Galileo Millennium Status 29 Dec 2000
NASA’s Galileo spacecraft has passed through the highest
radiation environment it will experience in its current orbit of
Jupiter, flying within about 500,000 kilometers (310,000 miles)
of the giant planet’s cloud tops at 7:26 p.m. PST Thursday, Dec.
28.
Exposure to Jupiter’s intense radiation caused two effects –
– an alarm received from Galileo’s camera system, and a computer
reset of the non-spinning portion of the spacecraft. The reset
was a transient event that has happened during radiation
exposures on several previous orbits. The computer reset was
handled properly by onboard software responses, and mission
engineers are investigating the out-of-the-ordinary measurement
that triggered the camera alarm.
Other systems on Galileo were operating normally more than
12 hours after the closest approach to Jupiter.
“Adverse effects from the radiation close to Jupiter are not
unexpected,” said Jim Erickson, Galileo project manager at NASA’s
Jet Propulsion Laboratory, Pasadena, Calif. Galileo had already
endured more than three times the cumulative radiation exposure
it was designed to withstand, and has operated more than three
years above and beyond its original two-year mission in orbit
around Jupiter.
Galileo had flown within 2,337 kilometers (1,452 miles) of
Jupiter’s largest moon, Ganymede, and taken images of it several
hours before the camera began indicating a possible problem. The
camera and other scientific instruments onboard the orbiter are
continuing to record data about Jupiter and its moons.
“Images from the camera are still being recorded,” Erickson
said. “Until the first of those images are transmitted to Earth
in February, we may not know whether this is a situation that is
impairing the images.”
As of 9 a.m. PST today, the spacecraft had recorded 46
percent of the scientific data that its instruments had been
programmed to collect during this swing through the inner
portion of the Jovian system, from Dec. 26 through Dec. 31.
Besides studying Ganymede, Galileo is making more distant
observations this week of Jupiter and the moons Io, Callisto
and Europa. If all goes as planned, the data will be
transmitted to Earth over the next five months for processing
and analysis. Some of the observations are planned as part of
collaborative studies with NASA’s Cassini spacecraft, which
will pass Jupiter on Saturday, though at a much greater
distance than Galileo is from the planet this week.
Additional information about the Galileo mission is
available at http://galileo.jpl.nasa.gov .
Galileo was launched from NASA’s Space Shuttle Atlantis
on Oct. 18, 1989. It began orbiting Jupiter on Dec. 7, 1995.
JPL, a division of the California Institute of Technology in
Pasadena, manages the Galileo mission for NASA’s Office of Space
Science, Washington, D.C.
