Galileo End of Mission Status

[Ulrich Rieth]

NASA News (http://www.jpl.nasa.gov)

Carolina Martinez (818) 354-9382
Jet Propulsion Laboratory, Pasadena, Calif.

News Release: 2003-129
September 21, 2003

Galileo End of Mission Status

The Galileo spacecraft's 14-year odyssey came to an end on Sunday, Sept.
21, when the spacecraft passed into Jupiter's shadow then disintegrated
in the planet's dense atmosphere at 11:57 a.m. Pacific Daylight Time.
The Deep Space Network tracking station in Goldstone, Calif., received
the last signal at 12:43:14 PDT. The delay is due to the time it takes
for the signal to travel to Earth.

Hundreds of former Galileo project members and their families were
present at NASA's Jet Propulsion Laboratory in Pasadena, Calif., for a
celebration to bid the spacecraft goodbye.

"We learned mind-boggling things. This mission was worth its weight in
gold," said Dr. Claudia Alexander, Galileo project manager.

Having traveled approximately 4.6 billion kilometers (about 2.8 billion
miles), the hardy spacecraft endured more than four times the cumulative
dose of harmful jovian radiation it was designed to withstand. During a
previous flyby of the moon Amalthea in November 2002, flashes of light
were seen by the star scanner that indicated the presence of rocky
debris circling Jupiter in the vicinity of the small moon. Another
measurement of this area was taken today during Galileo's final pass.
Further analysis may help confirm or constrain the existence of a ring
at Amalthea's orbit.

"We haven't lost a spacecraft, we've gained a steppingstone into the
future of space exploration," said Dr. Torrance Johnson, Galileo project
scientist.

The spacecraft was purposely put on a collision course with Jupiter
because the onboard propellant was nearly depleted and to eliminate any
chance of an unwanted impact between the spacecraft and Jupiter's moon
Europa, which Galileo discovered is likely to have a subsurface ocean.
Without propellant, the spacecraft would not be able to point its
antenna toward Earth or adjust its trajectory, so controlling the
spacecraft would no longer be possible. The possibility of life existing
on Europa is so compelling and has raised so many unanswered questions
that it is prompting plans for future spacecraft to return to the icy
moon.

Galileo was launched from the cargo bay of Space Shuttle Atlantis in
1989. The exciting list of discoveries started even before Galileo got
a glimpse of Jupiter. As it crossed the asteroid belt in October 1991,
Galileo snapped images of Gaspra, returning the first ever close-up
image of an asteroid. Less then a year later, the spacecraft got up
close to yet another asteroid, Ida, revealing it had its own little
"moon," Dactyl, the first known moon of an asteroid. In 1994 the
spacecraft made the only direct observation of a comet impacting a
planet-- comet Shoemaker-Levy 9's collision with Jupiter.

The descent probe made the first in-place studies of the planet's clouds
and winds, and it furthered scientists' understanding of how Jupiter
evolved. The probe also made composition measurements designed to assess
the degree of evolution of Jupiter compared to the Sun.

Galileo made the first observation of ammonia clouds in another planet's
atmosphere. It also observed numerous large thunderstorms on Jupiter
many times larger than those on Earth, with lightning strikes up to
1,000 times more powerful than on Earth. It was the first spacecraft to
dwell in a giant planet's magnetosphere long enough to identify its
global structure and to investigate the dynamics of Jupiter's magnetic
field. Galileo determined that Jupiter's ring system is formed by dust
kicked up as interplanetary meteoroids smash into the planet's four
small inner moons. Galileo data showed that Jupiter's outermost ring is
actually two rings, one embedded within the other.

Galileo extensively investigated the geologic diversity of Jupiter's
four largest moons: Ganymede, Callisto, Io and Europa. Galileo found
that Io's extensive volcanic activity is 100 times greater than that
found on Earth. The moon Europa, Galileo unveiled, could be hiding a
salty ocean up to 100 kilometers (62 miles) deep underneath its frozen
surface containing about twice as much water as all the Earth's oceans.
Data also showed Ganymede and Callisto may have a liquid-saltwater
layer. The biggest discovery surrounding Ganymede was the presence of a
magnetic field. No other moon of any planet is known to have one.

The prime mission ended six years ago, after two years of orbiting
Jupiter. NASA extended the mission three times to continue taking
advantage of Galileo's unique capabilities for accomplishing valuable
science. The mission was possible because it drew its power from two
long-lasting radioisotope thermoelectric generators provided by the
Department of Energy.

"The mission was a testimonial to the persistence of NASA even through
tremendous challenges. It was a phenomenal mission," said Sean O'Keefe,
NASA administrator.

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. JPL designed and built the Galileo orbiter, and
operated the mission.

Additional information about the Galileo mission and its discoveries is
available online at:
http://www.jpl.nasa.gov/galileo-legacy
and
http://galileo.jpl.nasa.gov

For information about NASA, visit: http://www.nasa.gov