or  property properly applicable to the payment  of  such
dividends.

3.5         So  long  as  any  of  the  Exchangeable  Shares  are
outstanding,  the Corporation shall not at any time without,  but
may  at  any  time  with,  the approval of  the  holders  of  the
Exchangeable  Shares given as specified in section 8.2  of  these
share provisions:

          (a)   pay any dividends on the Class B Preferred Shares
          or  the  Common  Shares, or any  other  shares  ranking
          junior  to  the Exchangeable Shares, other  than  stock
          dividends  payable in Common Shares or any  such  other
          shares  ranking junior to the Exchangeable  Shares,  as
          the case may be;

          (b)    redeem   or   purchase  or  make   any   capital
          distribution in respect of Class B Preferred Shares  or
          Common Shares or any other shares ranking junior to the
          Exchangeable Shares;

          (c)   redeem  or  purchase  any  other  shares  of  the
          Corporation   ranking  equally  with  the  Exchangeable
          Shares with respect to the payment of dividends  or  on
          any liquidation distribution;

          (d)   issue any Exchangeable Shares other than  (i)  by
          way   of  stock  dividends  to  the  holders  of   such
          Exchangeable Shares, (ii) otherwise pro rata to holders
          of  Exchangeable Shares, (iii) as contemplated  by  the
          Support Agreement or (iv) pursuant to any agreements or
          rights in existence at the Effective Date; or

          (e)   issue any other shares of the Corporation ranking
          equally with or senior to the Exchangeable Shares;

provided that the restrictions in subsections 3.5(a), 3.5(b)  and
3.5(c)  shall  not  apply  if all dividends  on  the  outstanding
Exchangeable Shares corresponding to dividends declared  to  date
on  the  Orbital  Common Shares shall have been declared  on  the
Exchangeable Shares and paid in full.


                           ARTICLE 4

                  DISTRIBUTION ON LIQUIDATION

4.1        In  the  event  of  the  liquidation,  dissolution  or
winding-up  of the Corporation or any other distribution  of  the
assets  of the Corporation among its shareholders for the purpose
of  winding up its affairs, a holder of Exchangeable Shares shall
be  entitled,  subject to applicable law,  to  receive  from  the
assets  of the Corporation in respect of each Exchangeable  Share
held  by  such  holder  on the effective date  (the  "Liquidation
Date") of such liquidation, dissolution or winding-up, before any
distribution  of any part of the assets of the Corporation  among
the holders of the Class B Preferred Shares, the Common Shares or
any  other  shares ranking junior to the Exchangeable Shares,  an
amount per share equal to (a) the Current Market Price multiplied
by  the  Current Orbital Common Share Equivalent,  in  each  case
determined  on the Liquidation Date, which shall be satisfied  in
full  in  respect of all of the Exchangeable Shares held by  such
holder  by the Corporation causing to be delivered to such holder
such  whole  number of Orbital Common Shares as is equal  to  the
product  obtained by multiplying the number of such  Exchangeable
Shares  by  the Current Orbital Common Share Equivalent (together
with  an  amount in lieu of any fractional Orbital  Common  Share
resulting  from  such  calculation  payable  in  accordance  with
section  9.4), plus (b) the aggregate of all declared and  unpaid
dividends  on each such Exchangeable Share up to the  Liquidation
Date (collectively the "Liquidation Amount").

4.2        On or promptly after the Liquidation Date, and subject
to  the  exercise by Orbital of the Liquidation Call  Right,  the
Corporation  shall cause to be delivered to the  holders  of  the
Exchangeable  Shares  the  Liquidation  Amount  for   each   such
Exchangeable  Share  upon  presentation  and  surrender  of   the
certificates representing such Exchangeable Shares, together with
such other documents and instruments as may be required to effect
a  transfer of Exchangeable Shares under the CBCA and the by-laws
of  the Corporation and such additional documents and instruments
as  the  Transfer Agent may reasonably require, at the registered
office of the Corporation or at any office of the Transfer  Agent
as  may  be specified by the Corporation by notice to the holders
of  the  Exchangeable Shares.  Payment of the  total  Liquidation
Amount for such Exchangeable Shares shall be made by delivery  to
each  holder,  at  the  address of the  holder  recorded  in  the
securities  register  of  the Corporation  for  the  Exchangeable
Shares  or by holding for pick-up by the holder at the registered
office of the Corporation or at any office of the Transfer  Agent
as  may  be specified by the Corporation by notice to the holders
of   Exchangeable  Shares,  on  behalf  of  the  Corporation   of
certificates  representing  the  Orbital  Common  Shares  to   be
delivered  in payment thereof (which shares shall be duly  issued
as  fully paid and non-assessable and shall be free and clear  of
any  Liens) and a cheque of the Corporation payable at par at any
branch  of  the  bankers of the Corporation  in  respect  of  any
fractional  Orbital  Common Share and  all  declared  and  unpaid
dividends comprising part of the total Liquidation Amount (or, if
any of such dividends were payable in property, such property  or
property that is the same as or economically equivalent  to  such
property).  On and after the Liquidation Date, the holders of the
Exchangeable   Shares  shall  cease  to  be   holders   of   such
Exchangeable Shares and shall not be entitled to exercise any  of
the rights of holders in respect thereof, other than the right to
receive  the  total  Liquidation  Amount  in  respect  of   their
Exchangeable  Shares,  unless payment of  the  total  Liquidation
Amount  for  such  Exchangeable Shares shall  not  be  made  upon
presentation  and surrender of share certificates  in  accordance
with  the foregoing provisions, in which case the rights  of  the
holders  shall  remain  unaffected until  the  total  Liquidation
Amount  has  been paid in the manner hereinbefore provided.   The
Corporation  shall have the right at any time  on  or  after  the
Liquidation  Date to deposit or cause to be deposited  the  total
Liquidation   Amount  in  respect  of  the  Exchangeable   Shares
represented by certificates that have not at the Liquidation Date
been  surrendered  by the holders thereof in a custodial  account
with  any  chartered bank or trust company in Canada.  Upon  such
deposit  being  made, the rights of the holders  of  Exchangeable
Shares after such deposit shall be limited to receiving the total
Liquidation  Amount  (without  interest)  for  such  Exchangeable
Shares  so deposited, against presentation and surrender  of  the
said  certificates held by them, respectively, in accordance with
the  foregoing provisions.  Upon such payment or deposit  of  the
total  Liquidation Amount, the holders of the Exchangeable Shares
shall thereafter be considered and deemed for all purposes to  be
the holders of the Orbital Common Shares delivered to them.

4.3       After the Corporation has satisfied its obligations  to
pay the holders of the Exchangeable Shares the Liquidation Amount
per  Exchangeable Share pursuant to section 4.1  of  these  share
provisions,  such holders shall not be entitled to share  in  any
further distribution of the assets of the Corporation.


                           ARTICLE 5

          RETRACTION OF EXCHANGEABLE SHARES BY HOLDER

5.1        A  holder of Exchangeable Shares shall be entitled  at
any  time,  subject to the exercise by Orbital of the  Retraction
Call  Right and otherwise upon compliance with the provisions  of
this  Article 5, to require the Corporation to redeem any or  all
of  the Exchangeable Shares registered in the name of such holder
(the  "Retracted Shares") for an amount for each Retracted  Share
equal  to (a) the Current Market Price multiplied by the  Current
Orbital Common Share Equivalent, in each case determined  on  the
Retraction  Date, which shall be satisfied in full in respect  of
the  Retracted Shares by the Corporation causing to be  delivered
to  such holder such whole number of Orbital Common Shares as  is
equal  to  the  product  obtained by multiplying  the  number  of
Retracted  Shares by the Current Orbital Common Share  Equivalent
(together with an amount in lieu of any fractional Orbital Common
Share resulting from such calculation payable in accordance  with
section  9.4),  plus (b) the aggregate of all dividends  declared
and  unpaid  on  each Retracted Share up to the  Retraction  Date
(collectively the "Retraction Price", provided that if the record
date for any such declared and unpaid dividend occurs on or after
the  Retraction Date the Retraction Price shall not include  such
declared  and unpaid dividends).  To effect such redemption,  the
holder  shall present and surrender at any office of the Transfer
Agent listed on Schedule A hereto the certificate or certificates
representing the Exchangeable Shares which the holder desires  to
have  the  Corporation redeem, together with such other documents
and  instruments  as  may be required to  effect  a  transfer  of
Exchangeable  Shares  under  the CBCA  and  the  by-laws  of  the
Corporation and such additional documents and instruments as  the
Transfer Agent may reasonably require, and together with  a  duly
executed  statement (the "Retraction Request")  in  the  form  of
Schedule  A hereto or in such other form as may be acceptable  to
the Transfer Agent:

          (a)   specifying that the holder desires  to  have  the
          Retracted  Shares  represented by such  certificate  or
          certificates redeemed by the Corporation; and

          (b)  acknowledging the Retraction Call Right of Orbital
          to  purchase  all but not less than all  the  Retracted
          Shares directly from the holder and that the Retraction
          Request  shall be deemed to be an irrevocable offer  by
          the  holder to sell the Retracted Shares to Orbital  in
          accordance with the Retraction Call Right.

5.2        Subject  to the exercise by Orbital of the  Retraction
Call  Right,  upon receipt by the Transfer Agent  in  the  manner
specified  in section 5.1 hereof of a certificate or certificates
representing the number of Exchangeable Shares which  the  holder
desires to have the Corporation redeem, together with such  other
documents  and  instruments  as  may  be  required  pursuant   to
section  5.1  and  a  Retraction Request, the  Corporation  shall
redeem the Retracted Shares effective at the close of business on
the  sixth Business Day after the Retraction Request is  received
(the  "Retraction Date") and shall cause to be delivered to  such
holder  the  total Retraction Price with respect to such  shares.
If  only  a  part of the Exchangeable Shares represented  by  any
certificate are redeemed (or purchased by Orbital pursuant to the
Retraction Call Right), a new certificate for the balance of such
Exchangeable Shares shall be issued to the holder at the  expense
of the Corporation.

5.3        Upon  receipt by the Transfer Agent  of  a  Retraction
Request,  the  Transfer  Agent  shall  forthwith  notify  Orbital
thereof.  In order to exercise the Retraction Call Right, Orbital
must  deliver an Orbital Call Notice to the Transfer Agent  prior
to  the expiry of the third Business Day after the receipt by the
Transfer Agent of the Retraction Request.  If Orbital does not so
notify  the  Transfer Agent, the Transfer Agent will  notify  the
holder  as  soon  as possible thereafter that  Orbital  will  not
exercise  the  Retraction Call Right.  If  Orbital  delivers  the
Orbital  Call  Notice before the end of such three  Business  Day
period, the Retraction Request shall thereupon be considered only
to  be  an  offer by the holder to sell the Retracted  Shares  to
Orbital  in accordance with the Retraction Call Right.   In  such
event, the Corporation shall not redeem the Retracted Shares  and
Orbital  shall  purchase from such holder and such  holder  shall
sell  to  Orbital  on  the Retraction Date the  Retracted  Shares
pursuant to the Retraction Call Right.

5.4        If  a  Retraction Request is received by the  Transfer
Agent  pursuant to section 5.1 and Orbital has not exercised  the
Retraction  Call Right, the Corporation shall cause the  Transfer
Agent  to deliver to the holder of the Retracted Shares,  at  the
address of the holder recorded in the securities register of  the
Corporation  for  the  Exchangeable  Shares  or  at  the  address
specified  in the holder's Retraction Request or by  holding  for
pick-up  by  the  holder at the office of the Transfer  Agent  to
which   the   Retraction  Request  was  delivered,   certificates
representing  the  Orbital Common Shares to be delivered  to  the
holder in payment of the total Retraction Price for the Retracted
Shares  (or the portion thereof payable in Orbital Common Shares,
as  the case may be) (which shares shall be duly issued as  fully
paid and non-assessable and shall be free and clear of any Liens)
registered in the name of the holder or in such other name as the
holder may request and a cheque of the Corporation payable at par
at any branch of the bankers of the Corporation in payment of the
remaining portion, if any, of the total Retraction Price (or,  if
any part of the Retraction Price consists of dividends payable in
property,  such  property or property that  is  the  same  as  or
economically equivalent to such property), and such  delivery  of
such certificates and cheque (and property, if any) on behalf  of
the  Corporation  by the Transfer Agent shall  be  deemed  to  be
payment of and shall satisfy and discharge all liability for  the
total   Retraction  Price,  to  the  extent  that  the  same   is
represented by such share certificates and cheque (and  property,
if any), unless such cheque is not paid on due presentation.

5.5        On  and  after the close of business on the Retraction
Date,  the  holder of the Retracted Shares shall cease  to  be  a
holder  of  such  Retracted Shares and shall not be  entitled  to
exercise any of the rights of a holder in respect thereof,  other
than  the  right to receive his proportionate part of  the  total
Retraction  Price,  unless  upon presentation  and  surrender  of
certificates in accordance with the foregoing provisions, payment
of  the  total Retraction Price shall not be made, in which  case
the rights of such holder shall remain unaffected until the total
Retraction  Price  has  been  paid  in  the  manner  hereinbefore
provided.   On and after the close of business on the  Retraction
Date,  provided  that presentation and surrender of  certificates
and  payment  of  the total Retraction Price  has  been  made  in
accordance  with  the foregoing provisions,  the  holder  of  the
Retracted  Shares so redeemed by the Corporation shall thereafter
be  considered and deemed for all purposes to be a holder of  the
Orbital Common Shares delivered to it.

5.6       Notwithstanding any other provision of this Article  5,
the Corporation shall not be obligated to redeem Retracted Shares
specified by a holder in a Retraction Request to the extent  that
such redemption of Retracted Shares would be contrary to solvency
requirements  or  other  provisions of applicable  law.   If  the
Corporation believes that on any Retraction Date it would not  be
permitted  by  any  of  such provisions to redeem  the  Retracted
Shares  tendered for redemption on such date, and  provided  that
Orbital  shall not have exercised the Retraction Call Right  with
respect  to  the  Retracted  Shares,  the  Corporation  shall  be
obligated to redeem Retracted Shares specified by a holder  in  a
Retraction Request only to the extent of the maximum number  that
may be so redeemed (rounded down to a whole number of shares)  as
would not be contrary to such provisions on a pro rata basis  and
shall  notify the holder at least two Business Days prior to  the
Retraction  Date as to the number of Retracted Shares which  will
not  be  redeemed  by the Corporation and the  Corporation  shall
issue  to  each holder of Retracted Shares a new certificate,  at
the expense of the Corporation, representing the Retracted Shares
not  redeemed by the Corporation pursuant to section 5.2  hereof.
The  holder  of  any such Retracted Shares not  redeemed  by  the
Corporation pursuant to section 5.2 of these share provisions  as
a  result  of  solvency requirements of applicable law  shall  be
deemed  by  giving the Retraction Request to require  Orbital  to
purchase such Retracted Shares from such holder pursuant  to  the
Exchange  Right  (as  defined in the Voting  and  Exchange  Trust
Agreement).


                           ARTICLE 6

               REDEMPTION OF EXCHANGEABLE SHARES

6.1        Subject  to  applicable law and if  Orbital  does  not
exercise the Redemption Call Right, the Corporation shall on  the
Automatic   Redemption  Date  redeem  the  whole  of   the   then
outstanding Exchangeable Shares for an amount per share equal  to
(a)  the  Current Market Price multiplied by the Current  Orbital
Common Share Equivalent, in each case determined on the Automatic
Redemption  Date, which shall be satisfied in full in respect  of
all   of   the  Exchangeable  Shares  held  by  each  holder   of
Exchangeable Shares by the Corporation causing to be delivered to
such  holder  such whole number of Orbital Common  Shares  as  is
equal  to the product obtained by multiplying the number of  such
Exchangeable   Shares  by  the  Current  Orbital   Common   Share
Equivalent  (together with an amount in lieu  of  any  fractional
Orbital  Common Share resulting from such calculation payable  in
accordance  with  section 9.4), plus (b)  the  aggregate  of  all
declared  and  unpaid  dividends  thereon  up  to  the  Automatic
Redemption Date (collectively the "Redemption Price").

6.2        On  or after the Automatic Redemption Date and subject
to  the  exercise  by Orbital of the Redemption Call  Right,  the
Corporation  shall cause to be delivered to the  holders  of  the
Exchangeable   Shares  the  Redemption  Price   for   each   such
Exchangeable Share upon presentation and surrender at any  office
of  the  Transfer  Agent  of the certificates  representing  such
Exchangeable  Shares,  together with  such  other  documents  and
instruments   as  may  be  required  to  effect  a  transfer   of
Exchangeable  Shares  under  the CBCA  and  the  by-laws  of  the
Corporation and such additional documents and instruments as  the
Transfer  Agent  may reasonably require.  Payment  of  the  total
Redemption  Price for such Exchangeable Shares shall be  made  by
delivery to each holder, at the address of the holder recorded in
the securities register of the Corporation or by holding for pick
up  by the holder at the registered office of the Corporation  or
at  any  office of the Transfer Agent as may be specified by  the
Corporation  in  such  notice, on behalf of  the  Corporation  of
certificates  representing  the  Orbital  Common  Shares  to   be
delivered  to the holder in payment of the Redemption  Price  (or
the portion thereof payable in Orbital Common Shares, as the case
may  be)  (which  shares shall be duly issued as fully  paid  and
non-assessable and shall be free and clear of any  Liens)  and  a
cheque  of  the Corporation payable at par at any branch  of  the
bankers  of the Corporation in respect of any fractional  Orbital
Common  Share  and  all declared and unpaid dividends  comprising
part  of the total Redemption Price (or, if any of such dividends
are  payable  in  property, such property).   On  and  after  the
Automatic Redemption Date, the holders of the Exchangeable Shares
called  for  redemption  shall  cease  to  be  holders  of   such
Exchangeable Shares and shall not be entitled to exercise any  of
the rights of holders in respect thereof, other than the right to
receive the total Redemption Price for their Exchangeable Shares,
unless   payment   of  the  total  Redemption  Price   for   such
Exchangeable  Shares  shall  not be made  upon  presentation  and
surrender  of  certificates  in  accordance  with  the  foregoing
provisions, in which case the rights of the holders shall  remain
unaffected until the total Redemption Price has been paid in  the
manner  hereinbefore provided.  The Corporation  shall  have  the
right  at any time to deposit or cause to be deposited the  total
Redemption  Price  of  the  Exchangeable  Shares  so  called  for
redemption,   or   of  such  of  the  said  Exchangeable   Shares
represented  by certificates that have not at the  date  of  such
deposit  been  surrendered by the holders thereof  in  connection
with  such  redemption, in a custodial account with any chartered
bank  or trust company in Canada named in such notice.  Upon  the
later  of  such  deposit being made and the Automatic  Redemption
Date,  the  Exchangeable Shares in respect whereof  such  deposit
shall  have  been made shall be redeemed and the  rights  of  the
holders thereof after such deposit or Automatic Redemption  Date,
as  the  case  may  be, shall be limited to receiving  the  total
Redemption  Price  for  such Exchangeable  Shares  so  deposited,
against presentation and surrender of the said certificates  held
by   them,   respectively,  in  accordance  with  the   foregoing
provisions.  Upon such payment or deposit of the total Redemption
Price, the holders of the Exchangeable Shares shall thereafter be
considered  and  deemed for all purposes to  be  holders  of  the
Orbital Common Shares delivered to them.


                           ARTICLE 7

                         VOTING RIGHTS

7.1       Except as required by applicable law and the provisions
of  sections  3.5, 8.1 and 10.2, the holders of the  Exchangeable
Shares shall not be entitled as such to receive notice of  or  to
attend any meeting of the shareholders of the Corporation  or  to
vote at any such meeting.


                           ARTICLE 8

                     AMENDMENT AND APPROVAL

8.1        The  rights, privileges, restrictions  and  conditions
attaching to the Exchangeable Shares may be added to, changed  or
removed  but  only  with  the approval  of  the  holders  of  the
Exchangeable Shares given as hereinafter specified.

8.2        Any  approval given by the holders of the Exchangeable
Shares  to  add  to,  change  or  remove  any  right,  privilege,
restriction or condition attaching to the Exchangeable Shares  or
any other matter requiring the approval or consent of the holders
of   the  Exchangeable  Shares  shall  be  deemed  to  have  been
sufficiently given if it shall have been given in accordance with
applicable  law  subject  to  a  minimum  requirement  that  such
approval  be  evidenced by resolution passed  by  not  less  than
two-thirds  of the votes cast on such resolution at a meeting  of
holders of Exchangeable Shares duly called and held at which  the
holders of at least 50% of the outstanding Exchangeable Shares at
that  time are present or represented by proxy.  If at  any  such
meeting   the   holders  of  at  least  50%  of  the  outstanding
Exchangeable  Shares at that time are not present or  represented
by  proxy within one-half hour after the time appointed for  such
meeting then the meeting shall be adjourned to such date not less
than  10  days thereafter and to such time and place  as  may  be
designated  by  the Chairman of such meeting.  At such  adjourned
meeting the holders of Exchangeable Shares present or represented
by  proxy thereat may transact the business for which the meeting
was  originally  called and a resolution passed  thereat  by  the
affirmative vote of not less than two thirds of the votes cast on
such resolution at such meeting shall constitute the approval  or
consent of the holders of the Exchangeable Shares.


                           ARTICLE 9

       ECONOMIC EQUIVALENCE; CHANGES RELATING TO ORBITAL

9.1        The Board of Directors shall determine, in good  faith
and in its sole discretion (with the assistance of such reputable
and qualified independent financial advisors and/or other experts
as  the Board of Directors may require) economic equivalence  for
the  purposes  of  any  provision herein  that  requires  such  a
determination and each such determination shall be conclusive and
binding on Orbital, where applicable.

9.2        If  at  any time there is a capital reorganization  of
Orbital  that  is  not  provided for in subsection  1.1(j)  or  a
consolidation, merger, arrangement or amalgamation (statutory  or
otherwise) of Orbital with or into another entity (any such event
being   called  a  "Capital  Reorganization"),  any   holder   of
Exchangeable  Shares  whose Exchangeable  Shares  have  not  been
exchanged  for  Orbital  Common Shares  in  accordance  with  the
provisions  hereof  prior to the record  date  for  such  Capital
Reorganization  shall be entitled to receive  and  shall  accept,
upon  any  such  exchange occurring pursuant  to  the  provisions
hereof  at  any  time  after the record  date  for  such  Capital
Reorganization,  in  lieu of the Orbital Common  Shares  that  he
would  otherwise  have been entitled to receive pursuant  to  the
provisions  hereof, the number of shares or other  securities  of
Orbital  or  of  the  body  corporate  resulting,  surviving   or
continuing  from  the Capital Reorganization, or other  property,
that  such holder would have been entitled to receive as a result
of  such  Capital Reorganization if, on the record date,  he  had
been the registered holder of the number of Orbital Common Shares
to   which  he  was  then  entitled  upon  any  exchange  of  his
Exchangeable Shares into Orbital Common Shares in accordance with
the  provisions hereof, subject to adjustment thereafter  in  the
same manner, as nearly as may be possible, as is provided for  in
subsection  1.1(j); provided that no such Capital  Reorganization
shall  be  carried into effect unless all necessary  steps  shall
have  been taken so that each holder of Exchangeable Shares shall
thereafter  be  entitled to receive, upon  any  exchange  of  his
Exchangeable  Shares  pursuant to  the  provisions  hereof,  such
number  of shares or other securities of Orbital or of  the  body
corporate  resulting, surviving or continuing  from  the  Capital
Reorganization, or other property.

9.3       In the case of any reclassification of, or other change
in,  the  outstanding Orbital Common Shares other than  a  Common
Share  Reorganization or a Capital Reorganization,  such  changes
shall be made in the rights attaching to the Exchangeable Shares,
without  any action on the part of the Corporation or the holders
of  the Exchangeable Shares to the extent permitted by applicable
law,  effective immediately following the record  date  for  such
reclassification  or  other change, to the  extent  necessary  to
ensure  that holders of Exchangeable Shares shall be entitled  to
receive,  upon the occurrence at any time after such record  date
of  any  event  whereby they would receive Orbital Common  Shares
pursuant  to  the provisions hereof, such shares,  securities  or
rights  as they would have received if their Exchangeable  Shares
had  been  exchanged for Orbital Common Shares  pursuant  to  the
provisions hereof immediately prior to such record date,  subject
to  adjustment thereafter in the same manner, as nearly as may be
possible, as is provided for in subsection 1.1(j).

9.4         No  certificates  or  scrip  representing  fractional
Orbital   Common  Shares  shall  be  delivered  to   holders   of
Exchangeable Shares pursuant to the provisions hereof.   In  lieu
of  any  such  fractional security, each  person  entitled  to  a
fractional  interest in an Orbital Common Share will  receive  an
amount  of  cash  (rounded to the nearest  whole  cent),  without
interest,  equal  to  the Canadian Dollar Equivalent  as  of  the
fourth  Business Day prior to the relevant date  of  delivery  of
certificates representing Orbital Common Shares (the  "Fractional
Share  Calculation  Date") of the product of (i)  such  fraction,
multiplied  by  (ii)  the closing sale price  of  Orbital  Common
Shares  as reported on NASDAQ on the Fractional Share Calculation
Date.


                           ARTICLE 10

       ACTIONS BY THE CORPORATION UNDER SUPPORT AGREEMENT

10.1       The Corporation will take all such actions and do  all
such  things  as shall be necessary or advisable to  perform  and
comply  with and to ensure performance and compliance by  Orbital
with  all provisions of the Support Agreement and the Voting  and
Exchange  Trust  Agreement  applicable  to  the  Corporation  and
Orbital,  respectively,  in accordance  with  the  terms  thereof
including, without limitation, taking all such actions and  doing
all such things as shall be necessary or advisable to enforce  to
the  fullest  extent  possible for  the  direct  benefit  of  the
Corporation and the holders of Exchangeable Shares all rights and
benefits in favour of the Corporation under or pursuant  to  such
agreements.

10.2       The  Corporation  shall  not  propose,  agree  to   or
otherwise  give  effect  to  any  amendment  to,  or  waiver   or
forgiveness  of  its  rights or obligations  under,  the  Support
Agreement and the Voting and Exchange Trust Agreement without the
approval  of  the  holders of the Exchangeable  Shares  given  in
accordance with section 8.2 of these share provisions other  than
such  amendments, waivers and/or forgiveness as may be  necessary
or advisable for the purposes of:

          (a)   adding  to  the covenants of the other  party  or
          parties  to  such agreement for the protection  of  the
          Corporation or the holders of Exchangeable Shares; or

          (b)    making  such  provisions  or  modifications  not
          inconsistent  with such agreements as may be  necessary
          or  desirable  with  respect to  matters  or  questions
          arising  thereunder which, in the opinion of the  Board
          of  Directors,  it may be expedient to  make,  provided
          that  the  Board of Directors shall be of the  opinion,
          after  consultation with counsel, that such  provisions
          and  modifications  will  not  be  prejudicial  to  the
          interests of the holders of the Exchangeable Shares; or

          (c)   making  such  changes in or corrections  to  such
          agreements  which,  on the advice  of  counsel  to  the
          Corporation, are required for the purpose of curing  or
          correcting  any  ambiguity or  defect  or  inconsistent
          provision  or clerical omission or mistake or  manifest
          error  contained therein, provided that  the  Board  of
          Directors  shall be of the opinion, after  consultation
          with counsel, that such changes or corrections will not
          be  prejudicial to the interests of the holders of  the
          Exchangeable Shares.


                           ARTICLE 11

                             LEGEND

11.1       The  certificates evidencing the  Exchangeable  Shares
shall  contain or have affixed thereto a legend, in form  and  on
terms  approved  by the Board of Directors, with respect  to  the
Support  Agreement,  the provisions of the  Plan  of  Arrangement
relating to the Retraction Call Right, the Liquidation Call Right
and  the Redemption Call Right, and the Voting and Exchange Trust
Agreement  (including the provisions with respect to  the  voting
rights, exchange right and automatic exchange thereunder).


                           ARTICLE 12

                            NOTICES

12.1       Any notice, request or other communication to be given
to the Corporation by a holder of Exchangeable Shares shall be in
writing  and  shall  be  valid and effective  if  given  by  mail
(postage prepaid) or by telecopy or by delivery to the registered
office  of the Corporation and addressed to the attention of  the
President.   Any such notice, request or other communication,  if
given by mail, telecopy or delivery, shall only be deemed to have
been  given  and  received upon actual  receipt  thereof  by  the
Corporation.

12.2            Any  presentation and surrender by  a  holder  of
Exchangeable Shares to the Corporation or the Transfer  Agent  of
certificates representing Exchangeable Shares in connection  with
the liquidation, dissolution or winding up of the Corporation  or
the retraction or redemption of Exchangeable Shares shall be made
by  registered  mail  (postage prepaid) or  by  delivery  to  the
registered  office of the Corporation or to such  office  of  the
Transfer  Agent as may be specified by the Corporation,  in  each
case  addressed  to  the  attention  of  the  President  of   the
Corporation.  Any such presentation and surrender of certificates
shall  only be deemed to have been made and to be effective  upon
actual  receipt thereof by the Corporation or the Transfer Agent,
as  the  case  may  be.  Any such presentation and  surrender  of
certificates made by registered mail shall be at the sole risk of
the holder mailing the same.

12.3       Any notice, request or other communication to be given
to  a  holder  of  Exchangeable Shares by or  on  behalf  of  the
Corporation shall be in writing and shall be valid and  effective
if  given by mail (postage prepaid) or by delivery to the address
of  the  holder  recorded  in  the  securities  register  of  the
Corporation  or, in the event of the address of any  such  holder
not  being  so recorded, then at the last known address  of  such
holder.   Any  such  notice, request or other  communication,  if
given by mail, shall be deemed to have been given and received on
the  fifth  Business Day following the date of  mailing  and,  if
given  by  delivery,  shall be deemed  to  have  been  given  and
received on the date of delivery.  Accidental failure or omission
to give any notice, request or other communication to one or more
holders  of Exchangeable Shares shall not invalidate or otherwise
alter  or  affect  any action or proceeding to be  taken  by  the
Corporation pursuant thereto.


      PROVISIONS ATTACHING TO THE CLASS B PREFERRED SHARES

           The  Class  B Preferred Shares in the capital  of  the
Corporation  shall  have attached thereto the  following  rights,
privileges, restrictions and conditions:

Dividends

           Subject  to  the prior rights of the  holders  of  the
Exchangeable  Shares and any other shares ranking senior  to  the
Class  B Preferred Shares with respect to priority in the payment
of  dividends, the holders of Class B Preferred Shares  shall  be
entitled  to  receive  dividends and the  Corporation  shall  pay
dividends  thereon,  as  and  when  declared  by  the  Board   of
Directors,  in  the amount of $0.10 per share per  annum  payable
quarterly on March 31, June 30, September 30 and December  31  in
each  year  (each  a "Dividend Payment Date") in  arrears.   Such
dividends shall be cumulative dividends and shall accrue from the
date  of issue, or from the most recent Dividend Payment Date  on
which dividends were paid, to and including the date to which the
computation of dividends is to be made.  A cheque for the  amount
of  the  dividend less any required deduction shall be mailed  by
first  class  mail  to  the addresses of the  registered  holders
thereof.

Redemption by the Corporation

           The Corporation may, upon giving notice as hereinafter
provided, redeem at any time the whole, but not a part  only,  of
the then outstanding Class B Preferred Shares on payment for each
share  to be redeemed of a sum of $1.00 together with all accrued
unpaid preferential cumulative cash dividends thereon whether  or
not declared (the "Redemption Amount").

           In  the case of redemption of Class B Preferred Shares
under  the  provisions  of the foregoing  paragraph  hereof,  the
Corporation shall at least 20 days before the date specified  for
redemption  mail to each person who at the date of mailing  is  a
registered  holder of Class B Preferred Shares to be  redeemed  a
notice  in writing of the intention of the Corporation to  redeem
such  Class B Preferred Shares.  Such notice shall be  mailed  by
letter,  postage prepaid, addressed to each such  shareholder  at
his  address  as  it appears on the records of  the  Corporation;
provided,  however,  that accidental failure  to  give  any  such
notice  to one or more of such shareholders shall not affect  the
validity  of  such  redemption.  Such notice shall  set  out  the
Redemption  Amount and the date on which redemption  is  to  take
place.   On  or  after the date so specified for redemption,  the
Corporation shall pay or cause to be paid to or to the  order  of
the  registered  holders of the Class B Preferred  Shares  to  be
redeemed  the  Redemption  Amount  thereof  on  presentation  and
surrender  of the certificates representing the Class B Preferred
Shares  called  for redemption at the registered  office  of  the
Corporation,  or  any  other place or places  designated  in  the
notice  of  redemption.   On and after  the  date  specified  for
redemption in any such notice the Class B Preferred Shares called
for  redemption shall cease to be entitled to dividends  and  the
holders  thereof  shall not be entitled to exercise  any  of  the
rights  of shareholders in respect thereof unless payment of  the
Redemption  Amount  shall  not  be  made  upon  presentation   of
certificates  in  accordance with the  foregoing  provisions,  in
which   case   the  rights  of  the  shareholders  shall   remain
unaffected.

           The Corporation shall have the right at any time after
the  mailing  of notice of its intention to redeem  any  Class  B
Preferred  Shares  as aforesaid to deposit the Redemption  Amount
for  the shares so called for redemption or for such of the  said
shares  represented by certificates as have not at  the  date  of
such   deposit  been  surrendered  by  the  holders  thereof   in
connection  with  such  redemption to  a  special  account  in  a
specified  chartered  bank in Canada, named  in  such  notice  of
redemption, to be paid without interest to or to the order of the
respective  holders of such Class B Preferred Shares  called  for
redemption  upon presentation and surrender to such bank  of  the
certificates  representing the same and upon such  deposit  being
made  or  upon the date specified for redemption in such  notice,
whichever  is the later, the Class B Preferred Shares in  respect
whereof such deposit shall have been made shall be deemed  to  be
redeemed  and the rights of the holders thereof shall be  limited
to  receiving without interest their proportionate  part  of  the
total  Redemption  Amount so deposited against  presentation  and
surrender  of  the  said certificates held by them  respectively.
Any  interest  allowed on any such deposit shall  belong  to  the
Corporation.  Redemption moneys that are represented by a  cheque
which  has  not been presented to the Corporation's  bankers  for
payment or that otherwise remain unclaimed (including moneys held
on  deposit  to a special account as provided for  above)  for  a
period of 6 years from the date specified for redemption shall be
forfeited to the Corporation.

Redemption at the Option of the Holders of the Class B  Preferred
Shares

           Every  registered holder of Class B  Preferred  Shares
may,  at  his  option  and  in the manner  hereinafter  provided,
require  the  Corporation to redeem at any time after  the  fifth
anniversary of the Effective Date all, but not part only, of  the
Class  B  Preferred Shares held by such holder upon  payment  for
each share to be redeemed of the Redemption Amount.

           In  the  case of the redemption of Class  B  Preferred
Shares under the provisions of this paragraph, the holder thereof
shall surrender the certificate or certificates representing such
Class  B  Preferred  Shares  at  the  registered  office  of  the
Corporation  accompanied  by  a notice  in  writing  (hereinafter
called a "redemption notice") signed by such holder requiring the
Corporation  to  redeem all, but not part only, of  the  Class  B
Preferred  Shares represented thereby.  As soon as is practicable
following  receipt of a redemption notice, the Corporation  shall
pay  or  cause  to be paid to or to the order of  the  registered
holder  of  the  Class  B Preferred Shares  to  be  redeemed  the
Redemption Amount thereof.

Dissolution

           In  the  event  of  the  dissolution,  liquidation  or
winding-up  of the Corporation, whether voluntary or involuntary,
or  any other distribution of assets of the Corporation among its
shareholders  for the purpose of winding up its affairs,  subject
to the prior rights of the holders of the Exchangeable Shares and
any  other shares ranking senior to the Class B Preferred  Shares
with  respect  to  priority in the distribution  of  assets  upon
dissolution, liquidation or winding-up, the holders of the  Class
B  Preferred Shares shall be entitled to receive an amount  equal
to  the  Redemption  Amount in respect of the Class  B  Preferred
Shares and any cumulative dividends remaining unpaid, whether  or
not  declared.   After  payment to the holders  of  the  Class  B
Preferred  Shares  of  such amounts, such holders  shall  not  be
entitled  to share in any further distribution of the  assets  of
the Corporation.

Voting Rights

           Except  where  specifically  provided  by  the  Canada
Business  Corporations Act, the holders of the Class B  Preferred
Shares  shall not be entitled to receive notice of or  to  attend
meetings of the shareholders of the Corporation and shall not  be
entitled  to  vote  at  any  meeting  of  shareholders   of   the
Corporation.


  PROVISIONS ATTACHING TO THE COMMON SHARES OF THE CORPORATION


           The  common  shares in the capital of the  Corporation
shall  have  attached  thereto the following rights,  privileges,
restrictions and conditions:

Dividends

           Subject  to  the prior rights of the  holders  of  the
Exchangeable Shares, the Class B Preferred Shares and  any  other
shares  ranking  senior  to the common  shares  with  respect  to
priority  in  the  payment of dividends, the  holders  of  common
shares shall be entitled to receive dividends and the Corporation
shall pay dividends thereon, as and when declared by the Board of
Directors  out  of moneys properly applicable to the  payment  of
dividends,  in  such  amount and in such form  as  the  Board  of
Directors may from time to time determine and all dividends which
the Board of Directors may declare on the common shares shall  be
declared and paid in equal amounts per share on all common shares
at the time outstanding.

Dissolution

           In  the  event  of  the  dissolution,  liquidation  or
winding-up  of the Corporation, whether voluntary or involuntary,
or  any other distribution of assets of the Corporation among its
shareholders  for the purpose of winding up its affairs,  subject
to  the  prior rights of the holders of the Exchangeable  Shares,
the  Class B Preferred Shares and any other shares ranking senior
to the common shares with respect to priority in the distribution
of  assets  upon  dissolution,  liquidation  or  winding-up,  the
holders  of  the common shares shall be entitled to  receive  the
remaining property and assets of the Corporation.

Voting Rights

           The holders of the common shares shall be entitled  to
receive  notice of and to attend all meetings of the shareholders
of  the Corporation and shall have one vote for each common share
held  at  all  meetings of the shareholders of  the  Corporation,
except  for  meetings at which only holders of another  specified
class or series of shares of the Corporation are entitled to vote
separately as a class or series.
                           SCHEDULE A

                      NOTICE OF RETRACTION


To  MacDonald  Dettwiler  Holdings Inc. (the  "Corporation")  and
Orbital Sciences Corporation ("Orbital")


           This  notice  is given pursuant to Article  5  of  the
provisions  (the  "Share Provisions") attaching to  the  share(s)
represented  by  this certificate and all capitalized  words  and
expressions  used in this notice that are defined  in  the  Share
Provisions  have  the  meanings  ascribed  to  such   words   and
expressions in such Share Provisions.

           The  undersigned hereby notifies the Corporation that,
subject  to  the  Retraction Call Right referred  to  below,  the
undersigned desires to have the Corporation redeem in  accordance
with Article 5 of the Share Provisions:


     all share(s) represented by this certificate; or


     _______________________ share(s) only.


           The undersigned acknowledges the Retraction Call Right
of  Orbital  to purchase all but not less than all the  Retracted
Shares  from the undersigned and that this notice shall be deemed
to  be an irrevocable offer (subject as hereinafter provided)  by
the  undersigned  to  sell the Retracted  Shares  to  Orbital  in
accordance with the Retraction Call Right on the Retraction  Date
for the Retraction Call Purchase Price and on the other terms and
conditions set out in section 5.1 of the Plan of Arrangement.  If
Orbital determines not to exercise the Retraction Call Right, the
Corporation will notify the undersigned of such fact as  soon  as
possible.

           The  undersigned acknowledges that if, as a result  of
solvency   provisions  of  applicable  law  or   otherwise,   the
Corporation fails to redeem all Retracted Shares, the undersigned
will  be  deemed to have exercised the Exchange Right (as defined
in  the  Voting  and Exchange Trust Agreement) so as  to  require
Orbital to purchase the unredeemed Retracted Shares.

           The undersigned hereby represents and warrants to  the
Corporation and Orbital:

                (i)  that the undersigned has good title to,  and
          owns,  the share(s) represented by this certificate  to
          be  acquired by the Corporation or Orbital, as the case
          may be, free and clear of all Liens; AND

               (ii) either


                                   the undersigned is a
                    resident of Canada for purposes  of
                    the Income Tax Act (Canada); OR

                                    the undersigned  is
                    not   a  resident  of  Canada   for
                    purposes  of  the  Income  Tax  Act
                    (Canada).



The  undersigned hereby acknowledges that, if the undersigned  is
not  a resident of Canada, and has not submitted with this notice
a  certificate issued by Revenue Canada under section 116 of  the
Income  Tax Act (Canada) in respect of the Retracted Shares,  the
amount of any securities or cash resulting from the retraction or
the  purchase  of  the Retracted Shares will be  reduced  by  the
amount  of  withholdings  required  under  the  Income  Tax   Act
(Canada).




____________________  ____________________   ____________________
____                  ______                 ____
       (Date)         (Signature of  Share   (Guarantee of Signat
                      holder)                ure)


     Please  check  box  if  the  securities  and  any  cheque(s)
     resulting  from the retraction or purchase of the  Retracted
     Shares are to be held for pick-up by the shareholder at  the
     principal  transfer  office  of Montreal  Trust  Company  of
     Canada   (the  "Transfer  Agent")  at  510  Burrard  Street,
     Vancouver,  British  Columbia, V6C  3B9  failing  which  the
     securities  and  any cheque(s) will be mailed  to  the  last
     address of the shareholder as it appears on the register.

NOTE:      This  panel  must  be completed and this  certificate,
     together  with  such additional documents  as  the  Transfer
     Agent may require, must be deposited with the Transfer Agent
     at   its  principal  transfer  office  in  Vancouver.    The
     securities  and any cheque(s) resulting from the  retraction
     or  purchase  of  the Retracted Shares will  be  issued  and
     registered in, and made payable to, respectively,  the  name
     of  the  shareholder as it appears on the  register  of  the
     Corporation and the securities and cheque(s) resulting  from
     such  retraction  or  purchase will  be  delivered  to  such
     shareholder  as  indicated above, unless the form  appearing
     immediately below is duly completed.




________________________________________  ______________________
________                                  _____
Name  of Person in Whose Name Securities  Date
or
Cheque(s)  Are To Be Registered,  Issued
or
Delivered (please print)

________________________________________  ______________________
________                                  _____
Street Address or P.O. Box                Signature            of
                                          Shareholder

________________________________________  ______________________
________                                  _____
City-Province                             Signature    Guaranteed
                                          by

NOTE:     If the notice of retraction is for less than all of the
     share(s)  represented  by  this certificate,  a  certificate
     representing the remaining shares of the Corporation will be
     issued and registered in the name of the shareholder  as  it
     appears on the register of the Corporation, unless the Share
     Transfer Power on the share certificate is duly completed in
     respect of such shares.







                          EXHIBIT 2.2


              VOTING AND EXCHANGE TRUST AGREEMENT


           MEMORANDUM  OF AGREEMENT made as of  the       day  of
,  1995.


B E T W E E N:


                  ORBITAL SCIENCES CORPORATION,
                  a  corporation existing under
                  the  laws  of  the  State  of
                  Delaware,

                  (hereinafter referred to as "Orbital"),

                            - and -

                  MacDONALD DETTWILER HOLDINGS INC.,
                  (formerly known as 3173623 Canada Inc.)
                  a  corporation existing under
                  the laws of Canada,

                  (hereinafter referred to as "Corporation"),

                            - and -

                  STATE STREET BANK AND TRUST COMPANY,
                  a  !  existing under the laws
                  of the United States,

                  (hereinafter referred to as "Trustee").



          WHEREAS pursuant to a combination agreement dated as of
August  31,  1995 (the "Combination Agreement"), by  and  between
Orbital,  the Corporation and MacDonald, Dettwiler and Associates
Ltd.  ("MDA"), the parties agreed that on the Effective Date  (as
defined   in   the  Combination  Agreement),  Orbital   and   the
Corporation would execute and deliver a Voting and Exchange Trust
Agreement  containing  the  terms and  conditions  set  forth  in
Exhibit 2.2 to the Combination Agreement together with such other
terms  and conditions as may be agreed to by the parties  to  the
Combination Agreement acting reasonably;

            AND   WHEREAS   pursuant  to  an   arrangement   (the
"Arrangement")   effected  by  articles  of   arrangement   dated
,  1995  filed pursuant to the Canada Business Corporations  Act,
each  issued and outstanding common share of MDA (an "MDA  Common
Share") was exchanged directly or indirectly for 0.# of an issued
and  outstanding Exchangeable Non-Voting Share of the Corporation
(the "Exchangeable Shares");

           AND WHEREAS the aforesaid articles of arrangement  set
forth   the   rights,  privileges,  restrictions  and  conditions
(collectively the "Exchangeable Share Provisions")  attaching  to
the Exchangeable Shares;

           AND  WHEREAS  Orbital is to provide voting  rights  in
Orbital  to  each holder (other than Orbital and its  Affiliates)
from time to time of Exchangeable Shares, such voting rights  per
Exchangeable  Share  to be equivalent to the  voting  rights  per
share  of  the  common stock, par value U.S. $.01 per  share,  of
Orbital (the "Orbital Common Shares");

          AND WHEREAS Orbital is to grant to and in favour of the
holders (other than Orbital and its Affiliates) from time to time
of  Exchangeable Shares the right, in the circumstances set forth
herein, to require Orbital to purchase from each such holder  all
or any part of the Exchangeable Shares held by the holder;

           AND  WHEREAS  the  parties desire to make  appropriate
provision  and to establish a procedure whereby voting rights  in
Orbital  shall be exercisable by holders (other than Orbital  and
its  Affiliates) from time to time of Exchangeable Shares by  and
through the Trustee, which will hold legal title to one share  of
Orbital Special Voting Preferred Stock, U.S. $.01 par value  (the
"Orbital  Special Voting Stock"), to which voting  rights  attach
for the benefit of such holders and whereby the rights to require
Orbital  to purchase Exchangeable Shares from the holders thereof
shall  be  exercisable  by such holders  from  time  to  time  of
Exchangeable Shares by and through the Trustee, which  will  hold
legal title to such rights for the benefit of such holders;

           AND  WHEREAS these recitals and any statements of fact
in this Agreement are made by Orbital and the Corporation and not
by the Trustee;

           NOW  THEREFORE  in  consideration  of  the  respective
covenants and agreements provided in this Agreement and for other
good  and valuable consideration (the receipt and sufficiency  of
which are hereby acknowledged), the parties agree as follows:


                           ARTICLE 1

                 DEFINITIONS AND INTERPRETATION

1.1        Definitions.  In this Agreement, the  following  terms
shall have the following meanings:

           "Affiliate"  of  any  person means  any  other  person
directly  or  indirectly  controlling, controlled  by,  or  under
common  control  of,  that  person.  For  the  purposes  of  this
definition, "control" (including, with correlative meanings,  the
terms  "controlling", "controlled by" and "under  common  control
of"),  as applied to any person, means the possession by  another
person,  directly or indirectly, of the power to direct or  cause
the  direction  of  the  management and policies  of  that  first
mentioned  person,  whether  through  the  ownership  of   voting
securities, by contract or otherwise.

           "Arrangement" has the meaning ascribed thereto in  the
recitals hereto.

           "Automatic Exchange Rights" means the benefit  of  the
obligation of Orbital to effect the automatic exchange of  shares
of  Orbital  Common  Shares for Exchangeable Shares  pursuant  to
subsection 5.12(c) hereof.

           "Board  of Directors" means the Board of Directors  of
the Corporation.

           "Business  Day" means a day other than a  Saturday,  a
Sunday  or a day when banks are not open for business in  one  or
both  of  Vancouver,  British Columbia and  the  Commonwealth  of
Virginia.

           "Call Rights" means collectively the Liquidation  Call
Right, the Redemption Call Right and the Retraction Call Right.

           "Canadian  Dollar Equivalent" means in respect  of  an
amount  expressed  in a foreign currency (the  "Foreign  Currency
Amount") at any date the product obtained by multiplying (a)  the
Foreign  Currency  Amount by (b) the noon spot exchange  rate  on
such date for such foreign currency expressed in Canadian dollars
as  reported  by  the Bank of Canada or, in the event  such  spot
exchange  rate is not available, such exchange rate on such  date
for such foreign currency expressed in Canadian dollars as may be
deemed  by  the  Board  of Directors to be appropriate  for  such
purpose.

           "CBCA" means the Canada Business Corporations Act,  as
amended;

           "Current  Market Price" means, in respect  of  Orbital
Common Shares on any date, the Canadian Dollar Equivalent of  the
closing sale price of Orbital Common Shares on such date (or,  if
no  trades of any Orbital Common Shares occurred on such date, on
the last trading day prior thereto on which such trades occurred)
reported on the NASDAQ National Market System, or, if the Orbital
Common  Shares are not then quoted on the NASDAQ National  Market
System,  on  such  other  stock exchange or  automated  quotation
system  on which the Orbital Common Shares are listed or  quoted,
as  the case may be, as may be selected by the Board of Directors
for  such  purpose; provided, however, that if in the opinion  of
the  Board  of  Directors  the  public  distribution  or  trading
activity  of  Orbital Common Shares during such period  does  not
create  a  market that reflects the fair market value of  Orbital
Common  Shares,  then the Current Market Price of Orbital  Common
Shares  shall be determined by the Board of Directors based  upon
the  advice  of such qualified independent financial advisors  as
the  Board of Directors may deem to be appropriate, and  provided
further that any such selection, opinion or determination by  the
Board of Directors shall be conclusive and binding.

           "Current  Orbital  Common Share  Equivalent"  has  the
meaning ascribed thereto in the Exchangeable Share Provisions.

          "Default Event" means any failure, other than by reason
of  an Insolvency Event, of the Corporation to perform any of its
obligations   pursuant  to  the  Exchangeable  Share  Provisions,
including  without  limitation  its  obligation  to  redeem   any
Retracted Shares.

           "Exchange  Right" has the meaning ascribed thereto  in
section 5.1 hereof.

            "Exchangeable  Share  Provisions"  has  the   meaning
ascribed thereto in the recitals hereto.

           "Exchangeable Shares" has the meaning ascribed thereto
in the recitals hereto.

           "Holder  Votes"  has the meaning ascribed  thereto  in
section 4.2 hereof.

           "Holders"  means the registered holders from  time  to
time   of  Exchangeable  Shares,  other  than  Orbital  and   its
Affiliates.

            "Insolvency  Event"  means  the  institution  by  the
Corporation  of any proceeding to be adjudicated  a  bankrupt  or
insolvent or to be dissolved or wound up, or the consent  of  the
Corporation   to  the  institution  of  bankruptcy,   insolvency,
dissolution or winding up proceedings against it, or  the  filing
of  a  petition, answer or consent seeking dissolution or winding
up  under any bankruptcy, insolvency or analogous laws, including
without  limitation  the  Companies  Creditors'  Arrangement  Act
(Canada) and the Bankruptcy and Insolvency Act (Canada), and  the
failure  by  the  Corporation to contest in good faith  any  such
proceedings  commenced  in respect of the Corporation  within  15
days of becoming aware thereof, or the consent by the Corporation
to  the  filing of any such petition or to the appointment  of  a
receiver,  or  the  making  by  the  Corporation  of  a   general
assignment  for  the benefit of creditors, or  the  admission  in
writing  by  the Corporation of its inability to  pay  its  debts
generally  as  they  become  due, or the  Corporation  not  being
permitted,  pursuant to solvency requirements of applicable  law,
to  redeem  any Retracted Shares pursuant to section 5.6  of  the
Exchangeable Share Provisions.

           "Lien" has the meaning ascribed thereto in the Plan of
Arrangement.

           "Liquidation  Call  Right" has  the  meaning  ascribed
thereto in the Plan of Arrangement.

          "Liquidation Event" has the meaning ascribed thereto in
subsection 5.12(a) hereof.

           "Liquidation  Event Effective Date"  has  the  meaning
ascribed thereto in subsection 5.12(c) hereof.

           "List" has the meaning ascribed thereto in section 4.6
hereof.

           "Officer's Certificate" means, with respect to Orbital
or  the Corporation, as the case may be, a certificate signed  by
any  one  of  the  Chairman  of the  Board,  the  President,  any
Vice-President  or  any other senior officer of  Orbital  or  the
Corporation, as the case may be.

           "Orbital  Common  Shares"  has  the  meaning  ascribed
thereto in the recitals hereto.

           "Orbital Consent" has the meaning ascribed thereto  in
section 4.2 hereof.

           "Orbital Meeting" has the meaning ascribed thereto  in
section 4.2 hereof.

          "Orbital Special Voting Stock" has the meaning ascribed
thereto in the recitals hereto.

          "Orbital Successor" has the meaning ascribed thereto in
subsection 10.1(a) hereof.

            "Person"   includes   an   individual,   partnership,
corporation,  company, unincorporated syndicate or  organization,
trust,   trustee,   executor,  administrator  and   other   legal
representative.

           "Plan of Arrangement" means the plan of arrangement of
the Corporation providing for the Arrangement.

           "Redemption  Call  Right"  has  the  meaning  ascribed
thereto in the Plan of Arrangement.

           "Retracted Shares" has the meaning ascribed thereto in
section 5.7 hereof.

           "Retraction  Call  Right"  has  the  meaning  ascribed
thereto in the Plan of Arrangement.

            "Support   Agreement"  means  that  certain   support
agreement  made as of even date herewith between the  Corporation
and Orbital.

          "Trust" means the trust created by this Agreement.

           "Trust  Estate"  means  the Voting  Share,  any  other
securities, the Exchange Right, the Automatic Exchange Rights and
any  money or other property that may be held by the Trustee from
time to time pursuant to this Agreement.

          "Voting Rights" means the voting rights attached to the
Voting Share.

           "Voting Share" means the one share of Orbital  Special
Voting  Stock,  issued  by  Orbital to  and  deposited  with  the
Trustee, which entitles the holder of record to a number of votes
at  meetings  of holders of Orbital Common Shares  equal  to  the
number  of  Exchangeable Shares outstanding from  time  to  time,
other   than  Exchangeable  Shares  held  by  Orbital   and   its
Affiliates,  multiplied  by  the  Current  Orbital  Common  Share
Equivalent at the relevant time.

1.2        Interpretation  not Affected by  Headings,  etc.   The
division of this Agreement into articles, sections and paragraphs
and  the  insertion of headings are for convenience of  reference
only  and shall not affect the construction or interpretation  of
this Agreement.

1.3        Number,  Gender,  etc.  Words importing  the  singular
number  only  shall  include the plural and  vice  versa.   Words
importing the use of any gender shall include all genders.

1.4        Date for any Action.  If any date on which any  action
is  required to be taken under this Agreement is not  a  Business
Day,  such  action  shall be required to be  taken  on  the  next
succeeding Business Day.

1.5        Withholding of Tax.  All amounts required to be  paid,
deposited  or  delivered hereunder shall be  paid,  deposited  or
delivered  after deduction of any amount required  by  applicable
law  to  be  deducted  or  withheld on account  of  tax  and  the
deduction  of  such amounts and remittance to the applicable  tax
authorities   shall,   to  the  extent  thereof,   satisfy   such
requirement to pay, deposit or deliver hereunder.


                           ARTICLE 2

                      PURPOSE OF AGREEMENT

2.1        Establishment of Trust.  The purpose of this Agreement
is  to create the Trust for the benefit of the Holders, as herein
provided.   The Trustee will hold the Voting Share  in  order  to
enable  the Trustee to exercise the Voting Rights and  will  hold
the Exchange Right and the Automatic Exchange Rights in order  to
enable  the  Trustee to exercise such rights,  in  each  case  as
trustee  for  and  on behalf of the Holders as provided  in  this
Agreement.


                           ARTICLE 3

                          VOTING SHARE

3.1         Issue   and  Ownership  of  the  Voting  Share.    In
consideration  of  the granting of the Call  Rights  to  Orbital,
Orbital hereby issues to and deposits with the Trustee the Voting
Share  to  be hereafter held of record by the Trustee as  trustee
for and on behalf of, and for the use and benefit of, the Holders
and in accordance with the provisions of this Agreement.  Orbital
hereby  acknowledges receipt from the Trustee as trustee for  and
on  behalf of the Holders of good and valuable consideration (and
the  adequacy  thereof) for the issuance of the Voting  Share  by
Orbital to the Trustee.  During the term of the Trust and subject
to  the terms and conditions of this Agreement, the Trustee shall
possess  and  be vested with full legal ownership of  the  Voting
Share  and  shall be entitled to exercise all of the  rights  and
powers  of  an  owner with respect to the Voting Share,  provided
that the Trustee shall:

                     (a)   hold  the Voting Share and  the  legal
               title  thereto as trustee solely for the  use  and
               benefit  of  the  Holders in accordance  with  the
               provisions of this Agreement; and

                     (b)   except  as specifically authorized  by
               this  Agreement,  have no power  or  authority  to
               sell, transfer, vote or otherwise deal in or  with
               the Voting Share and the Voting Share shall not be
               used or disposed of by the Trustee for any purpose
               other  than the purposes for which this  Trust  is
               created pursuant to this Agreement.

3.2        Legended  Share Certificates.  The  Corporation  shall
cause  each certificate representing Exchangeable Shares to  bear
an  appropriate  legend notifying the Holders of their  right  to
instruct  the Trustee with respect to the exercise of the  Voting
Rights with respect to the Exchangeable Shares held by Holders.

3.3         Safe   Keeping  of  Certificate.    The   certificate
representing the Voting Share shall at all times be held in  safe
keeping by the Trustee.


                           ARTICLE 4

                         VOTING RIGHTS

4.1       Voting Rights.  The Trustee, as the holder of record of
the  Voting Share, shall be entitled to all of the Voting Rights,
including  the  right to consent to or to vote in  person  or  by
proxy  the  Voting Share, on any matter, question or  proposition
whatsoever  that  may  properly come before the  stockholders  of
Orbital  for  their vote at an Orbital Meeting or  in  connection
with  an Orbital Consent.  The Voting Rights shall be and  remain
vested in and exercised by the Trustee.  Subject to section  6.15
hereof, the Trustee shall exercise the Voting Rights only on  the
basis  of instructions received pursuant to this Article  4  from
Holders entitled to instruct the Trustee as to the voting thereof
at  the  time at which an Orbital Consent is sought or an Orbital
Meeting is held.  To the extent that no instructions are received
from  a  Holder with respect to the Voting Rights to  which  such
Holder is entitled, the Trustee shall not exercise or permit  the
exercise of such Holder's Voting Rights.

4.2        Number  of  Votes.  With respect to  all  meetings  of
stockholders of Orbital at which holders of Orbital Common Shares
are  entitled to vote (an "Orbital Meeting") and with respect  to
all  written  consents sought from the holders of Orbital  Common
Shares  (an "Orbital Consent"), each Holder shall be entitled  to
instruct  the  Trustee  to  cast  and  exercise,  in  the  manner
instructed,  such number of votes comprised in the Voting  Rights
as is equal to the Current Orbital Common Share Equivalent on the
record date established by Orbital or by applicable law for  such
Orbital Meeting or Orbital Consent, as the case may be, for  each
Exchangeable Share owned of record by such Holder on such  record
date (the "Holder Votes") in respect of each matter, question  or
proposition  to  be voted on at such Orbital  Meeting  or  to  be
consented to in connection with such Orbital Consent.

4.3       Mailings to Shareholders.  With respect to each Orbital
Meeting  and Orbital Consent, the Trustee shall mail or cause  to
be mailed (or otherwise communicate in the same manner as Orbital
utilizes  in communications to holders of Orbital Common  Shares)
to  each of the Holders named in the List on the same day as  the
initial  mailing of notice (or other communication) with  respect
thereto  is  given  by  Orbital  or  any  third  party   to   its
stockholders:

                    (a)  a copy of such notice, together with any
               proxy   or   information  statement  and   related
               materials  to  be  provided  to  stockholders   of
               Orbital;

                    (b)  a statement that such Holder is entitled
               to  instruct the Trustee as to the exercise of the
               Holder  Votes with respect to such Orbital Meeting
               or  Orbital  Consent,  as the  case  may  be,  or,
               pursuant  to  section 4.7 hereof, to  attend  such
               Orbital  Meeting  and to exercise  personally  the
               Holder Votes thereat;

                     (c)   a statement as to the manner in  which
               such  instructions may be given  to  the  Trustee,
               including  an express indication that instructions
               may be given to the Trustee to give:

                     (d)   a proxy to such Holder or his designee
               to exercise personally the Holder Votes; or

                                          (i)    a  proxy  to   a
                         designated agent or other representative
                         of the management of Orbital to exercise
                         such Holder Votes;

                    (e)  a statement that if no such instructions
               are received from the Holder, the Holder Votes  to
               which   such  Holder  is  entitled  will  not   be
               exercised;

                     (f)   a form of direction whereby the Holder
               may   so  direct  and  instruct  the  Trustee   as
               contemplated herein; and

                     (g)  a statement of (i) the time and date by
               which  such instructions must be received  by  the
               Trustee  in order to be binding upon it, which  in
               the case of a Orbital Meeting shall not be earlier
               than  the close of business on the second Business
               Day prior to such meeting, and (ii) the method for
               revoking or amending such instructions.

For the purpose of determining Holder Votes to which a Holder  is
entitled  in  respect  of  any such Orbital  Meeting  or  Orbital
Consent, the number of Exchangeable Shares owned of record by the
Holder shall be determined at the close of business on the record
date established by Orbital or by applicable law for purposes  of
determining stockholders entitled to vote at such Orbital Meeting
or  to  give  written  consent in connection  with  such  Orbital
Consent.  Orbital shall notify the Trustee of any decision of the
board of directors of Orbital with respect to the calling of  any
such  Orbital  Meeting  or the seeking by  Orbital  of  any  such
Orbital  Consent and shall provide all necessary information  and
materials  to the Trustee in each case promptly and in any  event
in   sufficient  time  to  enable  the  Trustee  to  perform  its
obligations contemplated by this section 4.3.

4.4        Copies  of  Stockholder  Information.   Orbital  shall
deliver  to the Trustee copies of all proxy materials, (including
notices of Orbital Meetings but excluding proxies to vote Orbital
Common   Shares),  information  statements,  reports   (including
without  limitation all interim and annual financial  statements)
and  other  written communications that are to be distributed  by
Orbital from time to time to holders of Orbital Common Shares  in
sufficient quantities and in sufficient time so as to enable  the
Trustee  to send those materials to each Holder at the same  time
as  such  materials are first sent to holders of  Orbital  Common
Shares.  The Trustee shall mail or otherwise send to each Holder,
at  the expense of Orbital, copies of all such materials (and all
materials specifically directed to the Holders or to the  Trustee
for  the  benefit  of  the Holders by Orbital)  received  by  the
Trustee from Orbital at the same time as such materials are first
sent to holders of Orbital Common Shares.  The Trustee shall make
copies  of  all  such materials available for inspection  by  any
Holder at the Trustee's principal office.

4.5        Other Materials.  Immediately after receipt by Orbital
or  any  stockholder  of Orbital of any material  sent  or  given
generally to the holders of Orbital Common Shares by or on behalf
of  a  third party, including without limitation dissident  proxy
and  information circulars (and related information and material)
and  tender and exchange offer circulars (and related information
and  material),  Orbital  shall use all  commercially  reasonable
efforts  to  obtain and deliver to the Trustee copies thereof  in
sufficient quantities so as to enable the Trustee to forward such
material  (unless the same has been provided directly to  Holders
by  such  third  party)  to  each  Holder  as  soon  as  possible
thereafter.   As soon as practicable after receipt  thereof,  the
Trustee  shall  mail  or otherwise send to each  Holder,  at  the
expense of Orbital, copies of all such materials received by  the
Trustee from Orbital.  The Trustee shall also make copies of  all
such  materials  available for inspection by any  Holder  at  the
Trustee's principal office.

4.6        List  of  Persons Entitled to Vote.   The  Corporation
shall,  (a)  prior  to each annual, general and  special  Orbital
Meeting  or the seeking of any Orbital Consent and (b)  forthwith
upon  each  request made at any time by the Trustee  in  writing,
prepare  or cause to be prepared a list (a "List") of  the  names
and  addresses of the Holders arranged in alphabetical order  and
showing the number of Exchangeable Shares held of record by  each
such  Holder, in each case at the close of business on  the  date
specified  by the Trustee in such request or, in the  case  of  a
List prepared in connection with an Orbital Meeting or an Orbital
Consent,  at the close of business on the record date established
by  Orbital  or  pursuant to applicable law for  determining  the
holders  of Orbital Common Shares entitled to receive  notice  of
and/or  to  vote  at such Orbital Meeting or to give  consent  in
connection  with such Orbital Consent.  Each such List  shall  be
delivered   to  the  Trustee  promptly  after  receipt   by   the
Corporation  of such request or the record date for such  meeting
or  seeking  of  consent, as the case may be, and  in  any  event
within  sufficient time as to enable the Trustee to  perform  its
obligations  under this Agreement.  Orbital agrees  to  give  the
Corporation notice (with a copy to the Trustee) of the calling of
any  Orbital  Meeting  or  the seeking of  any  Orbital  Consent,
together  with the record dates therefor, sufficiently  prior  to
the  date  of  the  calling of such meeting or  seeking  of  such
consent   so  as  to  enable  the  Corporation  to  perform   its
obligations under this section 4.6.

4.7        Entitlement to Direct Votes.  Any Holder  named  in  a
List  prepared  in  connection with any Orbital  Meeting  or  any
Orbital Consent shall be entitled (a) to instruct the Trustee  in
the  manner described in section 4.3 hereof with respect  to  the
exercise of the Holder Votes to which such Holder is entitled  or
(b) to attend such meeting and personally to exercise thereat (or
to exercise with respect to any written consent), as the proxy of
the Trustee, the Holder Votes to which such Holder is entitled.

4.8         Voting   by  Trustee,  and  Attendance   of   Trustee
Representative, at Meeting.

                     (a)  In connection with each Orbital Meeting
               and  Orbital Consent, the Trustee shall  exercise,
               either  in person or by proxy, in accordance  with
               the  instructions received from a Holder  pursuant
               to  section  4.3 hereof, the Holder  Votes  as  to
               which  such Holder is entitled to direct the  vote
               (or  any lesser number thereof as may be set forth
               in the instructions); provided, however, that such
               written  instructions are received by the  Trustee
               from  the Holder prior to the time and date  fixed
               by  it  for  receipt of such instructions  in  the
               notice given by the Trustee to the Holder pursuant
               to section 4.3 hereof.

                      (b)    The   Trustee   shall   cause   such
               representatives as are empowered by it to sign and
               deliver,  on  behalf of the Trustee,  proxies  for
               Voting  Rights  to  attend each  Orbital  Meeting.
               Upon  submission by a Holder (or its designee)  of
               identification  satisfactory  to   the   Trustee's
               representatives, and at the Holder's request, such
               representatives  shall sign and  deliver  to  such
               Holder  (or  its  designee) a  proxy  to  exercise
               personally  the  Holder Votes  as  to  which  such
               Holder  is otherwise entitled hereunder to  direct
               the  vote,  if  such  Holder either  (i)  has  not
               previously given the Trustee instructions pursuant
               to  section 4.3 hereof in respect of such meeting,
               or  (ii)  submits to the Trustee's representatives
               written    revocation   of   any   such   previous
               instructions.    At  such  meeting,   the   Holder
               exercising such Holder Votes shall have  the  same
               rights  as the Trustee to speak at the meeting  in
               respect of any matter, question or proposition, to
               vote by way of ballot at the meeting in respect of
               any matter, question or proposition and to vote at
               such  meeting by way of a show of hands in respect
               of any matter, question or proposition.

