Illustration of Galileo at Jupiter

NASA's Galileo spacecraft will turn and fire its small on-board thrusters Tuesday, July 2, to set its course for an encounter with the asteroid Gaspra in October.

Acting on computer commands sent to it by engineers at the Jet Propulsion Laboratory, the 2-1/2-ton spacecraft will begin its maneuver about 8:20 a.m. Pacific Daylight Time Tuesday.

The maneuver will alter Galileo's velocity in space by about 3.6 meters per second (about 8 miles per hour), slowing it slightly and adjusting the flyby distance at Gaspra on October 29 to 1,600 kilometers (1,000 miles).

The October event will be the first flyby of an asteroid. Gaspra, about 11 miles long, orbits roughly 200 million miles from the sun near the inner edge of the asteroid belt. Scientists believe it is a fairly typical small, rocky main-belt asteroid.

Galileo is en route to the giant planet Jupiter, where it will go into orbit in December 1995 after sending a probe into Jupiter's atmosphere. Following an October 1989 launch, the spacecraft flew by Venus and the Earth in 1990 in gravity-assist passes to increase its velocity. One more Earth gravity assist is planned in December 1992 to pick up the last increment of velocity necessary to reach Jupiter.

The Galileo mission is managed for NASA's Office of Space Science and Applications by JPL.

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