But after the failure last week, the Hubble is now left with only two fully-operational gyros.
Hubble is equipped with six gyroscopes, but it's been operating with only three active gyros.
Launched aboard the shuttle Discovery in April 1990, Hubble is one of the most scientifically productive spacecraft ever built, generating a steady stream of astronomical discoveries and iconic photos familiar to millions around the world. The space shuttle Atlantis' mission is to overhaul the Hubble Space Telescope in order to extend its working life. That's the error engineers are working to fix now, with the instrument in safe mode to allow them to run tests. Exhibiting end-of-life behavior for about a year, the gadget actually exceeded expectations. The three remaining gyroscopes have been enhanced, and - in theory at least - will have much longer operational lives than the three failed gyroscopes.
Hubble has six gyroscopes, all of which were replaced by spacewalking astronauts during a servicing mission in May 2009. According to BBC, four were still working when the failure occurred late last week. The space agency said that they tried powering up a reserve gyroscope, but their telemetry indicated that "it was not performing at the level required for operations". NASA's decision to retire its space shuttles in 2011 means that astronauts can not service the 28-year-old observatory as they once did. Still, the telescope can function with just two gyros, and it could even continue observing the universe with just one.
"Very stressful weekend", Rachel Osten, deputy mission head for the Hubble Space Telescope, tweeted on Sunday.
Two gyros of the same type had already failed.
'We'll work through the issues and be back'.
"If the outcome indicates that the gyro is not usable, Hubble will resume science operations in an already defined "reduced-gyro" mode that uses only one gyro".
While reduced-gyro mode offers less sky coverage at any particular time, there is relatively limited impact on the overall scientific capabilities, NASA said in the statement.