After a few perilous weeks of uncertainty due to a broken gyroscope, the Hubble Space Telescope is fully functioning. It's not quite turning it off and turning it back on again as some coverage made it seem. However, NASA officials likened the process to "jiggling around" a bit to fix the issue.
Two weeks ago, the Hubble Space Telescope was forced to enter safe mode after a gyroscope -- the piece that steadies the most important functions of the telescope -- failed.
Fixing the backup gyro
NASA released a press statement a few days ago explaining how they freed up the gyroscope (aka gyro):
"In an attempt to correct the erroneously high rates produced by the backup gyro, the Hubble operations team executed a running restart of the gyro on Oct. 16. This procedure turned the gyro off for one second, and then restarted it before the wheel spun down. The intention was to clear any faults that may have occurred during startup on Oct. 6, after the gyro had been off for more than 7.5 years. However, the resulting data showed no improvement in the gyro’s performance."
"On Oct. 18, the Hubble operations team commanded a series of spacecraft maneuvers, or turns, in opposite directions to attempt to clear any blockage that may have caused the float to be off-center and produce the exceedingly high rates. During each maneuver, the gyro was switched from high mode to low mode to dislodge any blockage that may have accumulated around the float."
And while turning off the gyro for a second and then restarting the wheel might sound like any IT guy's suggestion, the process was far more complicated.
First, NASA engineers had to power up a backup gyro largely untouched since 2011. They were excited, initially, because the gyroscope started working after nearly eight years of dormancy.
However, their concern grew when the gyro sent back readings far too high.
NASA officials told the press that the issue was “similar to a speedometer on your car continuously showing that your speed is 100 miles per hour faster than it actually is,” NASA said. “It properly shows when your car speeds up or slows down, and by how much, but the actual speed is inaccurate.”
Engineers with NASA guessed it was an obstruction within the gyro causing it to lose functionality. While NASA worked on it, they put Hubble into safe mode -- a bare-bones setting for the popular space telescope. "Safe mode" also meant Hubble was 'closed' for new discoveries.
While in safe mode, engineering teams maneuvered the gyro in various rotations to try and knock the blockage out of the backup system.
More complicated than a simple IT fix
Hubble Operations Project Manager Patrick Crouse explained why the "turning it off and on again" methodology didn't work for Hubble (and why it's annoying to read in the press).
“At a high level, if people want to call it jiggling around, I suppose they can,” he said. “But we were trying to do very particular activities we thought would clear the problem. It certainly wasn’t as simple as turning it off and turning it back on.”
Regardless of how it happened, astronomers can breathe a sigh of relief that the most popular space telescope is finally back to normal.
"Originally required to last 15 years, Hubble has now been at the forefront of scientific discovery for more than 28 years," NASA officials explained. "The team expects the telescope will continue to yield amazing discoveries well into the next decade, enabling it to work alongside the James Webb Space Telescope."