Galileo Millenium Mission Status 16 Oct 2001

NASA’s Galileo spacecraft successfully completed a close
flyby to study Jupiter’s moon Io at 0123 Universal Time today
(6:23 p.m. Oct. 15, Pacific Daylight Time), during the long-lived
spacecraft’s 32nd orbit around Jupiter.

Galileo passed closer to Io than ever before, within about
181 kilometers (112 miles) of ground level near Io’s south pole.

Engineers at NASA’s Jet Propulsion Laboratory in Pasadena,
Calif., said that signals confirming the spacecraft’s basic
health arrived within an hour after the flyby. The signals were
received via JPL’s Deep Space Network antenna facility near
Madrid, Spain.

“Jupiter’s radiation belts make flying near Io risky, but
Galileo has come through for us again,” said JPL’s Dr. Eilene
Theilig, Galileo project manager.

Galileo has been orbiting Jupiter since 1995. It has already
endured more than three times as much radiation as it was
designed to tolerate. NASA has extended Galileo’s original two-
year orbital mission three times to take advantage of the
spacecraft’s continuing ability to make scientific discoveries.

As of 1500 UT (8 a.m. PDT) today, the spacecraft had
recorded about 70 percent of the scientific data that its
instruments had been programmed to collect during this swing
through the inner portion of the Jovian system. The encounter
period that began Oct. 13 includes more-distant observations of
Jupiter and the moon Europa, as well as the close-up examination
of Io.

The images and other scientific data from the encounter will
be transmitted to Deep Space Network antennas in Spain, Australia
and California over the next three months.

Engineering data already received, such as voltage
readings, suggest that Galileo’s solid-state camera functioned
properly during the flyby. However, the camera’s performance
won’t be known for sure until transmission of the pictures,
which is due to begin in late October. The camera has
malfunctioned intermittently in the past year because
radiation has degraded its electronics. Galileo engineers sent
new software to the camera two weeks ago designed to minimize
chances for recurrence of the problem.

Among the high-priority science observations for the flyby
are magnetic-field measurements near Io’s south pole, useful for
understanding the moon’s interior and interactive processes
within Jupiter’s large magnetic environment. Other instruments
were scheduled to observe details and changes in several volcanic
areas on Io’s surface, including a new hot spot and plume
eruption discovered on the most recent flyby, in August.

Io is the most volcanically active world known. It orbits
closest to Jupiter of the planet’s four major moons. Tidal
stress from the gravitational pull of Jupiter and the outlying
moons heats Io’s interior and sustains the volcanism.

Additional information about Galileo and the discoveries it
has made since it was launched from NASA’s Space Shuttle Atlantis
in 1989 is available 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,
Washington, D.C.