DULLES, Va.May 1, 2006--Orbital Sciences Corporation (NYSE:ORB) announced today that it successfully launched the second of two medium-range target vehicles that supported the U.S. Missile Defense Agency's (MDA) Critical Measurements and Countermeasures Program, Campaign 2 (CMCM-2). The second launch of Orbital's medium-range target vehicle was carried out on April 28, 2006 from the Kauai Test Facility on the Pacific Missile Range Facility and was conducted under the Targets and Countermeasures program, for which Lockheed Martin is prime contractor.

Orbital's role in the second CMCM-2 launch was identical to that of the first launch, which was successfully conducted earlier this month on April 13. The company supplied the boost vehicle, integrated the payload deployment module and re-entry system built by Sandia National Laboratories, as well as an MDA-provided secondary payload and conducted the launch operations as contracted by Lockheed Martin.

"We are delighted to have successfully executed the second mission of the CMCM-2 campaign in support of the U.S. missile defense effort," said Mr. Ronald D. Wiley, Orbital's Senior Vice President of Suborbital Launch Vehicles. "Both missions provided a great deal of phenomenology and signature data that is critical to MDA's missile defense development activities and also allowed MDA to examine target vehicle performance data that helps improve modeling and simulation capabilities for future target missions."

Orbital is one of the country's most experienced suppliers 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 and Countermeasures Program, Orbital supplies target vehicles for MDA's Ground-based Midcourse Defense System (GMDS), 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

    SOURCE: Orbital Sciences Corporation