-- Revenues Increase 46%, Net Income Rises 84%, EPS Climbs to
                               $0.26 --

   -- Company Raises Guidance for 2007, Provides Preliminary Outlook
                              for 2008 --

DULLES, Va.Oct. 18, 2007--Orbital Sciences Corporation (NYSE:ORB) today announced its financial results for the third quarter and first nine months of 2007. Orbital's third quarter revenues increased 46% to $289.5 million in 2007, compared to $197.8 million in 2006. The company's third quarter operating income rose 54% to $23.2 million in 2007, compared to $15.1 million in 2006. Third quarter net income increased 84% to $15.7 million in 2007, compared to $8.5 million in 2006, and diluted earnings per share increased to $0.26, compared to $0.14 in the third quarter of 2006. Orbital reported third quarter 2007 free cash flow* of $22.4 million compared to free cash flow of $21.3 million in the third quarter of 2006.

Commenting on Orbital's third quarter 2007 results, Mr. David W. Thompson, Chairman and Chief Executive Officer, said, "The company reported strong revenue growth in all three of our business segments, boosted profit in most product lines, and generated solid free cash flow in the third quarter. Following the pattern established earlier in the year, communications satellites, human space systems and missile defense programs drove our revenue growth in the quarter."

For the first nine months of 2007, Orbital reported revenues of $791.0 million, up 35% compared to $587.0 million in the first nine months of 2006. The company's operating income for the first nine months of 2007 was $62.3 million, up 30% compared to $47.8 million during the same period in 2006. Net income for the first nine months of 2007 was $41.0 million, or $0.67 diluted earnings per share, compared to $27.3 million, or $0.44 diluted earnings per share, in the first nine months of 2006. Orbital generated $43.6 million of free cash flow in the first nine months of 2007, compared to $75.5 million during the same period in 2006.

* "Free cash flow" is a non-GAAP financial measure discussed in this release. For additional details, please refer to the sections of this press release entitled "Cash Flow and Balance Sheet" and "Disclosure of Non-GAAP Financial Measure."

Financial Highlights

Summary financial results for the third quarter of 2007 compared to the third quarter of 2006 were as follows (in millions, except per share data):

                                                       Third Quarter
                                                       2007     2006
----------------------------------------------------------------------
Revenues                                              $289.5   $197.8
Operating Income                                        23.2     15.1
Net Income                                              15.7      8.5
Diluted Net Income per Share                          $  0.26  $  0.14
----------------------------------------------------------------------

Summary financial results for the first nine months of 2007 compared to the first nine months of 2006 were as follows (in millions, except per share data):

                                                     First Nine Months
                                                       2007     2006
----------------------------------------------------------------------
Revenues                                              $791.0   $587.0
Operating Income                                        62.3     47.8
Net Income                                              41.0     27.3
Diluted Net Income per Share                          $  0.67  $  0.44
----------------------------------------------------------------------

Revenues

Revenues by segment for the third quarter were as follows (in millions):

                                                       Third Quarter
                                                       2007     2006
----------------------------------------------------------------------
Launch Vehicles                                       $100.3  $ 71.3
Satellites and Space Systems                           176.0   117.9
Transportation Management Systems                       13.8     9.4
Eliminations                                            (0.6)   (0.8)
                                                     -------- --------
Total Revenues                                        $289.5  $197.8
----------------------------------------------------------------------

Orbital's third quarter 2007 revenues were $289.5 million, up 46% compared to third quarter 2006 revenues of $197.8 million, due to increased revenues in all business segments. Satellites and space systems segment revenues increased $58.0 million, or 49%, driven by contract activity on the Orion human spacecraft program for NASA which began in late 2006, and growth in the communications satellites product line that was mainly due to activity on recently awarded contracts. Launch vehicles segment revenues increased $29.0 million, or 41%, principally due to higher target and interceptor vehicle revenues driven by increased contract activity on several missile defense programs. Transportation management systems segment revenues increased $4.4 million, or 46%, largely due to an increase in product sales supporting follow-on and replacement demand for public transit fleet management systems.

