----

----

| þ | QUARTERLY      REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF      1934 |
|--------|---------------------------------------------------------------------------------------------------|
|   | For      the quarterly period ended March 31,2010                                                 |

| o      | TRANSITION      REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIESEXCHANGE      ACT OF 1934 |
|--------|---------------------------------------------------------------------------------------------------|
|   | For      the transition period from ______ to______                                               |

| Delaware                                    | 06-1209561                                |
|---------------------------------------------|-------------------------------------------|
| (State      of Incorporation of Registrant) | (I.R.S.      Employer Identification No.) |

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TABLE

|     |                  |                                                                                                | Page   |
|----------|-----------------------|-----------------------------------------------------------------------------------------------------|--------|
|     |                  |                                                                                                |   |
| PART I.  | FINANCIAL INFORMATION |                                                                                                |
|     |                  |                                                                                                |   |
|     | Item 1.               | Financial Statements                                                                                |   |
|     |                  |                                                                                                |   |
|     |                  | Condensed Consolidated Balance Sheets as of March 31, 2010 and      December 31, 2009               | 1      |
|     |                  |                                                                                                |   |
|     |                  | Condensed Consolidated Income Statements for the Quarters Ended      March 31, 2010 and 2009        | 2      |
|     |                  |                                                                                                |   |
|     |                  | Condensed Consolidated Statements of Cash Flows for the      Quarters Ended March 31, 2010 and 2009 | 3      |
|     |                  |                                                                                                |   |
|     |                  | Notes to Condensed Consolidated Financial      Statements                                           | 4      |
|     |                  |                                                                                                |   |
|     | Item 2.               | Management’s Discussion and Analysis of Financial Condition      and Results of Operations    | 17     |
|     |                  |                                                                                                |   |
|     | Item 3.               | Quantitative and Qualitative Disclosures About Market      Risk                                     | 26     |
|     |                  |                                                                                                |   |
|     | Item 4.               | Controls and Procedures                                                                             | 27     |
|     |                  |                                                                                                |   |
| PART II. | OTHER INFORMATION     |                                                                                                |
|     |                  |                                                                                                |   |
|     | Item 1.               | Legal Proceedings                                                                                   | 28     |
|     |                  |                                                                                                |   |
|     | Item 1A.              | Risk Factors                                                                                        | 28     |
|     |                  |                                                                                                |   |
|     | Item 2.               | Unregistered Sales of Equity Securities and Use of      Proceeds                                    | 28     |
|     |                  |                                                                                                |   |
|     | Item 3.               | Defaults Upon Senior Securities                                                                     | 28     |
|     |                  |                                                                                                |   |
|     | Item 4.               | Removed and Reserved                                                                                | 28     |
|     |                  |                                                                                                |   |
|     | Item 5.               | Other Information                                                                                   | 28     |
|     |                  |                                                                                                |   |
|     | Item 6.               | Exhibits                                                                                            | 28     |
|     |                  |                                                                                                |   |
|     |                  |                                                                                                |

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Table of Contents

| PART I |
|--------|

| ITEM 1.   FINANCIAL    STATEMENTS |
|--------------------------------------------------|

| ORBITAL SCIENCESCORPORATION |
|-----------------------------|

|                                                                                      |   | March      31, |    |   | December      31, |   |
|-------------------------------------------------------------------------------------------|--------|----------------|---------|--------|-------------------|--------|
|                                                                                      |   | 2010           |    |   | 2009              |   |
| ASSETS                                                                                    |   |           |    |   |              |   |
| Current      assets:                                                                      |   |           |    |   |              |   |
| Cash      and cash equivalents                                                            |   | $              | 372,065 |   |              | $      | 372,986 |   |
| Receivables,      net                                                                     |   |           | 225,441 |   |              |   | 199,482 |   |
| Inventories,      net                                                                     |   |           | 39,960  |   |              |   | 38,662 |   |
| Deferred      income taxes, net                                                           |   |           | 39,430  |   |              |   | 37,902 |   |
| Other      current assets                                                                 |   |           | 31,987  |   |              |   | 14,258 |   |
| Total      current assets                                                                 |   |           | 708,883 |   |              |   | 663,290 |   |
| Investments                                                                               |   |           | 12,600  |   |              |   | 13,100 |   |
| Property,      plant and equipment, net                                                   |   |           | 142,818 |   |              |   | 133,275 |   |
| Goodwill                                                                                  |   |           | 55,551  |   |              |   | 55,551 |   |
| Deferred      income taxes, net                                                           |   |           | 44,642  |   |              |   | 50,326 |   |
| Other      non-current assets                                                             |   |           | 13,948  |   |              |   | 13,939 |   |
| Total      assets                                                                         |   | $              | 978,442 |   |              | $      | 929,481 |   |
|                                                                                      |   |           |    |   |              |   |   |   |
| LIABILITIES      AND STOCKHOLDERS’ EQUITY                                           |   |           |    |   |              |   |   |   |
| Current      liabilities:                                                                 |   |           |    |   |              |   |   |   |
| Accounts      payable and accrued expenses                                                |   | $              | 190,386 |   |              | $      | 171,805 |   |
| Deferred      revenues and customer advances                                              |   |           | 136,453 |   |              |   | 127,056 |   |
| Total      current liabilities                                                            |   |           | 326,839 |   |              |   | 298,861 |   |
| Long-term      obligations                                                                |   |           | 121,566 |   |              |   | 120,274 |   |
| Other      non-current liabilities                                                        |   |           | 7,588   |   |              |   | 7,886 |   |
| Total      liabilities                                                                    |   |           | 455,993 |   |              |   | 427,021 |   |
| Commitments      and contingencies                                                        |   |           |    |   |              |   |   |   |
| Stockholders’      equity:                                                          |   |           |    |   |              |   |   |   |
| Preferred      Stock, par value $.01; 10,000,000 shares authorized, none      outstanding |   |           | — |   |              |   | — |   |
| Common      Stock, par value $.01; 200,000,000 shares authorized, 57,562,870      and     |   |           |    |   |              |   |   |   |
| 56,879,528      shares outstanding, respectively                                          |   |           | 576     |   |              |   | 569 |   |
| Additional      paid-in capital                                                           |   |           | 550,284 |   |              |   | 539,235 |   |
| Accumulated      other comprehensive loss                                                 |   |           | (2,241  | )      |              |   | (1,906 | ) |
| Accumulated      deficit                                                                  |   |           | (26,170 | )      |              |   | (35,438 | ) |
| Total      stockholders’ equity                                                     |   |           | 522,449 |   |              |   | 502,460 |   |
| Total      liabilities and stockholders’ equity                                     |   | $              | 978,442 |   |              | $      | 929,481 |   |

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ORBITAL

|                                              |   | Quarters      Ended March 31, |    |
|---------------------------------------------------|--------|-------------------------------|---------|
|                                              |   | 2010                          |    |   | 2009 |   |
|                                              |   |                          |    |   |   |   |
| Revenues                                          |   | $                             | 296,190 |   |   | $ | 295,741 |   |
| Cost      of revenues                             |   |                          | 227,902 |   |   |   | 246,348 |   |
| Research      and development expenses            |   |                          | 30,163  |   |   |   | 18,971 |   |
| Selling,      general and administrative expenses |   |                          | 20,760  |   |   |   | 19,258 |   |
| Income      from operations                       |   |                          | 17,365  |   |   |   | 11,164 |   |
| Interest      income and other                    |   |                          | 338     |   |   |   | 5,663 |   |
| Interest      expense                             |   |                          | (2,361  | ) |   |   | (2,257 | ) |
| Investment      impairment charge                 |   |                          | — |   |   |   | (700 | ) |
| Income      before income taxes                   |   |                          | 15,342  |   |   |   | 13,870 |   |
| Income      tax provision                         |   |                          | (6,074  | ) |   |   | (4,668 | ) |
| Net      income                                   |   | $                             | 9,268   |   |   | $ | 9,202 |   |
|                                              |   |                          |    |   |   |   |   |   |
| Basic      income per share                       |   | $                             | 0.16    |   |   | $ | 0.16 |   |
|                                              |   |                          |    |   |   |   |   |   |
| Diluted      income per share                     |   | $                             | 0.16    |   |   | $ | 0.16 |   |