4.9         Distribution  of  Written  Materials.   Any   written
materials  to  be  distributed by  the  Trustee  to  the  Holders
pursuant to this Agreement shall be delivered or sent by mail (or
otherwise communicated in the same manner as Orbital utilizes  in
communications  to  holders of Orbital  Common  Shares)  to  each
Holder  at  its address as shown on the books of the Corporation.
The  Corporation  shall provide or cause to be  provided  to  the
Trustee for this purpose, on a timely basis and without charge or
other expense:

                    (a)  a List; and

                    (b)  upon the request of the Trustee, mailing
               labels  to  enable the Trustee to  carry  out  its
               duties under this Agreement.

4.10       Termination of Voting Rights.  Except with respect  to
an  Orbital Meeting or Orbital Consent for which the record  date
has  occurred, all of the rights of a Holder with respect to  the
Holder  Votes  exercisable in respect of the Exchangeable  Shares
held  by such Holder, including the right to instruct the Trustee
as  to  the  voting of or to vote personally such  Holder  Votes,
shall  be  deemed to be surrendered by the Holder to Orbital  and
such Holder Votes and the Voting Rights represented thereby shall
cease immediately upon the delivery by such Holder to the Trustee
of  the  certificates  representing such Exchangeable  Shares  in
connection with the exercise by the Holder of the Exchange  Right
or  the  occurrence  of the automatic exchange  pursuant  to  the
Automatic  Exchange Rights (unless in either case  Orbital  shall
not  have  delivered the requisite Orbital Common Shares issuable
in exchange therefor to the Trustee for delivery to the Holders),
or upon the redemption of Exchangeable Shares pursuant to Article
5  or Article 6 of the Exchangeable Share Provisions, or upon the
effective  date of the liquidation, dissolution or winding-up  of
the  Corporation pursuant to Article 4 of the Exchangeable  Share
Provisions, or upon the purchase of Exchangeable Shares from  the
holder thereof by Orbital pursuant to the exercise by Orbital  of
the  Retraction  Call Right, the Redemption  Call  Right  or  the
Liquidation Call Right.

4.11       Issue of Additional Shares.  During the term  of  this
Agreement,  Orbital will not issue any shares of Orbital  Special
Voting Stock, in addition to the Voting Share.


                           ARTICLE 5

             EXCHANGE RIGHT AND AUTOMATIC EXCHANGE

5.1        Grant  and  Ownership  of  the  Exchange  Right.    In
consideration  of  the granting of the Call  Rights  to  Orbital,
Orbital hereby grants to the Trustee as trustee for and on behalf
of,  and  for the use and benefit of, the Holders (a)  the  right
(the  "Exchange  Right"),  upon the  occurrence  and  during  the
continuance of an Insolvency Event or Default Event,  to  require
Orbital  to  purchase from each Holder all or  any  part  of  the
Exchangeable  Shares held by such Holder and  (b)  the  Automatic
Exchange  Rights, all in accordance with the provisions  of  this
agreement.  Orbital hereby acknowledges receipt from the  Trustee
as  trustee for and on behalf of the Holders of good and valuable
consideration  (and the adequacy thereof) for the  grant  of  the
Exchange  Right and the Automatic Exchange Rights by  Orbital  to
the  Trustee.   During the term of the Trust and subject  to  the
terms and conditions of this Agreement, the Trustee shall possess
and be vested with full legal ownership of the Exchange Right and
the  Automatic Exchange Rights and shall be entitled to  exercise
all  of  the  rights and powers of an owner with respect  to  the
Exchange  Right and the Automatic Exchange Rights, provided  that
the Trustee shall:

                      (a)   hold  the  Exchange  Right  and   the
               Automatic  Exchange  Rights and  the  legal  title
               thereto  as trustee solely for the use and benefit
               of  the  Holders in accordance with the provisions
               of this Agreement; and

                     (b)   except  as specifically authorized  by
               this  Agreement,  have no power  or  authority  to
               exercise or otherwise deal in or with the Exchange
               Right  or the Automatic Exchange Rights,  and  the
               Trustee shall not exercise any such rights for any
               purpose  other  than the purposes for  which  this
               Trust is created pursuant to this Agreement.

5.2        Legended  Share Certificates.  The  Corporation  shall
cause  each certificate representing Exchangeable Shares to  bear
an appropriate legend notifying the Holders of:

                    (a)  their right to instruct the Trustee with
               respect  to the exercise of the Exchange Right  in
               respect  of  the  Exchangeable Shares  held  by  a
               Holder; and

                    (b)  the Automatic Exchange Rights.

5.3       General Exercise of Exchange Right.  The Exchange Right
shall  be  and  remain vested in and exercisable by the  Trustee.
Subject  to  section 6.15 hereof, the Trustee shall exercise  the
Exchange  Right  only  on  the  basis  of  instructions  received
pursuant to this Article 5 from Holders entitled to instruct  the
Trustee  as  to  the  exercise thereof.  To the  extent  that  no
instructions  are  received from a Holder  with  respect  to  the
Exchange  Right,  the Trustee shall not exercise  or  permit  the
exercise of the Exchange Right.

5.4        Purchase Price.  The purchase price payable by Orbital
for  each Exchangeable Share to be purchased by Orbital under the
Exchange  Right  shall be an amount per share equal  to  (a)  the
Current  Market  Price multiplied by the Current  Orbital  Common
Share  Equivalent, in each case determined on the day of  closing
of  the  purchase and sale of such Exchangeable Share  under  the
Exchange  Right, which shall be satisfied in full in  respect  of
the Exchangeable Shares in regard to which a Holder has exercised
the Exchange Right by causing to be delivered to such Holder such
whole  number of Orbital Common Shares as is equal to the product
obtained by multiplying the number of such Exchangeable Shares by
the  Current  Orbital Common Share Equivalent (together  with  an
amount  in  lieu of any fractional Orbital Common Share resulting
from  such calculation payable in accordance with section 9.4  of
the Exchangeable Share Provisions), plus (b) the aggregate of all
dividends  declared  and unpaid on each such  Exchangeable  Share
(provided  that  if  the record date for any  such  declared  and
unpaid  dividends occurs on or after the day of closing  of  such
purchase  and  sale  the purchase price shall  not  include  such
declared and unpaid dividends).

5.5        Exercise  Instructions.   Subject  to  the  terms  and
conditions herein set forth, a Holder shall be entitled, upon the
occurrence and during the continuance of an Insolvency Event,  to
instruct the Trustee to exercise the Exchange Right with  respect
to  all or any part of the Exchangeable Shares registered in  the
name  of  such Holder on the books of the Corporation.  To  cause
the  exercise  of the Exchange Right by the Trustee,  the  Holder
shall  deliver  to  the Trustee, in person  or  by  certified  or
registered  mail, at its principal office or at such other  place
as  the Trustee may from time to time designate by written notice
to  the  Holders, the certificates representing the  Exchangeable
Shares  that  such  Holder  desires  Orbital  to  purchase,  duly
endorsed  in  blank, and accompanied by such other documents  and
instruments   as  may  be  required  to  effect  a  transfer   of
Exchangeable  Shares  under  the CBCA  and  the  by-laws  of  the
Corporation and such additional documents and instruments as  the
Trustee may reasonably require together with (a) a duly completed
form  of  notice of exercise of the Exchange Right, contained  on
the   reverse   of   or   attached  to  the  Exchangeable   Share
certificates,  stating (i) that the Holder thereby instructs  the
Trustee  to exercise the Exchange Right so as to require  Orbital
to  purchase  from  the Holder the number of Exchangeable  Shares
specified  therein, (ii) that such Holder has good title  to  and
owns  all such Exchangeable Shares to be acquired by Orbital free
and clear of all Liens, (iii) the names in which the certificates
representing  Orbital Common Shares issuable in  connection  with
the  exercise of the Exchange Right are to be issued and (iv) the
names  and addresses of the persons to whom such new certificates
should be delivered and (b) payment (or evidence satisfactory  to
the Trustee, the Corporation and Orbital of payment) of the taxes
(if   any)  payable  as  contemplated  by  section  5.8  of  this
Agreement.  If only a part of the Exchangeable Shares represented
by  any certificate or certificates delivered to the Trustee  are
to  be  purchased  by  Orbital under the Exchange  Right,  a  new
certificate for the balance of such Exchangeable Shares shall  be
issued to the holder at the expense of the Corporation.

5.6        Delivery of Orbital Common Shares: Effect of Exercise.
Promptly  after  receipt  of  the certificates  representing  the
Exchangeable Shares that the Holder desires Orbital  to  purchase
under  the  Exchange  Right (together  with  such  documents  and
instruments  of transfer and a duly completed form of  notice  of
exercise of the Exchange Right (and payment of taxes, if any,  or
evidence  thereof in accordance with section 5.8)), duly endorsed
for transfer to Orbital, the Trustee shall notify Orbital and the
Corporation of its receipt of the same, which notice  to  Orbital
and  the  Corporation shall constitute exercise of  the  Exchange
Right by the Trustee on behalf of the holder of such Exchangeable
Shares, and Orbital shall immediately thereafter deliver or cause
to  be  delivered to the Trustee, for delivery to the  Holder  of
such  Exchangeable  Shares (or to such  other  persons,  if  any,
properly  designated  by such Holder), the certificates  for  the
number  of Orbital Common Shares issuable in connection with  the
exercise of the Exchange Right, which shares shall be duly issued
as  fully paid and non-assessable and shall be free and clear  of
any  Liens,  and cheques for the balance, if any,  of  the  total
purchase  price  therefor  (or, if part  of  the  purchase  price
consists  of  dividends  payable in property,  such  property  or
property  the  same  as  or  economically  equivalent   to   such
property).  Immediately upon the giving of notice by the  Trustee
to  Orbital  and the Corporation of the exercise of the  Exchange
Right,  as  provided  in this section 5.6,  the  closing  of  the
transaction  of  purchase and sale contemplated by  the  Exchange
Right  shall be deemed to have occurred, and the Holder  of  such
Exchangeable  Shares  shall  be deemed  to  have  transferred  to
Orbital  all  of  its right, title and interest in  and  to  such
Exchangeable  Shares  and in the related interest  in  the  Trust
Estate and shall cease to be a holder of such Exchangeable Shares
and  shall  not be entitled to exercise any of the  rights  of  a
holder  in  respect thereof, other than the right to receive  the
purchase  price therefor, unless the requisite number of  Orbital
Common Shares (together with a cheque for the balance, if any, of
the  purchase  price therefor or, if part of the  purchase  price
consists  of  dividends  payable in property,  such  property  or
property the same as or economically equivalent to such property)
is  not  allotted, issued and delivered by Orbital to the Trustee
for  delivery  to  such  Holder (or to  other  persons,  if  any,
properly designated by such Holder) within five Business Days  of
the  date  of the giving of such notice by the Trustee, in  which
case  the rights of the Holder shall remain unaffected until such
Orbital  Common Shares are so allotted, issued and  delivered  by
Orbital   and  any  such  cheque  is  so  delivered   and   paid.
Concurrently  with  such  Holder  ceasing  to  be  a  holder   of
Exchangeable  Shares, the Holder shall be considered  and  deemed
for  all  purposes to be the holder of the Orbital Common  Shares
delivered to it pursuant to the Exchange Right.

5.7        Exercise  of Exchange Right Subsequent to  Retraction.
In  the event that a Holder has exercised its right under Article
5 of the Exchangeable Share Provisions to require the Corporation
to  redeem  any  or all of the Exchangeable Shares  held  by  the
Holder   (the  "Retracted  Shares")  and  is  notified   by   the
Corporation  pursuant  to section 5.6 of the  Exchangeable  Share
Provisions that the Corporation is not permitted as a  result  of
solvency  requirements of applicable law to redeem  all  of  such
Retracted  Shares,  and  provided that  Orbital  shall  not  have
exercised the Retraction Call Right with respect to the Retracted
Shares,  the  retraction request shall constitute  and  shall  be
deemed  to  constitute  notice from the  Holder  to  the  Trustee
instructing  the  Trustee  to exercise the  Exchange  Right  with
respect to those Retracted Shares that the Corporation is  unable
to redeem.  In any such event, the Corporation hereby agrees with
the Trustee and in favour of the Holder immediately to notify the
Trustee of such prohibition against the Corporation redeeming all
of the Retracted Shares and immediately to forward or cause to be
forwarded to the Trustee all relevant materials delivered by  the
Holder  to  the  Corporation  or to the  transfer  agent  of  the
Exchangeable Shares (including without limitation a copy  of  the
retraction  request  delivered pursuant to  section  5.1  of  the
Exchangeable  Share Provisions) in connection with such  proposed
redemption  of  the  Retracted  Shares  and  the  Trustee   shall
thereupon  exercise  the  Exchange  Right  with  respect  to  the
Retracted Shares that the Corporation is not permitted to  redeem
and  will  require Orbital to purchase such shares in  accordance
with the provisions of this Article 5.

5.8        Stamp  or  Other Transfer Taxes.   Upon  any  sale  of
Exchangeable Shares to Orbital pursuant to the Exchange Right  or
the   Automatic   Exchange  Rights,  the  share  certificate   or
certificates  representing Orbital Common Shares to be  delivered
in  connection  with the payment of the purchase  price  therefor
shall  be  issued  in the name of the Holder of the  Exchangeable
Shares  so  sold  or in such names as such Holder  may  otherwise
direct   in  writing  without  charge  to  the  holder   of   the
Exchangeable Shares so sold, provided, however, that such  Holder
(a)  shall  pay  (and  neither Orbital, the Corporation  nor  the
Trustee  shall  be  required  to  pay)  any  documentary,  stamp,
transfer or other similar taxes that may be payable in respect of
any  transfer involved in the issuance or delivery of such shares
to  a person other than such Holder or (b) shall establish to the
satisfaction  of  the Trustee, Orbital and the  Corporation  that
such taxes, if any, have been paid.

5.9         Notice   of   Insolvency  Event  or  Default   Event.
Immediately upon the occurrence of an Insolvency Event or Default
Event  or any event that with the giving of notice or the passage
of  time  or both would be an Insolvency Event or Default  Event,
the Corporation and Orbital shall give written notice thereof  to
the  Trustee.  As soon as practicable after receiving notice from
the  Corporation  and  Orbital or from any other  person  of  the
occurrence  of an Insolvency Event or Default Event, the  Trustee
shall mail to each Holder, at the expense of Orbital, a notice of
such  Insolvency  Event  or  Default Event,  which  notice  shall
contain  a  brief  statement of the right  of  the  Holders  with
respect to the Exchange Right.

5.10       Qualification  of Orbital Common Shares.   Unless  the
staff  of  the  United States Securities and Exchange  Commission
(the  "SEC") has confirmed the availability of an exemption  from
registration under the United States Securities Act of  1933,  as
amended  (the "Securities Act") as to the issuance of the Orbital
Common Shares in exchange for the Exchangeable Shares pursuant to
the  Plan  of  Arrangement, the Exchangeable Share Provisions  or
this  Agreement, in response to the No Action Request (as defined
in  the Combination Agreement) or Orbital has received an opinion
of  counsel  reasonably satisfactory to the Corporation  to  such
effect,  then Orbital shall cause such issuance to be  registered
under the Securities Act, and shall file a registration statement
covering  such  issuance with the SEC and  use  all  commercially
reasonable efforts to cause such registration statement to become
effective  as soon as practicable and remain effective throughout
the  period during which the Exchangeable Shares may be exchanged
in  accordance  with  the Plan of Arrangement,  the  Exchangeable
Share  Provisions or this Agreement.  Orbital agrees to file  any
such  required  registration  statement  as  soon  as  reasonably
practicable.  Orbital shall use all reasonable efforts to  obtain
all  orders  required  from  the applicable  Canadian  securities
authorities  to permit the issuance of the Orbital Common  Shares
upon  any  such  exchange  of  the  Exchangeable  Shares  without
registration or qualification with or approval of or  the  filing
of  any document including any prospectus or similar document  or
the  taking of any proceeding with or the obtaining of any order,
ruling  or  consent from any governmental or regulatory authority
under  any  Canadian federal or provincial law or  regulation  or
pursuant to the rules and regulations of any regulatory authority
or  the  fulfilment  of any other legal requirement  before  such
Orbital  Common  Shares  may  be  issued  and  delivered  by  the
Corporation  or Orbital to the holder thereof or  in  order  that
such Orbital Common Shares may be freely traded thereafter (other
than  any restrictions on transfer by reason of a holder being  a
"control  person" of the Corporation or Orbital for  purposes  of
Canadian  federal or provincial securities law or an  "affiliate"
for purposes of United States Federal or state securities law).

5.11       Reservation of Orbital Common Shares.  Orbital  hereby
represents  and  warrants  that it has irrevocably  reserved  for
issuance  out of its authorized and unissued capital  stock  such
number  of  Orbital Common Shares as is equal to  the  number  of
Exchangeable Shares outstanding at the date hereof and  covenants
that  it  will at all times keep available, free from pre-emptive
and  other  rights,  out of its authorized and  unissued  capital
stock  such number of Orbital Common Shares (or other  shares  or
securities  into which Orbital Common Shares may be  reclassified
or changed) as is necessary to enable Orbital and the Corporation
to   perform  their  respective  obligations  pursuant  to   this
Agreement,  the  Exchangeable Share Provisions  and  the  Support
Agreement.

5.12      Automatic Exchange on Liquidation of Orbital.

           (a)  Orbital shall give the Trustee notice of each  of
the  following  events (a "Liquidation Event") at  the  time  set
forth below:

                                    (i)   in  the  event  of  any
                    determination  by the Board of  Directors  of
                    Orbital  to  institute voluntary liquidation,
                    dissolution  or  winding-up proceedings  with
                    respect  to  Orbital or to effect  any  other
                    distribution of assets of Orbital  among  its
                    stockholders  for the purpose of  winding  up
                    its  affairs, at least 60 days prior  to  the
                    proposed  effective date of such liquidation,
                    dissolution,     winding-up     or      other
                    distribution; and

                                    (ii)  immediately,  upon  the
                    earlier  of (A) receipt by Orbital of  notice
                    of  and (B) Orbital otherwise becoming  aware
                    of  any threatened or instituted claim, suit,
                    petition or other proceedings with respect to
                    the  involuntary liquidation, dissolution  or
                    winding up of Orbital or to effect any  other
                    distribution of assets of Orbital  among  its
                    stockholders  for the purpose of  winding  up
                    its affairs.

           (b)  Immediately following receipt by the Trustee from
Orbital  of  notice of any Liquidation Event, the  Trustee  shall
give notice thereof to the Holders.  Such notice shall include  a
brief  description  of  the  automatic exchange  of  Exchangeable
Shares  for  Orbital  Common Shares provided  for  in  subsection
5.12(c) below.

           (c)   In  order  that  the Holders  will  be  able  to
participate  on  a  pro rata basis with the  holders  of  Orbital
Common  Shares  in  the  distribution of  assets  of  Orbital  in
connection  with a Liquidation Event, on the fifth  Business  Day
prior  to  the  effective  date  of  a  Liquidation  Event   (the
"Liquidation  Event Effective Date") all of the then  outstanding
Exchangeable Shares shall be automatically exchanged for  Orbital
Common Shares.  To effect such automatic exchange, Orbital  shall
purchase  each  Exchangeable  Share  outstanding  on  the   fifth
Business  Day prior to the Liquidation Event Effective  Date  and
held  by  Holders,  and each Holder shall sell  the  Exchangeable
Shares  held by it at such time, for a purchase price  per  share
equal  to (a) the Current Market Price multiplied by the  Current
Orbital Common Share Equivalent on such fifth Business Day  prior
to the Liquidation Event Effective Date, which shall be satisfied
in full in respect of the Exchangeable Shares held by each Holder
by  Orbital  issuing to such Holder such whole number of  Orbital
Common  Shares as is equal to the product obtained by multiplying
the  number  of  such Exchangeable Shares by the Current  Orbital
Common  Share Equivalent (together with an amount in lieu of  any
fractional  Orbital Common Share resulting from such  calculation
payable in accordance with section 9.4 of the Exchangeable  Share
Provisions), plus (b) an additional amount equal to the aggregate
of  all  dividends declared and unpaid on each such  Exchangeable
Share (provided that if the record date for any such declared and
unpaid  dividends occurs on or after the day of closing  of  such
purchase  and  sale, the purchase price shall  not  include  such
additional amount equal to such declared and unpaid dividends).

          (d)  On the fifth Business Day prior to the Liquidation
Event  Effective Date, the closing of the transaction of purchase
and  sale  contemplated by the automatic exchange of Exchangeable
Shares  for  Orbital  Common  Shares  shall  be  deemed  to  have
occurred, and each Holder of Exchangeable Shares shall be  deemed
to  have transferred to Orbital all of the Holder's right,  title
and  interest in and to such Exchangeable Shares and the  related
interest  in the Trust Estate and shall cease to be a  Holder  of
such  Exchangeable Shares and Orbital shall issue to  the  Holder
the Orbital Common Shares issuable upon the automatic exchange of
Exchangeable  Shares for Orbital Common Shares and shall  deliver
to  the  Trustee  for delivery to the Holder  a  cheque  for  the
balance,  if  any,  of the purchase price for  such  Exchangeable
Shares  (or,  if  any  part  of the purchase  price  consists  of
dividends payable in property, such property or property that  is
the  same  as  or  economically  equivalent  to  such  property).
Concurrently  with  such  Holder  ceasing  to  be  a  holder   of
Exchangeable  Shares, the Holder shall be considered  and  deemed
for  all  purposes to be the holder of the Orbital Common  Shares
issued  to  it pursuant to the automatic exchange of Exchangeable
Shares for Orbital Common Shares and the certificates held by the
Holder  previously representing the Exchangeable Shares exchanged
by  the  Holder with Orbital pursuant to such automatic  exchange
shall thereafter be deemed to represent the Orbital Common Shares
issued  to  the  Holder  by Orbital pursuant  to  such  automatic
exchange.  Upon the request of a Holder and the surrender by  the
Holder  of  Exchangeable Share certificates deemed  to  represent
Orbital Common Shares, duly endorsed in blank and accompanied  by
such  instruments of transfer as Orbital may reasonably  require,
Orbital  shall  deliver or cause to be delivered  to  the  Holder
certificates representing the Orbital Common Shares of which  the
Holder is the holder.


                           ARTICLE 6

                     CONCERNING THE TRUSTEE

6.1        Powers and Duties of the Trustee.  The rights,  powers
and  authorities  of  the Trustee under this  Agreement,  in  its
capacity as trustee of the Trust, shall include:

                    (a)  purchasing the Voting Share from Orbital
               as  trustee  for and on behalf of the  Holders  in
               accordance with the provisions of this Agreement;

                      (b)    granting  proxies  and  distributing
               materials   to   Holders  as  provided   in   this
               Agreement;

                     (c)   voting the Holder Votes in  accordance
               with the provisions of this Agreement;

                     (d)   receiving  the grant of  the  Exchange
               Right  and  the  Automatic  Exchange  Rights  from
               Orbital  as  trustee  for and  on  behalf  of  the
               Holders in accordance with the provisions of  this
               Agreement;

                      (e)   exercising  the  Exchange  Right  and
               enforcing  the  benefit of the Automatic  Exchange
               Rights,  in  each  case  in  accordance  with  the
               provisions  of  this Agreement and  in  connection
               therewith   receiving  from  Holders  Exchangeable
               Shares   and   other   requisite   documents   and
               distributing  to such Holders the  Orbital  Common
               Shares  and cheques, if any, to which such Holders
               are  entitled  upon the exercise of  the  Exchange
               Right   or  pursuant  to  the  Automatic  Exchange
               Rights, as the case may be;

                    (f)  holding title to the Trust Estate;

                     (g)  investing any moneys forming, from time
               to time, a part of the Trust Estate as provided in
               this Agreement;

                     (h)  taking action on its own initiative  or
               at the direction of a Holder or Holders to enforce
               the  obligations of Orbital under this  Agreement;
               and

                    (i)  taking such other actions and doing such
               other things as are specifically provided in  this
               Agreement.

           In  the exercise of such rights powers and authorities
the  Trustee  shall  have (and is granted)  such  incidental  and
additional rights, powers and authority not in conflict with  any
of  the  provisions of this Agreement as the Trustee,  acting  in
good faith and in the reasonable exercise of its discretion,  may
deem necessary, appropriate or desirable to effect the purpose of
the Trust.  Any exercise of such discretionary rights, powers and
authorities by the Trustee shall be final, conclusive and binding
upon  all persons.  For greater certainty, the Trustee shall have
only those duties as are set out specifically in this Agreement.

           The  Trustee in exercising its rights, powers,  duties
and  authorities hereunder shall act honestly and in  good  faith
with  a  view  to  the best interests of the  Holders  and  shall
exercise the care, diligence and skill that a reasonably  prudent
trustee would exercise in comparable circumstances.

6.2       No Conflict of Interest.  The Trustee represents to the
Corporation  and  Orbital  that at  the  date  of  execution  and
delivery  of this Agreement there exists no material conflict  of
interest in the role of the Trustee as a fiduciary hereunder  and
the  role  of  the  Trustee in any other capacity.   The  Trustee
shall, within 30 days after it becomes aware that such a material
conflict  of  interest  exists, either  eliminate  such  material
conflict of interest or resign in the manner and with the  effect
specified in Article 9 hereof.  If, notwithstanding the foregoing
provisions  of this section 6.2, the Trustee has such a  material
conflict  of  interest, the validity and enforceability  of  this
Agreement  shall  not  be affected in any  manner  whatsoever  by
reason  only  of  the  existence of  such  material  conflict  of
interest.  If the Trustee contravenes the foregoing provisions of
this  section 6.2, any interested party may apply to the  Supreme
Court of British Columbia (Trial Division) for an order that  the
Trustee be replaced as trustee hereunder.

6.3        Dealings with Transfer Agents, Registrars,  etc.   The
Corporation  and Orbital irrevocably authorize the Trustee,  from
time to time, to:

                     (a)  consult, communicate and otherwise deal
               with   the   respective  registrars  and  transfer
               agents, and with any such subsequent registrar  or
               transfer  agent,  of the Exchangeable  Shares  and
               Orbital Common Shares; and

                    (b)  requisition, from time to time, (i) from
               any   such   registrar  or  transfer   agent   any
               information  readily available  from  the  records
               maintained  by it which the Trustee may reasonably
               require  for  the  discharge  of  its  duties  and
               responsibilities  under this  Agreement  and  (ii)
               from  the transfer agent of Orbital Common Shares,
               and  any subsequent transfer agent of such shares,
               the  share certificates issuable upon the exercise
               from  time  to  time  of the  Exchange  Right  and
               pursuant to the Automatic Exchange Rights  in  the
               manner specified in Article 5 hereof.

The   Corporation   and  Orbital  irrevocably   authorize   their
respective registrars and transfer agents to comply with all such
requests.   Orbital  covenants that it will supply  its  transfer
agent  with  duly executed share certificates for the purpose  of
completing  the exercise from time to time of the Exchange  Right
and  the  Automatic  Exchange Rights, in each  case  pursuant  to
Article 5 hereof.

6.4        Books  and Records.  The Trustee shall keep  available
for  inspection by Orbital and the Corporation, at the  Trustee's
principal  office,  correct and complete  books  and  records  of
account  relating to the Trustee's actions under this  Agreement,
including without limitation all information relating to mailings
and  instructions  to  and  from  Holders  and  all  transactions
pursuant  to  the  Voting  Rights, the  Exchange  Right  and  the
Automatic Exchange Rights for the term of this Agreement.  On  or
before  March 31, 1996, and on or before March 31 in  every  year
thereafter,  so long as the Voting Share is on deposit  with  the
Trustee,   the  Trustee  shall  transmit  to  Orbital   and   the
Corporation  a  brief report, dated as of the preceding  December
31, with respect to:

                     (a)   the property and funds comprising  the
               Trust Estate as of that date;

                     (b)  the number of exercises of the Exchange
               Right,  if  any,  and  the  aggregate  number   of
               Exchangeable  Shares received by  the  Trustee  on
               behalf  of  Holders in consideration of the  issue
               and  delivery by Orbital of Orbital Common  Shares
               in  connection with the Exchange Right, during the
               calendar year ended on such date; and

                     (c)   all other actions taken by the Trustee
               in  the  performance  of  its  duties  under  this
               Agreement that it had not previously reported.

6.5       Income Tax Returns and Reports.  The Trustee shall,  to
the  extent  necessary, prepare and file on behalf of  the  Trust
appropriate United States and Canadian income tax returns and any
other returns or reports as may be required by applicable law  or
pursuant  to the rules and regulations of any securities exchange
or other trading system through which the Exchangeable Shares are
traded  and, in connection therewith, may obtain the  advice  and
assistance of such experts as the Trustee may consider  necessary
or advisable.

6.6        Indemnification Prior to Certain Actions  by  Trustee.
The  Trustee  shall  exercise any or all of the  rights,  duties,
powers  or  authorities  vested in it by this  Agreement  at  the
request,  order  or  direction of any  Holder  upon  such  Holder
furnishing  to  the  Trustee  reasonable  funding,  security  and
indemnity against the costs, expenses and liabilities that may be
incurred  by  the  Trustee therein or thereby, provided  that  no
Holder  shall  be  obligated to furnish to the Trustee  any  such
funding, security or indemnity in connection with the exercise by
the  Trustee of any of its rights, duties, powers and authorities
with  respect  to  (i)  the Voting Share pursuant  to  Article  4
hereof,  subject to section 6.15 hereof, (ii) the Exchange  Right
pursuant to Article 5 hereof, subject to section 6.15 hereof, and
(iii) the Automatic Exchange Rights pursuant to Article 5 hereof.

           None  of  the  provisions contained in this  Agreement
shall  require  the Trustee to expend or risk its  own  funds  or
otherwise incur financial liability in the exercise of any of its
rights,  powers,  duties or authorities unless funded  and  given
security and indemnity as aforesaid.

6.7       Actions by Holders.  No Holder shall have the right  to
institute any action, suit or proceeding or to exercise any other
remedy  authorized by this Agreement for the purpose of enforcing
any  of  its  rights or for the execution of any trust  or  power
hereunder unless the Holder has requested the Trustee to take  or
institute  such  action,  suit or proceeding  and  furnished  the
Trustee with the funding, security and indemnity referred  to  in
section  6.6  hereof  and the Trustee shall have  failed  to  act
within  a  reasonable time thereafter.  In  such  case,  but  not
otherwise,  the  Holder shall be entitled to take proceedings  in
any  court  of  competent jurisdiction such as the Trustee  might
have  taken, it being understood and intended that no one or more
Holders  shall have any right in any manner whatsoever to affect,
disturb  or  prejudice  the rights hereby  created  by  any  such
action,  or  to enforce any right hereunder or under  the  Voting
Rights,  the  Exchange  Right or the  Automatic  Exchange  Rights
except  subject  to  the  conditions and  in  the  manner  herein
provided,  and  that  all powers and trusts  hereunder  shall  be
exercised and all proceedings at law shall be instituted, had and
maintained by the Trustee, except only as herein provided, and in
any event for the equal benefit of all Holders.

6.8        Reliance upon Declarations.  The Trustee shall not  be
considered  to be in contravention of any of its rights,  powers,
duties  and authorities hereunder if, when required, it acts  and
relies  in  good  faith  upon  lists,  mailing  labels,  notices,
statutory declarations, certificates, opinions, reports or  other
papers  or documents furnished pursuant to the provisions  hereof
or  required by the Trustee to be furnished to it in the exercise
of  its rights, powers, duties and authorities hereunder and such
lists,   mailing   labels,   notices,   statutory   declarations,
certificates,  opinions,  reports or other  papers  or  documents
comply  with the provisions of section 6.9 hereof, if applicable,
and with any other applicable provisions of this Agreement.

6.9        Evidence  and Authority to Trustee.   The  Corporation
and/or   Orbital  shall  furnish  to  the  Trustee  evidence   of
compliance  with  the conditions provided for in  this  Agreement
relating to any action or step required or permitted to be  taken
by  the  Corporation  and/or Orbital or the  Trustee  under  this
Agreement  or  as a result of any obligation imposed  under  this
Agreement,  including,  without limitation,  in  respect  of  the
Voting  Rights,  the  Exchange Right or  the  Automatic  Exchange
Rights  and  the taking of any other action to be  taken  by  the
Trustee  at  the  request  of  or  on  the  application  of   the
Corporation and/or Orbital forthwith if and when:

                     (a)   such evidence is required by any other
               section of this Agreement to be furnished  to  the
               Trustee  in  accordance with  the  terms  of  this
               section 6.9; or

                     (b)   the  Trustee, in the exercise  of  its
               rights, powers, duties and authorities under  this
               Agreement,  gives the Corporation  and/or  Orbital
               written  notice  requiring  it  to  furnish   such
               evidence  in relation to any particular action  or
               obligation specified in such notice.

          Such evidence shall consist of an Officer's Certificate
of the Corporation and/or Orbital or a statutory declaration or a
certificate  made  by  persons  entitled  to  sign  an  Officer's
Certificate  stating that any such condition  has  been  complied
with in accordance with the terms of this Agreement.

           Whenever such evidence relates to a matter other  than
the  Voting Rights, the Exchange Right or the Automatic  Exchange
Rights,  and  except as otherwise specifically  provided  herein,
such  evidence  may  consist  of  a  report  or  opinion  of  any
solicitor,  auditor, accountant, appraiser, valuer,  engineer  or
other  expert  or  any  other  person whose  qualifications  give
authority  to  a  statement made by him, provided  that  if  such
report or opinion is furnished by a director, officer or employee
of  the Corporation and/or Orbital it shall be in the form of  an
Officer's Certificate or a statutory declaration.

           Each  statutory declaration, certificate,  opinion  or
report furnished to the Trustee as evidence of compliance with  a
condition  provided  for  in  this  Agreement  shall  include   a
statement by the person giving the evidence:

                      (a)    declaring  that  he  has  read   and
               understands  the  provisions  of  this   Agreement
               relating to the condition in question;

                     (b)  describing the nature and scope of  the
               examination or investigation upon which  he  based
               the  statutory declaration, certificate, statement
               or opinion; and

                      (c)    declaring  that  he  has  made  such
               examination  or  investigation as he  believes  is
               necessary to enable him to make the statements  or
               give the opinions contained or expressed therein.

6.10      Experts, Advisers and Agents.

          The Trustee may:

                     (a)   in relation to this Agreement act  and
               rely  on  the  opinion or advice of or information
               obtained  from any solicitor, auditor, accountant,
               appraiser,  valuer,  engineer  or  other   expert,
               whether  retained  by  the  Trustee  or   by   the
               Corporation and/or Orbital or otherwise,  and  may
               employ such assistants as may be necessary to  the
               proper  discharge  of its powers  and  duties  and
               determination of its rights hereunder and may  pay
               proper  and reasonable compensation for  all  such
               legal and other advice or assistance as aforesaid;
               and

                     (b)  employ such agents and other assistants
               as  it  may  reasonably  require  for  the  proper
               discharge of its powers and duties hereunder,  and
               may  pay  reasonable remuneration for all services
               performed  for it in the discharge of  the  trusts
               hereof  and  compensation for  all  disbursements,
               costs  and expenses made or incurred by it in  the
               discharge  of  its  duties hereunder  and  in  the
               management of the Trust.

6.11      Investment of Moneys Held By Trustee.  Unless otherwise
provided  in this Agreement, any moneys held by or on  behalf  of
the  Trustee that under the terms of this Agreement may or  ought
to  be  invested or which may be on deposit with the  Trustee  or
that  may  be  in  the hands of the Trustee may be  invested  and
reinvested  in  the name or under the control of the  Trustee  in
securities  in  which,  under the laws  of  the  Commonwealth  of
Massachusetts,  trustees are authorized to invest  trust  moneys,
provided  that  such securities are stated to mature  within  two
years  after their purchase by the Trustee, and the Trustee shall
so   invest  such  moneys  on  the  written  direction   of   the
Corporation.    Pending  the  investment   of   any   moneys   as
hereinbefore provided, such moneys may be deposited in  the  name
of  the Trustee in any bank in the United States approved by  the
Corporation  or,  with  the consent of the  Corporation,  in  the
deposit  department of the Trustee at the rate of  interest  then
current on similar deposits.

6.12       Trustee  Not Required to Give Security.   The  Trustee
shall not be required to give any bond or security in respect  of
the   execution  of  the  trusts,  rights,  duties,  powers   and
authorities of this Agreement.

6.13       Trustee  Not  Bound  to Act on Corporation's  Request.
Except as in this Agreement otherwise specifically provided,  the
Trustee  shall  not  be  bound  to act  in  accordance  with  any
direction or request of the Corporation and/or Orbital or of  the
directors  thereof  until  a  duly  authenticated  copy  of   the
instrument  or  resolution containing such direction  or  request
shall  have been delivered to the Trustee, and the Trustee  shall
be  empowered to act and rely upon any such copy purporting to be
authenticated and believed by the Trustee to be genuine.

6.14      Authority to Carry on Business.  The Trustee represents
to  the Corporation and Orbital that at the date of execution and
delivery by it of this Agreement it is authorized to perform  its
obligations pursuant to this Agreement under all applicable  laws
but  if, notwithstanding the provisions of this section 6.14,  it
ceases  to  be so authorized, the validity and enforceability  of
this Agreement and the Voting Rights, the Exchange Right and  the
Automatic  Exchange Rights shall not be affected  in  any  manner
whatsoever  by  reason only of such event but the Trustee  shall,
within  30 days after ceasing to be so authorized, either  become
so  authorized  or  resign  in the manner  and  with  the  effect
specified in Article 9 hereof.

6.15       Conflicting Claims.  If conflicting claims or  demands
are  made or asserted with respect to any interest of any  Holder
in  any  Exchangeable Shares, including any disagreement  between
the  heirs, representatives, successors or assigns succeeding  to
all or any part of the interest of any Holder in any Exchangeable
Shares  resulting in conflicting claims or demands being made  in
connection  with  such  interest,  then  the  Trustee  shall   be
entitled,  at its sole discretion, to refuse to recognize  or  to
comply  with  any  such claim or demand.   In  so  refusing,  the
Trustee  may  elect not to exercise any Voting  Rights,  Exchange
Right  or  Automatic Exchange Rights subject to such  conflicting
claims or demands and, in so doing, the Trustee shall not  be  or
become  liable to any person on account of such election  or  its
failure or refusal to comply with any such conflicting claims  or
demands.   The Trustee shall be entitled to continue  to  refrain
from acting and to refuse to act until:

                    (a)  the rights of all adverse claimants with
               respect  to the Voting Rights, Exchange  Right  or
               Automatic   Exchange  Rights   subject   to   such
               conflicting   claims   or   demands   have    been
               adjudicated  by a final judgment  of  a  court  of
               competent jurisdiction; or

                     (b)   all  differences with respect  to  the
               Voting   Rights,  Exchange  Right   or   Automatic
               Exchange Rights subject to such conflicting claims
               or  demands  have been conclusively settled  by  a
               valid  written  agreement  binding  on  all   such
               adverse claimants, and the Trustee shall have been
               furnished with an executed copy of such agreement.

If  the Trustee elects to recognize any claim or comply with  any
demand  made  by  any  such  adverse  claimant,  it  may  in  its
discretion require such claimant to furnish such surety  bond  or
other  security  satisfactory to the Trustee  as  it  shall  deem
appropriate  fully  to  indemnify it as between  all  conflicting
claims or demands.

6.16       Acceptance of Trust.  The Trustee hereby  accepts  the
Trust  created  and  provided for by and in  this  Agreement  and
agrees  to perform the same upon the terms and conditions  herein
set  forth  and  to  hold  all rights,  privileges  and  benefits
conferred hereby and by law in trust for the various persons  who
shall from time to time be Holders, subject to all the terms  and
conditions herein set forth.


                           ARTICLE 7

                          COMPENSATION

7.1        Fees  and  Expenses of the Trustee.  Orbital  and  the
Corporation  jointly and severally agree to pay  to  the  Trustee
reasonable  compensation for all of the services rendered  by  it
under  this  Agreement and will reimburse  the  Trustee  for  all
reasonable  expenses and disbursements, including  the  cost  and
expense  of  any  suit  or litigation of any  character  and  any
proceedings before any governmental agency reasonably incurred by
the  Trustee in connection with its rights and duties under  this
Agreement;  provided that Orbital and the Corporation shall  have
no  obligation  to  reimburse the Trustee  for  any  expenses  or
disbursements  paid, incurred or suffered by the Trustee  in  any
suit  or  litigation in which the Trustee is determined  to  have
acted  fraudulently,  in bad faith or with negligence  or  wilful
misconduct.


                           ARTICLE 8

          INDEMNIFICATION AND LIMITATION OF LIABILITY

8.1        Indemnification  of  the  Trustee.   Orbital  and  the
Corporation  jointly and severally agree to  indemnify  and  hold
harmless  the  Trustee  and  each  of  its  directors,  officers,
employees and agents appointed and acting in accordance with this
Agreement  (collectively the "Indemnified Parties")  against  all
claims,  losses, damages, costs, penalties, fines and  reasonable
expenses  (including reasonable expenses of the  Trustee's  legal
counsel)  which, without fraud, negligence, wilful misconduct  or
bad  faith  on the part of such Indemnified Party, may  be  paid,
incurred or suffered by the Indemnified Party by reason of or  as
a  result  of the Trustee's acceptance or administration  of  the
Trust,  its  compliance  with  its  duties  set  forth  in   this
Agreement, or any written or oral instructions delivered  to  the
Trustee  by  Orbital or the Corporation pursuant hereto.   In  no
case  shall  Orbital  or the Corporation  be  liable  under  this
indemnity  for  any claim against any of the Indemnified  Parties
unless  Orbital  and  the Corporation shall be  notified  by  the
Trustee  of  the written assertion of a claim or  of  any  action
commenced against the Indemnified Parties, promptly after any  of
the  Indemnified  Parties shall have received  any  such  written
assertion of a claim or shall have been served with a summons  or
other first legal process giving information as to the nature and
basis  of  the  claim.  Subject to (ii), below, Orbital  and  the
Corporation shall be entitled to participate at their own expense
in the defense and, if Orbital or the Corporation so elect at any
time after receipt of such notice, either of them may assume  the
defence  of  any  suit brought to enforce any  such  claim.   The
Trustee  shall have the right to employ separate counsel  in  any
such suit and participate in the defence thereof but the fees and
expenses  of such counsel shall be at the expense of the  Trustee
unless: (i) the employment of such counsel has been authorized by
Orbital or the Corporation; or (ii) the named parties to any such
suit include both the Trustee and Orbital or the Corporation  and
the  Trustee  shall  have been advised by counsel  acceptable  to
Orbital  or  the Corporation that there may be one or more  legal
defences available to the Trustee that are different from  or  in
addition  to  those available to Orbital or the  Corporation  and
that an actual or potential conflict of interest exists (in which
case  Orbital  and the Corporation shall not have  the  right  to
assume  the  defence of such suit on behalf of  the  Trustee  but
shall  be  liable  to  pay the reasonable fees  and  expenses  of
counsel for the Trustee).

8.2       Limitation of Liability.  The Trustee shall not be held
liable  for any loss that may occur by reason of depreciation  of
the value of any part of the Trust Estate or any loss incurred on
any investment of funds pursuant to this Agreement, except to the
extent  that  such loss is attributable to the fraud, negligence,
wilful misconduct or bad faith on the part of the Trustee.


                           ARTICLE 9

                       CHANGE OF TRUSTEE

9.1        Resignation.   The Trustee, or any  trustee  hereafter
appointed,  may  at any time resign by giving written  notice  of
such  resignation to Orbital and the Corporation  specifying  the
date  on  which it desires to resign, provided that  such  notice
shall  never  be  given  less than 60 days  before  such  desired
resignation  date  unless Orbital and the  Corporation  otherwise
agree  and provided further that such resignation shall not  take
effect  until the date of the appointment of a successor  trustee
and  the acceptance of such appointment by the successor trustee.
Upon  receiving  such  notice  of resignation,  Orbital  and  the
Corporation shall promptly appoint a successor trustee by written
instrument in duplicate, one copy of which shall be delivered  to
the  resigning  trustee  and one copy to the  successor  trustee.
Failing  acceptance by a successor trustee, a  successor  trustee
may  be  appointed  by an order of the Supreme Court  of  British
Columbia upon application of one or more of the parties hereto.

9.2         Removal.   The  Trustee,  or  any  trustee  hereafter
appointed, may be removed with or without cause, at any  time  on
60  days' prior notice by written instrument executed by  Orbital
and  the  Corporation, in duplicate, one copy of which  shall  be
delivered to the trustee so removed and one copy to the successor
trustee.

9.3       Successor Trustee.  Any successor trustee appointed  as
provided  under  this  Agreement shall execute,  acknowledge  and
deliver  to  Orbital and the Corporation and to  its  predecessor
trustee an instrument accepting such appointment.  Thereupon  the
resignation  or removal of the predecessor trustee  shall  become
effective  and such successor trustee, without any  further  act,
deed  or  conveyance, shall become vested with  all  the  rights,
powers,  duties  and  obligations of its predecessor  under  this
Agreement, with like effect as if originally named as trustee  in
this  Agreement.  However, on the written request of Orbital  and
the  Corporation or of the successor trustee, the trustee ceasing
to act shall, upon payment of any amounts then due it pursuant to
the  provisions  of  this  Agreement,  execute  and  deliver   an
instrument transferring to such successor trustee all the  rights
and powers of the trustee so ceasing to act.  Upon the request of
any  such  successor trustee, Orbital, the Corporation  and  such
predecessor  trustee  shall execute any and  all  instruments  in
writing for more fully and certainly vesting in and confirming to
such successor trustee all such rights and powers.

9.4        Notice  of  Successor  Trustee.   Upon  acceptance  of
appointment  by  a successor trustee as provided herein,  Orbital
and  the  Corporation  shall cause to be  mailed  notice  of  the
succession of such trustee hereunder to each Holder specified  in
a  List.  If Orbital or the Corporation shall fail to cause  such
notice   to  be  mailed  within  10  days  after  acceptance   of
appointment by the successor trustee, the successor trustee shall
cause such notice to be mailed at the expense of Orbital and  the
Corporation.


                           ARTICLE 10

                       ORBITAL SUCCESSORS

10.1       Certain  Requirements in Respect of Combination,  etc.
Orbital shall not enter into any transaction (whether by  way  of
reconstruction, reorganization, consolidation, merger,  transfer,
sale, lease or otherwise) whereby all or substantially all of its
undertaking, property and assets would become the property of any
other  person  or,  in the case of a merger,  of  the  continuing
corporation resulting therefrom, unless:

                      (a)    such   other  person  or  continuing
               corporation  is a corporation (herein  called  the
               "Orbital  Successor") incorporated under the  laws
               of  any state of the United States or the laws  of
               Canada or any province thereof; and

                     (b)  Orbital Successor, by operation of law,
               becomes,  without  more, bound by  the  terms  and
               provisions of this Agreement or, if not so  bound,
               executes, prior to or contemporaneously  with  the
               consummation  of  such  transaction  an  agreement
               supplemental hereto and such other instruments (if
               any)  as  are  satisfactory to the Trustee  acting
               reasonably  to evidence the assumption by  Orbital
               Successor of liability for all moneys payable  and
               property deliverable hereunder and the covenant of
               such Orbital Successor to pay and deliver or cause
               to  be  delivered  the same and its  agreement  to
               observe   and   perform  all  the  covenants   and
               obligations of Orbital under this Agreement.

10.2        Vesting   of  Powers  in  Successor.   Whenever   the
conditions  of  section 10.1 hereof have been duly  observed  and
performed,  the  Trustee, if required, by  section  10.1  hereof,
Orbital  Successor and the Corporation shall execute and  deliver
the  supplemental agreement provided for in Article 11 hereof and
thereupon Orbital Successor shall possess and from time  to  time
may exercise each and every right and power of Orbital under this
Agreement  in  the name of Orbital or otherwise and  any  act  or
proceeding by any provision of this Agreement required to be done
or performed by the board of directors of Orbital or any officers
of  Orbital may be done and performed with like force and  effect
by the directors or officers of such Orbital Successor.

10.3       Wholly-Owned Subsidiaries.  Nothing  herein  shall  be
construed  as  preventing  the  amalgamation  or  merger  of  any
wholly-owned subsidiary of Orbital with or into Orbital.


                           ARTICLE 11

          AMENDMENTS AND SUPPLEMENTAL TRUST AGREEMENTS

11.1      Amendments, Modifications, etc.  This Agreement may not
be amended or modified except by an agreement in writing executed
by  the Corporation, Orbital and the Trustee and approved by  the
Holders in accordance with section 8.2 of the Exchangeable  Share
Provisions.

11.2      Ministerial Amendments.  Notwithstanding the provisions
of  section  11.1  hereof, the parties to this Agreement  may  in
writing,  at any time and from time to time, without the approval
of  the  Holders, amend or modify this Agreement for the purposes
of:

                    (a)  adding to the covenants of any or all of
               the  parties  hereto  for the  protection  of  the
               Holders hereunder;

                     (b)  making such amendments or modifications
               not  inconsistent with this Agreement  as  may  be
               necessary or desirable with respect to matters  or
               questions  that, in the opinion of  the  Board  of
               Directors  of each of Orbital and Corporation  and
               in  the opinion of the Trustee, having in mind the
               best  interests of the Holders as a whole, it  may
               be expedient to make, provided that such boards of
               directors and the Trustee shall be of the  opinion
               that such amendments and modifications will not be
               prejudicial to the interests of the Holders  as  a
               whole; or

                     (c)   making  such  changes  or  corrections
               required  for the purpose of curing or  correcting
               any  ambiguity or defect or inconsistent provision
               or clerical omission or mistake or manifest error,
               provided  that  the  Trustee  and  the  Board   of
               Directors  of each of the Corporation and  Orbital
               shall  be  of  the  opinion that such  changes  or
               corrections  will  not  be  prejudicial   to   the
               interests of the Holders as a whole.

11.3       Meeting  to Consider Amendments.  The Corporation,  at
the  request of Orbital, shall call a meeting or meetings of  the
Holders for the purpose of considering any proposed amendment  or
modification  requiring  approval  pursuant  hereto.   Any   such
meeting  or meetings shall be called and held in accordance  with
the by-laws of the Corporation, the Exchangeable Share Provisions
and all applicable laws.

11.4       Changes  in  Capital of Orbital and  the  Corporation.
Notwithstanding section 11.1, at all times after  the  occurrence
of   any   Orbital   Common  Share  Reorganization   or   Capital
Reorganization  (as such terms are respectively  defined  in  the
Exchangeable  Share  Provisions) or other change  in  either  the
Orbital  Common Shares or the Exchangeable Shares or  both,  this
Agreement shall forthwith be amended and modified as necessary in
order  that  it  shall apply with full force and effect,  mutatis
mutandis, to all new securities into which Orbital Common  Shares
or the Exchangeable Shares or both are so changed and the parties
hereto  shall execute and deliver a supplemental agreement giving
effect   to   and   evidencing  such  necessary  amendments   and
modifications.

11.5         Execution   of   Supplemental   Trust    Agreements.
Notwithstanding  section 11.1, from time to time the  Corporation
(when  authorized  by  a resolution of the Board  of  Directors),
Orbital  (when  authorized  by  a  resolution  of  its  board  of
directors) and the Trustee may, subject to the provisions hereof,
and  they shall, when so directed by these presents, execute  and
deliver by their proper officers, Agreements or other instruments
supplemental hereto, which thereafter shall form part hereof, for
any one or more of the following purposes:

                     (a)   evidencing the succession  of  Orbital
               Successors  to  Orbital and the covenants  of  and
               obligations assumed by each such Orbital Successor
               in  accordance with the provisions of  Article  10
               and  the  succession of any successor  trustee  in
               accordance with the provisions of Article 9;

                     (b)  making any additions to, deletions from
               or alterations of the provisions of this Agreement
               or  the  Voting Rights, the Exchange Right or  the
               Automatic Exchange Rights that, in the opinion  of
               the   Trustee  acting  reasonably  will   not   be
               prejudicial to the interests of the Holders  as  a
               whole  or  are  in the opinion of counsel  to  the
               Trustee   necessary  or  advisable  in  order   to
               incorporate,   reflect   or   comply   with    any
               legislation  the  provisions  of  which  apply  to
               Orbital,  the  Corporation, the  Trustee  or  this
               Agreement; and

                     (c)  for any other purposes not inconsistent
               with  the  provisions of this Agreement including,
               without  limitation,  to  make  or  evidence   any
               amendment  or  modification to this  Agreement  as
               contemplated hereby, provided that, in the opinion
               of  the  Trustee acting reasonably, the rights  of
               the Trustee and the Holders as a whole will not be
               prejudiced thereby.


                           ARTICLE 12

                          TERMINATION

12.1       Term.    The  Trust  created by this  Agreement  shall
continue until the earliest to occur of the following events:

                     (a)  no outstanding Exchangeable Shares  are
               held by any Holder;

                     (b)   each  of the Corporation  and  Orbital
               elects in writing to terminate the Trust and  such
               termination  is  approved by the  Holders  of  the
               Exchangeable Shares in accordance with Section 8.2
               of the Exchangeable Share Provisions; and

                     (c)   21  years after the death of the  last
               survivor  of  the descendants of His Majesty  King
               George  VI of the United Kingdom of Great  Britain
               and  Northern Ireland living on the  date  of  the
               creation of the Trust.

12.2       Survival.  The provisions of Articles 7 and  8  hereof
shall  survive any termination of the Trust pursuant  to  section
12.1.


                           ARTICLE 13

                            GENERAL

13.1       Severability.  If any provision of this  Agreement  is
held  to  be  invalid,  illegal or unenforceable,  the  validity,
legality  or  enforceability of the remainder of  this  Agreement
shall  not  in any way be affected or impaired thereby  and  this
Agreement  shall  be  carried  out  as  nearly  as  possible   in
accordance  with  its  original terms and  conditions;  provided,
however,  that  if  the provision or provisions  so  held  to  be
invalid, in the reasonable judgment of the parties, is or are  so
fundamental  to  the intent of the parties and the  operation  of
this  Agreement  that  the enforcement of  the  other  provisions
hereof,  in  the absence of such invalid provision or provisions,
would  damage irreparably the intent of the parties  in  entering
into  this  Agreement, the parties shall agree (i)  to  terminate
this  Agreement,  or  (ii)  to amend  or  otherwise  modify  this
Agreement  so as to carry out the intent and purposes hereof  and
the transactions contemplated hereby.

13.2       Inurement.  This Agreement shall be binding  upon  and
inure  to  the benefit of the parties hereto and their respective
successors  and  permitted assigns and  to  the  benefit  of  the
Holders.

13.3        Notices   to   Parties.   All   notices   and   other
communications between the parties hereunder shall be in  writing
and shall be deemed to have been given if delivered personally or
by  confirmed telecopy to the parties at the following  addresses
(or at such other address for such party as shall be specified in
like notice):

                    (a)  if to Orbital at:

               Orbital Sciences Corporation
               21700 Atlantic Boulevard
               Dulles, Virginia 20166
               U.S.A.

               Attention:     General Counsel

               Telecopy: (703) 406-5572

          (b)  if to the Corporation at:

               MacDonald Dettwiler Holdings Inc.
               13800 Commerce Parkway
               Vancouver, British Columbia
               V6V 2J3

               Attention:     #

               Telecopy: (604) #

                (with a copy to Orbital at the address set out in
(a))

                    (c)  if to the Trustee at:

               #

                         Attention:     #

                         Telecopy: (#) #

Any  notice  or  other  communication given personally  shall  be
deemed to have been given and received upon delivery thereof  and
if  given  by  telecopy shall be deemed to have  been  given  and
received on the date of receipt thereof unless such day is not  a
Business Day in which case it shall be deemed to have been  given
and received upon the immediately following Business Day.

13.4      Notice to Holders.  Any and all notices to be given and
any  documents to be sent to any Holders may be given or sent  to
the  address of such Holder shown on the register of  Holders  in
any  manner permitted by the by-laws of the Corporation from time
to  time in force in respect of notices to shareholders and shall
be deemed to be received (if given or sent in such manner) at the
time  specified in such by-laws, the provisions of  which  bylaws
shall apply mutatis mutandis to notices or documents as aforesaid
sent to such Holders.

13.5      Risk of Payments by Post.  Whenever payments are to  be
made or documents are to be sent to any Holder by the Trustee  or
by  the  Corporation,  or by such Holder to  the  Trustee  or  to
Orbital or the Corporation, the making of such payment or sending
of  such  document sent through the post shall be at the risk  of
the  Corporation, in the case of payments made or documents  sent
by the Trustee or the Corporation, and the Holder, in the case of
payments made or documents sent by the Holder.

13.6       Counterparts.   This  Agreement  may  be  executed  in
counterparts, each of which shall be deemed an original, but  all
of  which  taken  together  shall constitute  one  and  the  same
instrument.

13.7       Jurisdiction.  This Agreement shall be  construed  and
enforced  in accordance with the laws of the Province of  British
Columbia and the laws of Canada applicable therein.

13.8        Attornment.   Orbital  agrees  that  any  action   or
proceeding  arising out of or relating to this Agreement  may  be
instituted  in  the  courts of the Province of British  Columbia,
waives  any  objection that it may have now or hereafter  to  the
venue  of  any such action or proceeding, irrevocably submits  to
the  jurisdiction  of  the said courts  in  any  such  action  or
proceeding, agrees to be bound by any judgment of the said courts
and  agrees  not to seek, and hereby waives, any  review  of  the
merits  of  any  such  judgment  by  the  courts  of  any   other
jurisdiction   and  hereby  appoints  the  Corporation   at   its
registered office as Orbital's attorney for service of process.

          IN WITNESS WHEREOF, the parties hereto have caused this
Agreement to be duly executed as of the date first above written.


                                   ORBITAL SCIENCES CORPORATION

                                   by ___________________________


                                      ___________________________

                                   MACDONALD DETTWILER HOLDINGS
                                   INC.

                                   by ___________________________


                                      ___________________________

                                   STATE  STREET BANK  AND  TRUST
                                   COMPANY


                                   by ___________________________


                                      ___________________________



                          EXHIBIT 2.3


                       SUPPORT AGREEMENT


           MEMORANDUM  OF AGREEMENT made as  of  the      day  of
1995.


B E T W E E N:


                  ORBITAL SCIENCES CORPORATION,
                  a  corporation existing under
                  the  laws  of  the  State  of
                  Delaware,

                  (hereinafter referred to as "Orbital"),

                            - and -

                  MACDONALD DETTWILER HOLDINGS INC.
                  (formerly known as 3173623 Canada Inc.),
                  a  corporation existing under
                  the laws of Canada.

                  (hereinafter referred to as "Corporation").



          WHEREAS pursuant to a combination agreement dated as of
August  31,  1995 (the "Combination Agreement")  by  and  between
Orbital,  the Corporation and MacDonald, Dettwiler and Associates
Ltd.  ("MDA") the parties agreed that on the Effective  Date  (as
defined   in   the  Combination  Agreement),  Orbital   and   the
Corporation  would  execute  and  deliver  a  Support   Agreement
containing the terms and conditions set forth in Exhibit  2.3  to
the  Combination  Agreement together with such  other  terms  and
conditions  as may be agreed to by the parties to the Combination
Agreement acting reasonably;

            AND   WHEREAS   pursuant  to  an   arrangement   (the
"Arrangement") effected by articles of arrangement filed pursuant
to  the  Canada Business Corporations Act on #, 1995, each issued
and  outstanding common share of MDA (an "MDA Common Share")  was
exchanged  directly  or indirectly with the Corporation  for  0.#
issued  and  outstanding Exchangeable Shares of  the  Corporation
(the "Exchangeable Shares");

           AND WHEREAS the aforesaid articles of arrangement  set
forth   the   rights,  privileges,  restrictions  and  conditions
(collectively the "Exchangeable Share Provisions")  attaching  to
the Exchangeable Shares;

            AND   WHEREAS  the  parties  hereto  desire  to  make
appropriate  provision  and  to  establish  a  procedure  whereby
Orbital  will take certain actions and make certain payments  and
deliveries necessary to ensure that the Corporation will be  able
to  make certain payments and to deliver or cause to be delivered
shares   of  Orbital  Common  Shares  in  satisfaction   of   the
obligations  of  the  Corporation under  the  Exchangeable  Share
Provisions  with  respect  to  the payment  and  satisfaction  of
dividends,  Liquidation Amounts, Retraction Prices and Redemption
Prices all in accordance with the Exchangeable Share Provisions;

           NOW  THEREFORE  in  consideration  of  the  respective
covenants  in  this  agreement and for other  good  and  valuable
consideration  (the receipt and sufficiency of which  are  hereby
acknowledged), the parties agree as follows:

                           ARTICLE 1

                 DEFINITIONS AND INTERPRETATION

1.1        Defined  Terms.  Each term denoted herein  by  initial
capital  letters and not otherwise defined herein shall have  the
meaning  ascribed  thereto in the Exchangeable Share  Provisions,
unless the context requires otherwise.

1.2        Interpretation  not Affected by  Headings,  etc.   The
division of this agreement into articles, sections and paragraphs
and  the  insertion of headings are for convenience of  reference
only  and shall not affect the construction or interpretation  of
this agreement.

1.3        Number,  Gender,  etc.  Words importing  the  singular
number  only  shall  include the plural and  vice  versa.   Words
importing the use of any gender shall include all genders.

1.4        Date for any Action.  If any date on which any  action
is  required to be taken under this agreement is not  a  Business
Day,  such  action  shall be required to be  taken  on  the  next
succeeding Business Day.


                           ARTICLE 2

            COVENANTS OF ORBITAL AND THE Corporation

2.1       Covenants of Orbital Regarding Exchangeable Shares.  So
long as any Exchangeable Shares are outstanding, Orbital will:

                     (a)   not  declare or pay  any  dividend  on
               Orbital  Common Shares unless (i) the  Corporation
               shall  have  sufficient assets,  funds  and  other
               property  (including,  where  applicable,  Orbital
               Common  Shares  or  other securities  of  Orbital)
               available  to enable the due declaration  and  the
               due   and  punctual  payment  in  accordance  with
               applicable law, of an equivalent dividend  on  the
               Exchangeable   Shares  in  accordance   with   the
               Exchangeable   Share  Provisions  and   (ii)   the
               Corporation shall simultaneously declare  or  pay,
               as  the case may be, an equivalent dividend on the
               Exchangeable   Shares  in  accordance   with   the
               Exchangeable Share Provisions;

                      (b)    cause  the  Corporation  to  declare
               simultaneously   with  the  declaration   of   any
               dividend  on  Orbital Common Shares an  equivalent
               dividend on the Exchangeable Shares and, when such
               dividend  is paid on Orbital Common Shares,  cause
               the  Corporation  to pay simultaneously  therewith
               such   equivalent  dividend  on  the  Exchangeable
               Shares,  in  each  case  in  accordance  with  the
               Exchangeable Share Provisions;

                     (c)  advise the Corporation sufficiently  in
               advance  of  the  declaration by  Orbital  of  any
               dividend  on  Orbital Common Shares and  take  all
               such   other   actions  as   are   necessary,   in
               cooperation  with the Corporation, to ensure  that
               the declaration date, record date and payment date
               for  any dividend on the Exchangeable Shares shall
               be  the same as the record date, declaration  date
               and payment date for the corresponding dividend on
               Orbital Common Shares and such dates in respect of
               dividends on the Exchangeable Shares shall  be  in
               accordance   with   any   requirement    of    the
               Exchangeable  Share  Provisions  and   the   stock
               exchange  on  which  the Exchangeable  Shares  are
               listed;

                     (d)   ensure  that the record date  for  any
               dividend   declared  on  Orbital  Common   Shares,
               Orbital   Common   Share  Reorganization,   Rights
               Offering,   Special   Distribution   or    Capital
               Reorganization is not less than 10  Business  Days
               after  the  declaration date  for  such  dividend,
               Orbital   Common   Share  Reorganization,   Rights
               Offering,   Special   Distribution   or    Capital
               Reorganization;

                     (e)   take all such actions and do all  such
               things as are necessary or desirable to enable and
               permit   the   Corporation,  in  accordance   with
               applicable  law, to pay and otherwise perform  its
               obligations  with respect to the  satisfaction  of
               the  Liquidation Amount in respect of each  issued
               and   outstanding  Exchangeable  Share  upon   the
               liquidation,  dissolution  or  winding-up  of  the
               Corporation, including without limitation all such
               actions  and  all such things as are necessary  or
               desirable to enable and permit the Corporation  to
               cause  to  be  delivered shares of Orbital  Common
               Shares  to  the holders of Exchangeable Shares  in
               satisfaction  of the Liquidation Amount  for  each
               such  Exchangeable Share, in accordance  with  the
               provisions of Article 4 of the Exchangeable  Share
               Provisions;

                     (f)   take all such actions and do all  such
               things as are necessary or desirable to enable and
               permit   the   Corporation,  in  accordance   with
               applicable  law, to pay and otherwise perform  its
               obligations  with respect to the  satisfaction  of
               the  Retraction  Price and the  Redemption  Price,
               including without limitation all such actions  and
               all  such things as are necessary or desirable  to
               enable and permit the Corporation to cause  to  be
               delivered shares of Orbital Common Shares  to  the
               holders   of   Exchangeable   Shares,   upon   the
               retraction   or  redemption  of  the  Exchangeable
               Shares  in  accordance  with  the  provisions   of
               Article  5 or Article 6 of the Exchangeable  Share
               Provisions, as the case may be;

                     (g)   not exercise its vote as a shareholder
               of  the  Corporation to initiate,  consent  to  or
               approve the voluntary liquidation, dissolution  or
               winding-up of the Corporation nor take any  action
               or  omit  to  take any action that is designed  to
               result   in   the   liquidation,  dissolution   or
               winding-up of the Corporation; and

                     (h)   not exercise its vote as a shareholder
               of the Corporation to authorize the continuance or
               other  transfer of the corporate existence of  the
               Corporation to any jurisdiction outside Canada.

2.2         Segregation  of  Funds.   Orbital  will   cause   the
Corporation to deposit a sufficient amount of funds in a separate
account  and  segregate a sufficient amount of  such  assets  and
other  property as is necessary to enable the Corporation to  pay
or   otherwise  satisfy  the  applicable  dividends,  Liquidation
Amount,  Retraction Price or Redemption Price, in each  case  for
the  benefit  of  holders from time to time of  the  Exchangeable
Shares, and will cause the Corporation to use such funds,  assets
and  other property so segregated exclusively for the payment  of
dividends   and  the  payment  or  other  satisfaction   of   the
Liquidation Amount, the Retraction Price or the Redemption Price,
as  applicable, in each case in accordance with the  Exchangeable
Share Provisions.

2.3        Reservation of Orbital Common Shares.  Orbital  hereby
represents  and  warrants  that it has irrevocably  reserved  for
issuance  out of its authorized and unissued capital  stock  such
number  of  Orbital Common Shares as is equal to  the  number  of
Exchangeable   Shares  outstanding  immediately   following   the
Effective  Date  and covenants that at all times  in  the  future
while  any  Exchangeable  Shares are  outstanding  it  will  keep
available,  free from pre-emptive and other rights,  out  of  its
authorized  and  unissued capital stock such  number  of  Orbital
Common  Shares (or other shares or securities into which  Orbital
Common Shares may be reclassified or changed) as is necessary  to
enable  Orbital  and the Corporation to perform their  respective
obligations  pursuant to this agreement, the  Exchangeable  Share
Provisions and the Voting and Exchange Trust Agreement.

