September 17, 2003

Donald Savage 
Headquarters, Washington 
(Phone: 202/358-1547)

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

RELEASE: 03-297

GALILEO TO TASTE JUPITER BEFORE TAKING FINAL PLUNGE

In the end, the Galileo spacecraft will get a taste of Jupiter before 
taking a final plunge into the planet's crushing atmosphere, ending 
the mission on Sunday, Sept. 21. The team expects the spacecraft to 
transmit a few hours of science data in real time leading up to 
impact. 

The spacecraft has been purposely put on a collision course with 
Jupiter 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. The long-planned impact is 
necessary now that the onboard propellant is nearly depleted.

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. 

"It has been a fabulous mission for planetary science, and it is hard 
to see it come to an end," said Dr. Claudia Alexander, Galileo 
project manager at NASA's Jet Propulsion Laboratory, Pasadena, Calif. 
"After traversing almost 3 billion miles and being our watchful eyes 
and ears around Jupiter, we're keeping our fingers crossed that, even 
in its final hour, Galileo will still give us new information about 
Jupiter's environment."

Although scientists are hopeful to get every bit of data back for 
analysis, the likelihood of getting anything is unknown because the 
spacecraft has already endured more than four times the cumulative 
dose of harmful jovian radiation it was designed to withstand. The 
spacecraft will enter an especially high-radiation region again as it 
approaches Jupiter.

Launched in the cargo bay of Space Shuttle Atlantis in 1989, the 
mission has produced a string of discoveries while circling the solar 
system's largest planet, Jupiter, 34 times. Galileo was the first 
mission to measure Jupiter's atmosphere directly with a descent probe 
and the first to conduct long-term observations of the jovian system 
from orbit. 

It found evidence of subsurface liquid layers of salt water on Europa, 
Ganymede and Callisto and it examined a diversity of volcanic 
activity on Io. Galileo is the first spacecraft to fly by an asteroid 
and the first to discover a moon of an asteroid.

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. 

From launch to impact, the spacecraft has traveled 4,631,778,000 
kilometers (about 2.8 billion miles).

Its entry point into the giant planet’s atmosphere is about 1/4 degree 
south of Jupiter's equator. If there were observers floating along at 
the cloud tops, they would see Galileo streaming in from a point 
about 22 degrees above the local horizon. Streaming in could also be 
described as screaming in, as the speed of the craft relative to 
those observers would be 48.2 kilometers per second (nearly 108,000 
miles per hour). That is the equivalent of traveling from Los Angeles 
to New York City in 82 seconds. In comparison, the Galileo 
atmospheric probe, aerodynamically designed to slow down when 
entering, and parachute gently through the clouds, first reached the 
atmosphere at a slightly more modest 47.6 kilometers per second 
(106,500 miles per hour).

"This is a very exciting time for us as we draw to a close on this 
historic mission and look back at its science discoveries. Galileo 
taught us so much about Jupiter but there is still much to be 
learned, and for that we look with promise to future missions," said 
Dr. Charles Elachi, director of JPL.

JPL, a division of the California Institute of Technology in Pasadena, 
manages the Galileo mission for NASA's Office of Space Science, 
Washington. 

Additional information about the Galileo mission and its discoveries 
is available online at: 



http://galileo.jpl.nasa.gov 

For information about NASA TV on the Internet, visit: 



http://www.nasa.gov/multimedia/nasatv/index.html 

For information about NASA, visit: 



http://www.nasa.gov 

	
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