Company Expects to Conduct 8 Launches Carrying 20 Tons of Cargo Over 2011-2015 Period

NASA to be Anchor Customer for Company's Taurus II Medium-Class Space Launch Vehicle

DULLES, Va.Dec. 23, 2008--Orbital Sciences Corporation (NYSE:ORB), one of the world's leading space technology companies, today announced that it has been selected for a long-term contract by the National Aeronautics and Space Administration (NASA) to provide cargo transportation services to and from the International Space Station (ISS). Orbital stated that the contract, awarded under NASA's Commercial Resupply Services (CRS) program, has an expected value of approximately $1.9 billion for cargo transportation missions to be conducted between 2011 and 2015. This contract amount covers ISS cargo transportation services for about 20 metric tons of cargo, which would be accommodated by 8 missions of Orbital's CRS system. The operational missions would follow Orbital's flight demonstration of its CRS system in late 2010 under the Commercial Orbital Transportation Services (COTS) program, which Orbital and the space agency initiated in early 2008.

"We are very appreciative of the trust NASA has placed with us to provide commercial cargo transportation services to and from the International Space Station, beginning with our demonstration flight scheduled in late 2010," said Mr. David W. Thompson, Orbital's Chairman and Chief Executive Officer. "The CRS program will serve as a showcase for the types of commercial services U.S. space companies can offer NASA, allowing the space agency to devote a greater proportion of its resources for the challenges of human spaceflight, deep space exploration and scientific investigations of our planet and the universe in which we live."

To carry out the cargo services missions, Orbital will use the integrated system it is currently developing under the COTS cooperative research and development program with NASA. The company's COTS system is based on Orbital's new Cygnus(TM) maneuvering space vehicle and will be the anchor customer for the new Taurus IITM medium-lift launch vehicle, now under development. Cygnus is made up of a service module, containing the vehicle's propulsion, power systems and avionics, and one of three types of specialized cargo modules. Orbital's design accommodates pressurized, unpressurized and return cargo modules, offering NASA flexibility in its cargo planning.

"CRS represents a dramatic departure from NASA's traditional contracting practices that will be greatly beneficial to both the space agency and the nation's industrial base," said Dr. Antonio L. Elias, Executive Vice President and General Manager of Orbital's Advanced Programs Group, which oversees both the COTS and CRS projects.

Leading up to the first flight of Orbital's system, the company has begun preparations for its CRS-related production and testing activities over the next 18 months at its Dulles, Virginia headquarters and space vehicle engineering center; its Chandler, Arizona launch vehicle operations; and its Wallops Island, Virginia payload processing facility and launch base. Orbital recently determined that it would conduct the testing of the first stage engines of the Taurus II rocket at NASA's Stennis Space Center facility in Mississippi. The company has also begun its on-site preparations for the launch site infrastructure at the Mid-Atlantic Regional Spaceport located at Wallops Island that will support Taurus II launches.

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 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 government agencies and laboratories.

More information about Orbital can be found at

    CONTACT: Orbital Sciences Corporation
             Barron Beneski
             Public and Investor Relations

    Source: Orbital Sciences Corporation