Orbital Sciences Corporation today announced that it is prepared to launch the Space Technology 5 (ST5) scientific spacecraft for the National Aeronautics and Space Administration (NASA) aboard the company’s PegasusĀ® rocket. The launch is now scheduled to take place on Wednesday, March 22, 2006 from Vandenberg Air Force Base (VAFB), California, during an available launch window that extends from 8:57 to 10:20 a.m. (EST). The targeted launch time is 9:02 a.m. (EST). This operational schedule is subject to the completion of final pre-launch activities, as well as acceptable weather conditions at VAFB at the time of the launch.

Orbital and NASA engineers have completed their analysis as to why the Pegasus starboard flight control surface fin locking pin did not retract during the first launch attempt on March 15. The team concluded that while it is possible that ice build-up may have prevented the pin from being extracted, the exact cause could not be determined. As a result, the pin retraction mechanism was removed and replaced in the event there were other contributing causes. Steps have also been taken to mitigate potential water intrusion in this area of the Pegasus that could become ice during high-altitude captive carry of the rocket.

The powered flight sequence for the ST5 mission is expected to take approximately 11 minutes, from the time the Pegasus rocket is released from the L-1011 carrier aircraft to the time that the ST5 satellites are deployed into orbit. Orbital plans to launch the three 55-pound ST5 spacecraft into a highly elliptical orbit of 186 by 2,796 miles above the Earth inclined at 105.6 degrees to the equator.

About Orbital

Orbital develops and manufactures small space systems for commercial, civil government and military customers. The company’s primary products are satellites and launch vehicles, including low-orbit, geostationary-orbit and planetary spacecraft for communications, remote sensing and scientific missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense boosters 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.

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