DULLES, Va., July 12 /PRNewswire/ -- Orbital Sciences Corporation (NYSE: ORB) announced today that its MacDonald, Dettwiler and Associates Ltd. (MDA) subsidiary completed its initial public stock offering when its shares began trading on the Toronto Stock Exchange this morning under the trading symbol "MDA." Today's IPO of the Richmond, British Columbia-based information systems and space technology company raised approximately $57 million (U.S.) through the sale of 6.0 million shares of common stock priced at approximately $9.50 per share (U.S.). Of the 6.0 million shares, MDA sold 4.0 million primary shares, which raised $38 million for the subsidiary, while Orbital sold 1.5 million shares, which raised approximately $14 million for the company. Other private investors sold another 500,000 secondary shares. In addition, the underwriters have an option to purchase up to 600,000 additional shares, of which 500,000 would be sold by Orbital and the other 100,000 by MDA's pre-IPO private investors.

MDA has previously stated that the primary proceeds of the IPO will be used to invest in and expand MDA's e-commerce business in online land information services, as well as for other general corporate purposes. A syndicate of underwriters led by RBC Dominion Securities Inc. underwrote the offering.

Mr. David W. Thompson, Orbital's Chairman and Chief Executive Officer, said, "The successful completion of MDA's IPO represents a major step in Orbital's campaign to unlock value for our shareholders and our plan to fund MDA's continued rapid growth. We are very pleased to be able to realize such an outstanding return on the original investment we made in MDA in 1995."

Mr. Thompson added, "We believe that MDA's IPO, which has placed a market- based valuation on our majority holdings, should help highlight the intrinsic value of Orbital's businesses, which we strongly believe is not reflected in our current stock price."

The MDA shares were not registered in the U.S. and are not traded on any U.S. stock exchange.

MDA, which was acquired by Orbital in 1995, provides end-to-end spatial information systems, advanced space robotics technologies and online land information services. It develops, builds and upgrades imaging satellite ground stations and designs, manufactures and supports space robotics used on the NASA Space Shuttle and International Space Station. In addition, MDA offers electronic access to legal, asset and geographic information for property transactions in the U.S. and Canada.

Orbital is one of the largest space technology and satellite services companies in the world, with 1999 total enterprise revenues (including revenues from unconsolidated affiliates) of approximately $915 million. The company, headquartered in Dulles, Virginia, employs about 5,500 people at major facilities in the U.S., Canada and several overseas locations. Orbital is the world's leading manufacturer of low-cost space systems, including satellites and space robotics, launch vehicles, electronics and sensors, satellite ground systems and related digital infrastructure. Its Magellan subsidiary is a pioneer in satellite-based navigation and communications products for consumer and industrial markets. Through its ORBCOMM and ORBIMAGE affiliates and ORBNAV subsidiary, Orbital is also a major operator of satellite-based networks that provide data communications, high-resolution imagery and automotive information services to customers around the world. SOURCE Orbital Sciences Corporation

/ NOTE TO EDITORS: To learn more about Orbital, as well as to access its recent press releases, please visit its web site at http://www.orbital.com/

CONTACT: Barron Beneski of Orbital Sciences Corporation, 703-406-5000, or email: beneski.barron@orbital.com/