information:extraction
2021 power control issue

On June 13, 2021, Hubble's payload computer halted due to a suspected issue with a memory module. An attempt to restart the computer on June 14 failed. Further attempts to switch to one of three other backup memory modules on board the spacecraft failed on June 18. On June 23 and 24, NASA engineers switched Hubble to a backup payload computer, but these operations have failed as well with the same error. On June 28, 2021, NASA announced that it was extending the investigation to other components. Scientific operations were suspended while NASA worked to diagnose and resolve the issue. After identifying a malfunctioning power control unit (PCU) supplying power to one of Hubble's computers, NASA was able to switch to a backup PCU and bring Hubble back to operational mode on July 16. On October 23, 2021, HST instruments reported missing synchronization messages and went into safe mode. By December 8, 2021, NASA had restored full science operations and was developing updates to make instruments more resilient to missing synchronization messages.