-- Southeastern Pennsylvania Transportation Authority (SEPTA) Will

Receive Orbital's State-of-the-Art Community Transit System Solution

to Assist the Agency in Effectively Managing Its Customized Community

                       Transit (CCT) Services --

DULLES, Va.May 7, 2007--Orbital Sciences Corporation (NYSE:ORB) announced today that its Transportation Management Systems (TMS) division has been awarded a $17.8 million contract by the Southeastern Pennsylvania Transportation Authority (SEPTA) to provide an advanced system to help manage the Philadelphia area's paratransit system, known as Customized Community Transportation (CCT). SEPTA's CCT is the second-largest demand-responsive system in the U.S. providing transportation services for people with disabilities and seniors.

Orbital is providing an integrated communications, customer information and fleet management system to help improve the operational efficiency and overall service levels of the CCT. Orbital's state-of-the-art system provides modern voice and data communications, implements the latest advances in scheduling and dispatch software, and improves the process for the determination of paratransit eligibility of all CCT customers. The system will also increase the amount of real-time information that can be provided to CCT's supervisors and operators, allowing for better management of the CCT fleet of vehicles.

Orbital's solution will help SEPTA provide transportation solutions that fully support the guidelines of the Americans with Disabilities Act (ADA). Orbital's CCT system includes a wide-area, six-site data communication system to provide reliable communications between SEPTA's central operations and its fleet of vehicles operating over an area of almost 2,000 square miles. Orbital's OrbStar mobile data terminal will be installed on each vehicle in the fleet to provide constant two-way communication to central operations, turn-by-turn navigational directions on a color screen, and real-time manifest updates. These new features allow SEPTA to track vehicle progress and adjust to changes in customer requests. The central site includes the addition of an advanced scheduling and dispatch system that optimizes service planning for SEPTA customers, provides on-line access to service registration and trip booking, implements an Interactive Voice Response system to provide improved access to service users, and includes provisions to accept customer comments that can be used to improve service.

Mr. A. David Kachemov, Senior Vice President and General Manager of Orbital TMS, said, "Since SEPTA has been one of Orbital's long-standing customers for fixed-route fleet management products, we are very eager to extend our innovative suite of fleet management solutions to SEPTA's CCT paratransit services."

Mr. Kachemov continues his remarks, adding, "SEPTA's CCT employees will receive multi-functional features to improve the management of the fleet while CCT's passengers will receive valuable tools that will make it easier to book trips, thereby enhancing the CCT customers' traveling experience. There is a growing emphasis on providing mobility for an expanding senior population and for making sure that people with disabilities have dependable, high-quality paratransit services. Orbital will continue to develop products for this growing market."

About Orbital TMS

Orbital TMS is a leading integrator of products for fleet and workforce management, mobile data communications, data management, and advanced traveler information systems. TMS provides integrated Computer Aided Dispatch (CAD) and Automatic Vehicle Location (AVL) solutions for sixty public transit and state agency customers in the U.S. and internationally, with units installed or scheduled to be installed on approximately 28,000 vehicles. More information about Orbital TMS can be found at http://www.orbitaltms.com.

About Orbital

Orbital develops and manufactures small space and rocket systems for commercial, military and civil government customers. The company'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.

    CONTACT: Orbital Sciences Corporation
             Public and Investor Relations:
             Barron Beneski, 703-406-5528

    SOURCE: Orbital Sciences Corporation