Orbital Selected by JPL for $80 Million Contract to Design and Build First Main-Belt Asteroid Spacecraft

NASA-Sponsored Dawn Mission to Journey to Solar System’s Two Largest ‘Baby Planets’

Orbital Sciences Corporation
has been selected to develop and build the first spacecraft
designed to orbit main-belt asteroids, the company announced today.
The Dawn
mission, selected by NASA as the next project in its Discovery program of
lower-cost interplanetary probes, is scheduled for launch in 2006 on a nine-
year voyage to orbit the solar system’s two largest asteroids, Ceres and
Vesta.
By observing these “baby planets,” located between Mars and Jupiter
some 250 million miles (400 million kilometers) from the Sun, Dawn will
improve our understanding of how planets formed to create the solar system
billions of years ago.
Orbital is the industry partner on the Dawn mission
team, led by Dr. Christopher T. Russell of the University of California at Los
Angeles and managed by NASA’s Jet Propulsion Laboratory (JPL).

Under an $80 million contract to JPL, Orbital will design, manufacture,
integrate and test the Dawn spacecraft and support its launch and flight
operations.
“Orbital is thrilled and honored to be chosen as JPL’s industry
partner for such an important space exploration mission,” said Mr. David W.
Thompson, Chairman and Chief Executive Officer.
“As the company’s first
planetary spacecraft, Dawn is a very exciting opportunity for us to extend and
apply the Earth-orbiting satellite technologies and know-how we developed and
used on over 75 spacecraft in the past decade to a new type of space mission.
We are looking forward to working with JPL, the world leader in interplanetary
missions, to ensure that Dawn achieves its full scientific goals,” he added.

The Dawn spacecraft will draw on extensive design heritage and operational
experience from Orbital’s LEOStar low-orbit satellites and the company’s
StarBus geosynchronous-orbit platforms.
It also will incorporate JPL’s solar-
electric (ion) propulsion system and deep-space communications link.
The
spacecraft will weigh about 2,750 pounds (1,245 kilograms) at launch and will
generate approximately 8 kilowatts of solar power at Earth’s distance from the
Sun.
The Dawn spacecraft’s core structure will measure about six feet (two
meters) high, while its solar arrays will span almost 70 feet (21 meters) in
length.

Dawn is scheduled for a mid-2006 launch by a Boeing Delta rocket,
beginning its nine-year journey through the asteroid belt during which it will
rendezvous with Vesta (in 2010) and Ceres (in 2014), orbiting from as high as
500 miles (800 kilometers) to as low as 60 miles (100 kilometers) above their
surfaces.

“Ceres and Vesta are two of the largest unexplored worlds in our solar
system.
We’ll learn about early planet formation in ways that wouldn’t have
been possible before this mission,” said Ms. Sarah Gavit, JPL’s Project
Manager for the Dawn mission.
She also noted that the Dawn spacecraft will
employ a high-performance ion rocket engine for its primary propulsion to the
asteroid belt, a new technology pioneered by JPL on NASA’s Deep Space 1
mission.
“I’m ecstatic that we’ll have such a great opportunity to show what
ion propulsion can do,” she added.

Dawn’s principal investigator, Dr. Russell of UCLA, will lead a
government/industry team consisting of JPL, Orbital, NASA’s Goddard Space
Flight Center, Germany’s DLR space agency, the Department of Energy’s Los
Alamos National Laboratory and the Institute for Space Astrophysics in Rome in
carrying out the mission.

About NASA’s Discovery Program

The Discovery program emphasizes lower-cost, highly-focused scientific
missions.
The past Discovery missions are NEAR Shoemaker, Mars Pathfinder and
Lunar Prospector, all of which successfully completed their missions.
Additional Discovery missions include Stardust and Genesis, which are now in
space, and CONTOUR, Deep Impact and MESSENGER, scheduled for 2002, 2004 and
2004 launches, respectively.

About the Jet Propulsion Laboratory

JPL, a division of the California Institute of Technology in Pasadena, CA,
manages the Dawn mission for NASA’s Office of Space Science, Washington, D.C.

About Orbital

Orbital develops and manufactures affordable space systems, including
satellites, launch vehicles, electronics and advanced space systems. 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, or beneski.barron@orbital.com