[astroCS] Životná púť Galilea sa končí!

[Marek Husarik]

Zdroj:
http://www.reuters.com/newsArticle.jhtml;jsessionid=FUBMDKQID4EFECRBAELCFEY?type=scienceNews&storyID=3463262

             
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       Galileo Probe to Collide with Jupiter on Sunday 
             
Wed September 17, 2003 05:57 PM ET 
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 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.