-- New Geosynchronous Orbit Satellite to be the Eighth

            Orbital-Built Spacecraft in Intelsat's Fleet --

DULLES, Va.Aug. 21, 2008--Orbital Sciences Corporation (NYSE:ORB) today announced that it has been selected by Intelsat, Ltd., the world's leading provider of commercial satellite services, to design, build and deliver the Intelsat-18 (IS-18) commercial communications satellite. The satellite will be based on Orbital's flight-proven STAR-2 platform and will generate approximately 4.9 kilowatts of payload power. The IS-18 satellite will carry 24 C-band transponders to cover the Northern and Southern Hemispheres and 12 Ku-band transponders to provide services to the United States, French Polynesia, Australia, New Caledonia and other Pacific Islands. Following its launch and deployment, the spacecraft will be located in geosynchronous orbit (GEO) at 180 degrees East longitude. This latest order for one of Orbital's GEO communications satellites is the 24th to be ordered by customers throughout the world and will be the eighth in the Intelsat fleet. The IS-18 satellite will replace Intelsat's IS-701 spacecraft.

"The order from Intelsat for the IS-18 satellite continues the close collaboration between our two companies, enabling our valued customer to deploy the most efficient fleet of spacecraft possible to deliver high-quality services to their customers," said Mr. Michael Larkin, Orbital's Executive Vice President and General Manager of its Space Systems Group.

"So far this year, a total of three STAR satellites have been purchased by new and existing customers, solidifying Orbital's position as the leading provider of smaller-class GEO commercial satellites in the world," Mr. Larkin added. "In addition to the strong new order activity, our manufacturing and launch preparations are also in high gear. The AMC-21 satellite was recently launched for SES Americom and we are making preparations to ship the NSS-9 satellite to the launch site in the coming weeks for SES New Skies."

The Intelsat-18 spacecraft is the third order to be placed in 2008 for satellites based on Orbital's STAR-2 platform. In April, the company announced that SES Americom had ordered the AMC-1R spacecraft and in May, Orbital announced that it had teamed with Thales Alenia Space for the STAR-2 based Koreasat-6 satellite to be built for KT Corporation of the Republic of Korea.

About Intelsat

Intelsat is the leading provider of fixed satellite services (FSS) worldwide, delivering information and entertainment for many of the world's leading media and network companies, multinational corporations, Internet service providers and governmental agencies. Intelsat's satellite, teleport and fiber infrastructure is unmatched in the industry, setting the standard for advanced transmissions of video, data and voice services. With the globalization of content, broadband, telecom, HD and IPTV fueling next-generation growth, the ever-expanding universe of satellite communications is the cornerstone of today's Intelsat. Real-time, advanced communications with people anywhere in the world is closer, by far.

About Orbital

Orbital develops and manufactures small 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 http://www.orbital.com

    CONTACT: Orbital Sciences Corporation
             Barron Beneski (703) 406-5528
             Public and Investor Relations

    SOURCE: Orbital Sciences Corporation