The Hubble recovery team thinks it’s finally tracked down a problem that’s kept the space telescope out of commission for over a month.
The problem started on June 13, when an onboard computer suddenly ground to a halt. All science instruments on Hubble went into safe mode as a result, and it’s been that way ever since. The telescope is otherwise fine, but normal operations have been suspended.
The problem is with the payload computer, which controls and monitors Hubble’s science instruments. It’s the most serious glitch to afflict Hubble in years, raising concerns that the ageing telescope might finally be finished. Launched in 1990, Hubble has conducted over 1.5 million observations and contributed significantly to our understanding of the solar system, galaxies, and the universe in general.
The Hubble recovery team has tried all sorts of tests over the past few weeks (a running list of measures taken can be seen here), along with attempts to restart and reconfigure the payload computer, but nothing has worked. Data collected during these attempts has now led the team to determine that the “possible cause” of the glitch has something to do with the Power Control Unit (PCU) located on the telescope’s Science Instrument Command and Data Handling unit, according to NASA.
The PCU supplies electricity to the payload computer. Equipped with a power regulator, the PCU provides a steady 5 volts of electricity to both the payload computer and its memory modules. As NASA explains:
A secondary protection circuit senses the voltage levels leaving the power regulator. If the voltage falls below or exceeds allowable levels, this secondary circuit tells the payload computer that it should cease operations. 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.
Commands to reset the PCU haven’t worked, so it’s probably borked. In response, NASA management has approved a plan to switch over to backup hardware. This rescue operation is scheduled to start today, and it could take a few days to complete.
Hubble has experienced a slew of problems over the years, but NASA always seems to find a way to bring the telescope back. Hubble may be old, but it’s expected to remain in operation until the 2030s. Should all go well, and should Hubble return to service, it could serve alongside the upcoming James Webb Space Telescope, which is scheduled to launch later this year.