-- Company's 30-Year History Includes 146 Satellites Built and Launched,
With 81 Currently in Full Operations --

(Dulles, VA 11 March 2013) - Orbital Sciences Corporation (NYSE: ORB), one of the world's leading space technology companies, today announced that it recently achieved a significant space operational milestone. The fleet of satellites that Orbital designed, built and, in some cases, launched recently marked 1,000 years of cumulative in-orbit operational experience. This achievement has been accomplished by only four other companies since the dawn of the space age. Today, 81 of the 146 total spacecraft Orbital built over the last 30 years are fully operational, fulfilling their missions for customers in the fields of commercial communications, Earth and space science, national security, commercial imaging and others. Each day, these active spacecraft add over two and a half months to the company's cumulative in-orbit operating experience.

"This milestone is a testament to the robust design of Orbital's satellite platforms and the rigorous testing process that each spacecraft undergoes prior to launch," said Mr. David W. Thompson, Orbital's President and Chief Executive Officer. "Throughout Orbital's 30-year history, our focus has been on designing and building space systems that offer our customers an ideal combination of performance, affordability and, most important of all, reliability."

The 146 satellites built by Orbital and its predecessor companies have been deployed into low-, medium- and geosynchronous-altitude orbits, as well as into higher-energy Earth-escape trajectories. Of the satellites constructed by the company, 77 were built and launched for commercial communications and imaging customers and 69 were contracted by and delivered to government customers, such as NASA, the U.S. Department of Defense, and several international government customers. Orbital built its satellite design and manufacturing business not only through internal investments, but also through a series of strategic acquisitions that brought important technical capabilities, modern facilities and a talented workforce into the company, whose experience has added to Orbital's legacy.

Several Orbital-built spacecraft have recently reached noteworthy milestones. These include:

Landsat 5 and LDCM (Landsat 8) Remote Sensing Satellites - The Landsat 5 satellite was recently honored by Guinness World Records as the longest operating Earth observation satellite after nearly 29 years in space, far outliving its original three-year design life. Completed and launched in 1984, the satellite was officially retired by the U.S. Geological Survey in December 2012. More recently, the Orbital-built Landsat Data Continuity Mission (LDCM) satellite was launched into orbit in February 2013 and is now undergoing in-orbit testing before being placed into service and rechristened Landsat 8, extending the 40-year history of this pioneering Earth observation program.

Dawn Planetary Exploration Spacecraft - Dawn is the second interplanetary spacecraft built by Orbital. Following its launch in September 2007 and a nearly four-year journey to the main asteroid belt located between Mars and Jupiter, Dawn returned never-before-seen images of Vesta, one of the largest asteroids in the solar system, providing scientists with valuable clues to how the planets were formed. Dawn uses advanced ion propulsion, an innovative system that enabled it to reach its destination and to become the first spacecraft to orbit one body, Vesta, and then travel to and orbit another body, the nearly planet-size Ceres, where it will arrive in early 2015 and conduct another six months of observations. In total, Dawn will have traveled about three billion miles when its mission is complete in three years.

Azersat/Africasat-1 Commercial Communications Satellite - As an example of Orbital's end-to-end satellite system capabilities, Orbital designed, built and tested the Azersat/Africasat-1 commercial communications satellite for the Republic of Azerbaijan. With its launch in February 2013, Azerbaijan's Ministry of Communications and Information Technologies for the first time will soon be able to provide its citizens and government organizations with a modern, nationwide and international communications infrastructure based on the capabilities of Orbital's 5-kilowatt geosynchronous satellite that carries 36 active C- and Ku-band transponders. Orbital also designed and built the ground-based command and control network and provided pre-launch satellite operations training for a staff of Azerbaijani engineers.

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.

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Barron Beneski (703) 406-5528
Public and Investor Relations
Orbital Sciences Corporation

Note to Editors:
High-resolution images of Orbital satellites can be found at: http://www.orbital.com/NewsInfo/ImagesMultimedia/Images/