ST5 Mission Will be the First Pegasus Launch in 2006 and 37th in the Program’s 16-Year History

Orbital Sciences Corporation today announced
that it is in final preparations to launch the Space Technology 5
(ST5) scientific spacecraft for the National Aeronautics and Space
Administration (NASA) aboard the company’s Pegasus® rocket. The
launch is currently scheduled to take place on Wednesday, March 15,
2006 from Vandenberg Air Force Base (VAFB), California, during an
available launch window that extends from 8:57 to 10:19 a.m. (EST).
The targeted mission launch time is 9:02 a.m. (EST). This operational
schedule is subject to the completion of final pre-launch activities,
as well as acceptable weather conditions at VAFB at the time of the
launch.

The powered flight sequence for the ST5 mission is expected to
take approximately 11 minutes, from the time the Pegasus rocket is
released from its L-1011 carrier aircraft to the time that the three
ST5 satellites are deployed into orbit. Orbital plans to launch the
55-pound spacecraft into a highly elliptical orbit of 186 by 2,796
miles above the Earth at an inclination of 105.6 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.

For the ST5 mission, Orbital will employ a unique satellite
deployment system called the Pegasus Support Structure, which is a
spring-loaded mechanism that intentionally spins the satellites at
preset time intervals in order to create a formation-flying group of
spacecraft in low-Earth orbit.

The ST5 mission will be the 37th flight of the Pegasus rocket and
the first of two planned missions in 2006. Later in the year, Orbital
is scheduled to launch NASA’s Aeronomy of Ice in the Mesosphere (AIM)
spacecraft, which is now in production at Orbital’s Dulles, Virginia
satellite manufacturing facility.

About ST5

NASA’s New Millennium Program’s ST5 spacecraft consists of three
microsats that are designed to validate, in actual flight conditions,
innovative technology concepts that may reduce risks to future science
missions. The ST5 mission will demonstrate the ability of small
satellites to perform research-quality science by taking measurements
of the Earth’s magnetic field using highly sensitive magnetometers.

About Orbital

Orbital develops and manufactures small space systems for
commercial, civil government and military customers. The company’s
primary products are satellites and launch vehicles, including
low-orbit, geostationary-orbit 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

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