-- Ninth Consecutive Successful MRT Mission Supports Japanese Aegis BMD Test --

-- Orbital Continues to Support U.S. Missile Defense Agency with Highly-Reliable
Target Vehicle Launches --

(Dulles, VA 29 October 2010) - Orbital Sciences Corporation (NYSE: ORB) announced today that it successfully launched a Medium Range Target (MRT) vehicle under a direct contract from the U.S. Missile Defense Agency (MDA). The MRT vehicle served as an intercept target for the Japanese Navy's Aegis Ballistic Missile Defense (BMD) system. It was launched yesterday, October 28, 2010, from the Pacific Missile Range Facility on Kauai, Hawaii and flew on a northwestern trajectory. The MRT vehicle was successfully intercepted by the Japanese Navy's Standard Missile-3 (SM-3) interceptor system before it reentered the Earth's atmosphere. Yesterday's launch was the ninth overall mission for Orbital's MRT program, all of which have been successful. Of the nine missions, seven were launched in support of the Aegis BMD test program, including four for the Japanese test program.

"We are very pleased to support the Missile Defense Agency and Japanese Aegis BMD program with another successful target launch, including a positive hit indication from the Orbital-developed Test Object. This is the second successful mission for the Orbital Test Object and ninth successful MRT flight overall," said Mr. Ron Wiley, Senior Vice President of Suborbital Targets Programs. "We look forward to continued success with future MRT missions supporting MDA and Aegis BMD engagements."

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). It was developed to meet demanding specifications that require launch capability from air-, ground- or sea-based platforms. Its first flight occurred in April 2005 and demonstrated the air-launch mission capability. For that mission, the target vehicle was extracted and descended from a C-17 cargo aircraft via a parachute system, an operational methodology necessary to support U.S. Army Theater High Altitude Area Defense (THAAD) tests. The air-launch demonstration was then followed by four consecutive ground-launch missions for Aegis BMD tests, an air-launch mission in June 2008 for THAAD, followed by three more ground-launch missions for Aegis BMD. A launch from a sea-based platform has not yet been ordered by the customer.

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Orbital Successfully Launches Medium Range Target for Joint U.S./Japan
Missile Defense Test - Page 2

Orbital is one of the country's most experienced developers and operators of missile defense-related target 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 Aegis BMD, Orbital's target vehicles are used to test MDA's Ground-based Midcourse Defense (GMD) system, as well as the U.S. Army's Patriot PAC-3 and THAAD systems. Orbital also produces the "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- and medium-class rockets and space systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-Earth orbit, geosynchronous-Earth orbit and planetary exploration spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other 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 provides satellite subsystems and space-related technical services to U.S. Government agencies and laboratories.

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

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