NASA has brought Hubble Space Telescope’s seven-year old backup gyroscope (gyro) back to life, after the spacecraft entered safe mode due to a failed gyro earlier this month, the US space agency said on Tuesday. A gyro is a device that measures the speed at which the spacecraft is turning and is needed to help Hubble turn and lock on to new targets.
Hubble’s backup gyro, which had been off for more than 7.5 years, was incorrectly returning extremely high rotation rates, NASA said in a statement. This gyro was turned on after the spacecraft entered safe mode due to a failed gyro on October 5. Additional tests will be performed to ensure Hubble can return to science operations with this gyro, NASA said.
To correct high rotation rates, the Hubble team executed a running restart of the gyro on October 16. This procedure turned the gyro off for one second, and then restarted it before the wheel spun down. However, the data showed no improvement in the gyro’s performance.
The team, then on October 18, commanded a series of spacecraft manoeuvres, or turns, in opposite directions to attempt to clear any blockage that may have caused the float to be off-centre and produce the exceedingly high rates. During each maneuver, the gyro was switched from high mode to low mode to dislodge any blockage that may have accumulated around the float. They noticed a significant reduction in the high rates, allowing rates to be measured in low mode for brief periods of time.
On October 19, the team again commanded Hubble to perform additional manoeuvres and gyro mode switches, which appear to have cleared the issue. The rotation rates produced by the backup gyro have since reduced and are now within an expected range, NASA noted.
The team plans to execute a series of tests to evaluate the performance of the gyro under conditions similar to those encountered during routine science observations, including moving to targets, locking on to a target, and performing precision pointing. After these engineering tests have been completed, Hubble is expected to soon return to normal science operations, NASA stated.