Orbital Awarded Five-Year Satellite Production Contract by NASA

(Dulles, VA 28 DECEMBER 1999) — Orbital Sciences Corporation (NYSE: ORB) announced today that the National Aeronautics and Space
Administration’s (NASA) Goddard Space Flight Center has awarded the company a five-year contract for design, production and testing of small- and
medium-class satellites used in space science, Earth science and advanced technology missions. The contract, administered by Goddard’s Rapid Spacecraft
Development Office, allows NASA centers and laboratories, as well as other U.S. Government agencies, to procure a wide range of flight-proven satellites
from the company. The contract covers orders made by NASA and other agencies from 2000 to 2004 and has a maximum value of $1.5 billion to Orbital.

Under the Rapid Spacecraft Acquisition contract, NASA can purchase five different types of satellite platforms developed and manufactured by Orbital,
including both low-Earth orbit and geosynchronous orbit spacecraft. Each of these satellite types has successful space flight heritage from an extensive
history of 85 previous satellite missions carried out by the company in the last 18 years. Due to its flexible ordering structure, the contract will shorten
NASA’s satellite order-to-delivery cycle to as little as 18 months, permitting it to carry out faster and more effective space missions over the next five
years.

“We are delighted to have Goddard’s Rapid Spacecraft Development Office qualify five of our satellites under this new contract,” said Mr. Robert R.
Lovell, Executive Vice President and General Manager of Orbital’s Space Systems Group. “We expect this contract to help us maintain or increase our
already sizable share of the U.S. Government’s small and medium satellite business.”

Orbital is one of the largest space technology and satellite services companies in the world, with 1999 revenues targeted to exceed $900 million. The
company, which is headquartered in Dulles, Virginia, employs over 5,200 people at its major facilities in the United States, Canada and several overseas
locations. Orbital is the world’s leading manufacturer of low-cost space systems and products, including satellites, launch vehicles, electronics and
sensors, satellite ground systems and software, and satellite-based navigation and communications products. Through its ORBCOMM and ORBIMAGE
affiliates and ORBNAV subsidiary, Orbital is also a pioneering operator of satellite-based networks that provide data communications, high-resolution
imagery and automotive information services to customers all around the world.