The launch window for the WIRE mission extends from 6:51 p.m. to 7:01 p.m. (PST), with a targeted launch time of 6:57 p.m. (PST). This revised schedule remains subject to the completion of final pre-launch testing and acceptable weather conditions at launch time.

The mission sequence is expected to take approximately nine minutes, from the time the Pegasus rocket is released from its L-1011 carrier aircraft, about 100 miles off the California coast, to the time that the satellite is deployed into orbit from the rocket's final stage. Orbital plans to launch the WIRE satellite into a circular orbit 340 miles (or 540 kilometers) above the Earth, inclined at 97.5 degrees to the equator.

NASA's 561-pound (or 254-kilogram) WIRE satellite is a part of the space agency's Small Explorer (SMEX) series of lightweight spacecraft designed to carry out cost-effective scientific missions. The purpose of the four-month WIRE mission is to study the formation and evolution of ``starburst'' galaxies to help astrophysicists gain a better understanding of the structure and evolution of the early universe.

The WIRE mission will originate from Vandenberg Air Force Base (VAFB), California and will be the first Pegasus mission of 1999 following two consecutive years of flawless performance.

Over the past two years, the Pegasus rocket has successfully deployed a total of 33 satellites, including 24 for Orbital's ORBCOMM Global data communications affiliate, in 11 consecutive successful missions.