Doomed Jupiter probe goes blind early

Galileo spied Culann Patera, one of the most colorful volcanic regions on Io, during an earlier flyby.

By Richard Stenger
CNN Sci-Tech

(CNN) -- Making its closet approach to one of Jupiter's moons, the aging Galileo spacecraft experienced a glitch and could not snap one final flurry of photographs.

As the craft skimmed within 62 miles (100 km) of Io on Thursday, perilously close to the dangerous radiation belts of Jupiter, the NASA robot ship for unknown reasons went into safe mode, which automatically shut down onboard instruments.

"We're not totally surprised, because Galileo has already outlived expectations and we knew that it might encounter additional difficulties from the high-radiation environment on this flyby," said Eilene Theilig, lead Galileo scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calfifornia.

An inhabitant of the Jupiter system for six years, Galileo has already survived four years longer than expected and endured more than three times the radiation it was designed to withstand.

Flight engineers hope to restore normal operations on the craft so it can resume scientific observations during the remainder of the Io encounter, expected to last until Sunday.

The camera, however, which has weathered radiation problems in the past, will likely take no more photographs. The Io photo shoot was to be its last.

The $1.4 billion orbiter did manage to keep to its intended course over Io. Using the gravity of the moon, the flyby was planned to boost Galileo into an orbital path that will eventually lead to its destruction.

"The reason we're going so close is to put Galileo on a ballistic trajectory for impact into Jupiter," Theilig said.

Documenting wacky worlds

Launched in 1989, the robot ship has spotted an asteroid with a moon, a comet striking Jupiter and dozens of molten cauldrons on Io, the most volcanic body in the solar system.

The jagged ridges of Callisto resemble nothing seen on other jovian moons.

Galileo has taken more than 10,000 images, many documenting puzzling and stunning features on Io and the other major jovian moons, Ganymede, Callisto, Europa.

Among its achievements, Galileo's observations offered evidence that Europa possesses a deep saltwater ocean under its frozen exterior.

One year ago, the vessel took part in an unprecedented collaboration when it, and the Saturn-bound Cassini probe, conducted joint observations during the latter's brief stopover in the Jupiter system.

Its camera shuttered, its fuel and mission budget nearly exhausted, Galileo will nonetheless keep taking other scientific readings. In November, it will make the first close flyby of Amalthea, a small, inner moon of Jupiter.

The finale is expected in September 2003, when Galileo will plunge into the crushing atmosphere of Jupiter. The suicide run is to ensure the probe does not strike and contaminate Europa, which scientists speculate could harbor microbial life.