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ORBITAL 

|                                                                                        |   | Quarters      Ended March 31, |    |
|---------------------------------------------------------------------------------------------|--------|-------------------------------|---------|
|                                                                                        |   | 2010                          |    |   | 2009 |   |
| Operating      Activities:                                                                  |   |                          |    |   |   |   |
| Net      income                                                                             |   | $                             | 9,268   |   |   | $ | 9,202 |   |
| Adjustments      to reconcile net income to net cash provided by operating      activities: |   |                          |    |   |   |   |   |   |
| Depreciation      expense                                                                   |   |                          | 5,243   |   |   |   | 4,876 |   |
| Deferred      income taxes                                                                  |   |                          | 4,053   |   |   |   | 4,046 |   |
| Investment      impairment charge                                                           |   |                          | — |   |   |   | 700 |   |
| Stock-based      compensation and other                                                     |   |                          | 3,020   |   |   |   | 3,837 |   |
| Changes      in assets and liabilities                                                      |   |                          | (16,834 | ) |   |   | (6,595 | ) |
| Net      cash provided by operating activities                                              |   |                          | 4,750   |   |   |   | 16,066 |   |
|                                                                                        |   |                          |    |   |   |   |   |   |
| Investing      Activities:                                                                  |   |                          |    |   |   |   |   |   |
| Capital      expenditures                                                                   |   |                          | (15,097 | ) |   |   | (5,897 | ) |
| Net      cash used in investing activities                                                  |   |                          | (15,097 | ) |   |   | (5,897 | ) |
|                                                                                        |   |                          |    |   |   |   |   |   |
| Financing      Activities:                                                                  |   |                          |    |   |   |   |   |   |
| Net      proceeds from issuances of common stock                                            |   |                          | 7,899   |   |   |   | 529 |   |
| Repurchase      of common stock                                                             |   |                          | — |   |   |   | (14,580 | ) |
| Tax      benefit of stock-based compensation                                                |   |                          | 1,527   |   |   |   | 70 |   |
| Net      cash provided by (used in) financing activities                                    |   |                          | 9,426   |   |   |   | (13,981 | ) |
|                                                                                        |   |                          |    |   |   |   |   |   |
| Net      decrease in cash and cash equivalents                                              |   |                          | (921    | ) |   |   | (3,812 | ) |
| Cash      and cash equivalents, beginning of period                                         |   |                          | 372,986 |   |   |   | 328,307 |   |
| Cash      and cash equivalents, end of period                                               |   | $                             | 372,065 |   |   | $ | 324,495 |   |

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NOTES

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| ·   | Launch      Vehicles.  Rockets that are used as interceptor and      target vehicles for missile defense systems, small- and medium-class space      launch vehicles that place satellites into Earth orbit and escape      trajectories, and suborbital launch vehicles that place payloads into a      variety of high-altitudetrajectories. |
|--------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Satellites and Space      Systems.  Small- and medium-class spacecraft that are      used to enable global and regional communications and broadcasting, to      conduct space-related scientific research, to carry out interplanetary and      other deep-space exploration missions, to enable national security      applications, to collect imagery and other remotely-sensed data about the      Earth and to demonstrate new space  technologies. |
|--------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Advanced Space      Programs.  Human-rated space systems for Earth-orbit and      lunar exploration, and small- and medium-class satellites and satellite      subsystems primarily used for national security space programs and to      demonstrate new space technologies. |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