2.4        Notification of Certain Events.  In  order  to  assist
Orbital to comply with its obligations hereunder, the Corporation
will give, or cause the Transfer Agent to give, Orbital notice of
each of the following events at the time set forth below:

                    (a)  in the event of any determination by the
               Board of Directors of the Corporation to institute
               voluntary  liquidation, dissolution or winding  up
               proceedings with respect to the Corporation or  to
               effect any other distribution of the assets of the
               Corporation among its shareholders for the purpose
               of  winding up its affairs, at least 60 days prior
               to   the   proposed   effective   date   of   such
               liquidation,  dissolution,  winding  up  or  other
               distribution;

                     (b)   immediately, upon the earlier  of  (i)
               receipt by the Corporation of notice of, and  (ii)
               the  Corporation otherwise becoming aware of,  any
               threatened or instituted claim, suit, petition  or
               other  proceedings with respect to the involuntary
               liquidation,  dissolution or  winding  up  of  the
               Corporation or to effect any other distribution of
               the   assets   of   the  Corporation   among   its
               shareholders  for the purpose of  winding  up  its
               affairs;

                      (c)   immediately,  upon  receipt  by   the
               Transfer Agent of a Retraction Request; and

                    (d)  as soon as practicable upon the issuance
               by  the Corporation of any Exchangeable Shares  or
               rights to acquire Exchangeable Shares.

2.5        Delivery of Orbital Common Shares.  In furtherance  of
its  obligations  under subsections 2.1(e) and (f)  hereof,  upon
notice of any event that requires the Corporation to cause to  be
delivered  Orbital  Common Shares to any holder  of  Exchangeable
Shares,  Orbital shall forthwith issue and deliver the  requisite
Orbital Common Shares to or to the order of the former holder  of
the  surrendered  Exchangeable Shares, as the  Corporation  shall
direct.   All such Orbital Common Shares shall be duly issued  as
fully paid and non-assessable and shall be free and clear of  any
Liens.   In  consideration of the issuance of each  such  Orbital
Common  Share by Orbital, the Corporation shall issue to Orbital,
or  as Orbital shall direct, such number of common shares of  the
Corporation as is equal to the fair value of such Orbital  Common
Shares.

2.6        Qualification  of Orbital Common Shares.   Unless  the
staff  of  the  United States Securities and Exchange  Commission
(the  "SEC") has confirmed the availability of an exemption  from
registration under the United States Securities Act of  1933,  as
amended  (the "Securities Act") as to the issuance of the Orbital
Common Shares in exchange for the Exchangeable Shares pursuant to
the Plan of Arrangement, the Exchangeable Share Provisions or the
Voting and Exchange Trust Agreement, in response to the No Action
Request (as defined in the Combination Agreement) or Orbital  has
received  an  opinion of counsel reasonably satisfactory  to  the
Corporation  to  such  effect,  then  Orbital  shall  cause  such
issuance  to  be registered under the Securities Act,  and  shall
file a registration statement covering such issuance with the SEC
and  use  all  commercially  reasonable  efforts  to  cause  such
registration statement to become effective as soon as practicable
and  remain  effective  throughout the period  during  which  the
Exchangeable Shares may be exchanged in accordance with the  Plan
of  Arrangement, the Exchangeable Share Provisions or the  Voting
and  Exchange Trust Agreement.  Orbital agrees to file  any  such
required   registration   statement   as   soon   as   reasonably
practicable.  Orbital shall use all reasonable efforts to  obtain
all  orders  required  from  the applicable  Canadian  securities
authorities  to permit the issuance of the Orbital Common  Shares
upon  any  such  exchange  of  the  Exchangeable  Shares  without
registration or qualification with or approval of or  the  filing
of  any document including any prospectus or similar document  or
the  taking of any proceeding with or the obtaining of any order,
ruling  or  consent from any governmental or regulatory authority
under  any  Canadian federal or provincial law or  regulation  or
pursuant to the rules and regulations of any regulatory authority
or  the  fulfillment of any other legal requirement  before  such
Orbital  Common  Shares  may  be  issued  and  delivered  by  the
Corporation  or Orbital to the holder thereof or  in  order  that
such Orbital Common Shares may be freely traded thereafter (other
than  any restrictions on transfer by reason of a holder being  a
"control  person" of the Corporation or Orbital for  purposes  of
Canadian  federal or provincial securities law or an  "affiliate"
for purposes of United States Federal or state securities law).

2.7        Tender Offers, etc.  In the event that a tender offer,
share  exchange  offer,  issuer bid,  take-over  bid  or  similar
transaction with respect to Orbital Common Shares (an "Offer") is
proposed by Orbital or is proposed to Orbital or its stockholders
and  is recommended by the Board of Directors of Orbital,  or  is
otherwise effected or to be effected with the consent or approval
of  the  Board  of  Directors of Orbital, Orbital  will  use  all
commercially reasonable efforts expeditiously and in  good  faith
to  take all such actions and do all such things as are necessary
or  desirable to enable and permit holders of Exchangeable Shares
to  participate  in  such Offer to the  same  extent  and  on  an
economically  equivalent basis as the holders of  Orbital  Common
Shares,  without discrimination.  Without limiting the generality
of  the  foregoing, Orbital will use all commercially  reasonable
efforts expeditiously and in good faith to ensure that holders of
Exchangeable  Shares may participate in all such  Offers  without
being  required  to retract Exchangeable Shares  as  against  the
Corporation  (or,  if  so  required,  to  ensure  that  any  such
retraction shall be effective only upon, and shall be conditional
upon,  the  closing of the Offer and only to the extent necessary
to tender or deposit to the Offer).

2.8       Ownership of Outstanding Shares.  Orbital covenants and
agrees  in  favour  of  the Corporation  that,  as  long  as  any
outstanding Exchangeable Shares are owned by any person or entity
other than Orbital or any of its Affiliates, Orbital will be  and
remain the direct or indirect beneficial owner of all issued  and
outstanding shares in the capital of the Corporation (other  than
Exchangeable  Shares  and  the Class B Preferred  Shares  of  the
Corporation issued to Canadian Imperial Bank of Commerce pursuant
to  the  Arrangement)  and  all  outstanding  securities  of  the
Corporation  carrying or otherwise entitled to voting  rights  in
any circumstances (other than Exchangeable Shares and the Class B
Preferred  Shares of the Corporation issued to Canadian  Imperial
Bank  of  Commerce pursuant to the Arrangement),  unless  Orbital
shall have obtained the prior approval of the Corporation and the
holders  of  the  Exchangeable Shares given  in  accordance  with
section 8.2 of the Exchangeable Share Provisions.

2.9        Orbital  Not  To  Vote Exchangeable  Shares.   Orbital
covenants  and  agrees  that it will  appoint  and  cause  to  be
appointed  proxyholders with respect to all  Exchangeable  Shares
held  by  Orbital  and  its Affiliates for the  sole  purpose  of
attending each meeting of holders of Exchangeable Shares in order
to  be  counted  as  part of the quorum for  each  such  meeting.
Orbital  further covenants and agrees that it will not, and  will
cause its Affiliates not to, exercise any voting rights that  may
be  exercisable by holders of Exchangeable Shares  from  time  to
time pursuant to the Exchangeable Share Provisions or pursuant to
the  provisions  of  the CBCA with respect  to  any  Exchangeable
Shares  held by it or by its Affiliates in respect of any  matter
considered  at  any  meeting of holders of  Exchangeable  Shares,
including without limitation any approval to be given by  holders
of   Exchangeable  Shares  pursuant  to  section   8.2   of   the
Exchangeable Share Provision.

2.10       Due  Performance.  On and after  the  Effective  Date,
Orbital  shall  duly  and timely perform all of  its  obligations
provided   for   in  the  Plan  of  Arrangement,  including   any
obligations that may arise upon the exercise of Orbital's  rights
under the Exchangeable Share Provisions.

2.11      Economic Equivalence.  Orbital hereby acknowledges that
it  will  be  bound by any determination of economic  equivalence
made  by  the Board of Directors pursuant to section 5.6  of  the
Plan  of  Arrangement  or section 9.1 of the  Exchangeable  Share
Provisions, where applicable.


                           ARTICLE 3

                            GENERAL

3.1        Term.   This agreement shall come into  force  and  be
effective as of the date hereof and shall terminate and be of  no
further  force  and  effect  at  such  time  as  there   are   no
Exchangeable Shares (or securities or rights convertible into  or
exchangeable  for  or  carrying rights  to  acquire  Exchangeable
Shares) held by any party other than Orbital and its Affiliates.

3.2        Changes  in  Capital of Orbital and  the  Corporation.
Notwithstanding  the provisions of section  3.4  hereof,  at  all
times  after  the  occurrence of any event effected  pursuant  to
section  2.7  hereof as a result of which either  Orbital  Common
Shares or the Exchangeable Shares or both are in any way changed,
this  agreement  shall  forthwith  be  amended  and  modified  as
necessary  in  order  that it shall apply  with  full  force  and
effect,  mutatis  mutandis,  to all  new  securities  into  which
Orbital Common Shares or the Exchangeable Shares or both  are  so
changed  and  the  parties hereto shall execute  and  deliver  an
agreement  in  writing  giving  effect  to  and  evidencing  such
necessary amendments and modifications.

3.3        Severability.  If any provision of this  agreement  is
held  to  be  invalid,  illegal or unenforceable,  the  validity,
legality  or  enforceability of the remainder of  this  agreement
shall  not  in any way be affected or impaired thereby  and  this
agreement  shall  be  carried  out  as  nearly  as  possible   in
accordance with its original terms and conditions.

3.4        Amendments, Modifications, etc.   This  agreement  may
not  be  amended  or modified except by an agreement  in  writing
executed  by  the  Corporation and Orbital and  approved  by  the
holders  of  the Exchangeable Shares in accordance  with  section
10.2 of the Exchangeable Share Provisions.

3.5       Ministerial Amendments.  Notwithstanding the provisions
of  section  3.4, the parties to this agreement may  without  the
approval  of the holders of the Exchangeable Shares, at any  time
and  from time to time, amend or modify this agreement in writing
for the purposes of:

                     (a)   adding to the covenants of  either  or
               both parties for the protection of the holders  of
               the Exchangeable Shares;

                     (b)  making such amendments or modifications
               not  inconsistent with this agreement  as  may  be
               necessary or desirable with respect to matters  or
               questions  which, in the opinion of the  Board  of
               Directors of each of the Corporation and  Orbital,
               it  may  be expedient to make, provided that  each
               such  board  of directors shall be of the  opinion
               that such amendments or modifications will not  be
               prejudicial to the interests of the holders of the
               Exchangeable Shares; or

                     (c)   making  such  changes  or  corrections
               which, on the advice of counsel to the Corporation
               and  Orbital,  are  required for  the  purpose  of
               curing  or  correcting any ambiguity or defect  or
               inconsistent  provision or  clerical  omission  or
               mistake  or  manifest error herein, provided  that
               the boards of directors of each of the Corporation
               and  Orbital  shall  be of the opinion  that  such
               changes or corrections will not be prejudicial  to
               the  interests of the holders of the  Exchangeable
               Shares.

3.6        Meeting  to Consider Amendments.  The Corporation,  at
the  request of Orbital, shall call a meeting or meetings of  the
holders of the Exchangeable Shares for the purpose of considering
any   proposed  amendment  or  modification  requiring   approval
pursuant  to  section 3.4 hereof.  Any such meeting  or  meetings
shall  be called and held in accordance with the by-laws  of  the
Corporation and the Exchangeable Share Provisions.

3.7        Waivers  Only in Writing.  No waiver  of  any  of  the
provisions of this agreement otherwise permitted hereunder  shall
be  effective unless made in writing and signed by  both  of  the
parties hereto.

3.8        Inurement.  This agreement shall be binding  upon  and
inure  to  the benefit of the parties hereto and their respective
successors and permitted assigns.

3.9        Orbital Successors.  Orbital shall not enter into  any
transaction  (whether  by way of reconstruction,  reorganization,
consolidation,  merger,  transfer,  sale,  lease  or   otherwise)
whereby  all  or substantially all its undertaking, property  and
assets  would become the property of any other person or, in  the
case  of  a  merger,  of  the  continuing  corporation  resulting
therefrom, unless:

                      (a)    such   other  person  or  continuing
               corporation   is  a  corporation   (the   "Orbital
               Successor")  incorporated under the  laws  of  any
               state  of the United States or the laws of  Canada
               or any province thereof; and

                     (b)  the Orbital Successor, by operation  of
               law, becomes, without more, bound by the terms and
               provisions of this agreement or, if not so  bound,
               executes, prior to or contemporaneously  with  the
               consummation of such transaction, an agreement  to
               be bound by the provisions hereof as if it were an
               original  party hereto and to observe and  perform
               all  of  the covenants and obligations of  Orbital
               pursuant  to  this agreement, in form satisfactory
               to the Corporation, acting reasonably.

Nothing  herein shall be construed as preventing the amalgamation
or  merger of any wholly-owned subsidiary of Orbital with or into
Orbital.

3.10        Notices   to   Parties.   All   notices   and   other
communications between the parties shall be in writing and  shall
be  deemed  to  have  been given if delivered  personally  or  by
confirmed telecopy to the parties at the following addresses  (or
at such other address for either such party as shall be specified
in like notice):

                    (a)  if to Orbital at:


                         Orbital Sciences Corporation
                         21700 Atlantic Boulevard
                         Dulles, VA 20166

                         Attention: General Counsel

                                   Telecopy: (703) 406-5572

                    (b)  if to the Corporation at:

                         MacDonald Dettwiler Holdings Inc.
                         13800 Commerce Parkway
                         Richmond, British Columbia
                         V6V 2J3

                         Attention: #

                         Telecopy: (604) #

Any  notice  or  other  communication given personally  shall  be
deemed to have been given and received upon delivery thereof  and
if  given  by  telecopy shall be deemed to have  been  given  and
received on the date of confirmed receipt thereof unless such day
is  not  a Business Day in which case it shall be deemed to  have
been  given and received upon the immediately following  Business
Day.

3.11       Counterparts.   This  agreement  may  be  executed  in
counterparts, each of which shall be deemed an original, and  all
of  which  taken  together  shall constitute  one  and  the  same
instrument.

3.12       Jurisdiction.  This agreement shall be  construed  and
enforced  in accordance with the laws of the Province of  British
Columbia and the laws of Canada applicable therein.

3.13        Attornment.   Orbital  agrees  that  any  action   or
proceeding  arising out of or relating to this agreement  may  be
instituted  in  the  courts  of  British  Columbia,  waives   any
objection which it may have now or hereafter to the venue of  any
such   action   or   proceeding,  irrevocably  submits   to   the
jurisdiction of the said courts in any such action or proceeding,
agrees to be bound by any judgment of the said courts and not  to
seek,  and  hereby waives, any review of the merits of  any  such
judgment  by  the  courts  of any other jurisdiction  and  hereby
appoints  the  Corporation at its registered office as  Orbital's
attorney for service of process.

          IN WITNESS WHEREOF, the parties hereto have caused this
agreement to be duly executed as of the date first above written.


                                   ORBITAL SCIENCES CORPORATION


                                   by ___________________________


                                      ___________________________


                                   MACDONALD DETTWILER HOLDINGS
                                   INC.


                                   by ___________________________


                                      ___________________________





                          ARRANGEMENT

                           INVOLVING

            MacDONALD, DETTWILER AND ASSOCIATES LTD.

                      3173623 CANADA INC.

                              AND

                  ORBITAL SCIENCES CORPORATION







         NOTICE OF SPECIAL MEETING OF SHAREHOLDERS AND
       HOLDERS OF THE 1988 EMPLOYEE SHARE OPTIONS AND THE
               1988 KEY EMPLOYEE SHARE OPTIONS OF
            MacDONALD, DETTWILER AND ASSOCIATES LTD.


                              AND


                MANAGEMENT INFORMATION CIRCULAR


                        OCTOBER 6, 1995
<PAGE>

[MDA LETTERHEAD]


October 10, 1995

Dear Shareholder or Optionholder:

You  are cordially invited to attend a Special Meeting of Shareholders  and
holders  of 1988 Employee Share Options and 1988 Key Employee Share Options
(collectively,  the "MDA 1988 Optionholders") of MacDonald,  Dettwiler  and
Associates Ltd. ("MDA") to be held on Tuesday, November 14, 1995  at  MDA's
offices  located at 13800 Commerce Parkway, Richmond, British  Columbia  at
10:00 a.m. local time.  As described in the enclosed Proxy Circular, at the
Special  Meeting, the MDA Shareholders and MDA 1988 Optionholders  will  be
asked  to  consider and vote upon an Arrangement under section 192  of  the
Canada Business Corporation Act involving MDA, Orbital Sciences Corporation
("Orbital"),  and  317632  Canada  Inc.  ("Acquisition"),  a  wholly  owned
subsidiary  of Orbital.  Subject to any further order of the Supreme  Court
of British of Columbia, the Arrangement must be approved by the affirmative
vote of 66-2/3% of the votes actually cast thereon by MDA Shareholders  and
by MDA 1988 Optionholders, voting as separate classes.

The  MDA Board of Directors has carefully reviewed and considered the terms
and  conditions  of  the  proposed Arrangement.   The  Board  of  Directors
believes that the transaction is fair and in the best interests of MDA, MDA
Shareholders  and MDA 1988 Optionholders, and has unanimously approved  the
Arrangement.   The Board of Directors unanimously recommends that  the  MDA
Shareholders  and MDA 1988 Optionholders vote FOR the proposed  Arrangement
Resolution approving the Arrangement.

Under  the  Plan  of Arrangement, MDA will receive Exchangeable  Shares  of
Acquisition, which will have voting, dividend and liquidation  rights  that
are,  as  nearly  as  practicable, equivalent to those  of  Orbital  Common
Shares.  The number of Exchangeable Shares to be issued will be based  upon
an  Exchange  Ratio that is to be determined by dividing U.S.$5.41  by  the
average  closing  sale price of Orbital Common Shares for  the  twenty  day
period  ending  on the date four trading days prior to the Effective  Date,
and  may not be less than .2705 or greater than .3607.  The Effective  Date
is  expected  to occur shortly after the Special Meeting.  MDA Shareholders
will receive the number of Exchangeable Shares equal to the product of  the
Exchange Ratio multiplied by the number of MDA Common Shares held by  them.
Holders   of  MDA  Options,  including  MDA  1988  Options,  will   receive
Replacement  Options  entitling them to purchase  such  number  of  Orbital
Common Shares equal to the product of the Exchange Ratio multiplied by  the
number  of MDA Common Shares underlying such MDA Option, having an exercise
price  per share equal to the quotient of the exercise price per  share  of
such MDA Option divided by the Exchange Ratio, and having the same vesting,
expiration and other terms as such MDA Option.

The  accompanying  Proxy Circular provides a detailed  description  of  the
Arrangement and the business and financial information of MDA and Orbital.

MDA  retained  the investment banking firm of Nesbitt Burns Inc.  ("Nesbitt
Burns") to advise it on the acquisition transaction, including to advise it
with respect to the consideration to be paid by Orbital in the Arrangement.
Nesbitt  Burns  has  advised the MDA Board of Directors  that,  in  Nesbitt
Burns'  opinion, the consideration to be paid by Orbital in the Arrangement
is  fair  to  MDA Shareholders and MDA 1988 Optionholders from a  financial
point  of view.  A copy of Nesbitt Burns' opinion is attached to the  Proxy
Circular as Appendix "C".

Your  vote  on  this  matter is very important.   We  urge  you  to  review
carefully  the  enclosed  materials and  to  return  your  proxy  promptly.
Shareholders  with questions regarding the Arrangement  or  other   matters
described herein may contact Gordon Thiessen at (604) 278-3411.

Whether  or  not  you plan to attend the Special Meeting, please  sign  and
promptly return your proxy card in the enclosed postage paid envelope.   If
you attend the meeting, you may vote in person if you wish, even though you
have previously returned your proxy.

Sincerely,

/s/ John S. MacDonald                   /s/ Daniel E. Friedman

John S. MacDonald, Chairman             Daniel E. Friedman, President and
CEO
                                


                NOTICE OF SPECIAL GENERAL MEETING

NOTICE   IS   HEREBY   GIVEN   that   a  Special   General   Meeting   (the
"Special    Meeting")   of   holders   of   MDA   Common    Shares    ("MDA
Shareholders")   and   holders  of  options  ("MDA   1988   Optionholders")
under   the   1988   Employee  Share  Option  Plan   and   the   1988   Key
Employee   Share  Option  Plan  (together,  the  "MDA  1988  Options")   of
MacDonald,  Dettwiler  and  Associates  Ltd.  ("MDA")  will  be   held   at
the   offices   of  MDA  at  13800  Commerce  Parkway,  Richmond,   British
Columbia,  V6V  2J3,  on  Tuesday,  November  14,  1995  at  the  hour   of
10:00 a.m. (Vancouver time) for the following purposes:

(a)  to   consider,  pursuant  to  an  order  of  the  Supreme   Court   of
     British    Columbia    dated   October   6,   1995    (the    "Interim
     Order"),   and,  if  deemed  advisable  to  pass,  with   or   without
     variation,      a     special     resolution     (the     "Arrangement
     Resolution")   to   approve   an   arrangement   (the   "Arrangement")
     under   section   192   of  the  Canada  Business  Corporations   Act;
     and

(b)  to   transact   such  further  or  other  business  as  may   properly
     come before the Special Meeting or any adjournment thereof.

The   texts   of  the  Arrangement  Resolution,  the  Plan  of  Arrangement
and  the  agreements  in  respect  of the  Arrangement  are  set  forth  in
Appendices   "F,"   "A"   and  "B,"  respectively,  to   the   accompanying
Management Information Circular of MDA (the "Proxy Circular").

Pursuant  to  the  Interim  Order,  MDA  Shareholders  and  the  MDA   1988
Optionholders  have  been  granted  the  right  to  dissent  with   respect
to   the  Arrangement  and  to  be  paid  the  fair  value  of  their   MDA
Common  Shares  or  the  MDA  Common Shares  to  which  they  are  entitled
under  the  MDA  1988  Options, as the case  may  be,  in  respect  of  the
Arrangement   Resolution   in  accordance   with   section   190   of   the
Canada  Business  Corporations  Act.   This  right  is  described  in   the
Proxy Circular.

The   Board  of  Directors  has  fixed  October  10,  1995  as  the  record
date   for   determining  MDA  Shareholders  entitled  to  receive   notice
of   and  to  vote  at  the  Meeting.   Only  holders  of  record  of   MDA
Common  Shares  at  the  close  of  business  on  October  10,  1995   will
be  entitled  to  vote  in  respect of  the  matters  to  be  voted  on  at
the   Special   Meeting  or  any  adjournment  thereof,   except   that   a
person   who   has   acquired  MDA  Common  Shares   subsequent   to   such
record  date  will  be  entitled  to  vote  such  shares,  instead  of  the
holder   of   record,  upon  making  a  written  request  to  that   effect
not  later  than  10  days  preceding  the  date  of  the  Special  Meeting
to  the  Secretary  of  MDA  at  the  registered  office  of  MDA  at  26th
floor,    700   West   Georgia   Street,   Vancouver,   British   Columbia,
V7Y   1B3  and  establishing  that  such  person  owns  such  shares.   All
MDA   1988   Optionholders   on  the  date  of   mailing   of   the   Proxy
Circular  will  receive  Notice  of  the  Special  Meeting  and   all   MDA
1988   Optionholders  on  the  date  of  the  Special   Meeting   will   be
entitled to attend and vote at the Special Meeting.

MDA   Shareholders   and  MDA  1988  Optionholders  who   are   unable   to
attend  the  Special  Meeting  in  person  are  requested  to  sign,   date
and   return,   in   the   envelope  provided   for   that   purpose,   the
enclosed  instrument  of  proxy.   In  order  to  be  valid  for   use   at
the   Special   Meeting,  proxies  must  be  received  by  Montreal   Trust
Company    of    Canada,    510   Burrard   Street,   Vancouver,    British
Columbia,   V6C   3B9   not  less  than  48  hours  (excluding   Saturdays,
Sundays   and   holidays)   preceding   the   Special   Meeting   or    any
adjournment thereof.

DATED   at   Richmond,  British  Columbia,  this  6th   day   of   October,
1995.


                               BY ORDER OF THE BOARD OF DIRECTORS




                                      ROBERT B. WALLIS, Secretary
<PAGE>
                       TABLE OF CONTENTS

                                                             Page



MANAGEMENT INFORMATION CIRCULAR                                 1

GLOSSARY OF TERMS                                               2

MDA AND ORBITAL REPORTING CURRENCIES AND ACCOUNTING PRINCIPLES  7

CANADIAN/U.S. EXCHANGE RATES                                    7

SUMMARY OF PROXY CIRCULAR                                       8
          General                                               8
          The Arrangement and The Combination Agreement         8
          Certain Canadian Federal Income Tax Considerations   11
          Certain   United   States  Federal  Income
          Tax   Considerations                                 12
          The Special Meeting                                  13
          Business of Orbital                                  14
          Business of MDA                                      16

MARKET PRICE AND DIVIDEND INFORMATION                          17

SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA                18
          Selected Historical Consolidated Financial Data of
          MDA                                                  18
          Selected    Historical    Consolidated
          Financial    Data    of       Orbital                19

PRO FORMA FINANCIAL INFORMATION                                20

PRO FORMA CONSOLIDATED CAPITALIZATION                          27

RISK FACTORS                                                   28
          Technologically Advanced Products and Services       28
          Dependence on United States Government               28
          Capital Requirements                                 28
          Regulation                                           29

THE SPECIAL MEETING - GENERAL PROXY INFORMATION                30
          General                                              30
          Solicitation of Proxies                              30
          Appointment of Proxies                               30
          Signing of Proxies                                   30
          Revocation of Proxies                                30
          Voting of Proxies                                    31
          MDA Common Shares                                    31
          MDA 1988 Options                                     31
          Required   Votes   to   Approve  the   Arrangement
          and   Voting  Intentions of Certain Shareholders
          and Optionholders                                    31
          Principal   Holders   of  MDA  Common   Shares
          and   MDA   1988    Options                          32

THE ARRANGEMENT AND THE COMBINATION AGREEMENT                  32
          The Arrangement - General                            32
          Background of the Arrangement                        33
          MDA's   Reasons   for   the   Arrangement   and
          Recommendations of the MDA Board                     35
          Orbital's Reasons for the Arrangement                35
          Operations Following the Arrangement                 36
          Interests of Certain Persons in the Arrangement      36
          Opinion of MDA's Financial Advisor                   36
          Plan of Arrangement                                  39
          Post-Combination Share Ownership                     40
          Qualifying Holdcos                                   40
          Dissenting Holders                                   40
          Description of Exchangeable Shares                   40
                Voting Rights                                  41
                Dividend Rights                                41
                Retraction, Redemption and Exchange Right      42
                Deduction and Remittance of Withholding Tax    43
                Anti-dilution and Capital Reorganizations      44
          Support Agreement                                    44
          Market    for    Orbital   Common   Shares
          and    Exchangeable   Shares                         45
          The Combination Agreement                            45
                  Actions to be Taken Prior to the Effective
                  Time                                         45
                  Business of MDA Pending the Arrangement      45
                  Solicitation of Alternate Transactions       46
                  Conditions to the Arrangement                46
                  Termination and Amendment                    47
                   Fees, Expenses and  Indemnification         47
          Confidentiality Agreement                            48
          Agreements of MDA Affiliates                         48
          Court Approval and Completion of the Arrangement     48
          Accounting Treatment                                 49
          Stock Exchange Listings                              49
                 Exchangeable Shares                           49
                 Orbital Common Shares                         49
          Eligibility for Investment in Canada                 49
                 Exchangeable Shares                           49
                 Voting Rights and Exchange Right              49
                 Orbital Common Shares                         49
          Resale   of   Exchangeable  Shares  and  Orbital
          Common   Shares  Received in the Arrangement         50
                 Canada                                        50
                 United States                                 50
          Procedures   for   Exchange   of  Share
          Certificates   by   MDA   Shareholders               51
               Return to Depositary of Letter of Transmittal   51
               Election to Immediately Exchange
               Exchangeable Shares for Orbital Common Shares   51
               Fractional Shares                               52
               Failure to Deposit Certificates Representing
               MDA Common Shares                               52
          Confirmation of Replacement Options                  52

INCOME TAX CONSIDERATIONS TO MDA SHAREHOLDERS AND
        OPTIONHOLDERS                                          52
          Canadian Federal Income Tax Considerations           52
          Holders of MDA Common Shares Resident in Canada      53
          Holders of MDA Common Shares Not Resident in Canada  57
                MDA 1988 Optionholders                         58
          United States Federal Income Tax Considerations      58
          Taxation of U.S. Holders                             59
          Shareholders Not Resident in or Citizens of the
                United States                                  62
          Information, Reporting and Backup Withholding        63

INFORMATION CONCERNING ACQUISITION                             63

INFORMATION CONCERNING ORBITAL                                 63
          Background and Recent Acquisitions                   63
          Description Of Orbital's Products And Services       64
               Launch Systems                                  65
               Space and Electronics Systems                   66
               Communications and Information Systems          67
          Competition                                          70
          Research and Development                             71
          Backlog and Contracts                                71
          Properties                                           72
          Environmental Regulation                             73
          Insurance                                            73
          Litigation                                           73
          Management's    Discussion    and    Analysis    of
             Financial Condition and Results of Operations     73
                 Overview                                      73
                 Adoption of New Accounting Standard           74
               Results of Operations for the Six-Month Periods
                        Ended June 30, 1995 and 1994           76
               Results of Operations for the Years Ended
                December 31, 1994, 1993 and 1992               77
               Liquidity and Capital Resources                 79
          Management and Employees                             80
              Executive Officers and Directors                 80
              Indebtedness of Directors and Officers           81
              Employees                                        81
          Description of Capital                               82
              Capitalization                                   82
              Common Shares                                    82
              Preferred Shares                                 82
          Dividend Policy                                      83
          Transfer Agent                                       83
          Independent Auditors                                 83

INFORMATION CONCERNING MDA                                     83
          Business                                             83
                Subsidiary Companies                           83
                General                                        84
                Geo-Information Systems                        84
                Aviation Systems                               85
                Space and Defence Systems                      86
                Communications                                 87
          Contract Pricing and Completion                      87
          Marketing and Sales                                  87
          Competition                                          89
          Research and Development                             89
          Patents and Licenses                                 89
          Personnel                                            90
          Properties                                           90
          Management's    Discussion    and    Analysis    of
             Financial Condition and Results of Operations     90
               Results of Operations for the Quarter ended
               June 30, 1995 and Quarter Ended June 30, 1994   90
               Results of Operations for the Fiscal Years
               ended March 31, 1995 and 1994                   90
               Results of Operations for the Fiscal Years ended
                March 31, 1994 and 1993                        91
          Directors and Officers                               92
          Description of Share Capital                         93
          Dividend Record and Dividend Policy                  93
          Executive Compensation                               94
              Summary Compensation Table                       94
              Long-Term Incentive Plan Compensation            94
              Pensions                                         95
          Auditors                                             95
          Registrar and Transfer Agent                         96
          Stock Exchange Listings                              96

COMPARISON OF SHAREHOLDERS' RIGHTS                             96
          Extraordinary Transactions - Vote Required           96
          Amendment to Governing Documents                     97
          Dissent Rights                                       98
          Oppression Remedy                                    98
          Derivative Action                                    99
          Shareholder Consent in Lieu of Meeting               99
          Director Qualifications                              99
          Fiduciary Duties of Directors                        99
          Indemnification of Officers and Directors           100
          Director Liability                                  100
          Anti-takeover     Provisions    and    Interested
           Stockholder     Transactions                       100
          Shareholder Protection Rights Plan                  101

DISSENTING RIGHTS                                             101

AVAILABLE INFORMATION                                         104

LEGAL MATTERS                                                 104

APPROVAL OF PROXY CIRCULAR BY MDA BOARD OF DIRECTORS          104

ANNEX "I"      Orbital's Consolidated Financial Statements and
                Quarterly Report on Form 10-Q for the
                Quarter Ended June 30, 1995                     F-1 (OMITTED)

ANNEX "II"      MDA's Financial Statements                      F-39 (OMITTED)
ANNEX "III"    Excerpt of Orbital's Proxy Statement for 1995
                Annual Meeting of Stockholders                  P-1 (OMITTED)
APPENDIX "A"   Plan of Arrangement                              A-1
APPENDIX "B"   Combination Agreement                            B-1
APPENDIX "C"   Opinion of Nesbitt Burns                         C-1 (OMITTED)
APPENDIX "D"   Interim Order                                    D-1 (OMITTED)
APPENDIX "E"   Notice    of   Application   for   Final   Order
               to the Supreme Court (British Columbia)          E-1 (OMITTED)
APPENDIX "F"   Arrangement Resolution                           F-1 (OMITTED)
APPENDIX "G"   Section 190 of the CBCA                          G-1 (OMITTED)

<PAGE>
            MacDONALD, DETTWILER and ASSOCIATES LTD.
                                
                                
                 MANAGEMENT INFORMATION CIRCULAR
                                
                                

This   Proxy   Circular   is  being  furnished   to   holders   of   Common
Shares   of  MDA  and  MDA  1988  Optionholders  in  connection  with   the
solicitation   of   proxies  by  management  of  MDA   for   use   at   the
Special  Meeting  to  be  held  at  10:00 a.m.,  local  time,  on  Tuesday,
November   14,   1995,   at   the  offices  of  MDA   at   13800   Commerce
Parkway,    Richmond,   British   Columbia,   V6V   2J3,   and    at    any
adjournment thereof.

At    the    Special    Meeting,   MDA   Shareholders    and    MDA    1988
Optionholders  will  be  asked  to  consider  and  vote  upon  a   proposal
to  approve  an  arrangement  under  section  192  of  the  CBCA  involving
MDA   and   its  shareholders  and  optionholders  and  to  transact   such
further  or  other  business  as  may  properly  come  before  the  meeting
or any adjournment thereof.

MDA   Shareholders  and  MDA  1988  Optionholders  are   being   asked   to
approve    the   Arrangement   under   the   CBCA.    Pursuant    to    the
Arrangement,    MDA   will   become   a   wholly   owned   subsidiary    of
Acquisition   and   each   outstanding   MDA   Common   Share    will    be
exchanged   for   a   number   of  Exchangeable   Shares   of   Acquisition
equal   to   the   Exchange   Ratio.    The   Exchange   Ratio   will    be
determined   by   dividing  US$5.41  by  the  average  closing   price   of
Orbital  Common  Shares  for  the  20  trading  days  ending  on  the  date
four  trading  days  prior  to  the  Effective  Date  of  the  Arrangement,
provided  that  the  Exchange  Ratio  will  not  be  less  than  0.2705  or
greater    than    0.3607.    Outstanding   MDA   Options    will    become
Replacement   Options   to   acquire  Orbital  Common   Shares   on   terms
identical    to    the    existing    MDA   Options,    with    appropriate
adjustments   in   the   exercise  price   and   the   number   of   shares
subject   to   such   options   to  reflect  the   Exchange   Ratio.    The
Exchangeable   Shares   will   have  voting,   dividend   and   liquidation
rights   that   are,  as  nearly  as  practicable,  equivalent   to   those
rights of the Orbital Common Shares.

Holders   of   Exchangeable  Shares  will  have  the  right   to   exchange
all   or   any   of   such   shares  for  an  equal  number   (subject   to
adjustment    in    the   event   of   certain   capital   and    corporate
reorganizations)   of   Orbital   Common   Shares   plus    the    Dividend
Amount   attributable  to  such  shares,  at  any   time   prior   to   the
Automatic   Redemption  Date  and  subject  to  certain  Call   Rights   of
Orbital.    The   Exchangeable  Shares  will  be  automatically   exchanged
on   the   Automatic   Redemption  Date  and   upon   the   occurrence   of
certain   events,  including  the  liquidation,  dissolution  or   winding-
up   of  Orbital  or  Acquisition  or  the  default  by  Acquisition  under
the   Exchangeable  Share  Provisions.   Acquisition  has  the   right   to
accelerate   the   Automatic  Redemption  Date  upon   75   days'   written
notice   to   the  holders  of  Exchangeable  Shares  at  any   time   when
there   are   outstanding  less  than  400,000  Exchangeable  Shares   held
by persons other than Orbital and its Affiliates.

                                

This   Proxy   Circular  and  the  accompanying  forms  of  proxy,   Letter
of   Transmittal  and  Notice  of  Guaranteed  Delivery  are  first   being
mailed  to  MDA  Shareholders  and  MDA  1988  Optionholders  on  or  about
October 11, 1995.

                                

All   information  in  this  Proxy  Circular  relating  to  MDA  has   been
supplied   by   MDA.    All  information  relating  to   Orbital   Sciences
Corporation    and    Acquisition   has   been   supplied    by    Orbital.
Orbital   has   reviewed   all   information   relating   to   itself   and
Acquisition  after  its  inclusion  in  this  Proxy  Circular.    MDA   has
not    made    any    independent    investigations    and    assumes    no
responsibility    for    the    accuracy   or    completeness    of    such
information.     Certain   capitalized   terms   used   in    this    Proxy
Circular   without   definition   have   the   meanings   given   in    the
Glossary of Terms found at page 2.

See   "Risk   Factors"   for  certain  considerations   relevant   to   MDA
Shareholders   and  MDA  1988  Optionholders  regarding   the   Arrangement
and their investment in the securities referred to herein.

No   person  is  authorized  to  give  any  information  or  to  make   any
representation  not  contained  in  this  Proxy  Circular  and,  if   given
or   made,  such  information  or  representation  should  not  be   relied
upon   as   having   been  authorized.   This  Proxy  Circular   does   not
constitute   an  offer  to  sell,  or  a  solicitation  of  an   offer   to
purchase,  any  securities,  or  the  solicitation  of  a  proxy,  by   any
person  in  any  jurisdiction  in  which  such  an  offer  or  solicitation
would   be   unlawful  or  in  which  the  person  making  such  offer   or
solicitation  is  not  qualified  to  do  so  or  to  any  person  to  whom
it  is  unlawful  to  make  such  an offer  or  solicitation  of  an  offer
to   purchase   or   proxy   solicitation.   Neither   delivery   of   this
Proxy  Circular  nor  any  distribution  of  the  securities  referred   to
in   this  Proxy  Circular  shall,  under  any  circumstances,  create   an
implication  that  there  has  been  no  change  in  the  information   set
forth herein since the date of this Proxy Circular.
                        GLOSSARY OF TERMS

The  following  terms  have  the  following  meanings  when  used  in  this
Proxy   Circular  (including  the  summary).   These  defined   terms   are
not   used   in  the  consolidated  financial  statements  of  either   MDA
or Orbital attached as annexes hereto.

"1933   Securities  Act"  means  the  United  States  Securities   Act   of
1933,   including   all   regulations  made  thereunder,   all   amendments
to  such  statute  or  regulations from  time  to  time,  and  any  statute
or   regulation   that   supplements  or   supersedes   such   statute   or
regulation.

"1934   Securities  Exchange  Act"  means  the  United  States   Securities
Exchange   Act   of  1934,  including  all  regulations  made   thereunder,
all   amendments  to  such  statute  or  regulations  from  time  to  time,
and   any  statute  or  regulation  that  supplements  or  supersedes  such
statute or regulation.

"Acquisition"   means   3173623   Canada   Inc.,   a   newly   incorporated
subsidiary of Orbital, existing under the CBCA.

"Acquisition   Class   B   Preferred   Shares"   means    the    Class    B
Preferred   Shares   of   Acquisition  having   the   rights,   privileges,
restrictions  and  conditions  set  forth  in  Appendix  A  to   the   Plan
of Arrangement.

"Acquisition    Common    Shares"    means    the    Common    Shares    of
Acquisition    having    the   rights,   privileges,    restrictions    and
conditions set forth in Appendix A to the Plan of Arrangement.

"Affiliate"   of   any   person  means  any  other   person   directly   or
indirectly   controlling,   controlled  by,   or   under   common   control
with,    that    person.    For   the   purposes   of   this    definition,
"control"    (including,    with   correlative    meanings,    the    terms
"controlling,"   "controlled  by"  and  "under   common   control   with"),
as  applied  to  any  person,  means  the  possession  by  another  person,
directly   or   indirectly,  of  the  power  to   direct   or   cause   the
direction   of  the  management  and  policies  of  that  first   mentioned
person,   whether   through  the  ownership  of   voting   securities,   by
contract or otherwise.

"Affiliate   Agreements"  means  the  agreements   entered   into   between
Orbital   and   persons   who  are  deemed  to  be  "affiliates"   of   MDA
within   the   meaning  of  the  1933  Securities  Act,  substantially   in
the    forms   attached   as   Exhibits   6.2.4(A)   and   (B)    to    the
Combination Agreement.

"Arrangement"  means  the  arrangement  under  section  192  of  the   CBCA
on  the  terms  and  subject to the conditions  set  out  in  the  Plan  of
Arrangement,   subject  to  any  amendments  thereto  made  in   accordance
with   section   6.1  of  the  Plan  of  Arrangement   or   made   at   the
direction of the Court in the Final Order.

"Arrangement    Resolution"   means   the   resolution    concerning    the
Arrangement  in  the  form  set  forth  in  Appendix  "F"  to  this   Proxy
Circular.

"Automatic   Redemption   Date"  means  the  fifth   anniversary   of   the
Effective  Date,  unless  such  date  shall  be  accelerated  at  any  time
to   a   specified   earlier   date  by   the   board   of   directors   of
Acquisition   upon  at  least  75  days'  prior  written  notice   to   the
registered   holders   of   Exchangeable  Shares,   in   which   case   the
Automatic   Redemption   Date  shall  be  such  earlier   date;   provided,
however,   that   the   board   of  directors   of   Acquisition   may   so
accelerate   the   Automatic  Redemption  Date  only  at   such   time   as
there   are  outstanding  fewer  than  400,000  Exchangeable  Shares   held
by holders other than Orbital and its Affiliates.

"Average   Closing  Price"  means  the  average  closing  sales  price   of
Orbital  Common  Shares  for  the  20  trading  days  ending  on  the  date
four   trading   days  prior  to  the  Effective  Date,  as   reported   on
NASDAQ.

"Business  Day"  means  any  day other than  a  Saturday,  a  Sunday  or  a
day  when  banks  are  not  open for business in  either  or  both  of  the
Commonwealth of Virginia and Vancouver, British Columbia.

"CBCA"   means   the  Canada  Business  Corporations  Act,   R.S.C.   1985,
c.C-44,   including  all  regulations  made  thereunder,   all   amendments
to  such  statute  or  regulations from  time  to  time,  and  any  statute
or   regulation   that   supplements  or   supersedes   such   statute   or
regulation.

"Call   Rights"  means  collectively,  the  Liquidation  Call  Right,   the
Redemption Call Right and the Retraction Call Right.

"Canadian   dollars"  and  "Cdn$,"  "dollars"  and  "$"  mean  the   lawful
currency of Canada.

"Canadian   GAAP"  means  generally  accepted  accounting   principles   in
Canada.

"Canadian   Tax   Act"   means  the  Income  Tax   Act   (Canada),   R.S.C.
1985,    c.1    (5th   Supplement),   including   all   regulations    made
thereunder,   all   amendments  to  such  statute   or   regulations   from
time   to  time,  and  any  statute  or  regulation  that  supplements   or
supersedes such statute or regulation.

"Change   of  Control  Agreements"  means  the  agreements  to  be  entered
into   between   Orbital  and  certain  employees  of   MDA   substantially
in    the   form   attached   as   Exhibit   6.2.5   to   the   Combination
Agreement.

"Combination    Agreement"   means   the   Combination   Agreement    among
Orbital,   Acquisition   and  MDA  dated  as  of   August   31,   1995   as
amended   on   September  29,  1995,  a  copy  of  which  is  appended   as
Appendix "B" hereto.

"Court" means the Supreme Court of British Columbia.

"DGCL"   means   the   General   Corporation   Law   of   the   State    of
Delaware,   including  all  amendments  to  such  statute  from   time   to
time,    and    any    statute   or   regulation   that   supplements    or
supersedes such statute.

"Depositary"   means   Montreal   Trust   Company   of   Canada,   at   its
office set out in the Letter of Transmittal.

"Dissenting   MDA   Shareholders"   means   MDA   Shareholders   who   have
exercised   a   right   of   dissent  in   respect   of   the   Arrangement
Resolution  in  strict  compliance  with  section  190  of  the  CBCA   and
the Interim Order.

"Dissenting   MDA   1988  Optionholders"  means  MDA   1988   Optionholders
who   have   exercised   a   right   of   dissent   in   respect   of   the
Arrangement   Resolution  in  strict  compliance  with   section   190   of
the CBCA and the Interim Order.
"Dividend   Amount"  means  an  amount  equivalent  to  the   full   amount
of   declared  and  unpaid  dividends  on  the  Exchangeable  Shares   plus
all   dividends   declared  on  Orbital  Common  Shares   that   have   not
been   declared  on  the  Exchangeable  Shares  in  accordance   with   the
Exchangeable Share Provisions.

"Effective   Date"  means  the  date  on  which  the  Arrangement   becomes
effective   as  established  by  the  date  of  issue  of  the  certificate
of   amendment  in  respect  of  the  Plan  of  Arrangement  to  be  issued
by   the  Director  under  the  CBCA  pursuant  to  subsection  192(7)   of
the CBCA.

"Effective   Time"   means   12:01   a.m.   (Vancouver   time)    on    the
Effective Date.

"Employment   Agreements"   means   the   employment   agreements   to   be
entered   into   between   MDA  and  certain  officers   substantially   in
the form attached as Exhibit 3.18 to the Combination Agreement.

"Exchange   Ratio"   is   equal  to  US$5.41   divided   by   the   Average
Closing   Price,  provided  that  in  no  event  shall  it  be  less   than
0.2705 or greater than 0.3607.

"Exchange  Right"  means  the  right of  the  Trustee,  on  behalf  of  the
holders    of   Exchangeable   Shares   other   than   Orbital   and    its
Affiliates,    to   require   Orbital   to   purchase   the    Exchangeable
Shares   upon   the  occurrence  of  certain  events  as  stated   in   the
Voting and Exchange Trust Agreement.

"Exchangeable    Share   Provisions"   means   the   rights,    privileges,
restrictions   and   conditions  attaching  to  the  Exchangeable   Shares,
which are set forth in Appendix A to the Plan of Arrangement.

"Exchangeable   Shares"  means  the  Exchangeable  Non-Voting   Shares   of
Acquisition    having    the   rights,   privileges,    restrictions    and
conditions set forth in the Exchangeable Share Provisions.

"Final   Order"   means  the  final  order  of  the  Court  approving   the
Arrangement.

"Holding   Company  Agreements"  means  the  agreements   to   be   entered
into   among   Acquisition,   the   respective   Qualifying   Holdcos   and
their   shareholders,  substantially  in  the  form  attached  as   Exhibit
2.1.2 to the Combination Agreement.

"Insolvency    Event"   means   the   dissolution    or    winding-up    of
Acquisition,   any   insolvency   or   bankruptcy   proceeding   instituted
by   or   against   Acquisition,  including  any  such   proceeding   under
the    Companies'    Creditor   Arrangement   Act    (Canada)    and    the
Bankruptcy   and  Insolvency  Act  (Canada),  the  admission   in   writing
by   Acquisition   of  its  inability  to  pay  its  debts   generally   as
they  become  due  and  the  inability  of  Acquisition,  as  a  result  of
solvency   requirements   of   the  CBCA,  to   redeem   any   Exchangeable
Shares tendered for retraction.

"Interim  Order"  means  the  interim  order  of  the  Court,  a  copy   of
which is appended to this Proxy Circular as Appendix "D".

"Letter   of  Transmittal"  means  the  letter  of  transmittal   for   use
by  MDA  Shareholders.   A  copy  is  enclosed  with  this  Proxy  Circular
and    additional    copies   are   available   on   request    from    the
Depositary.

"Liquidation   Call   Right"  means  the  overriding  right   of   Orbital,
in   the   event   of   and   notwithstanding  the  proposed   liquidation,
dissolution,   winding-up  or  insolvency  of  Acquisition,   to   purchase
from   all   but   not  less  than  all  of  the  holders  of  Exchangeable
Shares  all  but  not  less  than  all  of  the  Exchangeable  Shares  held
by   each  such  holder,  as  more  particularly  described  in  the   Plan
of Arrangement.

"MDA"    means    MacDonald,    Dettwiler   and    Associates    Ltd.,    a
corporation   existing   under  the  CBCA,  and  where   the   context   so
requires, means MDA and its subsidiaries.

"MDA Board" means the board of directors of MDA.

"MDA  Common  Shares"  means  the  common  shares  of  MDA,  together  with
all Rights.

"MDA   Options"   means   collectively,  the  options   outstanding   under
the  MDA  1988  Option  Plans,  the  Key Employee  Share  Option  Plan  and
the Amended and Restated Key Employee Share Option Plan.

"MDA   1988   Option  Plans"  means  together,  the  1988  Employee   Share
Option  Plan  of  MDA  and  the  1988 Key Employee  Share  Option  Plan  of
MDA.

"MDA 1988 Optionholder" means a holder of an MDA 1988 Option.

"MDA   1988   Options"   means  the  options   to   purchase   MDA   Common
Shares issued under the MDA 1988 Option Plans.

"MDA Shareholder" means a holder of record of MDA Common Shares.

"NASDAQ"   means   the   National   Association   of   Securities   Dealers
Automated Quotation National Market System.

"Nesbitt   Burns"   means  Nesbitt  Burns  Inc.,   financial   advisor   to
MDA.

"Orbital"    means    Orbital   Sciences   Corporation,    a    corporation
existing  under  the  laws  of  the  State  of  Delaware,  and  where   the
context so requires, means Orbital and its subsidiaries.

"Orbital   Common  Shares"  means  the  common  stock,   par   value   $.01
per share, of Orbital.

"Plan   of   Arrangement"   means   the  plan   of   arrangement   proposed
under  section  192  of  the  CBCA,  substantially  in  the  form  attached
to   this  Proxy  Circular  as  Appendix  "A,"  as  amended,  modified   or
supplemented from time to time in accordance with its terms.

"Proxy    Circular"    means   this   Management    Information    Circular
including   the   Annexes   and  Appendices   attached   hereto   and   all
amendments and supplements hereto from time to time.

"PSC" means The PSC Communications Group, a division of MDA.

"Qualifying  Holdco"  means  a  corporation  that  shall  have   become   a
party  to  the  Plan  of  Arrangement prior to  the  date  of  the  Special
Meeting   pursuant   to  the  Plan  of  Arrangement   and   in   accordance
with   the   terms   of   the   Combination  Agreement   and   shall   have
satisfied   all  the  conditions  under  its  respective  Holding   Company
Agreement    to   the   satisfaction   of   Acquisition   in    its    sole
discretion.

"Redemption  Call  Right"  means  the  overriding  right  of  Orbital,   in
the    event   of   and   notwithstanding   a   proposed   redemption    of
Exchangeable  Shares  by  Acquisition,  to  purchase  from  all   but   not
less  than  all  of  the  holders  of  Exchangeable  Shares  all  but   not
less   than   all   of   the  Exchangeable  Shares  held   by   each   such
holder,    as    more   particularly   described    in    the    Plan    of
Arrangement.

"Replacement   Option"   means  an  option  to  purchase   Orbital   Common
Shares issued or granted in replacement of a MDA Option.

"Retraction  Call  Right"  means  the  overriding  right  of  Orbital,   in
the   event   of   and   notwithstanding  a  request   by   a   holder   of
Exchangeable  Shares  for  Acquisition  to  redeem  any  or  all   of   the
Exchangeable   Shares  registered  in  the  name   of   such   holder,   to
purchase   all   but   not  less  than  all  of  the  Exchangeable   Shares
that   are  the  subject  of  such  request  directly  from  such   holder,
as more particularly described in the Plan of Arrangement.

"Rights"   means   all  rights  associated  with  the  Common   Shares   in
the   capital   of   MDA,   including   without   limitation   all   rights
associated   with   such  Common  Shares  pursuant   to   the   Shareholder
Protection Rights Plan.

"SEC" means the United States Securities and Exchange Commission.

"SFAS"     means    the    Financial    Accounting    Standards     Board's
statements of financial accounting standards.

"Shareholder    Protection    Rights   Plan"    means    the    Shareholder
Protection   Rights   Plan  Agreement  dated  as   of   August   27,   1992
between   MDA   and   Montreal  Trust  Company   of   Canada,   as   Rights
Agent, as amended from time to time.

"Special   Meeting"  means  the  meeting  of  MDA  Shareholders   and   MDA
1988   Optionholders  to  be  held  on  Tuesday,  November  14,   1995   to
consider   the   Arrangement  Resolution  and  to  transact  such   further
and   other  business  as  may  properly  come  before  the  meeting,   and
any adjournment thereof.

"Special  Voting  Share"  means  the  one  Series  A  Preferred  Share   of
Orbital  to  be  issued  to  the  Trustee by  Orbital  in  connection  with
the   Arrangement  and  to  be  held  by  the  Trustee  pursuant   to   the
terms of the Voting and Exchange Trust Agreement.

"Support   Agreement"   means   the   agreement   to   be   entered    into
between    Acquisition    and    Orbital    in    connection    with    the
Arrangement  substantially  in  the  form  attached  as  Exhibit   2.3   to
the Combination Agreement.

"TSE" means The Toronto Stock Exchange.

"Trustee" means State Street Bank and Trust Company.

"U.S.   dollars"  and  "US$"  mean  the  lawful  currency  of  the   United
States.

"U.S.   GAAP"  means  generally  accepted  accounting  principles  in   the
United States.

"Voting   Agreements   and   Irrevocable  Proxy"   means   the   agreements
between   certain  directors,  officers  and  shareholders   of   MDA   and
Orbital   relating   to  the  voting  by  such  persons   of   MDA   Common
Shares held by them on the Arrangement Resolution.

"VSE" means the Vancouver Stock Exchange.

"Voting   and  Exchange  Trust  Agreement"  means  the  agreement   to   be
entered    into    as    of   the   Effective   Date    between    Orbital,
Acquisition   and   the   Trustee  in  connection  with   the   Arrangement
substantially   in   the   form   attached   as   Exhibit   2.2   to    the
Combination Agreement.

"Voting   Rights"  means  the  voting  rights  attached  to   the   Special
Voting   Share  exercisable  by  the  Trustee  at  the  direction  of   the
holders   of   Exchangeable  Shares  pursuant   to   the   terms   of   the
Voting and Exchange Trust Agreement.


              MDA AND ORBITAL REPORTING CURRENCIES
                    AND ACCOUNTING PRINCIPLES

The   financial  information  related  to  MDA  contained  in  this   Proxy
Circular  is  reported  in  Canadian  dollars  and  has  been  prepared  in
accordance   with   Canadian  GAAP,  which  differs  in  certain   respects
from U.S. GAAP.

The   financial   information  related  to  Orbital,  including   the   pro
forma   financial  information,  contained  in  this  Proxy   Circular   is
reported  in  U.S.  dollars  and  has  been  prepared  in  accordance  with
U.S.   GAAP,  which  differs  in  certain  respects  from  Canadian   GAAP.
See   Notes   2   and  G  to  the  pro  forma  financial   information   of
Orbital   for   an   explanation   of  the   relevant   major   differences
between U.S. GAAP and Canadian GAAP.


                  CANADIAN/U.S. EXCHANGE RATES

In   this   Proxy  Circular,  dollar  amounts  are  expressed   either   in
"Canadian  dollars,"  "Cdn$,"  "$"  or  "dollars"  or  in  "U.S.   dollars"
or "US$."

According   to   Reuters   Historical   Data   for   calendar    1992    to
calendar   1994  and  for  the  nine  months  ended  September  30,   1995,
the  high  and  low  exchange  rates  (i.e.  the  rate  at  which  Canadian
dollars   were   sold  for  U.S.  dollars),  the  average   exchange   rate
(i.e.  the  average  of  the  exchange  rates  on  the  last  day  of  each
month  during  the  period)  and  the  end-of-period  exchange  rates   for
one   Canadian   dollar  expressed  in  U.S.  dollars   for   the   periods
indicated are set forth below:

<TABLE>
<CAPTION>
                     Twelve          Nine Months Ended
                     Months              September 30,
                     Ended
                        
                    December
                      31,
                    _______     _________________________
                       1992     1993     1994        1995
                      US$       US$      US$         US$
<S>                 <C>      <C>       <C>         <C>
High for period      0.8485   0.7994   0.7567      0.7446
Low for period       0.7725   0.7417   0.7097      0.7009
End of period        0.7866   0.7566   0.7133      0.7410
Average for          0.8249   0.7737   0.7302      0.7288
period

</TABLE>

On  September  29,  1995, the noon buying rate for  Cdn$1.00  was
US$0.7442.
                   SUMMARY OF PROXY CIRCULAR

The  following  is  a  summary of certain information  about  the
Arrangement, MDA, Orbital and Acquisition and is qualified in its
entirety  by  reference to the full text of this Proxy  Circular,
including  the  annexes and appendices hereto.  MDA  Shareholders
and MDA 1988 Optionholders are urged to read this Proxy Circular,
including  the  accompanying  annexes  and  appendices,  in   its
entirety.  See "Risk Factors" for certain information that should
be  considered  by  MDA Shareholders and MDA 1988  Optionholders.
For the definitions of certain terms used in this Proxy Circular,
see "Glossary of Terms."

General

Orbital Sciences Corporation, MacDonald, Dettwiler and Associates
Ltd.  and  3173623  Canada  Inc., a newly  formed  subsidiary  of
Orbital,  have entered into the Combination Agreement.   Pursuant
to  the  Combination Agreement, MDA and Acquisition have  applied
for  and  received  the  Interim Order of the  Supreme  Court  of
British  Columbia calling the Special Meeting of MDA Shareholders
and  MDA  1988  Optionholders to consider  the  approval  of  the
Arrangement under section 192 of the CBCA.

Pursuant  to  the  Arrangement, MDA will become  a  wholly  owned
subsidiary  of Acquisition and each outstanding MDA Common  Share
will  be  exchanged  for  a  number  of  Exchangeable  Shares  of
Acquisition equal to the Exchange Ratio.  The Exchange Ratio will
be determined by dividing US$5.41 by the average closing price of
Orbital Common Shares for the 20 trading days ending on the  date
four trading days prior to the Effective Date of the Arrangement,
provided that the Exchange Ratio will not be less than 0.2705  or
greater  than  0.3607.   Outstanding  MDA  Options  will   become
Replacement  Options to acquire Orbital Common  Shares  on  terms
identical   to   the  existing  MDA  Options,  with   appropriate
adjustments  in  the  exercise price and  the  number  of  shares
subject  to  such  options to reflect the  Exchange  Ratio.   The
Exchangeable  Shares will have voting, dividend  and  liquidation
rights  that are, as nearly as practicable, equivalent  to  those
rights of the Orbital Common Shares.

Orbital is a space technology company that designs, manufactures,
operates and markets a broad range of space products and services
that  include launch systems, space and electronics systems,  and
communications and information systems.  Orbital had revenues  of
approximately  US$222  million for the year  ended  December  31,
1994.   As  of June 30, 1995, Orbital's total backlog,  including
firm  orders  of approximately US$495 million, was  approximately
US$1.3  billion.   The closing sales price of an  Orbital  Common
Share on September 29, 1995 was US$16.25, as reported by NASDAQ.

The Arrangement and The Combination Agreement

The Combination Agreement, a copy of which is appended hereto  as
Appendix  "B," provides for the implementation of the Arrangement
under  the  CBCA, including obtaining the Interim Order,  calling
the  Special Meeting and obtaining the Final Order of  the  Court
approving  the  Arrangement.   The  Combination  Agreement   also
contains  the  terms  and  conditions  of  Orbital's,  MDA's  and
Acquisition's obligations to consummate the Arrangement.

The  Arrangement.   Pursuant  to the Arrangement,  (i)  MDA  will
become  a  wholly owned subsidiary of Acquisition and an indirect
subsidiary  of Orbital, (ii) MDA Shareholders (except  dissenting
holders,  and  except corporations ("Qualifying  Holdcos")  that,
together with their respective shareholders, have entered into an
agreement   (a  "Holding  Company  Agreement")  with  Acquisition
substantially  in  the  form attached as  Exhibit  2.1.2  to  the
Combination  Agreement  and have met  the  conditions  under  the
Holding  Company Agreement) will receive, in exchange  for  their
MDA  Common Shares, a number of Exchangeable Shares equal to  the
product of the number of such MDA Common Shares multiplied by the
Exchange  Ratio; (iii) all outstanding shares of each  Qualifying
Holdco  will  be  exchanged for a number of  Exchangeable  Shares
equal to the product of the number of MDA Common Shares owned  by
such  Qualifying  Holdco multiplied by the  Exchange  Ratio;  and
(iii)  each  outstanding  MDA Option will  be  converted  into  a
Replacement  Option exercisable for a number  of  Orbital  Common
Shares  equal  to the product of the number of MDA Common  Shares
subject  to such MDA Option multiplied by the Exchange Ratio,  at
an exercise price per share equal to the exercise price per share
of  such MDA Option divided by the Exchange Ratio, and subject to
the  same vesting, expiration and other terms as such MDA Option.
In  addition,  Acquisition will issue 10,000  Class  B  Preferred
Shares  to Canadian Imperial Bank of Commerce as partial  payment
for  investment  banking services rendered with  respect  to  the
Arrangement.  See "The Arrangement and the Combination  Agreement
- - Plan of Arrangement."

Recommendation and Fairness Opinion.  The MDA Board has  approved
the  Combination  Agreement and unanimously recommends  that  MDA
Shareholders  and  MDA  1988  Optionholders  vote  to  adopt  the
Arrangement Resolution.  Nesbitt Burns Inc., financial advisor to
MDA, has delivered to the MDA Board its written opinion dated  as
of  October  4, 1995 (a copy of which is attached to  this  Proxy
Circular  as  Appendix "C") to the effect that,  based  upon  and
subject  to the various considerations set forth in such  opinion
and  as of that date, the Arrangement is fair to MDA Shareholders
and  MDA 1988 Optionholders from a financial point of view.   The
fees to be paid to Nesbitt Burns are contingent upon consummation
of  the  Arrangement.  See "The Arrangement and  the  Combination
Agreement - MDA's Reasons for the Arrangement and Recommendations
of the MDA Board" and "- Opinion of MDA's Financial Advisor."

Qualifying Holdcos.  The Combination Agreement provides that  any
MDA  Shareholder that wishes to contribute its MDA Common  Shares
to  a  holding company and exchange the shares of the  Qualifying
Holdco  for  Exchangeable  Shares as  provided  in  the  Plan  of
Arrangement   may  do  so  by  complying  with   certain   notice
provisions,  entering  into  a  Holding  Company  Agreement   and
satisfying  the  conditions  set forth  in  the  Holding  Company
Agreement.  See "The Arrangement and the Combination Agreement  -
Qualifying Holdcos."

Description of Exchangeable Shares.  The Exchangeable Shares will
have  voting, dividend and liquidation rights that are, as nearly
as  practicable, equivalent to those rights of the Orbital Common
Shares, and will be exchangeable for Orbital Common Shares  on  a
one-for-one  basis  (subject to adjustment).   Each  Exchangeable
Share  will  be  entitled to receive dividends  from  Acquisition
payable  at the same time as, and to the extent possible  in  the
same  property or cash as, and in the case of cash dividends,  in
the  Canadian dollar equivalent of, each dividend paid by Orbital
on  an  Orbital Common Share.  The Exchangeable Shares  generally
will    not   be  entitled  to  vote  on  matters  submitted   to
Acquisition's  shareholders  but,  pursuant  to  the  Voting  and
Exchange Trust Agreement, holders of Exchangeable Shares will  be
provided with voting rights that will entitle them to vote  along
with  holders  of Orbital Common Shares on matters  submitted  to
Orbital's   shareholders.   In  the  event  of  the  liquidation,
dissolution or winding-up of Acquisition or Orbital, a holder  of
Exchangeable  Shares will receive one Orbital  Common  Share  for
each  Exchangeable  Share  (subject to adjustment).   Acquisition
will   automatically   redeem  all   Exchangeable   Shares   then
outstanding on the fifth anniversary of the Effective  Date,  and
may  redeem all outstanding Exchangeable Shares at any time  when
there are less than 400,000 outstanding Exchangeable Shares  held
by  persons other than Orbital and its Affiliates, in  each  case
for   a  redemption  price  of  one  Orbital  Common  Share   per
Exchangeable  Share  (subject to adjustment).   Upon  a  proposed
retraction  or  redemption of an Exchangeable Share,  or  in  the
event   of   the   liquidation,  dissolution  or  winding-up   of
Acquisition, Orbital will have the right, in lieu of  Acquisition
making  such  retraction, redemption or liquidation  payment,  to
purchase  Exchangeable Shares for a price of one  Orbital  Common
Share  for  each Exchangeable Share (subject to adjustment).   In
the  event  of  certain capital or corporate  reorganizations  of
Orbital,  the number of Orbital Common Shares to be  issued  upon
the   exchange  of  Exchangeable  Shares  will  be  appropriately
adjusted  so  that  the  holders of the Exchangeable  Shares  are
treated  in the same manner as holders of Orbital Common  Shares.
Although   the  transfer  of  Exchangeable  Shares,  subject   to
receiving certain orders from securities regulators, will not  be
restricted  under applicable securities laws, except  in  certain
stated  instances, the Exchangeable Shares will not be listed  on
any  stock  exchange and MDA does not expect there  will  be  any
market for the Exchangeable Shares.  See "The Arrangement and the
Combination Agreement - Description of Exchangeable Shares."

Voting  and  Exchange  Trust Agreement.  At the  Effective  Time,
Acquisition, Orbital and the Trustee will enter into  the  Voting
and Exchange Trust Agreement pursuant to which Orbital will issue
to  the  Trustee  one Series A Preferred Share  of  Orbital  (the
"Special Voting Share").  The Special Voting Share will vote with
the Orbital Common Shares at any meeting at which the holders  of
Orbital  Common Shares are entitled to vote, and will be entitled
to a number of votes equal to the number of Orbital Common Shares
issuable  upon  exchange of all Exchangeable  Shares  outstanding
from  time  to  time not owned by Orbital or its Affiliates.   On
each  vote  of  Orbital  Common Shares, holders  of  Exchangeable
Shares as of the record date established for the meeting at which
such vote will be taken will have the right to direct the Trustee
with  respect to a number of votes equal to the number of Orbital
Common  Shares  issuable  upon  exchange  of  their  Exchangeable
Shares.   See  "The Arrangement and the Combination  Agreement  -
Description of Exchangeable Shares - Voting Rights."

Pursuant to the Voting and Exchange Trust Agreement, Orbital will
grant  to  the  Trustee  for  the  benefit  of  the  holders   of
Exchangeable  Shares  the Exchange Right,  exercisable  upon  the
liquidation,  dissolution  or insolvency  of  Acquisition  or  if
Acquisition  defaults in its dividend, retraction  or  redemption
obligations with respect to the Exchangeable Shares,  to  require
Orbital to purchase all or any part of the Exchangeable Shares at
a   purchase  price  of  one  Orbital  Common  Share   for   each
Exchangeable Share (subject to adjustment).  In addition, Orbital
will  grant to the Trustee for the benefit of the holders of  the
Exchangeable  Shares  the Automatic Exchange  Right,  exercisable
upon  the  liquidation, dissolution or winding-up of Orbital,  to
automatically  exchange each Exchangeable Share for  one  Orbital
Common Share (subject to adjustment) five business days prior  to
the date of any such liquidation event.  See "The Arrangement and
the Combination Agreement - Description of Exchangeable Shares  -
Retraction, Redemption and Exchange Right."

Support  Agreement.   At  the  Effective  Time,  Acquisition  and
Orbital  will enter into the Support Agreement pursuant to  which
Orbital  will  covenant to take such action as  is  necessary  to
permit   Acquisition  to  (i)  pay  simultaneous  and  equivalent
dividends  on the Exchangeable Shares as are paid by  Orbital  on
the  Orbital  Common Shares, and (ii) honour the  redemption  and
retraction  rights  and  the dissolution  entitlements  that  are
attributes  of  the  Exchangeable Shares.  The Support  Agreement
will also provide that, without the prior approval of the holders
of  the  Exchangeable  Shares,  Orbital  will  not  take  certain
actions, such as declaring dividends on the Orbital Common Shares
or  effecting reclassifications or reorganizations of the Orbital
Common  Shares,  without  the same or an economically  equivalent
action  being taken in respect of the Exchangeable  Shares.   See
"The   Arrangement  and  the  Combination  Agreement  -   Support
Agreement."

Court   Approval   and  Completion  of  the   Arrangement.    The
implementation of the Arrangement is subject to the  Final  Order
approving  the Arrangement.  MDA, Acquisition and Orbital  intend
to apply for the Final Order as promptly as practicable after the
Special  Meeting.   A copy of the Notice of Application  for  the
Final  Order is attached as Appendix "E" hereto.  The hearing  in
respect  of  the  Final  Order  is scheduled  to  take  place  on
November  16,  1995  before  the presiding  Judge  or  Master  in
Chambers at the Courthouse, 800 Smithe Street, Vancouver, British
Columbia.   At  that hearing, any MDA Shareholder, any  MDA  1988
Optionholder  and  any  other  interested  party  who  wishes  to
participate  or  to  be  represented or to  present  evidence  or
argument may do so, subject to filing with the Court and  serving
appropriate  notices of appearance in accordance with the Interim
Order.   At  the  hearing  for the Final Order,  the  Court  will
consider,  among  other factors, the fairness of the  Arrangement
and   the   approval  of  the  Arrangement  Resolution   by   MDA
Shareholders and MDA 1988 Optionholders.  The Effective  Date  of
the  Arrangement will occur after the Final Order is obtained and
all  other  conditions  in the Combination  Agreement  have  been
satisfied  or  waived, which is expected to occur promptly  after
the  Special  Meeting.  See "The Arrangement and the  Combination
Agreement - Court Approval and Completion of the Arrangement."

Conditions  to the Arrangement.  Consummation of the  Arrangement
is  subject  to  the  satisfaction of  a  number  of  conditions,
including  but not limited to: (i) the passage of the Arrangement
Resolution   by   the  MDA  Shareholders   and   the   MDA   1988
Optionholders;  (ii) Dissenting MDA Shareholders  and  Dissenting
MDA 1988 Optionholders being entitled in the aggregate to receive
no more than 10% of the aggregate number of Orbital Common Shares
and  Replacement Options to be issued pursuant  to  the  Plan  of
Arrangement;   (iii)   the  receipt  of   necessary   orders   or
registrations under applicable securities regulations  to  permit
the  transactions contemplated by the Arrangement to be completed
and  the  Exchangeable Shares to be freely  tradeable  except  in
certain   limited  circumstances;  (iv)  the   absence   of   any
restrictive court orders or any other legal restraints preventing
or  making illegal the consummation of the Arrangement;  (v)  the
continuing   accuracy   in   all   material   respects   of   the
representations  and  warranties  made  by  each   of   MDA   and
Acquisition and Orbital in the Combination Agreement on and as of
the Effective Date; and (vi) the receipt by Orbital of an opinion
that  the  Arrangement is to be accounted for  as  a  pooling  of
interests.  See "The Arrangement and the Combination Agreement  -
The Combination Agreement."

Termination.  The Combination Agreement may be terminated and the
Arrangement  may  be  abandoned  prior  to  the  Effective  Date,
notwithstanding the approval by the MDA Shareholders and the  MDA
1988  Optionholders  of  the Arrangement  Resolution,  under  the
circumstances specified in the Combination Agreement,  including:
(i)  by  Orbital,  if  the Average Closing  Price  is  more  than
US$25.00;  (ii) by Orbital, if the MDA Board shall have withdrawn
or  modified in any manner adverse to Orbital its support of  the
Arrangement,  or  shall  fail to affirm  such  support  upon  the
request of Orbital; (iii) by MDA, if the Average Closing Price is
less  than  US$12.775; (iv) by MDA, if MDA receives a  bona  fide
offer  to  acquire  all  the  shares  or  assets  of  MDA  for  a
consideration  per  MDA Common Share having a fair  market  value
greater than US$5.95, based on prevailing exchange rates  at  the
date  of  the offer; (v) by mutual agreement of Orbital and  MDA;
and (vi) by either party if the Arrangement is not consummated by
December  31,  1995 (other than as a result of a default  of  the
terminating  party).   Under certain  circumstances  MDA  may  be
required  to  pay  Orbital a US$750,000 termination  fee  if  the
Combination  Agreement is terminated by MDA. See "The Arrangement
and  the  Combination  Agreement - The  Combination  Agreement  -
Termination  and  Amendment"  and "-  Solicitation  of  Alternate
Transactions."

Operations Following the Arrangement.  Orbital currently  expects
that following the Arrangement, MDA will continue to operate as a
separate  entity,  substantially in the same  manner  as  it  has
operated  its  business  prior  to  the  Arrangement.   See  "The
Arrangement and the Combination Agreement - Operations  Following
the Arrangement."

Accounting  Treatment.   The  Arrangement  is  expected   to   be
accounted for as a pooling of interests under U.S. GAAP,  and  it
is   a  condition  to  Orbital's  obligation  to  consummate  the
Arrangement that Orbital shall have received an opinion  of  KPMG
Peat  Marwick LLP, its independent auditors, to the  effect  that
such  accounting treatment is appropriate.  See "The  Arrangement
and the Combination Agreement - Accounting Treatment."

Certain Canadian Federal Income Tax Considerations

The   following  discussion  of  Canadian  federal   income   tax
considerations  is  intended as a general summary  and  does  not
discuss  all of the facts and circumstances that may  affect  the
tax  liability of particular holders of MDA Common Shares and MDA
1988  Options.  Holders of MDA Common Shares and MDA 1988 Options
are  urged  to consult their own tax advisors.  See  "Income  Tax
Considerations to MDA Shareholders and Optionholders  -  Canadian
Federal Income Tax Considerations."

Residents of Canada.  A holder of MDA Common Shares who  receives
Exchangeable  Shares  will generally not be subject  to  Canadian
income  tax in respect of such transaction (i) if such holder  is
not considered to receive Voting Rights or the Exchange Right for
MDA  Common Shares, or (ii) even if such holder is considered  to
receive  Voting  Rights  or the Exchange  Right  for  MDA  Common
Shares, if such holder effects a Tax Election under section 85 of
the  Canadian  Tax Act specifying a transfer price equal  to  the
aggregate  of  the adjusted cost bases of such MDA Common  Shares
immediately before the exchange.

Pursuant to the Canadian Tax Act, a holder of an outstanding  MDA
1988 Option that becomes a Replacement Option will be deemed  not
to  have disposed of the MDA 1988 Option and not to have acquired
the  Replacement  Option, provided the value of  the  Replacement
Option  is  not  greater than the value of the MDA  1988  Option.
Furthermore,  for  purposes  of  the  tax  consequences  of   the
Replacement Option, the Replacement Option will be deemed  to  be
the  same  option as, and a continuation of, the MDA 1988  Option
and  Orbital will be deemed to be the same corporation as, and  a
continuation of, MDA.

So  long as the value of the Call Rights, Exchange Right and  the
Voting Rights is nominal, the grant of Call Rights by a holder of
Exchangeable Shares, in consideration of the receipt of  Exchange
Right  and  Voting  Rights, should not  result  in  any  material
Canadian federal income tax consequences.

A  holder  of  Exchangeable Shares who  receives  Orbital  Common
Shares  from Acquisition on a redemption (including a retraction)
by Acquisition of the holder's Exchangeable Shares will be deemed
to  receive a dividend as a result of such redemption.  A  holder
of Exchangeable Shares who exchanges his Exchangeable Shares with
Orbital  for Orbital Common Shares upon the exercise of the  Call
Rights  or  the Exchange Right will generally realize  a  capital
gain (or capital loss) as a result of such exchange.

Non-Residents  of  Canada.  Provided the MDA  Common  Shares  are
listed   on   a  prescribed  stock  exchange  at  the   time   of
implementation of the Arrangement, a holder of MDA Common  Shares
who  is  not resident in Canada, who holds MDA Common  Shares  as
capital  property  and  does  not  hold  MDA  Common  Shares   in
connection  with a business carried on in Canada, generally  will
not  be  subject to tax under the Canadian Tax Act  solely  as  a
result of the transactions effected pursuant to the Arrangement.

A non-resident holder of Exchangeable Shares who receives Orbital
Common  Shares  from  Acquisition on a  redemption  (including  a
retraction) of the holder's Exchangeable Shares will be deemed to
receive  a dividend as a result of such redemption that  will  be
subject  to  non-resident withholding tax under the Canadian  Tax
Act at the rate of 25%, subject to reduction under the provisions
of  an  applicable  income tax treaty.  Under  the  Canada-United
States  Income Tax Convention, the rate is generally  reduced  to
15% for residents of the United States.  A holder of Exchangeable
Shares  who  exchanges his Exchangeable Shares with  Orbital  for
Orbital Common Shares upon the exercise of the Call Rights or the
Exchange Right will generally realize a capital gain (or  capital
loss) as a result of such exchange.

An exchange of Exchangeable Shares for Orbital Common Shares by a
non-resident may be subject to tax under the Canadian Tax Act.  A
non-resident may be exempt from tax pursuant to the provisions of
an  applicable tax treaty such as the Canada-United States Income
Tax Convention.  In any case, Orbital or Acquisition will require
non-residents to obtain a certificate from Revenue Canada on such
exchange  specifying a certificate limit not less than  the  fair
market   value  of  the  Orbital  Common  Shares.   If  no   such
certificate is obtained, then either Orbital or Acquisition  will
withhold and remit to Revenue Canada as tax on behalf of such non-
resident  holder, 33J% of the fair market value  of  the  Orbital
Common Shares, and Orbital or Acquisition will deliver to the non-
resident  holder  a reduced number of Orbital  Common  Shares  to
reflect such payment to Revenue Canada.

Certain United States Federal Income Tax Considerations

The  following  discussion of United States  federal  income  tax
considerations  is  intended as a general summary  and  does  not
discuss  all of the facts and circumstances that may  affect  the
tax  liability of particular MDA Shareholders.  MDA  Shareholders
are  urged  to consult their own tax advisors.  See  "Income  Tax
Considerations  to  MDA Shareholders and Optionholders  -  United
States Federal Income Tax Considerations."

U.S.  Shareholders.  MDA and Orbital believe, based on advice  of
counsel,  that there is a reasonable basis on which  to  conclude
that   the  exchange  of  MDA  Common  Shares  pursuant  to   the
Arrangement  will  constitute  a  taxable  transaction  for  U.S.
federal  income  tax purposes, and MDA understands  that  Orbital
intends  to report the exchange in a manner consistent  with  the
foregoing.  If the exchange is taxable, MDA Shareholders who  are
"United  States  persons" for U.S. federal  income  tax  purposes
("U.S.  Holders"), including United States citizens or residents,
domestic  corporations,  domestic partnerships,  and  estates  or
trusts  subject  to  U.S.  federal income  tax  on  their  income
regardless  of  source,  who  receive Exchangeable  Shares  would
recognize  capital  gain  or  loss in  an  amount  equal  to  the
difference  between  the fair market value  of  the  Exchangeable
Shares   received  (together  with  cash  received  in  lieu   of
fractional  shares (if any)) and the tax basis of the MDA  Common
Shares  surrendered in the exchange.  Such capital gain  or  loss
would  generally constitute U.S. source gain and would  be  long-
term capital gain or loss if the MDA Common Shares exchanged have
been held for more than one year at the time of the exchange.  It
is  possible,  however, that the United States  Internal  Revenue
Service  (the  "IRS") may take the position that the  receipt  of
Exchangeable Shares in exchange for MDA Common Shares  is  not  a
taxable  event, in which case a U.S. Holder would  only  have  to
recognize gain to the extent of cash in lieu of fractional shares
(if  any),  and  certain carryover tax basis and  holding  period
rules would apply to the Exchangeable Shares.

MDA  and  Orbital also believe, based on the advice  of  counsel,
that  there is a reasonable basis on which to conclude  that  the
exchange, retraction or redemption of the Exchangeable Shares for
Orbital Common Shares will be treated as a taxable event for U.S.
federal income tax purposes, and Orbital has advised MDA that  it
currently  intends to take this position.  If the exchange  is  a
taxable event, a U.S. Holder that receives Orbital Common  Shares
from   Orbital  pursuant  to  the  Call  Rights  would  generally
recognize  capital  gain or loss equal to the difference  between
the fair market value of the Orbital Common Shares at the time of
the exchange (together with cash in lieu of fractional shares (if
any) and cash equal to the Dividend Amount (if any)) and the  tax
basis  of  the  Exchangeable Shares.  Such capital gain  or  loss
would  be  long-term  capital gain or loss  if  the  Exchangeable
Shares  have been held for more than one year at the time of  the
exchange.   It  is possible, however, that the IRS  could  assert
that  a  portion  of such gain constitutes U.S.  source  ordinary
income.   If  the  receipt of Orbital Common Shares  is  effected
through  a  retraction  or  redemption  of  Exchangeable   Shares
distributed to a U.S. Holder directly by Acquisition, then if the
retraction or redemption is treated as a taxable transaction,  it
would be treated as a taxable exchange of the Exchangeable Shares
if  the U.S. Holder meets certain tests relating to reductions in
its  percentage shareholdings in Acquisition, and otherwise would
be  taxed  as a dividend paid on the Exchangeable Shares  to  the
extent  of  Acquisition's (or, possibly, Orbital's) earnings  and
profits.  It is possible, however, that the IRS could assert that
the exchange, retraction or redemption of Exchangeable Shares for
Orbital  Common Shares is not a taxable event, in  which  case  a
U.S.  Holder would only have to recognize gain to the  extent  of
cash  in  lieu  of  fractional shares (if any) and  the  Dividend
Amount  (if  any),  and certain carryover tax basis  and  holding
period rules would apply to the Orbital Common Shares.

Non-U.S. Shareholders.  A holder of MDA Common Shares that is not
a  U.S.  Holder ("non-U.S. Holder") generally will not be subject
to U.S. federal income tax on a gain recognized on the receipt of
the Exchangeable Shares, Voting Rights and Exchange Right, or  on
the  subsequent  sale or exchange of the Exchangeable  Shares  or
Orbital  Common Shares, unless such gain is effectively connected
with a U.S. trade or business.

Dividends  received  by a non-U.S. Holder  with  respect  to  the
Orbital   Common  Shares  generally  will  be  subject  to   U.S.
withholding  tax at a rate of 30%, which rate may be  subject  to
reduction  by  an applicable income tax treaty in effect  between
the  U.S. and the non-U.S. Holder's country of residence.   Under
the  Canada-U.S.  Income Tax Convention, the  rate  is  generally
reduced  to 15%.  Although the matter is not entirely  free  from
doubt,  dividends received by a non-U.S. Holder  on  Exchangeable
Shares should not be subject to U.S. withholding tax.

The Special Meeting

Time  and  Place.  The Special Meeting will be held  on  Tuesday,
November 14, 1995 at the office of MDA at 13800 Commerce Parkway,
Richmond, B.C., V6V 2J3, at 10:00 a.m. (Vancouver time).

MDA Shareholders and MDA 1988 Optionholders Entitled to Vote.  At
the Special Meeting, the MDA Shareholders (voting together as one
class) and the MDA 1988 Optionholders (voting separately from the
MDA  Shareholders as a second class) will each consider and  vote
upon  a proposal to approve the Arrangement Resolution, and  will
transact  such  other business as may properly  come  before  the
Special  Meeting  or  any adjournments  thereof.   The  close  of
business on October 10, 1995 is the record date for determination
of  MDA Shareholders entitled to receive notice of and to vote at
the Special Meeting, subject to the rights of certain transferees
of MDA Common Shares after that date in accordance with the CBCA.
All  holders  of  MDA  1988 Options on the date  of  the  Special
Meeting  will  be  entitled to attend and  vote  at  the  Special
Meeting.  As of September 29, 1995, 11,218,156 MDA Common  Shares
and  277,643 MDA 1988 Options were outstanding.  See "The Special
Meeting -General Proxy Information."

Vote  Required.  Subject to any further order of the  Court,  the
Arrangement  Resolution must be approved by the affirmative  vote
of   66K%  of  the  votes  actually  cast  thereon  by  the   MDA
Shareholders and the MDA 1988 Optionholders, voting  as  separate
classes (and for this purpose any spoiled votes, illegible votes,
defective  votes and abstentions shall be considered  not  to  be
votes cast).  Directors, officers and shareholders of MDA holding
approximately  56.6%  of  the issued and outstanding  MDA  Common
Shares  have  executed Voting Agreements and Irrevocable  Proxies
with  Orbital agreeing to vote for the Arrangement Resolution  at
the Special Meeting.  In addition, certain officers and employees
of  MDA holding approximately 59.2% of total votes entitled to be
cast  by the MDA 1988 Optionholders have agreed with MDA to vote,
as  MDA 1988 Optionholders, for the Arrangement Resolution.   See
"The Special Meeting - General Proxy Information - Required Votes
to  Approve  the  Arrangement and Voting  Intentions  of  Certain
Shareholders and Optionholders."

Dissent Rights.  MDA Shareholders and MDA 1988 Optionholders  who
do  not vote in favour the Arrangement Resolution and comply with
certain procedures are entitled to dissent under section  190  of
the  CBCA, in accordance with the Interim Order.  See "Dissenting
Rights."

Business of Orbital

Orbital is a space technology company that designs, manufactures,
operates and markets a broad range of space products and services
that are grouped into three categories: Launch Systems, Space and
Electronics Systems, and Communications and Information  Systems.
Launch  Systems  include  space and suborbital  launch  vehicles;
Space  and  Electronics  Systems include  satellites,  spacecraft
platforms, space sensors and instruments, and space payloads  and
experiments,  as  well as advanced avionics and  data  management
systems;  and  Communications  and  Information  Systems  include
satellite-based  two-way  mobile  data  communications   systems,
satellite-based  navigation products and remote sensing  systems,
along   with   satellite  tracking  systems   and   environmental
monitoring products.  See "Information Concerning Orbital."

Orbital's  goal  is  to become a full-service  space  company  by
integrating  its launch vehicles, satellites and  other  products
into  complete "turn-key" space systems and providing  end-to-end
satellite-based  services  for  particular  markets.    Orbital's
strategy  is  to  exploit  expanding  opportunities  to   provide
government,  commercial and other customers with low-cost  access
to  space.   Essential  elements of  Orbital's  strategy  include
investment  of substantial private capital in the development  of
proprietary products; reduction of the time required for  product
development; formation of strategic business alliances to enhance
Orbital's   marketing,  technical,  manufacturing  and  financial
capabilities;    establishment    of    vertically     integrated
manufacturing  and  testing  capabilities;  and  acquisitions  of
companies with product lines that complement or enhance Orbital's
existing  base  of products, services and technologies.   Orbital
believes  that  providing  lower-cost  "turn-key"  space  systems
should  stimulate  the  use  of space products  and  services  by
private  corporations, educational and research institutions  and
other  non-traditional  space  customers  including,  ultimately,
individual consumers.

Orbital's   customer  base  includes  a  wide   range   of   U.S.
governmental  agencies,  universities and commercial  enterprises
including: the U.S. National Aeronautics and Space Administration
("NASA");  the  National Oceanic and Atmospheric  Administration;
various  organizations  within the  U.S.  Department  of  Defense
("DoD"),  including the U.S. Army, the U.S. Navy,  the  U.S.  Air
Force,  the  Advanced Research Projects Agency ("ARPA")  and  the
Ballistic Missile Defense Organization ("BMDO"); ORBCOMM  Global,
L.P.  ("ORBCOMM Global"), an affiliate of Orbital; Johns  Hopkins
University;   and   certain  distributors  of   electronics   and
recreational equipment.

Launch   Systems.    Orbital's  Launch   Systems   Group's   most
significant products are space and suborbital launch vehicles.  A
space  launch vehicle launches a satellite into orbit around  the
Earth.   Suborbital launch vehicles place payloads into a variety
of  high-altitude trajectories but, unlike space launch vehicles,
do not place payloads into Earth orbit.

Orbital's space launch vehicles are the Pegasusr launch  vehicle;
the  Pegasus XL launch vehicle (a modified, larger version of the
Pegasus);  and  the  Taurusr launch  vehicle.   The  Pegasus  and
Pegasus  XL  vehicles are launched from beneath a modified  large
aircraft  such as a Lockheed L-1011 to deploy satellites weighing
up  to  1,000  pounds into low-Earth orbit.  The  higher-capacity
Taurus  vehicle  is a ground-launched derivative of  the  Pegasus
vehicle  that can carry payloads weighing up to 3,000  pounds  to
low-Earth  orbit  and  payloads weighing  up  to  800  pounds  to
geosynchronous  orbit.   In  March  1995,  Orbital  and  Rockwell
International  Corporation agreed to  form  a  joint  venture  to
develop,  construct, operate and market a new advanced technology
small reusable space launch vehicle (the "X-34").

Orbital's  suborbital launch products include  various  types  of
suborbital  vehicles  and  their principal  subsystems,  payloads
carried   by   such   vehicles,  and   related   launch   support
installations  and systems used in their assembly and  operation.
Customers  typically use Orbital's suborbital launch vehicles  to
launch  scientific  and  other payloads and  for  defence-related
applications such as target and interceptor experiments for anti-
missile defence systems.

Space  and  Electronics Systems.  Orbital's Space and Electronics
Systems Group's products include spacecraft systems and payloads,
defence avionics and sensors.

The  Space and Electronics Systems Group is responsible  for  the
design,  production  and  testing  of  small  and  medium   class
spacecraft  for scientific, military and commercial applications.
The  small  standard spacecraft platforms developed  by  Orbital,
such  as  the  PegaStarO and the MicroStarO, are designed  to  be
launched  by  the Pegasus, Pegasus XL or Taurus launch  vehicles.
The  PegaStar spacecraft platform is a general purpose spacecraft
that has successfully performed on one mission, and is planned to
be  used  for  Orbital's SeaStarO ocean environmental  monitoring
satellite  system.   Orbital's MicroStar spacecraft  platform  is
designed  for  use in the ORBCOMM Global satellite-based  two-way
data  communications network consisting of  up  to  36  MicroStar
satellites (the "ORBCOMM System") and also for a variety of small
space  science  and  remote sensing projects, including  some  of
those being pursued by Orbital's wholly owned subsidiary, Orbital
Imaging   Corporation  ("ORBIMAGE").   Orbital's   medium   class
satellites are generally used to gather various scientific  data,
such  as  ocean  topography and ultraviolet sources  outside  the
galaxy.

Orbital  develops,  manufactures and markets  avionics  products,
including  advanced electronics and data management  systems  for
aircraft  flight  operations  and ground  support  for  the  U.S.
military  and  foreign  governments.  The Space  and  Electronics
Systems Group also is responsible for the design, production  and
testing of spacecraft command and data handling, attitude control
and  structural  subsystems  for  a  variety  of  government  and
commercial customers.  Other Space and Electronics Systems  Group
products   include   satellite-borne   scientific   sensors   and
instruments, such as atmospheric ozone monitoring instruments and
environmental sensors.

Communications and Information Systems.  Orbital's Communications
and  Information  Systems Group includes Orbital's  subsidiaries:
Orbital  Communications  Corporation  ("ORBCOMM"),  ORBIMAGE  and
Magellan Corporation ("Magellan").

In  June  1993, ORBCOMM and Teleglobe Mobile Partners ("Teleglobe
Mobile"),  a  partnership formed by Teleglobe Inc. ("Teleglobe"),
formed  ORBCOMM Global to design, develop, construct,  integrate,
test  and  market the ORBCOMM System.  The ORBCOMM  System  is  a
satellite-based  communications  network  designed   to   provide
virtually  continuous  mobile data communications  coverage  over
much  of the Earth's surface.  The ORBCOMM System will include  a
constellation  of  up  to  36  small  low-Earth  orbit  MicroStar
satellites,  a satellite control centre operating and positioning
the  satellites, network control centres controlling the flow  of
information through the system, local ground stations sending and
receiving signals between the network control centres and  nearby
satellites,  and the mobile communicators used by subscribers  to
transmit and receive messages to and from nearby satellites.   In
April  1995,  Orbital launched on a Pegasus  launch  vehicle  the
first  two  satellites  of the ORBCOMM  System.   ORBCOMM  Global
expects  to  begin  intermittent commercial service  using  these
satellites during the first quarter of 1996.

ORBIMAGE is currently seeking to develop and market a broad range
of   information  services  that  identify  and  monitor   global
environmental  changes and collect and disseminate  other  remote
sensing  information.  Small Earth-viewing satellites and related
sensors and instruments to be placed in relatively low orbits are
expected  to  offer cost-efficient data collection, daily  global
coverage  and high-resolution sensing services.  Services  to  be
provided  by  ORBIMAGE  could  include  high-resolution   optical
imaging  of land surfaces for geographic information and  sensing
of ozone and atmospheric conditions.

Magellan  designs,  manufactures and markets  Global  Positioning
System  satellite-based navigation and positioning  products  for
commercial  and  consumer markets including marine  and  aviation
applications,  outdoor recreational users  such  as  hunters  and
hikers,  professional  users  such  as  geologists,  geographers,
surveyors, natural resource managers and contractors  and,  to  a
lesser extent, governmental users.

Business of MDA

MDA  provides  technology-based solutions and services  to  Earth
information,  air  navigation,  defence  applications  and   data
communications markets worldwide, through four business areas.

Geo-Information Systems.  Geo-Information Systems, MDA's  largest
business  area,  involves  the development  of  systems  for  the
management  of Earth resources and the environment,  by  applying
MDA's  expertise in Earth observation ground stations and related
markets.   MDA  is  one  of  the  world's  leading  companies  in
providing  solutions  for the acquisition, processing,  archiving
and  dissemination of non-classified Earth observation data.   Of
the 26 non-secret ground stations in the world,  MDA has built or
been  part  of  the  construction of 23  ground  stations  in  20
countries.   In addition to pursuing opportunities to  build  new
ground  stations,  MDA  is  actively  pursuing  opportunities  to
upgrade existing ground stations so that they are able to process
the  data  that  new  technologically-advanced Earth  observation
satellites are able to provide.

In  addition  to  systems for space-based Earth observation,  MDA
builds systems to process Earth images from airborne radar.   MDA
also   designs  and  builds  customized  software   products   in
consultation  with consumers in government and industry  to  make
geographic related data more useful.  The Geo-Information Systems
business  area provides operational and post-delivery support  to
ensure  operational  efficiency  of  systems  delivered  to   its
customers.  This support includes consulting services,  training,
maintenance and test equipment, spare parts and manuals.

Aviation  Systems.   MDA's  Aviation  Systems  business  area  is
focused on specific markets, including the provision of automated
aeronautical  information  systems  and  automated  air   traffic
management  systems.   MDA builds and markets  the  Pegasus-AISTM
(unrelated  to  Orbital's  Pegasus  space  launch  vehicle),   an
automated  aeronautical  information  management  system.    This
system  provides  pilots and other users  with  aeronautical  and
meteorological  information.  In addition, MDA  is  developing  a
niche  in  the embedding of its aeronautical information  systems
into broader air traffic management systems.

MDA is currently participating in the development and delivery of
air  traffic  management  software to be  used  in  the  Canadian
Automated  Air  Traffic System.  Air traffic  management  systems
allow  air  traffic  controllers to guide  pilots  in  flight  by
combining    information   about   flights,   routes,    weather,
navigational aids, airways and airports, and delivering it to air
traffic  controllers in a form that is intended to enable timely,
safe decisions.

Space  and  Defence  Systems.  MDA's Space  and  Defence  Systems
business  area provides surveillance and command support  systems
for  space and defence.  MDA's defence systems include naval mine
countermeasures, artillery command and control,  radar  deception
systems and military materiel management.  In space-related work,
MDA  continues to provide major software development  efforts  as
part of Canada's contribution to the Space Station project.  This
activity  provides  an opportunity for the enhancement  of  MDA's
space-qualified software capabilities.

Communications.   In  1994, MDA entered a  new  computer  network
communications  consulting  and  training  business  through  the
acquisition  of  Ottawa-based The PSC Communications  Group  Inc.
PSC  helps  customers  design  and  implement  networks  so  that
computers can communicate faster and at lower cost, and  develops
software  for special client needs, such as to monitor  networks,
and   find   and   correct  trouble-spots.    PSC   also   offers
instructional classes for a variety of vendor products,  as  well
as  general courses in computer communications, aimed  mainly  at
technicians in companies across North America, Europe  and  other
parts of the world.
              MARKET PRICE AND DIVIDEND INFORMATION

Orbital  Common  Shares  are quoted on NASDAQ  under  the  symbol
"ORBI".   The following table sets forth the high and low closing
sale  prices reported on NASDAQ for an Orbital Common  Share  for
the  periods  indicated.  The closing sale price  of  an  Orbital
Common Share on the NASDAQ on July 28, 1995, the last trading day
prior  to  the  public  announcement  of  the  Arrangement,   was
US$17.625  and  on  September 29, 1995,  the  latest  practicable
trading  day  before  the printing of this  Proxy  Circular,  was
US$16.25.

Twelve Month Periods          High       Low
Ended December 31,             US$       US$

1993
First Quarter                   14.25      10.75
Second Quarter                  13.75      10.25
Third Quarter                   19.00      12.25
Fourth Quarter                  23.00      16.50

1994                                            
First Quarter                   26.50      15.25
Second Quarter                  24.50      14.00
Third Quarter                   18.50      14.50
Fourth Quarter                  22.50      15.00

1995                                            
First Quarter                   20.50      16.50
Second Quarter                  22.00      15.50
Third Quarter                   19.25      16.25

MDA  Common  Shares have been traded on the VSE since  August  9,
1993  and on the TSE since April 3, 1995 under the symbol  "MDA".
The  following  table sets forth the high and  low  closing  sale
prices  reported on the VSE and TSE for an MDA Common  Share  for
the  periods indicated.  The closing sale price for an MDA Common
Share on the TSE on July 28, 1995, the last trading day prior  to
the  public announcement of the Arrangement, was Cdn$5.50 and  on
September 29, 1995, the latest practicable trading day before the
printing   of  this  Proxy  Circular,  was  Cdn$6.375.   Assuming
Effective  Dates  of July 28, 1995 and September  29,  1995,  the
Exchange Ratio would have been .2927 and .3133, respectively.
<TABLE>
<CAPTION>
                                    VSE              TSE

Twelve Month Periods Ended       High    Low    High     Low
December 31,                     
                                 Cdn$     Cdn$    Cdn$    Cdn$
<S>                             <C>      <C>    <C>     <C>

1993                                                    
August 9 to Sept. 30              4.50    3.80   ---     ---

Fourth Quarter                    4.10    3.00   ---     ---

1994                                                     ---

First Quarter                     4.15    3.20   ---

Second Quarter                    4.00    3.50   ---     ---

Third Quarter                     4.25    3.65   ---     ---

Fourth Quarter                    4.00    3.25   ---     ---

1995

First Quarter                     3.75    2.90   ---     ---

Second Quarter                    3.75    3.50  4.55(1)  3.30 (1)

Third Quarter                     6.625   6.625  7.125   4.05

</TABLE>

Note 1: Commencing April 3, 1995.


Neither  Orbital nor MDA has paid any dividends on  their  common
shares  except for a cash dividend of $1.00 per MDA Common  Share
paid  by  MDA  in  1992.   Orbital currently  intends  to  retain
earnings  for use in its business and does not anticipate  paying
cash  dividends  on the Orbital Common Shares in the  foreseeable
future.   In  addition, Orbital is subject to certain contractual
restrictions  on  its ability to pay dividends.  The  Combination
Agreement prohibits the payment of any dividends by MDA prior  to
the Effective Date.

         SELECTED HISTORICAL CONSOLIDATED FINANCIAL DATA

The  following selected historical financial information  of  MDA
and  Orbital  has  been derived from their respective  historical
consolidated  financial  statements,  and  should  be   read   in
conjunction with such consolidated financial statements  and  the
related  notes  thereto,  which are attached  as  Annex  "I"  for
Orbital and Annex "II" for MDA to this Proxy Circular.

Selected Historical Consolidated Financial Data of MDA

The  following selected consolidated financial data as of and for
the  fiscal years ended March 31, 1993, 1994 and 1995 of MDA  are
derived  from  the  consolidated  financial  statements  of  MDA,
including  those contained in Annex "II" to this Proxy  Circular,
and   should  be  read  in  conjunction  with  such  consolidated
financial   statements  and  the  related  notes  thereto.    The
following  selected  consolidated financial data  for  the  three
months  ended June 30, 1994 and 1995 and as of June 30, 1995  are
derived  from  the  unaudited consolidated  financial  statements
included in Annex "II" to this Proxy Circular.  In the opinion of
management  of  MDA,  the unaudited consolidated  financial  data
reflect all adjustments, consisting of normal recurring accruals,
necessary  for  a fair presentation.  The operating  results  for
interim  periods are not necessarily indicative  of  the  results
expected for the full year.

Omitted:  See the Consolidated Financial Data of MDA included
in Item 7(a) above.

Selected Historical Consolidated Financial Data of Orbital

The  following selected consolidated financial data as of and for
the  years ended December 31, 1992, 1993 and 1994 of Orbital  are
derived  from  consolidated  financial  statements  contained  in
Annex  "I"  to  this  Proxy  Circular,  and  should  be  read  in
conjunction with such consolidated financial statements  and  the
related  notes  thereto.   The  following  selected  consolidated
financial  data for the six months ended June 30, 1994  and  1995
and  as  of  June  30, 1995 are derived from unaudited  condensed
consolidated financial statements included in Annex "I"  to  this
Proxy  Circular.   In the opinion of management of  Orbital,  the
unaudited  consolidated financial data reflect  all  adjustments,
consisting  of normal recurring accruals, necessary  for  a  fair
presentation.  The operating results for interim periods are  not
necessarily indicative of the results expected for the full year.

Omitted:  See the Selected Historical Consolidated Financial Data
of Orbital included in the Company's Annual Report on Form 10-K
filed with the SEC on March 29, 1995.

                PRO FORMA FINANCIAL INFORMATION

For purposes of the following pro forma presentation, Orbital has
assumed  that  the conversion of the Exchangeable  Shares  occurs
contemporaneously with the other transactions  occurring  on  the
Effective  Date (i.e., that Orbital issues Orbital Common  Shares
directly  for MDA Common Shares).  The actual number  of  Orbital
Common  Shares issuable pursuant to the Combination Agreement  is
based  on the Average Closing Price.  Assuming an Average Closing
Price  of US$17.25 per Orbital Common Share and an Exchange Ratio
of  .3136 Orbital Common Shares to 1.00 MDA Common Share, Orbital
expects to issue approximately 3.9 million Orbital Common  Shares
for  all  issued and outstanding MDA Common Shares and under  all
Replacement  Options  for MDA Options.  The Arrangement  will  be
accounted for using the pooling of interests method of accounting
and,  accordingly, MDA's assets and liabilities will  be  carried
forward at their historical recorded amounts.

The   following   unaudited  pro  forma  condensed   consolidated
financial  information  consists  of  the  Unaudited  Pro   Forma
Condensed  Consolidated  Statements of  Operations  for  the  six
months  ended  June 30, 1995 and for the year ended December  31,
1994,  and the Unaudited Pro Forma Condensed Consolidated Balance
Sheet   as  of  June  30,  1995  (collectively,  the  "Pro  Forma
Statements").   The  Unaudited Pro Forma  Condensed  Consolidated
Statement  of Operations for the six months ended June  30,  1995
gives  effect  to  the  Arrangement as  if  it  had  occurred  on
January  1, 1995.  The Unaudited Pro Forma Condensed Consolidated
Statement  of  Operations for the year ended  December  31,  1994
gives  effect  to  the  Arrangement as  if  it  had  occurred  on
January  1, 1994.  The Unaudited Pro Forma Condensed Consolidated
Balance  Sheet  gives  effect to the Arrangement  as  if  it  had
occurred  on June 30, 1995.  The Pro Forma Statements  have  been
prepared in accordance with U.S. GAAP (see Notes 2 and G  to  the
Pro  Forma  Statements  for a description  of  major  differences
between U.S. GAAP and Canadian GAAP).

Orbital's  management  believes that,  on  the  basis  set  forth
herein, the Pro Forma Statements reflect a reasonable estimate of
the  Arrangement based on currently available information and the
assumptions  described herein.  The pro forma financial  data  do
not  purport  to represent what Orbital's financial  position  or
results   of  operations  would  actually  have  been   had   the
Arrangement in fact occurred on June 30, 1995, January 1, 1995 or
January  1,  1994, or to project Orbital's financial position  or
results  of  operations for any future date or period  indicated.
The  Pro Forma Statements should be read in conjunction with  the
consolidated financial statements of each of Orbital and MDA  and
related   notes  thereto  included  in  Annexes  "I"  and   "II,"
respectively.

OMITTED:  See the Unaudited Pro Forma Condensed Cconsolidated Balance
Sheet at June 30, 1995 filed above in Item 7(b).

OMITTED:  See the Unaudited Pro Forma Condensed Consolidated Statement of
Operations for the Six Months Ended June 30, 1995 filed above in Item 7(b).

OMITTED:  See the Unaudited Pro Forma Condensed Consolidated Statement of
Operations for the Year Ended December 31, 1994 filed above in Item 7(b).

OMITTED:  See the Notes to Pro Forma Adjustments to Unaudited Pro Forma
Condensed Consolidated Financial Statements and Notes, Notes to Pro Forma
Adjustments to the Unaudited Pro Forma Condensed Consolidated Financial
Statements and Notes to Conversion Adjustments to the Unaudited Pro
Forma Condensed Consolidated Financial Statements filed above in Item 7(b).

             PRO FORMA CONSOLIDATED CAPITALIZATION

The   following  table  sets  forth  the  short-term   debt   and
capitalization of Orbital, on a pro forma consolidated basis,  to
give effect to the Arrangement.

                                              June 30, 1995
                                               (Pro Forma)
                                                 (US$ in
                                               thousands)
Short-term debt:                                            
    Current portion of long-term                   $   5,639
    obligations                                        7,005
    Short-term bank borrowings                     $  12,644
Total short-term debt

Long-term debt:                                             
    Long-term obligations, net of                     34,927
    current portion                                   20,000
    10 1/2% Senior Notes due 2002                     56,000
    6 3/4% Convertible Subordinated                  $110,927
    Debentures due 2003
Total long-term debt

Stockholders' equity:                                       
    Preferred Shares, par value $0.01                       
    per share: 10,000,000                                  --
     authorized; no shares issued and
    outstanding                                           

    Preferred Series A Shares, par value
    $0.01 per share:                                      --
     one share authorized; no shares                        
    issued and outstanding (1)                              

    Preferred Series B Shares, no par
    value: 10,000 authorized, issued
    and outstanding (2)                                   10

    Preferred Series B Shares, no par                    
    value:                                           
     10,000 authorized, issued and                   
    outstanding (2)                                    

    Common Shares, par value $0.01 per                    266
    share: 40,000,000                               
     authorized; 26,556,640 shares                  
    issued and outstanding
     after adjusting for 15,735 shares
    in treasury (3)

    Additional paid-in capital                        246,243

    Cumulative translation adjustment                  (3,571)

    Unrealized losses on short-term                      (221)
    investments

    Retained earnings (deficit)                        (1,960)

Total stockholders' equity                           $240,767

Total capitalization                                 $351,694


Notes:
(1)  The Preferred Series A Share issued by Orbital is held under
     the Voting and Exchange Trust Agreement and is eliminated in
     consolidation.
(2)  Preferred  Series  B  Shares are issued  by  Acquisition  to
     Canadian   Imperial  Bank  of  Commerce  pursuant   to   the
     Arrangement.
(3)  Assumes   an   immediate   exchange   of   all   outstanding
     Exchangeable Shares and exercise of Replacement Options  for
     3,920,290 Orbital Common Shares.  Excludes 3,900,945 Orbital
     Common  Shares issuable upon conversion of Orbital's 6  3/4%
     Convertible  Subordinated Debentures due 2003 and  1,661,146
     Orbital  Common  Shares reserved for  issuance  pursuant  to
     options  outstanding as of September 8, 1995  with  exercise
     prices ranging from US$7.50 to US$22.00 per share.

                          RISK FACTORS


The   following  risk  factors  related  to  Orbital  should   be
considered  by  MDA  Shareholders and MDA 1988  Optionholders  in
evaluating whether to approve the Arrangement Resolution.   These
factors  should  be  considered in  conjunction  with  the  other
information  included in this Proxy Circular.  In  addition,  MDA
Shareholders  and  MDA 1988 Optionholders should  refer  to  "The
Arrangement - Reasons for Recommendation of the MDA Board."

Technologically Advanced Products and Services

Most  of  the products developed and manufactured by Orbital  are
technologically  advanced and novel systems  that  must  function
under   demanding  operating  conditions.   Even  though  Orbital
believes  it  employs  sophisticated  design,  manufacturing  and
testing  practices,  there  can be no  assurance  that  Orbital's
products  will be successfully launched or operated or that  they
will  be  developed  or  will perform as  intended.   Certain  of
Orbital's  contracts require it to forfeit part of  its  expected
profit,  to  receive reduced payments, to provide  a  replacement
launch  or  other product or service, or to reduce the  price  of
follow-on  missions  if its products fail to perform  adequately.
Performance penalties also may be imposed should Orbital fail  to
meet   delivery   schedules  or  other   measures   of   contract
performance.   Orbital, like most companies and governments  that
have  launch  and satellite programs, has experienced  occasional
product  failures and other problems, including with  respect  to
certain  of  its  launch vehicles and satellites.   For  example,
Orbital's  first  two  flights of the  Pegasus  XL  space  launch
vehicle in June 1994 and June 1995 were unsuccessful.

Orbital's  products  and services are and  will  continue  to  be
subject  to  significant  technological  change  and  innovation.
Orbital's  success  will  generally  depend  on  its  ability  to
penetrate  and  retain markets for its existing products  and  to
continue to conceive, design, develop, manufacture and market new
products  and  services  on a cost-effective  and  timely  basis.
Orbital  anticipates that it will incur significant  expenses  in
the design, development and initial manufacture and marketing  of
new  products  and  services.  There can  be  no  assurance  that
Orbital  will  be  able  to  achieve the  technological  advances
necessary to remain competitive and profitable, that new products
and  services will be developed and manufactured on schedule  and
on a cost-effective basis, that licenses and regulatory approvals
required for new products and services will be secured,  or  that
anticipated  markets will exist or develop for  new  products  or
services.

Dependence on United States Government

A  significant percentage of Orbital's backlog is with  the  U.S.
Government  or under subcontracts with prime contractors  to  the
U.S.  Government.   Most  of Orbital's government  contracts  are
funded  incrementally  on  a  year-to-year  basis.   Changes   in
government policies, priorities or funding levels through  agency
or  program  budget  reductions  by  the  U.S.  Congress  or  the
imposition  of  budgetary constraints could materially  adversely
affect    Orbital's    business   and   financial    performance.
Furthermore, contracts with the U.S. Government may be terminated
or  suspended by the U.S. Government at any time, with or without
cause.

Capital Requirements

Orbital's  future  business requirements and  growth  plans  will
require  significant additional capital.  Orbital  believes  that
working capital, cash from operations, operating leases, customer
financing and available bank borrowings will be adequate to  meet
these  capital needs through 1995.  Orbital expects that it  will
need to incur indebtedness or raise additional equity capital  to
fund  its  anticipated growth in 1996 and beyond.  While  Orbital
believes  that,  if necessary, it has flexibility  to  reduce  or
delay  its  anticipated capital requirements and its  anticipated
investments  in ORBIMAGE or the X-34 program, such reductions  or
delays   could  impede  Orbital's  growth  and  adversely  affect
Orbital's results of operations.

The  ORBCOMM System and the X-34 program are in relatively  early
stages and the actual cost of each project may vary significantly
from  current  estimates.  In addition to the funds committed  by
Orbital  and  its respective partner in each venture,  additional
financing  from the partners and/or third party sources  will  be
required, and there can be no assurance that the required capital
will be received.  In the event that the necessary capital cannot
be  obtained,  implementation and commercial development  of  the
ORBCOMM  System or X-34 will be delayed, significantly restricted
or  possibly abandoned, and Orbital could be required to  expense
part  or all of its investment in the ORBCOMM System or the  X-34
program, as the case may be.

Orbital  has  invested  and will continue to  invest  substantial
resources  in  capital equipment and other assets supporting  its
various  products  and programs.  In the event  of  significantly
reduced  or eliminated product sales with respect to a particular
program, Orbital could be required to expense some or all of  its
investments in assets dedicated to that program.

Regulation

The  ability  of  Orbital  to pursue its business  activities  is
regulated  by  various  agencies  and  departments  of  the  U.S.
Government.  Commercial space launches require licenses from  the
U.S.  Department  of  Transportation  ("DoT")  and  operation  by
Orbital  of  its  leased L-1011 aircraft requires  licenses  from
certain  agencies  of  the DoT, including  the  Federal  Aviation
Administration.  Construction, launch and operation of commercial
communications satellites, including the ORBCOMM System,  require
licenses  from  the  U.S. Federal Communications  Commission  and
frequently  require  the  approval  of  international  regulatory
authorities.   Some  planned  ORBIMAGE  private  remote   sensing
satellites  require  a  license  from  the  U.S.  Department   of
Commerce.   Exports of Orbital's products, services and technical
information frequently require licenses from the U.S.  Department
of  State  or the U.S. Department of Commerce.  There can  be  no
assurance  that  Orbital will continue to be  successful  in  its
efforts to obtain necessary licenses or regulatory approvals.

         THE SPECIAL MEETING - GENERAL PROXY INFORMATION

General

This Proxy Circular is furnished to MDA Shareholders and MDA 1988
Optionholders in connection with the solicitation of  proxies  by
management of MDA to be used at the Special Meeting to be held on
Tuesday, November 14, 1995 at 10:00 a.m., Vancouver time, at  the
offices  of  MDA  at  13800 Commerce Parkway,  Richmond,  British
Columbia,  V6V  2J3,  and  at any adjournments  or  postponements
thereof for the purposes set forth in the accompanying Notice  of
Special Meeting.  The information contained herein is given as at
September 29, 1995, except where otherwise noted.

Solicitation of Proxies

In  addition  to  solicitation by mail, officers,  directors  and
regular  employees  of MDA may, without additional  compensation,
solicit  proxies personally or by telephone or telecopier.   This
solicitation is made on behalf of management of MDA and the  cost
of the solicitation will be borne by MDA.

Arrangements   will  be  made  with  custodians,   nominees   and
fiduciaries  for  forwarding  proxy  solicitation  materials   to
beneficial  owners of MDA Common Shares held of  record  by  such
custodians, nominees and fiduciaries, and MDA will reimburse such
custodians,  nominees  and fiduciaries  for  reasonable  expenses
incurred in connection therewith.

In  order  to be valid for use at the Special Meeting, any  proxy
must be received by Montreal Trust Company of Canada, 510 Burrard
Street,  Vancouver,  British Columbia, V6C  3B9,  not  less  than
48  hours  (excluding Saturdays, Sundays and holidays)  preceding
the Special Meeting or any adjournment thereof.

Appointment of Proxies

The persons named in the enclosed proxy are directors or officers
of MDA.  A MDA Shareholder or MDA 1988 Optionholder who wishes to
appoint  some other person to represent him or her at the Special
Meeting  may do so by inserting such person's name in  the  blank
space provided in the form of proxy or by completing another form
of  proxy and, in either case, delivering it or returning  it  by
mail  so  that  it is received by the stated deadline.   A  proxy
nominee need not be an MDA Shareholder or MDA 1988 Optionholder.

Signing of Proxies

The  proxy  must  be signed by the MDA Shareholder  or  MDA  1988
Optionholder,  as  the case may be, or by  his  or  her  attorney
authorized  in  writing,  as his or her  name  appears  on  MDA's
register  of  shareholders or records  of  holders  of  MDA  1988
Options.  If the MDA Shareholder is a corporation, the proxy must
be executed by a duly authorized officer or attorney thereof.

Revocation of Proxies

In addition to revocation in any other manner permitted by law, a
proxy  given  pursuant to this solicitation  may  be  revoked  by
instrument in writing executed by the MDA Shareholder or MDA 1988
Optionholder,  as  the case may be, or by  his  or  her  attorney
authorized   in  writing  or,  if  the  MDA  Shareholder   is   a
corporation, by a duly authorized officer or attorney thereof and
deposited either:

          (i)  at the registered office of MDA at any time up  to
          and  including the last business day preceding the  day
          of   the  Special  Meeting,  or  any  adjournments   or
          postponements thereof; or

          (ii)  with the chairman of the Special Meeting  on  the
          day  of  the  Special Meeting prior to the commencement
          thereof, or any adjournments or postponements thereof.

Upon either of such deposits, the former proxy will be revoked.

Voting of Proxies

The  persons  named  in the enclosed proxy  will  vote  "FOR"  or
"AGAINST"  the Arrangement Resolution such number  of  shares  or
votes with respect to which such persons are appointed proxy,  on
the  ballot to be cast with respect to the Arrangement Resolution
in accordance with the instructions of the MDA Shareholder or MDA
1988  Optionholder appointing them.  In the absence of  direction
or  instruction,  shares  or  votes  represented  by  a  properly
executed  proxy  will be voted "FOR" approval of the  Arrangement
Resolution.

The  enclosed form of proxy confers discretionary authority  upon
the  persons designated therein with respect to amendments to  or
variations  of matters identified in the accompanying  Notice  of
Special Meeting of Shareholders and with respect to other matters
that  may properly come before the Special Meeting.  At the  date
of  this  Proxy Circular, the management of MDA knows of no  such
amendments,  variations or other matters.  However, if  any  such
amendments,  variations or other matters not presently  known  to
the  management  of MDA should properly come before  the  Special
Meeting,  the shares represented by the proxies will be voted  in
accordance with the best judgment of the person or persons voting
such proxies, absent contrary instructions.

MDA Common Shares

On  September 29, 1995, MDA had outstanding 11,218,156 MDA Common
Shares; the only shares of MDA issued and outstanding.  Each  MDA
Shareholder  of  record at the close of business on  October  10,
1995,  the  record  date established for notice  of  the  Special
Meeting,  will be entitled to one vote for each MDA Common  Share
held  by  him or her on all matters proposed to come  before  the
Special  Meeting,  except  to the  extent  that  he  or  she  has
transferred any MDA Common Shares after the record date  and  the
transferee  of  such  shares  produces  properly  endorsed  share
certificates or otherwise establishes ownership thereof and makes
a  written  demand,  not  later than the  close  of  business  on
November  3,  1995,  to be included in the list  of  shareholders
entitled  to  vote  at the Special Meeting,  in  which  case  the
transferee will be entitled to vote such shares.

MDA 1988 Options

On   September  29,  1995,  MDA  had  277,643  MDA  1988  Options
outstanding.  Each MDA 1988 Optionholder on the date  of  mailing
will  receive  notice of the Special Meeting and  each  MDA  1988
Optionholder,  on  the  date  of the  Special  Meeting,  will  be
entitled  to  one vote for each MDA Common Share such  person  is
entitled to purchase under a MDA 1988 Option.

Required  Votes to Approve the Arrangement and Voting  Intentions
of Certain Shareholders and Optionholders

Subject  to  any  further  order of the  Court,  the  Arrangement
Resolution  must be approved by the affirmative vote of  66K%  of
the  votes actually cast thereon by the MDA Shareholders  and  by
the  MDA 1988 Optionholders, voting as separate classes, and  for
this  purpose any spoiled votes, illegible votes, defective votes
and abstentions shall be considered not to be votes cast.

As at September 29, 1995, the directors and officers of MDA as  a
group  beneficially owned approximately 23.6% of the  outstanding
MDA  Common Shares and executive officers of MDA as a group  held
approximately 47.0% of the outstanding MDA 1988 Options.

All  of  the  directors and officers of MDA and MDA  Shareholders
holding 10% or more of the MDA Common Shares have executed Voting
Agreements  and  Irrevocable Proxies agreeing to hold  their  MDA
Common Shares and to vote for the Arrangement Resolution.   These
agreements  represent  56.6%  of  the  votes  attached   to   the
outstanding  MDA  Common  Shares.   In  addition,  officers   and
employees  of MDA holding approximately 59.2% of the total  votes
entitled  to  be cast by MDA 1988 Optionholders have agreed  with
MDA to hold their options and vote for the Arrangement Resolution
in  their  capacity  as  MDA 1988 Optionholders.   All  of  these
agreements  contain provisions which provide for  termination  in
certain circumstances, including if the Combination Agreement  is
terminated.  See "The Arrangement and the Combination Agreement -
Interests  of  Certain  Persons in the Arrangement"  and  "-  The
Combination Agreement - Termination and Amendment."

Principal Holders of MDA Common Shares and MDA 1988 Options

To  the knowledge of the directors and officers of MDA, the  only
persons who beneficially own, directly or indirectly, or exercise
direction over, MDA Common Shares carrying more than 10%  of  the
votes attached to all of the MDA Common Shares are as follows:

<TABLE>
<CAPTION>

                                        Number of MDA Common
     Name of Shareholder                Shares Beneficially Held         Percentage

<S>                                    <C>                              <C>
     Ventures West Technologies (1)     2,404,104                               21%
     Spar Aerospace Limited             1,292,709                               12%
     John W. Pitts (2)                  1,154,314                               10%
     John S. MacDonald (3)              1,110,449                               10%

</TABLE>

Notes:
(1)  Ventures  West  Technologies' holdings are  in  two  limited
     partnerships:   Ventures  West Technologies  (1994)  Limited
     Partnership   owns  1,879,666  shares  and   Ventures   West
     Technologies Limited Partnership owns 524,438 shares.
(2)  Mr.  Pitts  controls 1,154,314 MDA Common Shares  indirectly
     through Anako Holdings Inc.
(3)  Dr.   MacDonald   controls  1,110,449  MDA   Common   Shares
     indirectly through QuMac Enterprises Limited.

There  is no MDA 1988 Optionholder carrying the right to vote  at
the Special Meeting more than 10% of the votes attached to all of
the MDA 1988 Options.

Each   of  the  above  MDA  Shareholders  have  executed   Voting
Agreements  and  Irrevocable Proxies agreeing to hold  their  MDA
Common Shares and to vote for the Arrangement Resolution.

Management of MDA has been advised that Orbital does not own  any
MDA Common Shares.


         THE ARRANGEMENT AND THE COMBINATION AGREEMENT

The Arrangement - General

MDA  Shareholders and MDA 1988 Optionholders are being  asked  to
approve  the  Arrangement under the CBCA whereby:  (i)  MDA  will
become  a  wholly-owned subsidiary of Acquisition and an indirect
subsidiary   of  Orbital;  (ii)  MDA  Shareholders  (other   than
Dissenting  MDA  Shareholders but including  Qualifying  Holdcos)
will  receive, in exchange for all of their MDA Common Shares,  a
number  of  Exchangeable  Shares equal  to  the  product  of  the
Exchange Ratio multiplied by the number of MDA Common Shares held
by  them; and (iii) holders of MDA Options (other than Dissenting
MDA  1988  Optionholders) will receive, in exchange for  each  of
their  MDA  Options,  a  Replacement  Option  entitling  them  to
purchase  a number of Orbital Common Shares equal to the  product
of  the  Exchange Ratio multiplied by the number  of  MDA  Common
Shares  underlying such MDA Option, having an exercise price  per
share  equal to the quotient of the exercise price per  share  of
such  MDA  Option divided by the Exchange Ratio, and  having  the
same vesting, expiration and other terms as such MDA Option.  The
Exchangeable  Shares will have voting, dividend  and  liquidation
rights  that are, as nearly as practicable, equivalent  to  those
rights of the Orbital Common Shares.

Holders  of  Exchangeable Shares will have the right to  exchange
all  or  any  of  such  shares for an equal  number  (subject  to
adjustment  in  the  event  of  certain  capital  and   corporate
reorganizations)  of  Orbital Common  Shares  plus  the  Dividend
Amount  attributable to such shares, at any  time  prior  to  the
Automatic  Redemption Date and subject to certain Call Rights  of
Orbital.  The Exchangeable Shares will be automatically exchanged
on  the  Automatic  Redemption Date and upon  the  occurrence  of
certain events, including the liquidation, dissolution or winding-
up  of Orbital or Acquisition or the default by Acquisition under
the Exchangeable Share Provisions.  Acquisition has the right  to
accelerate  the Automatic Redemption Date upon 75  days'  written
notice  to  the holders of Exchangeable Shares at any  time  when
there are outstanding less than 400,000 Exchangeable Shares  held
by persons other than Orbital and its Affiliates.

Background of the Arrangement

On  March  31,  1995,  the  MDA Board engaged  Nesbitt  Burns  as
financial advisors to MDA to assist in determining whether or not
it  would  be  advantageous  for MDA to  proceed  with  a  public
offering of MDA Common Shares, and to provide advice with respect
to  any  acquisition transaction relating to MDA or  to  the  MDA
Common  Shares.   An engagement letter was executed  by  MDA  and
Nesbitt Burns on June 15, 1995.  At the March 31 meeting the  MDA
Board  proposed  the  terms  of  bonus  arrangements  for  senior
employees in the event of the completion of certain transactions.
See "The Arrangement and the Combination Agreement - Interests of
Certain Persons in the Arrangement."

On  June 8, 1995, at a regularly scheduled board meeting the  MDA
Board  was  advised by a director that Orbital had  indicated  an
interest  in acquiring all of the MDA Common Shares.   Management
was  instructed  by  the  MDA Board  to  meet  with  Orbital  and
determine whether or not a transaction could be proceeded with.

On  June 14, 1995, senior management of MDA and advisors  met  in
Richmond,  B.C.  with senior management of Orbital  to  determine
Orbital's  level  of  interest  and  the  general  terms   of   a
transaction,  including the requirements that the transaction  be
effected  as  a pooling of interests and on a tax deferred  basis
for Canadian MDA Shareholders.

On  June  19,  1995,  the MDA Board met and was  advised  of  the
position  of  Orbital and the general terms of  the  transactions
contemplated.  Management was advised to conduct due diligence on
Orbital  and  if  the  results were  positive,  to  proceed  with
negotiations  with  Orbital  to reach  an  agreement  as  to  the
structure and price of a proposed transaction.

On  June  23,  1995,  Orbital and MDA  signed  a  confidentiality
agreement  and  Orbital  agreed not to purchase  any  MDA  Common
Shares.

During  the period from June 26 to July 12, 1995, executives  and
advisors of Orbital met with representatives of MDA in Vancouver,
B.C. and conducted due diligence on MDA.  Executives and advisors
of MDA met with representatives of Orbital at Orbital's office in
Dulles,   Virginia  and  conducted  due  diligence  on   Orbital.
Discussions  of  a  general nature were held on  the  form  of  a
proposed   transaction,  including  the  requirements  that   the
transaction  be effected on a pooling of interests basis  through
an   arrangement  under  the  CBCA,  and  whereby  Canadian   MDA
Shareholders  would receive a tax deferral as  a  result  of  the
transaction.  In addition, senior management and advisors of  MDA
met   with  senior  management  and  advisors  of  Orbital.   The
preliminary  terms of a proposal were presented  by  Orbital  and
Orbital  and  MDA  commenced  preliminary  negotiations  on   the
exchange  ratio  (price),  conditions  for  completion   of   the
transaction,  factors relating to the exchange ratio,  and  other
related matters.

On  July  13,  1995,  the MDA Board met and was  advised  of  the
results   of   due  diligence  on  Orbital  and  the  preliminary
negotiations.   Representatives  of  Nesbitt  Burns  presented  a
preliminary  review  of the proposed transaction,  including  the
range of prices then being discussed and its preliminary view  as
to  the fairness of a transaction from a financial point of view.
The  MDA  Board  was  advised  of  the  duties  of  directors  in
transactions such as the one being proposed by Orbital.

From  July 17 to July 25, 1995, senior management of MDA and  its
advisors  met  with  senior management  of  Orbital  to  continue
negotiations.   Orbital  and  MDA and  their  advisors  commenced
preparation of the Affiliate Agreements and Voting Agreements and
Irrevocable Proxies.  Drafts of these agreements were  circulated
to  certain shareholders, directors and officers of MDA who would
be required to execute the same.  On July 18, 1995, the MDA Board
met and was advised of the status of negotiations and on July 20,
1995,  MDA  signed a letter with Orbital agreeing not to  solicit
other business combinations except as specified.

On July 27, 1995, the MDA Board met and was updated on the status
of   negotiations  and  the  status  of  the  position  of  major
shareholders   including   Spar   Aerospace   Limited   ("Spar").
Management  was  advised  to  continue  negotiations  and   those
negotiations  were proceeded with.  The meeting  adjourned  until
July  28, 1995 following a meeting between Mr. Wallis of MDA  and
senior  management  of Spar.  At the adjourned  meeting  the  MDA
Board  was  advised of Spar's position and that a  meeting  among
senior  executives  of MDA, Orbital and Spar  would  be  held  on
July  31, 1995.  On July 28, 1995, MDA was advised that Orbital's
board  of  directors  had  given approval  in  principle  to  the
proposed transaction.

On  July 31, 1995, trading in MDA Common Shares was halted on the
TSE  and VSE pending a press release.  MDA, Orbital and Spar  met
to discuss the terms of the proposed transaction and implications
to   Spar.   Spar  senior  management  advised  that  they  would
recommend   supporting  the  transaction  to  Spar's   board   of
directors.   On that date, Orbital and MDA executed a  memorandum
of  understanding with respect to the transaction and each of MDA
and Orbital issued press releases with respect thereto.

On  August  3,  1995, the MDA Board ratified  and  confirmed  the
memorandum  of  understanding,  approved  proceeding   with   the
preparation  of definitive agreements for the completion  of  the
transaction  with  Orbital  and  waived  the  provisions  of  the
Shareholder  Protection Rights Plan to permit  the  execution  of
Voting   Agreements   and  Irrevocable  Proxies   and   Affiliate
Agreements.  Representatives of Nesbitt Burns took part  in  this
meeting  and  gave  an  oral  opinion  on  the  fairness  of  the
Arrangement from a financial point of view.

From  August 5 to August 31, 1995, negotiations were held on  the
form  of  the  definitive  agreements  and  transactions  related
thereto.   On August 17, 1995 the MDA Board met.  Representatives
of  Nesbitt Burns updated the MDA Board with respect to its  view
on  the  fairness of the Arrangement to MDA Shareholders and  MDA
1988  Optionholders and confirmed its opinion on the fairness  of
the  Arrangement.   The MDA Board reviewed and commented  on  the
draft  definitive agreements including the Combination  Agreement
and   discussed  certain  conditions  and  changes  with  respect
thereto.

On   August  17,  1995,  the  MDA  Board  formally  approved  and
authorized execution of the Combination Agreement and waived  the
provisions  of the Shareholder Protection Rights Plan  to  permit
the  transactions contemplated by the Arrangement to be effected.
On  August  18,  1995,  the Orbital board of  directors  met  and
approved the definitive agreements in the form presented, subject
to Orbital's management negotiating the terms of a fee payable by
MDA  in the event MDA were to terminate the Combination Agreement
and  not proceed with the transaction because a higher bona  fide
offer was received by MDA.  Negotiations were conducted over  the
period from August 21 to 22, 1995.  In exchange for the agreement
of  MDA  to  provide  a  break-up fee of  US$750,000  in  certain
circumstances,  the parties agreed that the maximum  and  minimum
range  within which the Exchange Ratio was established be changed
from .3488 to .3607 for the maximum, and from .2578 to .2705  for
the minimum.

From  August  25 to August 31, 1995, the disclosure schedules  of
the  respective parties were reviewed.  On August  31,  1995  the
definitive Combination Agreement was executed, subject to receipt
from Spar of an executed Affiliate Agreement and Voting Agreement
and  Irrevocable Proxy.  These agreements were received from Spar
on September 1, 1995.

On  September 5, 1995, MDA and Orbital issued press releases with
respect  to the execution of the definitive Combination Agreement
and terms of the Arrangement.

As  of  September 29, 1995, the Combination Agreement was amended
and   restated  to  reflect,  inter  alia,  amendments   to   the
Exchangeable Share Provisions as a result of Orbital obtaining  a
"no-action"  letter from the SEC with respect  to  the  issue  of
Orbital Common Shares on the exchange of the Exchangeable Shares.

MDA's Reasons for the Arrangement and Recommendations of the  MDA
Board

On  October  5,  1995  the  MDA Board  unanimously  approved  the
Arrangement and determined that the Arrangement was fair  and  in
the  best interests of MDA, the MDA Shareholders and the MDA 1988
Optionholders.   The  MDA  Board unanimously  recommends  to  MDA
Shareholders and MDA 1988 Optionholders that they vote "FOR"  the
Arrangement Resolution.  The MDA Board based its approval of  the
Arrangement on its determination that the Exchange Ratio is  fair
to  MDA, MDA Shareholders and MDA 1988 Optionholders, and upon  a
number  of  other  factors, including  its  views  regarding  the
following:

          (i)  as of July 28, 1995, the last trading day prior to
          the   public  announcement  of  the  Arrangement,   the
          consideration  provided under the  Arrangement  to  MDA
          Shareholders and MDA 1988 Optionholders of Cdn$7.35 per
          MDA  Common Share (based on currency exchange rates  at
          that date), and provided that the Average Closing Price
          is  US$15.00 or more, represented a 34% premium to  the
          closing  price of MDA Common Shares on the TSE on  that
          date;

          (ii) the Arrangement will provide MDA Shareholders  and
          MDA  1988 Optionholders with the opportunity to receive
          Orbital   Common  Shares,  a  security   that   has   a
          significantly larger market float and greater liquidity
          than MDA Common Shares;

          (iii)                     the opinion of the MDA  Board
          that  the  combination of Orbital's space  and  defence
          business with MDA's expertise in earth imaging and  air
          navigation    systems   will   result    in    expanded
          opportunities  for  MDA's  core  business  that  should
          strengthen overall combined operations;

          (iv)  the  fact  that Orbital's business combined  with
          MDA's   business  after  the  Arrangement   will   have
          significantly greater financial and business  resources
          than  those  of  MDA  alone,  which  may  enable  MDA's
          business  to  compete more effectively with competitors
          having   greater  resources  than  MDA  alone  and   to
          negotiate future acquisitions;

          (v)   the  geographic  distribution  of  customers  for
          Orbital's and MDA's business are complementary and will
          allow  these businesses easier access to new customers;
          and

          (vi)  the  discussions between management  of  MDA  and
          senior executives of Orbital relating to operations  of
          MDA, after the Effective Date.

The  MDA  Board  also  considered the  following  information  in
concluding that the Arrangement and the Exchange Ratio  are  fair
to MDA Shareholders and MDA 1988 Optionholders: (i) its knowledge
of   the   business,  operations,  property,  assets,   financial
condition,  operating results and prospects of MDA  and  Orbital;
(ii)  current industry, economic and market conditions and trends
and  its  informed expectations of the future of the industry  in
which MDA operates; (iii) the opinion of Nesbitt Burns as to  the
fairness from a financial point of view of the Arrangement to MDA
Shareholders and to the MDA 1988 Optionholders; (iv) the terms of
the  Combination Agreement; (v) the structure and accounting  and
tax  treatment  of  the  Arrangement;  and  (vi)  the  respective
corporate cultures and strategies of MDA and Orbital.

