Engineers are still troubleshooting a glitch with the Hubble Space Telescope’s payload computer that put the observatory in “safe mode,” a sort of electronic hibernation, until the problem is resolved.
The shutdown occurred just after 20:00 GMT on 13 June when the computer, which controls and coordinates observations by Hubble’s science instruments, stopped sending routine “keep-alive” signals to the telescope’s primary computer. That, in turn, activated software that automatically halted instrument operations, shutting down science observations.
Engineers initially suspected problems with one of four 64K solid-state memory modules used by the computer. But an attempt to switch to an alternate module was not successful, prompting another round of troubleshooting.
The payload computer is known as a “NASA Standard Spacecraft Computer-1, or NSSC-1, built in the 1980s and part of the telescope’s Science Instrument Command and Data Handling unit. The computer is fully redundant, with two independent “strings,” either one of which can handle all payload functions. Whichever string is operating uses one memory module with the other three on standby as backups.
As of 18 June, engineers were still collecting diagnostic data and had not yet resorted to attempting a switch over to the alternate computer string.
“The operations team will be running tests and collecting more information on the system to further isolate the problem,” NASA said in a statement. “The science instruments will remain in a safe mode state until the issue is resolved. The telescope itself and science instruments remain in good health.”