DULLES, Va.June 22, 2006--Orbital Sciences Corporation (NYSE:ORB) announced today that its Transportation Management Systems (TMS) division has been awarded a $9.2 million contract by the Hillsborough Area Regional Transit Authority (HART) in Tampa, Florida. Under the contract, Orbital TMS will provide its latest Computer Aided Dispatch (CAD) and Automatic Vehicle Location (AVL) system, known as OrbCAD XP. This new system is designed to enable HART to operate more efficiently, cost-effectively and safely, using real-time satellite-based Global Positioning System (GPS) information to manage its fleet of over 300 fixed route, paratransit and support vehicles. In addition to GPS, other system features include: improved voice and data communications between vehicle operators and dispatchers, automated next stop announcements, passenger count collection and reporting, automated paratransit manifests for efficient transportation solutions for disabled citizens, video monitoring on board buses and at transit hubs for improved safety and security, and the SmartTraveler information system that displays arrival information at selected transit centers and bus stops.

"All of us at HART are excited about the installation of Orbital's vehicle management system because it will help us serve our customers in a whole new way," said Mr. Ray Miller, HART's Executive Director. "It's an investment in HART's future that will pay off for passengers almost immediately, since it will give them a great riding experience and a safer environment. The features the system offers, like up-to-the-minute schedule information and improved safety and security, will be a great benefit to the people of Hillsborough County."

Mr. Miller added, "The information that will be available to us now is invaluable. We'll be able to use the new data generated by the system to operate more efficiently, better stick to published schedules, or make changes to schedules based on what's really happening on the street. All the great features and functions of this system will help us control operational costs by increasing our capability to monitor, analyze and manage all of our operations."

When the OrbCAD XP system is operational, a variety of tools will be at HART's disposal to effectively manage its fleet of vehicles. In addition to being able to pinpoint each vehicle's location and operational status, HART's managers will be able to monitor route and schedule performance while being able to access the number of passengers that are on board each bus in the system. A key feature will allow paratransit vehicle operators to receive their manifests, or daily schedules, with real-time updates during their shift, leading to improved customer responsiveness.

The fully integrated vehicle equipment suite will simplify driver operations and automate ADA-compliant stop announcements to the public. HART's dispatchers and bus operators will have the ability to automate the coordination of passenger transfers at any of HART's four transit centers throughout Tampa.

Mr. A. David Kachemov, Senior Vice President and General Manager of Orbital TMS, said, "Orbital is proud to have been selected to partner with Tampa's HART to provide our OrbCAD XP solution. Enhanced customer service, greater responsiveness to incidents and improved situational awareness are just some of the benefits that HART will realize from Orbital's system. Additionally, the OrbCAD XP system is scalable and will allow HART to upgrade and add features as it chooses."

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 60 public transit and state agency customers in the U.S. and internationally, with units installed or scheduled to be installed on approximately 27,500 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 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 Sciences Corporation 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