MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
Contacts: Guy Webster, JPL (818) 354-6278
FOR IMMEDIATE RELEASE
March 15, 2001
GALILEO GETS ONE LAST FREQUENT-FLYER UPGRADE
The resilient Galileo spacecraft doesn't know when to
call it quits. So, NASA has outlined the details of one last
mission extension, which includes five more flybys of the
Jovian moons before a final plunge into the crushing pressure
of the giant planet's atmosphere.
Galileo has been orbiting Jupiter for more than five
years and survived radiation exposure more than three times
what it was built to withstand. Galileo's mission has
previously been extended twice and during that time it has
returned an enormous wealth of scientific information,
including evidence of a sub-surface ocean on Jupiter's moon
"We're proud that this workhorse of a spacecraft has kept
performing well enough that we can ask it to keep serving
science a little longer," said Dr. Jay Bergstralh, acting
director of solar system exploration at NASA Headquarters,
On May 25, Galileo should pass about 123 kilometers (76
miles) above the moon Callisto, the second largest of
Jupiter's 28 known moons. The effects of Callisto's gravity
will set up the space probe for a swing over both polar
regions of the intensely volcanic moon Io in August and
Galileo will take pictures, measure magnetic forces, and
study dust and smaller particles. Science goals include
studying the extent of volcanism on Io, both in new and
previously active sites; determining whether Io generates its
own weak magnetic field; and gaining a better understanding of
a doughnut-shaped ring, the so-called Io torus, that encircles
Jupiter and contains electrically charged gases.
In 2002, having completed its imaging mission, Galileo
will continue studies of Jupiter's massive magnetic field with
seven instruments. In January, the orbiter will fly near the
equator of Io.
In November, it will swing closer to Jupiter than ever
before, dipping within about 500 kilometers (about 300 miles)
of the moon Amalthea, which is less than one-tenth the size of
Io and less than half as far from Jupiter. Scientists will use
Galileo measurements to determine the mass and density of
Amalthea. They will also study dust particles as Galileo flies
through Jupiter's gossamer rings and seek new details of the
magnetic forces and the densities of charged particles close
to the planet.
Galileo's final orbit will take an elongated loop away
from Jupiter. Then in August 2003, the spacecraft will head
back for a direct impact and burn up as it plows into
Jupiter's 60,000-kilometer-thick atmosphere. This final act
was recommended by the National Research Council of the
National Academy of Sciences last June.
Galileo has already succeeded beyond expectations, and we
have the opportunity to learn still more in coming months, but
it is sad to see the end of the road up ahead," said Eilene
Theilig, Galileo project manager at NASA's Jet Propulsion
Laboratory, Pasadena, Calif. "Exposure from Jupiter's intense
radiation belts has impaired some of Galileo's instruments,
but it is still producing valuable scientific results."
The science program for the Galileo mission extension,
which will cost $9 million, was recommended to NASA by a blue-
ribbon panel of planetary scientists that met last July. "This
mission extension accomplishes the highest priorities of the
review panel in a cost effective way," said Paul Hertz,
Galileo program executive at NASA Headquarters.
Galileo was launched Oct. 18, 1989, aboard NASA's Space
Shuttle Atlantis. On Dec. 7, 1995, a probe released earlier
from Galileo made measurements while dropping through
Jupiter's upper atmosphere. Galileo's top scientific
- Produced strong evidence that Europa has a melted saltwater
ocean under the ice layer on its surface. The spacecraft has
also found indications that Ganymede and Callisto also have
layers of liquid saltwater.
- Detailed the varied and extensive volcanic processes on Io,
catching plumes erupting, fire fountains in process and lava
flows expanding, among other observations.
- Delivered a probe that made the first measurements of
Jupiter's atmosphere from within the atmosphere.
- Made the first close approach to an asteroid and made the
first discovery of a satellite orbiting an asteroid.
- Discovered the first internal magnetic field of a moon.
Ganymede's intrinsic magnetic field actually creates a "mini-
magnetosphere" embedded within Jupiter's vast magnetosphere.
- Provided the only direct observation of Comet Shoemaker-
Levy's impact into Jupiter.
JPL, a division of the California Institute of Technology
in Pasadena, manages Galileo for NASA's Office of Space
Science, Washington, D.C.
More information about Galileo is available on the
Internet at http://galileo.jpl.nasa.gov/ .