Galileo has successful flyby of Ganymede during eclipse
Posted: December 29, 2000
"It looks like a nice, calm flyby," said Jim Erickson, Galileo project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The team was prepared for problems, but we're happy without any. And we'll be even happier once we've passed this orbit's closest approach to Jupiter."
Intense radiation near Jupiter poses a risk to the spacecraft's electronics. Galileo's closest approach to Jupiter on this orbit came today at 0326 GMT (10:26 p.m. EST Thursday).
Galileo has already received three times the cumulative radiation exposure it was designed to withstand and has continued making valuable scientific observations more than three years after its original two-year mission in orbit around Jupiter.
At 0900 GMT (4 a.m. EST), mission controllers received the signals indicating that the Ganymede flyby had taken place. The signals had been relayed from the Goldstone, Calif., and Madrid, Spain, stations of NASA's Deep Space Network, which operates large dish antennas around the world for communications with spacecraft.
Galileo's camera and other instruments were set to capture the flyby with images and other observations. If all goes as planned, the data will be transmitted to Earth over the next five months for processing and analysis.
Gases in portions of Ganymede's thin atmosphere give off a shimmering auroral glow as they are struck by electrons from Jupiter's radiation belts. The phenomenon is similar to Earth's Northern Lights and to what happens inside a fluorescent light bulb. Sunlight washes out the glow, so Galileo scientists took advantage of the eclipse to study the glow for information about the chemical makeup of the gases and the structure of Ganymede's magnetic field, which affects the location of the glow.
Ganymede is the largest moon in the solar system, larger than the planets Mercury and Pluto. It is also the only moon known to have its own internally generated magnetic field. Earlier this month, scientists announced evidence that Ganymede may have a thick layer of melted, salty water under its ice-rich surface.
"Ganymede is certainly one of the most interesting places in the solar system, and we're looking forward to see what kind of new surprises Galileo may have to tell us about it," Erickson said.
Galileo was launched from NASA's Space Shuttle Atlantis on Oct. 18, 1989. It began orbiting Jupiter on Dec. 7, 1995.
NASA animation shows the Galileo space probe making a close flyby of Jupiter's moon Ganymede. The moon is in eclipse by the giant gas planet during Galileo's encounter.
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With the sun behind us, this animation clips shows Ganymede slipping into the eclipse, which makes its auroral glow visible as Galileo passes closest to the moon.
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