DULLES, Va.Dec. 15, 2004--

Mach 2.5 Target Vehicle Demonstrates 30-Foot Low Altitude Performance

                         and High-G Maneuvers

Orbital Sciences Corporation (NYSE:ORB) announced today that it successfully flight-tested the U.S. Navy's GQM-163A "Coyote" Supersonic Sea-Skimming Target (SSST) system for the Naval Air Systems Command (NAVAIR) on December 14, 2004. The flight test was conducted at the Navy's missile test range at Point Mugu in southern California and was the third consecutive successful flight in a series of progressively demanding missions that Orbital has carried out during the last two years. Orbital was awarded a development contract in 2000 to meet the Navy's requirement for an affordable SSST to simulate high-speed anti-ship cruise missiles for fleet training and weapon systems research, development, test and evaluation.

Yesterday's flight test of the GQM-163A Coyote had several primary objectives, all of which were achieved, including the verification of booster ignition and stable first stage flight, the transition of the ducted-rocket ramjet from booster separation to started inlets, and the ducted rocket ramjet ignition and powered flight performance. In addition, the missile was flown through a series of demanding medium-G vertical and horizontal maneuvers, as well as high-G horizontal weave maneuvers. Finally, the performance of the vehicle's laser altimeter was verified by a descent to a 30-foot cruise altitude and successful completion of the mission through the intentional activation of the flight termination system.

Captain Richard Walter, the U.S. Navy's Program Manager of Aerial Target and Decoy Systems, said, "We are very satisfied with yesterday's flight test results. The capabilities of the GQM-163A Coyote are impressive and will provide a threat representative target for testing of new weapon systems being developed by the Navy. We expect to complete the development phase and award low rate production in early 2005."

Mr. Keven Leith, Orbital's Vice President of Naval Programs, said, "We are pleased with the progress of the GQM-163A flight test program. This latest test flight success represents another step towards making the SSST system ready for operational status and limited fleet deployment in the coming months."

The GQM-163A Coyote target missile design integrates a four-inlet, solid-fuel ducted-rocket ramjet propulsion system into a compact missile airframe 18 feet long and 14 inches in diameter. Ramjet supersonic takeover speed is achieved using a decommissioned Navy MK 70 solid rocket motor for the first stage. Rail-launched from Navy test and training ranges, the highly maneuverable GQM-163A Coyote achieves cruise speeds of Mach 2.5+ following the separation of the MK 70 first-stage booster. The range of the target vehicle system is approximately 50 nautical miles at altitudes of less than 20 feet above the sea surface.

The GQM-163A Coyote program represents a significant milestone for the American aerospace industry by achieving multiple successful flights of a U.S.-built solid-fuel ducted-rocket ramjet. It is also the first successful development and flight test program of a new domestic ramjet missile configuration in over a decade. Orbital is the only U.S. Department of Defense prime contractor to be both developing and operating ramjet-powered missile systems. In addition to developing the GQM-163A Coyote, Orbital provides the Navy with launch services for the MQM-8 VANDAL SSST. The MQM-8 VANDAL is based on the liquid-fuel ramjet-powered Talos missile and provides the Navy with a legacy SSST until the more capable GQM-163A Coyote is determined to be operational for fleet use.

Orbital is developing and manufacturing the GQM-163A Coyote at its launch vehicle engineering and production facility in Chandler, Arizona. Orbital's major subcontractors include Aerojet Corporation in Gainesville, Virginia and Sacramento, California, for the solid-fuel ducted-rocket motor and Cei, Inc. in Sacramento, California, for the vehicle's avionics system.

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.

More information about Orbital can be found at http://www.orbital.com

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

    SOURCE: Orbital Sciences Corporation