A damaged data recorder aboard NASA鈥檚 Galileo space probe has finally been reactivated, allowing scientists to retrieve the secrets of the craft鈥檚 final mission.
The tape recorder was damaged when Galileo flew through Jupiter鈥檚 intense radiation belt on 5 November. The device holds information collected by Galileo鈥檚 instruments on its last journey.
This took it on an unprecedented pass through the Jupiter鈥檚 inner Gossamer Ring, a dust belt that stretches from the inner moon Amalthea to the planet鈥檚 main dust ring, and then into the planet鈥檚 inner magnetic field.
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鈥淲e hope this will be the best data set that鈥檚 ever been collected about the inner region of Jupiter鈥檚 magnetic environment,鈥� said Torrence Johnson, Galileo project scientist at NASA鈥檚 Jet Propulsion Laboratory in California.
Remote repair
The spacecraft automatically shut down all of its instruments in response to the high radiation. Most were successfully reactivated 10 days later but the tape device refused to respond to commands.
Engineers traced the problem to a light-emitting diode (LED) within the electronics that control the tape player鈥檚 motor drive. They suspect that protons from Jupiter鈥檚 radiation belt may have disrupted the crystalline lattice of the semiconductor material from which the diode is made.
To correct the problem, the Galileo engineers repeatedly directed an electrical current though the diode for an hour at a time. This prompted the atoms to shift back to their lattice positions. This annealing treatment lasted for a total of 83 hours.
Crash landing
The tape recorder will only play for a few minutes at a time but this is sufficient to retrieve data, the probe鈥檚 controllers say. Playback will continue until mid-January when the craft is scheduled to shut down for the last time.
Galileo is almost out of fuel and has been set on a collision course that will see it burn up in Jupiter鈥檚 atmosphere in September 2003. This will prevent the probe hitting and contaminating Jupiter鈥檚 moon Europa, which researchers believe could harbour primitive lifeforms.
Galileo has operated five years longer than originally planned and has been exposed to four times as much radiation as it was designed to withstand.