NASA says mission controllers are working to restore the 28-year-old telescope.
Gyroscopes are needed to keep Hubble pointed in the right direction during observations.
‘It’s true. Very stressful weekend,’ Rachel Osten, Hubble’s deputy mission head at the Space Telescope Science Institute in Baltimore, said on Twitter.
‘Right now HST is in safe mode while we figure out what to do.
‘Another gyro failed.
‘First step is try to bring back the last gyro, which had been off, and is being problematic.’
Launched in 1990, Hubble has had trouble with its gyroscopes before.
Spacewalking shuttle astronauts replaced all six in 2009.
The telescope could work with as few as one or two gyroscopes, although that leaves little room for additional breakdowns.
Olsten confirmed the problem would not mean the end of Hubble.
‘Not really scary, we knew it was coming.
‘The gyro lasted about six months longer than we thought it would (almost pulled the plug on it back in the spring).
‘We’ll work through the issues and be back.’
Even with one gyro working , Hubble will still be able to take part in science, NASA confirmed.
‘There isn’t much difference between 2- and 1, and it buys lots of extra observing time. Which the Astro community wants desperately.’
Astronomers use the orbiting observatory to peer deep into the cosmos, revealing faraway solar systems as well as galaxies and black holes.