In  view of the variety of factors considered in connection  with
its evaluation of the Arrangement, the MDA Board did not find  it
practicable to and did not quantify or otherwise assign  relative
strengths  to  the specific factors considered  in  reaching  its
determination.

Orbital's Reasons for the Arrangement

Orbital  believes that the combination of the two companies  will
expand  the  vertical integration of Orbital's manufacturing  and
testing   capabilities,  enhance  Orbital's  ability   to   offer
customers  complete  space-based systems  and  augment  Orbital's
satellite   tracking  product  line  and  customer   base.    The
combination  of MDA's expertise in satellite ground  systems  and
related information processing software with services offered  by
Orbital  is  expected to achieve synergies that should strengthen
Orbital's ability to offer affordable space-based services, while
also  expanding  the combined company's overall commercial  base.
Orbital  also  anticipates  that MDA's significant  international
presence will solidify Orbital's expansion of its existing  lines
of business into international markets.  Finally, Orbital expects
to  realize synergies due to the ability of the combined  company
to  integrate MDA's technical expertise in such areas as advanced
space-qualified  software,  air navigation  systems  and  defence
electronics   with  Orbital's  existing  defence   and   avionics
products.

Operations Following the Arrangement

Following the Arrangement, Orbital expects that MDA will continue
to operate as a separate entity, substantially in the same manner
as it is operated prior to the Effective Date.

Interests of Certain Persons in the Arrangement

In  considering the recommendation of the MDA Board with  respect
to  the  Arrangement, MDA Shareholders and MDA 1988 Optionholders
should  be aware that certain officers and directors of  MDA  had
interests in the Arrangement, including those referred to  below,
that  may present potential conflicts of interest.  The MDA Board
was  aware of these potential conflicts and considered them along
with  the  other  matters described in "The Arrangement  -  MDA's
Reasons  for  the  Arrangement and  Recommendations  of  the  MDA
Board."

Dr.  John S. MacDonald, Chairman of MDA will be asked to join the
board  of  directors  of  Orbital. On  the  Effective  Date,  Dr.
MacDonald will execute an Employment Agreement with MDA.

The  President and each area general manager of MDA will  execute
an  Employment Agreement with MDA which will provide for  payment
of  compensation in accordance with industry standards  and  will
contain an obligation on the employee not to compete with MDA for
a  two  year period following the  Effective Date.  The Chairman,
the  President  and  each general manager will also  concurrently
enter  into a Change of Control Agreement with Orbital that  will
provide  compensation to them of two times their annual level  of
compensation  if  their  employment with  MDA  is  terminated  or
changed in certain circumstances following a change of control of
Orbital or MDA after the Effective Date.

The  MDA Board, in March, 1995, approved the grant of a bonus  to
certain  members  of  MDA  management in  the  event  of  certain
transactions  such as share dispositions and sales of  assets  of
MDA  occurring, to compensate for the fact that change of control
agreements  were  not in place for these members  of  management.
The  amount  of  the  bonus  will  based  on  the  value  of  the
transaction,  including the price for MDA Common Shares  obtained
thereunder.  If a transaction were completed at a price no higher
than the price for MDA Common Shares at the time of the grant  no
bonus  would  have been payable under the formula therefor.   The
aggregate  amount of this bonus will be allocated  among  certain
members   of  MDA's  management,  including  officers,   by   the
compensation  committee  of  the MDA  Board  and  while  not  yet
definitively allocated, the amount paid to any one recipient  may
be significant to that recipient.

Opinion of MDA's Financial Advisor

MDA  appointed  Nesbitt Burns on March 31, 1995  to  act  as  the
exclusive  financial advisor to MDA and to evaluate the  fairness
from  a financial point of view to MDA Shareholders and MDA  1988
Optionholders  of  certain business transactions,  including  the
Arrangement.  An engagement letter was executed on June 15,  1995
relating  to this appointment.  Nesbitt Burns was retained  based
on  its  experience  as a financial advisor  in  connection  with
mergers  and acquisitions and in securities valuation as well  as
Nesbitt Burns' familiarity with relevant markets and with MDA.

As compensation for its financial advisory services in connection
with  a  proposed business combination Arrangement MDA agreed  to
pay   Nesbitt  Burns  a  success  fee  on  the  closing  of   any
transaction.   Assuming  the Average  Closing  Price  is  between
US$15.00   and  US$20.00,  this  fee  is  estimated  to   be   to
Cdn$981,000.   Whether or not a transaction is  consummated,  MDA
has  agreed  to  reimburse Nesbitt Burns  for  its  out-of-pocket
expenses,  including reasonable counsel fees,  and  to  indemnify
Nesbitt  Burns  against  certain  liabilities  and  expenses   in
connection  with  its  services  as  financial  advisor  to  MDA,
including liabilities arising under securities laws.

Nesbitt  Burns first delivered to the MDA Board its oral  opinion
on  fairness of the Arrangement at the MDA Board meeting held  on
August   3,  1995.   Concurrently  with  the  execution  of   the
Combination Agreement on August 31, 1995, Nesbitt Burns delivered
to  the MDA Board a written opinion that the Arrangement was fair
to  the  MDA Shareholders and the MDA 1988 Optionholders  from  a
financial  point of view.  This opinion was subsequently  updated
to  October 4, 1995.  The complete text of Nesbitt Burns' opinion
is attached hereto as Appendix "C" and the summary of the opinion
set forth below is qualified in its entirety by reference to such
opinion.   MDA Shareholders and MDA 1988 Optionholders are  urged
to  read  such  opinion  carefully and  in  its  entirety  for  a
description  of  the procedures followed, the factors  considered
and  the  assumptions made by Nesbitt Burns.  In connection  with
the rendering of its opinion dated October 4, 1995, Nesbitt Burns
among other things reviewed and relied upon:

(a)  the  most  recent  available draft of  this  Proxy  Circular
     prepared in connection with the Arrangement;

(b)  the Combination Agreement as at September 29, 1995;

(c)  the Voting Agreements and Irrevocable Proxies;

(d)  the  agreement dated as of July 31, 1995 between Orbital and
     MDA  outlining  the  proposed terms and  conditions  of  the
     Arrangement;

(e)  the  Agreement dated July 20, 1995 between Orbital  and  MDA
     relating to MDA's agreement not to solicit third party  bids
     ("No-Shop Agreement");

(f)  audited  financial statements of MDA for each of the  fiscal
     years  in the five-year period ended March 31, 1995 and  the
     unaudited  financial statements of MDA for the  three  month
     periods ended June 30, 1994 and June 30, 1995;

(g)  the  budget  for  MDA for the fiscal year ending  March  31,
     1996;

(h)  the strategic plan for MDA dated April 24, 1995 for the five
     fiscal   years  ending  March  31,  2000  prepared  by   the
     management of MDA;

(i)  certain income tax information with respect to MDA;

(j)  publicly  available  information related  to  the  business,
     operations  and  consolidated financial performance  of  MDA
     including  the annual report to shareholders for the  fiscal
     year ended March 31, 1995;

(k)  confidential  information provided to Nesbitt Burns  by  the
     management of MDA consistent with that disclosed to Orbital;

(l)  discussions  with senior management of MDA with  respect  to
     the  information referred to in (f), (g), (h), (i)  and  (j)
     above,  and  MDA management's assessment of the current  and
     prospective  operations of MDA and the industries  in  which
     they operate;

(m)  relevant stock market information relating to the MDA Common
     Shares  and  the shares of other companies whose  activities
     include businesses similar to certain of MDA's businesses;

(n)  data  with  respect to other transactions  of  a  comparable
     nature considered by Nesbitt Burns to be relevant;

(o)  such  other  financial, market and industry information  and
     such other analysis as Nesbitt Burns considered relevant and
     appropriate in the circumstances; and

(p)  a  certificate  dated  the date of the opinion  from  senior
     officers  of  MDA  as  to the accuracy and  completeness  of
     certain information provided to Nesbitt Burns.

In addition, Nesbitt Burns reviewed and relied upon the following
with respect to Orbital:

(a)  audited  financial statements of Orbital  for  each  of  the
     fiscal years in the five-year period ended December 31, 1994
     and  the  unaudited financial statements for the six  months
     ended June 30, 1994 and June 30, 1995;

(b)  publicly  available  information related  to  the  business,
     operations   and   consolidated  financial  performance   of
     Orbital, including the annual report to shareholders for the
     fiscal year ended December 31, 1994;

(c)  confidential  information provided to Nesbitt Burns  by  the
     management of Orbital consistent with that disclosed to MDA;

(d)  discussions  with senior management of Orbital with  respect
     to the information referred to in (a), (b) and (c) above and
     Orbital   management's  assessment  of   the   current   and
     prospective  operations of Orbital, and  the  industries  in
     which it operates;

(e)  relevant  stock market information relating to  the  Orbital
     Common  Shares  and  the  shares of  other  companies  whose
     activities   include  businesses  similar  to   certain   of
     Orbital's businesses;

(f)  data  with respect to transactions involving other companies
     similar to Orbital; and

(g)  such  other  financial, market and industry information  and
     such other analysis as Nesbitt Burns considered relevant and
     appropriate in the circumstances.

Nesbitt  Burns' conclusion as to the fairness of the  Arrangement
from  a  financial point of view to the MDA Shareholders and  MDA
1988   Optionholders   was  based  upon   various   factors   and
assumptions, including without limitation, the following:

(a)  the  conclusion that fairness in respect of the  Arrangement
     for  MDA  Shareholders or MDA 1988 Optionholders  should  be
     based  upon  whether the consideration to be received  under
     the  Arrangement by current holders of MDA Common Shares  is
     equal  to  or  greater than the bottom end of the  range  of
     values of the MDA Common Shares currently held;

(b)  the  determination that it was not inappropriate to  utilize
     the  market  trading  price  of Orbital  Common  Shares  for
     purposes of its assessment;

(c)  in  assessing  the  MDA Common Shares and the  consideration
     offered  for  each  MDA Common Share,  an  assumption  of  a
     currency  exchange rate of US$0.7361 per Cdn$1.00 as  agreed
     on  July  31, 1995 and US$0.7509 per Cdn$1.00 on October  4,
     1995  and an assumption of a trading value of Orbital Common
     Shares in excess of US$15.00;

(d)  in  assessing  the MDA Common Shares, an approach  to  value
     based  on  MDA  remaining a going concern.  Liquidation  and
     break-up  methodologies were not considered  appropriate  in
     the  circumstances.  Nesbitt Burns considered that the  most
     appropriate  going  concern method to apply  to  MDA  was  a
     discounted  cash  flow ("DCF") approach.  The  DCF  approach
     takes into account the amount, timing and relative certainty
     of  future  cash  flows expected to be  generated  by  MDA's
     businesses   after   provision  for  cash   taxes,   capital
     expenditures  and  changes  in working  capital  and  before
     provisions  for payment to debtholders, interest  income  or
     expense  and  payment to equity holders ("Free Cash  Flow").
     These  Free  Cash  Flow projections were present  valued  by
     applying  an  appropriate weighted average cost  of  capital
     ("WACC").   The  DCF  analysis  included  consideration   of
     sensitivities  in respect of revenue growth, gross  margins,
     levels  of  WACC and the future growth rates  of  Free  Cash
     Flow;

(e)  in order to check the conclusions reached based upon the DCF
     analysis,  a comparison of a range of multiples  implied  by
     Nesbitt  Burns'  analysis to the range of multiples  derived
     from  an analysis of comparable transactions and the  market
     trading of comparable public companies; and

(f)  the  fact  that  the  consideration  value  offered  to  MDA
     Shareholders  of $7.35 per MDA Common Share,  provided  that
     the  Average  Closing  Price is greater  than  or  equal  to
     US$15.00, represents a 53% premium to the closing  price  of
     MDA Common Shares on the TSE on July 19, 1995 (the day prior
     to  MDA and Orbital entering into the No-Shop Agreement) and
     a  34% premium to the closing price of MDA Common Shares  on
     the  TSE on July 28, 1995 (the last trading day prior to the
     announcement of the proposed Arrangement).

Based  on and subject to the foregoing, Nesbitt Burns is  of  the
opinion  that, as of the date of the Opinion, the Arrangement  is
fair,  from  a  financial point of view, to the  holders  of  MDA
Common Shares and MDA 1988 Optionholders.

Plan of Arrangement

Under  the Plan of Arrangement, the following transactions, among
others, shall occur in the following order:

(a)  the authorized share capital of Acquisition shall be amended
     to  authorize  an  unlimited number of  Exchangeable  Shares
     having the rights, restrictions and limitations set forth in
     the  Exchangeable  Share  Provisions  and  10,000  Class   B
     Preferred   Shares  having  the  rights,  restrictions   and
     limitations  set  forth  in  Appendix  A  to  the  Plan   of
     Arrangement;

(b)  Acquisition shall issue 10,000 Class B Preferred  Shares  to
     Canadian  Imperial Bank of Commerce in partial consideration
     for  services rendered to Acquisition in connection with the
     Arrangement;

(c)  all  the  outstanding MDA Common Shares, except  MDA  Common
     Shares  owned  beneficially and of record by the  Qualifying
     Holdcos  and  MDA  Common  Shares  held  by  Dissenting  MDA
     Shareholders, shall be exchanged by the holders thereof  for
     Exchangeable  Shares,  the number  of  which  shall  be  the
     product  of such number of MDA Common Shares being exchanged
     and  the  Exchange Ratio.  Each former holder of MDA  Common
     Shares (other than the Qualifying Holdcos and Dissenting MDA
     Shareholders) shall receive the whole number of Exchangeable
     Shares  resulting  from the exchange of  such  holder's  MDA
     Common Shares for the consideration set out in the foregoing
     sentence  and in lieu of fractional Exchangeable Shares,  an
     amount  in  cash  equal to the fraction  multiplied  by  the
     Average Closing Price, payable in Canadian dollars;

(d)  all the outstanding shares of each of the Qualifying Holdcos
     shall  be  exchanged by the holders thereof for Exchangeable
     Shares,  the  number of which shall be the  product  of  the
     number of MDA Common Shares owned beneficially and of record
     by each respective Qualifying Holdco and the Exchange Ratio.
     Each  former  holder of shares of a Qualifying Holdco  shall
     receive  the  whole number of Exchangeable Shares  resulting
     from  the  exchange  of  all  such  holder's  shares  of   a
     Qualifying  Holdco  for the consideration  set  out  in  the
     foregoing  sentence  and in lieu of fractional  Exchangeable
     Shares,  an  amount in cash equal to the fraction multiplied
     by the Average Closing Price, payable in Canadian dollars;

(e)  each  of the Qualifying Holdcos shall be dissolved into  and
     its  assets distributed to Acquisition and for the  purposes
     of  such dissolution each of the Qualifying Holdcos will  be
     authorized to file articles of dissolution with the Director
     under  CBCA  at  such  time as the  board  of  directors  of
     Acquisition shall determine;

(f)  each   outstanding  MDA  Option,  except  options  held   by
     Dissenting MDA 1988 Optionholders, shall become an option to
     purchase  a  number of Orbital Common Shares  equal  to  the
     product  (rounded  to  the  nearest  whole  number)  of  the
     Exchange Ratio times the number of MDA Common Shares subject
     to  such MDA Option and will have an exercise price equal to
     the  exercise price for such option divided by the  Exchange
     Ratio  and the same vesting, expiration and other  terms  as
     such  MDA  Option  as  in effect immediately  prior  to  the
     Effective Time;

(g)  the MDA 1988 Option Plans will be amended to provide that if
     the  Orbital  Common Shares are changed or exchanged  for  a
     different   kind  or  number  of  securities,  the   options
     thereunder will be amended accordingly; and

(h)  the  name  of  Acquisition shall be  changed  to  "MacDonald
     Dettwiler Holdings Inc."

Contemporaneously with the Arrangement, Orbital  and  Acquisition
will  enter into the Voting and Exchange Trust Agreement and  the
Support  Agreement.   See "The Arrangement  and  the  Combination
Agreement - Description of Exchangeable Shares."

Post-Combination Share Ownership

Upon  completion  of  the Arrangement, Acquisition  will  be  the
beneficial  owner  of all the outstanding MDA Common  Shares  and
Orbital will be the beneficial and registered owner of all of the
Acquisition Common Shares.  The Acquisition Common Shares will be
the  only class of voting securities of Acquisition.  As a result
of the Arrangement, assuming an Exchange Ratio of .3136 (based on
an  assumed  Average Closing Price of US$17.25), the  former  MDA
Shareholders and holders of MDA Options will own or will have the
right  to  acquire (through ownership of Exchangeable Shares  and
Replacement Options) approximately 15% of the outstanding Orbital
Common  Shares  (including  shares issuable  to  holders  of  the
Exchangeable Shares and Replacement Options).

Qualifying Holdcos

Any  MDA Shareholder who wishes to transfer the MDA Common Shares
owned  by  it to a Qualifying Holdco and exchange the  shares  of
such  Qualifying Holdco for Exchangeable Shares pursuant  to  the
Plan  of Arrangement must notify MDA of its desire to do  so  not
less  than  five Business Days prior to the Special  Meeting  and
must   have  entered  into  a  Holding  Company  Agreement   with
Acquisition  and met all the conditions thereunder prior  to  the
date  of  the  Special Meeting.  Acquisition shall enter  into  a
Holding  Company Agreement with each MDA Shareholder who provides
the  aforementioned  notice to MDA and who meets  the  conditions
provided  in  the Holding Company Agreement.  Any MDA Shareholder
who  has  not  entered  into  a Holding  Company  Agreement  with
Acquisition on or before the date of the Special Meeting  or  who
has  entered into such agreement but has failed to meet all  such
conditions  to  the  satisfaction  of  Acquisition  in  its  sole
discretion  shall,  subject to the Plan of Arrangement  receiving
all  necessary  approvals, exchange his or her MDA Common  Shares
for   Exchangeable  Shares  as  an  MDA  Shareholder.   Any   MDA
Shareholder wishing to use a Qualifying Holdco should consult its
legal advisors and tax advisors.

Dissenting Holders

As  permitted in the Interim Order, MDA Shareholders and MDA 1988
Optionholders  may  exercise rights of dissent  with  respect  to
their  MDA Common Shares or the MDA Common Shares underlying  the
MDA  1988  Options  pursuant to and in the manner  set  forth  in
section  190  of  the CBCA and the Plan of Arrangement.   In  the
event  of  the  exercise  of  dissent  rights  by  any  MDA  1988
Optionholders, such MDA 1988 Options shall be deemed to have been
exercised  and  the exercise price of each such MDA  1988  Option
shall be satisfied by reducing the fair market value paid for the
MDA  Common  Shares  underlying such  MDA  1988  Option  by  such
exercise  price,  provided that if the MDA 1988  Optionholder  is
ultimately not entitled to be paid the fair market value for such
underlying  shares, such MDA 1988 Option shall be deemed  not  to
have  been exercised and shall become a Replacement Option.   See
"Dissenting Rights."

Description of Exchangeable Shares

Holders of Exchangeable Shares will have voting, liquidation  and
dividend  rights which are, as nearly as practicable,  equivalent
to  the  rights of holders of Orbital Common Shares.  Holders  of
Exchangeable Shares will have the right to exchange any  of  such
shares for an equal number (subject to adjustment in the event of
certain  capital  and corporate reorganizations  of  Orbital)  of
Orbital  Common  Shares plus the Dividend Amount attributable  to
such  shares, at any time prior to the Automatic Redemption  Date
and  subject to certain Call Rights of Orbital.  The Exchangeable
Shares   will   be  automatically  exchanged  on  the   Automatic
Redemption  Date  and  upon  the occurrence  of  certain  events,
including  the liquidation, dissolution or winding-up of  Orbital
or   Acquisition  or  the  default  by  Acquisition   under   the
Exchangeable  Share Provisions.  Acquisition  has  the  right  to
accelerate  the  Automatic Redemption Date  upon  not  less  than
75  days' written notice to the holders of Exchangeable Shares at
any   time   when  there  are  outstanding  less   than   400,000
Exchangeable  Shares held by persons other than Orbital  and  its
Affiliates.

Voting Rights

Holders of Exchangeable Shares will generally not be entitled  to
vote  at  meetings of the shareholders of Acquisition (except  as
required by law).  Orbital will be the only voting shareholder of
Acquisition.  Pursuant to the Voting and Exchange Trust Agreement
holders  of  Exchangeable Shares will be entitled to  vote  along
with  holders of Orbital Common Shares at meetings of the holders
of Orbital Common Shares.

As  of  the Effective Date, Orbital, Acquisition and the  Trustee
will  enter  into  the Voting and Exchange Trust Agreement  under
which  Orbital will issue one Special Voting Share to the Trustee
for  the  benefit of the holders of the Exchangeable Shares  (the
"Beneficiaries").  The Special Voting Share will carry the number
of  votes, exercisable at any meeting at which holders of Orbital
Common  Shares  are  entitled to vote, equal  to  the  number  of
Orbital  Common  Shares  into which the outstanding  Exchangeable
Shares  not  held  by Orbital or any of its Affiliates  are  then
exchangeable.

Each  Beneficiary  on the record date for any  meeting  at  which
holders  of  Orbital Common Shares are entitled to vote  will  be
entitled to instruct the Trustee to exercise that number  of  the
votes attached to the Special Voting Share equal to the number of
votes  that the Exchangeable Shares held by such holder would  be
entitled to if exchanged for Orbital Common Shares.  The  Trustee
will exercise each vote attached to the Special Voting Share only
as  directed by the relevant Beneficiary and, in the  absence  of
instructions  from a Beneficiary, will not exercise  such  votes.
Each  Beneficiary  may, upon instructing the  Trustee,  obtain  a
proxy from the Trustee entitling the Beneficiary to vote directly
at  the relevant meeting the votes attached to the Special Voting
Share  to  which the Beneficiary is entitled.  All  rights  of  a
Beneficiary  to  exercise votes attached to  the  Special  Voting
Share  will cease upon the exchange or redemption of Exchangeable
Shares  for Orbital Common Shares or the purchase of Exchangeable
Shares by Orbital pursuant to the Call Rights.

The  Trustee  will send to the Beneficiaries the notice  of  each
meeting at which holders of Orbital Common Shares are entitled to
vote, together with the related meeting materials and a statement
as  to  the  manner  in which the Beneficiary  may  instruct  the
Trustee  to  exercise the votes attaching to the  Special  Voting
Share, in each case at the same time as Orbital sends such notice
and  materials  to  the holders of Orbital  Common  Shares.   The
Trustee  will  also  send  to  the Beneficiaries  copies  of  all
information  statements, interim and annual financial statements,
reports and other materials and at the same time as, and  to  the
extent that, such materials are sent by Orbital to the holders of
Orbital  Common  Shares.   The Trustee  will  also  send  to  the
Beneficiaries all materials sent by third parties to  holders  of
Orbital  Common Shares to the extent such materials are  provided
by  Orbital  to the Trustee, including dissident proxy  circulars
and  tender  and  exchange offer circulars, as soon  as  possible
after  such materials are first sent to holders of Orbital Common
Shares.

Dividend Rights

Under  the Exchangeable Share Provisions, holders of Exchangeable
Shares will be entitled to receive dividends as follows:

          (i)  in the case of a cash dividend declared on Orbital
          Common Shares, holders of each Exchangeable Share  will
          be  entitled to receive the Canadian dollar  equivalent
          of  the  dividend declared on one Orbital Common  Share
          (subject to adjustment);

          (ii)  in  the  case  of  a stock dividend  declared  on
          Orbital Common Shares that is payable in Orbital Common
          Shares,  holders  of each Exchangeable  Share  will  be
          entitled to receive such number of Exchangeable  Shares
          as  is equal to the number of Orbital Common Shares  to
          be  paid  as  a  dividend on one Orbital  Common  Share
          (subject to adjustment); and

          (iii)                     in  the  case of  a  dividend
          declared  on  Orbital Common Shares in  property  other
          than  cash  or Orbital Common Shares, holders  of  each
          Exchangeable  Share will be entitled  to  receive  such
          type  and  amount  of  property  as  is  the  same   or
          economically equivalent to (as determined by the  board
          of  directors  of Acquisition) the type and  amount  of
          property  declared as a dividend on one Orbital  Common
          Share (subject to adjustment).

The  number  of Orbital Common Shares referred to in  determining
the  amount of dividends to be paid on one Exchangeable Share  is
subject  to  adjustment  in  the event  of  certain  capital  and
corporate   reorganizations  so  as  to  treat  the  holders   of
Exchangeable Shares in the same manner as the holders of  Orbital
Common   Shares   were   treated  with  respect   to   any   such
reorganization.   The  record date for the determination  of  the
holders  of  Exchangeable Shares entitled to receive payment  of,
and  the  payment date for, any dividend declared on Exchangeable
Shares  shall  be the same dates as the record date  and  payment
date,  respectively,  for the corresponding dividend  on  Orbital
Common Shares.

Retraction, Redemption and Exchange Right

Subject  to  applicable  law  and  the  Call  Rights  of  Orbital
described  below,  (i) holders of Exchangeable  Shares  shall  be
entitled  at  any time upon notice to the Depositary  to  require
Acquisition to redeem any of such Exchangeable Shares,  and  (ii)
on the Automatic Redemption Date, Acquisition shall redeem all of
the  then  outstanding Exchangeable Shares held by holders  other
than  Orbital  and its Affiliates.  Pursuant to  the  Voting  and
Exchange Trust Agreement, subject to applicable law and the  Call
Rights of Orbital described below, (i) upon the occurrence of and
during  the  continuance of an Insolvency Event or if Acquisition
shall  be  in  default  of  the terms of the  Exchangeable  Share
Provisions,  a  holder of Exchangeable Shares  may  instruct  the
Trustee  to  require  Orbital to purchase  any  or  all  of  such
holder's  Exchangeable  Shares and  (ii)  in  the  event  of  the
voluntary  or involuntary liquidation, dissolution or  winding-up
of   Orbital,  the  Exchangeable  Shares  will  automatically  be
exchanged  for  Orbital  Common  Shares.   In  the  case  of  any
retraction  or redemption of Exchangeable Shares by  Acquisition,
any  purchase or exchange of Exchangeable Shares pursuant to  the
Voting   and  Exchange  Trust  Agreement,  or  any  purchase   of
Exchangeable  Shares  by  Orbital pursuant  to  its  Call  Rights
described  below, each Exchangeable Share so retracted, redeemed,
purchased  or  exchanged shall (subject to required  withholding)
entitle the holder thereof to receive (i) an amount equal to  the
market  price of an Orbital Common Share, which amount  shall  be
satisfied  in  full  by delivery to such holder  of  one  Orbital
Common  Share  (subject to adjustment) and (ii)  payment  of  the
Dividend Amount.  Upon the exercise by Orbital of any of the Call
Rights  described below, the holder of Exchangeable  Shares  with
respect  and  to  which  such Call Right  is  exercised  will  be
authorized to sell and Orbital will be obligated to purchase  the
Exchangeable  Shares with respect to which  such  Call  Right  is
exercised.

Exercise of Retraction Rights of Holders and Orbital's Retraction
Call  Rights.   Holders  of  Exchangeable  Shares  may  effect  a
retraction  by  presenting  a  certificate  or  certificates   to
Acquisition's   transfer  agent  representing   the   number   of
Exchangeable Shares the holder desires to retract, together  with
a  written request (a "Retraction Request") specifying the number
of   Exchangeable  Shares  the  holder  wishes  to  retract   and
acknowledging  the  Retraction Call Right  of  Orbital  described
below, and such other documents as may be required to effect  the
retraction of the Exchangeable Shares.  Subject to the Retraction
Call  Right of Orbital, Acquisition shall redeem the Exchangeable
Shares  so  retracted effective at the close of business  on  the
sixth Business Day after the Retraction Request is received.

Upon  receipt of a Retraction Request, the transfer  agent  shall
immediately notify Orbital of such request.  If Orbital wishes to
exercise  its  Retraction  Call Right,  it  must  so  notify  the
transfer agent by the end of the third Business Day following the
receipt  by the transfer agent of the Retraction Request that  it
intends  to  exercise its Retraction Call Right to purchase  all,
but  not  less than all, of the Exchangeable Shares submitted  by
the holder thereof for retraction.

Exercise  of  Redemption  Rights  of  Acquisition  and  Orbital's
Redemption  Call  Rights.  Subject to Orbital's  Redemption  Call
Right,  the  Exchangeable Shares shall be redeemed by Acquisition
on  the Automatic Redemption Date.  Acquisition has the right  to
accelerate  the Automatic Redemption Date upon 75  days'  written
notice  to  the holders of Exchangeable Shares at any  time  when
there are outstanding less than 400,000 Exchangeable Shares  held
by  holders other than Orbital and its Affiliates.  Orbital shall
have  the  Redemption  Call Right, notwithstanding  any  proposed
redemption of the Exchangeable Shares by Acquisition as  outlined
above, to purchase on the Automatic Redemption Date all, but  not
less than all, of the outstanding Exchangeable Shares.

Orbital  shall, at least 75 days before the Automatic  Redemption
Date,  provide Acquisition and the transfer agent with notice  of
its  exercise  of the Redemption Call Right.  The transfer  agent
shall  thereafter  give  notice to each  holder  of  Exchangeable
Shares of Orbital's exercise of the Redemption Call Right.

Exercise  of Liquidation Exchange Right of Holders and  Orbital's
Liquidation  Call  Rights.  Pursuant to the Voting  and  Exchange
Trust  Agreement, upon the occurrence and during the  continuance
of  an Insolvency Event, or if Acquisition shall be in default of
the terms of the Exchangeable Share Provisions, a Beneficiary may
instruct the Trustee to require Orbital to purchase any or all of
the Exchangeable Shares held by the Beneficiary.  Acquisition and
Orbital will give immediate written notice to the Trustee of  the
occurrence of an Insolvency Event or any event that may, with the
passage  of  time or the giving of notice, become  an  Insolvency
Event,  or if Acquisition shall be in default of the Exchangeable
Share Provisions.  As soon as practicable thereafter, the Trustee
will   notify  each Beneficiary of such event or potential  event
and will advise the Beneficiary of its rights as described above.

Under  the  Plan  of  Arrangement, Orbital will  be  granted  the
Liquidation  Call Right, in the event of and notwithstanding  the
proposed  voluntary  or involuntary liquidation,  dissolution  or
winding-up  of  Acquisition, to purchase all, but not  less  than
all, of the Exchangeable Shares then outstanding and not held  by
Orbital  or its Affiliates.  The purchase by Orbital of  all  the
outstanding  Exchangeable  Shares  upon  the  exercise  of   such
Liquidation Call Right in that event will occur on the  effective
date of the voluntary or involuntary liquidation, dissolution  or
winding  up of Acquisition.  In addition, if Acquisition  is  not
legally  able  to  redeem all Exchangeable  Shares  tendered  for
retraction by a Beneficiary because it is insolvent or to  do  so
would  render  it  insolvent, Orbital shall  be  deemed  to  have
exercised  its  Liquidation  Call Right  with  respect  to  those
Exchangeable Shares which could not be redeemed.

Exercise  of Automatic Exchange Right in the Event of Liquidation
or  Winding  Up of Orbital.  Under the Voting and Exchange  Trust
Agreement,   in  the  event  of  the  voluntary  or   involuntary
liquidation,   dissolution   or  winding-up   of   Orbital,   all
outstanding  Exchangeable Shares will automatically be  exchanged
for  Orbital Common Shares, by way of a purchase by Orbital.  The
consideration  for the full purchase price for  the  Exchangeable
Shares  subject to such automatic exchange shall be delivered  to
the  holder  thereof at least five days prior  to  a  liquidation
event.

Deduction and Remittance of Withholding Tax

Delivery  of  Orbital Common Shares to a holder  of  Exchangeable
Shares  by  Acquisition  or Orbital,  as  the  case  may  be,  as
described  under "Exercise of Retraction Rights  of  Holders  and
Orbital's Retraction Call Rights," "Exercise of Redemption Rights
of  Acquisition and Orbital's Redemption Call Rights,"  "Exercise
of   Liquidation   Exchange  Right  of  Holders   and   Orbital's
Liquidation  Call  Rights," and "Exercise of  Automatic  Exchange
Right in the Event of Liquidation or Winding Up of Orbital," will
be  made, in the case of a holder that is a resident of Canada or
a  holder  that  is  a  non-resident of  Canada  who  provides  a
certificate  issued  under section 116 of the  Canadian  Tax  Act
specifying  a  certificate limit not less than  the  fair  market
value of the Exchangeable Shares, without any reduction in number
of  Orbital  Common Shares, and will be made, in the  case  of  a
holder  who is a non-resident of Canada and who does not  provide
such  a certificate, in a reduced number of Orbital Common Shares
to  reflect  compliance  with the obligation  of  Acquisition  or
Orbital,  as the case may be, to withhold and remit on behalf  of
such  non-resident holder, tax under section 116 of the  Canadian
Tax Act.

Anti-dilution and Capital Reorganizations

In  the event of stock splits or consolidations of Orbital Common
Shares, the distribution to the holders of Orbital Common  Shares
of options, warrants or rights to acquire securities or assets of
Orbital   for  less  than  their  fair  market  value  or   other
distribution  to holders of Orbital Common Shares  of  assets  of
Orbital, unless an economically equivalent distribution  is  made
by  Acquisition to holders of the Exchangeable Shares, the number
of  Orbital  Common Shares to be received upon  exchange  of  the
Exchangeable  Shares will be adjusted so as  to  give  equivalent
economic treatment to the holders of the Exchangeable Shares.  In
the  event  of  a capital reorganization of Orbital,  holders  of
Exchangeable  Shares  shall be entitled  to  receive  after  such
capital  reorganization, the number of shares or other securities
of Orbital or of a corporation resulting, surviving or continuing
from  the  capital  reorganization that such  holder  would  have
received had he or she been a holder of Orbital Common Shares  on
the record date of the capital reorganization.

Support Agreement

The  Support Agreement obligates Orbital and Acquisition to  take
or  refrain  from  taking certain actions so as  to  ensure  that
holders of Exchangeable Shares will receive the voting, dividend,
liquidation  and exchange rights described above.  In particular,
the  Support Agreement provides that: (i) Orbital shall not,  and
shall  cause  its Affiliates not to, exercise any  voting  rights
attached  to  Exchangeable Shares owned  by  it  or  any  of  its
Affiliates  on  any matter considered at meetings of  holders  of
Exchangeable  Shares  (including any approval  sought  from  such
holders   in  respect  of  matters  arising  under  the   Support
Agreement); (ii) Orbital shall not declare or pay any dividend on
the  Orbital  Common  Shares  unless  Acquisition  simultaneously
declares and pays the same or an economically equivalent dividend
(after,  in  the case of cash dividends, appropriate  adjustments
for  currency translations) on the Exchangeable Shares; and (iii)
Orbital  and Acquisition will do all things necessary  to  ensure
that  Acquisition  will  be  able to make  all  payments  on  the
Exchangeable Shares required in the event of (a) the liquidation,
dissolution  or winding-up of Acquisition, (b) the retraction  of
Exchangeable  Shares by a holder, or (c) the  redemption  of  the
Exchangeable Shares by Acquisition.

The  Support  Agreement obligates Orbital, in the  event  that  a
tender  offer, share exchange offer, issuer bid, takeover bid  or
similar  transaction with respect to Orbital  Common  Shares  (an
"Offer")  is proposed or recommended by Orbital, its shareholders
or  board of directors, or is otherwise effected with the consent
or   approval  of  Orbital's  board  of  directors,  to  use  all
commercially  reasonable efforts to take  such  actions  in  good
faith  as are necessary or desirable to enable and permit holders
of  Exchangeable Shares to participate in such Offer to the  same
extent and on an economically equivalent basis as the holders  of
the Orbital Common Shares, without discrimination.

The  Support Agreement also provides that Orbital will  take  all
actions necessary or desirable to cause all Orbital Common Shares
issued  and  delivered pursuant to the Combination Agreement  and
related  agreements to be freely tradeable by the holders thereof
(other  than any restrictions on transfer by reason of  a  holder
being a "control person" of Orbital for purposes of Canadian  law
or  an  "affiliate"  of  Orbital for purposes  of  United  States
securities  laws).   In  addition, Orbital  will  take  all  such
actions necessary to cause all such Orbital Common Shares  to  be
listed  or quoted for trading on all stock exchanges or quotation
systems  on  which  outstanding Orbital Common  Shares  are  then
listed  or  quoted  for trading.  The Orbital Common  Shares  are
currently  quoted  for  trading on  the  NASDAQ  and  it  is  not
anticipated  that such shares will be listed on any  other  stock
exchange or trading system.

The  Support  Agreement  also provides that,  without  the  prior
approval  of  Acquisition  and the holders  of  the  Exchangeable
Shares,  Orbital  will not distribute additional  Orbital  Common
Shares  or  rights  to  subscribe therefor  or  other  assets  or
evidences of indebtedness to all or substantially all holders  of
Orbital  Common Shares nor change the Orbital Common  Shares  nor
effect  any  reorganization  or other transaction  affecting  the
Orbital  Common  Shares,  unless  the  same  or  an  economically
equivalent distribution on, or change to, the Exchangeable Shares
(or in the rights of the holders thereof) is made simultaneously.
The  board  of directors of Acquisition is conclusively empowered
to determine in good faith and in its sole discretion whether any
corresponding  distribution  on or  change  to  the  Exchangeable
Shares  is the same as or economically equivalent to any proposed
distribution on or change to the Orbital Common Shares.

The  Support Agreement also provides that so long as there remain
outstanding any Exchangeable Shares not owned by Orbital  or  any
of  its  Affiliates,  Orbital will remain the  beneficial  owner,
directly or indirectly, of all outstanding shares of Acquisition,
other than Exchangeable Shares and the Class B Preferred Shares.

With the exception of administrative changes for the purposes  of
adding  covenants  for  the protection  of  the  holders  of  the
Exchangeable  Shares,  making  certain  necessary  amendments  or
curing ambiguities or clerical errors (in each case provided that
the  board of directors of each of Orbital and Acquisition is  of
the  opinion  that  such amendments are not  prejudicial  to  the
interests of the holders of the Exchangeable Shares), the Support
Agreement may not be amended without the approval of the  holders
of the Exchangeable Shares.

Market for Orbital Common Shares and Exchangeable Shares

The   Orbital   Common  Shares  issued  upon  exchange   of   the
Exchangeable  Shares  will  be freely tradeable  by  the  holders
thereof (other than any restrictions on transfer by reason  of  a
holder  being  a  "control  person" of Orbital  for  purposes  of
Canadian law or an "affiliate" of Orbital for purposes of  United
States  securities laws) and will be quoted for  trading  on  the
NASDAQ.  Although the transfer of Exchangeable Shares, subject to
receiving orders from applicable securities regulators, will  not
be  restricted under applicable securities laws, subject  to  the
above-noted  exceptions,  the Exchangeable  Shares  will  not  be
listed  on any stock exchange and MDA does not expect there  will
be  any market for the Exchangeable Shares.  See "The Arrangement
and  the Combination Agreement - Stock Exchange Listings" and  "-
Resale  of Exchangeable Shares and Orbital Common Shares Received
in the Arrangement."

The Combination Agreement

The  following  paragraphs summarize the material  terms  of  the
Combination   Agreement.    MDA   Shareholders   and   MDA   1988
Optionholders are urged to read the Combination Agreement in  its
entirety  for  a  more  complete description  of  the  terms  and
conditions  of the obligations of the parties in respect  of  the
Plan of Arrangement.

Actions to be Taken Prior to the Effective Time

Pursuant  to  the  Combination Agreement,  MDA,  Acquisition  and
Orbital  have agreed to perform certain obligations.  MDA  agreed
to  call all options to purchase MDA Common Shares presently held
by  shareholders of Earth Observation Sciences Ltd., a subsidiary
of  MDA.  Orbital and Acquisition covenanted to obtain exemptions
from registration or file a registration statement under the 1933
Securities Act qualifying the issue of the Orbital Common Shares,
and to obtain all orders necessary from securities regulators  in
Canada  so as to qualify the issuance and permit the free trading
of  the Exchangeable Shares and the Orbital Common Shares in  the
U.S.  and Canada subject only to restrictions on holders who  are
"control  persons"  in Canada or "affiliates"  in  the  U.S.   In
addition,  Orbital, Acquisition and MDA have agreed to  cooperate
in  the  preparation of this Proxy Circular, to take all  actions
necessary  to  qualify the issue of the Exchangeable  Shares  and
Orbital Common Shares under appropriate securities legislation in
order  to  permit the issue and free trading thereof, subject  to
the  above-noted exceptions, to call the Special Meeting, and  to
obtain the necessary court orders to permit the Arrangement to be
completed.

Business of MDA Pending the Arrangement

Pending  consummation of the Arrangement, and except as otherwise
consented  to  or approved in advance by Orbital in writing,  MDA
has  agreed  that  MDA  and its subsidiaries  will,  among  other
things,  operate  their  respective businesses  in  the  ordinary
course  of  business  consistent  with  past  practices  and  use
reasonable  efforts to preserve intact their respective  business
organizations;  not authorize for issuance or issue  any  capital
stock,  rights,  warrants,  options  or  convertible  or  similar
securities,  subject  to certain exceptions,  or  repurchase  any
capital   stock;  not  take  any  action  that  would  materially
adversely  affect  the ability of MDA or Orbital  to  obtain  the
approvals required to effect the transactions contemplated by the
Combination  Agreement;  and  not  take  any  action  that  would
materially affect the ability of MDA to perform its covenants and
agreements under the Combination Agreement.

Solicitation of Alternate Transactions

The  Combination Agreement provides that except  as  required  by
law,  MDA  will not, directly or indirectly: solicit,  encourage,
initiate  or  participate  in  any  negotiations,  inquiries   or
discussions with respect to any offer or proposal to acquire  all
or  any  significant part of MDA's business,  assets  or  capital
shares    whether    by   arrangement,   amalgamation,    merger,
consolidation,  other business combination, purchase  of  assets,
tender  or  exchange  offer or otherwise  (each  an  "Acquisition
Transaction");  or  disclose  any  information  not   customarily
disclosed  to any person concerning MDA's business or  properties
or afford to any person or entity access to its properties, books
or  records, except in the ordinary course of business consistent
with  past  practice  and  except  as  required  pursuant  to   a
governmental request for information; enter into or  execute  any
agreement  relating  to  an  Acquisition  Transaction,  plan   of
reorganization, or other agreement calling for the sale of all or
any  significant part of its business and properties; or make  or
authorize  any  public statement, recommendation or  solicitation
with  respect  to  any Acquisition Transaction or  any  offer  or
proposal  relating to an Acquisition Transaction other than  with
respect to the Arrangement.

The Combination Agreement provides that nothing contained therein
limits  the  power  of the MDA Board to withdraw  or  modify  any
recommendation  with  respect to the Plan  of  Arrangement  if  a
material  adverse  change occurs in the business  or  affairs  of
Orbital or in any of the information provided by Orbital on which
the   MDA  Board  has  based  any  recommendation  regarding  the
Arrangement.   If  any person proposes an unsolicited  bona  fide
acquisition  transaction  that in  the  opinion  of  MDA's  Board
(having  consulted its financial advisors) offers terms that  may
be  more favourable to the MDA Shareholders than pursuant to  the
Combination Agreement or the Plan of Arrangement, MDA shall  have
seven  business  days to consider such proposal, following  which
time the MDA Board may withdraw or modify any recommendation with
respect to the Plan of Arrangement only if to do so would, in the
opinion  of  the  MDA Board (having consulted  outside  counsel),
acting  reasonably,  be  a  proper  exercise  of  the  directors'
fiduciary duty.  Depending on the timing of the unsolicited  bona
fide  Acquisition  Transaction,  the  MDA  Board  may  support  a
proposal to postpone or adjourn the Special Meeting for not  more
than  10  business  days.   The Combination  Agreement  generally
requires  MDA  to  inform Orbital of any  such  bona  fide  offer
received by it or any related request for information.

In  addition,  MDA may terminate the Combination Agreement  if  a
bona   fide   offer  for  an  Acquisition  Transaction  providing
consideration for MDA Common Shares having a fair market value of
at least US$5.95 per share (based on prevailing currency exchange
rates  at  the date of the offer) is received, in which case  MDA
has agreed to pay Orbital a fee of US$750,000 upon completion  of
the transaction that gave rise to such termination.

Conditions to the Arrangement

Consummation of the Arrangement is subject to the satisfaction of
various conditions for the benefit of each of MDA or Orbital  and
both  of  them.   Conditions precedent for  the  benefit  of  MDA
include:  (i)  Orbital's  and Acquisition's  representations  and
warranties being correct on the Effective Date and Orbital having
performed  its covenants under the Combination Agreement  in  all
material respects; (ii) MDA receiving an opinion from counsel  to
Orbital in form and substance reasonably satisfactory to MDA; and
(iii)  the  Average Closing Price being equal to or greater  than
US$12.775.   Conditions  precedent for  the  benefit  of  Orbital
include:  (i) MDA's representations and warranties being  correct
on  the  Effective  Date and MDA having performed  its  covenants
under  the  Combination Agreement in all material respects;  (ii)
Orbital  having received an opinion of MDA's counsel in form  and
substance  reasonably satisfactory to Orbital; (iii) MDA's  Board
having  waived  the  applicable  provisions  of  the  Shareholder
Protection  Rights Plan; (iv) all necessary Affiliate  Agreements
having  been  executed;  (v) MDA having entered  into  Employment
Agreements  and Change of Control Agreements with  the  Chairman,
the  President  and each area general manager, as required,  (vi)
Dissenting MDA Shareholders and Dissenting MDA 1988 Optionholders
entitled  to  receive in the aggregate no more than  10%  of  the
aggregate number of Orbital Common Shares and the Orbital  Common
Shares  reserved  for issuance upon exercise of  the  Replacement
Options  to be issued pursuant to the Plan of Arrangement;  (vii)
Orbital having received a letter from its independent auditors to
the  effect  that  the  transaction meets  the  requirements  for
pooling  of  interests  accounting under U.S.  GAAP;  (viii)  all
required  third-party  consents  and  waivers  relating  to   the
Arrangement  having been obtained; and (ix) the  Average  Closing
Price being equal to or less than US$25.00.

In  addition,  for  the  benefit of both  MDA  and  Orbital,  the
following  conditions  must  be met:  (i)  the  approval  of  MDA
Shareholders  and  MDA 1988 Optionholders as required  under  the
Interim Order shall have been obtained and the Final Order  shall
have  been  issued by the Court; (ii) there shall be no temporary
restraining order, preliminary or permanent injunction  or  other
legal restraints or prohibitions, statutes, rules, regulations or
orders preventing consummation of the Arrangement; and (iii)  the
approval  for  quotation, subject to notice of issuance,  on  the
NASDAQ  of  the Orbital Common Shares to be issued in  connection
with the Arrangement shall have been obtained.

The parties entitled to the benefit of a particular condition may
waive compliance thereof.

Termination and Amendment

The  Combination Agreement may be terminated and the  Arrangement
may  be  abandoned  prior to the Effective  Date  notwithstanding
approval  by  the  MDA  Shareholders and MDA 1988  Optionholders,
under  the  circumstances specified therein,  including:  (i)  by
mutual consent of Orbital and MDA; (ii) by either Orbital or MDA,
if   the   Arrangement  shall  not  have  been   consummated   by
December 31, 1995 and if the terminating party has not caused the
failure  of the Arrangement to be consummated by its own  failure
to fulfil any of its obligations under the Combination Agreement;
(iii)  by either Orbital or MDA, if the MDA Shareholders  or  the
MDA   1988   Optionholders  fail  to  approve   the   Arrangement
Resolution; (iv) by either Orbital or MDA if there is a  material
breach  on  the  part of the other party in a  representation  or
warranty  or  covenant or agreement contained in the  Combination
Agreement  which is not cured within 10 days of  notice;  (v)  by
Orbital,   if  the  MDA  Board  has  withdrawn  or  changed   its
recommendation on the Arrangement in a manner adverse to Orbital,
or  shall  fail to affirm such support at Orbital's request;  and
(vi)  by  MDA, if it has received a bona fide offer to consummate
an Acquisition Transaction for consideration per MDA Common Share
having  a  fair  market  value  of at  least  US$5.95  (based  on
prevailing currency exchange rates on the date of such offer).

The  Combination  Agreement may be amended  by  an  agreement  in
writing  among  the  parties thereto at any  time  prior  to  the
Effective  Date; provided, however, that, after approval  of  the
Arrangement  by  the MDA Shareholders and MDA 1988 Optionholders,
no  amendment may be made which by law requires further  approval
of  such  shareholders  or optionholders,  without  such  further
approval.

Fees, Expenses and Indemnification

Except  as  described herein, all fees and expenses  incurred  in
connection  with  the Combination Agreement and the  transactions
contemplated  thereby  will be paid by the party  incurring  such
expenses, whether or not the Arrangement is consummated.

MDA  has  agreed  to  pay  Orbital a fee  of  US$750,000  if  the
Combination  Agreement  is terminated  by  MDA  because  MDA  has
received  a  bona  fide offer of an Acquisition  Transaction  for
consideration per MDA Common Share having a fair market value  of
at  least US$5.95 (based on prevailing currency exchange rates on
the  date of such offer), and such fee is payable only when  such
Acquisition Transaction is completed.

If  the  Combination Agreement is terminated as  a  result  of  a
breach by one of the parties, the party who has breached will pay
the actual out-of-pocket expenses of the others.

The  Combination  Agreement  provides  that  the  indemnification
provisions set forth in MDA's by-laws may not be modified for six
years  from the Effective Date in any manner that would adversely
affect  the rights thereunder of individuals who at the Effective
Date  were  MDA's directors or officers, unless such modification
is  required  by  law,  and requires Orbital  or  Acquisition  to
continue  in  effect with respect to any claims  arising  out  of
conduct  prior  to  the  Effective Date directors  and  officers'
insurance policies providing coverage of substantially  the  same
scope as is currently maintained by MDA; provided, however,  that
Orbital  may  amend, repeal or modify such by-law  provisions  or
cause  the  directors  and  officer's insurance  policies  to  be
modified or cancelled if it indemnifies such parties against  all
expenses  (including  attorney's  fees),  judgments,  fines   and
amounts  paid in settlement actually and reasonably  incurred  by
reason of the fact that such person was a director or officer  of
MDA,  in  connection  with any threatened, pending  or  completed
action,    suit   or   proceeding,   whether   civil,   criminal,
administrative or investigative, provided that such expenses were
incurred by such person in connection with such action,  suit  or
proceeding and provided that such person acted in good faith  and
in  a  manner he reasonably believed to be in or not  opposed  to
MDA's  best interests and had no reasonable cause to believe  his
conduct was unlawful.

MDA has agreed that, if the Arrangement is not effective, it will
indemnify each present and former director or officer of  MDA  or
any   of   its   subsidiaries  (collectively,  the   "Indemnified
Parties"),  to the fullest extent permitted under applicable  law
or  under  its by-laws, against any costs or expenses  (including
attorneys'  fees),  judgments, fines,  losses,  claims,  damages,
liabilities and amounts paid in settlement in connection with any
claim,  action, suit, proceeding or investigation, whether civil,
criminal,  administrative or investigative,  arising  out  of  or
pertaining  to any action or omission occurring while  they  were
directors, officers or employees for six years after the proposed
Effective Date.

Confidentiality Agreement

Each of Orbital and MDA has agreed to keep confidential, pursuant
to   a   confidentiality  agreement  dated  June  23,  1995  (the
"Confidentiality Agreement"), proprietary information provided by
the  other  party.  The Confidentiality Agreement contains  terms
restricting  the  disclosure and use of confidential  information
exchanged  between the two parties in evaluating the  Arrangement
and otherwise.

Agreements of MDA Affiliates

Rule 145 promulgated under the 1933 Securities Act regulates  the
disposition in the U.S. of securities by "affiliates" of  MDA  in
connection  with  the  Arrangement.  Affiliates  of  MDA,  as  so
defined, have delivered to Orbital executed Affiliate Agreements.
Under  such  Affiliate Agreements, each affiliate agrees  not  to
sell,  transfer or otherwise dispose of Orbital Common Shares  or
Exchangeable  Shares issued to the affiliate in  the  Arrangement
unless  such  sale, transfer or other disposition  (i)  has  been
registered  under  the  1933 Securities  Act,  (ii)  is  made  in
compliance  with  the requirements of Rule  145  under  the  1933
Securities  Act,  or  (iii) in the opinion of counsel  reasonably
acceptable  to  Orbital,  is otherwise exempt  from  registration
under  the  1933 Securities Act.  To comply with the requirements
of  pooling  of  interests accounting treatment,  each  Affiliate
Agreement  also restricts the sales of such shares prior  to  and
following the Arrangement until the publication and dissemination
by Orbital of consolidated financial results that include results
of combined operations of MDA and Orbital for at least 30 days on
a consolidated basis following the Effective Date.  The Affiliate
Agreements terminate if the Combination Agreement is terminated.

Court Approval and Completion of the Arrangement

Under the CBCA and pursuant to the Interim Order, the Arrangement
requires  Court approval, after approval of the MDA  Shareholders
and  MDA  1988  Optionholders has been obtained.   Prior  to  the
mailing  of  this Proxy Circular, MDA obtained the Interim  Order
providing  for  the calling, holding and conduct of  the  Special
Meeting  and  other procedural matters.  A copy  of  the  Interim
Order  is  attached as Appendix "D" to this Proxy Circular.   The
Notice of Application for the Final Order appears as Appendix "E"
to this Proxy Circular.

Subject to the approval of the Arrangement Resolution by the  MDA
Shareholders  and  the  MDA 1988 Optionholders,  the  hearing  in
respect  of  the  Final  Order  is scheduled  to  take  place  on
November  16,  1995  at  10:00 a.m. (Vancouver  time).   At  that
hearing, any MDA Shareholder, any MDA 1988 Optionholder,  or  any
other  interested  party  who wishes  to  participate  or  to  be
represented  or  to  present evidence or  arguments  may  do  so,
subject  to  filing  a notice of appearance with  the  Court  and
serving  such  notice of appearance upon MDA's solicitors  within
the  time as set forth in the Notice of Application for the Final
Order,  and  upon all other parties who have filed  a  notice  of
appearance, and satisfying other requirements as provided in  the
Interim  Order.   At the final hearing the Court  will  consider,
among  other  things,  the  fairness and  reasonableness  of  the
Arrangement.

Assuming  that  the  Final  Order  is  granted,  and  the   other
conditions to the Combination Agreement are satisfied, or  waived
by the party or parties entitled to do so, it is anticipated that
the  following will occur substantially simultaneously:  articles
of  arrangement  will be filed with the Director appointed  under
the  CBCA  to  give effect to the Arrangement;  and  the  Support
Agreement,  the  Voting  and Exchange  Trust  Agreement  and  the
various  other  documents  necessary  to  give  effect   to   the
Arrangement   and   other  transactions   contemplated   by   the
Combination Agreement will be executed and delivered.

Subject  to the foregoing, it is anticipated that the Arrangement
will be completed not later than November 30, 1995.

Accounting Treatment

The Arrangement is expected to be treated by Orbital as a pooling
of  interests  for  accounting purposes under  U.S.  GAAP.   This
accounting method permits the recorded assets and liabilities  of
both  Orbital  and  MDA to be carried forward on  a  consolidated
basis  by  Orbital,  after giving effect to the  Arrangement,  at
their  recorded historical amounts.  No recognition  of  goodwill
will be required as a result of the Arrangement and consequently,
there  will  be no amortization of goodwill from the  Arrangement
reflected in Orbital's future financial periods.

It   is  a  condition  to  Orbital's  obligation  to  effect  the
Arrangement  that  Orbital  receive an  opinion  from  KPMG  Peat
Marwick LLP, independent auditors of Orbital, to the effect  that
pooling  of  interests accounting treatment for  the  Arrangement
under  U.S.  GAAP is appropriate.  In the event  holders  of  MDA
Common  Shares and MDA 1988 Options in the aggregate entitled  to
receive greater than 10% of the sum of the Orbital Common  Shares
issuable  pursuant  to the Plan of Arrangement  and  the  Orbital
Common  Shares  reserved  for  issuance  upon  exercise  of   the
Replacement  Options,  shall properly  exercise  their  right  to
dissent,  the  Arrangement may not qualify  for  treatment  as  a
pooling of interests under applicable accounting rules.

Stock Exchange Listings

Exchangeable Shares

The  Exchangeable Shares will not be listed or posted for trading
on  any  stock exchange.  MDA does not expect there will  be  any
market for the Exchangeable Shares.

Orbital Common Shares

NASDAQ  has  conditionally approved inclusion of  the  additional
Orbital  Common Shares issuable upon exchange of the Exchangeable
Shares  and  the  Replacement  Options  for  quotation.   Orbital
expects that NASDAQ will grant final approval for such inclusion.

Eligibility for Investment in Canada

Exchangeable Shares

The  Exchangeable  Shares (including the Voting  Rights  and  the
Exchange Right) (a) will be "foreign property" under the Canadian
Tax   Act  for  trusts  governed  by  registered  pension  plans,
registered retirement savings plans, registered retirement income
funds and deferred profit sharing plans or for certain other tax-
exempt  persons, and (b) will not be qualified investments  under
the Canadian Tax Act for trusts governed by registered retirement
savings  plans, registered retirement income funds  and  deferred
profit sharing plans.

Voting Rights and Exchange Right

The  Voting  Rights and the Exchange Right will not be  qualified
investments and will be "foreign property" under the Canadian Tax
Act.

Orbital Common Shares

The Orbital Common Shares will be qualified investments under the
Canadian  Tax  Act  for trusts governed by registered  retirement
savings  plans, registered retirement income funds  and  deferred
profit sharing plans so long as such shares remain quoted on  the
NASDAQ  or another prescribed stock exchange.  The Orbital Common
Shares will be "foreign property" under the Canadian Tax Act.

Resale  of Exchangeable Shares and Orbital Common Shares Received
in the Arrangement

Canada

Orbital,  Acquisition and MDA have applied  for  rulings  of  the
British  Columbia  Securities Commission  ("BCSC"),  the  Ontario
Securities  Commission (the "OSC") and the securities commissions
of  certain other jurisdictions in Canada in which holders of MDA
Common  Shares reside, exempting any trade in Exchangeable Shares
or  in  Orbital Common Shares made in connection with or pursuant
to   the   Arrangement   from  the  applicable   prospectus   and
registration requirements of the securities legislation  of  such
jurisdictions.  If granted, these rulings would permit holders of
Exchangeable Shares who are not "control persons" of  Acquisition
to  sell  such securities in British Columbia, Ontario  and  such
other  jurisdictions, without being required to file a prospectus
in  respect thereof, provided that no unusual effort is  made  to
prepare  the market for any such sale or to create a  demand  for
such  securities and no extraordinary commission or consideration
is  paid  in respect thereof.  However, if such resale occurs  in
British  Columbia by a seller that is an insider of  Acquisition,
then,   as  a  further  condition  to  permitting  such   resale,
Acquisition  must  not be in default of any  requirement  of  the
Securities Act (British Columbia) or the regulations thereunder.

If   granted,  these  rulings  would  permit  residents  of  such
jurisdictions  who  are recipients of Orbital  Common  Shares  to
resell  such  securities provided that such resales are  executed
through  the facilities of a stock exchange or market outside  of
British Columbia, Ontario or such other jurisdiction, as the case
may be, and such resales are made in accordance with the rules of
the  stock exchange or market upon which such trades are made and
in  accordance with all laws applicable to such stock exchange or
market.

MDA,  Acquisition and Orbital have also applied for orders  under
the   Securities  Act  (British  Columbia),  the  Securities  Act
(Ontario)  and  the applicable securities laws of  certain  other
jurisdictions  in  Canada in which holders of MDA  Common  Shares
reside  to  permit all issuances of securities to be carried  out
pursuant to the Exchangeable Share Provisions and the Voting  and
Exchange  Trust  Agreement  to be exempt  from  the  registration
requirements of such Acts and applicable securities  laws.   Upon
completion  of the Arrangement, Acquisition will be  a  reporting
issuer under the Securities Act (British Columbia), but MDA  will
cease to be a reporting issuer under the Securities Act (Ontario)
and  the  applicable securities laws of the other  jurisdictions.
In  addition,  the  ruling  requested from  the  BCSC  would,  if
granted, exempt Acquisition from certain statutory financial  and
other  reporting requirements under the Securities  Act  (British
Columbia).   As a condition to granting the ruling  as  described
above,  Orbital will undertake, among other things, to file  with
the  appropriate  securities commissions  of  such  jurisdictions
copies  of all documents filed by it with the SEC and to send  to
all  holders of Exchangeable Shares resident in British  Columbia
and  such  other jurisdictions all disclosure materials that  are
sent  to  holders  of  Orbital Common Shares, including,  without
limitation,   copies  of  its  annual  reports  and   all   proxy
solicitation materials and, upon request, copies of its quarterly
reports.

United States

The  offer  and sale of the Exchangeable Shares, the  Replacement
Options  and  the Orbital Common Shares to be issued in  exchange
therefor  (collectively the "New Shares") will not be  registered
under  the  1933  Securities Act.  The Exchangeable  Shares,  the
Replacement  Options and the Orbital Common Shares issuable  upon
exchange of the Exchangeable Shares will be issued in reliance on
section  3(a)(10) of the 1933 Securities Act, which exempts  from
registration  under the 1933 Securities Act securities  that  are
issued  in  exchange for other outstanding securities  where  the
terms  and conditions of the issuance have been approved  by  any
court  expressly  authorized by law  to  grant  approval  to  the
proposed issuance, after a hearing upon the fairness of the terms
and  conditions of the issuance at which all persons to whom such
securities will be issued have the right to appear.  Orbital  has
been orally advised that it will be issued a letter from the  SEC
confirming  that  the  staff of the SEC will  not  recommend  any
enforcement action to the SEC if Acquisition, in reliance on  the
exemption  provided by section 3(a)(10), issues the  Exchangeable
Shares,  the  Replacement Options, and the Orbital Common  Shares
issuable in exchange for the Exchangeable Shares.

All  Orbital  Common Shares received by MDA Shareholders  in  the
Arrangement  will be freely transferable under the United  States
federal  securities  laws,  except  that  Orbital  Common  Shares
received  by persons who are deemed to be "affiliates"  (as  such
term is defined under the 1933 Securities Act) of MDA at the time
of  the  transaction  may be resold by such  affiliates  only  in
transactions    permitted   by   the   resale    provisions    of
Rule  145(d)(1), (2) or (3) promulgated under the 1933 Securities
Act  (or  Rule  145(d)(1) alone in the case of such  persons  who
become   affiliates  of  Orbital  upon  the  completion  of   the
Arrangement), or as otherwise permitted under the 1933 Securities
Act.  Rule 145(d)(1) generally provides that the "affiliates"  of
the acquired company may not sell securities of the issuer unless
pursuant  to  an  effective  registration  statement  or   unless
pursuant  to  the volume, current public information,  manner  of
sale  and  timing limitations of Rule 144 (excluding the  holding
period  requirements  of Rule 144).  These limitations  generally
require  that  (a) any sales made by the affiliate in  any  three
month  period not exceed the greater of (i) 1% of the outstanding
shares  of the issuer or (ii) the average weekly reported  volume
of  trading  in such shares on all national securities  exchanges
and/or  reported  through  an automated  quotation  system  of  a
registered securities association over a four-week period and (b)
that  such  sales  be  made in unsolicited, open  market  "broker
transactions"  or in transactions directly with a  market  maker.
Rules  145(d)(2)  and (3) generally provide  that  the  foregoing
limitations lapse for nonaffiliates of the issuer after a  period
of  two  or three years has elapsed since the date the securities
were  acquired from the issuer, respectively.  The average weekly
reported  volume of the Orbital Common Shares for the four  weeks
ending  September  29,  1995 was 848,250 Orbital  Common  Shares.
Persons who may be deemed to be affiliates of an issuer generally
include  individuals  or  entities that  directly  or  indirectly
control,  are  controlled by, or are under common  control  with,
such  issuer  and may include certain officers and  directors  of
such  issuer  as well as principal stockholders of  such  issuer.
See  "The  Arrangement and the Combination Agreement - Agreements
of MDA Affiliates."

Procedures for Exchange of Share Certificates by MDA Shareholders

At  or  promptly  after  the Effective  Time,  Acquisition  shall
deposit  with the Depositary, for the benefit of the  holders  of
MDA  Common  Shares and the holders of shares of  the  Qualifying
Holdcos   exchanged   pursuant  to  the  Plan   of   Arrangement,
certificates   representing   the  Exchangeable   Shares   issued
therefor.

A  Letter of Transmittal is enclosed with this Proxy Circular for
use   by   MDA   Shareholders  for  transmittal  of  certificates
representing MDA Common Shares.  Additional copies of the  Letter
of Transmittal may be obtained from the Depositary.  A subsequent
letter  of  transmittal may also be forwarded to MDA Shareholders
following the Effective Date.  The details of the procedures  for
exchange of certificates representing MDA Common Shares  and  the
deposit  of  such  certificates  with  the  Depositary  and   the
addresses  of  the office of the Depositary are set  out  in  the
Letter of Transmittal.

The    procedures   for   receiving   certificates   representing
Exchangeable Shares and/or Orbital Common Shares are as follows:

Return to Depositary of Letter of Transmittal

A  properly  completed Letter of Transmittal, or  any  subsequent
letter  of  transmittal, is to be forwarded to the Depositary  at
the office as set forth therein, together with the certificate(s)
representing the MDA Common Shares.  As soon as practicable after
the  surrender of certificates representing MDA Common Shares and
after   the   Effective   Date,  the  Depositary   will   deliver
certificates  representing  Exchangeable  Shares  and/or  Orbital
Common  Shares in accordance with the instructions set  forth  in
the   Letter   of  Transmittal  or  any  subsequent   letter   of
transmittal, as the case may be.

Election to Immediately Exchange Exchangeable Shares for  Orbital
Common Shares

MDA   Shareholders  who  wish  to  immediately   exchange   their
Exchangeable  Shares for Orbital Common Shares must complete  the
Letter  of Transmittal and indicate their election to immediately
exchange the Exchangeable Shares they are entitled to receive for
Orbital Common Shares in the election section therein.  If only a
part  of  such  holder's MDA Common Shares are to be  immediately
exchanged  for  Orbital Common Shares, the MDA Shareholder  shall
indicate  the  number of Exchangeable Shares to be so  exchanged.
If any MDA Shareholder elects to immediately exchange all or part
of  his  or her Exchangeable Shares for Orbital Common Shares,  a
certificate for the full number of Exchangeable Shares  to  which
that   holder  would  have  been  entitled  under  the  Plan   of
Arrangement shall be issued, the Depositary shall, by the  Letter
of Transmittal, be appointed an attorney to effect the retraction
on  behalf of the holder and the holder will receive certificates
representing Orbital Common Shares.  MDA has been advised that in
the  event of the retraction contemplated by the exercise of this
election,  Orbital intends to exercise its Redemption Call  Right
and purchase such Exchangeable Shares.  Orbital or Acquisition as
the  case may be, will require holders of Exchangeable Shares who
are  not  residents  of  Canada and who elect  to  retract  their
Exchangeable  Shares as described above to obtain  a  certificate
from  Revenue Canada pursuant to section 116 of the Canadian  Tax
Act,  specifying a certificate limit no less than the fair market
value  of  the  Orbital  Common  Shares  immediately  before  the
exchange  or redemption, as the case may be, and to deliver  such
certificate to Orbital or Acquisition.  See "The Arrangement  and
the Combination Agreement - Description of Exchangeable Shares  -
Deduction and Remittance of Withholding Tax."

