DULLES, Va.April 17, 2006--Orbital Sciences Corporation (NYSE:ORB) announced today that it successfully launched a two-stage medium-range target vehicle that supported the U.S. Missile Defense Agency's (MDA) Critical Measurements/Countermeasures Program, Campaign 2 (CMCM-2). The launch of Orbital's target vehicle, which was based on two SR-19 rocket motors, originated from the Pacific Missile Range Facility on April 13, 2006. Orbital's role in the test was to supply the boost vehicle, integrate the Massachusetts Institute of Technologies/Lincoln Laboratories payload deployment module and re-entry system, integrate an MDA-provided secondary payload and conduct launch operations as contracted by Lockheed Martin Space Systems.

"It is with great pride that Orbital successfully launched another signature target mission for the U.S. missile defense effort," said Mr. Ronald D. Wiley, Orbital's Senior Vice President of Suborbital Launch Vehicles. "This complex mission provided important phenomenology and data collection opportunities for U.S. missile defense systems."

This was the second mission that Orbital has conducted as a subcontractor to Lockheed Martin, the prime contractor for MDA's Targets and Countermeasures Program. The previous mission conducted under this arrangement was the successful launch of a Medium Range Target (MRT-1) for the U.S. Navy's Aegis BMD system in November 2005. Mr. Wiley added, "We appreciate the opportunity to work with Lockheed Martin's mission management and engineering team to achieve another mission success for our customer."

Orbital is one of the country's most experienced builders and operators of suborbital boosters and anti-ship cruise missile targets that are used to test defensive weapons systems. In addition to the Critical Measurements/Countermeasures Program, Orbital supplies target vehicles for MDA's Ground-based Midcourse Defense (GMD) System, U.S. Navy's Aegis Ballistic Missile Defense System, and the U.S. Army's Patriot (PAC-3) and Theater High Altitude Area Defense (THAAD) Systems.

About Orbital

Orbital develops and manufactures small space systems for commercial, civil government and military customers. The company's primary products are satellites and launch vehicles, including low-orbit, geostationary-orbit 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
             Public and Investor Relations
             Barron Beneski, 703-406-5528
             Beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation