Orbital Sciences Corporation (NYSE: ORB), one of the world’s leading space technology companies, today announced that it is prepared to launch the first orbital mission of the Minotaur IV rocket in support of the Air Force’s Space Based Space Surveillance (SBSS) satellite, also known as SBSS Block 10. The Minotaur IV rocket is the latest in the family of highly reliable, cost-effective Minotaur launches that Orbital has developed for the U.S. Air Force. The SBSS mission will be the 18th to be carried out by Orbital’s family of Minotaur vehicles over the last 10 years. The previous 17 missions have all been successful.

The Minotaur IV launch vehicle is based on decommissioned Peacekeeper rocket motors that Orbital has upgraded and integrated with modern avionics and other subsystems to produce a cost-effective space launcher based on flight-proven hardware. Subject to final preparations and favorable weather conditions, the mission will originate from Space Launch Complex-9 at Vandenberg Air Force Base, CA, with an available launch window from 9:41 to 9:55 p.m. (PDT) on Saturday, September 25, 2010.

SBSS Block 10 will complement an array of ground-based sensors to detect and track objects in space, such as satellites and orbital debris, to enhance operations and situational awareness. NASA may also use information collected by SBSS Block 10 to maneuver the International Space Station away from threatening orbital debris.

This mission will be the inaugural orbital flight of the Minotaur IV, which is capable of carrying out a variety of orbital and suborbital missions for the U.S. Air Force and other customers. Orbital currently has eight additional Minotaur IV launches scheduled, the next of which will launch STP-S26, a research and development mission for the Air Force that will carry seven small satellites with 16 experimental payloads into orbit.

“Building upon the success of our first Minotaur IV launch earlier this year, a suborbital mission for DARPA, we are excited to begin executing our backlog of Minotaur IV orbital missions, beginning with the SBSS mission,” said Mr. Ron Grabe, Orbital’s Executive Vice President and General Manager of its Launch Systems Group. “By developing all the Minotaur systems using existing, flight-proven components, we have been able to provide reliable and cost-effective launch services for a wide range of government missions for the past decade.”

About Minotaur IV

The Minotaur IV space launch vehicle leverages the flight-proven heritage of Orbital’s Minotaur I, Pegasus and Taurus space launch vehicles to provide a highly reliable, capable and cost-effective space launcher. It utilizes three government-furnished solid rocket motors from decommissioned Peacekeeper ICBMs and, in certain configurations, commercial solid rocket upper stages. The Minotaur IV rocket is capable of launching payloads up to 4,000 lbs. (1,820 kgs.) to low-Earth orbit.

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 exploration 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 U.S. Government agencies and laboratories. More information about Orbital can be found at http://www.orbital.com.

Note to Editors: High-resolution images of the Minotaur IV rocket can be found at: http://www.orbital.com/NewsInfo/ImagesMultimedia/Images/SpaceLaunch