Fractional Shares

No  certificates  or  scrip representing fractional  Exchangeable
Shares  or Orbital Common Shares will be issued.  In lieu of  any
such  fractional interests, each MDA Shareholder  entitled  to  a
fractional  interest  in Exchangeable Shares  or  Orbital  Common
Shares in consequence of the Arrangement or upon exchange of  the
Exchangeable  Shares for Orbital Common Shares  will  receive  an
equivalent  amount in cash (rounded to the nearest  whole  cent),
without  interest, from Acquisition equal to the Canadian  Dollar
Equivalent  (as defined in the Exchangeable Share Provisions)  of
the  product of such fraction, multiplied by the Average  Closing
Price.

Failure to Deposit Certificates Representing MDA Common Shares

Pending  the surrender of certificates formerly representing  MDA
Common  Shares, such certificates will, subject to the provisions
in  the  following sentence, be deemed to represent the right  to
receive  upon  such  surrender,  a certificate  representing  the
appropriate number of Exchangeable Shares (based on the  Exchange
Ratio),  any  cash  payment in lieu of a fractional  Exchangeable
Share,   and  any  Dividend  Amount.   Any  certificate  formerly
representing  MDA  Common  Shares not deposited  with  all  other
necessary documents on or prior to the sixth anniversary  of  the
Effective  Date shall cease to represent a claim or  interest  of
any  kind  or  nature  as  a shareholder  of  MDA,  the  relevant
Qualifying  Holdco or Acquisition, as the case may be.   On  such
date,  the  Exchangeable Shares to which  the  former  registered
holder  of  such  undeposited certificate was entitled  shall  be
deemed to have been surrendered to Acquisition together with  all
dividends,  distributions  and interests  held  for  such  former
registered holder.

Confirmation of Replacement Options

As  soon  as  practicable after the Effective Date, Orbital  will
forward  to each holder of a MDA Option, except a Dissenting  MDA
1988   Optionholder,  confirmation  of  the  Replacement  Option,
setting forth the number of Orbital Common Shares such holder  is
entitled to and the exercise price therefor.


INCOME TAX CONSIDERATIONS TO MDA SHAREHOLDERS AND OPTIONHOLDERS

Canadian Federal Income Tax Considerations

In  the opinion of Farris, Vaughan, Wills and Murphy, counsel for
MDA, the following is a summary of the principal Canadian federal
income  tax  considerations  generally  applicable  to  (i)   MDA
Shareholders  who,  for  purposes of the Canadian  Tax  Act,  are
residents  of  Canada, hold their MDA Common  Shares  as  capital
property  and  deal  at  arm's length with MDA,  Acquisition  and
Orbital,  (ii) MDA Shareholders who, for purposes of the Canadian
Tax  Act, have not been and will not be resident in Canada at any
time  while  they  have  held MDA Common Shares  or  Exchangeable
Shares,  and  deal  at  arm's length with  MDA,  Acquisition  and
Orbital, and (iii) MDA 1988 Optionholders.

This  summary is based on the current provisions of the  Canadian
Tax  Act,  all specific proposals to amend the Canadian  Tax  Act
publicly  announced by the Minister of Finance prior to the  date
hereof, and counsel's understanding of the current administrative
practices  of  Revenue  Canada. Except for  the  foregoing,  this
summary  does not take into account or anticipate any changes  in
law,  whether by legislative, administrative or judicial decision
or  action, nor does it take into account provincial, territorial
or  foreign income tax legislation or considerations,  which  may
differ  from  the  federal  income tax  considerations  described
herein.

WHILE  THIS SUMMARY IS INTENDED TO ADDRESS ALL PRINCIPAL CANADIAN
FEDERAL INCOME TAX CONSIDERATIONS, IT IS OF A GENERAL NATURE ONLY
AND  IS  NOT  INTENDED TO BE, NOR SHOULD IT BE CONSTRUED  TO  BE,
LEGAL OR TAX ADVICE TO ANY PARTICULAR MDA SHAREHOLDER OR MDA 1988
OPTIONHOLDER.  THEREFORE, SUCH HOLDERS SHOULD CONSULT  THEIR  OWN
TAX ADVISORS WITH RESPECT TO THEIR PARTICULAR CIRCUMSTANCES.   NO
ADVANCE  INCOME  TAX  RULING HAS BEEN OR WILL  BE  OBTAINED  FROM
REVENUE  CANADA TO CONFIRM THE TAX CONSEQUENCES  OF  ANY  OF  THE
TRANSACTIONS DESCRIBED HEREIN.

Holders of MDA Common Shares Resident in Canada

Exchange of MDA Common Shares for Exchangeable Shares.  A  holder
of MDA Common Shares who receives Exchangeable Shares in exchange
for  MDA  Common  Shares  pursuant to  the  Plan  of  Arrangement
(provided such holder is not considered to receive Voting  Rights
or  any  Exchange Right as partial consideration for  MDA  Common
Shares (see below)) will, unless such holder of MDA Common Shares
includes  any  portion  of  the  capital  gain  or  capital  loss
otherwise  determined in respect of the disposition of  such  MDA
Common  Shares in the holder's income tax return for the taxation
year  in  which  the exchange occurs, be deemed pursuant  to  the
"automatic"  rollover provisions of section 85.1 of the  Canadian
Tax  Act  to have disposed of such MDA Common Shares and will  be
deemed  to  have  acquired the Exchangeable  Shares  received  in
exchange  for  such  MDA Common Shares at a  cost  equal  to  the
adjusted cost base to such holder of such MDA Common Shares.

Based on the current administrative practise of Revenue Canada, a
holder of MDA Common Shares who receives cash not exceeding  $200
in  lieu  of  a fraction of an Exchangeable Share may reduce  the
adjusted  cost base of the Exchangeable Shares received  by  such
holder  by  the amount of such cash. Alternatively,  the  capital
gain or capital loss otherwise arising on the disposition of  the
fraction  of the MDA Common Share which is disposed of  for  such
cash may be reported.

If a holder of MDA Common Shares chooses to treat the exchange of
MDA   Common  Shares  for  Exchangeable  Shares  as   a   taxable
transaction, such holder of MDA Common Shares will be required to
recognize a capital gain (or capital loss) to the extent that the
fair  market  value of the Exchangeable Shares (and any  cash  in
lieu  of a fractional MDA Common Share) received in exchange  for
such  holder's MDA Common Shares immediately before the exchange,
net  of  any costs of disposition, exceeds (or is less than)  the
adjusted  cost  base  to  the holder of such  MDA  Common  Shares
immediately  before the exchange. The cost to the holder  of  the
Exchangeable  Shares  received in exchange for  such  MDA  Common
Shares  will  in this case be equal to the fair market  value  of
such Exchangeable Shares immediately before the exchange.

Where  the  transitional  rules  contained  in  the  Income   Tax
Application Rules, R.S.C. 1985, c.2 (5th Supplement), as  amended
(the  "ITARs"), apply to determine the adjusted cost  base  to  a
holder  of  MDA Common Shares of any MDA Common Shares  owned  by
such  holder  prior  to  1972 and continuously  thereafter  until
immediately  before the exchange of such shares for  Exchangeable
Shares,  such  rules may continue to apply for  the  purposes  of
determining  the  adjusted  cost  base  to  the  holder  of   any
Exchangeable Shares received in exchange therefor. Holders of MDA
Common  Shares  who may be affected by such rules should  consult
their own tax advisors.

Although  the  Plan  of Arrangement and the Voting  and  Exchange
Trust  Agreement  provide that Orbital  has  granted  the  Voting
Rights and Exchange Right to holders of the MDA Common Shares  in
consideration  of the Call Rights, it is possible Revenue  Canada
may  take the position that the Voting Rights and Exchange  Right
were acquired by a holder of MDA Common Shares in connection with
the exchange of the MDA Common Shares and not in consideration of
the  Call  Rights.  In such event, a holder of MDA Common  Shares
who  receives  Exchangeable Shares in  exchange  for  MDA  Common
Shares pursuant to the Plan of Arrangement would not qualify  for
the  "automatic"  rollover provisions  of  section  85.1  of  the
Canadian Tax Act.  In such circumstances, unless a holder of  MDA
Common Shares effects an election in respect of such exchange  in
accordance with the provisions of subsection 85(1) or (2) of  the
Canadian  Tax  Act  (as  described  below),  the  holder  may  be
considered  to have disposed of MDA Common Shares  in  a  taxable
transaction and the holder therefore may be required to recognize
a capital gain (or capital loss) to the extent that the aggregate
of the fair market value of the Exchangeable Shares (and any cash
in  lieu  of  a fractional MDA Common Share) and the fair  market
value of Voting Rights and Exchange Right (which MDA believes  to
be  nominal)  received in exchange for such holder's  MDA  Common
Shares  immediately  before the exchange, net  of  any  costs  of
disposition, exceeds (or is less than) the adjusted cost base  to
the  holder  of  such  MDA Common Shares immediately  before  the
exchange.   The  cost  to the holder of the  Exchangeable  Shares
received in exchange for such MDA Common Shares will in this case
be  equal  to  the fair market value of such Exchangeable  Shares
immediately before the exchange.

A  holder  may exchange MDA Common Shares and obtain  a  full  or
partial tax-free "rollover" in respect of such exchange by filing
with Revenue Canada (and, where applicable, with a provincial tax
authority)    an    election   (the   "Tax    Election")    under
subsection  85(1) of the Canadian Tax Act or, in the  case  of  a
partnership, under subsection 85(2) of the Canadian Tax Act  (and
the  corresponding  provisions of any applicable  provincial  tax
legislation)  made  jointly by the holder and Acquisition  (which
Acquisition, subject to the following paragraphs, has  agreed  to
make)  in  respect of the holder's MDA Common Shares so exchanged
pursuant  to  the  Plan of Arrangement and specifying  therein  a
"transfer  price,"  within  the  limitations  set  forth  in  the
Canadian  Tax Act, so that such MDA Common Shares will be  deemed
to  be  disposed  of  for proceeds of disposition  equal  to  the
transfer  price thereof.  Subject to the limitations set  out  in
subsection 85(1) of the Canadian Tax Act regarding the  specified
transfer  price, if the transfer price is equal to the  aggregate
of  the  adjusted cost bases of such MDA Common Shares determined
immediately before the exchange, no capital gain or capital  loss
will  be  realized, and to the extent that the transfer price  in
respect of such shares exceeds (or is less than) the aggregate of
the  adjusted  cost  bases thereof, such holder  will  realize  a
capital gain (or a capital loss).

Holders of MDA Common Shares who desire to effect the exchange of
their  MDA Common Shares pursuant to subsection 85(1) or  (2)  of
the  Canadian  Tax  Act, as the case may be,  should  obtain  the
appropriate federal election forms at any Revenue Canada District
Taxation  Office.   Where  necessary, the appropriate  provincial
election forms should be obtained from the income tax authorities
in that province.  These forms must be completed and submitted to
Acquisition   for  execution  at  the  following   address:   c/o
MacDonald, Dettwiler and Associates Ltd., 13800 Commerce Parkway,
Richmond,   British  Columbia,  V6V  2J3,  Attention:  Secretary.
Although the Tax Election involves certain complexities,  it  may
result in more favourable tax consequences to a holder than would
otherwise be the case if the Tax Election was not made in respect
of the exchange.

Holders  of MDA Common Shares who wish to effect the exchange  of
their  MDA Common Shares pursuant to subsection 85(1) or  (2)  of
the  Canadian  Tax  Act,  as the case may  be,  are  referred  to
Information  Circular  76-19R2 and  Interpretation  Bulletin  IT-
291R2,  published  by Revenue Canada, for information  respecting
the joint election to be made under the Canadian Tax Act.

The  comments provided herein with respect to joint elections are
provided  for general assistance only.  The law in this  area  is
complex  and  contains numerous technical requirements  including
limitations  applicable to the transfer price.   Compliance  with
such  requirements to ensure the validity of the joint  elections
will  be  the  sole  responsibility  of  the  holder  making  the
election.   Acquisition  will  not  be  responsible  for   proper
completion  and timely filing of such joint elections and  agrees
only  to  execute any properly completed election forms  received
from  holders  of  MDA Common Shares. In particular,  Acquisition
will  not  be  responsible  or liable for  any  taxes,  interest,
penalties,  damages  or expenses resulting from  the  failure  of
Acquisition  or  any  of  its agents, servants  or  officers,  to
properly  complete and return such joint election  forms  to  any
holder  for  filing by such holder with Revenue Canada  (and  the
appropriate  provincial authority, where applicable)  within  the
time  and in the prescribed form required under the Canadian  Tax
Act and any applicable provincial tax legislation.

Call Rights.  MDA is of the view and has advised counsel that the
Call  Rights, the Exchange Right and the Voting Rights have  only
nominal value.  The disposition by a holder of the Call Rights in
consideration  for  the  Voting Rights  and  the  Exchange  Right
should,  therefore, not result in any material  Canadian  federal
income  tax consequences.  Such determinations of value  are  not
binding  on Revenue Canada and counsel can express no opinion  on
matters  of  factual determination such as this.  If  the  Voting
Rights  or Exchange Right do have greater than nominal value  and
are  properly viewed as being received by a holder of MDA  Common
Shares  from  Orbital in consideration for  the  Call  Rights,  a
capital  gain would arise in an amount equal to the  fair  market
value of the Voting Rights and the Exchange Right and such holder
will  be  deemed  to have acquired such Voting  Rights  and  such
Exchange Right for a cost equal to their fair market value.

Dividends.   Dividends on Exchangeable Shares or  Orbital  Common
Shares  will  receive the following treatment under the  Canadian
Tax Act.

Exchangeable  Shares.   In the case of a shareholder  who  is  an
individual,  dividends received or deemed to be received  on  the
Exchangeable   Shares   will  be  included   in   computing   the
shareholder's  income, and will be subject to  the  gross-up  and
dividend   tax  credit  rules  normally  applicable  to   taxable
dividends received from taxable Canadian corporations.

The  Exchangeable Shares will be "taxable preferred  shares"  and
"short-term  preferred shares" for purposes of the  Canadian  Tax
Act, and accordingly, dividends received or deemed to be received
on  the  Exchangeable Shares will not be subject to the  10%  tax
under  Part  IV.1 of the Canadian Tax Act applicable  to  certain
corporations.

If  the Support Agreement is deemed to be a "guarantee agreement"
under the Canadian Tax Act and if Acquisition or any person  with
whom  Acquisition does not deal at arm's length is  a  "specified
financial institution" under the Canadian Tax Act at a  point  in
time  that  a  dividend  is paid on an Exchangeable  Share,  then
dividends received or deemed to be received by a shareholder that
is  a  corporation  will not be deductible in  computing  taxable
income  but  will  be  fully includable in taxable  income  under
Part  I  of  the  Canadian Tax Act.  Such dividend  will  not  be
subject  to  tax  under  Part IV of  the  Canadian  Tax  Act.   A
corporation  will generally be a specified financial  institution
for  these  purposes if it is a bank, a trust company,  a  credit
union,  an insurance corporation or a corporation whose principal
business  is  the  lending  of money to  persons  with  whom  the
corporation is dealing at arm's length or the purchasing of  debt
obligations issued by such persons or a combination thereof,  and
corporations   controlled  by  or  related  to   such   entities.
Acquisition  has  informed counsel that it is of  the  view  that
neither  it  nor any person with whom it does not deal  at  arm's
length  is a specified financial institution at the current  time
but  there  can be no assurance that this status will not  change
prior  to  the  time  any  dividend on an Exchangeable  Share  is
received or deemed to be received by a corporate shareholder.

Subject to the foregoing, in the case of a shareholder that is  a
corporation,  other than a "specified financial  institution"  as
defined in the Canadian Tax Act, dividends received or deemed  to
be   received  on  the  Exchangeable  Shares  will  normally   be
deductible in computing its taxable income.

A  shareholder that is a "private corporation" (as defined in the
Canadian Tax Act) or any other corporation resident in Canada and
controlled  or deemed to be controlled directly or indirectly  in
any manner whatsoever by or for the benefit of an individual or a
related group of individuals may be liable under Part IV  of  the
Canadian  Tax Act to pay a refundable tax of 33 1/3% on dividends
received  or deemed to be received on the Exchangeable Shares  to
the  extent  that such dividends are deductible in computing  the
shareholder's taxable income.

Orbital  Common Shares.  Dividends on Orbital Common Shares  will
be  included  in the recipient's income for the purposes  of  the
Canadian  Tax  Act.   Such dividends received  by  an  individual
shareholder will not be subject to the gross-up and dividend  tax
credit rules in the Canadian Tax Act.  A corporation which  is  a
shareholder will include such dividends in computing  its  income
and  generally will not be entitled to deduct the amount of  such
dividends  in computing its taxable income.  United  States  non-
resident  withholding tax on such dividends will be eligible  for
foreign tax credit or deduction treatment where applicable  under
the Canadian Tax Act.

Redemption or Exchange of Exchangeable Shares.  On the redemption
(including  a retraction) of an Exchangeable Share by Acquisition
for  an Orbital Common Share, the holder of an Exchangeable Share
will  be  deemed to have received a dividend equal to the amount,
if  any, by which the redemption proceeds (the fair market  value
at  the  time  of  the  redemption of the  Orbital  Common  Share
received  by  the shareholder from Acquisition on the  redemption
plus  the  amount,  if  any,  of  all  unpaid  dividends  on  the
Exchangeable Share) exceeds the paid-up capital at that  time  of
the  Exchangeable  Share so redeemed.  The  amount  of  any  such
deemed dividend will be subject to the tax treatment accorded  to
dividends described above.  On the redemption, the holder  of  an
Exchangeable  Share will also be considered to have  disposed  of
the  Exchangeable Share, but the amount of such  deemed  dividend
will  be  excluded  in  computing the shareholder's  proceeds  of
disposition for purposes of computing any capital gain or capital
loss  arising on the disposition of the Exchangeable  Share.   In
the  case  of a shareholder that is a corporation, it is possible
that in some circumstances the amount of any such deemed dividend
may  be  treated as proceeds of disposition and not as a dividend
and accordingly, such corporate shareholders should consult their
own tax advisors for specific advice in these circumstances.

On  the  exchange of an Exchangeable Share by the holder  thereof
with  Orbital for an Orbital Common Share pursuant  to  the  Call
Rights  or the Exchange Right, the holder will in general realize
a  capital gain (or a capital loss) equal to the amount by  which
the proceeds of disposition of the Exchangeable Share, net of any
reasonable  costs of disposition, exceed (or are less  than)  the
adjusted  cost  base  of the Exchangeable  Share  to  the  holder
thereof.  For these purposes, the proceeds of disposition will be
the value of an Orbital Common Share at the time of exchange plus
the amount of all unpaid dividends on the Exchangeable Share.

The  cost  of an Orbital Common Share received on the retraction,
redemption or exchange of an Exchangeable Share will be equal  to
the fair market value of the Orbital Common Share at the time  of
such event.

If  the  holder of an Exchangeable Share is a corporation,  or  a
partnership  or a trust of which a corporation is  a  partner  or
beneficiary,  as the case may be, the amount of any loss  arising
from a disposition or deemed disposition of an Exchangeable Share
in  certain  circumstances  may  be  reduced  by  the  amount  of
dividends received or deemed to have been received by it on  such
share.

Because  of  the existence of the Call Right, a holder exercising
the  right  of  retraction in respect of  an  Exchangeable  Share
cannot control whether such holder will receive an Orbital Common
Share  by  way  of  redemption  of  the  Exchangeable  Share   by
Acquisition  or by way of purchase of the Exchangeable  Share  by
Orbital.   As  described above, the Canadian federal  income  tax
consequences  of a redemption differ from those  of  a  purchase.
However, a holder who exercises the right of retraction  will  be
notified if the Call Right will not be exercised by Orbital,  and
if  such holder does not wish to proceed, such holder may  cancel
the  notice  of retraction and retain such holder's  Exchangeable
Share.

Dissenting  MDA Shareholders.  A holder of MDA Common  Shares  is
permitted  to  dissent from the Arrangement  in  compliance  with
section 190 of the CBCA and the Interim Order.  A MDA Shareholder
who  dissents from the Arrangement Resolution in compliance  with
section  190  of  the CBCA will be entitled,  in  the  event  the
Arrangement becomes effective, to be paid by MDA the  fair  value
of  the MDA Common Shares held by such shareholder determined  at
the appropriate date.  See "Dissenting Rights."  A Dissenting MDA
Shareholder  will be considered to receive a deemed dividend  and
to  have disposed of the MDA Common Shares in accordance with the
discussion  above  of the redemption of the Exchangeable  Shares.
Additional   income  tax  considerations  may  be   relevant   to
Dissenting MDA Shareholders who fail to perfect or withdraw their
claims  pursuant  to  the  rights  of  dissent.   Dissenting  MDA
Shareholders  should consult their own tax advisors for  specific
advice in these circumstances.

Foreign  Property.   The  Exchangeable  Shares  will  be  foreign
property  under  the  Canadian Tax Act  for  trusts  governed  by
registered  pension plans, registered retirement  savings  plans,
registered  retirement income funds and deferred  profit  sharing
plans or for certain other tax-exempt persons.  The Voting Rights
and  Exchange  Right will be foreign property under the  Canadian
Tax  Act.   Orbital Common Shares will be foreign property  under
the Canadian Tax Act.

Qualified  Investments.   The Exchangeable  Shares  will  not  be
qualified  investments  under the Canadian  Tax  Act  for  trusts
governed  by  registered  retirement  savings  plans,  registered
retirement income funds and deferred profit sharing plans and  at
the  end of each month, such trusts will be liable to pay  a  tax
under the Canadian Tax Act of 1% of the fair market value of  the
Exchangeable  Shares.  Orbital Common Shares  will  be  qualified
investments under the Canadian Tax Act for such plans as long  as
such shares remain listed on the NASDAQ (or are listed on certain
other exchanges).  The Voting Rights and Exchange Right will  not
be qualified investments under the Canadian Tax Act.

Holders of MDA Common Shares Not Resident in Canada

Generally,  MDA  Common  Shares  will  not  be  taxable  Canadian
property  provided that those shares are listed on  a  prescribed
stock exchange in Canada, the holder does not use or hold, and is
not  deemed  to use or hold, the MDA Common Shares in  connection
with  carrying  on a business in Canada and the  holder,  persons
with  whom  such  holder does not deal at arm's  length,  or  the
holder and such persons, has not owned (or had under option)  25%
or  more  of  the  issued shares of any class or  series  of  the
capital stock of MDA at any time within five years preceding  the
date in question.  The MDA Common Shares are currently listed  on
a prescribed stock exchange in Canada under the Canadian Tax Act.
Such  a  holder of MDA Common Shares will not be subject  to  tax
under the Canadian Tax Act on the exchange of MDA Common Shares.

Generally,  the  Exchangeable Shares  will  be  taxable  Canadian
property,  and on the redemption (including a retraction)  of  an
Exchangeable Share by Acquisition for an Orbital Common Share,  a
non-resident  holder of an Exchangeable Share will be  considered
to  have  received  a deemed dividend and be considered  to  have
disposed of the Exchangeable Share for proceeds of disposition in
an amount as described above for residents of Canada.  The amount
of   such   deemed  dividend  will  be  subject  to  non-resident
withholding  tax  under the Canadian Tax Act as described  below,
and Acquisition will require the non-resident holder to obtain  a
certificate pursuant to section 116 of the Canadian  Tax  Act  as
described below.  On the exchange of an Exchangeable Share by the
non-resident  holder thereof with Orbital for an  Orbital  Common
Share,  the non-resident holder of an Exchangeable Share will  be
considered  to  have  disposed  of  the  Exchangeable  Share  for
proceeds  of  disposition in an amount  as  described  above  for
residents  of  Canada, and Orbital will require the  non-resident
holder  to  obtain a certificate pursuant to section 116  of  the
Canadian Tax Act as described below.

Orbital or Acquisition, as the case may be, will require the non-
resident  holder of the Exchangeable Shares to apply  to  Revenue
Canada  to  obtain a certificate pursuant to section 116  of  the
Canadian Tax Act, specifying a certificate limit no less than the
fair market value of the Orbital Common Shares immediately before
the  exchange  or redemption, as the case may be.  A  certificate
should generally be obtainable from Revenue Canada where the non-
resident holder of Exchangeable Shares pays an amount on  account
of  tax  arising on a disposition or establishes that no  tax  is
payable.   Where no certificate is obtained by such  non-resident
holder   or   where  a  certificate  is  obtained  specifying   a
certificate limit less than the fair market value of the  Orbital
Common Shares, Orbital or Acquisition will withhold and remit  to
Revenue Canada within 30 days after the end of the month in which
Orbital or Acquisition acquires the Exchangeable Shares,  as  tax
on behalf of the non-resident holder, 33J% of the amount by which
the  fair  market value of the Orbital Common Shares exceeds  the
certificate  limit  specified  in  the  certificate  or   if   no
certificate  is obtained, 33J% of the fair market  value  of  the
Orbital Common Shares, and Acquisition or Orbital will deliver to
the non-resident holder a reduced number of Orbital Common Shares
to  reflect  such  payment to Revenue Canada.   Holders  of  such
Exchangeable Shares may be exempt from liability to pay tax under
the  Canadian  Tax  Act  by virtue of any applicable  tax  treaty
between  Canada and the country in which they are resident.   For
example, under the Canada-United States Income Tax Convention,  a
resident  of  the United States who has not been  a  resident  of
Canada at any time during the ten years immediately preceding the
exchange  of the Exchangeable Shares should generally  be  exempt
from  such  tax  under  the  Canadian  Tax  Act.   However,  such
exemption  will  not  relieve Acquisition or Orbital  from  their
liability  to  withhold or remit amounts  to  Revenue  Canada  on
account of tax where the non-resident holder has not provided the
appropriate certificate as discussed above.  Non-resident holders
of  Exchangeable Shares should consult their own tax advisors for
specific advice in these circumstances.

Dividends  paid  or deemed to be paid on the Exchangeable  Shares
are  subject  to non-resident withholding tax under the  Canadian
Tax  Act  at  the rate of 25%, although such rate may be  reduced
under  the  provisions of an applicable income tax  treaty.   For
example,  under  the Canada-United States Income Tax  Convention,
the rate is generally reduced to 15%.

A  holder  whose Exchangeable Shares are redeemed  (either  under
Acquisition's  redemption  right  or  pursuant  to  the  holder's
retraction  rights)  will  be deemed to  receive  a  dividend  as
described  above,  which  deemed  dividend  will  be  subject  to
withholding tax as described in the preceding paragraph.

MDA 1988 Optionholders

Pursuant  to  the Canadian Tax Act, a holder of each  outstanding
MDA  1988  Option which becomes a Replacement Option pursuant  to
the  Plan  of Arrangement will be deemed not to have disposed  of
the  MDA  1988  Option and not to have acquired  the  Replacement
Option,  provided  the  value of the  Replacement  Option  is  no
greater than the value of the MDA 1988 Option.  Furthermore,  the
Replacement Option shall be deemed to be the same option as,  and
a  continuation  of,  the MDA 1988 Option and  Orbital  shall  be
deemed to be the same corporation as, and a continuation of, MDA.

Dissenting MDA 1988 Optionholders.  A holder of MDA 1988  Options
is permitted to dissent from the Arrangement and shall be deemed,
pursuant  to  the Plan of Arrangement and the Interim  Order,  to
have  exercised the MDA 1988 Options with respect to which he  or
she  is exercising the dissent and the exercise price under  each
such  MDA  1988  Option shall be deemed to  be  paid  by  set-off
against the fair value paid for MDA Common Shares under such  MDA
1988 Option, determined at the appropriate date.  See "Dissenting
Rights."  A benefit (the "Benefit Amount") equal to the amount of
such  payment by MDA to the Dissenting MDA 1988 Optionholder will
be  deemed  to  have  been received by the  Dissenting  MDA  1988
Optionholder because of his or her employment and will  be  added
to  the  taxable  income of such holder, and where  the  exercise
price  for  the MDA Common Share under each such MDA 1988  Option
was  not less than the fair market value of the MDA Common  Share
at  the  time the agreement for the MDA 1988 Option was made,  an
amount  equal to one fourth of the Benefit Amount may be deducted
by  the  Dissenting  MDA 1988 Optionholder  for  the  purpose  of
computing   taxable   income.    Where   Dissenting   MDA    1988
Optionholders  are considered to have acquired MDA Common  Shares
under   his  or  her  MDA  1988  Option,  Dissenting   MDA   1988
Optionholders would also be considered to have received a  deemed
dividend.  Dissenting MDA 1988 Optionholders should consult their
own tax advisors for specific advice in these circumstances.

United States Federal Income Tax Considerations

In  the  opinion  of  Paul, Weiss, Rifkind, Wharton  &  Garrison,
United  States  counsel  to  MDA, the  following  summarizes  the
principal U.S. federal income tax considerations arising from and
relating  to the Arrangement, including the receipt and ownership
of  Exchangeable  Shares  and Orbital  Common  Shares,  that  are
generally  applicable to MDA Shareholders that are U.S.  citizens
or  residents, domestic corporations, domestic partnerships,  and
estates  or  trusts subject to U.S. federal income tax  on  their
income  regardless of source ("U.S. Holders") and to certain  MDA
Shareholders that are not U.S. Holders.  This summary is intended
for general information only.  It does not discuss all aspects of
U.S. federal income taxation that may be relevant to a particular
U.S.  Holder  (including potential application of the alternative
minimum  tax) or to certain types of investors subject to special
treatment  under the U.S. federal income tax laws  (for  example,
banks, life insurance companies, tax-exempt organizations, broker-
dealers  or U.S. Holders who received their MDA Common Shares  as
compensation), nor does it discuss any aspect of state, local  or
foreign tax laws.  Additionally, the following summary is limited
to  U.S.  Holders  (i)  who hold MDA Common  Shares  as  "capital
assets"  within the meaning of section 1221 of the United  States
Internal Revenue Code of 1986, as amended (the "Code"), (ii)  who
will  hold  Exchangeable  Shares and  Orbital  Common  Shares  as
"capital assets," (iii) who do not actually or constructively own
(and  have  not  at  any time in the preceding  five-year  period
actually or constructively owned) 10% or more of the voting stock
of  MDA  or  Acquisition,  as the case may  be,  and  (iv)  whose
ownership,  receipt  and disposition of Exchangeable  Shares  and
Orbital   Common  Shares  is  not  attributable  to  a  permanent
establishment in Canada.  The summary also does not  discuss  the
federal  income tax consequences of any transaction  involving  a
Qualifying Holdco.

This summary is based on laws, regulations, rulings and decisions
currently in effect, all of which are subject to change, possibly
with  retroactive effect.  In addition, U.S. Holders should  note
that there is no statutory, judicial, or administrative authority
that  directly addresses certain of the U.S. federal  income  tax
consequences  of  the issuance and ownership of  instruments  and
rights  comparable to the Exchangeable Shares, the Voting Rights,
the  Exchange  Right  and  the  Call  Rights.   Consequently  (as
discussed  more  fully below), many aspects of the  U.S.  federal
income  tax treatment of the Arrangement, including the  receipt,
ownership  and disposition of Exchangeable Shares, are uncertain.
No advance income tax ruling has been sought or obtained from the
Internal  Revenue Service ("IRS") regarding the tax  consequences
of  any of the transactions described herein.  Accordingly, it is
possible  that  the U.S. federal income tax consequences  of  the
Arrangement  and the holding and disposition of the  Exchangeable
Shares may differ from those described below.

U.S. HOLDERS AND NON-U.S. HOLDERS ARE URGED TO CONSULT THEIR  OWN
TAX  ADVISORS WITH RESPECT TO THE U.S. FEDERAL, STATE, AND  LOCAL
TAX   CONSEQUENCES  AND  THE  FOREIGN  TAX  CONSEQUENCES  OF  THE
ARRANGEMENT,  INCLUDING THE RECEIPT AND OWNERSHIP OF EXCHANGEABLE
SHARES OR ORBITAL COMMON SHARES.

Taxation of U.S. Holders

The Arrangement.  Although the matter is not free from doubt, MDA
and Orbital have been advised that there is a reasonable basis on
which  to  conclude  that the exchange of MDA Common  Shares  for
Exchangeable Shares pursuant to the Arrangement will constitute a
taxable transaction for U.S. federal income tax purposes, and MDA
understands  that  Orbital intends to report the  exchange  in  a
manner consistent with the foregoing.

If the exchange is a taxable transaction:

(1)  a   U.S.  Holder  who  receives  Exchangeable  Shares  would
     recognize  capital gain or loss in an amount  equal  to  the
     difference between the fair market value of the Exchangeable
     Shares  received  (together with cash received  in  lieu  of
     fractional  shares (if any)) and the adjusted basis  of  the
     MDA Common Shares surrendered in the exchange;

(2)  such capital gain or loss would be long-term capital gain or
     loss  if the MDA Common Shares exchanged have been held  for
     more than one year at the time of the exchange and otherwise
     would be short-term capital gain or loss;

(3)  an exchanging U.S. Holder would take as its tax basis in the
     Exchangeable   Shares   the  fair  market   value   of   the
     Exchangeable Shares at the time of the exchange;

(4)  the  holding  period of the Exchangeable Shares received  by
     the U.S. Holder in the exchange would begin on the day after
     the U.S. Holder receives the Exchangeable Shares; and

(5)  gain  realized  on  the exchange of MDA  Common  Shares  for
     Exchangeable  Shares  generally would  be  treated  as  U.S.
     source gain.

It  is  possible  that  the IRS may take the  position  that  the
receipt of Exchangeable Shares in exchange for MDA Common  Shares
is not a taxable event.  In such case:

(1)  a  U.S. Holder generally would not recognize gain or loss on
     the  receipt of the Exchangeable Shares; such a U.S.  Holder
     would,  however, be required to recognize gain to the extent
     of the receipt of cash in lieu of fractional shares (if any)
     and, possibly as discussed below, the value, if any, of  the
     Voting  Rights,  Exchange Right and other rights  under  the
     Support Agreement;

(2)  the  tax basis of the Exchangeable Shares would be equal  to
     the  tax  basis of the MDA Common Shares exchanged  therefor
     (reduced  by  the  tax basis allocated to  fractional  share
     interests); and

(3)  the  holding period of the Exchangeable Shares would include
     the  holding  period  of  the MDA  Common  Shares  exchanged
     therefor.

The  IRS  may assert that the Exchangeable Shares and certain  of
the rights associated therewith constitute "offsetting positions"
for  purposes of the straddle rules set forth in section 1092  of
the  Code.   In such case, the holding period of the Exchangeable
Shares  would  not  increase while held by  a  U.S.  Holder,  and
interest  incurred in carrying the Exchangeable Shares would  not
be deductible by a U.S. Holder.

MDA  believes  that  the  Voting Rights and  the  Exchange  Right
received  and  the  Call  Rights  conveyed  by  MDA  shareholders
pursuant  to  the Combination Agreement and the Arrangement  will
have  only  nominal value and, therefore, that their  receipt  or
conveyance  will not result in any material U.S.  federal  income
tax  consequences.  Further, the exchange of the Call Rights  for
the  Voting  Rights and the Exchange Right may not be taxable  to
such U.S. Holders because such U.S. Holders may be deemed to have
granted  a  purchase option to Orbital, which  is  not  generally
treated  as a taxable event for U.S. federal income tax  purposes
(although,  under this approach, the value of the  Voting  Rights
and  the  Exchange  Right would be taken into  account  upon  the
exercise  or lapse of the Call Rights).  It is possible, however,
that the IRS could take the position that the Voting Rights,  the
Exchange  Right  and  the Call Rights have greater  than  nominal
value and that the transfer or receipt of such rights is taxable.
In  such event, the receipt of the Voting Rights and the Exchange
Right  and  the  conveyance  of the Call  Rights  could  generate
taxable gain or loss.  Such gain or loss would generally be  U.S.
source  short-term capital gain or loss, unless the IRS  were  to
assert  that  the Voting Rights and the Exchange  Right  (or  any
other  rights,  such as the rights beneficially enjoyed  by  U.S.
Holders under the Support Agreement) were transferred to the U.S.
Holder by MDA, and not by Orbital, in consideration for a portion
of  the U.S. Holder's MDA Common Shares.  In the latter case, any
gain  recognized  by  a U.S. Holder may be  treated  as  ordinary
income.

Distributions  on the Exchangeable Shares.  MDA understands  that
Orbital  does not intend to pay dividends prior to the  Automatic
Redemption  Date, and thus, no dividends would  be  payable  with
respect  to the Exchangeable Shares.  If any such dividends  were
paid,  however,  a  U.S. Holder of Exchangeable Shares  generally
would  be required to include in gross income as ordinary  income
any  dividends paid on the Exchangeable Shares to the extent paid
out  of  the  earnings and profits of Acquisition, as  determined
under U.S. federal income tax principles.  Distributions, if any,
in  excess  of Acquisition's current or accumulated earnings  and
profits  would constitute a non-taxable return of  capital  to  a
U.S.  Holder  to  the extent of the U.S. Holder's  basis  in  the
Exchangeable Shares and would be applied against and  reduce  the
basis  in  the  Exchangeable Shares.  To  the  extent  that  such
distributions  are  in  excess of a U.S. Holder's  basis  in  the
Exchangeable  Shares, the distributions would constitute  capital
gain.   It is possible that the IRS could take the position  that
Orbital's, rather than Acquisition's, earnings and profits should
be taken into account in the foregoing calculations.

Based  on the tax position that Orbital has advised MDA  that  it
plans to take, any dividends paid on the Exchangeable Shares  out
of Acquisition's earnings and profits would be treated as foreign
source  dividend income and would generally not be  eligible  for
the   dividends   received  deduction  allowed   to   corporation
shareholders under the Code.  It is possible, however,  that  the
IRS  could  assert  that  such dividends constitute  U.S.  source
income.   Under  the  current  Canada-United  States  Income  Tax
Convention, such distributions to U.S. Holders would  be  subject
to  Canadian withholding tax at a rate of 15% irrespective of any
position that the IRS may take.  See "Canadian Federal Income Tax
Considerations  - Holders of MDA Common Shares  Not  Resident  In
Canada,"  above.  Subject to certain limitations of U.S.  federal
income  tax  law, a U.S. Holder should generally be  entitled  to
either a credit against its U.S. federal income tax liability  or
a  deduction in computing U.S. taxable income for Canadian income
taxes   withheld   from  distributions  with   respect   to   the
Exchangeable  Shares.   The  use of a  credit  may,  however,  be
limited  or precluded entirely if the U.S. Holder has  no  income
that is treated as non U.S. source income for U.S. federal income
tax purposes.

Exchange  or  Retraction of Exchangeable  Shares.   Although  the
matter  is not free from doubt, MDA and Orbital have been advised
that  there is a reasonable basis on which to conclude  that  the
exchange, retraction or redemption of the Exchangeable Shares for
Orbital Common Shares will be treated as a taxable event for U.S.
federal income tax purposes, and Orbital has advised MDA that  it
currently  intends to take this position.  If the exchange  is  a
taxable event, and the U.S. Holder receives Orbital Common Shares
from Orbital pursuant to the Call Rights:

(1)  a  U.S. Holder generally would recognize gain or loss  equal
     to  the  difference  between the fair market  value  of  the
     Orbital  Common Shares at the time of the exchange (together
     with cash equal to the Dividend Amount (if any) and cash  in
     lieu  of  fractional shares (if any)) and the U.S.  Holder's
     tax basis in the Exchangeable Shares;

(2)  such  gain or loss would generally be capital gain or  loss,
     except  that  the  IRS  could  assert  that  a  holder  must
     recognize  amounts attributable to any declared  but  unpaid
     dividends on the Exchangeable Shares as ordinary income that
     may he treated as U.S. source income;

(3)  any capital gain or loss would be long-term capital gain  or
     loss if the Exchangeable Shares have been held for more than
     one year at the time of the exchange and otherwise would  be
     short-term capital gain or loss;

(4)  the  U.S. Holder would take as its tax basis in the  Orbital
     Common  Shares  the fair market value of the Orbital  Common
     Shares at the time of the exchange;

(5)  the holding period of the Orbital Common Shares received  by
     the U.S. Holder in exchange would begin on the day after the
     U.S. Holder receives the Orbital Common Shares; and

(6)  gain  realized  on the exchange of Exchangeable  Shares  for
     Orbital  Common  Shares generally will be  treated  as  U.S.
     source gain.

If  the  receipt of Orbital Common Shares is effected  through  a
retraction  or redemption of Exchangeable Shares with respect  to
which  Orbital does not exercise its overriding Call  Right,  and
thus  the Orbital Common Shares are distributed to a U.S.  Holder
directly by Acquisition, then if the retraction or redemption  is
treated as a taxable transaction, it will be treated as a taxable
exchange  of  the Exchangeable Shares (treated for  U.S.  federal
income  tax  purposes as described above) if the  retraction  (i)
results  in  a "complete termination" of the U.S. Holder's  stock
interest in Acquisition under section 302(b)(3) of the Code, (ii)
is  "substantially  disproportionate" with respect  to  the  U.S.
Holder  under  section 302(b)(2) of the Code, or  (iii)  is  "not
essentially  equivalent to a dividend" with respect to  the  U.S.
Holder  under  section  302(b)(1) of the  Code.   In  determining
whether  any  of  these  tests has  been  met,  shares  of  stock
considered  to be owned by the U.S. Holder by reason  of  certain
constructive  ownership rules set forth in  section  318  of  the
Code,  as well as shares actually owned, generally must be  taken
into  account.  If a retraction or a redemption is treated  as  a
taxable  transaction but does not meet any of the tests described
above,  the cash and the fair market value of the Orbital  Common
Shares received by the U.S. Holder would generally be taxed as  a
dividend  paid  on  the  Exchangeable  Share  to  the  extent  of
Acquisition's  (or,  possibly, Orbital's) earnings  and  profits.
See "Distributions on the Exchangeable Shares," above.

Irrespective of how the retraction or redemption is  treated  for
U.S. federal income tax purposes, it will, as discussed above, be
subject  to  Canadian  withholding tax.   See  "Canadian  Federal
Income  Tax  Considerations - Holders of MDA  Common  Shares  Not
Resident  in  Canada," above.  Any Canadian tax  imposed  on  the
exchange  will  be  available as a credit  against  U.S.  federal
income  taxes, subject to applicable limitations.   For  example,
the use of such a credit may be limited or precluded entirely  if
the  U.S. Holder has no income that is treated as non U.S. source
income  for  U.S. federal tax purposes.  A U.S.  Holder  that  is
ineligible for a foreign tax credit with respect to any  Canadian
tax  paid,  or  who otherwise so chooses, may be  entitled  to  a
deduction therefor in computing U.S. taxable income.

It  is possible that the exchange, or retraction or redemption of
Exchangeable Common Shares for Orbital shares would  be  held  to
constitute a nonrecognition event.  In such case:

(1)  a  U.S.  Holder that exchanges its Exchangeable  Shares  for
     Orbital Common Shares generally would not recognize gain  or
     loss on the receipt of the Orbital Common Shares;

(2)  a  U.S. Holder would, however be required to recognize  gain
     to  the  extent of the receipt of cash in lieu of fractional
     shares (if any) exceeds the tax basis allocable thereto  and
     income (which may be ordinary income) to the extent of  cash
     equal to the Dividend Amount (if any);

(3)  the tax basis of the Orbital Common Shares would be equal to
     the  tax basis of the Exchangeable Shares exchanged therefor
     (reduced  by  the  tax basis allocated to  fractional  share
     interests); and

(4)  the  holding  period  of  the Orbital  Common  Shares  would
     include  the  holding  period  of  the  Exchangeable  Shares
     exchanged therefor.

Dissenting U.S. Holders.  A U.S. Holder who exercises  its  right
to  dissent  from the Arrangement will generally  recognize  U.S.
gain or loss on the exchange of its MDA Common Shares for cash in
an  amount  equal to the difference between the  amount  of  cash
received  and  its adjusted tax basis in the MDA  Common  Shares.
Such  gain  or loss will be capital gain or loss if  such  shares
have been held for more than one year at the time of the exchange
and  otherwise will be short-term capital gain or loss, and  will
generally be U.S. source.

Shareholders Not Resident in or Citizens of the United States

The  following  summary is applicable to a holder of  MDA  Common
Shares that is not a U.S. Holder ("non-U.S. Holder").

A  non-U.S. Holder generally will not be subject to U.S.  federal
income  tax on gain recognized on the receipt of the Exchangeable
Shares, the Voting Rights and the Exchange Right, on the sale  or
exchange of the Exchangeable Shares, or on the receipt or sale of
the  Orbital  Common  Shares  unless  such  gain  is  effectively
connected with the conduct by the non-U.S. Holder of a U.S. trade
or  business  or,  if  a  tax treaty  applies,  if  the  gain  is
attributable  to a U.S. permanent establishment of  the  non-U.S.
Holder.

If  gain  recognized by a non-U.S. Holder on the receipt  of  the
Exchangeable  Shares, on the sale or exchange of the Exchangeable
Shares,  or on the receipt or sale of the Orbital Common  Shares,
is  effectively  connected with a U.S. trade or  business  or  is
attributable  to a permanent establishment in the United  States,
the  non-U.S. Holder would be subject to U.S. federal income  tax
at  the  graduated  rates that are applicable to  U.S.  citizens,
resident aliens, and domestic corporations, and may be subject to
withholding  in certain circumstances.  Non-U.S. Holders  may  be
entitled  to  a  limited foreign tax credit  on  non-U.S.  source
income  that  is  effectively connected  with  a  U.S.  trade  or
business.   In addition, if the non-U.S. Holder is a corporation,
the branch profits tax also may apply.

MDA  understands  that Orbital does not intend to  pay  dividends
prior  to  the  Automatic Redemption Date and thus, no  dividends
would  be  payable with respect to the Exchangeable Shares.   Any
dividends  received  by a non-U.S. Holder  with  respect  to  the
Exchangeable  Shares  should not be subject to  U.S.  withholding
tax,  and  MDA  understands  that  it  is  not  anticipated  that
Acquisition  would withhold any amounts in respect  of  such  tax
from  such dividends.  The possibility exists, however, that  the
IRS  may assert that U.S. withholding tax is payable with respect
to dividends paid on the Exchangeable Shares to non-U.S. Holders.
In  such case, holders of Exchangeable Shares could be subject to
U.S.  withholding tax at a rate of 30%, which rate may be reduced
by  an  applicable income tax treaty in effect between the United
States  and  the non-U.S. Holder's country of residence  (15%  on
dividends paid to residents of Canada).  Dividends paid to a non-
U.S. Holder that are effectively connected with the conduct of  a
trade or business in the United States are taxed at the graduated
rates that are applicable to U.S. citizens, resident aliens,  and
domestic corporations, and are not subject to withholding if  the
non-U.S. holder gives an appropriate statement to the withholding
agent  in  advance  of  the dividend payment.   Such  effectively
connected  dividends  also may, under certain  circumstances,  be
subject  to  an  additional branch profits tax  if  the  non-U.S.
Holder is a corporation.

Dividends  received  by a non-U.S. Holder  with  respect  to  the
Orbital   Common  Shares  generally  will  be  subject  to   U.S.
withholding  tax at a rate of 30%, which rate may be  subject  to
reduction  by  an applicable income tax treaty (15% on  dividends
paid  to  residents of Canada).  If the dividends are effectively
connected  with  the conduct of a U.S. trade  or  business,  they
would be taxed at the graduated rates that are applicable to U.S.
citizens,  resident aliens, and domestic corporations, and  would
not  be  subject to withholding if the non-U.S. holder  gives  an
appropriate statement to the withholding agent in advance of  the
dividend  payment.  A non-U.S. Holder that is a corporation  also
may be subject to an additional branch profits tax on effectively
connected dividends.

The Orbital Common Shares (and, possibly, the Exchangeable Shares
or  a portion thereof) will be deemed to be U.S. situs assets for
purposes of the U.S. federal estate tax with the result that  any
such shares held by an individual non-U.S. Holder at the time  of
his  or her death will be subject to the U.S. federal estate tax,
except  as may otherwise be provided by an applicable estate  tax
treaty with the U.S.

Information, Reporting and Backup Withholding

Information reporting to the IRS by paying agents and  custodians
located  in  the  United States may be required with  respect  to
amounts  received  on the disposition of Exchangeable  Shares  or
Orbital  Common  Shares,  or dividends  paid  on  either  of  the
foregoing.  A U.S. Holder may be subject to backup withholding at
the  rate  of 31% with respect to dividends paid by such persons,
unless  the  holder (i) is a corporation or comes within  certain
other  exempt  categories and, when required,  demonstrates  this
fact,   or  (ii)  provides  a  taxpayer  identification   number,
certifies as to no loss of exemption from backup withholding, and
otherwise  complies with applicable requirements  of  the  backup
withholding rules.  Generally, dividends paid to non-U.S. Holders
of  the  Orbital Common Shares that are subject to  the  30%  (or
reduced  treaty)  rate of withholding tax  will  be  exempt  from
backup  withholding tax.  Backup withholding is not an additional
tax, and may be credited against the holder's federal income  tax
liability.


               INFORMATION CONCERNING ACQUISITION

Acquisition  was incorporated under the CBCA on August  11,  1995
solely for the purpose of entering into the Combination Agreement
and  completing the transactions contemplated thereby,  including
the  Arrangement.  Acquisition has not carried  on  any  material
business  or  activities  other  than  those  relating   to   the
Combination  Agreement and the Arrangement.  The  registered  and
principal office of Acquisition is located at 44th Floor, 1 First
Canadian  Place,  Toronto, Ontario, M5X 1B1.  It  is  anticipated
that  immediately  prior to the Effective Date, Acquisition  will
change  its  registered and principal office  to  13800  Commerce
Parkway, Richmond, British Columbia, V6V 2J3.

Acquisition is a wholly owned subsidiary of Orbital.  Pursuant to
the Arrangement, among other things, the authorized share capital
of  Acquisition will be amended to authorize an unlimited  number
of Exchangeable Shares and 10,000 Class B Preferred Shares; as  a
result of this amendment, Acquisition will have three classes  of
authorized  share  capital consisting of an unlimited  number  of
common  shares,  an unlimited number of Exchangeable  Shares  and
10,000  Class  B Preferred Shares.  Pursuant to the  Arrangement,
the Exchangeable Shares will be issued to MDA Shareholders (other
than  Dissenting  MDA  Shareholders) and  holders  of  shares  of
Qualifying Holdcos in exchange for the MDA Common Shares held  by
them or the Qualifying Holdcos, as the case may be.  As a result,
Acquisition will become the sole shareholder of MDA.  The  10,000
Class B Preferred Shares will be issued to Canadian Imperial Bank
of  Commerce  as partial payment for investment banking  services
rendered with respect to the Arrangement.  All of the issued  and
outstanding common shares of Acquisition will be held by Orbital.
In addition, pursuant to the Arrangement, the name of Acquisition
will  be changed to "MacDonald Dettwiler Holdings Inc."  See "The
Arrangement and The Combination Agreement - Plan of Arrangement."

The directors of Acquisition are David W. Thompson (President and
Chief   Executive  Officer  of  Orbital),  Ian  J.  Cowan  (Vice-
President, Lehman Brothers Canada Inc.) and Michael Gregory (Vice-
President,  Lehman  Brothers  Canada  Inc.).   The  officers   of
Acquisition  are  David  W.  Thompson,  President,   Carlton   B.
Crenshaw,  Vice-President and Treasurer, and  Leslie  C.  Seeman,
Secretary, all of whom are also officers of Orbital.


                 INFORMATION CONCERNING ORBITAL

Background and Recent Acquisitions

Orbital  was incorporated under the laws of the State of Delaware
in   1987.   Its  headquarters  are  located  at  21700  Atlantic
Boulevard, Dulles, Virginia, 20166, U.S.A.

Orbital is a space technology company that designs, manufactures,
operates and markets a broad range of space products and services
that are grouped into three categories: Launch Systems, Space and
Electronics Systems, and Communications and Information  Systems.
Launch  Systems  include  space and suborbital  launch  vehicles;
Space  and  Electronics  Systems include  satellites,  spacecraft
platforms, space sensors and instruments, and space payloads  and
experiments,  as  well as advanced avionics and  data  management
systems;  and  Communications  and  Information  Systems  include
satellite-based  two-way  mobile  data  communications   systems,
satellite-based  navigation products and remote sensing  systems,
along   with   satellite  tracking  systems   and   environmental
monitoring products.

Orbital's  goal  is  to become a full-service  space  company  by
integrating  its launch vehicles, satellites and  other  products
into  complete "turn-key" space systems and providing  end-to-end
satellite-based  services  for  particular  markets.    Orbital's
strategy  is  to  exploit  expanding  opportunities  to   provide
government,  commercial and other customers with low-cost  access
to  and  operations  in space.  Essential elements  of  Orbital's
strategy include investment of substantial private capital in the
development  of  proprietary  products;  reduction  of  the  time
required for product development; formation of strategic business
alliances    to    enhance   Orbital's   marketing,    technical,
manufacturing  and financial capabilities; and  establishment  of
vertically integrated manufacturing and testing capabilities.  In
addition, Orbital believes that its strategy of providing  "turn-
key"  space systems, through the integration of lower-cost  space
launch  vehicles with lower-cost smaller satellites  and  sensors
and  instruments, should stimulate the use of space products  and
services   by  private  corporations,  educational  and  research
institutions and other non-traditional space customers including,
ultimately, individual consumers.

An  important  element  of Orbital's strategy  to  integrate  its
various  products  into  complete  "turn-key"  systems   is   the
acquisition  of companies with product lines that  complement  or
enhance  Orbital's  existing  base of  products,  technology  and
services.  Orbital acquired Space Data Corporation ("Space Data")
in  1988, thereby expanding its product lines and increasing  its
vertical  integration  in production and testing.   In  September
1993,  Orbital  acquired all the assets of the  Applied  Sciences
Operation,  a  division of The Perkin-Elmer Corporation  ("ASO").
This  operation  designs,  develops and produces  satellite-borne
scientific sensors for space and terrestrial research and in situ
atmospheric monitoring equipment for human space flight programs.
In  August  1994  and  December 1994, Orbital acquired  Fairchild
Space   and   Defense  Corporation  ("Fairchild")  and   Magellan
Corporation    ("Magellan"),   respectively.     The    Fairchild
acquisition has enhanced Orbital's satellite system and subsystem
development   and  production  capabilities  and   has   expanded
Orbital's  existing product lines by adding various sophisticated
electronics and defence products.  Magellan designs, manufactures
and  markets  hand-held receivers for Global  Positioning  System
("GPS") satellite-based navigation and positioning for commercial
and consumer markets.

Orbital's    customer   base   includes   a   wide    range    of
U.S.   governmental   agencies,   universities   and   commercial
enterprises  including NASA; the National Oceanic and Atmospheric
Administration; various organizations within the U.S.  Department
of  Defense ("DoD") including the U.S. Army, the U.S.  Navy,  the
U.S.  Air  Force,  ARPA  and BMDO; ORBCOMM Global;  John  Hopkins
University;   and   certain  distributors  of   electronics   and
recreational    equipment.    Orbital's    diversification    and
integration of space-based products and services is reflected  in
its  revenue  mix  with  34%, 40% and 26% of  its  1994  revenues
derived  from Launch Systems, Space and Electronics  Systems  and
Communications  and  Information Systems, respectively.   Orbital
had  revenues of approximately US$222 million for the year  ended
December 31, 1994.  As of June 30, 1995, Orbital's total backlog,
including  firm  orders  of  approximately  US$495  million,  was
approximately US$1.3 billion.

Orbital  has three wholly owned active subsidiaries --  Magellan,
ORBIMAGE  and  Fairchild  -- and owns 99.9%  of  the  outstanding
shares of ORBCOMM.  Magellan, ORBIMAGE, Fairchild and ORBCOMM are
each incorporated under the laws of the State of Delaware.

Description Of Orbital's Products And Services

The  space products and services provided by Orbital are  grouped
into  three  categories: Launch Systems,  Space  and  Electronics
Systems, and Communications and Information Systems.

Launch Systems

Orbital's  Launch  Systems  Group's products  include  space  and
suborbital  launch vehicles.  Orbital also continues  to  explore
new,  longer-term research and development opportunities for more
affordable and flexible space launch vehicles, such as  the  X-34
reusable launch vehicle described below.

Space  Launch  Vehicles.   A  space  launch  vehicle  launches  a
satellite  into  orbit around the Earth.  Orbital's  three  space
launch  vehicles are the Pegasus launch vehicle, the  Pegasus  XL
launch vehicle, and the Taurus launch vehicle.

Orbital's  Pegasus  vehicle is launched from beneath  a  modified
large  aircraft, such as a Lockheed L-1011, to deploy  satellites
up  to  1,000 pounds into low-Earth orbit.  Customers for Pegasus
include the U.S. Air Force, NASA, BMDO, ORBCOMM Global and  ARPA,
as  well  as  the Brazilian and Spanish space agencies.   Through
September  1995, Orbital has conducted a total of seven  standard
Pegasus   missions,  all  of  which  were  fully   or   partially
successful.   Whether a mission is fully or partially  successful
depends on the particular mission requirements designated by  the
customer.   The modified Pegasus XL, developed to deploy  heavier
satellites  into  orbit,  has had two unsuccessful  flights,  one
occurring  in  June 1994 and the other occurring  in  June  1995.
Orbital  believes that it correctly identified and  remedied  the
cause  of  the 1994 failure.  Orbital believes it has  identified
the  cause  of  the 1995 failure, which was not  related  to  the
anomalies  observed  in  the first unsuccessful  flight,  and  is
implementing  what  it  believes to be the  necessary  corrective
actions.  There can be no assurance, however, that the causes  of
the failures here been correctly identified or that they will  be
successfully corrected.  In 1992, Orbital entered into a ten-year
lease for a Lockheed L-1011 aircraft, which has been modified  to
enable  it  to  launch both the Pegasus and Pegasus XL  vehicles.
There  is  no  assurance that, in the event that the L-1011  were
unavailable for any reason, another aircraft could be obtained on
a timely or cost-effective basis.

The  higher-capacity  Taurus vehicle  is  a  four-stage,  ground-
launched  derivative  of  the  Pegasus  vehicle  that  can  carry
payloads  weighing  up  to 3,000 pounds to  low-Earth  orbit  and
payloads  weighing  up  to  800 pounds to  geosynchronous  orbit.
Taurus  is  designed  to  be  readily transported  with  a  self-
contained   launch   pad,  including  assembly   and   pre-flight
equipment, so that launch from a variety of developed  or  remote
locations  can  be  achieved on short  notice.   In  March  1994,
Orbital successfully launched the first Taurus vehicle, deploying
two satellites for ARPA.

Suborbital  Launch  Vehicles.  Suborbital launch  vehicles  place
payloads into a variety of high-altitude trajectories but, unlike
space  launch  vehicles, do not place payloads into orbit  around
the   Earth.    Orbital's  suborbital  launch  products   include
suborbital  vehicles  and  their principal  subsystems,  payloads
carried   by   such   vehicles,  and   related   launch   support
installations  and systems used in their assembly and  operation.
Orbital  offers  its  customers customized  vehicle  and  payload
design, manufacturing and integration, launch and mission support
and  tracking and recovery services, as well as construction  and
activation  of  launch  pads and other  infrastructure  elements.
Customers  typically use Orbital's suborbital launch vehicles  to
launch  scientific  and  other payloads and  for  defence-related
applications such as target and interceptor experiments for anti-
missile  defence  systems.  The primary customers  for  Orbital's
suborbital launch vehicles include the U.S. Army, the  U.S.  Navy
and BMDO.

From January 1991 through September 1995, Orbital has conducted a
total  of  38 launches of suborbital vehicles, of which  34  have
been  fully or partially successful and four have been  failures.
While  cutbacks  in  the DoD's budget and, in  particular,  those
projects  related to missile defence have resulted  in  decreased
revenues  attributable to suborbital launches,  Orbital  believes
that  increasing sophistication of missile technology and  public
concern  over  the  United States' missile  defence  system  will
continue   to  provide  opportunities  for  Orbital's  suborbital
program.

Reusable  Launch Vehicles.  A major reason for the high  cost  of
access  to  space today using expendable launch vehicles  is  the
fact   that   the  entire  launch  vehicle,  including  expensive
structures and electronics equipment, is expended during  launch.
Orbital  is  currently  developing the  X-34  partially  reusable
launch  vehicle with the goal of significantly reducing the  cost
of  access to space.  Like Pegasus, the X-34 will be air-launched
from  a carrier aircraft.  Although the X-34 upper stage will  be
expended during launch, the booster vehicle itself will return to
Earth, to be refurbished and reused in subsequent launches.   The
X-34  is  being  designed  to launch  small  500  to  1,000-pound
satellites to low-Earth orbit.

In  March 1995, Orbital entered into a Cooperative Agreement with
NASA  to  develop, construct, test and launch two  X-34  reusable
launch   vehicles.    At   that  time,   Orbital   and   Rockwell
International  Corporation ("Rockwell")  agreed  to  establish  a
joint  venture,  to be called American Space Lines  ("ASL"),  the
terms of which are under negotiation, to develop, construct, test
and  operate two X-34 small reusable launch vehicles.  Under  the
ASL  joint venture, Orbital will be the prime contractor for  the
design and construction of the launch vehicle, and Rockwell  will
be  a  subcontractor for the design and construction  of  various
subsystems,  including  the  propulsion  and  thermal  protection
subsystems.  There can be no assurance that Orbital and  Rockwell
will successfully conclude their negotiations to establish ASL.

Orbital  estimates that the development, construction and initial
testing  of  the  first two X-34 vehicles will  require  a  total
investment  of  at least US$190 million.  Under  the  Cooperative
Agreement  between Orbital (to be novated to ASL) and NASA,  NASA
will  partially fund the project by providing approximately US$60
million  in  cash to ASL as specified performance milestones  are
met.   NASA  also  is providing approximately  US$10  million  in
funding   NASA  centres  that  will  perform  as  subcontractors.
Orbital and Rockwell are expected to fund the remaining costs  of
the X-34 program.

The Cooperative Agreement can be suspended or revoked by NASA  or
Orbital/ASL at any time, and there can be no assurance that  NASA
will  continue  to  fund  or support the project  to  the  extent
presently contemplated by the Cooperative Agreement.  Development
and  construction of the X-34 is in a very early  stage  and  the
actual  cost  of  the  X-34  and  the  amount  and  structure  of
anticipated investment in ASL may vary significantly from current
estimates.  There can be no assurance that the funds expected  to
be  committed by Orbital, Rockwell and NASA will be sufficient to
finance  the  project,  or that ASL will be  able  to  raise  the
required capital if NASA exercises its right to suspend or revoke
the  Cooperative  Agreement.  In the  event  that  ASL  does  not
receive the necessary capital and Orbital and Rockwell decide not
to  go  forward  with the project, Orbital could be  required  to
expense part or all of its expected investment in ASL.

Space and Electronics Systems

Orbital's Space and Electronics Systems Group's products  include
spacecraft systems and payloads, defence avionics and sensors.

The  Space and Electronics Systems Group is responsible  for  the
design,  production  and  testing  of  small  and  medium   class
spacecraft  for scientific, military and commercial applications.
The  small  standard spacecraft platforms developed  by  Orbital,
such  as  the  PegaStar and the MicroStar,  are  designed  to  be
launched  by the Pegasus or Taurus launch vehicle.  The  PegaStar
spacecraft  platform  is a general purpose  spacecraft  that  has
successfully  performed  one  mission  for  the  U.S.  Air  Force
measuring  space radiation.  It is also planned to  be  used  for
Orbital's   SeaStar  ocean  environmental  monitoring   satellite
system.  Orbital's MicroStar spacecraft platform is designed  for
use  in the ORBCOMM System and also for a variety of small  space
science  and  remote sensing projects, including  some  of  those
being pursued by Orbital's wholly owned subsidiary, ORBIMAGE.  In
April  1995, the first three MicroStar spacecraft were  deployed,
two  for  the ORBCOMM System, and the other to monitor  lightning
and severe weather patterns for NASA.

Orbital's medium class satellites, such as TOPEX/Poseidon, NASA's
Upper Atmosphere Research Satellite, Landsat 4 and Landsat 5 have
been  in  space for several years, and are used to gather various
scientific data, such as ocean topography and ultraviolet sources
outside  the  galaxy.  In August 1995, Orbital  was  selected  to
become the spacecraft supplier to Johns Hopkins University, which
is  leading  NASA's Far Ultraviolet Spectroscopy Explorer  (FUSE)
program   to  measure  far  ultraviolet  radiation.    The   FUSE
spacecraft is presently scheduled for launch in 1998.

Orbital  develops,  manufactures and markets  avionics,  advanced
electronics  and  data  management systems  for  aircraft  flight
operations  and  ground support.  These systems collect,  process
and  store mission-critical data for, among other things, mission
planning and flight operations, and manage on-board equipment for
strategic tactical military aircraft, helicopters, satellites and
surface  vehicles.   The primary customers  for  data  management
systems are the U.S. Navy, the U.S. Air Force, various DoD  prime
contractors  and  foreign governments.  Orbital  is  the  leading
supplier  of  certain  avionics systems and  products,  including
mission  data  loaders  for  the U.S.  Navy,  and  data  transfer
equipment and digital terrain systems for the U.S. Air Force.  In
addition,  Orbital provides stores management systems,  including
weapons  arming and firing functions for use on tactical aircraft
and  helicopters.  The avionics systems and products are deployed
on a number of aircraft, including the F-14, F-15, F-16, F-22 and
the LAMPS Helicopter.

Orbital's  satellite-borne  scientific  sensors  and  instruments
include    atmospheric   ozone   monitoring    instruments    and
environmental  sensors.   The  Total Ozone  Mapping  Spectrometer
("TOMS") instrument was produced by Orbital to be launched  on  a
Pegasus vehicle for NASA.  TOMS will measure ozone concentrations
around the world for the purpose of monitoring the effect of man-
made chemicals and atmospheric conditions on the ozone layer.  In
addition,  Orbital is currently developing and producing  various
in  situ  monitoring products for space and defence applications.
These  products  include  the Atmospheric Composition  Monitoring
Assembly,  being  developed  under a  contract  with  The  Boeing
Company,  that  will  measure various atmospheric  gases  in  the
crew's  living quarters on the Space Station for the  purpose  of
ensuring  a  healthy living environment for astronauts.   Orbital
also  produces the Central Atmospheric Monitoring System for  the
U.S. Navy for use on submarines.

Communications and Information Systems

Orbital's Communications and Information Systems include  planned
and  operational  products  and services  provided  by  Orbital's
Magellan,   ORBCOMM   and   ORBIMAGE   subsidiaries.     Magellan
manufactures  GPS  satellite-based  navigation  and   positioning
products for commercial and consumer markets including marine and
aviation applications, outdoor recreational users such as hunters
and  hikers,  professional users such as geologists, geographers,
surveyors, natural resource managers and contractors  and,  to  a
lesser  extent,  the U.S. Government.  ORBCOMM and  ORBIMAGE  are
developing  satellite-based services  to  address  the  expanding
market  for  global two-way data communications  and  information
derived  from remote sensing of the atmosphere, oceans  and  land
surfaces.  Orbital believes that the ORBCOMM and ORBIMAGE systems
will  require significant capital investments.  Although  Orbital
believes   the   long-term  profit  potential  of  such   service
businesses  developed  and  supported  by  Orbital's  proprietary
product  technologies is significant, there can be  no  assurance
that   Orbital  will  be  able  to  successfully  develop   these
businesses.

Satellite-Based  Navigation and Positioning Products.   Orbital's
Magellan  subsidiary designs, manufactures and markets  hand-held
GPS  receivers  that provide users with precise  positioning  and
navigation  information  for  a  broad  range  of  personal   and
professional  activities  including  marine  navigation,  outdoor
recreation (hiking and hunting), surveying and general  aviation.
Magellan  focuses its research, design and engineering activities
on  the development of GPS receivers that are reliable, portable,
easy-to-use  and  affordable,  recently  targeting  the   growing
recreational  market.   Magellan  is  also  expected  to   be   a
significant  supplier of personal communicators for  the  ORBCOMM
System.

