NASA images issued in July 2021 shows the Hubble Space Telescope drifting over Earth on May 19 2009
The Hubble Space Telescope is one of NASA's most beloved projects. After over 30 years in service, it's now facing one of its greatest challenges, as a technical glitch has left it in safe mode for over a month. On Wednesday, NASA said it may have tracked down the source of the issue.

The Hubble team had been looking at the payload computer -- hardware dating back to the 1980s -- as the potential source of a memory problem. "A series of multi-day tests, which included attempts to restart and reconfigure the computer and the backup computer, were not successful, but the information gathered from those activities has led the Hubble team to determine that the possible cause of the problem is in the Power Control Unit," NASA said.

As with the payload computer, the PCU is part of Hubble's Science Instrument Command and Data Handling unit. The PCU is responsible for supplying a constant and steady source of electricity to the computer and its memory. Herein lies the possible problem.

"The team's analysis suggests that either the voltage level from the regulator is outside of acceptable levels (thereby tripping the secondary protection circuit), or the secondary protection circuit has degraded over time and is stuck in this inhibit state," NASA said.

Hubble is equipped with a lot of backup systems, including a backup PCU. On Thursday, NASA will attempt the switch to the other hardware in an effort to restore the telescope to normal operations. Since the issue cropped up on June 13, Hubble's science work has been stalled.

If the plan works, it could still take several days to get the telescope back up and running. There has been concern for the aging telescope, which is a joint project from NASA and the European Space Agency. Hubble's successor, the much-delayed James Webb Space Telescope, is still here on Earth, waiting for a possible October launch.

Hubble has weathered many technical glitches in its time, and it may yet survive this latest one. The good news is NASA has a plan, and the hope to go along with it.