Illustration of Galileo at Jupiter

NASA's Galileo spacecraft, on its way to Jupiter via gravity-assist encounters with Venus and the Earth, performed its second trajectory correction maneuver Friday, Dec. 22.

"The maneuver went off exactly as planned," said mission director Neal Ausman at the Jet Propulsion Laboratory, where the Galileo mission and spacecraft were designed and built and are now being operated. "We're analyzing spacecraft tracking and telemetry data now to determine exactly how close the maneuver has placed Galileo to the desired aim point."

Galileo's first maneuver, completed in November, removed most of the intentional offset placed in the flight path during the Oct. 18 launch. Friday's maneuver took out the rest of this offset and corrected small statistical errors in the first maneuver.

The spacecraft velocity changed by 0.74 meter per second (roughly 1/20 that of the first maneuver), mostly at right angles to the Sun line, moving the Venus closest approach to about 10,000 miles from planet center or about 6,200 miles above the cloud tops. Closest approach will occur about 10 p.m. PST on Feb. 9, 1990.

Because the spacecraft is spinning at 3.15 rpm and because it uses tiny thrusters for the maneuver, this trajectory change required 218 small pulses of thrust during 2-hour period.

One more maneuver is scheduled for late January, if needed to fine-tune the trajectory for the Feb. 9, 1990, Venus encounter.

Today the Galileo mission team begins comprehensive 4-day checkout of all the Orbiter science instruments to be used to observe Venus, the Earth and Moon, an asteroid and, in 1995-97, the giant planet Jupiter and its system. Galileo's Probe was checked out shortly after launch and will be rechecked at later date.

Only two instruments have been turned on up to now, the magnetometer and the heavy ion counter. They observed the great solar flare last October.

As of today the Galileo spacecraft is 12.5 million miles, or 67 light-seconds, from Earth. It has gone almost 105 million miles along its 185-million-mile path to Venus; Jupiter lies 2.3 billion miles and almost six years ahead.

The Galileo project is managed by the Caltech Jet Propulsion Laboratory for NASA's Office of Space Science and Applications.

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