Hubble Space Telescope in ‘safe mode’ – engineers troubleshooting

A cut-away view of the Hubble Space Telescope showing its instruments grouped behind the primary mirror. A glitch in the system that synchronises commands and data to and from the instruments has put the telescope in protective ‘safe mode’ while engineers troubleshoot the problem. Image: NASA

Engineers are troubleshooting a timing issue in the electronics of the Hubble Space Telescope that has twice triggered protective “safe mode” software. While the rest of the telescope’s systems are operating normally, science operations have been suspended pending resolution of the problem.

The issue first cropped up on 23 October when Hubble’s science instruments downlinked error codes indicating a synchronisation problem preventing the correct responses to commands and requests for data. Engineers reset the instruments and science observations resumed on 24 October.

But the next day, the instruments again issued error codes indicating multiple instances of lost synchronisation. Again, the error codes triggered safe mode, a sort of electronic hibernation designed to keep the observatory safe while engineers work to figure out what’s causing the problem.

“Mission team members are evaluating spacecraft data and system diagrams to better understand the synchronisation issue and how to address it,” NASA said in a 1 November statement. “They also are developing and testing procedures to collect additional data from the spacecraft. These activities are expected to take at least one week.”

The glitch is another reminder that Hubble, now in its 31st year of service, is living on borrowed time 12 years after a fifth and final space shuttle servicing mission in 2009. While it has remained remarkably healthy since then, ageing components are expected to slowly but surely take their toll.

Most recently, engineers needed weeks to resolve a problem with the telescope’s payload computer, eventually switching over to backup components in July to return the observatory to normal operation.