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|                               |   | Quarters      Ended March 31, |    |
|------------------------------------|--------|-------------------------------|---------|
|                               |   | 2010                          |    |   | 2009 |   |
| Launch      Vehicles:              |   |                          |    |   |   |   |
| Revenues(1)                        |   | $                             | 100,342 |   |   | $ | 119,240 |   |
| Operating      income              |   |                          | 4,531   |   |   |   | 4,286 |   |
| Identifiable      assets           |   |                          | 182,780 |   |   |   | 151,249 | (2) |
| Capital      expenditures          |   |                          | 10,216  |   |   |   | 1,460 |   |
| Depreciation                       |   |                          | 1,806   |   |   |   | 1,611 |   |
| Satellites      and Space Systems: |   |                          |    |   |   |   |   |   |
| Revenues(1)                        |   | $                             | 100,521 |   |   | $ | 110,157 |   |
| Operating      income              |   |                          | 7,707   |   |   |   | 7,800 |   |
| Identifiable      assets           |   |                          | 192,166 |   |   |   | 178,233 | (2) |
| Capital      expenditures          |   |                          | 1,530   |   |   |   | 3,524 |   |
| Depreciation                       |   |                          | 2,265   |   |   |   | 2,176 |   |
| Advanced      Space Programs:      |   |                          |    |   |   |   |   |   |
| Revenues(1)                        |   | $                             | 107,543 |   |   | $ | 68,346 |   |
| Operating      income              |   |                          | 5,127   |   |   |   | (922 | ) |
| Identifiable      assets           |   |                          | 101,962 |   |   |   | 91,981 | (2) |
| Capital      expenditures          |   |                          | 2,510   |   |   |   | 578 |   |
| Depreciation                       |   |                          | 3       |   |   |   | 3 |   |
| Corporate      and Other:          |   |                          |    |   |   |   |   |   |
| Revenues(1)                        |   | $                             | (12,216 | ) |   | $ | (2,002 | ) |
| Operating      income              |   |                          | — |   |   |   | — |   |
| Identifiable      assets           |   |                          | 501,534 |   |   |   | 508,018 | (2) |
| Capital      expenditures          |   |                          | 841     |   |   |   | 335 |   |
| Depreciation                       |   |                          | 1,169   |   |   |   | 1,086 |   |
| Consolidated:                      |   |                          |    |   |   |   |   |   |
| Revenues                           |   | $                             | 296,190 |   |   | $ | 295,741 |   |
| Operating      income              |   |                          | 17,365  |   |   |   | 11,164 |   |
| Identifiable      assets           |   |                          | 978,442 |   |   |   | 929,481 | (2) |
| Capital      expenditures          |   |                          | 15,097  |   |   |   | 5,897 |   |
| Depreciation                       |   |                          | 5,243   |   |   |   | 4,876 |   |

|   |  (1)  Corporate      and other revenues are comprised solely of the elimination of intersegment      sales.  Launch vehicles segment revenues include $10.5 million      and $0.9 million of intersegment sales in the quarters ended March 31,      2010 and 2009, respectively.  Satellites and space systems      segment revenues include $1.3 million and $1.0 million of intersegment      sales in the quarters ended March 31, 2010 and 2009,      respectively.  Advanced space programs segment revenues include      $0.4 million and $0.1 million of intersegment sales in the quarters ended      March 31, 2010 and 2009,respectively. |
|--------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | (2)  As      of December 31, 2009. |
|--------|----------------------------------------------|

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| (3) | Earnings      Per Share |
|-----|-------------------------|

