The Hubble Space Telescope has been put in 'safe mode' after one of its gyroscopes -- used to point and steady the probe -- failed, NASA said.
The US space agency is working to resume science operations of the after the spacecraft entered safe mode on October 5.
Hubble's instruments still are fully operational and are expected to produce excellent science for years to come, NASA said in a statement.
Safe mode puts the telescope into a stable configuration until ground control can correct the issue and return the mission to normal operation.
Built with multiple redundancies, Hubble had six new gyros installed during Servicing Mission-4 in 2009. Hubble usually uses three gyros at a time for maximum efficiency, but can continue to make scientific observations with just one.
The gyro that failed had been exhibiting end-of-life behaviour for approximately a year, and its failure was not unexpected; two other gyros of the same type had already failed.
The remaining three gyros available for use are technically enhanced and therefore expected to have significantly longer operational lives. Two of those enhanced gyros are currently running.
Upon powering on the third enhanced gyro that had been held in reserve, analysis of spacecraft telemetry indicated that it was not performing at the level required for operations. As a result, Hubble remains in safe mode.
Staff at NASA's Goddard Space Flight Center and the Space Telescope Science Institute are currently performing analyses and tests to determine what options are available to recover the gyro to operational performance.
Science operations with Hubble have been suspended while NASA investigates the anomaly.
An Anomaly Review Board, including experts from the Hubble team and industry familiar with the design and performance of this type of gyro, is being formed to investigate this issue and develop the recovery plan.
If the outcome of this investigation results in recovery of the malfunctioning gyro, Hubble will resume science operations in its standard three-gyro configuration.
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.
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