-- Third Orbital-Built Spacecraft Launched for Australian Satellite Operator --

DULLES, Va.Aug. 24, 2009-- Orbital Sciences Corporation (NYSE: ORB) announced today that the Optus D3 commercial communications satellite, built by Orbital for Optus Networks Pty Limited of Australia, was successfully launched into its targeted orbit aboard an Ariane 5 rocket on Friday, August 21, 2009. The mission originated from the spaceport at Kourou, French Guiana at approximately 6:10 p.m. (EDT). The Optus D3 satellite was deployed into a geostationary transfer orbit about 32 minutes after lift-off. Initial communications with the satellite have been established and it is performing as expected in the early stages of the mission.

“We are very pleased with the early results of the Optus D3 mission following its launch into orbit on Friday,” stated Chris Richmond, Senior Vice President for Orbital’s commercial satellite programs. “The satellite is operating as expected at this early stage of its in-orbit testing process. We anticipate turning over operational control of the D3 spacecraft to Optus in the coming weeks after all testing is complete. With three Orbital-built satellites in its fleet, Optus continues to be one of our most valued customers and we look forward to continuing the excellent relationship for many years to come.”

Once in service, the Optus D3 spacecraft will further expand Optus’ market coverage with its co-location at 156 degrees East longitude with the Optus C1 satellite. Optus D3 is the largest GEO communications satellite that Orbital has built to date, with total payload power of approximately 5.0 KW, a launch mass of 2,500 kg (5,510 lbs) and a total of 32 transponders.

During the next several days, the Optus D3 spacecraft will perform a series of orbit-raising burns of its onboard rocket engine to achieve a circular orbit 22,300 miles (35,800 kilometers) above the Earth. For several weeks afterwards, the mission’s engineering team will conduct comprehensive tests to ensure the spacecraft is ready for final hand-over to Optus.

Orbital’s highly successful communications satellites are based on the company’s STAR spacecraft platform, which is able to accommodate all types of commercial communications payloads and is compatible will all major commercial launchers. The company’s STAR product line includes the STAR 2.4 design, which is optimized for smaller satellite missions, generating up to 5.0 KW of payload power. Orbital has also developed the higher-power STAR 2.7 spacecraft design, delivering the next increment of payload power to between 5.0 and 7.0 KW, allowing Orbital to offer its innovative and reliable satellite design to the medium-class of communications satellites.

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 http://www.orbital.com

Note to Editors: A high-resolution image of the Optus D3 satellite is available on Orbital’s web site at: http://www.orbital.com/NewsInfo/Images/GEO

Source: Orbital Sciences Corporation

Orbital Sciences Corporation
Barron Beneski (703) 406-5528
Public and Investor Relations
Beneski.barron@orbital.com