-- Launch Aboard Ariane Rocket Marks the First Time Two

Orbital-Built GEO Satellites Are Manifested on Same Launch Vehicle --

DULLES, Va.Oct. 4, 2007--Orbital Sciences Corporation (NYSE:ORB), the world leader in smaller-sized commercial geosynchronous (GEO) communications satellites, is in final preparations for the launch of two of its spacecraft from the European space launch complex in French Guiana. The two satellites are the Intelsat-11 (IS-11) spacecraft for Intelsat, Ltd. of Bermuda and the Optus D2 satellite for Optus Networks, Pty of Australia. The mission is currently scheduled for Friday, October 5, with the launch to take place within an available window that extends from 5:28 p.m. to 6:13 p.m. (EDT).

In another sign of Orbital's rapidly growing GEO satellite business, two of Orbital's Star(TM) satellites will be launched aboard the same rocket for the first time. In previous launches aboard Ariane rockets, Orbital's smaller-sized satellites have been co-manifested with another larger satellite from a different manufacturer. Thus far in 2007, Orbital has been awarded five firm and four optional orders for its GEO satellites, making it the most productive year in the company's history for commercial communications satellites.

"Our team is very excited to be in the final phase of preparing the IS-11 and Optus D2 spacecraft for their launch and deployment, which will be followed by several weeks of in-orbit check-out before they are maneuvered into their operational slots 22,300 miles above the Earth," said Senior Vice President Christopher Richmond, head of Orbital's GEO communications satellite programs. "Both Intelsat and Optus are very important and valued customers of Orbital and we are committed to extending our history of carrying out successful missions for them."

About Intelsat-11

Following its launch and check-out, the IS-11 spacecraft will join several other Orbital-built satellites in Intelsat's in-orbit fleet, including Galaxy 12, 14 and 15. The IS-11 spacecraft is a hybrid satellite that will provide both C-band and Ku-band services. It will deliver C-band services to Intelsat's customers in the continental United States and will also serve as DirecTV Latin America's Ku-band downlink for coverage of Brazil. In addition to IS-11, Intelsat has three other Orbital GEO spacecraft on order, including Horizons-2 (for a joint venture between Intelsat and JSAT of Japan), and Intelsat-15 and Intelsat-16.

About Optus D2

Built for Australia-based Optus Networks, Pty., Optus D2 is the second in a series of satellites that will provide Ku-band fixed communications and direct television broadcasting services to Australia and New Zealand. The Optus D2 is among the most powerful GEO communications satellites ever built by Orbital, designed to generate 5 Kw of electrical power. Optus D2 will carry 24 active Ku-band transponders on a platform that is ideal for telephony, data and broadcasting applications. Earlier this year, Optus ordered its third satellite from Orbital for the D-series of spacecraft. Orbital is scheduled to deliver the Optus D3 satellite in 2009.

Orbital's commercial satellite business has experienced rapid growth over the past several years. Including the five new orders the company has booked so far this year, Orbital currently has 10 commercial GEO satellites and five science and defense spacecraft in various stages of design, production and testing at its Dulles, VA satellite manufacturing facility. To accommodate this rapid rate of growth, earlier this year Orbital completed an expansion of its manufacturing plant that, together with other facility improvements, has increased its manufacturing throughput capacity by over 30% as compared to one year ago.

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-orbit, geosynchronous-orbit and planetary spacecraft for communications, remote sensing, scientific and defense 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 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.

Note to Editor: High-resolution images of the Intelsat-11 and Optus D2 satellites are available on Orbital's web site at: http://www.orbital.com/NewsInfo/Images/GEO/index.html


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

    SOURCE: Orbital Sciences Corporation