|                      |   |                                                    |                                                  | Quarters      Ended March 31, |   |
|---------------------------|--------|---------------------------------------------------------|-------------------------------------------------------|-------------------------------|--------|
| Numerator                 |   | 2010                                                    |                                                  |                          | 2009   |   |
|                      |   | Net      income                                         |                                                  | $                             | 9,268  |   |   | $ | 9,202 |   |
|                      |   | Percentage      allocated to shareholders (1)           |                                                  |                          | 99.2   | % |   |   | 98.5 | % |
|                      |   | Numerator      for basic and diluted earnings per share |                                                  | $                             | 9,193  |   |   | $ | 9,064 |   |
|                      |   |                                                    |                                                  |                          |   |   |   |   |   |   |
| Denominator               |   |                                                    |                                                  |                          |   |   |   |   |
|                      |   | Denominator      for basic earnings per share -         |                                                  |                          |   |   |   |   |   |   |
|                      |   | weighted-average      shares outstanding                |                                                  |                          | 57,060 |   |   |   | 57,189 |   |
|                      |   | Dilutive      effect of stock options                   |                                                  |                          | 796    |   |   |   | 664 |   |
|                      |   | Denominator      for diluted earnings per share         |                                                  |                          | 57,856 |   |   |   | 57,853 |   |
|                      |   |                                                    |                                                  |                          |   |   |   |   |   |   |
| Per      share income     |   |                                                    |                                                  |                          |   |   |   |   |
|                      |   | Basic                                                   |                                                  | $                             | 0.16   |   |   | $ | 0.16 |   |
|                      |   | Diluted                                                 |                                                  |                          | 0.16   |   |   |   | 0.16 |   |
|                      |   |                                                    |                                                  |                          |   |   |   |   |   |   |
| _________________________ |   |                                                    |                                                  |                          |   |   |   |   |
|                      |   |  (1)                                               | Basic      weighted-average shares outstanding        |                          |   | 57,060 |   |   |   | 57,189 |   |
|                      |   |                                                    | Basic      weighted-average shares outstanding and    |                          |   |   |   |   |   |   |   |
|                      |   |                                                    | unvested      restricted stock units expected to vest |                          |   | 57,536 |   |   |   | 58,063 |   |
|                      |   |                                                    | Percentage      allocated to shareholders             |                          |   | 99.2 | % |   |   | 98.5 | % |

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|     |   | March      31, |    |   | December      31, |   |
|----------|--------|----------------|---------|--------|-------------------|--------|
|     |   | 2010           |    |   | 2009              |   |
| Billed   |   | $              | 47,822  |   |              | $      | 53,157 |   |
| Unbilled |   |           | 177,619 |   |              |   | 146,325 |   |
| Total    |   | $              | 225,441 |   |              | $      | 199,482 |   |

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|      |   | March      31, 2010         |   |   | December      31, 2009          |   |
|-----------|--------|-----------------------------|--------|--------|---------------------------------|--------|
|      |   | Cost      or Amortized Cost |   |   | Net      Unrealized Gain (Loss) |   |   | Fair      Value |   |   | Cost      or Amortized Cost |   |   | Net      Unrealized Gain (Loss) |   |   | Fair      Value |   |
| Debt      |   | $                           | 11,400 |   |                            | $      | (900 | ) |   | $ | 10,500 |   |   | $ | 11,400 |   |   | $ | (500 | ) |   | $ | 10,900 |   |
| Equity(1) |   |                        | 2,000  |   |                            |   | 100 |   |   |   | 2,100 |   |   |   | 2,000 |   |   |   | 200 |   |   |   | 2,200 |   |
| Total     |   | $                           | 13,400 |   |                            | $      | (800 | ) |   | $ | 12,600 |   |   | $ | 13,400 |   |   | $ | (300 | ) |   | $ | 13,100 |   |
|      |   |                        |   |   |                            |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |   |

