NASA officials have announced that the agency is making progress in resuming Hubble Space Telescope science operations. The telescope entered into safe mode on Friday, October 5 following the failure of one of the spacecraft’s gyros.
The Hubble Space Telescope was fitted with 6 new gyros in 2009 during a servicing mission. The telescope requires three gyros to operate optimally. Over the last decade, two of the 6 gyros had failed. Following the latest failure, the last gyro, which was being held in reserve, was turned on and should have allowed the telescope to continue operations uninterrupted.
Gyros operate using a small wheel spinning at 19,200 revolutions a minute. The wheel is suspended in a thick fluid and sealed in a cylinder. Electronics monitor the wheel for slight movements of its axis. If any movement is detected, the gyro fires to cancel out the movement ensuring the telescope remains steady while operational.
Moments after turning Hubble’s reserve gyro on, engineers noticed that it was incorrectly returning extremely high rotation rates. With the wheel potentially spinning at dangerously high speeds, the risk to the health of the telescope was deemed too high to continue operations. As a result, the spacecraft was placed in safe mode until engineers could fix the problem.
Since then, the Hubble operations team has made several attempts to clear any faults in the gyro. On October 16, the team executed a “running restart” of the faulty gyro. The processes essentially involved turning it on and off again quickly and hoping that would clear any faults. Data from the telescope following the “running restart” showed no improvement.
On October 18, the telescope’s operations team had Hubble’s spacecraft run a series of manoeuvres in opposite directions while shifting the affected gyro from low to high mode. Simply put, the team ordered Hubble to give itself a shake to clear any blockages that may have built up over the 7.5 years it sat idle. The operation was performed again on October 19 following which, all data from the telescope seemed to indicate that the fault had been resolved.
Additionally, testing of Hubble’s system will be conducted over the next couple of days to ensure the gyro remains stable. Once testing has been completed, the telescope will resume science operations. It is hoped that the telescope will remain operational for years to come.