9:00 a.m. Conference Call with Financial Analysts and Investors to

                              be Webcast

DULLES, Va.Oct. 12, 2007--Orbital Sciences Corporation (NYSE:ORB) announced today that it will release its third quarter 2007 financial results prior to the opening of the market on Thursday, October 18, 2007. Orbital will also conduct a conference call with financial analysts and investors the same morning, beginning at 9:00 a.m. (EDT). The conference call will be hosted by:

    --  Mr. David W. Thompson, Chairman and Chief Executive Officer

    --  Mr. Garrett E. Pierce, Vice Chairman and Chief Financial
        Officer

    --  Mr. James R. Thompson, Vice Chairman and Chief Operating
        Officer

To listen to the conference call, dial (888) 541-8767, and use the conference ID number 20632898. A replay of the conference call will be available approximately two hours after the end of the call and will remain active until Thursday, October 25, 2007. For access to the replay of the conference call, dial (800) 642-1687 (international callers should dial (706) 645-9291) and use the same conference ID number.

For webcast registration and information, please visit Orbital's web site at http://www.orbital.com/Investor. The company advises participants to register at least 20 minutes prior to the call to download and install any necessary audio software.

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; 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.

More information about Orbital can be found at http://www.orbital.com.


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

    SOURCE: Orbital Sciences Corporation