Set to Launch Taurus Rocket on December 20

(Dulles, VA 17 December 1999) — Orbital Sciences Corporation (NYSE: ORB) announced today that it is in final preparations to launch its next Taurus^® rocket, which will carry two scientific satellites and a small secondary commercial payload into orbit, on Monday, December 20. The available launch window extends from 11:11 to 11:24 p.m. (PST), with a targeted launch time of 11:15 p.m. This schedule is subject to final preparations and testing, as well as acceptable weather conditions at the Vandenberg Air Force Base, California launch site at the time of the mission.

On board Orbital’s four-stage ground-launch rocket will be the Korea Multi-Purpose Satellite (KOMPSAT) that is being launched for the Korean Aerospace Research Institute (KARI), and the Active Cavity Irradiance Monitor Satellite (ACRIMSAT) that is being launched for NASA’s Jet Propulsion Laboratory. In addition, the Taurus rocket will carry a small payload for Celestis, Inc., which will not separate from the rocket’s final stage once it reaches orbit.

On launch day, the Taurus rocket will be prepared for its mission during a four-hour countdown procedure. Following a final launch decision, the vehicle will ignite its first stage rocket motor, lift off and follow a pre-programmed launch sequence controlled by its onboard flight computer. Approximately 13 minutes after liftoff, Taurus will deliver the KOMPSAT spacecraft into a Sun-synchronous orbit approximately 420 miles (685 kilometers) above the Earth. About one minute later, Taurus will deploy the ACRIMSAT satellite into a similar orbit.

The Taurus Launch System
Orbital developed the ground-launched Taurus vehicle to provide a cost-effective, reliable means of launching satellites weighing up to 3,000 pounds into low-Earth orbit, or up to 800 pounds into geosynchronous Earth orbit. Taurus incorporates advanced structural and avionics technology proven on Pegasus and other operational launch systems. It is also designed for easy transportability, offering customers rapid-response launches from a wide range of locations.

Including its debut flight in 1994, Orbital’s Taurus rocket has carried out three space missions, all of which have been successful. The most recent Taurus mission occurred in October 1998, when the rocket launched an experimental satellite for the U.S. National Reconnaissance Office.

The KOMPSAT Satellite
The KOMPSAT satellite’s scientific mission is designed to serve South Korea in several specific applications. The satellite carries three primary instruments, including an electro-optical camera for the production of digital elevation maps of Korea, an ocean scanning multispectral imaging instrument to study biological oceanography, and a space physics sensor that will study the effects of radiation on microelectronics and the characteristics of electrons in the ionosphere. Details about the KOMPSAT program can be found at http://kompsat.kari.re.kr/

The ACRIMSAT Satellite
Under a contract from NASA’s Jet Propulsion Laboratory, Orbital’s Space Systems Group designed and built the ACRIMSAT satellite at the company’s McLean, Virginia satellite manufacturing and testing facility. The scientific mission of the ACRIMSAT satellite is to measure the degree of variation in total radiant energy from the Sun over its five-year mission life. Detailed information about the ACRIM program can be found at http://acrim.jpl.nasa.gov/

About Orbital
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.

In addition, the following is a list of planned media events for the launch of Orbital’s Taurus rocket:

Photo/video opportunity, remote camera placement
Sunday, December 19, 1999
Time: 11:00 a.m. to 12:30 p.m.
Location: Visitor’s center parking lot at the main gate of Vandenberg Air Force Base, California

Media representatives should meet Vandenberg Air Force public affairs representatives at 11:00 a.m. in the parking lot of the main gate of Vandenberg Air Force Base to be transported to and from launch pad 576E, where photo, video and remote camera placement opportunities will be available.

Press briefing on the Taurus, KOMPSAT and ACRIMSAT mission
Monday, December 20, 1999
Time: 9:30 a.m. to 11:30 a.m.
Location: NASA Building 840

Representatives from Orbital Sciences Corporation, the Korean Aerospace Research Institute, TRW Corporation, NASA/Jet Propulsion Laboratory and VAFB’s 30th Weather Squadron will brief the media on the Taurus launch vehicle, the KOMPSAT satellite and its mission, the ACRIMSAT satellite and its mission, and the weather forecast for the launch.

One-on-one interview opportunities will be available following the briefing.

VAFB Public Affairs will meet members of the media at 9:30 a.m. at the South Gate parking lot and provide an escort to NASA Building 840.

Launch of Orbital’s Taurus rocket
Monday, December 20, 1999
Time: 10:15 p.m.
Location: Weather station observation area at VAFB

The available launch window for the Taurus mission extends from 11:11 p.m. to 11:24 p.m. (PST). Media wishing to view the launch in person should gather at 10:15 p.m. at the parking lot of the Visitor Control Center at the main gate where VAFB Public Affairs will provide an escort to the Weather Station viewing area.

All media wishing to attend any of the following events must register with the Office of Public Affairs at VAFB by calling (805) 606-3595.

Satellite broadcast
The launch of the Taurus rocket will be broadcast over the Tellstar 5 satellite, transponder #24 at 97 degrees. The downlink frequency is 4180 Mhz and horizontal. The audio channels are 6.2 (left) for Korean language commentary or 6.8 (right) for the English language countdown.