Galileo's flight team today is commanding the spacecraft for the third in a planned series of trajectory correction maneuvers since the Venus flyby last February.
The maneuver, starting Tuesday at 11 a.m. PDT, will refine Galileo's flight path for this December's flyby of Earth.
Venus and Earth are providing gravity assists to enable the NASA spacecraft to reach Jupiter in 1995 for a detailed, two-year study of the giant planet's atmosphere, satellites, and magnetosphere. Two Earth flybys are scheduled, the second in December 1992.
As it did at Venus, Galileo will make scientific observations of Earth as it passes by.
Taking a gravity assist from a planet requires precise navigation, since any error in the approach would be magnified on the way out. Flight engineers at the Jet Propulsion Laboratory plan to shape Galileo's course with a total of six rocket-thrust maneuvers on the way to the first Earth flyby.
The spinning spacecraft will pulse its axial thrusters 228 times (pushing the craft towards the Sun) and then deliver 160 pulses from the lateral thrusters (nearly at right angles to the Sun line), during a period of nearly three hours. This will change Galileo's velocity by 0.92 meters per second or 2 mph. Additional maneuvers this October and November will fine-tune the flight path for the Earth gravity assist needed.
The Galileo project is managed by the Jet Propulsion Laboratory, California Institute of Technology, for NASA's Office of Space Science and Applications.
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