NASA Still Trying to Revive Hubble Telescope After Memory Swap Fails

The Hubble Space Telescope has been offline for a week following a failure in the observatory’s payload computer, and it might take longer than we expected to get it back up and running. NASA reports it has made several attempts to switch to backup memory modules, but it hasn’t worked. The team is now exploring the possibility that the issue is more severe, but we won’t know the damage until the investigation is further along. 

The trouble started on June 13th when the telescope’s payload computer stopped working. This is a separate system from Hubble’s main computer that controls the science instruments. It pings the main computer with a “keep alive” signal, but that stopped on June 13th. That sent the observatory into safe mode, where it has remained ever since. 

Initially, NASA believed the issue was a deteriorating 64K memory module. Yes, that’s a very small amount of active memory for 2021, but this is a NASA Standard Spacecraft Computer-1 (NSSC-1) system built in the 1980s. Luckily, the NSSC-1 is built with four redundant memory modules. Theoretically, NASA should have been able to tell the computer to switch to a backup, and all would be right. However, the system stubbornly refuses to cooperate. 

NASA now believes the system failure lies elsewhere in Hubble’s hardware, and the memory corruption was merely a symptom. The focus now is on the Standard Interface (STINT) hardware, which connects the Central Processing Module (CPM) to the computer’s other components. The team is designing tests that can be run remotely to diagnose the problem.

Hubble’s final 2009 servicing mission.

Luckily, there is still hope even if NASA determines the payload computer is busted. During Hubble’s last servicing mission in 2009, astronauts replaced a recently failed Science Instrument Command and Data Handling unit, which contains the payload computer and a backup for that system. NASA has reviewed the procedure for swapping to the backup payload computer, which accesses the same four memory modules as the current one. 

So, as long as the backup computer and at least one memory module are still functional, Hubble should be alive again soon. If, however, there’s a problem with the backups, this could be the telescope’s swansong. That would leave the world’s astronomers without a high-power orbiting observatory until NASA’s long-delayed Webb telescope launches (hopefully) late this year.

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