ORBITAL SET TO LAUNCH NASA SCIENCE SATELLITE
ABOARD PEGASUS ROCKET

-- Mission Will Mark 45th Flight of Company's Air-Launched Rocket Since 1990 --

-- Launch to Originate on Wednesday from Vandenberg Air Force Base in California --

(Dulles, VA 27 June 2013) -- Orbital Sciences Corporation (NYSE: ORB) today announced that it is in final preparations to launch NASA's Interface Region Imaging Spectrograph (IRIS) heliophysics satellite aboard the company's Pegasus air-launched rocket from Vandenberg Air Force Base (VAFB), California. The launch is scheduled to take place later today at approximately 7:27 p.m. (PDT). This schedule is subject to final pre-launch preparations, as well as acceptable weather conditions at the time of the launch.

Orbital's L-1011 "Stargazer" carrier aircraft will depart from the VAFB airfield approximately one hour prior to the targeted launch time. Following a pre-planned flight path, the Pegasus rocket will be released at approximately 39,000 feet and first stage ignition will occur approximately five seconds later. The powered flight sequence for the IRIS mission is expected to take just over 13 minutes, from the time the Pegasus rocket is released from the L-1011 to the time that the satellite is separated from the rocket's third stage and is deployed into orbit. Pegasus will launch the IRIS spacecraft into a polar, Sun-synchronous orbit approximately 400 miles above the Earth.

The launch of the IRIS spacecraft will mark the 45th overall mission for the Pegasus program. Its launch history includes 41 previous launches to orbit, which collectively have deployed over 80 satellites for Earth and space science missions overseen by NASA, military and technology demonstrations for the U.S. Department of Defense, communications and imaging satellites for commercial customers, and various missions for international customers. The unique air-launch capability of Pegasus has also been used to boost three hypersonic flight vehicles in Earth's stratosphere for NASA's HyperX program.

About the IRIS Mission

IRIS is a NASA Small Explorer mission designed to observe how solar material moves, gathers energy and heats up as it travels through a little-understood region in the Sun's lower atmosphere. This interface region between the Sun's photosphere and corona powers its dynamic million-degree atmosphere and drives the solar wind. The interface region also is where most of the Sun's ultraviolet emission is generated that impacts the near-Earth space environment and Earth's climate.

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 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. It is the world's only small space launch vehicle that is certified with NASA's Payload Risk Category 3, which the space agency reserves for its highest value space missions.
Past Pegasus flights have originated from six launch sites around the globe.

About Orbital

Orbital develops and manufactures small- and medium-class rockets and space systems for commercial, military and civil government customers. The company's primary products are satellites and launch vehicles, including low-Earth orbit, geosynchronous-Earth orbit and planetary spacecraft for communications, remote sensing, scientific and defense missions; human-rated space systems for Earth-orbit, lunar and other missions; ground- and air-launched rockets that deliver satellites into orbit; and missile defense systems that are used as interceptor and target vehicles. Orbital also provides satellite subsystems and space-related technical services to government agencies and laboratories. More information about Orbital can be found at http://www.orbital.com. Follow the company on Twitter @OrbitalSciences.

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Contact:
Barron Beneski (703) 406-5528
Public and Investor Relations
beneski.barron@orbital.com

Note to Editors:

  1. For more information about the Pegasus rocket, please visit:

http://www.orbital.com/SpaceLaunch/Pegasus/

  1. For more information about NASA's IRIS mission, please visit: http://www.nasa.gov/mission_pages/iris/index.html


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