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Galileo to end stint, UA-led Cassini will take over

After a successful 11 year mission in space, the Galileo Imaging Team announced yesterday the spacecraft will end its duties early next year, bowing to the technologically superior UA-led Cassini imaging spacecraft.

The last major mission for Galileo will be a rendezvous with Cassini in December. The two spacecraft will jointly examine the magnetosphere surrounding Jupiter.

Scientists hope this joint effort will give them a better idea of the cause and effect relationship between the magnetosphere and solar winds.

"One spacecraft will be on the outside of the magnetosphere and will look at the effects of the magnetosphere," said Ronald Greeley, professor at Arizona State University, and a member of the Galileo Imaging Team. "The other will be on the inside and will examine what the magnetosphere is doing."

Since the launch of Galileo in 1989, the spacecraft has made 35 separate missions. But radiation from Jupiter's magnetosphere has taken its toll on the aging spacecraft and the time has come to retire it, said Torrence Johnson of NASA's Jet Propulsion Laboratory.

"The radiation build-up was higher than we first expected it would be. In fact, it was three times our first estimate," Johnson said at yesterday's news conference.

Another expected problem plaguing Galileo is the decrease in the amount of propellant in the spacecraft.

"At lift-off we had nearly 900 kilos of propellant." Johnson said. "Now we have somewhere in the range of the low double digits."

During its reign, the Galileo spacecraft made many significant discoveries, most notably that Jupiter's moon Ganymede has its own magnetic field.

More recently, the imaging craft discovered that Io - another of Jupiter's moons - is the most volcanically active mass in the solar system. Io has the largest lava flow in the universe, which stretches nearly 200 miles.

Currently, Galileo is finishing an examination of another of Jupiter's moons, Europa.

Carolyn Porco, leader of the Cassini Imaging Team, said the Galileo missions have been successful.

"The Galileo Imaging Team should be enormously congratulated on their success in difficult circumstances," said Porco, who is also a member of the University of Arizona's Lunar and Planetary Laboratory.

While the Galileo mission has a long list of achievements, Porco said she expects great things from the Cassini spacecraft.

"The Cassini has a camera system that is more capable than Galileo," she said.

Cassini - launched in the early 1990s - will have two cameras, as opposed to one camera on Galileo.

Porco said another bonus is that Cassini has a high-gain antenna, which will allow the craft to gather information on atmospheric conditions surrounding Jupiter. Galileo was unable to deploy its antenna.

"We will go to Jupiter and examine the atmospheric conditions around the planet," she said.

Porco said Cassini will also be able to see into ultraviolet light, while Galileo couldn't.

She added the main focus of the Cassini mission is investigating every part of Saturn.