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)

                    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



             MACDONALD, DETTWILER AND ASSOCIATES LTD.

                   Consolidated Balance Sheets
                    (In thousands of Canadian dollars)

                                                  
                                         June 30,            March 31,
                                           1995          1995        1994
                                        (Unaudited)     _____        _____
                                                            
                  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)                                       


On behalf of the Board:



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

   See accompanying notes to consolidated financial statements.




             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)                                
                                                  
                                                                             
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




   See accompanying notes to consolidated financial statements





             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)                                                      

                                                                                  
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


   See accompanying notes to consolidated financial statements



             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)                   
                                                                         
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


   See accompanying notes to consolidated financial statements

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:


                                              June 30, 1995
                                                          
                                                Unaudited
                                Cost            Accumulated             Net
                                                Depreciation
                                 (000's)          (000's)                (000's)
                                                          
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


                                                 March 31, 1995

                                 Cost            Accumulated              Net
                                                 Depreciation
                                                                                    
                               (000's)             (000's)             (000's)
                                                              
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
                                                                                    
                                              March 31, 1994

                                Cost             Accumulated            Net
                                                 Depreciation
                                                                   
                               (000's)           (000's)               (000's)
                                                                                                                
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


     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:


                                               June 30,        March 31,
                                                 1995       1995      1994
                                              (Unaudited            
                                                (000's)    (000's)   (000's)
                                                            
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



     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).




                                               (Dollar amounts in thousands)
                                                              
                                             Common Shares         Contributed
                                                                     Surplus
                                                             
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                    -




        (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:


                                        June 30,              March 31,
                                          1995          1995          1994
                                        (Unaudited)                            
                                                             
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


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:



                                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)
                                                   

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



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:



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


7.   Supplementary information to the consolidated statements  of
     earnings:

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



                             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)
                                                  
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


               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.



                                                     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$)
                                               (C$)
                                                                                               
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 
                                                                                                                            



                                                                                                                            
                                                                                                                            
                                                     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$)
                                               (C$)
                                                                                              
                                                                                                                               
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
                                                                                                                            


                                                                                                                            
                                                                       
                                                     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$)
                                               (C$)
                                                                                               
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
                                                                                                                            




                                                                                                                            
                                                     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$)
                                               (C$)
                                                                                              
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
                                                                                                                            




                                                                                                                            
                                                     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$)              
                                               (C$)
                                                                   
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
                                                                                                                            




                                                     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$)
                                               (C$)
                                                                                              
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



                   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