DULLES, Va., Sep 23, 2005 (BUSINESS WIRE) -- Orbital Sciences Corporation (NYSE:ORB) announced today that it successfully launched a satellite for the Defense Advanced Research Projects Agency (DARPA) aboard a company-built Minotaur I rocket. The mission, called STP-R1, originated on Thursday, September 22, 2005 at approximately 10:25 p.m. (EDT) from Vandenberg Air Force Base (VAFB), CA when the Minotaur rocket ignited its first stage motor and lifted-off from its West Coast launch site. Approximately nine minutes after launch, the STP-R1 satellite was inserted into its targeted orbit of approximately 300 kilometers above the Earth. Yesterday's mission was the fourth flight of the Minotaur I space launch vehicle, all of which have been successful.

Since the program's first flight in 2000, the Minotaur family of space and suborbital launch vehicles has carried out nine launches with 100% success. Over the next three years, Orbital is scheduled to conduct another eight launches of the Minotaur family of rockets.

About Orbital's Minotaur Product Line

The Minotaur I space launch vehicle used in yesterday's successful launch of the STP-R1 satellite is the initial member of Orbital's Minotaur family of launch vehicles, which include both space launch vehicles as well as long-range missile defense targets and other suborbital vehicles. The rockets are derived from U.S. Government-supplied Minuteman and Peacekeeper rocket motors. The space launch configurations combine commercial rocket motors, avionics and other elements with the government-supplied stages to create responsive, reliable and low-cost launch systems for U.S. Government payloads.

The Minotaur I configuration includes Minuteman II rocket motors that serve as the vehicle's first and second stages, efficiently reusing motors that have been previously decommissioned. Its third and fourth stages, structures and payload fairing are common with Orbital's highly reliable Pegasus XL rocket.

The Minotaur I space launch vehicle made its inaugural flight in January 2000, successfully delivering a number of small military and university satellites into orbit and marking the first-ever use of residual U.S. Government Minuteman boosters in a space launch vehicle. Its second mission was carried out less than six months later, in July 2000, with the launch of a technology demonstration satellite for the U.S. Air Force Research Laboratory. The most recent mission was in April 2005, launching the Air Force's XSS-11 spacecraft from Vandenberg AFB.

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

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

-- Minotaur III - A Peacekeeper-based three-stage suborbital rocket also used as a target vehicle for testing U.S. missile defense systems and similar missions. The first Minotaur III is under contract as a launch vehicle for DARPA's Hypersonic Test Vehicle (HTV), which is part of the FALCON program.

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

-- 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 is one of the world's leading developers and manufacturers of affordable space systems for commercial, civil government and military customers. The company's primary products are satellites and launch vehicles, including geostationary and low-orbit 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.

Note to editors: A high-resolution photo of the Minotaur I rocket is available on Orbital's web site at: http://www.orbital.com/images/high/Minotaur_pad_HR.jpg

SOURCE: Orbital Sciences Corporation

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