SORCE Mission will be 32nd Flight of Company’s Air-Launched Rocket – – Solar Observation Satellite Developed and Built by Orbital

Orbital Sciences
Corporation today announced that it is in final preparations to
launch the National Aeronautics and Space Administration’s (NASA) Solar
Radiation and Climate Experiment (SORCE) satellite aboard the company’s
Pegasus® rocket. The launch is currently scheduled to take place on
Saturday, January 25, 2003 and will originate from Cape Canaveral, FL. The
available launch window for the SORCE mission extends from 3:10 p.m. to 4:08
p.m. (Eastern Standard Time), with a targeted launch time of 3:15 p.m. on
Saturday. This operational schedule is subject to the completion of final
pre-launch activities, as well as acceptable weather conditions at Cape
Canaveral at the time of the launch.

The powered flight sequence for the SORCE mission is expected to take
approximately 11 minutes, from the time the Pegasus rocket is released from
the L-1011 carrier aircraft to the time that the satellite is deployed into
orbit. Orbital plans to launch the 315 kilogram (693 pound) SORCE spacecraft
into a circular orbit 645 kilometers (400 miles) above the Earth, inclined at
40 degrees to the equator.

About Pegasus

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, reduces cost and provides customers with unparalleled
flexibility to operate from virtually anywhere on Earth with minimal ground
support requirements.

The SORCE mission will be the 32nd flight of the Pegasus rocket and its
first mission in 2003. Several other Pegasus missions are currently scheduled
for this year, including the launch of the Galaxy Evolution Explorer (GALEX)
satellite for Jet Propulsion Laboratory, the SCISAT scientific spacecraft for
NASA/Kennedy Space Center and the Canadian Space Agency, and the OrbView-3
high-resolution imaging satellite for ORBIMAGE.

About SORCE

Orbital designed and built the SORCE satellite at its Dulles, VA
manufacturing facility for NASA under contract to the Laboratory for
Atmospheric and Space Physics at the University of Colorado in Boulder,
Colorado. The SORCE program merges two previous scientific efforts: the Solar-
Stellar Irradiance Comparison Experiment/Solar Atmospheric Variability
Explorer (SOLSTICE/SAVE) mission and the Total Solar Irradiance Mission
(TSIM). The SORCE satellite is based on the company’s state-of-the-art LEOStar
platform and will carry four instruments on board.

The mission of the SORCE satellite is to provide state-of-the-art
measurements of incoming x-ray, ultraviolet, visible, near-infrared and total
solar radiation. The measurements provided by the SORCE spacecraft will
address long-term atmospheric change, climate prediction, atmospheric ozone
and ultraviolet-B radiation. These measurements are critical to the study of
the Sun, its effect on Earth’s atmosphere and its influence on mankind.

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