DULLES, Va.April 12, 2005--Orbital Sciences Corporation (NYSE:ORB) announced today that it successfully launched a new Medium Range Target (MRT) vehicle for the U.S. Missile Defense Agency (MDA). The mission served as a risk reduction flight demonstration for the new target vehicle and collected critical data for a number of missile defense-related sensors that were activated for the test.

The MRT vehicle is the first of a family of flexible targets being developed for MDA that can be launched conventionally from ground sites, air-launched from a U.S. Air Force C-17 cargo aircraft or sea-launched from the deck of a retired helicopter carrier. The risk reduction flight, which originated approximately 900 miles due west of Kauai, Hawaii, demonstrated the air-launch mode of operation from a C-17 aircraft. The target vehicle flew a ballistic trajectory and impacted the Pacific Ocean northwest of the Kauai Pacific Missile Range Facility (PMRF).

"We are very pleased to have provided another successful target vehicle launch for our immediate customer at the Army's Space and Missile Defense Command and for the Missile Defense Agency," said Mr. Ron Grabe, Executive Vice President and General Manager of Orbital's Launch Systems Group. "The success of this mission was particularly important since it resulted in the delivery of the first flexible ballistic target vehicle that MDA can use for years to come."

Orbital developed the MRT multiple launch mode target vehicle over a two-year period under a contract from the U.S. Army Space and Missile Defense Command (USASMDC). The specifications required a target vehicle that could support a broad range of ballistic trajectories and the integration of flexible hardware and software designs. These flexible configurations will allow MDA to select from a wide variety of mission parameters using a single target design with relatively short lead-time notification before mission execution. The MRT also integrates extensive booster and reentry system instrumentation and sensors to fully characterize the target vehicle's performance and provide post-mission verification data.

The MRT integrates a Castor IVB rocket motor produced by Alliant TechSystems (NYSE:ATK), which Orbital has integrated and launched on several recent and past missions for MDA. Orbital's teammate, Coleman Research Corporation, and their subcontractor Irvin Aerospace, developed and produced the Carriage Extraction System (CES) and parachute systems used to integrate and extract the MRT from the C-17 aircraft and provide descent and release of the target vehicle.

Orbital is one of the country's most experienced developers and operators of missile defense-related launch vehicles. The company supports virtually all of America's major missile defense programs with cost-effective and highly reliable target vehicles. In addition to the Aegis BMD and THAAD, Orbital's target vehicles are used to test MDA's Ground-based Midcourse Defense (GMD) system, the U.S. Army's Patriot PAC-3 and MDA's Critical Measurements and Countermeasures Programs. Orbital also produces the new Coyote sea-skimming supersonic target vehicle for the U.S. Navy's ship self-defense systems.

In addition to target vehicles, Orbital is one of the leading suppliers of missile defense interceptor boosters, with major roles as the primary booster supplier for both the GMD and Kinetic Energy Interceptors (KEI) programs. As part of a Boeing-led team, Orbital is in full production of GMD interceptor boosters now being deployed in Alaska and California, and for use in system testing. In addition, as a member of a Northrop Grumman-led team, Orbital will conduct booster design, development and test activities for MDA's KEI system over the next several years.

About Orbital

Orbital develops and manufactures small space and missile systems for commercial, civil government and military customers. The company's primary products are satellites and launch vehicles, including low-orbit, geostationary and planetary spacecraft for communications, remote sensing and scientific missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense boosters 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
             Beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation