DULLES, Va., Sep 20, 2001 /PRNewswire/ --

- Company's Ground-Launched Rocket to Deliver ORBIMAGE's OrbView-4 Satellite And NASA's QuikTOMS Ozone Monitoring Spacecraft to Orbit - - Orbital's Space Technology Capabilities Showcased in a Mission That Includes Two Company-Built Satellites, the TOMS Space Sensor and the Taurus Launch Vehicle -

Orbital Sciences Corporation (NYSE: ORB) announced today that it is in final preparations to launch its Taurus(R) rocket, which will carry two satellites and another small commercial payload into orbit, on Friday, September 21, 2001. The available launch window extends from 11:49 a.m. to 12:07 p.m. (Pacific time), with a targeted launch time of 11:50 p.m. This schedule is subject to final preparations and testing, as well as acceptable weather conditions at the Vandenberg Air Force Base, California, launch site at the time of the mission.

Onboard Orbital's four-stage ground-launch rocket will be the OrbView-4 high-resolution and hyperspectral imaging satellite that Orbital built for Orbital Imaging Corporation (ORBIMAGE). Also onboard will be Total Ozone Mapping Spectrometer spacecraft, known as QuikTOMS, which Orbital developed for NASA's Goddard Space Flight Center and for which the company built the ozone mapping instrument. In addition, the Taurus rocket will carry a small payload for Celestis, Inc., which will not separate from the rocket's final stage once it reaches orbit.

On launch day, the Taurus rocket will be prepared for its mission during a four-hour countdown procedure. Following a final launch decision, the vehicle will ignite its first stage rocket motor, lift off and follow a pre-programmed launch sequence controlled by its onboard flight computer. Approximately 11 and a half minutes after liftoff, Taurus will deliver the OrbView-4 spacecraft into a Sun-synchronous orbit approximately 470 kilometers above the Earth. About two and a half minutes later, Taurus will also deploy the QuikTOMS satellite into a Sun synchronous orbit at 470 kilometers above the Earth. Over the next month, the QuikTOMS satellite's onboard propulsion system will boost the spacecraft into its final 800-kilometer orbit.

About the Taurus Launch System:

Orbital developed the ground-launched Taurus vehicle to provide a cost- effective, reliable means of launching satellites weighing up to 3,000 pounds into low-Earth orbit. Taurus incorporates advanced structural and avionics technology proven on Pegasus and other operational launch systems. It is also designed for easy transportability, offering customers rapid-response launches from a wide range of locations. Since its debut in 1994, the Taurus rocket has carried out five space missions, all of which have been successful. The most recent Taurus mission occurred in April 2000, when the rocket launched the U.S. Department of Energy's Multispectral Thermal Imager (MTI) satellite.

About the OrbView-4 Satellite

The Orbview-4 satellite that Orbital developed and built for ORBIMAGE will be one of the world's first commercial satellite to provide high-resolution imagery from space. OrbView-4's digital electro-optical camera will acquire one-meter resolution panchromatic (black and white) and four-meter resolution multispectral (color) imagery. In addition, OrbView-4 will be the world's first commercial satellite to deliver hyperspectral imagery for commercial applications, such as classifying material types on the Earth's surface, a capability that will be beneficial in agricultural management, mineral exploration and environmental monitoring. More information about the OrbView- 4 satellite and high-resolution and hyperspectral imagery can be found at: http://www.orbimage.com .

About the QuikTOMS Satellite

The QuikTOMS satellite, which Orbital built for NASA's Goddard Space Flight Center, is based on the company's flight-proven MicroStar spacecraft, on which nearly 40 in-orbit satellites have been based over the last six years. Originally developed for the ORBCOMM data communications network, the MicroStar design has been readily adapted to missions for NASA, DARPA and several commercial and international customers. The MicroStar platform has provided cost and schedule benefits to the QuikTOMS program through the use of mature designs, automated manufacturing and test equipment, dedicated and experienced personnel, and established vendors. More information about the QuikTOMS program can be found at: http://www.gsfc.nasa.gov/topstory/20010705quiktoms.html .

About the TOMS Sensor

Orbital's Sensor Systems Division has built four of the five Total Ozone Monitoring System (TOMS) sensors flown by NASA, including the one that will operate aboard the QuikTOMS satellite. Flown on U.S., Russian and Japanese satellites beginning in the early 1980's, these instruments have enabled the international scientific community to better understand the Earth's ozone layer and the factors that alter atmospheric ozone distribution. The previous Orbital-built TOMS sensor, launched aboard a NASA Earth Probe satellite in 1996, operated well beyond its expected in-orbit lifetime, providing the world's most widely used data on the Earth's ozone layer.

In addition, the sensor gathered information on other important atmospheric conditions, including aerosol particles from desert dust storms, forest fires and biomass burning, UV-B radiation, and Earth surface and cloud reflectance.

About Orbital

Orbital develops and manufactures affordable space systems, including satellites, launch vehicles, sensors and electronics, and advanced systems. Orbital is also involved with satellite-based networks that provide wireless data communications and high-resolution Earth imagery to customers all around the world. More information about Orbital can be found at: http://www.orbital.com .

CONTACT: Barron Beneski, Public Relations of Orbital Sciences Corporation, +1-703-406-5528, or beneski.barron@orbital.com.

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SOURCE Orbital Sciences Corporation

CONTACT:          Barron Beneski, Public Relations of Orbital Sciences
                  Corporation, +1-703-406-5528, or beneski.barron@orbital.com