The Hubble Space Telescope has been expanding our knowledge of the cosmos for more than three decades, a spectacularly long run for any spacecraft. Nothing can stop the inevitable, though. NASA has again taken the iconic observatory offline due to a hardware glitch. This time, it’s the satellite’s gyroscopes acting up, but NASA expects to be able to bring Hubble back online.
The gyroscopes, along with reaction wheels and fine guidance sensors, are part of Hubble’s orientation system. The satellite has no thrusters, so Hubble relies on this system to determine where it’s pointed and make adjustments as new observation orders arrive from Earth. Gyroscopes measure the turn rate, without which operators don’t know how much to adjust.
The latest issues began on Nov. 19 when the problematic gyroscope failed and caused Hubble to go into safe mode—that’s not the first time, either. NASA successfully restarted the system and returned Hubble to operation soon after. However, the gyro continued to cause issues, and NASA again suspended operations on Nov. 21. Engineers attempted a fix for the malfunctioning gyroscope, but Hubble went back into safe mode on Nov. 29, and it remains that way as of now.
Hubble launched initially with six gyroscopes, but they failed quickly. That was when NASA had a Space Shuttle that could rendezvous with Hubble for service missions. There have been suggestions of another mission, but nothing is firm. In the final 2009 service run, NASA replaced all the gyroscopes. Three were the old, unreliable model, and three were new versions. The old gyros contain a bromine solution that slowly degrades the internals, so failure is inevitable. The three old type gyros stopped working in a few years, leaving the three newer models. It is one of these causing issues now after 14 years.
NASA expects to have Hubble working again soon, even if the only solution is turning off the malfunctioning component. Hubble can be reconfigured to operate with just one gyroscope, so turning off the bad one isn’t the end of the world. If NASA arrives at that solution, Hubble will be one step closer to a failure from which it cannot recover. NASA currently hopes to keep the telescope alive through the early 2030s. Even though the more advanced Webb telescope is online, Hubble continues to make important contributions. We can only hope it comes back online soon.
