DULLES, Va.May 23, 2005--Orbital Sciences Corporation (NYSE:ORB) announced today that its Chairman and Chief Executive Officer, Mr. David W. Thompson, will participate in a panel discussion entitled "Outlook for the Aerospace and Defense Supplier Sector" at Banc of America Securities 2005 Aerospace and Defense Suppliers Conference on Thursday, May 26. The panel discussion will begin at 12:30 p.m. (EDT).

A live audio webcast of the panel discussion will be available on Orbital's web site under the "For Investors" heading at www.orbital.com. An archived replay of the webcast will be available following the conference.

About Orbital

Orbital develops and manufactures small space and rocket systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-orbit, geosynchronous 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.

    CONTACT: Orbital Sciences Corporation
             Barron Beneski, 703-406-5528

    SOURCE: Orbital Sciences Corporation