While the telescope is not expected to be at risk of being permanently out of order, two of the four gyroscopes used to direct the telescope towards its targets in the sky have failed.
This photo of the Hubble Space Telescope was taken on the 5th servicing mission to the observatory in 2009. Astronomers are aiming to prolong Hubble's life, but losing another gyroscope makes life hard.
Hubble could potentially function with just two or even a single active gyroscope, so the latest failure shouldn't be the end of the road for the telescope. But when the third one was powered up, it wasn't operating as it should be, so NASA Goddard engineers placed the telescope in safe mode while they try to figure out the problem.
The Hubble Space Telescope is in an uncomfortable predicament.
The Hubble Space telescope is now in safe mode.
NASA sent a December 1999 Space Shuttle service mission (described here) that replaced failed gyros, and a mission in 2009 (the one Hubble's twitter team referred to) again replaced gyros to extend the telescope's life.
"On Friday, the Hubble Space Telescope went into safe mode due to a failed gyro - used to keep the telescope precisely pointed for long periods", NASA explained in a tweet on the telescope's official page.
"Hubble's instruments still are fully operational and are expected to produce excellent science for years to come", the NASA statement reads. The safe mode is meant to keep the telescope "precisely pointed" for a long duration, the space agency explains, stating that experts are working on fixing the problem.
Responding to a claim that the safe mode was "scary news for the most famous telescope in history", Dr Osten downplayed the issues.
Should NASA fail to recover the malfunctioning gyro, they would resume Hubble's operation using the remaining two gyroscopes. There is a third gyro that might be able to work, but last time NASA tested it there were some issues.
It's impossible to overstate the amount of data Hubble has collected during its 28-year stint in space, and its overall contributions to science.
Although Hubble uses three gyros at a time for maximum efficiency, it can still continue to make scientific observations with just one, NASA said.