SORCE Spacecraft to be Integrated with Pegasus Rocket at Kennedy Space Center in Preparation for December Launch

Orbital Sciences
Corporation announced today that it has shipped the Solar
Radiation and Climate Experiment (SORCE) satellite to the launch site at the
National Aeronautics and Space Administration’s (NASA) Kennedy Space Center
(KSC), Cape Canaveral, Florida. In conjunction with a team from NASA and the
University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP),
Orbital designed, manufactured, integrated and tested the spacecraft at the
company’s Dulles, Virginia facilities. In addition to supplying the
satellite, Orbital is also the launch vehicle provider for the mission, using
the company’s unique air-launched Pegasus rocket. The SORCE mission is
currently scheduled for a mid-December launch.

Unlike previous Pegasus missions that have flown from Cape Canaveral, the
majority of the pre-launch activities during the final month before SORCE is
launched are taking place at KSC. On typical Pegasus missions, the satellite
is first shipped to Orbital’s facility at Vandenberg Air Force Base,
California for integration with the rocket. The combined system is then flown
on a cross-country ferry flight to the Florida site. For the SORCE mission,
Orbital will fly the Pegasus rocket to Florida in early November and will
complete the integration of the satellite and conduct final testing prior to
the launch at KSC’s Multi-Purpose Processing Facility (MPPF).

About the SORCE Satellite

The SORCE mission is being led by a principal investigator from LASP with
NASA’s Goddard Space Flight Center providing project management and
engineering oversight. Scientists and engineers at LASP designed, built,
calibrated and tested the four science instruments on SORCE. The Mission
Operations Center and the Science Operations Center are both located at LASP,
which will operate the spacecraft over its five-year mission life and is
responsible for the acquisition, management, processing and distribution of
the science data.

SORCE is a key component of NASA’s Earth Observing System (EOS) program.
SORCE will address long-term climate change, natural variability and enhanced
climate prediction, as well as atmospheric ozone and UV-B radiation. These
measurements are critical to the study of the Sun and its effect on Earth and
humankind.

About the Pegasus Rocket

Pegasus is the world’s leading launch system for the deployment of small
satellites into low-Earth orbit. Its patented air-launch approach, in which
the rocket is launched from beneath an L-1011 carrier aircraft over the ocean,
reduces cost and provides customers with unparalleled flexibility to operate
from virtually anywhere on the planet. Pegasus has successfully completed 28
out of 31 missions since the early 1990’s and has spawned several derivative
vehicles, including Orbital’s Taurus and the U.S. Government’s Minotaur space
launch vehicles.

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 include low-orbit, geosynchronous
and planetary spacecraft for communications, scientific and remote sensing
missions; ground- and air-launched rockets that deliver satellites into orbit;
and missile defense boosters that are used as target and interceptor 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 .

Notes to editors:

A SORCE mission Fact is available on Orbital’s web site at:
http://www.orbital.com/NewsInfo/Publications/index.html

High-resolution (300+ d.p.i.) photos of the Pegasus rocket are available
on Orbital’s web site at:
http://www.orbital.com/NewsInfo/Images/SpaceLaunch/index.html

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