DULLES, Va.May 25, 2006--Orbital Sciences Corporation (NYSE:ORB):

  -- Two Minotaur I Rockets to Launch the TacSat-2 and -3 Satellites
             Within a One-Year Period in 2006 and 2007 --

   -- 2006 Mission to Demonstrate Quick-Reaction Launch Service Just
                  Six Months After Contract Award --

Orbital Sciences Corporation (NYSE:ORB) today announced that it has been awarded a $23 million contract for two Minotaur I space launch vehicles by the United States Air Force (USAF) Rocket System Launch Program (RSLP). The two new missions will launch the TacSat-2 and TacSat-3 satellites in 2006 and 2007, respectively. The TacSat-2 launch will demonstrate Orbital's ability to carry out an operationally responsive launch service just six months after the contract award. The second launch is scheduled to take place within a year of the first launch, currently scheduled for September 2007.

"We are very excited about meeting the challenging six month contract-to-launch goal that the Air Force has set for us on the TacSat-2 mission," said Mr. Ron Grabe, Orbital's Executive Vice President and General Manager of its Launch Systems Group. "We are also pleased to be able to offer the Air Force exceptional value for these two critical missions that will be carried out within a one-year period aboard our proven and reliable Minotaur I launch vehicle. This selection serves as a testament to our demonstrated track record of success in terms of technical, schedule and cost performance. We have already assembled our launch team for the TacSat-2 mission and are looking forward to conducting the second Minotaur I launch of 2006."

In April, six Orbital-designed FORMOSAT satellites were launched into low-Earth orbit aboard a Minotaur I rocket in a flawless mission that originated at Vandenberg Air Force Base in California. The TacSat-2 mission will be the sixth space launch of a Minotaur I rocket. All of the previous five missions have been fully successful.

The TacSat-2 and -3 satellites are two in a series of experimental spacecraft designed to demonstrate new technologies and capabilities for providing responsive space-based support of military operations. The TacSat series of satellites, plus the quick-reaction Minotaur I launches, are key parts of the U.S. government's effort to develop Operationally Responsive Space (ORS) systems. The Air Force Research Laboratory (AFRL) at Kirtland AFB, NM is leading the TacSat-2 and -3 joint development teams in partnerships that include space organizations from the Air Force, Navy and Army.

The rockets that will launch TacSat-2 and -3 satellites are the seventh and eighth Minotaur I space launch vehicles to be ordered by the USAF and are the 18th and 19th orders placed for the complete Minotaur family of launch vehicles.

About Orbital's Minotaur Product Line

Orbital's Minotaur product line was developed under the USAF's Orbital/Suborbital Program (OSP). The initial five-year OSP-1 contract was competitively awarded to Orbital in 1997 and the company also won the follow-on 10-year OSP-2 contract in 2003. The Minotaur I space launch vehicle design is the original member of Orbital's Minotaur family of launch vehicles, which includes both space launch vehicle designs and long-range suborbital vehicles for missile defense and other specialized launch missions.

The Minotaur I, IV and V space launch configurations combine Orbital's commercial launch vehicle technologies, including upper stage rocket motors, avionics and other elements, with government-supplied lower-stage rocket motors stages to create responsive, reliable and low-cost launch systems for U.S. Government-sponsored payloads. These are flight-proven launch vehicles capable of supporting the Department of Defense's ORS launch requirements.

The Minotaur vehicles are specifically designed to be capable of launching from all U.S. spaceports, including government and commercial launch sites in Alaska, California, Florida, and Virginia. Due to the minimal amount of specialized infrastructure that is required to support Minotaur launches, they can also be employed at other domestic launch sites.

The Minotaur I space launch vehicle made its inaugural flight in January 2000, successfully delivering multiple small military and university satellites into orbit. Its second mission was carried out less than six months later with the launch of the MightySat II technology demonstration satellite for AFRL in May 2000. The most recent three missions were all conducted within a one-year period, beginning with the April 2005 launch of the XSS-11 spacecraft for AFRL. That mission was closely followed by the launch of a classified DARPA satellite in September 2005. The most recent Minotaur I mission took place in April 2006 with the launch of six FORMOSAT satellites for the National Space Program Office of Taiwan.

In addition to the Minotaur I space booster, Orbital's Minotaur product line also includes:

    --  Minotaur II - A three-stage suborbital rocket, used as a
        long-range target vehicle for testing U.S. missile defense
        systems and related missions.

    --  Minotaur III - A three-stage suborbital rocket, also used as a
        long-range target vehicle for testing U.S. missile defense
        systems and similar missions.

    --  Minotaur IV - A heavier-lift four-stage space launch vehicle
        used to place U.S. Government-sponsored satellites weighing up
        to 3,800 lbs. into low-Earth orbit. The first Minotaur IV
        mission is currently under contract to launch the Space-Based
        Surveillance System (SBSS) satellite for the U.S. Air Force.

    --  Minotaur V - An enhanced-performance version of the Minotaur
        IV space launch vehicle that may be used to launch government
        satellites into higher-energy orbits for missions related to
        space exploration and other activities beyond low-Earth orbit.

    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-orbit 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

Note to Editors:

High-resolution photos of the Minotaur I rocket are available on Orbital's website at: http://www.orbital.com/NewsInfo/Images/SpaceLaunch/index.html

More information about the Minotaur I launch vehicle can be found at: http://www.orbital.com/SpaceLaunch/Minotaur/index.html

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

    SOURCE: Orbital Sciences Corporation