Orbital Set To Launch Pegasus Rocket Carrying Company-Built Autonomous Rendezvous Spacecraft For NASA

Contact: Barron Beneski, (703) 406-5000,

Orbital Set To Launch Pegasus Rocket Carrying Company-Built Autonomous
Rendezvous Spacecraft For NASA

-- Complex Mission to be Carried Out Entirely With Orbital's Space
Technology, Including Two Company-Built Satellites, On-Board Rendezvous
Sensors and the Space Launch Vehicle --

-- 36th Mission for the Pegasus Air-Launched Rocket to Originate from
Vandenberg Air Force Base, California --


(Dulles, VA 22 October 2004) - Orbital Sciences Corporation (NYSE: ORB)
announced today that it is in final preparations to launch the National
Aeronautics and Space Administration (NASA)'s Demonstration of Autonomous
Rendezvous Technology (DART) spacecraft aboard a Pegasus rocket. The mission
is scheduled to take place on Tuesday, October 26, 2004, from Vandenberg Air
Force Base, CA (VAFB) during an available seven-minute launch window that
extends from 11:15 a.m. to 11:22 a.m. (Pacific). This operational schedule
is subject to the completion of final testing and other pre-launch
activities, as well as acceptable weather conditions in the VAFB area at the
time of the launch.

About the Pegasus Launch Vehicle

Pegasus is the world's leading launch system for the deployment of small
satellites into low-Earth orbit. Its patented air-launch system, in which
the rocket is launched from beneath Orbital's "Stargazer" L-1011 carrier
aircraft over the ocean at approximately 40,000 feet, reduces cost, improves
performance and provides customers with unparalleled flexibility to operate
from virtually anywhere on Earth with minimal ground support requirements.
Orbital has launched the Pegasus rocket from six sites around the world,
including VAFB; Edwards Air Force Base, CA; Cape Canaveral, FL; Wallops
Island, VA; Kwajalein Atoll in the Central Pacific region; and the Spanish
Canary Islands. The DART mission will be the 36th flight of the Pegasus
rocket since its introduction in 1990. The Pegasus launch vehicle is
provided by Orbital under contract to NASA's Kennedy Space Center, FL.

About the DART Spacecraft

Orbital designed, developed, manufactured and tested the DART spacecraft for
NASA's Marshall Space Flight Center in Huntsville, AL. The DART spacecraft
will demonstrate key hardware and software technologies that will allow one
spacecraft to rendezvous with and conduct close-proximity operations near
another in-orbit spacecraft. While previous U.S. space rendezvous and
docking missions have been piloted by astronauts, the unmanned DART
spacecraft will have only on-board computers and data from sensors to
perform its rendezvous and close-proximity maneuvers functions.

Along with NASA's Marshall Center, Orbital also engineered, manufactured and
tested the advanced laser guidance sensor that the DART spacecraft will use
to carry out its final rendezvous and close-proximity maneuvers with its
target. Marshall pioneered the basic video laser technology in the late 1990
's, which Orbital subsequently qualified for space applications at its
Technical Services Division in Greenbelt, MD.

Future applications of the technologies that the DART mission is
demonstrating may be used in manned and unmanned missions of the U.S. space
program that require in-space assembly, servicing, docking or other
autonomous rendezvous operations. The DART spacecraft is nearly six feet
long with a diameter of about three feet and weighs about 500 pounds.

About the DART Mission

Following its launch aboard Pegasus into a targeted 475-mile polar orbit,
the DART spacecraft will locate and rendezvous with the mission's target
satellite, the Multiple-Path Beyond-Line-of-Sight Communications (MUBLCOM)
spacecraft that has completed its mission and is operating well beyond its
design life. The MUBLCOM satellite was also built by Orbital for the Defense
Advanced Research Projects Agency and was launched aboard a previous Pegasus
mission in 1999.

Once the DART spacecraft achieves orbit and locates and rendezvous with
MUBLCOM, it will perform several close-proximity operations such as
approaching to as close as 15 feet and moving away from the satellite on
different vectors, as well as performing circumnavigation maneuvers using
data provided by its onboard sensors. The entire DART mission will be
performed without human intervention and will be completed within 24 hours.

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.

More information about Orbital, the Pegasus space launch vehicle and the
DART spacecraft can be found at http://www.orbital.com

# # #
Notes to Editors:

* NASA TV will cover live the Pegasus launch of the DART spacecraft. NASA TV
is broadcast on AMC-9, transponder 9, C-band, located at 85 degrees West
Longitude. The frequency is 38880.0 MHz. Polarization is vertical and audio
is monaural at 6.8 MHz.

* Orbital will link to NASA's web-based pre-launch and live coverage of the
DART mission from the company's web site at http://www.orbital.com


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Jacques :-)

www.spacepatches.info