DULLES, Va., Feb 1, 2005 (BUSINESS WIRE) -- Satellite Designed for Launch Aboard Pegasus Rocket Into 150,000-Mile-Apogee Orbit; Combined Value for Satellite and Launch Vehicle of Approximately $60 Million

Orbital Sciences Corporation (NYSE:ORB) announced today that the National Aeronautics and Space Administration (NASA) has selected the company's Interstellar Boundary Explorer (IBEX) satellite to carry out the next mission in its Small Explorer (SMEX) series of scientific spacecraft. Orbital is a key member of the IBEX mission team, which is led by Principal Investigator Dr. David McComas of the Southwest Research Institute in San Antonio, Texas. The IBEX satellite is based on Orbital's MicroStar spacecraft design, a lightweight, multi-role platform of which dozens are already in orbit performing communications and remote sensing missions.

The IBEX spacecraft is designed for launch on Orbital's Pegasus(R) rocket, which is procured by NASA's Kennedy Space Center under a separate contract. A solid rocket motor, provided by Alliant Techsystems (NYSE:ATK), is used to boost IBEX into its highly elliptical Earth orbit, with an apogee of approximately 150,000 miles (or nearly two-thirds of the distance to the Moon). Together, the satellite and launch vehicle contracts have an estimated combined value of approximately $60 million. The IBEX mission is scheduled for launch in 2008 and will be designed for an in-orbit duration of at least two years.

"Our team is delighted to be working with Orbital on IBEX," said Dr. McComas. "The combination of their small satellite capabilities and Pegasus launch vehicle makes them a unique partner for this exciting new mission."

Commenting for Orbital, Mr. Howard Runge, who will serve as Orbital's IBEX Spacecraft Manager, said, "We are thrilled with NASA's selection of the IBEX mission for the Small Explorer program. We congratulate Dr. McComas and his team at the Southwest Research Institute for their outstanding work developing the IBEX mission concept and leading the winning proposal effort. We look forward to working with the IBEX team and NASA to successfully perform this mission."

The Interstellar Boundary Explorer is a remarkable mission of exploration and discovery that provides the first global images of the boundaries between our solar system and the interstellar medium that fills our galaxy. This investigation fills in the critical missing piece of understanding in the connection of our Sun and solar system to the galaxy, fulfilling requirements from recent NASA and National Research Council plans and making fascinating connections to even more distant astrophysical phenomena. IBEX also addresses a serious challenge facing human deep-space exploration by studying the region that shields out the vast majority of galactic cosmic ray radiation. As a result, IBEX is an important early step beyond the solar system and into the galactic frontier.

Orbital has supported NASA's SMEX program for many years with reliable launch services and spacecraft. Recent SMEX missions on which Orbital has played a key role include the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), launched aboard Pegasus in February 2002, and the Galaxy Evolution Explorer (GALEX), built by Orbital and launched aboard Pegasus in April 2003. Orbital is also building and launching the next SMEX mission, the Aeronomy of Ice in the Mesosphere (AIM) satellite, scheduled for a September 2006 launch aboard Pegasus.

About Orbital

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

More information about IBEX can be found at: http://www.ibex.swri.edu/

SOURCE: Orbital Sciences Corporation

Orbital Sciences Corporation
Barron Beneski, 703-406-5528