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Contact: Jane Platt (818) 354-0880

FOR IMMEDIATE RELEASE October 11, 1999

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.

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10/11/99 JP
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