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Galileo Blacks Out Again
25 November 1998 6:00 pm
The Galileo spacecraft unexpectedly shut down on 22 November, just before it was to fly by Europa. NASA engineers had the spacecraft operating normally a day later, but they lost a chance to observe the Jovian moon, which appears to harbor an ice-covered ocean that may hold primitive life. NASA says it has identified the problem and is investigating possible fixes. Galileo heads back to Europa in late January.
This is not the first time Galileo has blacked out. Since the spacecraft began orbiting Jupiter in December 1995, it has turned itself off more than 2 dozen times. On Sunday, Galileo's computers detected an anomaly and triggered its safe mode 6 hours before the Europa flyby, which was to examine the surface for possible chemical signs of life. This mode shuts down sensitive instruments and orients the craft's antennas toward Earth until ground control reactivates the craft. "Unfortunately ... most of the near-encounter observations weren't recorded," says Torrence Johnson, NASA's project scientist for Galileo at the Jet Propulsion Laboratory in Pasadena, California. But some data taken before the shutdown can be played back, he says.
NASA's engineers blame the glitches on worn-out electrical contacts that carry power and data between the two spacecraft parts that rotate around each other. "Some metal debris creates electrical shortages for very brief periods," says Johnson. "We are looking for ways to have the spacecraft automatically recover from safing," including writing new software, he says.
Hassles aside, Pierre Drossart of Paris Observatory at Meudon, who investigates the Jovian atmosphere, takes a sanguine view. "We are, after all, very satisfied with the functioning of the probe," he says. "It is one of the [technically] most complex probes ever launched."