SORCE Mission Was 32nd Flight of Air-Launched Pegasus Rocket And Its 18th Consecutive Success

Orbital Sciences
Corporation announced that on Saturday, January 25, it
successfully launched the National Aeronautics and Space Administration’s
(NASA’s) Solar Radiation and Climate Experiment (SORCE) satellite into its
targeted orbit aboard the company’s Pegasus® rocket. The 315 kilogram (693
pound) SORCE scientific satellite, which Orbital also designed and built at
its Dulles, Virginia, satellite manufacturing facility, was accurately
delivered into its targeted orbit approximately 640 kilometers (400 miles)
above the Earth, inclined at 40 degrees to the equator.

Mr. David W. Thompson, Orbital’s Chairman and Chief Executive Officer,
said, “The successful launch of the SORCE satellite underscores the
reliability of the Pegasus launch system. We are exceptionally pleased to
begin a very busy 2003 operational campaign for the Pegasus program with such
a successful mission.”

Mr. Thompson continued his remarks, saying, “We wish NASA and the
University of Colorado’s Laboratory for Atmospheric and Space Physics the
greatest of success in their important scientific mission to study the Sun and
its influence on Earth’s climate.”

The powered flight sequence for the SORCE mission took about 11 minutes,
from the time the Pegasus rocket was released from its L-1011 carrier aircraft
at 3:14 p.m. (EST) to the time that the satellite was deployed into orbit.
Preliminary information indicates that the SORCE satellite is working as
planned in the early stages of its mission.

About the Pegasus Launch System

The SORCE mission, which originated from Cape Canaveral, Florida, was the
32nd flight of the Pegasus air-launch system, a depth of experience unmatched
by any other small commercial space launch vehicle. The SORCE mission was
also the 18th consecutive success for Pegasus, a record of reliability that
has led NASA to certify the vehicle as the only small launch vehicle in its
Payload Risk Category 3, which the space agency reserves for its highest value
space missions.

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.

About the SORCE Mission

Orbital designed and built the SORCE satellite 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 carries four instruments on board.

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

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