NASA engineers have figured out how to bring the ailing Hubble Space Telescope back online after troubleshooting an instrument that wasn’t working properly. The observatory, currently in orbit around Earth, has been in safe mode since October 5th when a crucial piece of steering hardware — needed to point the telescope — failed. A backup piece of hardware will be used instead, allowing Hubble to operate at its full capacity again.

One of Hubble’s gyroscopes, the devices that are needed to measure how fast the telescope is turning in space, failed on October 5th. Two of Hubble’s six gyros are already offline, and the failure brought the working number of gyros down to three. Hubble only needs three of them to work at any given time in order to perform its job, but NASA had some trouble getting one of the three functioning gyros to work properly. It’s actually been turned off for seven and a half years, and when NASA started using it again, it was sending back bad data about how the Hubble was turning. The gyro sensed that Hubble was rotating much faster than it was.

The failed instrument was one of Hubble’s gyroscopes

Technically, Hubble could operate with two gyros, but the telescope would be limited in the types of targets that it could observe. It looks like NASA won’t have to rely on just two gyros, though. In an update, the space agency noted that Hubble engineers turned the wonky gyro off for one second and then turned it back on again. That didn’t fix the problem. But then, the team programmed a bunch of maneuvers for Hubble to potentially reset the gyro, in case the cylinder inside the gyro was off-center. That seemed to do the trick; afterward, they gyro stopped measuring super high rotation rates for Hubble.

The gyros consist of spinning wheels that rotate 19,200 times a minute inside a cylinder that’s suspended in fluid. It’s a fancy setup that allows sensors in the cylinders to pick up very small movements in the spinning wheel that can then be communicated to Hubble’s computer. That information is crucial whenever Hubble needs to turn and stay focused on a new target in the Solar System and beyond.

All six of these instruments have been replaced at some point over the telescope’s nearly 30-year history in orbit. Thanks to the Space Shuttle program, astronauts could service Hubble whenever it was in need of repairs. But since the Space Shuttle is no longer flying, there is no vehicle currently capable of bringing humans to the spacecraft. So when something breaks, NASA has to fix it from the ground.

Hubble has been in safe mode ever since its gyro failed

Hubble has been in safe mode ever since its gyro failed, a state in which most of the spacecraft’s instruments are turned off. So the telescope hasn’t been able to do any observations for a while. Hubble is an important tool for the astronomy community, taking images of everything from distant galaxies and stars to faraway objects in our own Solar System.

Hubble isn’t completely ready to return to action yet. NASA has been doing maneuvers with the telescope to make sure the newly fixed gyro continues to work properly. The engineering team also has a bunch of tests planned for the spacecraft to evaluate the gyro further. If those go well, Hubble can get back to its regular workload.