Galileo survives volcanic flyby

NASA spacecraft completes the first of two historic flybys of Jupiter's moon Io

October 11, 1999: 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.

Right: Artist's concept of Galileo swooping over the surface of Io. [click for animation].

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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.

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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.

Visit IoFlyBy.com for coverage of Galileo's close encounters with Io, including science news and the latest images of Jupiter's volcanic moon.

"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.

Related Stories:

Sulfuric Acid Discovered on Europa -- September 30, 1999. Sulfur from Io's fiery volcanoes may be responsible for a battery acid chemical on Europa with implications for astrobiology.

Io or Bust -- September 16, 1999. Galileo braves extreme radiation as it plunges toward a close encounter with Io's volcanoes.

Divining Water on Europa -- September 9, 1999. As circumstantial evidence for an underground ocean mounts, JPL scientists try an ingenious experiment to look for hexagonal ice crystals on the surface of Europa.

Taking the Scenic Route to Io -- June 30, 1999. What's happening to the small craters on Callisto? That's the mystery scientists were contemplating as Galileo zoomed past Jupiter's pockmarked moon this morning in an orbit-changing maneuver designed to bring the spacecraft closer to volcanic Io.

Turn Left at Callisto -- May 5, 1999. Galileo heads for a daring encounter with Io's volcanoes.

Galileo buzzes Europa -- Feb. 2, 1999. Galileo executes a close flyby of Europa for the last time during the current mission.

The Frosty Plains of Europa -- Dec. 3, 1998. As Galileo returns new images of Europa, NASA scientists prepare to study samples from a potentially similar environment here on Earth.

Callisto makes a big splash -- Oct. 22, 1998. Scientists may have discovered a salty ocean and a possible ingredient for life on Jupiter's moon.

Galileo takes a close look at icy Europa -- Oct 2, 1998. The spacecraft flew within 2300 miles of the mysterious satellite last weekend.

Clues to possible life on Europa may lie buried in Antarctic ice -- Mar. 5, 1998. Exotic microbial forms turn up in ice above Antarctica's Lake Vostok.

Related Sites:

Ice, Water and Fire the Galileo Europa Mission

Galileo home page at JPL, with the latest on Europa, Callisto and Io

Jet Propulsion Laboratory home page

Io from the SEDS Nine Planets web site

Callisto from the SEDS Nine Planets web site

Jupiter from the SEDS Nine Planets web site

Io: The Prometheus Plume Aug. 18, 1997 Astronomy Picture of the Day

Close-up of an Io volcano Aug. 4, 1995 Astronomy Picture of the Day

Sizzling Io July 6, 1998 Astronomy Picture of the Day

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