Galileo Millennium Mission Status 12-28-2000

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
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NASA’s Galileo spacecraft has successfully flown past
Jupiter’s moon Ganymede, the largest moon in the solar system,
while Ganymede was eclipsed in Jupiter’s shadow.

Engineers at JPL said that Galileo dipped within 2,337
kilometers (1,452 miles) of the surface at 12:25 a.m. PST
today. A passage during Ganymede’s eclipse was planned in
order to observe auroral glows in that moon’s thin atmosphere.

“It looks like a nice, calm flyby,” said Jim Erickson,
Galileo project manager at NASA’s Jet Propulsion Laboratory,
Pasadena, Calif. “The team was prepared for problems, but
we’re happy without any. And we’ll be even happier once we’ve
passed this orbit’s closest approach to Jupiter.”

Intense radiation near Jupiter poses a risk to the
spacecraft’s electronics. Galileo’s closest approach to
Jupiter on this orbit will come at 7:26 p.m. PST tonight.
Information about the status of the spacecraft at that point
should be received on the ground about 35 minutes later, via
radio signals traveling at the speed of light. The last time
Galileo passed close to Jupiter was in May 2000.

Galileo has already received three times the cumulative
radiation exposure it was designed to withstand and has
continued making valuable scientific observations more than
three years after its original two-year mission in orbit
around Jupiter.

At 1 a.m. today, mission controllers at JPL received the
signals indicating that the Ganymede flyby had taken place.
The signals had been relayed from the Goldstone, Calif., and
Madrid, Spain, stations of NASA’s Deep Space Network, which
operates large dish antennas around the world for
communications with spacecraft.

Galileo’s camera and other instruments were set to
capture the flyby with images and other observations. If all
goes as planned, the data will be transmitted to Earth over
the next five months for processing and analysis.

As of 9 a.m. today, the spacecraft had recorded 31
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. 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.

Gases in portions of Ganymede’s thin atmosphere give off
a shimmering auroral glow as they are struck by electrons from
Jupiter’s radiation belts. The phenomenon is similar to
Earth’s Northern Lights and to what happens inside a
fluorescent light bulb. Sunlight washes out the glow, so
Galileo scientists took advantage of the eclipse to study the
glow for information about the chemical makeup of the gases
and the structure of Ganymede’s magnetic field, which affects
the location of the glow.

Ganymede is the largest moon in the solar system, larger
than the planets Mercury and Pluto. It is also the only moon
known to have its own internally generated magnetic field.
Earlier this month, scientists announced evidence that
Ganymede may have a thick layer of melted, salty water under
its ice-rich surface.

“Ganymede is certainly one of the most interesting places
in the solar system, and we’re looking forward to see what
kind of new surprises Galileo may have to tell us about it,”
Erickson said.

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.

[NOTE TO BROADCASTERS: A video file with animation to
accompany this status report will air today on NASA Television
at 3 p.m., 6 p.m. and 9 p.m. Eastern Standard Time. NASA
Television is broadcast on GE-2, transponder 9C, C-Band,
located at 85 degrees West longitude.
The frequency is 3880.0 MHz. Polarization is vertical and
audio is monaural at 6.8 MHz. For general questions about the
NASA Video File, contact: Fred Brown, NASA Television,
Washington, D.C. (202) 358- 0713.]