— Latest Mission Is 25th Consecutive Successful Launch for Pegasus —

(Dulles, VA 16 April 2008) — Orbital Sciences Corporation (NYSE: ORB) announced today that its Pegasus(R) space launch vehicle successfully launched the U.S. Air Force’s Communications/Navigation Outage Forecasting System (C/NOFS) satellite into its intended low-Earth orbit. The mission was the 25th consecutive successful mission for the Pegasus program since 1997 and the 39th overall flight of the company’s air-launched system since its introduction in 1990.

“Pegasus continues to prove that it is the most reliable and versatile small launcher in the world today, with another successful mission supporting an important Air Force program,” said Mr. Ron Grabe, Orbital’s Executive Vice President and General Manager of its Launch Systems Group. “Orbital-developed launch vehicles continue to demonstrate their value to our customers in the military, civil government and commercial markets with highly reliable and available launch services at reasonable prices.”

The Pegasus/C/NOFS mission took place earlier today, originating from the Reagan Test Site, Kwajalein, Marshall Islands in the mid-Pacific Ocean. Following a one-hour long preplanned positioning flight, the Pegasus rocket was released from Orbital’s L-1011 carrier aircraft at approximately 1:00 p.m. (EDT). The C/NOFS satellite, which weighed approximately 870 lbs. (395 kg.) at launch, was accurately deployed into its targeted elliptical orbit of 205 x 385 nautical miles (400 x 850 km.) after an 8-minute powered flight sequence. Due to its launch from the near-equatorial Reagan Test Site, the satellite’s orbit is at a low inclination of 13 degrees to the equator.

The C/NOFS satellite is a joint project of the U.S. Air Force’s Space and Missile Center’s Space Development and Test Wing and the Air Force Research Laboratory Space Vehicles Directorate, both of which are based at Kirtland Air Force Base in Albuquerque, NM. General Dynamics designed and built the satellite and Orbital provided the launch services.

About Pegasus

Pegasus is the world’s leading launch system for the deployment of small satellites into low-Earth orbit. Its patented air-launch system, in which the rocket is launched from beneath Orbital’s “Stargazer” L-1011 carrier aircraft over the ocean, increases performance, reduces cost and provides customers with unparalleled flexibility to operate from virtually anywhere on Earth with minimal ground support requirements.

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 offers space-related technical services to government agencies and develops and builds software-based transportation management systems for public transit agencies and private vehicle fleet operators.

More information about Orbital can be found at http://www.orbital.com