DULLES, Va.Dec. 7, 2006--Orbital Sciences Corporation (NYSE:ORB) announced today that it has commenced an offering of $125 million aggregate principal amount of convertible senior subordinated notes due 2027, plus an additional $18.75 million aggregate principal amount of notes that may be issued, at the option of the initial purchasers, to cover over-allotments within 30 days of the initial issuance of the notes.

Orbital intends to use the net proceeds from the sale of the notes, together with cash on hand, to repurchase its outstanding 9% Senior Notes due 2011 and to repurchase concurrently with this offering up to $50 million of outstanding shares of its common stock.

The notes will be sold to qualified institutional buyers in accordance with Rule 144A under the Securities Act of 1933, as amended. The notes and Orbital common shares issuable upon conversion of the notes have not been registered under the Securities Act of 1933, or any state securities laws, and unless so registered, may not be offered or sold in the United States except pursuant to an exemption from the registration requirements of the Securities Act of 1933 and applicable state laws.

This release shall not constitute an offer to sell or the solicitation of an offer to buy any of these securities, nor shall it constitute an offer, solicitation or sale in any jurisdiction in which such offer, solicitation or sale is unlawful.

About Orbital

Orbital develops and manufactures small rockets and space systems for commercial, military and civil government customers. Orbital's primary products are satellites and launch vehicles, including low-orbit, geosynchronous-orbit 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.

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

Safe Harbor Statement

Certain statements in this press release may be forward-looking in nature or "forward-looking statements" as defined in the Private Securities Litigation Reform Act of 1995. Such forward-looking statements are subject to risks, trends and uncertainties that could cause the actual results or performance of the company to be materially different from the forward-looking statement. Uncertainty surrounding factors such as continued government support and funding for key space and defense programs, product performance and market acceptance of products and technologies, the outcome of the government investigation, as well as other risk factors and business considerations described in the company's SEC filings, including its annual report on Form 10-K/A, could impact Orbital's actual financial and operational results. Orbital assumes no obligation for updating the information contained in this press release.


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

    SOURCE: Orbital Sciences Corporation