-- Both Satellites Performing As Expected Early In Their Missions
                                  --

    -- Spacecraft Begin Several Weeks of In-Orbit Testing Prior to
                 Commencement of Commercial Service --

DULLES, Va.Oct. 8, 2007--Orbital Sciences Corporation (NYSE:ORB), the world leader in smaller-sized geosynchronous (GEO) communications satellites, announced today that two of its satellites were successfully launched into orbit during a mission that took place on Friday, October 5. The two satellites, Intelsat-11 (IS-11) and Optus D2, were delivered into their initial orbit by an Ariane 5 rocket launched from the European space launch complex located near the Equator in French Guiana. Results from early tests of the spacecraft conducted over the weekend indicate that both satellites are operating as planned for this phase of their missions. Friday's launch marked the first time that two of Orbital's GEO satellites were launched aboard the same rocket, an indication of the company's growing presence in the GEO satellite market.

"We are very pleased with the early results from the mission, including the picture-perfect flight aboard the Ariane launch vehicle and the state of health of both satellites early in their missions," stated Mr. Carl Marchetto, Executive Vice President and General Manager of Orbital's Space Systems Group.

During the next several days, both the IS-11 and Optus D2 spacecraft will perform a series of orbit-raising burns using their onboard rocket engines to achieve a circular orbit approximately 22,300 miles (35,800 kilometers) above the Earth. For several weeks afterwards, each of the mission engineering teams will conduct a comprehensive series of tests to ensure the spacecraft is ready for final hand-over to the customer.

About Intelsat-11

The IS-11 satellite was built for Intelsat, Ltd. of Bermuda. Following its launch and check-out, IS-11 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
             Barron Beneski, 703-406-5528
             Public and Investor Relations
             beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation