The Galileo spacecraft, scheduled to go into orbit around Jupiter in December 1995, is within 2 million miles and four days of the second of three planetary gravity assists designed to get it there.
At this gravity-assist flyby of Earth, as at Venus in February 1990, Galileo is making use of the opportunity to conduct limited scientific observations of the planet.
Following a successful trim maneuver November 28, 1990, it is precisely on course for the December 8 Earth gravity assist.
Galileo will have a closest-approach altitude of about 590 miles and gain approximately 11,500 mph of heliocentric speed from the gravity assist. This enlarges its orbit so that it reaches the asteroid belt and returns to Earth in 2 years for the final gravity assist, which in turn will add another 8,300 mph of speed and pump the orbit up to reach Jupiter in December 1995.
Health and performance of the spacecraft continue to be excellent.
The data acquired at Venus during the February gravity assist there were successfully played back November 19-21, 1990, after some 9 months in storage, and processing and analysis began. The observations include 81 images of the clouds; two infrared maps of lower-level clouds some 3033 miles above surface and 6-10 miles below the visible cloudtops; and other atmospheric and plasma measurements.
Preliminary analysis indicates new information concerning the atmospheric circulation of Venus. The new lower-level cloud maps, showing the night side, indicated strong equatorial convection, while temperate-zone clouds showed East-West elongation by winds estimated at 150 mph.
Scientific observations of the Earth will not be constrained by tape-recorder capacity. Between 1,000 and 2,000 images, and correspondingly expanded observations by other instruments, are planned.
Following the first Earth gravity assist, the first close flyby of an asteroid is planned for October 29, 1991, with the asteroid Gaspra.
The Galileo Project is managed and operated for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory. The atmospheric probe is provided by NASA Ames Research Center. The scientific activities are being carried out by more than 100 scientists from 6 nations.
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