Posted on 09/17/2003 7:31:46 PM PDT by TopQuark
Galileo probe to collide with Jupiter on Sunday
By Deborah Zabarenko
WASHINGTON (Reuters) - After eight years orbiting Jupiter, NASA's Galileo space probe will end its long mission on Sunday by plunging through the Jovian cloud tops and smashing into the giant planet -- collecting data as it goes.
Low on propellant and six years past its original end date, Galileo has set a collision course with Jupiter to eliminate any unwanted crash into the Jovian moon Europa, officials at NASA's Jet Propulsion Laboratory said in a statement.
The spacecraft is so low on fuel it will not be able to point its antenna toward Earth or adjust its trajectory, but scientists believe it will be able to send back a few hours of information on its last descent.
"It has been a fabulous mission for planetary science, and it is hard to see it come to an end," Galileo project manager Claudia Alexander said. "... We're keeping our fingers crossed that, even in its final hour, Galileo will still give us new information about Jupiter's environment."
The Galileo team will gather at the laboratory's Pasadena, California, headquarters on Sunday to bid the little craft farewell, scientist Rosaly Lopes said by telephone on Wednesday.
"Galileo was a real fighter of a spacecraft, it actually had a lot of problems right from the beginning," Lopes said, adding that the difficulties were always overcome -- and in fact inspired an ingenious "slingshot" route to Jupiter.
The small robotic craft was supposed be launched in 1986 on the space shuttle following the January flight of shuttle Challenger. When Challenger exploded seconds after liftoff, Galileo's trip was postponed until 1989.
'SLINGSHOT' TO JUPITER
By that time, Lopes said, the rocket boosters originally intended to power Galileo to Jupiter were not available. The boosters that were used were thought capable of sending Galileo to Mars but no further.
Lopes credited the Galileo team's engineers with inventing the so-called VEEGA trajectory, short for Venus, Earth, Earth gravity assist. This route sent the spacecraft to Venus and around Earth before it was lobbed to the asteroid belt and then back around Earth again to get an assist from Earth's gravity -- a sort of gravitational slingshot -- to fling it all the way to Jupiter.
Astronomers hope to retrieve Galileo's data, but radiation from Jupiter could be a problem. The craft has already weathered more than four times the dose of harmful Jovian radiation it was designed to withstand, and Galileo is entering a particularly high-radiation area as it approaches the planet.
Launched from space shuttle Atlantis in 1989, Galileo will have traveled about 2.8 billion miles (4.6 billion km) by the time it hits Jupiter.
The end doesn't sound pretty.
"The spacecraft will reach the outermost layers of Jupiter's atmosphere, which is very dense," Lopes said. "There will be a lot of friction. (Galileo) will begin to burn and crush and disintegrate and then it will just vaporize and become part of Jupiter."
Galileo orbited Jupiter 34 times and obtained the first direct measurements of Jupiter's atmosphere by sending a descent probe parachuting down toward the planet in 1995. It detected evidence of underground salt water oceans on Jupiter's moons Europa, Ganymede and Callisto, and examined the lively, intensely hot, volcanoes on the moon Io
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