DULLES, Va.Nov. 28, 2005--Orbital Sciences Corporation (NYSE:ORB) announced today that it has been selected by the Jet Propulsion Laboratory (JPL) to design, develop and manufacture the next satellite in the National Aeronautics and Space Administration's (NASA) series of New Millennium Program (NMP) technology demonstration spacecraft. The satellite, Space Technology 8 (ST8), will be based on Orbital's Microstar(TM) platform, a lightweight, multi-role spacecraft bus of which dozens are already in orbit performing communications and Earth and space science missions. At launch, ST8 will weigh approximately 385 lbs. (or 175 kg). In addition to the satellite contract, Orbital will also provide the mission's launch vehicle and related services, which is procured by NASA's Kennedy Space Center under a separate contract. The ST8 mission will utilize Orbital's highly reliable Pegasus(R) rocket, the world's leading small launcher for dependable transportation to low-Earth orbit. Together, the total value to Orbital of the ST8 program is expected to exceed $50 million.

The ST8 mission is a technology demonstration mission, consisting of four payload experiments. Together, these experiments aim to improve NASA's understanding of the feasibility of using these technologies for future space missions such as large solar sail missions. The four technology demonstrations include a large flexible solar array, a 40-meter deployable boom, high radiation environment electronics and a thermal radiator experiment.

The ST8 mission is scheduled for launch in early 2009 and is planned to conduct a seven-month technology demonstration mission. Orbital's overall role is to provide the spacecraft, perform the integration of the experiments with the satellite platform, conduct pre-launch environmental testing, integrate and test the satellite with the launch vehicle, plan and conduct the mission's launch operations and provide post-launch mission operations support.

Orbital's Small Satellites

Orbital has built and launched more small-class satellites than any other company by a wide margin. Over the past two decades, Orbital has delivered nearly 100 small satellites that have performed national security, commercial communications, Earth and space science, remote imaging and technology demonstration missions. Together, these satellites have amassed nearly 450 years of reliable in-orbit experience. Including the ST8 satellite, Orbital is currently under contract to deliver another 14 satellites over the next four years.

Orbital's Small-Class Space Launch Vehicles

Orbital's family of small-class space launch vehicles is the industry's standard for reliable and cost-effective launch services to low-Earth orbit. The company's Pegasus, Taurus and Minotaur rockets combined have carried out a total of 47 space missions, 43 of which have been successful, including the last 22 Pegasus launches dating back to 1996. Together, these launch vehicles have placed 99 satellites and other payloads into orbit. Over the next four years, Orbital is under contract to carry out another 10 space launch missions.

Orbital's Highly Reliable Small Space Systems

The ST8 mission will continue Orbital's extensive heritage in providing customers with a total mission package of small, highly reliable and cost-effective space systems. On numerous occasions, Orbital has been the provider of a mission's small satellite and small-class space launch vehicle, as will be the case for the ST8 mission. Several recent examples of this type of successful dual mission include the GALEX and SORCE science missions launched in 2003 for NASA, the OrbView-3 high-resolution imaging satellite also carried out in 2003 for ORBIMAGE, and the TSX-5 mission and STEP series conducted in 2000 and the mid-1990's, respectively, for the U.S. Department of Defense.

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 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