Revenues by segment for the first nine months were as follows (in millions):

                                                     First Nine Months
                                                       2007     2006
----------------------------------------------------------------------
Launch Vehicles                                       $290.8   $230.4
Satellites and Space Systems                           466.5    333.4
Transportation Management Systems                       36.2     26.8
Eliminations                                            (2.5)    (3.6)
                                                     -------- --------
Total Revenues                                        $791.0   $587.0
----------------------------------------------------------------------

For the first nine months of 2007, Orbital reported $791.0 million in revenues, up 35% compared to the same period last year due to increased revenues in all business segments. Satellites and space systems segment revenues increased $133.1 million, or 40%, driven by contract activity on the Orion program which began in late 2006 and growth in the communications satellites product line mainly due to activity on recently awarded contracts. Launch vehicles segment revenues increased $60.4 million, or 26%, primarily due to the same factors that drove the increase in quarterly results, most notably higher target vehicle product line revenue. Transportation management systems segment revenues increased $9.4 million, or 35%, primarily due to an increase in product sales supporting follow-on and replacement demand for fleet management systems.

Operating Income

Operating income by segment for the third quarter was as follows (in millions):

                                                        Third Quarter
                                                        2007    2006
----------------------------------------------------------------------
Launch Vehicles                                        $  10.5 $   7.4
Satellites and Space Systems                              11.4     7.1
Transportation Management Systems                          1.3     0.6
                                                       ------- -------
Total Operating Income                                 $  23.2 $  15.1
----------------------------------------------------------------------

Orbital reported operating income of $23.2 million in the third quarter of 2007, up 54% over the third quarter of 2006. This growth was due to a $4.3 million, or 61%, operating income increase in the satellites and space systems segment, a $3.1 million, or 38%, operating income increase in the launch vehicles segment and a $0.7 million, or 115%, operating income increase in the transportation management systems segment. The increase in operating income in the satellites and space systems segment was principally due to increased contract activity on the Orion program and new communications satellite programs. The increase in launch vehicles segment operating income was primarily due to increased activity levels on target and interceptor vehicle programs. The growth in the transportation management systems segment was largely attributable to the increase in product sales mentioned above.

Operating income by segment for the first nine months was as follows (in millions):

                                                     First Nine Months
                                                       2007     2006
----------------------------------------------------------------------
Launch Vehicles                                       $  28.9  $  25.3
Satellites and Space Systems                             31.1     21.0
Transportation Management Systems                         2.3      1.5
                                                     -------- --------
Total Operating Income                                $  62.3  $  47.8
----------------------------------------------------------------------

Orbital reported operating income of $62.3 million in the first nine months of 2007, up 30% over the first nine months of 2006. This increase was due to a $10.1 million, or 48%, increase in the satellites and space systems segment, a $3.6 million, or 14%, increase in the launch vehicles segment and a $0.7 million, or 49%, increase in the transportation management systems segment. The increases in operating income in all three segments were generally attributable to the same factors described above that drove the improvements in the third quarter results.

Net Income

Net income for the third quarter of 2007 was $15.7 million, or $0.26 diluted earnings per share, up from $8.5 million, or $0.14 diluted earnings per share, in the third quarter of 2006. Net income for the first nine months of 2007 was $41.0 million, or $0.67 diluted earnings per share, compared to $27.3 million, or $0.44 diluted earnings per share, in the same period of 2006.

Interest expense for the third quarter and first nine months of 2007 decreased to $1.3 million and $3.6 million, respectively, compared to $3.1 million and $9.3 million, respectively, in the same periods in 2006. The reduction in interest expense is due to lower interest rates on long-term debt as a result of Orbital's December 2006 refinancing transaction.

Diluted weighted-average shares outstanding decreased to 60.9 million in the third quarter of 2007 compared to 62.9 million in the third quarter of 2006 due to share repurchases made by the company. Diluted weighted-average shares outstanding in the first nine months of 2007 decreased to 61.0 million compared to 62.6 million in the first nine months of 2006, also driven by company share repurchases.