|                                         |   | Quarters      Ended March 31, |    |
|----------------------------------------------|--------|-------------------------------|---------|
|                                         |   | 2010                          |    |   | 2009 |   |
| Debt Securities                              |   |                          |    |   |   |   |
| Fair      value at beginning of period       |   | $                             | 10,900  |   |   | $ | 12,900 |   |
| Temporary      impairment charges            |   |                          | (400    | ) |   |   | (100 | ) |
| Fair      value at end of period             |   | $                             | 10,500  |   |   | $ | 12,800 |   |
|                                         |   |                          |    |   |   |   |   |   |
|                                         |   |                          |    |   |   |   |   |   |
| Equity      Securities                       |   |                          |    |   |   |   |   |   |
| Fair      value at beginning of period       |   | $                             | 2,200   |   |   | $ | 3,800 |   |
| Temporary      impairment charges            |   |                          | (100    | ) |   |   | (1,200 | ) |
| Other-than-temporary      impairment charges |   |                          | — |   |   |   | (700 | ) |
| Net      change in fair value                |   |                          | (100    | ) |   |   | (1,900 | ) |
| Fair      value at end of period             |   | $                             | 2,100   |   |   | $ | 1,900 |   |
|                                         |   |                          |    |   |   |   |   |   |
|                                         |   |                          |    |   |   |   |   |   |
| Total                                        |   |                          |    |   |   |   |   |   |
| Fair      value at beginning of period       |   | $                             | 13,100  |   |   | $ | 16,700 |   |
| Temporary      impairment charges            |   |                          | (500    | ) |   |   | (1,300 | ) |
| Other-than-temporary      impairment charges |   |                          | — |   |   |   | (700 | ) |
| Net      change in fair value                |   |                          | (500    | ) |   |   | (2,000 | ) |
| Fair      value at end of period             |   | $                             | 12,600  |   |   | $ | 14,700 |   |

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|                                   |   | Quarters      Ended March 31, |   |
|----------------------------------------|--------|-------------------------------|--------|
|                                   |   | 2010                          |   |   | 2009 |   |
|                                   |   |                          |   |   |   |   |
| Net      income                        |   | $                             | 9,268  |   |   | $ | 9,202 |   |
| Unrealized      loss on investments    |   |                          | (500   | ) |   |   | (1,300 | ) |
| Defined      benefit plans, net of tax |   |                          | 166    |   |   |   | (318 | ) |
| Total      comprehensive income        |   | $                             | 8,934  |   |   | $ | 7,584 |   |

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|                                  | Restricted      Stock Units | Stock      Options |
|---------------------------------------|-----------------------------|--------------------|
|                                  |                        |               | Weighted      Average |   |   | Weighted      Average |
|                                  | Number      of              |               | Measurement | Number      of |   | Exercise |
|                                  | Units                       |               | Date      Fair Value | Options |   | Price |
| Outstanding      at December 31, 2009 |  473,615               |               |  $22.88 |  2,301,305 |   |   | $       8.29 |   |
| Granted      (1)                      |  24,970                |               |  16.02 |  — |   |   |  — |   |
| Exercised                             | —                     |               |  — |  (636,990 | )  |   |  11.65 |   |
| Vested                                |  (21,677               | )             |  19.05 |  — |   |   |  — |   |
| Forfeited                             |  (1,032                | )             |  24.88 |  (1,466 | )  |   |  5.79 |   |
| Expired                               |  —               |               |  — |  (21,000 | )  |   |  18.50 |   |
| Outstanding      at March 31, 2010    |  475,876               |               |  $22.67 |  1,641,849 | (2) |   | $       6.86 |   |

| (1)   | The      fair value of restricted stock unit grants is determined based on the      closing market price of Orbital’s common stock on the date of      grant.  Such value is recognized as expense over the service      period, net of estimatedforfeitures. |
|-----------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|    (2)   | The      weighted average remaining contractual term is 2.40  years. |
|-----------------------------------|----------------------------------------------------------------------|

|                                                                                          |   | Quarters      Ended March 31, |
|-----------------------------------------------------------------------------------------------|--------|------------------------------------|
| (in      millions)                                                                            |   | 2010                               |   | 2009 |
| Stock-based      compensation expense                                                         |   | $                                  | 1.8 |   |   | $ | 2.5 |   |
| Income      tax benefit related to stock-based compensation expense                           |   |                               |  0.7 |   |   |   |  0.8 |   |
| Intrinsic      value of options exercised computed as the market                              |   |                               |   |   |   |   |   |   |
|         price on the exercise date less the price paid to exercise the      options |   |                               |  4.3 |   |   |   |  0.2 |   |
| Cash      received from exercise of options                                                   |   |                               |  7.4 |   |   |   |  0.2 |   |
| Tax      benefit recorded as credits to additional paid-in capital      related               |   |                               |   |   |   |   |   |   |
|         to stock-based compensation transactions                                    |   |                               |  1.5 |   |   |   |  0.1 |   |

|                                                                                                  |   | As      of          |   |
|-------------------------------------------------------------------------------------------------------|--------|---------------------|--------|
| (in      millions)                                                                                    |   | March      31, 2010 |   |
| Shares      of common stock available for grant under stock-based incentive      plans                |   |                | 1.6    |   |
| Aggregate      intrinsic value of restricted stock units that are expected to      vest               |   | $                   | 8.1    |   |
| Unrecognized      compensation expense related to non-vested restricted stock units,      expected to |   |                |   |   |
| be      recognized over a weighted-average period of 1.16 years                                       |   |                | 5.9    |   |
| Aggregate      intrinsic value of stock options outstanding, all fully    vested                      |   |                | 19.9   |   |

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ITEM 2

| ·   | Launch      Vehicles.  Rockets that are used as interceptor and      target vehicles for missile defense systems, small- and medium-class space      launch vehicles that place satellites into Earth orbit and escape      trajectories, and suborbital launch vehicles that place payloads into a      variety of high-altitudetrajectories. |
|--------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| · | Satellites and Space      Systems.  Small- and medium-class spacecraft that are      used to enable global and regional communications and broadcasting, to      conduct space-related scientific research, to carry out interplanetary and      other deep-space exploration missions, to enable national security      applications, to collect imagery and other remotely-sensed data about the      Earth and demonstrate new spacetechnologies. |
|--------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| ·   | Advanced Space      Programs.  Human-rated space systems for Earth-orbit and      lunar exploration, and small- and medium-class satellites and satellite      subsystems primarily used for national security space programs and to      demonstrate new space technologies. |
|--------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

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|                                    |   | First      Quarter |    |   |   |   |
|-----------------------------------------|--------|--------------------|---------|--------|--------|--------|
| (in      thousands, except percentages) |   | 2010               |    |   | 2009   |   |   | %      Change |   |
| Revenues                                |   | $                  | 100,342 |   |   | $      | 119,240 |   |   |   | (16% | ) |
| Operating      income                   |   |               | 4,531   |   |   |   | 4,286 |   |   |   | 6% |   |
| Operating      margin                   |   |               | 4.5     | %      |   |   | 3.6 | % |   |   |   |   |

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|                                    |   | First      Quarter |    |   |   |   |
|-----------------------------------------|--------|--------------------|---------|--------|--------|--------|
| (in      thousands, except percentages) |   | 2010               |    |   | 2009   |   |   | %      Change |   |
| Revenues                                |   | $                  | 100,521 |   |   | $      | 110,157 |   |   |   | (9% | ) |
| Operating      income                   |   |               | 7,707   |   |   |   | 7,800 |   |   |   | (1% | ) |
| Operating      margin                   |   |               | 7.7     | %      |   |   | 7.1 | % |   |   |   |   |

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|                                    |   | First      Quarter |    |   |   |   |
|-----------------------------------------|--------|--------------------|---------|--------|--------|--------|
| (in      thousands, except percentages) |   | 2010               |    |   | 2009   |   |   | %      Change |   |
| Revenues                                |   | $                  | 107,543 |   |   | $      | 68,346 |   |   |   | 57% |   |
| Operating      income                   |   |               | 5,127   |   |   |   | (922 | ) |   |   | — |   |
| Operating      margin                   |   |               | 4.8     | %      |   |   | (1.3 | %) |   |   |   |   |

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ITEM 3

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| ITEM 4.   CONTROLS AND      PROCEDURES |
|-------------------------------------------------------|

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PART II

ITEM 1

ITEM 1A.  RISK FACTORS

| ITEM 2.     UNREGISTERED      SALES OF EQUITY SECURITIES AND USE OFPROCEEDS |
|------------------------------------------------------------------------------------------------------|

|   | (a) | None. |
|--------|-----|-------|
|   | (b) | None. |
|   | (c) | None. |

| ITEM 3.     DEFAULTS UPON      SENIOR SECURITIES |
|---------------------------------------------------------------------------|

| ITEM 4.     REMOVED AND      RESERVED |
|----------------------------------------------------------------|

| ITEM 5.     OTHER      INFORMATION |
|-------------------------------------------------------------|

| ITEM      6.     EXHIBITS |
|----------------------------------------------------|

|   | (a) | Exhibits – A      complete listing of exhibits required is given in the Exhibit      Index. |
|--------|-----|---------------------------------------------------------------------------------------------------|

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|                                  | ORBITAL      SCIENCES CORPORATION |
|---------------------------------------|-----------------------------------|
|                                  |                              |   |
|                                  |                              |   |
| DATED:  April      23, 2010 | By:                               | /s/      David W. Thompson |
|                                  |                              | David      W. Thompson |
|                                  |                              | Chairman      and Chief Executive Officer |
|                                  |                              |   |
|                                  |                              |   |
| DATED:  April      23, 2010 | By:                               | /s/      Garrett E. Pierce |
|                                  |                              | Garrett      E. Pierce |
|                                  |                              | Vice      Chairman and Chief FinancialOfficer |

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| Exhibit No. | Description                                                                                                                                                                                                                                                       |
|-------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| 3.1         | Restated      Certificate of Incorporation (incorporated by reference to Exhibit 4.1 to      the company’s Registration Statement on Form S-3 (File Number 333-08769)      filed and effective on July 25, 1996).                                                |
| 3.2         | Amended      and Restated Bylaws (incorporated by reference to Exhibit 3.2 to the      company’s Quarterly Report on Form 10-Q for the quarter ended June 30,      2005).                                                                                        |
| 3.3         | Certificate      of Amendment to Restated Certificate of Incorporation, dated April 29,      1997 (incorporated by reference to Exhibit 3.3 to the company’s Annual      Report on Form 10-K for the fiscal year ended December 31,      1998).                  |
| 3.4         | Certificate      of Amendment to Restated Certificate of Incorporation, dated April 30,      2003 (incorporated by reference to Exhibit 3.4 to the company’s Quarterly      Report on Form 10-Q for the quarter ended June 30,  2003).                           |
| 4.1         | Form      of Certificate of Common Stock (incorporated by reference to Exhibit 4.1      to the company’s Registration Statement on Form S-1 (File Number 33-33453)      filed on February 9, 1990 and effective on April 24,  1990).                             |
| 4.2         | Indenture      dated as of December 13, 2006, by and between Orbital Sciences Corporation      and The Bank of New York, as Trustee (incorporated by reference to Exhibit      4.1 to the company’s Current Report on Form 8-K filed on December 13,      2006). |
| 4.3         | Form      of 2.4375% Convertible Senior Subordinated Note due 2027 (incorporated by      reference to Exhibit 4.2 to the company’s Current Report on Form 8-K filed      on December 13, 2006).                                                                  |
| 31.1        | Certification      of Chairman and Chief Executive Officer pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002 (18 U.S.C. Section 1350) (transmitted      herewith).                                                                                        |
| 31.2        | Certification      of Vice Chairman and Chief Financial Officer pursuant to Section 302 of      the Sarbanes-Oxley Act of 2002 (18 U.S.C. Section 1350) (transmitted      herewith).                                                                                   |
| 32.1        | Written      Statement of Chairman and Chief Executive Officerpursuant      to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. Section 1350)      (transmitted herewith).                                                                                     |
| 32.2        | Written      Statement of Vice Chairman and Chief Financial Officerpursuant      to Section 906 of the Sarbanes-Oxley Act of 2002 (18 U.S.C. Section 1350)      (transmitted herewith).                                                                                |