DULLES, Va.Nov. 18, 2005--Orbital Sciences Corporation (NYSE:ORB) announced today that it successfully launched a medium-range target (MRT-1) vehicle under the Lockheed Martin Targets and Countermeasures Prime Contract with the U.S. Missile Defense Agency (MDA). The MRT-1 vehicle served as an intercept target for the Navy's Aegis Ballistic Missile Defense (BMD) System and was launched yesterday from the Pacific Missile Range Facility (PMRF) on Kauai, Hawaii. MRT-1 flew a trajectory northwest of Kauai and was intercepted by the Navy's Standard Missile (SM-3) interceptor system before reentering the Earth's atmosphere. The MRT-1 was the first of several medium-range targets Orbital is prepared to launch under contract to Lockheed Martin in support of the Aegis BMD test program. The MRT target is also part of Lockheed Martin's Flexible Target Family (FTF), currently under development for responsive and cost-effective missile defense system testing.

"We are very pleased to provide a successful target launch and presentation for our immediate Lockheed Martin customer, and the Missile Defense Agency's (MDA) Aegis BMD program," said Mr. Ron Grabe, Executive Vice President and General Manager of Orbital's Launch Systems Group. "This target launch and intercept mission has been several years in the making and we're excited to have played a key role in achieving such an important testing milestone. We also appreciate the opportunity for Lockheed Martin and Orbital mission management and engineering teams to work together to ensure mission success, as an integrated team throughout target vehicle integration and launch operations."

Orbital originally developed the MRT multiple-launch-mode target vehicle over a two-year period under contract to the U.S. Army Space and Missile Defense Command (USASMDC), according to specifications that require launch capability from ground, air, or sea, a broad range of ballistic trajectories and integration of flexible hardware and software designs. These flexible designs allow customers to select from a wide variety of mission parameters in a single target design, just a short period of time before mission execution.

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

About Orbital

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