New Order Is Third Spacecraft Ordered by Australia-Based Satellite Services Company

Optus D3 Satellite to Broadcast Digital Television to Australia and New Zealand

(Dulles, VA 29 March 2007) – Orbital Sciences Corporation (NYSE: ORB) announced today that one of its current satellite customers, Australia’s Optus Networks, has placed a firm order for its third STAR™ communications satellite as an addition to its in-orbit fleet. The Optus D3 satellite will provide Ku-Band direct television broadcasting services to Australia and New Zealand. The new satellite, like Optus D1 and Optus D2, will be based on Orbital’s STAR platform and will carry a total of 32 transponders and is scheduled for delivery in 2009.

Commenting on the contract award, Mr. Carl A. Marchetto, Orbital’s Executive Vice President and General Manager of its Space Systems Group, said, “We are thrilled with Optus’ continued acquisition of Orbital’s STAR satellites. With the Optus D1 spacecraft already deployed in the Optus fleet and the Optus D2 satellite scheduled for launch later this year, we are looking forward to another opportunity to work with one of our most important customers. We are fully committed to working closely with the Optus team to build on our already solid relationship, to help ensure Optus meets the needs of the customers they serve.”

Orbital has experienced strong growth in its commercial communications satellite business over the past several years. To accommodate this rapid growth, the company recently completed an expansion of its Satellite Manufacturing Facility in Dulles, Virginia. This year also promises to be another busy period for Orbital’s commercial satellite business. In addition to the award of the Optus D3 satellite, the first of several orders expected to be placed this year, Orbital is schedule to deliver four other geosynchronous communications satellites for launch throughout 2007. Included in this year’s deliveries are the Optus D2, Intelsat-11, Horizons-2 and THOR 5 spacecraft. This production and delivery schedule will allow for efficient production flow through the manufacturing and testing facility for the satellites now in production and for those anticipated to be ordered during this year and next.

Mr. Steve Christian, Acting Managing Director of Optus Networks, said the additional satellite cements Optus’ position in the Asia Pacific region as the industry leader as its business goes from strength-to-strength with a fleet of satellites that will be one of the youngest in operation. “The decision to build a third D-series satellite with Orbital follows increased demand for access, especially for television broadcast services with major broadcasting companies signing up for services that rely on the new Optus D3 satellite as part of a robust broadcasting future for Australia and New Zealand. We are looking forward to our continuing relationship with Orbital.”

Orbital’s highly successful communications satellites are based on the company’s STAR spacecraft platform, which is able to accommodate all types of commercial communications payloads. The STAR design is optimized for smaller satellite missions, generating up to five kilowatts of payload power. For many applications, the lighter-weight, more-affordable STAR design is an attractive alternative to the larger, more costly 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. The company provides a broad range of communications services including mobile, national and long distance services, local telephony, business network services, 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