In   addition,  Orbital's  Germantown  operations  produce   data
management  systems  that  have  been  applied  to  the   design,
development   and  manufacture  of  "intelligent   transportation
systems,"  primarily  for  metropolitan transit  operators,  that
provide   GPS-based   location  of   vehicles   and   allow   for
communications and schedule management.

ORBCOMM  System.   The  ORBCOMM System  is  designed  to  provide
virtually  continuous  mobile data communications  coverage  over
much of the Earth's surface.  Under this design, subscribers will
be  able  to use inexpensive, pocket-sized personal communicators
to  send  and receive short messages, emergency alerts and  other
critical   information,  and  to  use  the   position-determining
capability  of  the communicators to obtain data  concerning  the
location  and condition of automobiles, trucks, shipping  vessels
and  other valuable assets.  Orbital expects that the ability  to
send  and  receive  other short messages  and  data  without  the
geographic  limitations  of existing data communications  systems
will stimulate the growth of new markets for satellite-based data
communications  and  will  be  used  to  supplement   terrestrial
communications systems by providing relatively low-cost  coverage
in areas outside the range of these systems.

The  ORBCOMM System design consists of a constellation  of  small
low-Earth  orbit satellites, a satellite control centre operating
and   positioning   the  satellites,  network   control   centres
controlling  the  flow of information through the  system,  local
ground stations sending and receiving signals between the network
control   centres   and  nearby  satellites,   and   the   mobile
communicators  used  by  subscribers  to  transmit  and   receive
messages  to and from nearby satellites.  In April 1995,  Orbital
successfully launched the first two satellites that will comprise
the  ORBCOMM System constellation.  After working through certain
anomalies  that were initially observed on these two  spacecraft,
the  satellites have validated a number of technical capabilities
of  the ORBCOMM System.  ORBCOMM Global is presently involving in
beta  testing the ORBCOMM System, and has successfully  used  the
ORBCOMM System to transmit data messages.

Orbital   expects  that,  using  at  least  26   satellites   and
appropriately located gateway Earth stations, the ORBCOMM  System
will provide communications availability generally exceeding  95%
during  each  24-hour  period  in the  United  States  and  other
temperate  zones  in  the Northern and Southern  hemispheres  and
exceeding  75%  of each 24-hour period in the equatorial  region.
Equatorial  region  availability could be improved  to  generally
exceed 90% with an additional plane of eight satellites.  Outages
will  be  dispersed in brief intervals over the  24-hour  period,
thereby  minimizing  the  effect of  any  unavailability  of  the
system.  The ORBCOMM System will only be available in areas where
appropriate licenses have been obtained and generally only  where
there  is  a proximate gateway Earth station and network  control
centre.

The  ORBCOMM System is being constructed and implemented  in  two
phases:   the ORBCOMM Phase 1 System, consisting of the satellite
control  centre, the United States network control  centre,  four
United   States   gateway  Earth  Stations  and   two   MicroStar
satellites; and the ORBCOMM Phase 2 System, consisting of  up  to
an  additional  34  MicroStar satellites.  The  ORBCOMM  Phase  1
System  satellites were launched in April 1995, and Phase  1  has
been  substantially completed.  Subject to the ability of ORBCOMM
Global to secure sufficient financing and completion of satellite
development and production in accordance with current  schedules,
Orbital  believes that the ORBCOMM Phase 2 System could be  fully
operational in late 1997.

Development and Financing.  Effective June 30, 1993, ORBCOMM  and
Teleglobe  Mobile formed a partnership, ORBCOMM Global,  for  the
design, development, construction, testing and operation  of  the
ORBCOMM  System, and formed two marketing partnerships to  market
the  ORBCOMM  System  in the United States  and  internationally.
ORBCOMM  USA,  L.P.  ("ORBCOMM USA")  and  ORBCOMM  International
Partners,  L.P.  ("ORBCOMM International,  "  and  together  with
ORBCOMM USA, the "Marketing Partnerships") each has the exclusive
right  to  market  the ORBCOMM System in the  United  States  and
internationally,  respectively.  Also effective  June  30,  1993,
Orbital  entered  into  an arm's length  agreement  with  ORBCOMM
Global  pursuant  to  which Orbital had  responsibility  for  the
overall design, development and integration of the ORBCOMM System
(the  "System Agreement").  The System Agreement was replaced  by
the  ORBCOMM System Procurement Agreement between ORBCOMM  Global
and   Orbital,   dated  September  12,  1995  (the   "Procurement
Agreement").

The  Phase  1  System was designed, constructed  and  implemented
pursuant  to  the  System Agreement.  The  Procurement  Agreement
provides  that  Orbital will, among other things,  construct  and
launch  24 satellites, and construct an additional 10 satellites,
for the ORBCOMM Phase 2 System.  Under the Procurement Agreement,
Orbital  is  providing  satellites and launch  services  and  the
remaining  work  to be done on the U.S. satellite control  centre
and U.S. gateway Earth stations on a fixed-price basis.

Construction and implementation of the ORBCOMM Phase 1 System  in
the   United  States  cost  approximately  US$65  million,   with
US$55  million and US$10 million contributed by Orbital  (through
ORBCOMM)  and  Teleglobe Mobile, respectively.  Teleglobe  Mobile
and  Orbital (through ORBCOMM) are obligated to increase each  of
their aggregate investment in ORBCOMM Global to US$85 million and
US$75 million, respectively.


Under  ORBCOMM  Global's  partnership agreement,  action  by  the
partnership  generally requires the approval of general  partners
holding   a  majority  of  the  participating  interests   (i.e.,
interests  participating in profits and losses). Each of  ORBCOMM
and  Teleglobe Mobile is a general partner of ORBCOMM Global  and
holds 50% of the participating interests in ORBCOMM Global,  with
the result that the approval of both Orbital and Teleglobe Mobile
is  necessary for ORBCOMM Global to act.  ORBCOMM holds  directly
and  indirectly a 51% participating interest in ORBCOMM  USA  and
Teleglobe   Mobile   holds  directly   and   indirectly   a   51%
participating interest in ORBCOMM International, with the  result
that  ORBCOMM  acting alone generally controls the  operation  of
ORBCOMM USA, and Teleglobe Mobile acting alone generally controls
the operation of ORBCOMM International.

Although   construction  of  the  ORBCOMM  Phase  1   System   is
substantially  completed, development  and  construction  of  the
ORBCOMM  Phase 2 System is in an early stage and the actual  cost
of  the  system,  schedule and the amount and  structure  of  the
anticipated  investment in ORBCOMM Global may vary  significantly
from   current   estimates.    Orbital   expects   that   design,
construction  and  implementation in the  United  States  of  the
ORBCOMM   Phase   2   System  will  require  total   capital   of
approximately  US$160  million,  bringing  the  total   estimated
required   capital  for  the  ORBCOMM  System  to   approximately
US$235  million.   ORBCOMM  Global  may  seek  additional  equity
contributions  and/or  bank  or other  debt  financing.   ORBCOMM
Global has already obtained asset-based financing of US$5 million
to  fund  a portion of its development and startup costs for  the
ORBCOMM  Phase 2 System.  Orbital has guaranteed ORBCOMM Global's
outstanding  indebtedness,  and  Orbital  or  Teleglobe  may   be
required  to  guarantee or provide credit support  in  connection
with   additional   indebtedness  incurred  by  ORBCOMM   Global.
Teleglobe  Mobile  has obtained a US$44 million  commitment  from
Technologies    Resources   Industries    Bhd.,    a    Malaysian
telecommunications  company, to acquire up to  30%  of  Teleglobe
Mobile's  interest in ORBCOMM Global.  Orbital has been  informed
that   Teleglobe   Mobile  may  seek  additional   investors   to
participate in its investment in ORBCOMM Global.

In  the event that ORBCOMM Global does not otherwise receive  the
necessary  capital, implementation and commercial development  of
the  ORBCOMM  System may be delayed, significantly restricted  or
possibly abandoned, and Orbital could be required to expense part
or  all  of  its investment in the ORBCOMM System.  In  addition,
start-up  of the ORBCOMM System will produce significant  ORBCOMM
Global  operating losses for several years.  Even if the  ORBCOMM
System  is fully implemented, there can be no assurance  that  an
adequate  market will develop for ORBCOMM System  services,  that
ORBCOMM Global will achieve profitable operations or that Orbital
will  recover  any of its past or anticipated investment  in  the
ORBCOMM System.  Because Orbital has a 50% participating interest
in  ORBCOMM  Global, Orbital expects to recognize  its  pro  rata
share of ORBCOMM Global profits and losses.

Regulatory Approvals.  In October 1994, ORBCOMM became the  first
company  to be awarded full U.S. Federal Communication Commission
("FCC")  authority to construct, launch and operate  a  low-Earth
orbit  satellite-based messaging and data communications  network
in  the  United  States.  This license, which provides  that  the
ORBCOMM System must be constructed within six years from the date
the  license was granted, extends for a period of ten years  from
the  date  the first ORBCOMM System satellite became operational.
At  the  end of the seventh year of the ten-year term, a  renewal
application  must  be filed with the FCC.  ORBCOMM  has  retained
control   over  applicable  FCC  licences  consistent  with   FCC
regulations.   As  with  any  such license,  the  ORBCOMM  System
license may be revoked and a license renewal application  may  be
denied  for  cause.  In late 1994, two other applicants  for  FCC
licenses similar to that awarded to ORBCOMM petitioned the FCC to
reconsider  the  grant  of the license to ORBCOMM.   ORBCOMM  has
opposed  the  petitions, which Orbital and  ORBCOMM  believe  are
without  merit.   In  addition, for  the  ORBCOMM  System  to  be
operated in other countries throughout the world, Orbital or  the
foreign  licensees  must  obtain  from  the  appropriate  foreign
regulatory  bodies authority to do so.  Orbital anticipates  that
the  cost of these activities will be borne primarily by  foreign
licensees.   ORBCOMM International has entered  into  preliminary
agreements  with 19 candidate licensees serving 66  countries  to
seek  such  licenses  and  to  initiate  country-specific  market
development  in  such countries.  There can be no assurance  that
Orbital  or  foreign licensees will be granted  all  licenses  or
approvals  necessary to operate the ORBCOMM System in  any  other
country.

ORBIMAGE  Remote Sensing and Imaging Systems.  Orbital, primarily
through  ORBIMAGE, is currently seeking to develop and  market  a
broad  range  of  information services to  identify  and  monitor
global environmental changes and to collect and disseminate other
remote  sensing information.  Small Earth-viewing satellites  and
related  sensors and instruments to be placed in  relatively  low
orbits  are  expected  to offer cost-efficient  data  collection,
daily  global  coverage and high-resolution imaging services  for
government and commercial uses.

In   April   1995,  ORBIMAGE's  first  MicroStar  satellite   was
successfully  launched to monitor lightning  and  severe  weather
patterns  for  NASA.   In  March 1991,  Orbital  entered  into  a
contract  with  NASA  to provide worldwide, daily  ocean  imagery
using   Orbital's  SeaStar  environmental  monitoring   satellite
system,  based  on  the PegaStar spacecraft.   Orbital  plans  to
develop,  produce,  launch  and operate  the  SeaStar  system  to
deliver high-quality multi-spectral ocean imagery for up to  five
years,  currently scheduled to commence during 1996.  In addition
to  providing  unprocessed real-time ocean data to NASA,  Orbital
plans  to process and package the data received from SeaStar  and
to  use value-added resellers and other marketing agents to  sell
the  SeaStar data to other U.S. Government users and to potential
domestic   and   international  customers  such   as   commercial
fishermen, oil and gas companies, ocean transportation  companies
and oceanographers.

ORBIMAGE  is developing and marketing other small satellite-based
Earth  observation,  remote sensing and environmental  monitoring
services  using,  among  other  things,  Orbital's  PegaStar  and
MicroStar   spacecraft  platforms,  Pegasus  and  Taurus   launch
vehicles, space sensors and instruments and other space products.
Services to be provided by ORBIMAGE could include high-resolution
optical  imaging  of  land  surfaces for  geographic  information
services,  mapping  and  news-gathering,  sensing  of  ocean  and
atmospheric  conditions and measuring of ozone and other  gaseous
concentrations   in  the  atmosphere.   ORBIMAGE   is   currently
exploring potential strategic arrangements for the development of
several remote sensing businesses, with Orbital providing  launch
services, spacecraft and other related products.  There can be no
assurance  that ORBIMAGE will be able to conclude such  strategic
arrangements  or develop profitable commercial Earth observation,
remote sensing or environmental monitoring businesses.

Satellite  Tracking Systems.  Orbital's ground tracking  systems,
installed at approximately 70 sites around the world, consist  of
meteorological and satellite tracking and telemetry stations that
are  used  to  collect weather data and to communicate  with  and
control  orbiting  spacecraft.  Orbital's current  customers  for
satellite  tracking  systems include Lockheed Martin  Corporation
("Lockheed Martin"), ORBCOMM and Orbital's SeaStar project.  As a
result  of  the Arrangement, Orbital is exploring the feasibility
of combining its satellite tracking systems operations with those
of MDA.

Competition

Orbital  believes that competition for sales of its products  and
services  is  based  on price, performance  and  other  technical
features, reliability, scheduling and customization.

The  primary  competition to the Pegasus and Taurus  vehicles  is
expected   to   come  from  the  smaller  and   larger   classes,
respectively, of LLV launch vehicles currently being developed by
Lockheed  Martin.  The LLV had an unsuccessful  first  flight  in
August 1995. Direct competition to the Taurus vehicle also  comes
from   EER   Systems'   Conestoga  launch   vehicle.    Potential
competition  to the Pegasus may come from launch systems  derived
from  surplus ballistic missiles that could be made available  by
the  U.S.  Government  and various foreign governments  including
Russia.   In  addition,  the  X-34  reusable  launch  vehicle  is
expected  to  compete with, and eventually replace, the  Pegasus.
Competition  for  Taurus could also come from  surplus  Titan  II
launch   vehicles,   although  Titan  II  production   has   been
discontinued  and  only  a limited inventory  remains.   Indirect
competition to the Pegasus and Taurus vehicles also exists in the
form  of  secondary  or  "piggyback" payload  capacity  on  large
boosters  such  as  Ariane, Titan, Long March and  Proton  launch
vehicles.   While secondary payloads offer a low-cost  method  of
launching satellites in some cases, the secondary status  of  the
payload often requires customers to accept less desirable orbits,
"standby" launch scheduling and potentially more complicated  and
costly payload integration procedures.

Orbital's  suborbital  launch vehicles,  spacecraft  systems  and
payloads,  satellite-based services and  space  support  products
compete  with  products  and services  produced  or  provided  by
numerous  companies and government entities.  Orbital's  airborne
and ground-based electronics, data management systems and defence-
oriented   avionics  products  face  competition   from   several
established   manufacturers.    Orbital's   space   sensors   and
instruments  face  competition from a  number  of  companies  and
university   research  laboratories  capable  of  designing   and
producing space instruments.

The ORBCOMM System will face direct and indirect competition from
numerous   existing   and  potential  alternative   communication
products  and  services from various large and  small  companies,
ranging  from one-way tower-based data and messaging services  to
sophisticated    two-way   satellite-based   data    and    voice
communications  services.  Depending on the  requirement  of  the
specific  market,  the ORBCOMM System may both compete  with  and
complement existing services such as one-way and two-way  paging,
cellular  data,  specialized mobile radio and  private  networks.
ORBIMAGE  may  face competition from private and U.S.  government
entities  that  provide satellite-based and other  land  imaging,
environmental  monitoring and atmospheric sensing products.   GPS
satellite-based navigation and positioning products  manufactured
by  Magellan face competition from several other producers of GPS
receivers,  such  as Garmin International and Trimble  Navigation
Ltd.  Orbital believes that Magellan's success will depend on its
ability  to  continue  to  develop new  lower-cost  and  enhanced
performance  products and to enter into and develop  new  markets
for GPS receivers.

Many  of  Orbital's competitors are larger and have substantially
greater  resources  than Orbital.  Furthermore,  the  possibility
exists  that  other domestic or foreign companies or governments,
some  with  greater experience in the space industry and  greater
financial  resources than Orbital, will seek to produce  products
or  services  that compete with those of Orbital,  including  the
Pegasus  and  Taurus launch vehicles, various  suborbital  launch
vehicles,  PegaStar, MicroStar and other satellite  systems,  GPS
receivers  and  ORBCOMM and other satellite services.   Any  such
foreign  competitor could benefit from subsidies from,  or  other
protective  measures  by,  its home  country.   In  addition,  in
response  to  reductions in the U.S. defence budget, Orbital  may
face  competition from companies, such as missile  manufacturers,
that  could attempt to adapt existing or future products for non-
defence, space or suborbital launch applications.

Research and Development

Orbital  believes that its future success will depend in part  on
its  ability to continue to conceive and develop new products and
services  and enhance existing products on a more rapid and  less
expensive  basis  than  its  competitors.   Accordingly,  Orbital
expects  to  continue to invest in product-related  research  and
development,  to conceive and develop new products and  services,
to  enhance existing products and to seek customer and  strategic
partner   investments   in  these  products.    These   strategic
relationships have included, and may include in the future, joint
development   arrangements,   joint   venture   investments   and
acquisitions of strategic product lines and businesses.

Orbital's  research  and development expenses,  excluding  direct
customer-funded  development, were approximately  US$8.8  million
for  the six months ended June 30, 1995 and approximately US$14.4
million, US$14.9 million, and US$10.6 million for the years ended
December  31,  1994,  1993  and  1992,  respectively.   Orbital's
research and development expenses during 1995 have been and  will
be  primarily  for  new  or modified launch  systems,  spacecraft
programs,  including possible ORBIMAGE projects,  and  satellite-
based navigation and positioning products.

Backlog and Contracts

Orbital's   firm  backlog  at  June  30,  1995   and   1994   was
approximately  US$495  million and US$256 million,  respectively.
As  of June 30, 1995, approximately 60% of Orbital's backlog  was
with  the  U.S. Government and its agencies or from  subcontracts
with  the  U.S. Government's prime contractors.  Backlog consists
of  aggregate contract values for firm product orders,  excluding
the  portion  previously included in operating  revenues  on  the
basis  of  percentage  of  completion accounting,  and  including
government  contracts awarded but not signed and orders  not  yet
funded  in  the  amounts of approximately US$140  million  as  of
June  30,  1995.   Approximately US$385  million  of  backlog  at
June 30, 1995 is currently scheduled to be performed beyond 1995.
Backlog excludes unexercised contract options having an aggregate
potential  contract  value  at June  30,  1995  of  approximately
US$795 million.

A  substantial portion of Orbital's revenues have been  generated
primarily  under fixed-price incentive fee, firm fixed-price  and
cost-plus-fee  U.S. government contracts.  Fixed-price  incentive
fee contracts are long-term contracts with specified cost, profit
and  price targets.  To the extent a contractor incurs less costs
than targeted, the contractor's profit will be increased based on
contractual  incentives.   In  this  manner,  the  contractor  is
encouraged to keep costs at a minimum and, as a reward,  realizes
additional  profit.   The  U.S.  Government,  by  virtue  of  the
contractor's  reduced costs, offset in part by increased  profit,
realizes a reduced price for the product or service.  Firm-fixed-
price contracts are long-term contracts with fixed stated prices.
The  contractor bears the burden of cost increases  and  realizes
the  reward  of  cost  savings.  Cost-plus-fee  contracts,  which
include    cost-reimbursable    contracts,    cost-plus-fixed-fee
contracts, cost-plus-award-fee contracts and cost-plus-incentive-
fee   contracts,  are  long-term  contracts  that   reimburse   a
contractor  for  all  costs incurred in the  performance  of  the
contract  with  various  contractual fee arrangements,  including
fixed  fees, award fees based on specific contractor performance,
and incentive fees based on contractor cost performance.

Orbital  uses the percentage of completion method of  accounting,
whereby  revenue is recognized based on actual costs incurred  in
relation  to  total estimated costs to complete the  contract  or
based  on  specific delivery terms and conditions, with incentive
and award amounts included in revenue or expense based on ongoing
estimates of expected incentive or award fees.  Unforeseen events
and  circumstances  can  alter Orbital's estimate  of  the  costs
associated with a particular contract and any related  profit  or
incentive  or award fee.  To the extent cost overruns  cannot  be
passed on to Orbital's customers, they could materially adversely
affect Orbital's results of operations.

All  of Orbital's U.S. Government contracts and, in general,  its
subcontracts   with  the  U.S.  Government's  prime  contractors,
provide that such contracts may be terminated at will by the U.S.
Government  or the prime contractor, respectively.   Furthermore,
any  of these contracts may become subject to a government-issued
stop  work  order  under  which Orbital is  required  to  suspend
production.   In the event of a termination at will,  Orbital  is
normally  entitled  to  the purchase price for  delivered  items,
reimbursement  for allowable costs for work in  process,  and  an
allowance for reasonable profit thereon or adjustment for loss if
completion of performance would have resulted in a loss.  Orbital
has experienced several contract suspensions and terminations  in
the past, and there can be no assurance that such terminations or
stop work orders will not occur in the future.

During  1994,  1993  and 1992, approximately 60%,  70%  and  80%,
respectively,  of  Orbital's total annual revenues  were  derived
from  contracts with the U.S. Government and its agencies or from
subcontracts   with  the  U.S.  Government's  prime  contractors.
Orbital's  government contracts are subject to regular audit  and
periodic  reviews  and  may be modified,  increased,  reduced  or
terminated in the event of changes in government requirements  or
policies,  Congressional appropriations and program progress  and
scheduling.   Orbital  believes that any  adjustments  likely  to
result from pending inquiries or audits of its contracts will not
have  a  material adverse impact on Orbital's financial condition
or  results of operation.  Since Orbital's inception, it has  not
experienced  any  material adjustments as a result  of  any  such
inquiries or audits.  U.S. Government curtailment of expenditures
for  space  research  and development and  related  products  and
services  could  have  a  material adverse  effect  on  Orbital's
revenues and results of operations.

Properties

In  1993,  Orbital  entered into a 12-year  lease  agreement  for
approximately 100,000 square feet of office and engineering space
in  Dulles, Virginia, which serves as its corporate headquarters.
In  1994,  Orbital  completed construction  of  an  approximately
30,000   square-foot  satellite  engineering  and   manufacturing
facility on land adjacent to the Dulles office facility.  Orbital
also   leases  approximately  320,000  square  feet  of   office,
engineering  and  manufacturing space  in  Germantown,  Maryland;
312,000  square  feet  of office, engineering  and  manufacturing
space in Chandler, Arizona; approximately 135,000 square feet  of
office,   engineering   and  manufacturing   space   in   Pomona,
California;   approximately  40,000  square   feet   of   office,
engineering and manufacturing space in San Dimas, California; and
approximately  25,000  square  feet  of  manufacturing  space  in
Mexicali,  Mexico.   Orbital  leases other  small  facilities  or
offices   in   Huntsville,  Alabama;  Edwards  Air  Force   Base,
California; Vandenberg Air Force Base, California; and Greenbelt,
Maryland.  Although completion of Orbital's existing and  pending
contracts  may  in  the  future require additional  manufacturing
capacity,  Orbital  believes  that its  existing  facilities  are
adequate for its near- and medium-term requirements.

Environmental Regulation

Orbital's  operations are subject to a variety of Federal,  state
and  local  environmental regulations, including laws  regulating
air  and  water  quality and hazardous materials and  regulations
implementing  those laws.  Orbital is one of several  potentially
responsible parties involved in a California mandated clean-up of
a  manufacturing  facility  near  Salinas,  California.   Through
June  30,  1995,  Orbital  and two other potentially  responsible
parties  have shared certain investigation and monitoring  costs,
resulting   in   total  Orbital  expenditures   after   insurance
recoveries of approximately US$85,000.  Orbital does not  believe
that   its  total  exposure  in  this  clean-up,  or  that  other
compliance by it with applicable environmental regulations,  will
have a material adverse effect on its operations.

Insurance

Orbital  maintains  a US$100 million aviation products  liability
policy that insures Orbital against certain liabilities to  third
parties  that  might arise in connection with the  production  or
operation  of  a  number of its products and generally  purchases
launch liability insurance with respect to certain liabilities to
third  parties  that  might arise in connection  with  a  launch.
Orbital  also  maintains a commercial general liability  umbrella
policy of US$50 million to insure Orbital against any third party
claims  associated  with its manufacturing or business  ventures.
In  addition, under certain of its government contracts,  Orbital
is  indemnified by the U.S. Government against certain  potential
third-party  liabilities resulting from launch  or  operation  of
space  launch vehicles and for commercial launches is indemnified
against  certain of such liabilities under launch  licenses  with
the U.S. Department of Transportation.  In circumstances in which
Orbital has provided mission success warranties, depending on  an
assessment  of its exposure and the availability and  pricing  of
insurance,  Orbital generally seeks to purchase  mission  success
insurance,  which  provides coverage  with  respect  to  contract
losses in the event its launch vehicles or other products fail to
perform  and the mission is not completed successfully.   Orbital
separately maintains both property (aircraft hull) and  liability
insurance on the Lockheed L-1011 aircraft it is currently leasing
for its Pegasus program.

Orbital  reviews  its insurance coverage from time  to  time  and
considers  changes to its insurance coverage in response  to  the
introduction  and  operation  of  new  products.   The  insurance
carried  by  Orbital and its indemnity rights  against  the  U.S.
Government  and other parties do not extend to all  of  Orbital's
products and services, may not cover all potential risks and  may
not  be effective to protect Orbital against all potential claims
or  losses.  In addition, there can be no assurance that  mission
success  insurance will be available at premium  levels  that  in
Orbital's  judgment justify purchase of such  insurance  or  that
such  insurance  will  be  available in all  instances  in  which
Orbital has provided mission success warranties.

Litigation

To its knowledge, Orbital is not a party to any legal proceeding,
the  outcome  of  which would materially impact its  business  or
operations.

Management's  Discussion and Analysis of Financial Condition  and
Results of Operations

Overview

A  significant portion of Orbital's revenues are generated  under
fixed-price  incentive fee, firm fixed-price,  and  cost-plus-fee
contracts with various agencies of the U.S. Government, including
NASA, the U.S. Air Force, ARPA, the U.S. Army, the U.S. Navy  and
BMDO.   Orbital  recognizes  revenues  using  the  percentage  of
completion  method of accounting, whereby revenue  is  recognized
based  on  actual  costs incurred in relation to total  estimated
costs  to  complete  the contract or based on  specific  delivery
terms  and conditions.  In the case of fixed-price incentive  fee
contracts, the final revenue amount can be increased or decreased
in  accordance with cost incentive provisions that measure actual
financial performance against established targets.  The incentive
fee is included in revenue at the time the amount of such fee can
reasonably  be  determined.  In the case of cost-plus  award  fee
contracts,  revenues  are  recognized  to  the  extent  of  costs
incurred plus a proportionate amount of a base fee fixed  at  the
inception of the contract, if any.  The award fee is included  in
revenue   as  work  is  performed  based  on  Orbital's  on-going
estimates of the amount of the fee to be awarded.  To the  extent
that   estimated  costs  of  completion  are  adjusted,   revenue
recognized  from  a particular contract will be affected  in  the
period of the adjustment.

Orbital is accounting for its investment in ORBCOMM Global  using
the  equity  method of accounting and will continue  to  use  the
equity  method as long as Orbital's interest in the  profits  and
losses  of  ORBCOMM Global does not exceed the current  50%.   In
accordance   with  the  equity  method  of  accounting,   Orbital
consolidates  100%  of  the revenues earned  and  costs  incurred
pursuant to the System Agreement and Procurement Agreement.   See
"Information on Orbital - Communications and Information  Systems
- -  Development and Financing."  Orbital also recognizes as equity
in  earnings (losses) of affiliates its pro rata share of ORBCOMM
Global's profits and losses.  During construction of the  ORBCOMM
System,  ORBCOMM Global is capitalizing substantially all  system
construction  costs,  including amounts  paid  under  the  System
Agreement  and  Procurement Agreement.   To  the  extent  ORBCOMM
Global  capitalizes its purchases under these agreements, Orbital
eliminates  as equity in earnings (losses) of affiliates  50%  of
Orbital's profits and losses thereunder.

Orbital  acquired Magellan on December 28, 1994, in a transaction
accounted  for  as a pooling of interests.  Orbital's  historical
financial information has been restated to effect the pooling  of
interests with Magellan as of the earliest period presented.   On
August  11,  1994, Orbital acquired Fairchild,  a  subsidiary  of
Matra  Aerospace,  Inc.,  in a transaction  accounted  for  as  a
purchase business combination.  Fairchild's results of operations
for  the  nineteen-week period ended December 31, 1994 have  been
included in Orbital's consolidated results of operations for  the
year   ended  December  31,  1994.   Orbital  acquired   ASO   on
September 17, 1993, in a transaction accounted for as a  purchase
business  combination.   ASO's  results  of  operations  for  the
fourteen-week  period ended December 31, 1993 have been  included
in  Orbital's  consolidated results of operations  for  the  year
ended December 31, 1993.

Adoption of New Accounting Standard

The  Financial  Accounting Standards Board recently  issued  SFAS
No.  121, "Accounting for the Impairment of Long-Lived Assets and
Long-Lived  Assets  to  be Disposed Of" ("SFAS  121")  which  (i)
requires that long-lived assets "to be held and used" be reviewed
for  impairment  whenever  events  or  changes  in  circumstances
indicate  that  the  carrying amount  of  an  asset  may  not  be
recoverable, (ii) requires that long-lived assets "to be disposed
of"  be  reported at the lower of carrying amount or  fair  value
less  cost  to sell, and (iii) provides guidelines and procedures
for measuring an impairment loss that are significantly different
from existing guidelines and procedures.

Orbital  adopted  the provisions of SFAS 121 during  the  quarter
ended  June 30, 1995.  As a result, as of January 1, 1995 Orbital
recorded  a  cumulative  adjustment for a  change  in  accounting
principle  of  approximately  US$4.2  million  related   to   the
impairment  in  the  carrying amount  of  certain  assets  to  be
disposed  of  that supported its orbit transfer  vehicle  product
line.

The  following table shows Orbital's revenues, gross  profit  and
gross  profit margin, by major product category, for each of  the
three years ended December 31, 1992, 1993 and 1994.

OMITTED:  See Management's Discussion and Analysis in the Company's
Annual Report on Form 10-K filed with the SEC on March 29, 1995.


Results  of Operations for the Six-Month Periods Ended  June  30,
1995 and 1994

Revenues.   Orbital's  revenues for the six-month  periods  ended
June  30,  1995  and 1994 were US$132,930,000 and  US$98,675,000,
respectively.

Space   launch   vehicle   revenues   were   US$11,965,000    and
US$29,762,000 for the six-month periods ended June 30,  1995  and
1994,  respectively.  The significant decrease in revenues during
the  periods is attributable primarily to the continuing  effects
of  production delays caused by Orbital's failed first launch  of
its  new Pegasus XL launch vehicle in June 1994, and was impacted
to  some extent by the failed second launch of the Pegasus XL  in
June 1995. Orbital expects revenues during the rest of 1995 to be
less  than 1994 as a result of the ongoing failure review process
and resulting schedule delays.  Sales of space launch vehicles to
ORBCOMM  Global were US$1,452,000 and US$4,150,000 for  the  1995
and 1994 six-month periods, respectively.

Revenues   from   suborbital   launch   vehicle   products   were
US$11,492,000  and US$11,626,000 for the six-month periods  ended
June  30, 1995 and 1994, respectively.  While suborbital revenues
have  decreased significantly during the past few years  as  U.S.
Government  defence  spending has been reduced,  Orbital  expects
1995  revenues  to remain approximately consistent  with,  or  to
increase slightly from, revenue levels achieved in 1994.

For  the  six  months  ended  June 30, 1995,  spacecraft  systems
revenues  increased  to US$28,901,000 from US$11,043,000  in  the
same period in 1994.  The increase in spacecraft system sales  is
primarily  as  a  result  of additional revenues  generated  from
Orbital's  Germantown operations, acquired in August  1994.   The
1995  and  1994  six-month  periods  included  US$3,395,000   and
US$4,496,000,  respectively, in sales of MicroStar spacecraft  to
ORBCOMM  Global.   Space  sensors  and  instruments  sales   were
US$6,547,000  and  US$8,773,000 for the 1995 and  1994  six-month
periods, respectively, and are expected to remain lower than 1994
levels throughout 1995.

Revenues  from  defence  electronics and avionics  products  were
approximately US$29,790,000 and US$5,860,000 in the 1995 and 1994
six-month periods, respectively.  Orbital acquired these products
as  part  of  the  August  1994  Fairchild  acquisition  and  the
September 1993 acquisition of ASO.

Revenues  from  sales  of  navigation  and  positioning  products
increased to US$26,459,000 for the six months ended June 30, 1995
as  compared to US$18,553,000 for the 1994 period, primarily  due
to increased unit sales offset, in part, by lower unit prices for
GPS navigators.

Revenues from Orbital's newly established Advanced Projects Group
were  US$9,404,000 during the first half of 1995 as a  result  of
work  performed under the Cooperative Agreement with NASA awarded
in  March  1995  for the development of the X-34  small  reusable
launch vehicle and work under a contract with ARPA, completed  in
April  1995,  for  the  study of a new advanced  unmanned,  long-
duration, high-flying aircraft.

Gross  Profit.   Gross  profit depends on a  number  of  factors,
including  Orbital's  mix of contract types  and  costs  incurred
thereon in relation to estimated costs.  Gross profit for the six-
month periods ended June 30, 1995 and 1994 was US$35,637,000  and
US$25,052,000, respectively.  Gross profit margin as a percentage
of  sales  was  approximately 26.8% and 25.4%, for the  six-month
periods  ended  June  30,  1995  and  1994,  respectively.    The
increased   gross  profit  margin  during  1995   was   primarily
attributable  to  increased margins for  spacecraft  systems  and
navigation  and  positioning products, offset  in  part  by  cost
increases  on the Pegasus program as a result of the  Pegasus  XL
failures  in  June of 1994 and 1995.  Orbital believes  that  its
gross  profit  margin  for the remainder of  1995  will  increase
slightly as compared to the first half of 1995.

Research  and  Development  Expenses.  Research  and  development
expenses  represent  Orbital's  self-funded  product  development
activities,   and  exclude  direct  customer-funded  development.
Research and development expenses for the 1995 and 1994 six-month
periods   were   US$8,764,000  and  US$6,506,000,   respectively.
Research and development expenses in 1995 relate primarily to the
development   of   new  or  improved  navigation   products   and
development efforts on Orbital's Pegasus XL program, and  include
estimated  expenses  related to the recent  Pegasus  XL  failure.
Orbital expects its research and development expenditures for the
rest of 1995 to be consistent with second half 1994 expenditures.

Selling,  General and Administrative Expenses.  Selling,  general
and  administrative  expenses include  the  costs  of  marketing,
advertising, promotional and other selling expenses  as  well  as
the  costs  of the finance, administrative and general management
functions   of  Orbital.   Selling,  general  and  administrative
expenses  for  the six months ended June 30, 1995 and  1994  were
US$22,707,000 (or 17.1% of revenues) and US$14,472,000 (or  14.7%
of revenues), respectively.  The increase in selling, general and
administrative  expenses  during 1995 as  compared  to  1994  was
primarily  attributable to expanded marketing efforts related  to
Orbital's  ORBCOMM project (US$3,304,000 of expenses in  1995  as
compared  to US$1,714,000 in 1994) and to various remote  sensing
systems  (US$408,000  of expenses in 1995 with  no  corresponding
expenses  in  1994), and to the August 1994 Fairchild acquisition
(US$12,188,000  of expenses in 1995).  Orbital  expects  selling,
general  and administrative expenses as a percentage of  revenues
during  the  remainder of 1995 to be less than  or  approximately
equal to those in the first half of 1995.

Interest  Income and Interest Expense.  Net interest expense  for
the  1995  six-month  period  was  US$1,887,000  as  compared  to
US$931,000 of net interest income for the 1994 six-month  period.
Interest  income  for the periods reflects interest  earnings  on
short-term  investments.   Interest  expense  is  primarily   for
outstanding  amounts on Orbital's revolving credit  facility,  on
Orbital's public debentures and, during 1995, on acquisition debt
incurred   in   connection  with  the   August   1994   Fairchild
acquisition.   Interest expense has been reduced  by  capitalized
interest  of US$2,533,000 and US$2,517,000 for the 1995 and  1994
six-month periods, respectively.

Equity  in  Earnings (Losses) of Affiliates.  Equity in  earnings
(losses)  of affiliates for the six-month periods ended June  30,
1995   and   June   30,  1994  of  US$362,000  and  (US$544,000),
respectively,  represents elimination of 50% of  the  profits  on
sales  to ORBCOMM Global, as well as Orbital's pro rata share  of
ORBCOMM Global's current period earnings and losses.  During  the
construction  phase of the project and prior to the  commencement
of   planned   operations,   ORBCOMM   Global   is   capitalizing
substantially all construction-related costs and is expensing  as
incurred all selling, general and administrative costs as  period
costs.

Provision for Income Taxes.  A provision for income taxes was not
necessary  for the six months ended June 30, 1995 given Orbital's
reported  operating  losses.   Orbital  recorded  an  income  tax
provision of US$917,000 for the six-month period ended  June  30,
1994.  Orbital records its interim income tax provisions based on
estimates  of  Orbital's  effective  tax  rate  expected  to   be
applicable  for the full fiscal year.  Estimated effective  rates
recorded  during interim periods may be periodically revised,  if
necessary, to reflect current estimates.

At December 31, 1994, Orbital had approximately US$50,000,000 and
US$900,000  of  net operating loss and tax credit  carryforwards,
respectively,  which are available to reduce  future  income  tax
obligations,  subject  to certain annual  limitations  and  other
restrictions.

Results of Operations for the Years Ended December 31, 1994, 1993
and 1992

Revenues.   Orbital's  revenues for  1994,  1993  and  1992  were
US$221,946,000, US$223,087,000 and US$204,190,000,  respectively.
Revenues in 1994 included approximately US$30 million in sales to
ORBCOMM Global, as compared to US$38 million in 1993.

Revenues  from Orbital's space launch vehicle products  decreased
from  US$55,987,000  in  1993  to  US$52,200,000  in  1994.   The
unexpected  decrease was primarily attributable to a  significant
delay  in  production of Orbital's Pegasus space  launch  vehicle
products  as a result of the June 1994 Pegasus XL launch failure.
Revenues from space launch vehicle products increased in 1993, as
compared  to  1992,  due to work performed on  Pegasus  contracts
awarded  in  1992 by BMDO and Brazil's national space agency  and
initial  work  performed on the commercial  contract  awarded  by
ORBCOMM Global.

Revenues  from  suborbital launch vehicle products  decreased  to
US$22,632,000  in  1994  as compared to  US$48,990,000  in  1993.
Revenues  from suborbital launch vehicle products also  decreased
in  1993  from 1992's record revenues of US$82,061,000.  Revenues
from suborbital launch vehicles, which are primarily purchased by
various agencies within the DoD for U.S. military purposes,  have
decreased significantly as defence spending throughout  the  U.S.
Government has been reduced.

Orbital's sole contract with NASA for its orbit transfer  vehicle
products was completed in 1993 after two successful launches.

Space and Electronics Systems revenues increased to US$88,305,000
in 1994 as compared to US$31,287,000 in 1993, due primarily to  a
full   year  of  sales  of  sensors  and  instruments  equal   to
US$28,482,000 following the September 1993 acquisition of ASO and
19  weeks  of  sales of spacecraft systems and  defence  avionics
equal  to US$44,998,000 following the August 1994 acquisition  of
Fairchild.  Space systems revenues increased to US$31,287,000  in
1993  from US$20,715,000 in 1992, primarily as a result of  sales
of  sensors and instruments and sales of MicroStar satellites  to
ORBCOMM Global.  Space systems revenues in 1992 consisted  solely
of sales of satellite systems to NASA and the U.S. Air Force.

Communications  and  Information Systems  revenues  decreased  to
US$58,808,000 in 1994 from US$71,391,000 in 1993.   The  decrease
was  attributable  primarily to a decrease in  sales  to  ORBCOMM
Global  of  US$10,455,000  as the initial  contract  for  network
software  neared completion, and a decrease in sales of satellite
tracking  systems  of  US$8,443,000  as  a  large  contract   was
completed  in  1994.  Sales of Magellan's satellite  navigational
instruments   were   US$37,144,000  in  1994   as   compared   to
US$32,900,000  in 1993 and US$29,557,000 in 1992.   The  increase
from  1993  was  due to a significant increase in the  number  of
products  sold  offset,  in  part, by lower  average  unit  sales
prices.    Communications   and  Information   Systems   revenues
increased  in 1993 as compared to 1992 as a result  of  sales  of
network software and satellite tracking systems to ORBCOMM Global
under  a  contract  awarded in 1993  and  as  a  result  of  work
performed  on a large satellite tracking system contract  awarded
in late 1992.

Gross Profit.  Orbital's gross profit for 1994, 1993 and 1992 was
US$64,881,000,  US$52,883,000  and  US$45,529,000,  respectively.
Gross  profit  margin as a percentage of sales for those  periods
was  approximately 29.1%, 23.7%, and 22.3%, respectively.   Gross
profit margin during 1994 reflected higher profit margins on  ASO
and  Fairchild  products offset in part by  cost  growth  on  the
Taurus  space  launch  vehicle  development  program,  the  first
product  of  which  was  successfully  launched  in  March  1994.
Additionally, gross profit margin was decreased by cost growth on
the  Pegasus  program  as a result of the June  1994  Pegasus  XL
launch failure.

Research  and  Development  Expenses.  Research  and  development
expenses   during   1994,  1993  and  1992  were   US$14,389,000,
US$14,885,000  and  US$10,586,000,  respectively.   Research  and
development  spending  during 1994 and 1993  reflected  Orbital's
continued  development of its Pegasus XL and Taurus space  launch
vehicles  and  development  of  lower-cost  satellite  navigation
equipment.   In 1994, Orbital incurred approximately US$2,500,000
of  unexpected research and development costs related to the June
1994 failure of its Pegasus XL vehicle.

Selling,  General and Administrative Expenses.  Selling,  general
and   administrative  expenses  for  1994,  1993  and  1992  were
US$39,751,000 (or 17.9% of revenues), US$25,897,000 (or 11.6%  of
revenues) and US$28,615,000 (or 14.0% of revenues), respectively.
The  significant increase in selling, general and  administrative
expenses  and  its  related percentage of revenues  in  1994  was
attributable  to  a full year of ASO's expenses (US$4,666,000  in
1994,  or 16.8% of ASO's revenues), nineteen weeks of Fairchild's
expenses (US$6,409,000 in 1994, or 14.0% of Fairchild's revenues)
and  significant  selling,  general and  administrative  expenses
related  to  initial marketing activities for  Orbital's  ORBCOMM
project  (US$5,470,000  in 1994) offset in  part  by  significant
company-wide cost reduction initiatives adopted during  1994  and
1993.

Interest  Income and Interest Expense.  Net interest  income  was
US$37,000,  US$356,000 and US$738,000 for 1994,  1993  and  1992,
respectively.   Interest  income reflects  interest  earnings  on
short-term  investments  reduced  by  interest  expense  (net  of
capitalized interest of US$5,500,000, US$3,500,000 and US$850,000
in  1994, 1993 and 1992, respectively) for outstanding amounts on
Orbital's revolving credit facility, the public debentures and on
debt incurred in 1994 related to the Fairchild acquisition.

Equity in Earnings (Losses) of Affiliates.  Equity in earnings of
affiliates  in 1994 and 1993 primarily represents elimination  of
US$1,264,000 and US$2,436,000, respectively, of profits on  sales
to  ORBCOMM Global, due to ORBCOMM Global's capitalization of its
purchases  from  Orbital.  There were no sales to ORBCOMM  Global
prior to 1993.

Provision  for  Income  Taxes.   Orbital  adopted  SFAS  No.  109
effective January 1, 1993.  The cumulative effect on prior  years
of  this  change in accounting principle increased net income  in
1993  by  approximately US$200,000.  The effect of adopting  SFAS
109  on  income  from  continuing  operations  in  1993  was  not
material.

Orbital   recorded   income  tax  provisions   of   US$2,081,000,
US$2,288,000   and  US$1,630,000  for  1994,   1993   and   1992,
respectively.  Orbital's effective tax rate for these periods  of
approximately  28%  is primarily a result of  non-tax  deductible
goodwill amortization related to its acquisition of Space Data in
1988  and  Fairchild  in  1994,  offset  by  tax-exempt  interest
earnings and U.S. Federal research and experimental tax credits.

Liquidity and Capital Resources

Orbital's growth has required substantial capital to fund both an
expanding  business base and significant research and development
and  capital investment expenditures.  Additionally, Orbital  has
historically  made  strategic  acquisitions  of  businesses   and
routinely  evaluates  potential acquisition candidates.   Orbital
expects  to  continue  to pursue potential acquisitions  that  it
believes would augment its marketing, technical, manufacturing or
financial capabilities.  Orbital has funded these requirements to
date, and expects to fund its requirements in the future, through
cash  generated  by operations, working capital loan  facilities,
asset-based  financings, joint venture arrangements, and  private
and public equity and debt offerings.

During  the quarter ended June 30, 1995, Orbital entered  into  a
US$20  million  fixed-rate unsecured debt  financing  arrangement
with  a private insurance company.  The debt has a six-year  term
and  bears  interest  at 10 1/2% per annum.   The  debt  arrangement
restricts the payment of dividends and contains certain covenants
with  respect  to Orbital's working capital, fixed charge  ratio,
leverage  ratio  and tangible net worth.  Additionally,  in  June
1995,  Orbital  completed  a private  placement  of  two  million
Orbital  Common  Shares, receiving net proceeds of  approximately
US$32   million.   Orbital's  shares  were  placed  with  various
offshore institutional investors and the issuance was exempt from
public  registration  pursuant  to  Regulation  S  of  the   1933
Securities  Act,  as  amended.  In August  1994,  Orbital  issued
secured  notes  totalling approximately  US$24,200,000  to  eight
financial  institutions,  to  support  Orbital's  acquisition  of
Fairchild.    The  notes  have  an  average  interest   rate   of
approximately 8_% and generally mature on a monthly basis over  a
three- to five-year period.

Cash,   cash   equivalents   and  short-term   investments   were
US$39,817,000  at June 30, 1995, and Orbital had  short-term  and
long-term   debt   obligations   outstanding   of   approximately
US$106,955,000.   The  outstanding  debt  relates  primarily   to
advances  under Orbital's line of credit facility, secured  notes
issued  in  connection with the Fairchild acquisition,  unsecured
notes issued in 1995, fixed asset financings and Orbital's public
debentures.   During  the quarter ended June  30,  1995,  Orbital
converted,  at  a  premium,  approximately  US$3,000,000  of  its
convertible  debentures  at  the  request  of  certain  debenture
holders, issuing approximately 209,000 Orbital Common Shares.

Orbital's revolving credit facility provides for total borrowings
from   an  international  syndicate  of  six  banks  of   up   to
US$65,000,000, subject to a defined borrowing base  comprised  of
certain  contract  receivables.   Approximately  US$6,113,000  of
borrowings were outstanding under the facility at June 30,  1995,
against    an   available   facility   limit   of   approximately
US$25,491,000.   At June 30, 1995, the average interest  rate  on
outstanding  borrowings  under this  facility  was  approximately
8.2%.  Borrowings are secured by contract receivables and certain
other  assets.  The facility restricts the payment  of  dividends
and  contains certain covenants with respect to Orbital's working
capital,  fixed  charge ratio, leverage ratio  and  tangible  net
worth, and expires in September 1997.

Orbital's  operations used net cash of approximately US$8,466,000
in  the  six  months ended June 30, 1995.  Orbital also  invested
approximately  US$9,689,000 in the ORBCOMM  System  and  incurred
US$9,854,000   of  capital  expenditures  related  primarily   to
spacecraft production and test equipment.

Orbital  expects  that its 1995 capital needs  for  its  existing
operations, including its planned US$5,000,000 net investment  in
the  ORBCOMM System, will in part be provided by working capital,
cash   flows  from  operations,  credit  facilities,  asset-based
financings, customer financings and operating lease arrangements.
Additionally, Orbital intends to invest at least US$67,500,000 in
the X-34 program, which investment will be required over the next
four   years,  including  approximately  US$5,000,000  in   1995.
Orbital  believes  that it may require additional  equity  and/or
debt financing to fund fully its currently planned operations and
capital  requirements, to meet its potential increased investment
in the ORBCOMM System and to meet its investment requirements for
the X-34 program.

Management and Employees

Executive Officers and Directors

The  following  table  sets forth the name,  city  of  residence,
position  and  principal  occupation of  each  of  the  executive
officers and directors of Orbital as of September 1, 1995.  As of
September  29,  1995,  the executive officers  and  directors  of
Orbital beneficially owned, as a group, approximately 3.7% of the
outstanding Orbital Common Shares.
<TABLE>
<CAPTION>
                                             Principal
 Name and        Director  Position with      Occupation if
 Residence       Since     Orbital            Different than
                                             Office Held
<C>             <C>      <C>                <C>
 David W.        1982      Chairman of the    
 Thompson                  Board, President
 Reston,                   and Chief
 Virginia                  Executive Officer

 Bruce W.        1982      Executive Vice
 Ferguson                  President and
 Great Falls,              General Manager/
 Virginia                  Communications
                           and Information
                           Systems Group and
                           Director

 James R.        1992      Executive Vice
 Thompson                  President and
 Huntsville,               General
 Alabama                   Manager/Launch
                           Systems Group and
                           Director

 Jack A.         1994      Executive Vice
 Frohbieter                President and
 Germantown,               General
 Maryland                  Manager/Space and
                           Electronics
                           Systems Group and
                           Director
 
 Fred C. Alcorn  1983      Director           President, Alcorn
 Houston, Texas                               Oil & Gas and
                                              Alcorn
                                              Development
                                              (Real Estate)
 
 Kelly H. Burke  1984      Director           Chairman,
 Alexandria,                                  Stafford, Burke &
 Virginia                                     Hoaxer
                                              (Aerospace
                                              consulting)
 
 Daniel J. Fink  1983      Director           President, D.J.
 Potomac,                                     Fink Associates,
 Maryland                                     Inc.
                                              (Management
                                              consulting)
 
 Lennard A.      1993      Director           Professor and
 Fisk                                         Chairman,
 Ann Arbor,                                   Department of
 Michigan                                     Atmospheric,
                                              Oceanic, and
                                              Space Sciences,
                                              University of
                                              Michigan
  
 Jack L.         1993      Director           Professor of
 Kerrebrock                                   Aeronautics and
 Lincoln,                                     Astronautics,
 Massachusetts                                Massachusetts
                                              Institute of
                                              Technology
 
 J. Paul         1984      Director           Managing
 Kinloch                                      Director, Lehman
 Los Angeles,                                 Brothers
 California                                   (Investment
                                              Banking)
 
 Douglas S.      1983      Director           President and
 Luke                                         CEO, WLD
 Coral Gables,                                Enterprises, Inc.
 Florida                                      (Investments)
 
 John L.         1993      Director           Consultant
 McLucas
 Alexandria,
 Virginia
 
 Harrison H.     1983      Director           Consultant
 Schmitt
 Albuquerque,
 New Mexico
 
 Scott L.        1982      Director           Consultant
 Webster
 Chandler,
 Arizona
 
 Antonio L.                Executive Vice
 Elias                     President and
 McLean,                   General
 Virginia                  Manager/Advanced
                           Projects Group
 
 Carlton B.                Senior Vice
 Crenshaw                  President/Finance
 Herndon,                  and
 Virginia                  Administration
 
 Leslie C.                 Senior Vice
 Seeman                    President,
 Bethesda,                 General Counsel
 Maryland                  and Secretary
 
</TABLE> 

For  information  regarding executive and director  compensation,
and  a description of Orbital's stock option plans, reference  is
made   to  the  excerpt  from  Orbital's  Proxy  Statement  dated
March 27, 1995, attached as Annex "III" to this Proxy Circular.

Indebtedness of Directors and Officers

There  is no indebtedness owed by Orbital's directors or officers
to Orbital.

Employees

As  of  June  31,  1995  Orbital had  1,781  full-time  permanent
employees,  none  of  whom are covered by a collective-bargaining
agreement.

Description of Capital

Capitalization

The  following table sets forth the capitalization of Orbital  as
of June 30, 1995.
                                                 June 30,
                                                   1995
                                                  (US$ in
                                                thousands)
Long-term debt:                                              
    Long-term obligations, net of current          $ 19,203
    portion                                                
    10 1/2% Senior Notes due 2002                    20,000
    6 3/4% Convertible Subordinated Debentures     $ 56,000 
    due 2003
Total long-term debt                               $ 95,203
Shareholders' equity:                                        
    Preferred Shares, par value $0.01 per                    
    share: 10,000,000                                    --  
     authorized; no shares issued and                        
    outstanding                                              

    Common Shares, par value $0.01 per                  227
    share: 40,000,000                                 
     authorized; 22,636,357 shares issued             
    and outstanding                                 
     after adjusting for 15,735 shares in          
    treasury (1)

    Additional paid-in capital                      237,549
    Unrealized losses on short-term                    (221)
    investments
    Retained earnings (deficit)                      (1,941)
Total shareholders' equity                        $ 235,614
Total capitalization                              $ 330,817

Note:
(1)  Excludes  3,900,945  Orbital  Common  Shares  issuable  upon
     conversion  of  Orbital's  6 3/4%  Convertible  Subordinated
     Debentures  due  2003  and 1,661,146 Orbital  Common  Shares
     reserved for issuance pursuant to options outstanding as  of
     September 8, 1995 with exercise prices ranging from  US$7.50
     to US$22.00 per share.

Common Shares

Orbital has authorized 40,000,000 Common Shares, par value  $0.01
per  share  of  which approximately 22,636,357 are issued  as  at
June 30, 1995.  Holders of Orbital Common Shares are entitled  to
one  vote per share on all matters to be voted on by shareholders
including  the election of directors.  Subject to the  rights  of
holders  of  any  Orbital Preferred Shares that  may  be  issued,
holders  of  Orbital Common Shares are entitled to  receive  such
dividends  as may be declared from time to time by the  board  of
directors of Orbital from funds legally available therefor.  Upon
liquidation, dissolution or winding-up of Orbital, the holders of
Orbital  Common  Shares will be entitled  to  share  ratably  all
assets  available for distribution to shareholders after  payment
of  liabilities, subject to prior distribution rights of  holders
of  Preferred Shares then outstanding.  The Orbital Common Shares
have  no  preemptive  or conversion rights or other  subscription
rights.   There  are  no  redemption or sinking  fund  provisions
applicable to the Common Shares.

Preferred Shares

Orbital  has  authorized 10,000,000 Preferred Shares,  $0.01  par
value  per  share of which none are issued.  See "Special  Voting
Share"  below.   Orbital's  board  of  directors  is  authorized,
without any further action by the shareholders, to determine  the
rights,  preferences, privileges and restrictions of the unissued
Preferred Shares.

Special  Voting  Share.   In  connection  with  the  Arrangement,
Orbital's  Board  of  Directors  will  designate  the  Series   A
Preferred  Stock  as  a  series of  Preferred  Shares,  and  will
authorize  the  issue  of one Series A Preferred  Share,  as  the
Special  Voting  Share,  to  the Trustee  under  the  Voting  and
Exchange Trust Agreement.  Except as otherwise required by law or
Orbital's  Restated  Certificate of Incorporation  (the  "Orbital
Restated  Certificate"),  the holder of  record  of  the  Special
Voting  Share will have a number of votes equal to the number  of
Orbital  Common Shares issuable upon exchange of all  outstanding
Exchangeable  Shares  (not owned by Orbital or  its  Affiliates).
The holders of Orbital Common Shares and the Special Voting Share
will  vote  together as a single class on all matters, except  as
may  be  required  by  applicable  law.   In  the  event  of  any
liquidation, dissolution or winding up of Orbital, the holder  of
the  Special  Voting Share shall not be entitled to  receive  any
assets of Orbital available for distribution to its shareholders.
The  holder of the Special Voting Share shall not be entitled  to
receive dividends.  At such time as the Special Voting Share  has
no  votes attached to it because there are no Exchangeable Shares
outstanding  not owned by Orbital or its Affiliates, the  Special
Voting Share will be cancelled.

Dividend Policy

Orbital  has  never  paid a cash dividend on the  Orbital  Common
Shares.   Orbital currently intends to retain earnings  primarily
for  working  capital and product development and therefore  does
not  anticipate paying dividends in the foreseeable  future.   In
addition,  Orbital is subject to certain contractual restrictions
on its ability to pay dividends.

Transfer Agent

Orbital's  transfer  agent with respect  to  the  Orbital  Common
Shares  is  The  First  National Bank of  Boston.   Acquisition's
transfer  agent  with  respect  to  the  Exchangeable  Shares  is
expected to be Montreal Trust Company of Canada.

Independent Auditors

Orbital's independent auditors are KPMG Peat Marwick LLP.


                   INFORMATION CONCERNING MDA

Business

MDA was incorporated under the laws of Canada on February 3, 1969
by  letters  patent under the Canada Corporations Act.   MDA  was
subsequently continued under the CBCA on May 3, 1976.   The  head
and principal office of MDA is located at 13800 Commerce Parkway,
Richmond, British Columbia, V6V 2J3.

Subsidiary Companies

MDA owns 100% of the following active subsidiary companies:
                   INFORMATION CONCERNING MDA

Business

MDA was incorporated under the laws of Canada on February 3, 1969
by  letters  patent under the Canada Corporations Act.   MDA  was
subsequently continued under the CBCA on May 3, 1976.   The  head
and principal office of MDA is located at 13800 Commerce Parkway,
Richmond, British Columbia, V6V 2J3.

Subsidiary Companies

MDA owns 100% of the following active subsidiary companies:

Company                         Jurisdiction of
                                Incorporation

MacDonald Dettwiler             British Columbia
Technologies Ltd.

MacDonald Dettwiler             U.S.A.
Technologies Inc.

MacDonald Dettwiler Pty. Ltd.   Australia

MacDonald Dettwiler Limited     United Kingdom

PSC International (Europe)      United Kingdom
Limited

At  June  30, 1995 MDA owned 89.6% of Earth Observation  Sciences
Limited, a corporation incorporated under the laws of the  United
Kingdom,  and  will  acquire  the balance  of  its  shares  as  a
condition to the Arrangement.

General

MDA  is  a  leading supplier of commercial space  remote  sensing
ground  stations,  installed in over  20  countries,  capable  of
handling   all  major  optical  and  radar  imaging,   or   Earth
observation,  satellites.   MDA  is  also  a  major  provider  of
advanced   space-qualified  software,  air  navigation   systems,
defence  electronic  systems and network communications  training
and consulting.

MDA's customers for systems are usually Fortune-500 companies and
government agencies worldwide.  MDA's basic business strategy  is
to  develop customized systems for individual clients, drawing on
proprietary  technologies and on off-the-shelf  products.   MDA's
strength is in undertaking fixed price projects and delivering on
time  and  within  the customer's budget.  MDA  currently  has  a
strategy of reducing its reliance on contracts from or related to
the  Canadian Federal Government through operations and alliances
outside  of Canada.  MDA is seeking to expand its export  markets
through understanding and accessing foreign funding sources  such
as multi-lateral development agencies.

Utilizing  existing  technologies and  seeking  opportunities  in
areas  that  complement MDA's business in terms of  technological
capabilities  and  markets,  MDA is currently  developing  a  new
business  strategy to capitalize on higher margin  opportunities.
As  part  of  the strategy, MDA's PSC division is  extending  its
consulting  services by negotiating worldwide service  agreements
with  manufacturers of computer network equipment.  The  strategy
also  contemplates MDA charging a per-use fee for data  processed
by  systems  provided by MDA.  In addition, MDA  may  acquire  an
equity  interest in ventures where it traditionally sold systems.
MDA's  participation  in  EarthWatch  Inc.  is  a  part  of  this
strategy.   This  strategy is also consistent  with  MDA's  25.4%
interest  in RSI, which has worldwide rights to market data  from
the soon to be launched RADARSAT satellite.  In other situations,
MDA  will  package components of customized systems into products
which  can be sold to many buyers with few changes.  This  latter
strategy  is designed to permit MDA to bring products  to  market
economically  by  capitalizing on the initial  development  of  a
system.   An  example of a new product opportunity is the  radar-
jamming system of the Space and Defence Systems business area.

MDA's business is divided into four business areas consisting  of
Geo-Information  Systems,  Aviation Systems,  Space  and  Defence
Systems and Communications, which are described in detail in  the
following sections.

Geo-Information Systems

Geo-Information Systems, MDA's largest business area in terms  of
revenues,  involves the development of systems for the management
of  Earth resources and the environment.  This business  area  is
built on MDA's expertise in Earth observation ground stations and
related markets.  The Geo-Information Systems business area  also
provides   operational  and  post-delivery  support   to   ensure
operational  efficiency of systems delivered  to  its  customers.
This  support includes consulting services, training, maintenance
and test equipment, spare parts and manuals.

MDA  is  one  of  the  world's  leading  companies  in  providing
solutions   for   the  acquisition,  processing,  archiving   and
dissemination of non-classified Earth observation data.   Of  the
26 non-secret ground stations in the world, MDA has built or been
involved  in  the  construction  of  23  ground  stations  in  20
countries.   These  ground stations are designed  to  receive  or
process data from some or all of the seven major non-secret Earth
observation  satellites  currently  in  operation.   Among  other
things,  the data is processed to construct useful images  or  is
modified  to  enhance  special  characteristics  or  to   correct
distortions and anomalies.

A  significant  portion of MDA's business in this  area  involves
upgrades  to existing systems.  Such upgrades are required  as  a
result  of  the  launch  of  new technologically-advanced  Earth-
observation  satellites in order to ensure that  existing  ground
stations  are  able to process the data that the  new  satellites
provide.   Delays  in  the  launch of  such  new  satellites  can
adversely impact the ground station upgrade business.

The  upgrade business has recently declined, in part due  to  the
failure  of  the U.S. LANDSAT-6 satellite, which was launched  in
1994  but  failed to achieve orbit.  The only satellite  launched
since  then  was  the  European Space Agency's  ERS-2  which  was
launched  in April 1995.  While MDA performed about $3.5  million
of  ground  station  upgrades in Europe for ERS-2  during  fiscal
1995,  additional upgrading work will be relatively minor because
this satellite uses technology similar to ERS-1, launched in July
1991.   However, several new technologically-advanced  satellites
are  scheduled  for launch by the end of 1996 and these  launches
are  expected  to  increase demand for new  and  upgraded  ground
stations.

Over  the  longer  term, other major trends  affecting  the  Geo-
Information Systems business area include technological advances,
the   loosening  of  government  restrictions,  and   a   growing
commercial  value  and  profit  potential  in  the  ownership  of
satellites  and  ground  stations.   The  technological  advances
include  a  declining  cost to obtain and disseminate  satellite-
based   Earth  information  and  the  proliferation  of  low-cost
personal  computers  capable  of  receiving  these  images.   The
loosening  of  government restrictions mainly involves  the  1994
decision  of  the  U.S.  government  to  begin  issuing  licences
permitting  private companies to obtain and sell  high-resolution
Earth  images  of a quality previously restricted  to  government
intelligence agencies.  MDA expects that these trends  will  lead
to  an  increase in the number of satellites and ground stations,
and  to  the ownership of some satellites and ground stations  by
private-sector companies.

MDA  has  completed several Earth information projects  involving
mission-control and mission-management systems for  the  Canadian
Space  Agency's RADARSAT satellite, scheduled for launch in  late
1995,  which  contracts  totalled $33.6 million.   MDA  has  also
completed  a  multi-year project to build a specialized  software
and  hardware ground system that refines raw data from  RADARSAT.
This  $10  million  system was installed at the Gatineau,  Quebec
ground station that MDA has upgraded several times since the mid-
1980s.   MDA  owns approximately 25% of RSI, which has  worldwide
rights to market data from the new RADARSAT satellite imagery.

In  addition  to space-based Earth observation, MDA builds  other
systems related to Earth information, including the $10.8 million
Fast  Mapping System for the government of Malaysia,  which  will
allow  the  Malaysian government to quickly update  and  generate
digital mapping products from satellite and airborne sensors, and
the  installation of a multimillion-dollar Airborne Radar  System
in China, which is used for flood monitoring and natural disaster
relief.

MDA  has  developed  and  delivered  airborne  Earth  observation
systems  with  both  electro-optical  and  radar  sensors.    The
Integrated  Radar  Imaging  System,  a  side-looking  radar  that
provides  detailed images of the ground in any light  or  weather
conditions,  makes high-resolution imagery available in  realtime
both  on  board an aircraft and at transportable ground stations.
Airborne Earth observation systems have been used for a number of
applications  including  mapping, forest  management,  oil  spill
recovery and ice flow monitoring in the Arctic.  MDA is a  member
of   a   team,   led  by  Raytheon  Corporation   of   Lexington,
Massachusetts,  that was awarded a contract  from  the  Brazilian
Government  in  May  1995  for  the  development  of  an   Amazon
surveillance  system.   MDA is currently  negotiating  the  final
terms of its subcontract with Raytheon.

In  mission management, under a contract with the European  Space
Agency  ("ESA"),  MDA has built a system for managing  the  ERS-1
satellite's instrument package and for cataloguing and  archiving
the  vast quantities of data the satellite will deliver over  its
lifetime.   MDA  expects  to  use this  technology  in  providing
satellite  mission  management systems in the  future,  including
systems  for  ESA's  ENVISAT satellite, which  is  scheduled  for
launch in 1998.

Aviation Systems

Since  1987, MDA's Aviation Systems business area has focused  on
specific aviation niche markets, including automated aeronautical
information systems and automated air traffic management systems.
This  division  was established to take advantage  of  a  growing
trend  toward  commercialization of civil  aviation  authorities.
This  commercialization typically leads to a strong incentive  to
cut  costs  by  investing in automation.  At the same  time,  the
airline industry estimates several billion dollars will be  spent
worldwide  before  the  year  2000 on  upgrading,  replacing  and
automating  civil aviation traffic management systems.   To  meet
these  developments MDA's Aviation Systems business area provides
the following:

Aeronautical Information Systems.  MDA builds and markets Pegasus-
AIS (unrelated to Orbital's Pegasus launch vehicle), an automated
aeronautical information management system.  The first sale of  a
Pegasus-AIS system was to the Belgian Air Force for $1.8 million.
Faster  and  less  expensive to operate than  traditional  manual
systems,  Pegasus-AIS  provides  pilots  and  other  users   with
aeronautical  and  meteorological  information.   MDA  has   been
developing  the underlying technology for Pegasus-AIS since  1989
by  way  of  customized automated briefing systems  that  MDA  is
building for civil aviation authorities in Australia, Norway  and
Belgium.   In  addition,  MDA  incorporates  its  knowledge  into
broader   air  traffic  management  systems.   MDA  has  recently
completed  work  on  a  $2.7 million AIS  project  in  India  for
Raytheon.

Air  Traffic Management Systems.  Air traffic management  systems
allow  air traffic controllers to guide pilots in flight.   These
systems  combine  information  about  flights,  routes,  weather,
navigational  aids, airways and airports and deliver  it  to  air
traffic controllers in a form that enables timely, safe decisions
to  be  made.   In  Canada,  MDA is  currently  working  under  a
subcontract  to Hughes Aircraft of Canada Limited  ("Hughes")  to
develop  and deliver air traffic management software as  part  of
the Canadian Automated Air Traffic System.  The subcontract value
was increased by $24 million during fiscal 1995 to a total of $85
million.   Hughes' prime contract with Transport Canada is  being
renegotiated.   In Switzerland, MDA has a $4 million  subcontract
for  a  Hughes air traffic control project.  Under a  $3  million
subcontract to Hughes, MDA is providing a military version of the
Canadian  Automated Air Traffic System to Canada's Department  of
National  Defence.   Together, MDA  and  Hughes  are  pursuing  a
growing   number   of  air  traffic  management   systems   sales
opportunities  around the world, including a  bid  on  two  large
projects  in Britain and the execution of projects in  China  and
Indonesia.

Space and Defence Systems

Many  of  MDA's  technologies  are  directly  applicable  to  the
development of space and defence systems.  Defence markets around
the world have declined as governments reformulate defence policy
in  the wake of the Gulf War and the collapse of the Soviet Bloc.
MDA  has,  however, sought to identify niches that are likely  to
grow  as  defence  agencies  focus  on  peace-time  surveillance,
monitoring  and  defensive capabilities.  MDA's  defence  systems
include   naval  mine  countermeasures,  artillery  command   and
control, radar deception system and military materiel management.
In  space-related work, MDA continues to provide  major  software
development efforts as part of Canada's contribution to the Space
Station  project.  This activity provides an opportunity for  the
enhancement of MDA's space-qualified software capabilities.   MDA
has  actively  pursued space and defence systems  business  since
1988.

Naval Mine Countermeasures System.  Since 1988 MDA has worked  on
a  series  of projects to develop geocoded sonar image  modelling
and  mosaicking  techniques for mapping  the  ocean  floor.   MDA
currently has an $80 million subcontract from a unit of the  SNC-
Lavalin  Group Inc. of Montreal to develop a mine countermeasures
system  for  the Canadian Navy's Maritime Coastal Defence  Vessel
program.   MDA's  role is to provide command and control  systems
and  operational  ship-borne and shore-based  sonar  sensing  and
processing capabilities for the detection of underwater mines.

Artillery  Command  and Control System.  MDA  is  developing  the
Artillery Regimental Data System to automate certain command  and
control  functions for the Canadian Army.  This project draws  on
MDA's  expertise in the computerization of geographic information
and  in the management of complex database systems.  The Army has
agreed  to  extend the project into the implementation phase  and
has increased the value of MDA's contract to $15.3 million.

Radar  Deception System.  MDA is developing a system  to  protect
airplanes, ships or ground installations from being detected  and
tracked by hostile radars, under contract with the Department  of
National  Defence.   MDA  is  also  pursuing  possible  licensing
arrangements that would allow original-equipment manufacturers to
market and install the product.

Military   Materiel  Management  System.   In  March  1994,   the
Department of National Defence selected the SHL Systemhouse  Inc.
team, which includes MDA as a major subcontractor, to upgrade the
Canadian Forces Supply System.  This inventory management  system
is scheduled for completion in 1997.

Communications

MDA  entered into the computer network communications, consulting
and  training  business in fiscal 1995 with  the  acquisition  of
Ottawa-based PSC Communications Group ("PSC").

PSC  helps  customers  design  and  implement  networks  so  that
computers  can  communicate faster and at  less  cost.   It  also
develops  software for special client needs, such as  to  monitor
networks  and find and correct trouble spots.  PSC  has  built  a
training   relationship  with  U.S.-based  Cisco   Systems   Inc.
("Cisco")  and a worldwide service relationship with Nortel  Inc.
PSC  recently  entered into a training relationship with  Digital
Equipment  Corporation ("DEC").  Training relationships  such  as
those with Cisco and DEC are expected to play a significant  role
in PSC's future business.

PSC's  relationship  with  Cisco,  one  of  the  world's  largest
manufacturers of network equipment, includes acting as a  leading
training  and consulting partner around the world.  PSC  provides
similar services for DEC in the United States.  PSC's arrangement
with  Nortel Inc. involves a new product called Entrust which  is
designed  to ensure the security of computer networking  systems.
PSC  provides post-sales service to Entrust customers,  including
product installation, training and ongoing customer support.  PSC
anticipates offering additional training through its  new  office
in  Australia, which will begin serving Hong Kong and other Asian
markets.

In  addition to classes for specific vendor products, PSC  offers
general  courses  in  computer communications,  aimed  mainly  at
technicians in companies across North America, Europe  and  other
parts  of the world.  PSC also provides software programming  and
consulting  services  for  clients with  network  related  needs,
including   assistance  to  customers  in   developing   advanced
switching  and  network management products and recommending  and
designing an optimal network system.

Contract Pricing and Completion

As  of March 31, 1995 approximately 56% of MDA's active contracts
were   fixed-price   contracts.   MDA  has   developed   costing,
contingency  management, operations and engineering methodologies
to  allow  it  to  undertake  work on a  fixed-price  basis,  and
believes its ability to undertake large-scale systems engineering
and  software development projects on a fixed-price  basis  is  a
major competitive advantage.  The balance of MDA's contracts  are
performed on a cost-plus or limitation of expenditures basis.

The   technical   nature  and  sophistication  of   the   systems
deliverable  under  MDA's contracts require  amendments  to  such
contracts  to  be negotiated, from time to time, in the  ordinary
course  of completing any contracts.  These amendments may relate
to  specifications, delivery times or similar  matters.   In  the
absence of an agreement to such amendments, customers of MDA  may
be  in  a  position to terminate a contract with MDA  and  demand
repayments  and penalties.  Any such termination and  demand  may
have  an  effect  on  the  earnings of MDA.   To  date,  MDA  has
generally been successful in renegotiating contracts as  required
from time to time.

MDA  endeavours  to  negotiate payment terms  in  its  commercial
contracts   that  include  advance  and  progress  payments   for
completion of project milestones.  To secure these payments, some
customers require bank guarantees or letters of credit for all or
part of the advance and progress payments remitted to MDA.

Marketing and Sales

Within  each of its business areas MDA focuses on specific  niche
markets   and  follows  a  strategy  of  seeking  to   thoroughly
understand, anticipate and follow the trends within each niche.

The  Earth  observation market is shifting from one of scientific
orientation  to one of end-user applications.  This has  resulted
in  MDA now providing complete remote sensing centres and mission
management  and  control  systems, where it  previously  marketed
satellite  ground stations.  In image analysis,  the  market  has
matured  for  specific application systems  focused  on  resource
management,  digital mapping and land information.  These  shifts
have  greatly  expanded the size of the markets in which  MDA  is
operating.

The  worldwide defence market is undergoing a rapid  change  from
one centred on conventional forces to one focused on intelligence
gathering  and surveillance by methods that include  the  use  of
sonar  or  radar  mapping  techniques.   Economic  pressures   on
governments  have  caused  defence  agencies  to  focus  on   the
efficient  use of resources through logistics and supply  service
systems.  MDA is focusing its defence marketing efforts on  these
new areas of emphasis.

The  space  market is shifting from a scientific  orientation  to
include    global   environmental   monitoring   and   commercial
applications.  Several large programs such as the U.S. Mission to
Planet  Earth, the Japanese ADEOS program and the European  Space
Agency's Polar Orbiting Earth Mission program will require  large
amounts  of  processing  of remotely sensed  satellite  data  and
mission  management  systems, and MDA has  positioned  itself  to
compete  in  these  emerging  markets.   In  addition,   MDA   is
positioning  itself to participate in the evolving private-sector
ownership  of  satellites and ground stations  through  a  supply
contract and the acquisition of a minority interest in EarthWatch
Inc.,  which  plans  to  launch a privately-owned  Earth  imaging
satellite in 1996.

MDA  has  taken advantage of the trend in the airspace management
market from a focus on radar systems and hardware to advanced air
traffic management systems.  Through participation in programs in
Canada, Australia, Norway, Belgium and Switzerland, MDA is  in  a
position  to  market automated technology that it has  previously
developed   and  provide  applications  expertise   relating   to
aeronautical information systems and flight data processing.

For  the  fiscal year ended March 31, 1995 approximately  44%  of
MDA's  revenues were generated from outside Canada,  an  increase
from  36%  a year earlier.  MDA traditionally works closely  with
domestic  and  foreign  customers to develop  technology.   MDA's
target  is  to  derive 70% of its revenues from  export  markets,
replacing  MDA's  reliance on Canadian government  funding.   The
Canadian  business is higher than the target, in part because  of
MDA's  entry  into several new market niches.  MDA is  developing
export markets for such business.

The  following table presents the source of MDA's gross  revenues
by region during the last three fiscal years:
<TABLE>
<CAPTION>
                     Gross
                   Revenues
                                            
Country               1993       1994     1995
<S>               <C>          <C>       <C>
Canada                52%           64%      56%
Asia                  25%           19%      11%
Europe                11%            9%      18%
Australia              4%            4%       3%
South America          1%             -        -
United States          1%            2%       6%
Other                  6%            2%       6%
Total                100%          100%     100%
</TABLE>

MDA's  sales  cycle  varies  from as short  as  three  weeks  for
communications  consulting projects to as long as  two  or  three
years  for  certain defence and ground station  projects.   Where
required  MDA  has  the capability to provide customer  financing
through  various agencies, including Canada's Export  Development
Corporation and the Asian Development Bank.

MDA  has  established sales and engineering offices worldwide  to
serve  key  geographic  locations.  These offices  are  presently
located  in  Canada,  the United States,  England,  Malaysia  and
Australia.   In  several  other countries  MDA  has  developed  a
network  of in-country agents to provide necessary assistance  to
sales  teams  and  to provide long-term customer  support.   PSC,
which  is operated as a division of MDA, has its headquarters  in
Ottawa,  Ontario,  and  has branch offices  in  Ontario,  British
Columbia, the United States, England and Australia.

Competition

MDA   participates  in  various  technological  and  geographical
markets.   No  one  competitor is considered  dominant  in  these
markets and MDA knows of no competitor which competes across  its
entire  span  of  technological expertise and markets.   MDA  may
compete against or team with the same company, depending  on  the
nature of each project opportunity.

In   the   Geo-Information  Systems  business  area,  MDA   faces
competition from Datron Systems Inc. and Hughes-STX Corp. of  the
United  States.   Competition in airborne radar systems  includes
Loral  Corp.  (USA) and Thomson CSF (France).  In  the  field  of
land, resource and environmental management systems, MDA faces  a
variety  of  competitors  including  MBB  Dornier  (Germany)  and
Intergraph Corp. (USA).

Competition  in  the Aviation Systems markets  is  broad.   Major
competitors  include  Siemens  Plessy  (Germany),  Alenia  S.p.A.
(Italy) and Thomson CSF (France).

In  the  Space  and  Defence  Systems market,  MDA's  competitive
strategy  is  to take part in a consortium, when appropriate,  in
order to participate in all of the major Canadian programs within
MDA's  particular areas of expertise.  Competitors and consortium
partners  vary  according to the specific program, but  typically
include  Computing Devices Canada, CAE Inc. and  Paramax  Systems
Canada.

PSC's  consulting business has many small competitors, while  its
training  business  competition is limited  to  a  few  companies
licensed by equipment manufacturers.

Research and Development

The  majority  of  systems developed by  MDA  are  large,  highly
interactive  and on the leading edge of technology.  MDA  devotes
significant resources to research and development because it is a
critical  element in the maintenance of MDA's edge  in  a  highly
competitive   and  rapidly  changing  worldwide  market.    MDA's
strategy  is  to  conduct most research and  development  through
commercial contracts with customers providing the funding,  while
maintaining the rights to use and exploit the technology.   Where
full  customer funding is not sufficient, MDA uses its own  funds
and   solicits   assistance  from  various  Canadian   Government
agencies.   A large percentage of MDA's customer-funded  research
is   contracted   from  government  agencies,  particularly   the
Government of Canada which encourages research activity  and  the
development of new systems for export around the world.

MDA's  net  research and development expenditures for the  fiscal
years  ended 1993, 1994 and 1995 were $4.4 million, $3.4  million
and  $2.4 million, respectively.  These amounts exclude customer-
funded  research  and  development and government  assistance  of
$28.8 million, $30.2 million and $31.7 million in 1993, 1994  and
1995, respectively.

Patents and Licenses

MDA  seeks  to protect its proprietary information and technology
under  applicable intellectual property laws.  For work  that  is
not    patentable,    contractual   provisions,    non-disclosure
agreements,  copyright and secrecy laws are all used  to  protect
MDA's proprietary information and technology.

Where  software is sold to a customer under contract,  rights  to
any   proprietary  software  used,  but  developed  outside   the
contract,  are restricted.  MDA seeks to retain, to the  greatest
extent  possible, rights to use the software developed under  the
contract.

Where   MDA  develops  systems  and  software  under  development
contracts  with  the Government of Canada or by  utilizing  funds
provided in the form of government assistance, the Government  of
Canada retains the ownership rights to the products developed and
in  return  licenses  the  technology to  the  developer.   These
licenses  are sole licenses which, in practice, give the  use  of
the  technology  only to the developer of the technology.   Where
systems  and  software are developed under development  contracts
with  other governments, however, MDA seeks to retain all  rights
to ownership and use of the technology developed.

Personnel

A key factor in MDA's success has been the ability to recruit and
retain  the highly qualified people it needs to be successful  in
the  diverse  and rapidly evolving markets in which it  competes.
As  at  March 31, 1995, MDA employed 916 people, the majority  of
whom  hold  university or college degrees.  MDA has no  unionized
employees and believes its relations with its employees are good.

Properties

MDA's  head office, located at 13800 Commerce Parkway,  Richmond,
British  Columbia, is comprised of approximately  182,000  square
feet and is leased until January 2004.  A second Richmond office,
located  at 13571 Commerce Parkway, is comprised of approximately
30,000  square feet and is leased until February 2003.  MDA  also
leases  space in Ottawa, Ontario and Kuala Lumpur, Malaysia,  and
its  subsidiaries  lease space for their operations  in  each  of
Boulder, Colorado; Farnham, England; and Sydney, Australia.   The
PSC  division is headquartered in Ottawa, Ontario and has offices
in   Toronto,   Ontario;  Richmond,  British  Columbia;   McLean,
Virginia; Bristol, England; and Sydney, Australia.

Management's  Discussion and Analysis of Financial Condition  and
Results of Operations

Results  of  Operations for the Quarter ended June 30,  1995  and
Quarter Ended June 30, 1994

For  the  first  quarter ended June 30, 1995, consolidated  gross
revenues  declined to $23.6 million, from $27.6 million  for  the
1994  quarter.  The decline in revenue is primarily due to delays
in  certain  satellite  launches that  impact  demand  for  Earth
information  systems.  MDA believes that revenues  will  increase
through  the  end of its 1996 fiscal year based  on  the  current
schedule of upcoming optical and radar satellite launches.

Despite the drop in revenues for the quarter ended June 30, 1995,
net  earnings  remained constant for the June 30, 1995  and  1994
quarters  at  $0.09 per MDA Common Share.  The earnings  for  the
June  30,  1994  quarter  were affected  by  several  low  margin
development projects that have since been completed.

Other  income  consists  primarily of  interest  income  on  term
deposits,  bank  balances  and  a  lease  receivable  with   RSI.
Interest  income  increased from $115,000 in  the  first  quarter
ended  June  30, 1994 to $232,000 in the 1995 quarter,  primarily
due  to  an  approximate  $9  million increase  in  average  cash
balances.

The  acquisition of The PSC Communications Group  Inc.  in  April
1994 was partially funded by debt, which is reflected in the  net
increase in long-term debt of $3.9 million for the quarter  ended
June 30, 1994.

Results  of Operations for the Fiscal Years ended March 31,  1995
and 1994

Consolidated  gross revenue increased by 8.4% over  the  previous
year.   Fiscal  year 1995 includes $13.9 million of revenue  from
MDA's   newly  acquired  Communications  business   area.    Geo-
Information  Systems  revenues declined  from  $59.3  million  in
fiscal  1994 to $48.8 million in fiscal 1995.  An important  part
of this unit's business is the construction and upgrade of ground-
based   Earth  observation  centres.   The  revenue  decline   is
attributable mainly to a temporary lull in the launching  of  new
Earth  observation satellites and the 1994 launch failure of  the
Landsat-6 satellite, which delayed several customers' programs.

Cost  of sales, consisting of labour, the purchase of deliverable
equipment  and  the engagement of subcontractors, rose  by  6.3%,
from  approximately $75.3 million in fiscal 1994 to $80.1 million
in  fiscal  1995.   In fiscal 1995, equipment and  subcontracting
costs  declined  as a percentage of revenue.  Labour  costs  were
higher  primarily due to the acquisition of PSC,  whose  cost  of
sales  is  comprised  mainly of labour,  and  a  one-time  labour
expense  to  deliver a UNIX based system for MDA's  Earth-imaging
technology.

Research  and  development  expenditures,  before  allowing   for
government assistance, were $4.7 million in fiscal 1995, up  9.9%
from  $4.3  million  in  fiscal 1994.   MDA  received  government
assistance for research and development of $2.3 million in fiscal
1995,  bringing  the  net  expenditure  to  $2.4  million.   That
compared  with net expenditures of $3.4 million in  fiscal  1994.
In  addition  to  the  internally funded expenditures,  customer-
funded  research and development, pursuant to which MDA  conducts
most of its research and development, was $29.3 million in fiscal
1995,  unchanged from fiscal 1994.  In most cases,  MDA  has  the
right  to exploit the technology that results from this customer-
funded research and development.

General  and  administrative expenditures were  $7.8  million  in
fiscal  1995, up from $6.7 million in fiscal 1994.  This increase
includes  $1.6  million attributable to the acquisition  of  PSC,
which  has a slightly higher general and administrative component
than  MDA's  traditional  business.  General  and  administrative
expenditures  for the traditional business declined  by  7.5%  in
fiscal 1995.

The  effective  rate  of income tax for MDA was  46.9%  in  1995,
compared with 44.0% in 1994.  This increase is primarily  due  to
certain losses on foreign operations which MDA was unable to take
advantage of in fiscal 1995 but which can be carried forward  and
used   in   the  future,  if  these  foreign  operations   become
profitable.  These foreign losses are substantially due to start-
up operations in Australia and Britain.

Cash  from operations was $4.2 million in fiscal 1995, down  from
$16.3   million   a  year  earlier.   This  change   is   largely
attributable  to  prepayment  in  fiscal  1994  for  work  to  be
performed  in fiscal 1995 and the recognition of revenue  on  the
percentage  of completion basis.  MDA does not recognize  advance
prepayments on work as revenue until the work is done.  In fiscal
1995,  MDA worked off advance payments that had been received  in
fiscal 1994.

Capital expenditures, primarily required to support growth in the
number   of  employees  and  replacement  of  existing  computing
infrastructure, totalled $3.9 million in 1995 compared with  $3.6
million  in fiscal 1994.  On April 6, 1994, MDA acquired 100%  of
PSC  for  $6.3  million.   The acquisition  was  funded  by  cash
reserves and a term bank loan.

Gross  order backlog at March 31, 1995 was $112 million, compared
to  $136 million at March 31, 1994.  The backlog has been  higher
in  the recent past due to the simultaneous booking of some large
multi-year  programs.   But  at about  one  year's  revenue,  the
backlog  is  typical for MDA's industry.  In addition,  with  the
acquisition of PSC and with changes in certain market niches, MDA
is less reliant on traditional, long-term delivery contracts than
it once was.

As  at the end of the 1995 fiscal year, MDA's bankers have issued
letters of guarantee to certain customers of MDA in the amount of
$9,459,000  of  which  $2,438,000 is guaranteed  by  the  Federal
Government  of  Canada.  If MDA fails to perform as  agreed  with
these  customers and if the letters of guarantee are called,  the
$7,021,000  due to MDA's bankers would be secured by an  existing
general assignment of book debts and assignment of raw materials,
work  in  progress and finished goods.  Inventories  relating  to
contracts  with  the Government of Canada are excluded  from  the
assignment.  The Federal Government of Canada is secured under  a
general recourse agreement, which ranks second to the charge held
by  MDA's  bankers.  A letter of guarantee has never  been  drawn
against with respect to any project.

Results  of Operations for the Fiscal Years ended March 31,  1994
and 1993

Consolidated   gross   revenues   increased   by   19.1%,    from
approximately $85.2 million in fiscal 1993 to $101.4  million  in
fiscal 1994.  Operating costs increased by 18.9% in fiscal  1994,
slightly  below  the increase in revenues for  the  corresponding
1993 period.  Internally funded research and development, net  of
government assistance, decreased from $4.4 million in fiscal 1993
to  $3.4  million  in  fiscal  1994.   Research  and  development
decreased   as   the   Geo-Information  Systems   business   area
substantially  completed  the development  phase  of  its  ground
station upgrade program in fiscal 1993.

Operating earnings increased to $5.3 million in fiscal 1994  from
$4.3  million  in fiscal 1993, an increase of 22%.  Other  income
decreased  from  $634,000 in fiscal 1993 to  $532,000  in  fiscal
1994.   The  decrease in interest income due  to  lower  interest
rates  is partially offset by interest income earned on  the  10%
lease receivable with RSI.

Net  cash provided by operations reached $16.3 million in  fiscal
1994,  compared  with  $0.5  million in  fiscal  1993.   Deferred
revenue  was a major reason for this change, increasing by  $12.0
million.    Deferred  revenue  represents  amounts  invoiced   to
customers  in  excess  of revenue earned.   Capital  expenditures
amounted to $3.6 million in 1994.

Directors and Officers

The following table sets forth the directors and officers of MDA,
their municipality of residence, their principal occupations, the
year  when  they became directors and the number  of  MDA  Common
Shares  and  MDA Options held by them.  Following  the  Effective
Date, Orbital expects to appoint new directors to the MDA Board.

<TABLE>
<CAPTION>

                                                       Principal           
                                                     Occupation if    No. of MDA
                                        Director    Different than      Common
  Name and Residence        Office       Since        Office Held      Shares or
                                                                      MDA Options
                                                                         Held
 <C>                     <C>            <C>         <C>               <C>       
 J. Brian Aune            Director      1986        Chairman, St.      Nil
 Westmount, Quebec                                  James Financial
                                                    Corporation
                                                    (Private
                                                    investment
                                                    company)
 
 Winslow W. Bennett*      Director      1982        President,         202,000
 Vancouver, B.C.                                    Winwood Holdings   shares
                                                    Ltd. (Private
                                                    investment
                                                    company)
 
 Michael J. Brown*        Director      1982        President,         100 shares
 West Vancouver, B.C.                               Ventures West
                                                    Management Inc.
                                                    (Venture capital
                                                    management)
 
 Mark H. Leonard          Director      1990        Senior Vice-       Nil
 Toronto, Ontario                                   President,
                                                    Ventures West
                                                    Management Inc.
                                                    (Venture capital
                                                    management)
 
 C. Calvert Knudsen*      Director      1988        Director,          50,000
 Seattle, Washington,                               MacMillan Bloedel  shares
 U.S.A.                                             Limited, formerly
                                                    Chairman and
                                                    Chief Executive
                                                    Officer of
                                                    MacMillan Bloedel
                                                    (Integrated
                                                    forest products
                                                    company)
 
 John S. MacDonald        Director,     1969                           1,110,449
 Vancouver, B.C.          Chairman of                                  shares
                          the Board                                    1,994
                                                                       options (1)
 
 John W. Pitts*           Director,     1982                           1,154,314
 Vancouver, B.C.          Deputy                                       shares
                          Chairman                                     2,341
                                                                       options (1)
 
 Daniel E. Friedmann      Director,     1992                           77,041
 Vancouver, B.C.          President                                    shares
                          and Chief                                    161,467
                          Executive                                    options (1)
                          Officer
 
 Mark Dostie              Director,     1995                           5 shares
 Vancouver, B.C.          Engineer
 David N. Caddey          Vice-                                        11,346
 Delta, B.C.              President,                                   shares
                          Space &                                      81,700
                          Defence                                      options (1)
                          Systems
 
 Bernard S. Clark         Vice-                                        15,165
 Delta, B.C.              President,                                   shares
                          Geo-                                         80,660
                          Information                                  options (1)
                          Systems
 
 Robert B. Wallis         Vice-                                        15,002
 Surrey, B.C.             President,                                   shares
                          Aviation                                     82,584
                          Systems,                                     options (1)
                          Chief
                          Financial
                          Officer and
                          Secretary
 
 Gordon D. Thiessen       Controller                                   3,029
 Richmond, B.C.           and                                          shares
                          Assistant                                    10,816
                          Secretary                                    options (1)
 
 John S. Rybinski         Treasurer                                    9,315
 Vancouver, B.C.                                                       shares
 
 Elizabeth J. Harrison,   Assistant                 Partner, Farris,   Nil
 Q.C.                     Secretary                 Vaughan, Wills &
 Vancouver, B.C.                                    Murphy
                                                    (Barristers and
                                                    Solicitors)
</TABLE> 
 *    Member of Audit Committee

Note:

(1)  The outstanding MDA Options are exercisable at varying times
     at prices ranging from $0.90 to $3.75 per MDA Common Share.

All  of the directors of MDA have been engaged for the last  five
years  in  their  present  principal  occupation  or  in  another
capacity  with  the  firms  identified opposite  their  names  or
related  firms,  with the exception of J. Brian Aune.   Prior  to
November 1990, Mr. Aune was Chairman and Chief Executive  Officer
of  Nesbitt Thomson Inc., an investment dealer.  MDA's Board does
not have an executive committee.

Description of Share Capital

The  authorized  share capital of MDA consists  of  an  unlimited
number  of  MDA Common Shares, 205,000 Class A Preference  Shares
and  27,000  Class B Preference Shares.  As at the  date  hereof,
there  are  no  Class A or Class B Preference Shares outstanding.
The  MDA Common Shares are without par value and rank equally  as
to  dividends  and  participation  in  assets  in  the  event  of
liquidation,  dissolution or winding  up.   The  holders  of  MDA
Common  Shares  are entitled to one vote for each share  held  at
general   meetings   of  MDA.   Following   completion   of   the
Arrangement, Acquisition will be the sole shareholder of MDA.

Dividend Record and Dividend Policy

MDA  paid  a  dividend of $1.00 per MDA Common  Share,  totalling
$10,965,000, on July 30, 1992.  No dividends have been paid since
that date.  It is MDA's general policy to retain its earnings for
use in its business and not to pay cash dividends.

Executive Compensation

Summary Compensation Table

The following table sets forth the summary of compensation of the
Chief Executive Officer and the four named executive officers  of
MDA  and  its subsidiaries for the fiscal years ended  March  31,
1994 and 1995:

<TABLE>
<CAPTION>
                                         Long-Term                       
                                         Compensation                    All
  Annual Compensation                       Awards                      Other
                                                                      Compensa-
                                                                        tion
                                                           Securities      
  Name and Principal                              Other      Under       
       Position          Year   Salary   Bonus    Annual    Options     $ (2)
                                  ($)     ($)    Compen-    Granted
                                                 sation (1)     (3)
<S>                     <C>    <C>       <C>     <C>        <C>        <C>

Daniel E. Friedmann      1995   208,000     ---       ---      35,000     7,342
President & C.E.O. (3)
Vice President & C.O.O   1994   202,000     ---       ---      30,000     7,352

John W. Pitts (3)        1995   216,000     ---       ---         ---     7,373
Deputy Chairman
President & C.E.O.       1994   216,000     ---       ---         ---     7,379

John S. MacDonald        1995   186,760  11,560       ---         ---     7,270
Chairman
                         1994   184,690  10,600                   ---     7,269

Bernard S. Clark         1995   113,600  20,499       ---      20,000     7,050
Vice President                                                                 
Geo-Information Systems  1994   108,933  30,947       ---      20,000     9,521

Robert B. Wallis         1995   110,200  20,000       ---      20,000     6,139
Chief Financial Officer                                                        
Vice-President,                                                                
Aviation Systems                                                               
                                                                               
Vice President           1994   107,369  10,000       ---      20,000     6,139
Chief Financial Officer

David N. Caddey          1995   108,600  17,233       ---      20,000     7,044
Vice President                                                                 
Space & Defence Systems  1994   107,400  29,965       ---      20,000     7,050

</TABLE>
Notes:

(1)  Perquisites  and other personal benefits do not  exceed  the
     lesser  of $50,000 and 10% of the total of the annual salary
     and  bonus  of the named executive officer for the financial
     year.
(2)  Includes   amounts   paid  pursuant  to   contributions   to
     designated retirement savings plan.
(3)  John  W.  Pitts  served  as President  and  Chief  Executive
     Officer until March 15, 1995.  Daniel E. Friedmann served as
     Executive  Vice President and Chief Operating Officer  until
     he  was  appointed President and Chief Executive Officer  on
     March 15, 1995.


Long-Term Incentive Plan Compensation

MDA  provides long-term incentive compensation to key  employees,
including  executive  officers, in the form  of  options  granted
under   the   Key  Employee  Share  Option  Plan  ("KESOP")   and
predecessor plans, whereby options to purchase MDA Common  Shares
are granted.

The  following table set forth individual grants of options under
the  KESOP  during the fiscal year ended March 31, 1995,  to  the
named executive officers:

 Options Granted During the Financial Year Ended March 31, 1995

<TABLE>
<CAPTION>
                                                            Market Value     
                                  % of Total                     of          
                                   Options                   Securities      
                      Securities  Granted to  Exercise of    Underlying      
                        Under     Employees    Base Price    Options on      
        Name           Options        in      ($/Security)  the Date of    Expiration
                       Granted    Financial                    Grant         Date
                       (#) (1)       Year                   ($/Security)
<S>                  <C>          <C>         <C>           <C>          <C>

Daniel E. Friedmann     35,000       14%          3.75          3.75         March
                                                                           31, 2001
Bernard S. Clark        20,000        8%          3.75          3.75         March
                                                                           31, 2001
Robert B. Wallis        20,000        8%          3.75          3.75         March
                                                                           31, 2001
David N. Caddey         20,000        8%          3.75          3.75         March
                                                                           31, 2001
</TABLE>
Note:

(1)  The  first  20%  of  the  MDA  Common Shares  under  option  vest
     immediately  and  the  remaining  options  vest  over  the   four
     succeeding anniversary dates of the day of grant.

The  following  table sets forth each exercise of options  during  the
fiscal year ended March 31, 1995 by the named executive officers:

     Aggregate Options Exercised During the Financial Year Ended
         March 31, 1995 and Financial Year-End Option Values

<TABLE>
<CAPTION>
                       Securities  Aggregate                       Value of
                        Acquired     Value    Unexercised       Unexercised in
        Name               on      Realized     Options        the Money Options
                        Exercise      ($)      at FY-End         at FY-End($)
                          (#)                     (#)      _________________________
                                              Exercisable  Unexer-   Exer-    Unexer-
                                                           cisable   cisable  cisable
<S>                   <C>          <C>        <C>         <C>       <C>      <C>   
Daniel E. Friedmann       ---         ---       81,760      40,000   302,512  148,000
Bernard S. Clark          ---         ---       35,400      24,000   130,980   88,800
Robert B. Wallis          ---         ---       37,500      24,000   138,750   88,800
David N. Caddey           ---         ---       39,700      24,000   146,870   88,800

</TABLE>

Pensions

MDA  does  not  maintain  any pension  plans  for  its  executive
officers.   MDA  makes  contributions on behalf  of  all  of  its
employees,   as  part  of  their  compensation,  for   registered
retirement savings plans ("RRSP") equal to the contributions made
by  each  employee to their RRSP up to a maximum of  5%  of  that
person's base salary.

Auditors

MDA's auditors are KPMG Peat Marwick Thorne, 777 Dunsmuir Street,
Vancouver, British Columbia V7Y 1K3.

Registrar and Transfer Agent

Montreal Trust Company, at its principal offices in Vancouver and
Toronto,  is the registrar and transfer agent for the MDA  Common
Shares.

Stock Exchange Listings

The MDA Common Shares are listed on the TSE and the VSE and trade
under the symbol "MDA".


               COMPARISON OF SHAREHOLDERS' RIGHTS

Former  MDA  Shareholders  will,  at  the  Effective  Date,   own
Exchangeable  Shares  that are exchangeable  for  Orbital  Common
Shares.  Pursuant to the Voting and Exchange Trust Agreement  the
Trustee  may, at the direction of the holders of the Exchangeable
Shares,  exercise  votes equivalent to those  of  Orbital  Common
Shares.   At the Effective Date, Acquisition will be a  reporting
issuer  under  the  laws  of the province  of  British  Columbia,
Ontario and certain other provinces.

While  the  rights and privileges of stockholders of  a  Delaware
corporation such as Orbital are, in many instances, comparable to
those  of shareholders of a corporation under the CBCA,  such  as
MDA   and  Acquisition,  there  are  certain  differences.    The
following  is a summary of the material differences  between  the
rights of holders of MDA Common Shares, the rights of holders  of
Exchangeable Shares, and the rights of holders of Orbital  Common
Shares.  These differences arise from differences between  United
States  and  Canadian securities laws, between the DGCL  and  the
CBCA,  and  between  the  MDA  articles  and  by-laws  (the  "MDA
Articles"  and  the  "MDA By-Laws," respectively),  Acquisition's
articles   (the   "Acquisition  Articles")   and   by-laws   (the
"Acquisition  By-laws") as proposed to be amended  in  connection
with the Arrangement and the Orbital Restated Certificate and by-
laws   (the  "Orbital  By-Laws").   For  a  description  of   the
respective rights of the holders of MDA Common Shares and Orbital
Common Shares, see, respectively, "Information Concerning  MDA  -
Share  Capital Structure" and "Information Concerning  Orbital  -
Description of Capital."

Extraordinary Transactions - Vote Required

Under the CBCA, certain extraordinary corporate actions, such  as
certain  amalgamations, continuances, sales, leases or  exchanges
of  all  the  assets of a corporation other than in the  ordinary
course  of  business, and other extraordinary  corporate  actions
such  as  liquidations, dissolutions and (if ordered by a  court)
arrangements, are required to be approved by special  resolution.
A  special resolution is a resolution passed by a majority of not
less  than  two-thirds of the votes cast by the shareholders  who
voted in respect of that resolution.  In certain cases, a special
resolution to approve an extraordinary corporate action  is  also
required  to be approved separately by the holders of a class  or
series of shares.

The  DGCL  requires  the affirmative vote of a  majority  of  the
outstanding  stock  entitled to vote  thereon  to  authorize  any
merger,  consolidation, dissolution or sale of substantially  all
of  the assets of a corporation, except that, unless required  by
its certificate of incorporation, no authorizing stockholder vote
is  required  of  a corporation surviving a merger  if  (a)  such
corporation's certificate of incorporation is not amended in  any
respect  by  the  merger,  (b)  each  share  of  stock  of   such
corporation  outstanding immediately prior to the effective  date
of  the merger will be an identical outstanding or treasury share
of  the  surviving corporation after the effective  date  of  the
merger,  and (c) the number of shares to be issued in the  merger
plus   those  initially  issued  upon  conversion  of  any  other
securities to be issued in the merger do not exceed 20%  of  such
corporation's outstanding common stock immediately prior  to  the
effective date of the merger.  Stockholder approval is  also  not
required under the DGCL for mergers or consolidations in which  a
parent  corporation merges or consolidates with a  subsidiary  of
which  it  owns  at least 90% of the outstanding shares  of  each
class  of  stock.   The  Orbital Restated  Certificate  does  not
require  a  greater percentage vote for such actions except  with
respect  to  certain  business combinations.  See  "Anti-takeover
Provisions and Interested Stockholder Transactions."

Such  matters  as  take-over bids, issuer bids or  self  tenders,
going-private  transactions  and  transactions  with   directors,
officers,  significant shareholders and other related parties  to
which  Acquisition is a party will be subject  to  regulation  by
Canadian  provincial  securities legislation  and  administrative
policies of Canadian securities administrators.  Similar  matters
to  which Orbital is a party will be subject to regulation  under
United States securities laws, regulations and policies.

Orbital's Restated Certificate contains a provision that requires
the holders of two-thirds of Orbital's voting power, voting as  a
single  class,  to  approve a merger or  certain  other  business
transactions  ("Business  Combination")  between  Orbital  and  a
holder  of more than 5% of Orbital's outstanding voting stock  or
any  such  holder's affiliates or associates ("Related  Person").
Stockholder   approval  is  not  required  if  the  "fair   price
provision" (as defined therein) is satisfied or if two-thirds  of
the  "Continuing  Directors" (as defined therein)  (i)  expressly
approve  in  advance  the acquisition of stock  that  caused  the
Related Person to become a Related Person and expressly decide in
advance  of  such acquisition that the approval of two-thirds  of
the  holders  of the outstanding shares of voting  stock  is  not
required,  or (ii) approve the Business Combination.   Generally,
the  "fair price provision" will have been satisfied if the price
received  by  the holders of shares of Orbital Common  Shares  or
other  class  of voting stock is not less than the highest  price
paid  by  the  Related Person when acquiring any of  its  Orbital
Common  Shares  or  other class of voting stock,  as  applicable,
within  the two-year period preceding the earlier of the date  of
the  Business  Combination  or  the  date  of  the  first  public
announcement of the Business Combination.

Amendment to Governing Documents

Under  the CBCA, any amendment to the articles generally requires
the  approval by special resolution, which is a resolution passed
by  a  majority of not less than two-thirds of the votes cast  by
shareholders who voted in respect of that resolution.  Under  the
CBCA,  unless  the  articles or by-laws  otherwise  provide,  the
directors  may, by resolution, make, amend or repeal  any  by-law
that  regulates the business or affairs of a corporation.   Where
the  directors make, amend or repeal a by-law, they are  required
under  the CBCA to submit the by-law, amendment or repeal to  the
shareholders  at  the  next  meeting  of  shareholders,  and  the
shareholders  may confirm, reject or amend the by-law,  amendment
or repeal by an ordinary resolution, which is a resolution passed
by  a majority of the votes cast by the shareholders who voted in
respect of the resolution.

The  DGCL requires a vote of the corporation's board of directors
followed by the affirmative vote of a majority of the outstanding
stock  of  each class entitled to vote for any amendment  to  the
certificate of incorporation, unless a greater level of  approval
is  required  by the certificate of incorporation.   The  Orbital
Restated Certificate provides that any amendment that relates  to
(i)  a director's liability to Orbital or its stockholders,  (ii)
indemnification of directors, (iii) classification of  the  board
of  directors  or election or removal of directors,  (iv)  voting
requirements for approval of certain mergers, consolidations  and
other  business  combinations, or  (v)  voting  requirements  for
amendment  of  any  supermajority  voting  provisions,  must   be
approved by the affirmative vote of the holders of not less  than
two-thirds  of the outstanding shares entitled to  vote  for  the
election  of  directors.  The DGCL provides that if an  amendment
alters  the powers, preferences or special rights of a particular
class  or  series  of stock so as to affect them adversely,  that
class  or  series  shall be given the power to vote  as  a  class
notwithstanding the absence of any specifically enumerated  power
in  the  certificate  of incorporation.   The  Orbital  Series  A
Preferred  Share  which  will be issued in  connection  with  the
Arrangement  has special voting powers.  See "The  Arrangement  -
Description of Exchangeable Shares - Voting Rights."

The DGCL also states that the power to adopt, amend or repeal the
by-laws of a corporation shall be in the stockholders entitled to
vote,  provided  that  the  corporation  in  its  certificate  of
incorporation may confer such power on the board of directors  in
addition   to  the  stockholders.   Under  the  Orbital  Restated
Certificate  the board of directors has been granted this  power.
The Orbital By-laws are subject to adoption, amendment, repeal or
rescission  by a majority of the authorized number of  directors,
subject  to the right of the stockholders entitled to  vote  with
respect thereto to alter and repeal by-laws adopted by the  board
of directors.

Dissent Rights

The  CBCA  provides  that  shareholders  of  a  CBCA  corporation
entitled  to  vote  on certain matters are entitled  to  exercise
dissent  rights and to be paid the fair value of their shares  in
connection  therewith.  The CBCA does not  distinguish  for  this
purpose between listed and unlisted shares.  Such matters include
(a)  any  amalgamation with another corporation (other than  with
certain  affiliated  corporations);  (b)  an  amendment  to   the
corporation's  articles to add, change or remove  any  provisions
restricting  or constraining the issue, transfer or ownership  of
shares;  (c) an amendment to the corporation's articles  to  add,
change  or  remove any restriction on the business or  businesses
that  the  corporation may carry on or upon the powers  that  the
corporation  may exercise; (d) a continuance under  the  laws  of
another  jurisdiction; (e) a sale, lease or exchange  of  all  or
substantially all the property of the corporation other  than  in
the  ordinary course of business; (f) a court order permitting  a
shareholder to dissent in connection with an application  to  the
court  for  an  order approving an arrangement  proposed  by  the
corporation;  or  (g) certain amendments to  the  articles  of  a
corporation  which  require  a separate  class  or  series  vote,
provided  that  a shareholder is not entitled to  dissent  if  an
amendment  to the articles is effected by a court order approving
a  reorganization or by a court order made in connection with  an
action  for  an oppression remedy.  Under the CBCA, a shareholder
may, in addition to exercising dissent rights, seek an oppression
remedy  for  any  act  or  omission of  a  corporation  which  is
oppressive, unfairly prejudicial to or that unfairly disregards a
shareholder's interest.

Under the DGCL, holders of shares of any class or series have the
right,  in  certain circumstances, to dissent from  a  merger  or
consolidation by demanding payment in cash for their shares equal
to  the fair value (excluding any appreciation or depreciation as
a  consequence,  or in expectation, of the transaction)  of  such
shares, as determined by agreement with the corporation or by  an
independent  appraiser appointed by a court in an  action  timely
brought  by  the corporation or the dissenters.  The DGCL  grants
dissenters'  appraisal  rights only in the  case  of  mergers  or
consolidations  and  not in the case of a  sale  or  transfer  of
assets or a purchase of assets for stock regardless of the number
of  shares  being  issued.   Further,  no  appraisal  rights  are
available for shares of any class or series listed on a  national
securities  exchange  or designated as a national  market  system
security  on  the  NASDAQ or held of record by  more  than  2,000
stockholders,  unless  the agreement of merger  or  consolidation
converts  such shares into anything other than (a) stock  of  the
surviving corporation, (b) stock of another corporation which  is
either listed on a national securities exchange or designated  as
a national market system security on the NASDAQ or held of record
by  more  than 2,000 stockholders, (c) cash in lieu of fractional
shares, or (d) some combination of the above.  In addition,  such
rights  are  not  available  for  any  shares  of  the  surviving
corporation  if  the  merger did not  require  the  vote  of  the
stockholders of the surviving corporation.

Oppression Remedy

The CBCA provides an oppression remedy that enables the court  to
make  any  order, both interim and final, to rectify the  matters
complained  of, if the Director under the CBCA is satisfied  upon
application by a complainant (as defined below) that: (i) any act
or  omission of the corporation or an affiliate effects a result;
(ii)  the  business or affairs of the corporation or an affiliate
are  or  have been carried on or conducted in a manner; or  (iii)
the  powers  of the directors of the corporation or an  affiliate
are,  have  been or are threatened to be exercised  in  a  manner
that,  in  any of the foregoing cases, is oppressive or  unfairly
prejudicial to, or that unfairly disregards the interests of  any
security   holder,   creditor,  director  or   officer   of   the
corporation.   A  complainant includes: (a) a present  or  former
registered  holder  or  beneficial  owner  of  securities  of   a
corporation  or  any of its affiliates; (b) a present  or  former
officer  or director of the corporation or any of its affiliates;
(c) the Director under the CBCA; and (d) any other person who  in
the  discretion  of  the court is a proper person  to  make  such
application.

Because of the breadth of the conduct which can be complained  of
and  the  scope  of the court's remedial powers,  the  oppression
remedy  is  very  flexible  and  is  frequently  relied  upon  to
safeguard  the  interests of shareholders and other  complainants
with  a substantial interest in the corporation.  Under the CBCA,
it  is not necessary to prove that the directors of a corporation
acted  in  bad  faith  in  order to seek  an  oppression  remedy.
Furthermore,  the  court  may order the corporation  to  pay  the
interim  expenses of a complainant seeking an oppression  remedy,
but  the  complainant may be held accountable  for  such  interim
costs on final disposition of the complaint (as in the case of  a
derivative  action).   The DGCL does not provide  for  a  similar
remedy.

Derivative Action

Derivative actions may be brought in Delaware by a stockholder on
behalf  of,  and for the benefit of, the corporation.   The  DGCL
provides that a stockholder must aver in the complaint that he or
she  was  a  stockholder of the corporation at the  time  of  the
transaction of which he or she complains.  A stockholder may  not
sue  derivatively  unless he or she first  makes  demand  on  the
corporation that it bring suit and such demand has been  refused,
unless it is shown that such demand would have been futile.

Under the CBCA, a complainant may apply to the court for leave to
bring an action in the name of and on behalf of a corporation  or
any  subsidiary, or to intervene in an existing action  to  which
any  such  body  corporate  is  a  party,  for  the  purpose   of
prosecuting, defending or discontinuing the action on  behalf  of
the body corporate.  Under the CBCA, no action may be brought and
no  intervention  in an action may be made unless  the  court  is
satisfied that (a) the complainant has given reasonable notice to
the  directors  of  the  corporation or  its  subsidiary  of  the
complainant's intention to apply to the court if the directors of
the  corporation  or  its  subsidiary do  not  bring,  diligently
prosecute   or  defend  or  discontinue  the  action;   (b)   the
complainant is acting in good faith; and (c) it appears to be  in
the  interests  of  the corporation or its  subsidiary  that  the
action  be  brought,  prosecuted, defended  or  discontinued.   A
complainant  is  not required to give security  for  costs  in  a
derivative action.

Shareholder Consent in Lieu of Meeting

Under  the DGCL, unless otherwise provided in the certificate  of
incorporation, any action required to be taken or  which  may  be
taken  at  an  annual or special meeting of stockholders  may  be
taken without a meeting if a consent in writing is signed by  the
holders  of  outstanding stock having not less than  the  minimum
number  of votes that would be necessary to authorize such action
at  a  meeting at which all shares entitled to vote were  present
and  voted.  The Orbital Restated Certificate does not permit any
action  to  be  taken  by  written  consent.   Under  the   CBCA,
shareholder action without a meeting may only be taken by written
resolution  signed by all shareholders who would be  entitled  to
vote thereon at a meeting.

Director Qualifications

A  majority of the directors of a CBCA corporation generally must
be resident Canadians.  The CBCA also requires that a corporation
whose  securities are publicly traded must have  not  fewer  than
three  directors,  at  least two of  whom  are  not  officers  or
employees  of the corporation or its affiliates.  The  DGCL  does
not have comparable requirements.

Fiduciary Duties of Directors

Directors  of  corporations incorporated or organized  under  the
CBCA  and  the DGCL have fiduciary obligations to the corporation
and  its  shareholders.  Pursuant to these fiduciary obligations,
the directors must act in accordance with the so-called duties of
"due  care"  and  "loyalty."  Under the DGCL, the  duty  of  care
requires  that the directors act in an informed and  deliberative
manner   and  inform  themselves,  prior  to  making  a  business
decision,  of  all material information available to  them.   The
duty  of  loyalty may be summarized as the duty to  act  in  good
faith,  not  out  of  self-interest, and in a  manner  which  the
directors reasonably believe to be in the best interests  of  the
stockholders.

Pursuant to section 122 of the CBCA, the duty of loyalty requires
directors of a CBCA corporation to act honestly and in good faith
with  a  view to the best interests of the corporation,  and  the
duty  of  care  requires that the directors  exercise  the  care,
diligence  and  skill  that  a reasonably  prudent  person  would
exercise in comparable circumstances.

Indemnification of Officers and Directors

Under  the  CBCA  and  pursuant  to  the  MDA  By-Laws  and   the
Acquisition By-Laws, MDA and Acquisition may indemnify a director
or  officer, a former director or officer or a person who acts or
acted at the corporation's request as a director or officer of  a
body  corporate of which MDA or Acquisition, as the case may  be,
is  or  was  a shareholder or creditor, and his or her heirs  and
legal  representatives (an "Indemnifiable Person"),  against  all
costs,  charges and expenses, including an amount paid to  settle
an  action or satisfy a judgment, reasonably incurred by  him  or
her in respect of any civil, criminal or administrative action or
proceeding to which he or she is made a party by reason of  being
or  having  been a director or officer of MDA or Acquisition,  as
the  case may be, or such body corporate, if: (a) he or she acted
honestly  and in good faith with a view to the best interests  of
MDA;  and (b) in the case of a criminal or administrative  action
or  proceeding that is enforced by a monetary penalty, he or  she
had  reasonable grounds for believing that his or her conduct was
lawful.   An  Indemnifiable Person is entitled to such  indemnity
from the corporation if he or she was substantially successful on
the  merits in his or her defence of the action or proceeding and
fulfilled  the  conditions set out in  (a)  and  (b),  above.   A
corporation may, with the approval of a court, also indemnify  an
Indemnifiable Person in respect of an action by or on  behalf  of
the  corporation or such body corporate to procure a judgment  in
its  favour,  to which such person is made a party by  reason  of
being  or having been a director or an officer of the corporation
or body corporate, if he or she fulfils the conditions set out in
(a) and (b), above.

The  DGCL  provides that a corporation may indemnify its  present
and  former  directors, officers, employees and agents  (each  an
"indemnitee")   against   all  reasonable   expenses   (including
attorneys' fees) and, except in actions initiated by  or  in  the
right  of  the  corporation, against  all  judgments,  fines  and
amounts  paid in settlement in actions brought against  them,  if
such  indemnitee acted in good faith and in a manner which he  or
she  reasonably believed to be in, or not opposed  to,  the  best
interests  of  the  corporation, and in the case  of  a  criminal
proceeding, had no reasonable cause to believe that  his  or  her
conduct  was  unlawful.   The  corporation  shall  indemnify   an
indemnitee  to  the  extent that he or she is successful  on  the
merits  or otherwise in the defence of any claim, issue or matter
associated  with  an  action.  The Orbital  Restated  Certificate
provides  for  indemnification of directors or  officers  to  the
fullest extent permitted by the DGCL.

The  DGCL  allows  for  the advance payment  of  an  indemnitee's
expenses  prior  to the final disposition of an action,  provided
that  the indemnitee undertakes to repay any such amount advanced
if  it is later determined that the indemnitee is not entitled to
indemnification with regard to the action for which such expenses
were  advanced.   The CBCA does not expressly  provide  for  such
advance payment.

Director Liability

The DGCL provides that the charter of the corporation may include
a provision which limits or eliminates the liability of directors
to  the corporation or its stockholders for monetary damages  for
breach  of  fiduciary duty as a director, provided such liability
does not arise from certain proscribed conduct, including acts or
omissions   not  in  good  faith  or  which  involve  intentional
misconduct or a knowing violation of law, breach of the  duty  of
loyalty,  the  payment of unlawful dividends  or  expenditure  of
funds for unlawful stock purchases or redemptions or transactions
from  which  such director derived an improper personal  benefit.
The  Orbital  Restated Certificate contains a provision  limiting
the liability of its directors to the fullest extent permitted by
the  DGCL.   The  CBCA does not permit any such limitation  of  a
director's liability.

Anti-takeover Provisions and Interested Stockholder Transactions

The   DGCL  prohibits,  in  certain  circumstances,  a  "business
combination"   between  the  corporation   and   an   "interested
stockholder"  within three years of the stockholder  becoming  an
"interested  stockholder."   An  "interested  stockholder"  is  a
holder  who, directly or indirectly, controls 15% or more of  the
outstanding  voting stock or is an affiliate of  the  corporation
and  was the owner of 15% or more of the outstanding voting stock
at  any  time  within the prior three-year period.   A  "business
combination" includes a merger or consolidation, a sale or  other
disposition of assets having an aggregate market value of 10%  or
more  of  the  consolidated  assets of  the  corporation  or  the
aggregate   market  value  of  the  outstanding  stock   of   the
corporation  and  certain transactions that  would  increase  the
interested  stockholder's proportionate share  ownership  in  the
corporation.  This provision does not apply where: (i) either the
business  combination or the transaction which  resulted  in  the
stockholder becoming an interested stockholder is approved by the
corporation's board of directors prior to the date the interested
stockholder   acquired   such  15%  interest;   (ii)   upon   the
consummation of the transaction which resulted in the stockholder
becoming  an  interested stockholder, the interested  stockholder
owned  at  least  85%  of the outstanding  voting  stock  of  the
corporation excluding, for the purpose of determining the  number
of  shares  outstanding, shares held by persons who are directors
and   also  officers  and  by  employee  stock  plans  in   which
participants  do  not have the right to determine  confidentially
whether  shares held subject to the plan will be tendered,  (iii)
the  business combination is approved by a majority of the  board
of  directors  and  the  affirmative vote of  two-thirds  of  the
outstanding   votes   entitled  to  be  cast   by   disinterested
stockholders   at  an  annual  or  special  meeting;   (iv)   the
corporation does not have a class of voting stock that is  listed
on a national securities exchange, authorized for quotation on an
inter-dealer quotation system of a registered national securities
association,  or  held of record by more than 2,000  stockholders
unless  any of the foregoing results from action taken,  directly
or indirectly, by an interested stockholder or from a transaction
in  which a person becomes an interested stockholder, or (v)  the
corporation  has  opted out of this provision.  Orbital  has  not
opted out of this provision.

The CBCA does not contain a comparable provision with respect  to
"business  combinations"  however policies  of  certain  Canadian
securities  regulatory authorities, including Policy 9.1  of  the
Ontario    Securities   Commission   ("Policy   9.1"),    contain
requirements  in  connection with related party transactions.   A
related  party  transaction means, generally, any transaction  by
which an issuer, directly or indirectly, acquires or transfers an
asset  or  acquires or issues treasury securities or  assumes  or
transfers  a liability from or to, as the case may be, a  related
party  by any means in any one transaction or any combination  of
transactions.   "Related  party" is  defined  in  Policy  9.1  to
include directors, senior officers and holders of at least 10% of
the voting securities of the issuer.

Policy  9.1  requires  more  detailed disclosures  in  the  proxy
material  sent to security holders in connection with  a  related
party  transaction.   Where  the value  of  the  asset,  treasury
security or the principal amount of the liability, subject to the
related  party  transactions exceeds 25% of the  issuer's  market
capitalization,  subject  to  certain  exceptions,   Policy   9.1
requires  the  preparation of a formal valuation of  the  subject
matter   of  the  related  party  transaction  and  any  non-cash
consideration offered therefor and the inclusion of a summary  of
the   valuation  in  the  proxy  material.   For  related   party
transactions of such value, Policy 9.1 also requires, subject  to
certain exemptions, that the minority shareholders of the  issuer
approve  the  transaction, by either a simple  majority  or  two-
thirds of the votes cast, depending upon the circumstances.

Shareholder Protection Rights Plan

MDA  has  a  Shareholder Protection Rights Plan.  The Shareholder
Protection   Rights  Plan  in  certain  specific   circumstances,
including the event of a hostile takeover bid being made for MDA,
provides that each MDA Common Shareholder is entitled to  acquire
MDA  Common Shares, or in certain circumstances common shares  of
the  bidder,  at  a 50% discount from the then prevailing  market
price.    The  MDA  Board  has  waived  the  provisions  of   the
Shareholder  Protection  Rights Plan to permit  the  transactions
contemplated   by   the  Arrangement  to  be  completed   without
triggering such provisions.

Orbital does not currently have a plan similar to the Shareholder
Protection  Rights  Plan,  although  plans  comparable   to   the
Shareholder Protection Rights Plan are permitted by the DGCL  and
may  be  adopted  by  a  board of directors  without  shareholder
approval.   Orbital may in the future adopt a shareholder  rights
plan.


                       DISSENTING RIGHTS

Pursuant  to  the Interim Order, MDA Shareholders  and  MDA  1988
Optionholders have been provided with the right to  dissent  from
the   Arrangement   Resolution  under  and  in  compliance   with
section 190 of the CBCA and the Interim Order, reprinted in their
entireties as Appendices "D" and "G", respectively to this  Proxy
Circular.  The following summary is qualified in its entirety  by
the Interim Order and the provisions of section 190 of the CBCA.

Pursuant  to  the Interim Order, a MDA Shareholder  who  dissents
from the Arrangement Resolution in compliance with section 190 of
the  CBCA  and the Interim Order (a "Dissenting MDA Shareholder")
will be entitled, in the event the Arrangement becomes effective,
to be paid by MDA the fair value of the MDA Common Shares held by
such  Dissenting MDA Shareholder determined as of  the  close  of
business on the day before the Arrangement Resolution is adopted.

Pursuant  to  the Interim Order and the Plan of Arrangement,  any
MDA   1988   Optionholder  who  dissents  from  the   Arrangement
Resolution  in accordance with section 190 of the  CBCA  and  the
Interim  Order (a "Dissenting MDA 1988 Optionholder"),  shall  be
deemed,  pursuant  to  the Plan of Arrangement  and  the  Interim
Order,  to  have exercised the MDA 1988 Options with  respect  to
which  he or she is exercising the dissent.  Such Dissenting  MDA
1988  Optionholder, will be entitled, if the Arrangement  becomes
effective,  to  be paid the fair value of the MDA  Common  Shares
deemed to have been issued upon exercise, set-off by the exercise
price.   The  fair value shall be determined as of the  close  of
business on the day before the Arrangement Resolution is adopted.

A  MDA Shareholder or MDA 1988 Optionholder who wishes to dissent
must  send  to MDA, no later than the termination of the  Special
Meeting  (or any adjournment thereof), written objection  to  the
Arrangement Resolution (a "Dissent Notice") and must not vote for
the  Arrangement Resolution.  The filing of a Dissent Notice does
not  deprive a MDA Shareholder or a MDA 1988 Optionholder, as the
case  may  be, of the right to vote.  The CBCA does not  provide,
and  MDA  will  not assume, that a vote against  the  Arrangement
Resolution  or an abstention constitutes a Dissent Notice  but  a
MDA  Shareholder or a MDA 1988 Optionholder need not vote his  or
her  MDA  Common Shares or the votes to be exercised with respect
to his or her MDA 1988 Options against the Arrangement Resolution
in  order  to  dissent.  Under the CBCA, there  is  no  right  of
partial dissent and, accordingly, a Dissenting MDA Shareholder or
a  Dissenting MDA 1988 Optionholder, as the case may be, may only
dissent  with respect to all MDA Common Shares or all MDA  Common
Shares to which he or she is entitled under all MDA 1988 Options,
respectively, held by him or her on behalf of any one  beneficial
owner and which are registered in the name of the Dissenting  MDA
Shareholder or Dissenting MDA 1988 Optionholder, as the case  may
be.

MDA  is required, within 10 days after the Arrangement Resolution
is   adopted,  to  notify  each  MDA  Shareholder  or  MDA   1988
Optionholder  or  MDA 1988 Optionholder who has filed  a  Dissent
Notice that the Arrangement Resolution has been adopted, but such
notice  is  not  required to be sent to any MDA  Shareholder  who
voted for the Arrangement Resolution or who has withdrawn his  or
her Dissent Notice.

A   Dissenting   MDA  Shareholder  or  a  Dissenting   MDA   1988
Optionholder  must then, within 20 days after receipt  of  notice
that the Arrangement Resolution has been adopted or, if he or she
does  not  receive such notice, within 20 days after  he  or  she
learns that the Arrangement Resolution has been adopted, send  to
MDA  a written notice (a "Payment Demand") containing his or  her
name  and address, the number of MDA Common Shares in respect  of
which  he  or she dissents, and a demand for payment of the  fair
value of such MDA Common Shares.  Within 30 days after sending  a
Payment Demand, the Dissenting MDA Shareholder must send  to  the
MDA  transfer agent the certificates representing the MDA  Common
Shares in respect of which he or she dissents.  A Dissenting  MDA
1988 Optionholder shall be deemed to have sent those certificates
to the MDA transfer agent by reason of the deemed exercise of the
MDA  1988  Option.  A Dissenting MDA Shareholder or a  Dissenting
MDA  1988  Optionholder  who fails to send  to  MDA,  within  the
appropriate time frame, certificates representing the MDA  Common
Shares  in respect of which he or she dissents, forfeits  his  or
her  right  to make a claim in accordance with the provisions  of
section 190 of the CBCA.  The MDA transfer agent will endorse  on
share  certificates received from a Dissenting MDA Shareholder  a
notice  that the holder is a Dissenting MDA Shareholder and  will
forthwith  return  the share certificates to the  Dissenting  MDA
Shareholder.

On  sending a Payment Demand to MDA, a Dissenting MDA Shareholder
or  a  Dissenting MDA 1988 Optionholder ceases to have any rights
as  a  MDA  Shareholder or MDA 1988 Optionholder, other than  the
right  to be paid the fair value of his or her MDA Common  Shares
as determined under section 190 of the CBCA, except where:

(a)  the  Dissenting  MDA  Shareholder or a Dissenting  MDA  1988
     Optionholder withdraws his or her Payment Demand before  MDA
     makes an offer to him or her pursuant to the CBCA;

(b)  MDA  fails to make an offer as hereinafter described and the
     Dissenting  MDA  Shareholder  or  the  Dissenting  MDA  1988
     Optionholder withdraws his or her Payment Demand; or

(c)  the Arrangement does not proceed;

in  which  case his or her rights as a MDA Shareholder or  a  MDA
1988  Optionholder, as the case may be, are reinstated as of  the
date he or she sent the Payment Demand.

MDA is required, not later than seven days after the later of the
Effective  Date  or  the date on which MDA received  the  Payment
Demand  of a Dissenting MDA Shareholder or a Dissenting MDA  1988
Optionholder, as the case may be, to send to each such dissenting
person  who  has  sent a Payment Demand a written  offer  to  pay
("Offer  to  Pay")  for his or her MDA Common  Shares  an  amount
considered by the MDA Board to be the fair value thereof, on  the
close of business on the day before the Arrangement Resolution is
adopted,  accompanied by a statement showing the manner in  which
the fair value was determined.  Every Offer to Pay must be on the
same  terms.   MDA  must  pay for the  MDA  Common  Shares  of  a
Dissenting  MDA Shareholder or a Dissenting MDA 1988 Optionholder
within  10 days after an Offer to Pay made as aforesaid has  been
accepted by a Dissenting MDA Shareholder or a Dissenting MDA 1988
Optionholder, but any such Offer to Pay lapses if  MDA  does  not
receive  an acceptance thereof within 30 days after the Offer  to
Pay has been made.

If  MDA  fails  to  make  an Offer to Pay for  a  Dissenting  MDA
Shareholder's or a Dissenting MDA 1988 Optionholder's MDA  Common
Shares,  or  if a Dissenting MDA Shareholder or a Dissenting  MDA
1988  Optionholder fails to accept an Offer to Pay which has been
made,  MDA may, within 50 days after the Effective Date or within
such further period as a court may allow, apply to a court having
jurisdiction in the place where MDA has its registered office  or
in   the  Province  where  such  Dissenting  MDA  Shareholder  or
Dissenting  MDA  1988  Optionholder resides  if  MDA  carries  on
business in that province, to fix a fair value for the MDA Common
Shares  of  Dissenting MDA Shareholders or  Dissenting  MDA  1988
Optionholders.   If  MDA fails to apply to a  court  within  such
period,  a  Dissenting  MDA Shareholder or  Dissenting  MDA  1988
Optionholder may apply to a court for the same purpose  within  a
further  period  of 20 days or within such further  period  as  a
court may allow.  A Dissenting MDA Shareholder or Dissenting  MDA
1988  Optionholder is not required to give security for costs  in
such an application.

Upon  an  application to a court, all Dissenting MDA Shareholders
and all Dissenting MDA 1988 Optionholders whose MDA Common Shares
have  not  been  purchased by MDA will be joined as  parties  and
bound  by the decision of the court, and MDA will be required  to
notify  each  affected Dissenting MDA Shareholder and  Dissenting
MDA  1988 Optionholder of the date, place and consequences of the
application  and of his or her right to appear and  be  heard  in
person or by counsel.  Upon any such application to a court,  the
court  may determine whether any other Dissenting MDA Shareholder
or  Dissenting MDA 1988 Optionholder should be joined as a party,
and  the  court  will then fix a fair value for  the  MDA  Common
Shares of all Dissenting MDA Shareholders or Dissenting MDA  1988
Optionholders who have not accepted an Offer to Pay.   The  final
order  of a court will be rendered against MDA in favour of  each
such   Dissenting  MDA  Shareholder  and  Dissenting   MDA   1988
Optionholder and for the amount of the fair value of his  or  her
MDA  Common Shares as fixed by the court.  The court may, in  its
discretion,  allow a reasonable rate of interest  on  the  amount
payable  to  each such Dissenting MDA Shareholder and  Dissenting
MDA  1988 Optionholder from the Effective Date until the date  of
payment.

The  above  is  only  a  summary of  the  dissenting  shareholder
provisions of the CBCA and the Interim Order, which are technical
and  complex.   It is suggested that any MDA Shareholder  or  MDA
1988  Optionholder wishing to avail himself or herself of his  or
her  rights  under  those provisions seek his or  her  own  legal
advice  as failure to comply strictly with the provisions of  the
CBCA  and  the  Interim Order may prejudice his or her  right  of
dissent.    For   a  general  summary  of  certain   income   tax
implications  to  a Dissenting MDA Shareholder, see  "Income  Tax
Considerations to MDA Shareholders and Optionholders  -  Canadian
Federal  Income Tax Considerations - Dissenting MDA Shareholders,
and  "-  Dissenting MDA 1988 Optionholders" and "- United  States
Federal Income Tax Considerations - Dissenting Persons."


                     AVAILABLE INFORMATION

Orbital is subject to the informational requirements of the  1934
Securities  Exchange  Act,  and  in  accordance  therewith  files
reports  and  other information with the SEC.  Such  reports  and
other  information filed with the SEC can be inspected and copied
at  the public reference facilities maintained by the SEC at Room
1024, 450 Fifth Street, N.W., Washington, D.C. 20549, and at  the
SEC's  Regional Offices at Seven World Trade Center, 13th  Floor,
New  York, New York 10048 and Northwest Atrium Center,  500  West
Madison  Street, Suite 1400, Chicago, Illinois 60661.  Copies  of
such  material  also  can be obtained from the  Public  Reference
Section  of the SEC, Washington, D.C. 20549 at prescribed  rates.
In  addition, material filed by Orbital can be inspected  at  the
offices  of  The  Nasdaq Stock Market, Reports  Section,  1735  K
Street N.W., Washington, D.C., 20006.


                         LEGAL MATTERS

Certain legal matters in connection with the Arrangement will  be
passed  upon  by Farris, Vaughan, Wills & Murphy,  Vancouver  and
Paul,  Weiss, Rifkind, Wharton & Garrison, New York, New York  on
behalf  of  MDA  and  by Ropes & Gray, Boston, Massachusetts  and
Davies,   Ward  &  Beck,  Toronto  on  behalf  of   Orbital   and
Acquisition.


      APPROVAL OF PROXY CIRCULAR BY MDA BOARD OF DIRECTORS

The  contents of this Proxy Circular and the sending  thereof  to
MDA Shareholders and MDA 1988 Optionholders has been approved  by
the MDA Board.

DATED  at  Richmond, British Columbia, this 6th day  of  October,
1995.


                               BY ORDER OF THE BOARD OF DIRECTORS


                                        /S/ Robert B. Wallis

                                      ROBERT B. WALLIS, Secretary






ACCOUNTANTS' CONSENT

The Board of Directors
Orbital Sciences Corporation

We consent to the incorporation by reference in the Registration
Statement on Form S-8 dated August 31, 1995 of Orbital Sciences
Corporation of our report dated May 25, 1995, except as to note
8(d) which is at September 29, 1995, with respect to the
consolidated balance sheets of MacDonald, Dettwiler and
Associates Ltd. as at March 31, 1995 and 1994, and the related
consolidated statements of earnings, retained earnings and
changes in financial position for each of the years in the three
year period ended March 31, 1995, which report appears in the
Form 8-K of Orbital Sciences Corporation dated October 19, 1995.



(Signed) KPMG Peat Marwick Thorne

Chartered Accountants

Vancouver, Canada
October 19, 1995



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