NASA is working to restart scientific operations of the Hubble Space Telescope, which went into safe mode on November 23 due to a problem with its gyroscope. Hubble’s instruments are intact and the telescope is in good health.

When one of the three gyroscopes gave an incorrect measurement, the telescope automatically went into safe mode. Gyroscopes measure the speed of rotation of the telescope and are part of the system that determines the orientation of the telescope. In safe mode, scientific operations are stopped and the telescope awaits new instructions from the ground.

Hubble entered safe mode for the first time on November 19. Although the task force successfully recovered the spacecraft and resumed observations the next day, an unstable gyroscope forced the observatory to cease science activities again on November 21. After a successful recovery, Hubble entered safe mode on November 23.

The team is currently running tests to characterize the problem and develop a solution. If necessary, the spacecraft can be reconfigured to operate with a single gyroscope. During the fifth and final spacecraft maintenance mission in 2009, six new gyroscopes were installed on the spacecraft.

Three of these gyroscopes remain operational today, including the gyroscope currently experiencing oscillation. Hubble uses three gyroscopes to maximize efficiency, but it can still make scientific observations with just one gyroscope if necessary.