Editing Galileo project (section)

===Tape recorder problems===
Routine maintenance of the tape recorder involved winding the tape halfway down its length and back again to prevent it sticking.{{sfn|Meltzer|2007|p=226}} In November 2002, after the completion of the mission's only encounter with Jupiter's moon Amalthea, problems with playback of the tape recorder again plagued ''Galileo''. About 10 minutes after the closest approach of the Amalthea flyby, ''Galileo'' stopped collecting data, shut down all of its instruments, and went into safe mode, apparently as a result of exposure to Jupiter's intense radiation environment. Though most of the Amalthea data was already written to tape, it was found that the recorder refused to respond to commands telling it to play back data.<ref>{{cite press release |first=Guy |last=Webster |id=2002-213 |url=https://www.jpl.nasa.gov/news/galileo-millennium-mission-status-3 |title=Galileo Millennium Mission Status |publisher=NASA/Jet Propulsion Laboratory |date=November 25, 2002 |access-date=April 27, 2024 |archive-date=April 28, 2024 |archive-url=https://web.archive.org/web/20240428014837/https://www.jpl.nasa.gov/news/galileo-millennium-mission-status-3 |url-status=live }}</ref>

After weeks of troubleshooting of an identical flight spare of the recorder on the ground, it was determined that the cause of the malfunction was a reduction of light output in three infrared Optek OP133 [[light-emitting diode]]s (LEDs) located in the drive electronics of the recorder's motor [[rotary encoder|encoder]] wheel. The [[gallium arsenide]] LEDs had been particularly sensitive to [[proton]]-irradiation-induced [[crystal|atomic lattice]] displacement defects, which greatly decreased their effective light output and caused the drive motor's electronics to falsely believe the motor encoder wheel was incorrectly positioned.{{sfn|Swift|Levanas|Ratliff|Johnston|2003|pp=1991–1993}}

''Galileo''{{'s}} flight team then began a series of "[[Annealing (metallurgy)|annealing]]" sessions, where current was passed through the LEDs for hours at a time to heat them to a point where some of the crystalline lattice defects would be shifted back into place, thus increasing the LED's light output. After about 100 hours of annealing and playback cycles, the recorder was able to operate for up to an hour at a time. After many subsequent playback and cooling cycles, the complete transmission back to Earth of all recorded Amalthea flyby data was successful.{{sfn|Swift|Levanas|Ratliff|Johnston|2003|pp=1993–1997}}