MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
Contact: Jane Platt
FOR IMMEDIATE RELEASE
October 8. 1999
GALILEO SPACECRAFT HAS HOT DATE WITH VOLCANIC MOON
NASA's Galileo spacecraft is gearing up for a daring
rendezvous with Jupiter's moon Io (pronounced EYE-oh), the most
volcanic body in our solar system, on Sunday night, Oct. 10
Galileo will swoop down to within 612 kilometers (380 miles)
of Io's fiery surface at 10:06 p.m. PDT (1:06 a.m. Oct. 11 EDT),
snapping the closest-ever pictures of this intriguing celestial
"Io is a natural laboratory for volcanoes," said Dr. Duane
Bindschadler, Galileo manager of science operations and planning.
"By studying Io close up, we'll learn more about how and when
volcanoes erupt and why they act the way they do. This may even
help us predict the behavior of volcanoes on Earth."
During the flyby, Galileo's science instruments will study
the chemistry, heat distribution, gravity and magnetic properties
of Io. For scientists, this thrilling encounter promises to
yield a bonanza of pictures and information, but for Galileo
engineers, the flyby presents a serious challenge with uncertain
results. Io's orbit lies in a region of intense radiation from
Jupiter's radiation belts, which could affect the performance of
spacecraft systems or even knock out various spacecraft
instruments. A mere fraction of the dose that Galileo will
receive would be fatal to a human.
"We expect that the spacecraft will survive the flyby,
although the radiation may cause its computers to reset or may
even cause irreversible damage to critical electronic
components," said Wayne Sible, Galileo deputy project manager.
"There is a possibility, if enough damage is done to the
electronics, it won't survive the flyby. Because of this
possibility, we planned the Io encounters for the end of the two-
year extended mission. After orbiting Jupiter for nearly four
years, the spacecraft has more than fulfilled its mission
objectives, so it seems reasonable to take a calculated risk for
a much closer look at such a scientifically rich target."
Galileo was originally assigned to spend two years studying
Jupiter, its moons and its magnetic environment. When that
original mission ended in December 1997, it was followed by a
two-year extended mission, scheduled to end in January 2000.
While spending the past four years near Jupiter, Galileo has been
exposed to radiation on an ongoing basis, which has caused some
of its instruments to act up.
To prepare for any possible harm caused by radiation during
the Io flyby, engineers have designed sophisticated software to
help the spacecraft weed out a true crisis from a minor glitch
caused by radiation and respond appropriately.
Galileo, the first spacecraft to orbit Jupiter, has
revolutionized our knowledge of Jupiter and its moons and has
provided thousands of colorful images. Data from Galileo support
the premise of a liquid ocean beneath the icy crust of Jupiter's
moon Europa, an intriguing prospect since water is a vital
ingredient for life. Thanks to information sent by Galileo,
scientists know much more about the weather on Jupiter and the
composition of its moons. En route to Jupiter, the spacecraft
took the first-ever close-up pictures of asteroids, when it
photographed Gaspra and Ida, and it returned historic images of
the destruction of comet Shoemaker-Levy 9 as its pieces slammed
If all goes well with the upcoming Io flyby, the spacecraft
will make an even more daring approach of Io on Nov. 25 (Pacific time) at an
altitude of only 300 kilometers (186 miles).
New Io images taken by the spacecraft are available at the
Additional information and pictures taken by the Galileo
spacecraft are available at the redesigned Galileo website at
this new Internet address:
Galileo was launched from the Space Shuttle Atlantis on Oct.
18, 1989. It entered orbit around Jupiter on Dec. 7, 1995. The
Jet Propulsion Laboratory (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.