GALILEO SUCCEEDS IN HISTORIC FLYBY OF JUPITER’S VOLCANIC MOON

NASA’s Galileo spacecraft has successfully zipped past
Jupiter’s moon Io, the most volcanic body in our solar system.

Instruments onboard the spacecraft peered down at Io from an
altitude of only 611 kilometers (380 miles) at 10:06 p.m. Pacific
Daylight Time on Sunday. This was the closest look at Io by any
spacecraft, and Galileo’s cameras were poised to capture the
brief encounter.

If all goes as planned, the data will be transmitted to
Earth over the next several weeks and then will undergo
processing by mission scientists. New pictures would then be
released at a press briefing tentatively scheduled next month.

“We’re thrilled that the spacecraft handled this flyby so
well, particularly because it had to endure a strong dose of
radiation from Jupiter,” said Jim Erickson, Galileo project
manager at NASA’s Jet Propulsion Laboratory, Pasadena, CA. “It
appears at this point that everything went well.”

Because Io is the innermost of Jupiter’s moons, it lies in a
region with the highest levels of radiation from Jupiter, which
can wreak havoc with spacecraft instruments.

During this Io flyby, it appears the radiation did trigger
an error of the onboard computer’s memory, which put the
spacecraft in a “safe mode,” halting all non-essential activities
while awaiting further commands from the ground. That occurred
Sunday morning at 3:09 a.m Pacific time. Galileo engineers
scrambled to prepare new commands to help the spacecraft work
around the problem. The commands were transmitted to the
spacecraft late Sunday afternoon, they worked as hoped, and
Galileo resumed full operations at 8 p.m. Pacific time, just two
hours before the Io flyby.

“It was a heroic effort to pull this off, “Erickson said.
“The team diagnosed and corrected a problem we’d never come
across before, and they put things back on track.”

“We look forward to seeing the closest-ever pictures of Io,”
said Dr. Duane Bindschadler, Galileo manager of science
operations and planning. “We want to learn more about the
differences and similarities between volcanoes on Io and
volcanoes on Earth.” During the flyby, Galileo’s science
instruments studied the surface chemistry, heat, gravity and
magnetic properties of Io.

The flyby took place while Galileo was 598 million
kilometers (372 million miles) from Earth. A second, closer
flyby of Io by Galileo is planned for the evening of November 25
Pacific time (November 26 Eastern time) at an altitude of 300
kilometers (186 miles).

Additional information about the Galileo mission is
available on the Galileo home page at a new web address of
http://galileo.jpl.nasa.gov.

JPL manages the Galileo mission for NASA’s Office of Space
Science, Washington, D.C. JPL is operated for NASA by the
California Institute of Technology, Pasadena, CA.