ST5 Mission was 37th Launch in the Pegasus Program's 16-Year History and 23rd Consecutive Successful Flight Since 1997

Orbital Sciences Corporation announced today that its Pegasus® space launch vehicle successfully launched three small scientific spacecraft for the National Aeronautics and Space Administration's (NASA's) Space Technology 5 program (ST5). In a mission that took place earlier today from Vandenberg Air Force Base, California, the three 55-pound ST5 spacecraft were accurately delivered into their targeted elliptical orbits approximately 300 by 4,570 kilometers above the Earth at an inclination of 105.6 degrees to the equator. Preliminary data from the satellites indicate that all three NASA-built spacecraft are operating as expected early in their mission.

The powered flight sequence for the ST5 mission took approximately 10 minutes, from the time the Pegasus rocket was released from its L-1011 carrier aircraft at 9:04 a.m. (EST) to the time that the first of the three satellites were deployed into orbit. The remaining two ST5 satellites were then deployed at three-minute intervals. Today's mission was the 37th launch of the Pegasus rocket and its 23rd consecutive successful mission.

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, reduces cost and provides customers with unparalleled flexibility to operate from virtually anywhere on Earth with minimal ground support requirements.

For the ST5 mission, Orbital employed a unique satellite deployment system called the Pegasus Support Structure, which is a spring-loaded mechanism that intentionally spins the satellites at preset time intervals in order to create a formation-flying group of spacecraft in low-Earth orbit.

The ST5 mission was the first flight of the Pegasus rocket in 2006. Later this year, Orbital is scheduled to launch NASA's Aeronomy of Ice in the Mesosphere (AIM) spacecraft, which is now in production at Orbital's Dulles, Virginia satellite manufacturing facility.

About ST5

NASA's New Millennium Program's ST5 spacecraft consists of three microsats that are designed to validate, in actual flight conditions, innovative technology concepts that may reduce risks to future science missions. The ST5 mission will demonstrate the ability of small satellites to perform research-quality science by taking measurements of the Earth's magnetic field using highly sensitive magnetometers.

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

Note to Editors:

High-resolution photos of the Pegasus rocket are available on Orbital's website at:

http://www.orbital.com/NewsInfo/Images/index.html