DULLES, Va.July 17, 2003--Orbital Sciences Corporation (NYSE:ORB) announced today that it will release its second quarter 2003 financial results prior to the opening of the market on Tuesday, July 22, 2003. Orbital will also conduct a conference call with financial analysts and investors the same morning, beginning at 9:00 a.m. (EST). 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 1766734. A replay of the conference call will be available approximately two hours after the end of the call and will remain active for one week, until Tuesday, July 29, 2003. 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.

The conference call will also be webcast. For webcast registration and information, please visit Orbital's web site at http://www.orbital.com/Investor. It is advisable to register at least 20 minutes prior to the call to download and install any necessary audio software. A transcript of the conference call will be posted on the investor relations section of Orbital's web site within 48 hours.

Orbital develops and manufactures small space systems for commercial, civil government and military customers. The company's primary products are satellites and launch vehicles, including low-orbit, geostationary and planetary spacecraft for communications, remote sensing and scientific missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense boosters 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
             Barron Beneski, 703-406-5528
             beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation