DULLES, Va.Sept. 9, 2004--

    -- Orbital Veteran and Former U.S. Astronaut to Succeed Richard
            Hicks at Company's Greenbelt, MD-based Unit --

Orbital Sciences Corporation (NYSE:ORB) announced today that Mr. G. David Low has been named Vice President of its Technical Services Division (TSD), headquartered in Greenbelt, MD. Mr. Low will succeed Mr. Richard Hicks, who is remaining with TSD on a part-time basis as an advisor on existing contracts and new business opportunities. Mr. Hicks has held various positions in the aerospace industry over the past 43 years and is entering into partial retirement. Mr. Low assumed his new post on September 7.

"It is with great confidence in David's abilities that we announce his appointment as the new head of our Technical Services Division," said Mr. Jack Danko, Orbital's Executive Vice President and General Manager of its Space Systems Group. "His credentials as a senior Orbital manager and extensive knowledge of and background with NASA, TSD's principal customer, represent a perfect fit for the TSD business."

Mr. Danko also added, "I am also pleased that Dick Hicks has agreed to remain active in the TSD business. Orbital will continue to benefit from the insight and wisdom he gained during his many years in the industry."

Mr. Low has served with Orbital for the past eight years, joining the company's Launch Systems Group in 1996 as Vice President of Safety and Mission Assurance, spearheading the Group's ISO qualification effort. In addition to holding several other senior positions in the company, Mr. Low most recently served as Vice President and Deputy General Manager of Orbital's Advanced Programs Group. In this role, he helped lead the company's participation in NASA's efforts to develop new human space exploration systems.

Prior to joining Orbital, Mr. Low was a NASA astronaut from 1984 until 1996. During this time he flew on three Space Shuttle missions as a mission specialist, flight engineer and payload commander. During his more than 700 hours in space, Mr. Low helped to deploy two communications satellites and retrieve two scientific satellites using the Shuttle's robotic arm. He also conducted a six-hour spacewalk and participated in numerous scientific and medical experiments. Mr. Low began his career with NASA in 1980 as a spacecraft systems engineer for the Jet Propulsion Laboratory.

Mr. Low holds a B.S. in Physics-Engineering from Washington and Lee University, a B.S. in Mechanical Engineering from Cornell University, an M.S. in Aeronautics and Astronautics from Stanford University and an MBA from Johns Hopkins University. He has also completed the Advanced Management Program at Harvard Business School.

Mr. Low is a recipient of the NASA Outstanding Leadership Medal, the NASA Exceptional Service Medal, three NASA Space Flight Medals and an honorary Doctor of Engineering Degree from Rensselaer Polytechnic Institute. He is an Associate Fellow of the AIAA.

Mr. Low resides in Potomac Falls, Virginia with his wife JoAnn and their three children.

About Orbital

Orbital develops and manufactures small space and rocket systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-orbit, geosynchronous and planetary spacecraft for communications, remote sensing, scientific and defense 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 satellite-based transportation management systems for public transit agencies and private vehicle fleet operators.

    Note to editors:

    --  A high-resolution photo of Mr. Low is available on Orbital's
        web site at: http://www.orbital.com/images/high/David_Low.jpg

    --  More information about Orbital can be found on the company's
        web site at: www.orbital.com

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

    SOURCE: Orbital Sciences Corporation