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                                   EXHIBIT 11.
                 STATEMENT RE: COMPUTATION OF EARNINGS PER SHARE



THREE-MONTH PERIOD ENDED SEPTEMBER 30, 1999
- ---------------------------------------------------------------------------------------------
                                                                                   ASSUMING
                                                                  BASIC          DILUTION (2)
                                                              -------------      ------------
                                                                           
WEIGHTED AVERAGE OF OUTSTANDING SHARES                           37,384,519        37,384,519

COMMON EQUIVALENT SHARES:
     OUTSTANDING STOCK OPTIONS                                          N/A           613,951

OTHER POTENTIALLY DILUTIVE SECURITIES:
     CONVERTIBLE NOTES (1)                                              N/A         3,571,429

                                                              -------------      ------------
SHARES USED IN COMPUTING
NET INCOME PER COMMON SHARE                                      37,384,519        41,569,899
                                                              =============      ============


NET INCOME                                                    $ (32,649,000)     $(32,649,000)

ADJUSTMENTS ASSUMING DILUTION:
     INTEREST EXPENSE ADJUSTMENT, NET OF APPLICABLE TAXES               N/A         1,250,000

                                                              -------------      ------------
NET INCOME                                                    $ (32,649,000)     $(31,399,000)
                                                              =============      ============


NET INCOME PER COMMON SHARE (AS CALCULATED)                   $       (0.87)     $      (0.76)
                                                              =============      ============


NET INCOME PER COMMON SHARE                                   $       (0.87)     $      (0.87)
                                                              =============      ============




NINE-MONTH PERIOD ENDED SEPTEMBER 30, 1999
- ---------------------------------------------------------------------------------------------
                                                                                   ASSUMING
                                                                  BASIC          DILUTION (2)
                                                              -------------      ------------
                                                                           
WEIGHTED AVERAGE OF OUTSTANDING SHARES                           37,240,742        37,240,742

COMMON EQUIVALENT SHARES:
     OUTSTANDING STOCK OPTIONS                                          N/A           936,934

OTHER POTENTIALLY DILUTIVE SECURITIES:
     CONVERTIBLE NOTES (1)                                              N/A         3,571,429

                                                              -------------      ------------
SHARES USED IN COMPUTING
NET INCOME PER COMMON SHARE                                      37,240,742        41,749,105
                                                              =============      ============


NET INCOME                                                    $ (71,507,000)     $(71,507,000)

ADJUSTMENTS ASSUMING DILUTION:
     INTEREST EXPENSE ADJUSTMENT, NET OF APPLICABLE TAXES               N/A         3,750,000

                                                              -------------      ------------
NET INCOME                                                    $ (71,507,000)     $(67,757,000)
                                                              =============      ============


NET INCOME PER COMMON SHARE (AS CALCULATED)                   $       (1.92)     $      (1.62)
                                                              =============      ============


NET INCOME PER COMMON SHARE                                   $       (1.92)     $      (1.92)
                                                              =============      ============


NOTES:

(1) -    On September 16, 1997, the company sold $100 million of 5% convertible
         subordinated notes due October 2002. The notes are convertible at the
         option of the holders into Orbital common stock at a conversion price
         of $28.00 per share.



(2) -    Subsidiary stock options that enable holders to obtain subsidiary's
         common stock pursuant to effective stock option plans are included in
         computing the subsidiary's earnings per share, to the extent dilutive.
         Those earnings per share data are included in the Company's per share
         computations based on the Company's holdings of the subsidiary's stock.
         For the three and nine months ended September 30, 1999, all such
         subsidiary stock options were anti-dilutive