-- $43 Million Sale of Company's Non-Core Unit Completes Orbital's
   Strategic Refocusing on Its Satellite Systems and Launch Vehicle
                             Businesses --

DULLES, Va.June 2, 2008--Orbital Sciences Corporation (NYSE:ORB) announced today that it has completed the sale of its non-core Transportation Management Systems (TMS) unit to Affiliated Computer Systems (ACS) (NYSE:ACS). As announced earlier this year, the sale price in the all-cash transaction was approximately $43 million.

Mr. David W. Thompson, Orbital's Chairman and CEO said, "We would like to thank all the TMS employees whose efforts contributed to the success of the business. We believe the TMS group has a very bright future as part of the ACS team, which is strongly focused on providing innovative technology to the transportation industry."

TMS is a leading integrator of software-based systems that combine satellite navigation and wireless communications to enable municipal transit and other fleet operators to better manage and dispatch public transit and highway service vehicles and commuter light rail systems. TMS offers its products and services to the global Intelligent Transportations Systems market, including its state-of-the-art Computer Aided Dispatch and Automatic Vehicle Location systems. TMS currently serves approximately 60 state, regional and local transit agency customers in the U.S. and abroad and has units installed or scheduled to be installed on over 27,500 vehicles in those markets.

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 provides satellite subsystems and space-related technical services to government agencies and laboratories.

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

    CONTACT: Orbital Sciences Corporation
             Barron Beneski, 703-406-5528
             Public and Investor Relations

    SOURCE: Orbital Sciences Corporation