MEDIA RELATIONS OFFICE|
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Galileo Millennium Mission Status
October 12, 2001
NASA's durable Galileo spacecraft will skim close to the
south pole of Jupiter's moon Io next week in search of new
insight about that moon's volcanic surface and molten interior.
The flyby at 0123 Universal Time on Oct. 16 (6:23 p.m. Oct.
15, Pacific Daylight Time), is taking the Jupiter-orbiting
spacecraft back inside the hazardous environment of Jupiter's
intense radiation belts. Io is the innermost of the giant
planet's four major moons.
An engine burn to fine-tune the trajectory on Oct. 13 is
planned to send Galileo about 181 kilometers (112 miles) above
Io's surface. This would be Galileo's closest approach to Io so
far. The spacecraft has made five previous swings near Io since
it reached Jupiter's neighborhood in 1995.
"Io is always changing, so we're eager to learn what Galileo
might show us this time," said Dr. Eilene Theilig, project
manager for Galileo at NASA's Jet Propulsion Laboratory,
Pasadena, Calif. "Maybe it will surprise us as much as it did in
the last flyby." When Galileo flew near Io's north pole in early
August, scientists were watching for a gassy plume that a volcano
named Tvashtar had been spraying seven months earlier. Instead,
Galileo found an even taller eruption from a site where there
hadn't even been a volcano before, she said.
The polar routes were chosen to position the spacecraft for
magnetic field measurements that can provide hints about the
moon's interior. The flight path will also provide good
opportunities for studying several of Io's interesting volcanic
features, including a recently discovered hot spot in the far
south and Loki, the most powerful volcano in the solar system.
While the spacecraft travels through the inner portion of the
Jupiter system in the days surrounding the Io flyby, scientists
will also be using Galileo's instruments to examine changes and
details in clouds on Jupiter itself and to measure the radiation
belts created by Jupiter's magnetic field.
Yesterday, the Galileo team sent the spacecraft its
detailed instructions for the encounter. The sequence of commands
was transmitted from JPL's Deep Space Network facility near
Madrid, Spain, one of three network sites worldwide with dish
antennas 70 meters (230 feet) across that are used for
communicating with Galileo.
Earlier, engineers sent new software to the spacecraft's
camera, designed to lessen chances for a repeat of radiation-
induced malfunctioning that has affected the camera on several
occasions since the middle of last year.
Electronic components in the camera and elsewhere in the
spacecraft have been degraded by repeated exposure to energetic-
particle radiation near Jupiter. Galileo has endured more than
three times the cumulative dose of radiation it was designed to
tolerate. It has performed in orbit nearly three times as long as
its original two-year mission.
Galileo is running low on the propellant it uses both for
tweaking its trajectory and for adjusting its orientation to
point its antenna. After one last flyby of Io in January 2002,
the spacecraft will be on a trajectory that will take it through
Jupiter's inner radiation belt and near the small inner moon
Amalthea in November 2002, then out for one more long loop ending
with a plunge into the crushing pressure of Jupiter's atmosphere
in September 2003.
Additional information about Galileo, Io and Jupiter is
available online at http://galileo.jpl.nasa.gov . JPL, a
division of the California Institute of Technology in Pasadena,
manages the Galileo mission for NASA's Office of Space Science,