DULLES, Va.Dec. 17, 2003--Orbital Sciences Corporation (NYSE:ORB) announced today that it has signed a major new contract in its geosynchronous (GEO) communications satellite manufacturing business. Optus Networks, Pty., based in Sydney, Australia, has placed a firm order for two spacecraft that will provide Ku-band fixed communications and direct television broadcasting services to Australia and New Zealand. The two new satellites, which will initiate Optus' D-series of satellites, will be based on Orbital's Star(TM) platform and will carry 24 transponders, with 8 back-up channels also available. The first satellite, known as D-1, will generate approximately 4.0 kilowatts of electrical power and is scheduled for delivery in the fourth quarter of 2005. The second satellite, D-2, will generate approximately 4.7 kilowatts of power and is scheduled for delivery in the fourth quarter of 2006. Financial details of the contract were not released.

Commenting on the contract award, Dr. Ali Atia, head of Orbital's GEO communications satellite unit, said, "We are very appreciative of Optus' decision to deploy our Star satellites into their fleet. We are fully committed to working in partnership with Optus to see that the satellites are delivered on schedule for a smooth transition into their network."

Dr. Atia added, "This contract is further evidence of Orbital's increasing dominance in the niche market for small GEO satellites. With an advanced satellite design based on three-axis stabilization and significant power and mass margins over our nearest small platform competitor, we have clearly become the preferred supplier of satellites in this class."

The order from Optus continues Orbital's growth in the market for small GEO communications satellites. Since the late 1990's, Orbital has received orders for 14 small GEO satellites, seven of which have been delivered to customers in the U.S. and Asia. Including this most recent order, Orbital currently has five GEO satellites in various stages of design, manufacturing and testing, and has options for two additional satellites that could be exercised in the future.

Mr. Paul O'Sullivan, Chief Operating Officer of Optus, said, "The deal with Orbital is very significant as it confirms Optus' position as a leading satellite operator in the Asia Pacific region. It secures our leadership position in the direct-to-home subscription television broadcasting markets of Australia and New Zealand. We are looking forward to a successful relationship with Orbital."

Orbital's highly successful GEO communications satellites are based on the company's Star-1 and Star-2 standard spacecraft platforms, which are able to accommodate most types of commercial communications payloads. For many applications, the lighter-weight, more-affordable Star design is an attractive alternative to the larger, more costly GEO satellites offered by other suppliers. Orbital's Star satellites are smaller and significantly less expensive to manufacture and launch. They are an ideal fit for established companies that require incremental capacity for their network or for customers in the early stages of building their business.

About Optus

Optus is an Australian leader in integrated communications, serving more than six million customers each day. In 2001, Singapore Telecon became the parent company of Optus, paving the way for Optus to become a strong and strategic telecommunications player within the Asia-Pacific region. The company provides a broad range of communications services including mobile, local, national, long distance and international telephony, business network services, dial-up and broadband internet and satellite services as well as subscription television.

    More information about Optus can be found at
http://www.optus.com.au

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, geostationary 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
             Barron Beneski, 703-406-5528
             Beneski.barron@orbital.com

    SOURCE: Orbital Sciences Corporation