Cash Flow and Balance Sheet

Orbital reported free cash flow of $22.4 million for the third quarter of 2007. The company repurchased approximately 700,000 shares of its common stock for $15.0 million in the third quarter of 2007. This stock repurchase is part of a 12-month, $50 million securities repurchase program authorized by the company's Board of Directors in April 2007. Orbital's unrestricted cash and marketable securities balances were $197.8 million and $34.5 million, respectively, as of September 30, 2007.

The company's cash flow was as follows (in millions):

                                                   2007
                                      Third Quarter  First Nine Months
----------------------------------------------------------------------
Net Cash Provided by Operating
 Activities                          $     26.9      $     56.2
Capital Expenditures                       (4.5)          (12.6)
                                     --------------- -----------------
    Free Cash Flow                         22.4            43.6
Net Purchases of Marketable
 Securities                               (34.5)          (34.5)
Repurchase of Common Stock                (15.0)          (25.0)
Proceeds from Issuance of Common
 Stock                                      3.2            10.2
Other                                       2.2             3.7
                                     --------------- -----------------
     Net Decrease in Cash                 (21.7)           (2.0)
Beginning Cash Balance                    219.5           199.8
                                     --------------- -----------------
Ending Cash Balance                  $    197.8      $    197.8
----------------------------------------------------------------------

Summary balance sheet data as of September 30, 2007 was as follows (in millions):

              Assets                      Liabilities and Equity
----------------------------------------------------------------------
Cash                         $197.8 Current Liabilities         $206.4
Other Current Assets          312.6 Long-Term Debt               143.8
Non-Current Assets            268.5 Stockholders' Equity         428.7
                             ------                             ------
                                         Total Liabilities and
     Total Assets            $778.9       Equity                $778.9
----------------------------------------------------------------------

New Business Highlights

During the third quarter of 2007, Orbital received approximately $420 million in new firm and option contract bookings. In addition, the company received approximately $35 million of option exercises under existing contracts. Year-to-date, Orbital received approximately $1.51 billion in new firm and option contract bookings, and approximately $240 million of option exercises under existing contracts. As of September 30, 2007, the company's firm contract backlog was approximately $1.96 billion and its total backlog (including options, indefinite-quantity contracts and undefinitized orders) was approximately $4.06 billion.

Operational Highlights

The company conducted four spacecraft and launch vehicle missions in the third quarter. These operational events included the launch and preliminary check-out of Dawn, Orbital's first interplanetary spacecraft, developed for NASA's Jet Propulsion Laboratory. In addition, the company's long-range missile interceptor, the Orbital Boost Vehicle, achieved its sixth successful flight test as part of a Missile Defense Agency (MDA) national missile defense exercise. Orbital also carried out two MDA target vehicle launches in the third quarter.

During the third quarter, the company also delivered two satellites, two space payloads and five launch vehicles for future missions, including two OBV interceptors for operational deployments in California and Alaska.

In early October, two Orbital-built communications satellites, Intelsat-11 for Intelsat, Ltd. and Optus D2 for Optus Networks, Pty., were launched and are now undergoing in-orbit commissioning. During the remainder of 2007, the company expects to carry out one or two additional satellite launches and three to five additional rocket launches, and to complete and deliver four space payloads and several more launch vehicles for future missions.

2007 Financial Guidance

Orbital updated its financial guidance for full-year 2007, increasing its forecast for revenues, earnings per share and free cash flow as follows:

                                            Current        Previous
----------------------------------------------------------------------
Revenues (in millions)                   approx. $1,050 $975 - $1,000
Operating Income Margin                   approx. 8.0%  8.25% - 8.75%
Diluted Earnings Per Share               $0.89 - $0.91  $0.82 - $0.87
Free Cash Flow (in millions)               $65 - $70      $60 - $65
----------------------------------------------------------------------

2008 Preliminary Outlook

The company provided its preliminary financial guidance for 2008, as summarized in the table below:

                                                            2008
----------------------------------------------------------------------
Revenues (in millions)                                 $1,075 - $1,100
Operating Income Margin                                 8.25% - 8.50%
Diluted Earnings Per Share                              $0.93 - $0.98
Free Cash Flow (in millions)                              $75 - $80
----------------------------------------------------------------------

Orbital is considering the merits of a major new product development program to increase the payload capacity of its space launch vehicle platforms to include a medium-capacity rocket called Taurus II. Orbital believes that this new rocket could substantially expand the company's space launch market, yielding significant potential revenue growth in 2009 and beyond. However, the Taurus II program would entail a substantial development effort, the financial impact of which is not reflected in the 2008 guidance above. Orbital anticipates that this effort would require a net $40 million to $45 million use of cash in 2008. In addition, proceeding with the Taurus II program is expected to result in a revenue increase of up to $25 million and a $0.12 to $0.16 reduction in diluted earnings per share next year. The company plans to update its 2008 guidance, including its intentions with respect to the Taurus II program, when it reports fourth quarter and full-year 2007 results early in 2008.

Disclosure of Non-GAAP Financial Measure

Free cash flow is defined as GAAP (Generally Accepted Accounting Principles) net cash provided by operating activities (the most directly comparable GAAP financial measure) less capital expenditures for property, plant and equipment. A quantitative reconciliation of free cash flow to net cash provided by operating activities is included above in the section entitled "Cash Flow and Balance Sheet." Management believes that the company's presentation of free cash flow is useful because it provides investors with an important perspective on the company's liquidity, financial flexibility and ability to fund operations and service debt. Orbital does not intend for this non-GAAP financial measure to be considered in isolation or as a substitute for the related GAAP measure. Other companies may define this measure differently.

About Orbital

Orbital develops and manufactures small rockets and space systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-orbit, geosynchronous-orbit and planetary spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense systems that are used as interceptor and target vehicles. Orbital also offers space-related technical services to government agencies and develops and builds satellite-based transportation management systems for public transit agencies and private vehicle fleet operators.

"Safe Harbor" Statement Under the Private Securities Litigation Reform Act of 1995

Certain statements in this press release may be forward-looking in nature or "forward-looking statements" as defined in the Private Securities Litigation Reform Act of 1995. Such forward-looking statements are subject to risks, trends and uncertainties that could cause the actual results or performance of the company to be materially different from the forward-looking statement. Uncertainty surrounding factors such as continued government support and funding for key space and defense programs, new product development programs, product performance and market acceptance of products and technologies, the outcome of the government investigation, as well as other risk factors and business considerations described in the company's SEC filings, including its annual report on Form 10-K, could impact Orbital's actual financial and operational results. Orbital assumes no obligation for updating the information contained in this press release.

A transcript of the earnings teleconference call will be available on Orbital's website at http://www.orbital.com/Investor.

                     ORBITAL SCIENCES CORPORATION
               Condensed Consolidated Income Statements
                (in thousands, except per share data)

                                                      Third Quarter
                                                     2007      2006*
----------------------------------------------------------------------

Revenues                                           $289,456  $197,840
Costs of goods sold                                 241,541   159,991
                                                   --------- ---------
Gross profit                                         47,915    37,849
Research and development expenses                     4,297     2,559
Selling, general and administrative expenses         20,382    20,177
                                                   --------- ---------
Income from operations                               23,236    15,113
Interest expense                                     (1,341)   (3,097)
Interest income and other                             3,497     2,703
                                                   --------- ---------
Income before income taxes                           25,392    14,719
Income taxes                                         (9,714)   (6,189)
                                                   --------- ---------
Net income                                         $ 15,678  $  8,530
                                                   ========= =========

Basic net income per share                         $   0.26  $   0.14
                                                   ========= =========
Diluted net income per share                       $   0.26  $   0.14
                                                   ========= =========

Shares used in computing basic net income per
 share                                               59,176    60,390
Shares used in computing diluted net income per
 share                                               60,874    62,861
----------------------------------------------------------------------
* The company's 2006 financial statements have been restated as
 required by a new accounting standard pertaining to the company's L-
 1011 airplane which is used in the Pegasus launch vehicle program.
 The effect of the new accounting standard is not material to 2006 or
 2007 financial statements.
                     ORBITAL SCIENCES CORPORATION
               Condensed Consolidated Income Statements
                (in thousands, except per share data)

                                                     First Nine Months
                                                       2007    2006*
----------------------------------------------------------------------

Revenues                                             $790,951 $587,015
Costs of goods sold                                   656,835  472,891
                                                     -------- --------
Gross profit                                          134,116  114,124
Research and development expenses                      11,723    7,261
Selling, general and administrative expenses           60,092   59,033
                                                     -------- --------
Income from operations                                 62,301   47,830
Interest expense                                      (3,606)  (9,287)
Interest income and other                               9,563    8,329
                                                     -------- --------
Income before income taxes                             68,258   46,872
Income taxes                                         (27,298) (19,586)
                                                     -------- --------
Net income                                            $40,960  $27,286
                                                     ======== ========

Basic net income per share                              $0.69    $0.48
                                                     ======== ========
Diluted net income per share                            $0.67    $0.44
                                                     ======== ========

Shares used in computing basic net income per share    59,249   57,272
Shares used in computing diluted net income per
 share                                                 60,998   62,618
----------------------------------------------------------------------
* The company's 2006 financial statements have been restated as
 required by a new accounting standard pertaining to the company's L-
 1011 airplane which is used in the Pegasus launch vehicle program.
 The effect of the new accounting standard is not material to 2006 or
 2007 financial statements.
                     ORBITAL SCIENCES CORPORATION
                Condensed Consolidated Balance Sheets
                            (in thousands)

                                            September 30, December 31,
                                                2007         2006*
----------------------------------------------------------------------
Assets
 Cash                                        $    197,752 $    199,751
 Marketable securities                             34,500            -
 Receivables, net                                 189,015      165,235
 Inventory                                         30,278       30,053
 Deferred income taxes, net                        48,028       42,880
 Other current assets                              10,797       11,794
                                             ------------ ------------
      Total current assets                        510,370      449,713
Property, plant and equipment, net                 93,327       93,662
Goodwill                                           55,551       55,551
Deferred income taxes, net                        109,706      135,701
Other non-current assets                            9,908        9,349
                                             ------------ ------------
      Total Assets                           $    778,862 $    743,976
                                             ============ ============

Liabilities and Stockholders' Equity
Short-term borrowings                        $          - $        551
Accounts payable and accrued expenses             148,591      122,421
Deferred revenues                                  57,800       81,704
                                             ------------ ------------
     Total current liabilities                    206,391      204,676
Long-term debt                                    143,750      143,750
Total stockholders' equity                        428,721      395,550
                                             ------------ ------------
     Total Liabilities and Stockholders'
      Equity                                 $    778,862 $    743,976
                                             ============ ============
* The company's 2006 financial statements have been restated as
 required by a new accounting standard pertaining to the company's L-
 1011 airplane which is used in the Pegasus launch vehicle program.
 The effect of the new accounting standard is not material to 2006 or
 2007 financial statements.
                     ORBITAL SCIENCES CORPORATION
           Condensed Consolidated Statements of Cash Flows
                            (in thousands)

                                               September 30, 2007
                                           Third Quarter  Nine Months
----------------------------------------------------------------------

Net income                                 $     15,678  $     40,960
Depreciation                                      4,472        12,580
Deferred taxes                                    6,785        20,847
Changes in assets and liabilities                   962       (20,977)
Other                                              (987)        2,793
                                           ------------- -------------
Net cash provided by operating activities        26,910        56,203
                                           ------------- -------------
Capital expenditures                             (4,489)      (12,610)
Net purchases of marketable securities          (34,500)      (34,500)
Change in cash restricted for letters of
 credit, net                                      1,000             -
                                           ------------- -------------
Net cash used in investing activities           (37,989)      (47,110)
                                           ------------- -------------
Repurchase of common stock                      (15,000)      (25,000)
Net proceeds from issuance of common stock        3,202        10,241
Other                                             1,180         3,667
                                           ------------- -------------
Net cash used in financing activities           (10,618)      (11,092)
                                           ------------- -------------
Net decrease in cash                            (21,697)       (1,999)
Cash, beginning of period                       219,449       199,751
                                           ------------- -------------
Cash, end of period                        $    197,752  $    197,752
                                           ============= =============

    CONTACT: Orbital Sciences Corporation
             Barron Beneski, 703-406-5528
             Public and Investor Relations
             beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation