DULLES, Va., Feb 6, 2003 /PRNewswire-FirstCall via COMTEX/ --

Company Demonstrates GMD Rocket Vehicle's Design and Gathers Important Flight Data for Future Intercept Missions

Orbital Sciences Corporation (NYSE: ORB) announced today that it successfully launched the first prototype of the interceptor boost vehicle the company is developing and manufacturing for the U.S. Missile Defense Agency's (MDA) Ground-based Midcourse Defense (GMD) system under a contract from The Boeing Company. In a mission that originated from Vandenberg Air Force Base, California, Orbital's GMD boost vehicle was launched at 4:00 p.m. (EST). It flew a ballistic trajectory over the Pacific Ocean, reaching an altitude of approximately 1,125 miles and traveling about 3,500 miles down range from the launch site.

Following preliminary post-flight analysis of the data collected from the mission, Orbital confirmed that all the primary objectives for the first launch of the GMD boost vehicle were achieved. These included the verification of the vehicle design and flight characteristics, the gathering of flight data through comprehensive onboard instrumentation, and the confirmation of the expected performance of the propulsion system.

"With the successful launch of our inaugural GMD boost vehicle, we have completed the first step toward the full development of a high-performance, reliable booster to help defend our nation," said Mr. Ron Grabe, Executive Vice President and General Manager of Orbital's Launch Systems Group. "I would like to commend the joint Boeing/Orbital team and our key suppliers for maintaining an extremely aggressive schedule to design, produce, test and deliver a new boost vehicle for the Missile Defense Agency in just 13 months, from the start of the contract to today's successful launch," he added.

Under a contract from Boeing, Orbital is developing, manufacturing and testing interceptor boost vehicles for MDA's GMD system. The contract is valued at nearly $1 billion, including firm and optional orders. The firm portion of the company's contract, awarded in early 2002, is valued at approximately $450 million and extends through 2007. Orbital's GMD boost vehicle is a three-stage system based on flight-proven hardware that has flown over 40 times on missions carried out by the company's Pegasus(R), Taurus(R) and Minotaur space launch vehicles.

Orbital's space launch vehicles, missile defense boosters and related suborbital rockets are primarily produced at the company's engineering and manufacturing facility in Chandler, Arizona and its vehicle assembly and integration facilities at Vandenberg Air Force Base, California. The launch vehicles are used by commercial, civil government and military agencies to deliver small satellites into low altitude orbits above the Earth and in missile defense systems, both as threat-simulating target vehicles and potentially as interceptor boosters for U.S. national defense systems. Orbital is one of the world's leading developers and manufacturers of small space systems for commercial, civil government and military customers. The company employs approximately 2,000 people at major facilities in Virginia, Maryland, Arizona and California. In addition to its launch vehicle products, Orbital is a leading supplier of satellites, including low-orbit, geostationary and planetary spacecraft for communications, remote sensing and scientific missions. The company 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: Barron Beneski, Public and Investor Relations of Orbital Sciences Corporation, +1-703-406-5528, or Beneski.barron@orbital.com

SOURCE Orbital Sciences Corporation

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

URL:              http://www.orbital.com
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