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-- 25th Company-Produced Commercial GEO Satellite Is Performing as Expected Early in Its Check-out for a 15-Year Service Life --

-- CHIRP Hosted Payload Sensor to be Activated After Spacecraft Check-Out
Procedures are Complete --

(Dulles, VA 22 September 2011) -- Orbital Sciences Corporation (NYSE: ORB), one of the world's leading space technology companies, today announced that the SES-2 satellite, built by the company for SES of Luxembourg, was successfully launched into orbit aboard an Ariane 5 rocket from the spaceport at Kourou, French Guiana. The mission began on Wednesday, September 21 with the lift-off of the Ariane space launch vehicle at 5:38 p.m. (EDT). The satellite was accurately deployed into a geosynchronous transfer orbit approximately 36 minutes after liftoff.

Mr. Christopher Richmond, Orbital's Senior Vice President and head of its communications satellite business unit, said, "We are pleased with the progress of the mission so far. Arianespace once again provided us with reliable transportation to orbit, accurately delivering SES-2 into its intended transfer orbit. With communications established to Orbital's mission control center, the satellite has been performing as expected early in its check-out. Together with the engineering team from SES, we have begun the process of in-orbit testing that will be carried out over the next several weeks."

The SES-2 satellite is carrying the Commercially Hosted Infrared Payload (CHIRP) sensor for the U.S. Air Force. The CHIRP sensor features a fixed telescope that can view one quarter of the Earth from geosynchronous orbit. The infrared sensor will test the potential of its wide field-of-view capabilities for future overhead persistent infrared missions for the Air Force.

"The CHIRP team is very excited about the successful SES-2 launch and orbit insertion, which begins the process to demonstrate and test new technologies within a rapidly emerging business model of government and commercial cooperation on hosted payloads," said Mr. Brent Armand, Orbital's CHIRP Program Manager. "Orbital is proud to be at the forefront of offering government and international customers affordable, reliable and short-cycle solutions for their space mission needs."

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Orbital-built SES-2 Communications Satellite with CHIRP Hosted Payload Successfully Launched - Page 2

CHIRP will remain powered off until the spacecraft operations team completes the post-launch testing and orbit raising maneuvers to place SES-2 in its intended geosynchronous Earth orbit (GEO). In approximately 30 days, CHIRP operations will begin with deployment and testing of the sensor electronics, electronics and optical systems.

An innovative three-way industry partnership was responsible for developing, integrating and testing the CHIRP sensor for the U.S. Air Force. SES acted as the prime contractor for the hosted payload project; Science Applications International Corporation (NYSE: SAI) developed and built the CHIRP sensor; and Orbital was responsible for the overall system design, integration and test processes as well as the designer and integrator of the hosted payload interface that will be utilized for future hosted payloads aboard Orbital's commercial satellites.

About the SES-2 Satellite

The SES-2 satellite is based on Orbital's GEOStar 2.4 bus, the company's largest and most powerful commercial communications satellite. The satellite carries 24 active C-band and 24 Ku-band transponders of 36 MHz capacity. Six of the channels in each band can be cross-strapped to the opposite band, enabling new service capability. The SES-2 satellite will generate approximately 5.0 kilowatts of payload power and will have two 2.3 meter deployable reflectors. Following its in-orbit check-out, SES-2 will be positioned at 87 degrees west longitude to provide services to North America.

About SES

SES (Euronext Paris and Luxembourg Stock Exchange: SESG) wholly owns the market-leading satellite operators SES ASTRA and SES WORLD SKIES and participation in Ciel in Canada and QuetzSat in Mexico, as well as a strategic participation in satellite infrastructure start-up O3b Networks. SES provides outstanding satellite communications solutions via a global fleet of 47 satellites. For further information:

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Orbital-built SES-2 Communications Satellite with CHIRP Hosted Payload Successfully Launched - Page 3

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 exploration 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 U.S. Government agencies and laboratories. More information about Orbital can be found at

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Note to Editors: High resolution images of the SES-2 satellite with the CHIRP payload are available on Orbital's web site at: