Galileo Millennium Mission Status 18 Jan 2002

NASA’s Galileo spacecraft resumed gathering scientific
information at about 4:00 today Universal Time (8:00 p.m. Jan.
17 Pacific Time) after commands radioed from Earth took the
Jupiter orbiter out of the passive standby mode it entered on
Thursday.

Galileo passed within about 102 kilometers (63 miles) of
Jupiter’s moon Io on Thursday. Planned observations for the
remainder of the spacecraft’s current swing near Jupiter
include a series of images of the planet’s atmosphere, a
farewell color study of its icy moon Europa and navigational
imaging of the small moon Amalthea.

Galileo hit its target point for the Io flyby so
accurately that a scheduled post-encounter firing of thrusters
to fine-tune the trajectory was cancelled as unnecessary, said
Dr. Eilene Theilig, Galileo project manager at NASA’s Jet
Propulsion Laboratory, Pasadena, Calif. The close flyby was
calculated to use Io’s gravity to put Galileo on course for
its next encounters. Galileo will pass near Amalthea in
November 2002 and plunge to its demise in Jupiter’s crushing
atmosphere in September 2003.

"As expected, visiting Io has proved to be a challenging
and risky endeavor," Theilig said. "It’s disappointing not to
get the observations of Io that were planned for this
encounter, but I am very proud of the flight team that has
kept Galileo functioning in orbit more than three times longer
than originally planned and revived it once more yesterday."

Galileo detected a computer reset and placed itself in a
standby or "safe" mode Thursday at 13:41 Universal Time (5:41
PacificTime), about half an hour before its closest approach
to Io. The reset was apparently caused by exposure to the
intense radiation environment at Io’s distance from Jupiter.
Since the spacecraft began orbiting Jupiter in 1995, it has
endured a cumulative radiation exposure about three-and-a-half
times what it was originally designed to withstand.

NASA has repeatedly extended Galileo’s original two-year
mission in orbit. The spacecraft is now nearly out of the
hydrazine propellant needed to keep its antenna pointed toward
Earth. Knowing they would eventually lose contact and control
of the spacecraft, the Galileo team chose the planned impact
with Jupiter to ensure there was no chance the spacecraft
might hit Europa. One of Galileo’s important discoveries has
been the likelihood of a melted saltwater ocean under Europa’s
icy crust, making that moon of great interest for future study
of the possibility of extraterrestrial life.

Additional information about the Galileo mission is
available at http://galileo.jpl.nasa.gov .

Galileo was launched from the Space Shuttle Atlantis on Oct.
18, 1989. After a long journey to Jupiter, Galileo began
orbiting the huge planet on Dec. 7, 1995, and successfully
completed its two-year primary mission in 1997. That has been
followed by three mission extensions. 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.