<ARTICLE> 5
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED BALANCE SHEETS AND CONSOLIDATED STATEMENTS OF EARNINGS AT AND FOR
THE NINE MONTHS ENDED SEPTEMBER 30, 1998 AND IS QUALIFIED IN ITS ENTIRETY BY
REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<CIK> 0000820736
<NAME> ORBITAL SCIENCES CORP/DE/
<MULTIPLIER> 1000
       
                             
<PERIOD-TYPE>                   YEAR
<FISCAL-YEAR-END>                          DEC-31-1998
<PERIOD-START>                             JAN-01-1998
<PERIOD-END>                               SEP-30-1998
<CASH>                                          39,482
<SECURITIES>                                       225
<RECEIVABLES>                                  226,379
<ALLOWANCES>                                   (8,101)
<INVENTORY>                                     41,733
<CURRENT-ASSETS>                               310,391
<PP&E>                                         247,375
<DEPRECIATION>                                (98,755)
<TOTAL-ASSETS>                                 891,817
<CURRENT-LIABILITIES>                          212,914
<BONDS>                                        152,803
<PREFERRED-MANDATORY>                                0
<PREFERRED>                                          0
<COMMON>                                           370
<OTHER-SE>                                     527,611
<TOTAL-LIABILITY-AND-EQUITY>                   891,817
<SALES>                                        558,363
<TOTAL-REVENUES>                               558,363
<CGS>                                          409,645
<TOTAL-COSTS>                                  409,645
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                   721
<INTEREST-EXPENSE>                               1,484
<INCOME-PRETAX>                                 16,310
<INCOME-TAX>                                     3,131
<INCOME-CONTINUING>                             13,179
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                    13,179
<EPS-PRIMARY>                                     0.37
<EPS-DILUTED>                                     0.37