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

Orbital Sciences Corporation
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®, Taurus®
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