Company on Track to Conduct First Launch of GMD Booster in Early 2003

DULLES, Va., Dec. 5 /PRNewswire-FirstCall/ -- Orbital Sciences Corporation (NYSE: ORB) announced today the successful test firing of the rocket motor that will serve as the first stage of the interceptor booster the company is developing for the U.S. Ground-based Missile Defense (GMD) system under a contract from The Boeing Company. Supplied by ATK's (Alliant Techsystems) (NYSE: ATK) Thiokol Propulsion division, an Orion solid-fuel rocket motor was test-fired for 70 seconds demonstrating its performance characteristics. The test also included a demonstration of the motor's thrust vector capability using a hydraulically-driven actuation system provided by Honeywell Engine Systems Division. The static firing is one of the final developmental steps for the rocket motor prior to launch. Orbital is currently planning to conduct the first launch of its GMD booster in early 2003.

"We are very pleased with the results of the static fire test of ATK's Orion motor," said Mr. Ron Grabe, Executive Vice President and General Manager of Orbital's Launch Systems Group. "For many years, ATK's Thiokol Propulsion has been a supplier of highly reliable rocket motors for Orbital's Pegasus and Taurus space launch vehicle programs. Similarly, Honeywell's thrust vector control systems have been successfully utilized on a number of Orbital's missile programs in the past. We are very proud to have both companies as key members of our team for the GMD booster program and congratulate them on the successful completion of the static fire test," he added.

Under a multi-year $900 million-plus contract (including options) from Boeing, Orbital is developing, testing and producing ground-based boost vehicles for America's ballistic missile defense system. As a key element of the U.S. Missile Defense Agency's (MDA) Ground-based Midcourse Defense system, Orbital's interceptor boost vehicles will carry advanced exoatmospheric kill vehicles that are designed to locate, track and destroy long-range enemy missiles in flight, protecting all 50 States from future attacks.

Orbital is one of the world's leading developers and manufacturers of affordable space systems for commercial, civil government and military customers. The company's primary products include low-orbit, geosynchronous and planetary spacecraft for communications, scientific and remote sensing missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense boosters that are used as target and interceptor vehicles. Orbital also offers space-related technical services to government agencies and develops and builds satellite-based transportation management systems for public transit and public works agencies, as well as private vehicle fleet operators.

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SOURCE Orbital Sciences Corporation

-0- 12/05/2002

/CONTACT: Barron Beneski, Public and Investor Relations, of Orbital Sciences Corporation, +1-703-406-5528, or Beneski.barron@orbital.com/