-- Company Has Repurchased Approximately $108 Million of Its

                Common Stock In the Last Three Years --

DULLES, Va.May 2, 2007--Orbital Sciences Corporation (NYSE:ORB) today announced that its Board of Directors has authorized the company to repurchase up to $50 million of its common stock over the next 12 months. The Board's authorization replaces a previous 12-month, $50 million securities repurchase program that expired in April. Since mid-2004, when Orbital's buyback plan was initiated, the company has repurchased approximately $108 million, or 7.5 million shares, of its common stock.

"The common stock buyback authorization by our Board will allow us to continue to repurchase the company's common stock on an opportunistic basis, providing us with another avenue to build value for our shareholders," said Mr. David W. Thompson, Chairman and Chief Executive Officer. "Orbital's healthy cash balances and continued strong free cash flow outlook provide us with the flexibility to further enhance the company's already solid capital structure."

Under the newly authorized repurchase program, shares of common stock may be purchased from time to time in the open market, in block purchase or in negotiated transactions. The timing and amount of shares to be repurchased will be determined based on market conditions and other factors.

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, geosynchronous-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


    CONTACT: Orbital Sciences Corporation
             Public and Investor Relations:
             Barron Beneski, 703-406-5528
             Beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation