Update on the Hubble Space Telescope Safe Mode

Hubble Space Telescope (Credit: NASA)

GREENBELT, Md. (NASA PR) — NASA continues to work toward resuming science operations of the Hubble Space Telescope after the spacecraft entered safe mode due to a failed gyroscope (gyro) on Friday, Oct. 5.

Following the gyro failure, the Hubble operations team turned on a backup gyro on the spacecraft. However, that gyro did not perform as expected, reporting rotation rates that are orders of magnitude higher than they actually are. This past week, tests were conducted to assess the condition of that backup gyro. The tests showed that the gyro is properly tracking Hubble’s movement, but the rates reported are consistently higher than the true rates. This is similar to a speedometer on your car continuously showing that your speed is 100 miles per hour faster than it actually is; it properly shows when your car speeds up or slows down, and by how much, but the actual speed is inaccurate.

When the spacecraft turns across the sky from one target to the next, the gyro is put into a coarser (high) mode. In this high mode it may be possible to subtract out a consistent large offset to get an accurate reading. However, after the large turns are over, the spacecraft attempts to lock onto a target and stay very still. For this activity, the gyro goes into a precision (low) mode to measure very small movements. The extremely high rates currently being reported exceed the upper limit of the gyro in this low mode, preventing the gyro from reporting the spacecraft’s small movements.

An anomaly review board that consists of professionals experienced in the manufacturing of such gyros, Hubble operations personnel, flight software engineers and other experts was formed earlier this week to identify the cause of this behavior and determine what solutions can be implemented from the ground to correct or compensate for it.

If the team is successful in solving the problem, Hubble will return to normal, three-gyro operations. If it is not, the spacecraft will be configured for one-gyro operations, which will still provide excellent science well into the 2020s, enabling it to work alongside the James Webb Space Telescope and continue groundbreaking science.

Safe mode places the telescope into a stable configuration that suspends science observations and orients the spacecraft’s solar panels toward the Sun to ensure Hubble’s power requirements are met. The spacecraft remains in this configuration until ground control can correct or compensate for the issue. The rest of the spacecraft and its instruments are still fully functional and are expected to produce excellent science for years to come.

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. To meet the stringent pointing requirements necessary to study far-off astronomical objects and obtain groundbreaking science data, Hubble’s gyros are extremely accurate. Hubble preferably uses three gyros at any given time to make the observatory as efficient as possible, and would work at slightly lower efficiency on only one gyro.

During Servicing Mission 4 in 2009, astronauts installed six new gyros on Hubble. Three gyros have since failed after achieving or exceeding the average runtime for a Hubble gyro. When fewer than three operational gyros remain, Hubble will continue to make scientific observations in a previously developed and tested mode that uses just one gyro in order to maximize the observatory’s lifetime.

Originally required to last 15 years, Hubble has now been operating for more than 28. The final servicing mission in 2009, expected to extend Hubble’s lifetime an additional 5 years, has now produced more than 9 years of science observations.

Hubble is managed and operated at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

For more information about Hubble, visit:

www.nasa.gov/hubble

  • Robert G. Oler

    An agency in chaos. Its time for leadership

  • echos of the mt’s

    Short answer: Hubble is dying.

  • Kirk

    And with better leadership, that gyro would have failed back in 2014 when it should have. Damn NASA, always overbuilding things!

  • patb2009

    1)JWST is late. Maybe they get caught up, maybe they don’t.
    2) HST is getting long in the tooth. We can either let her run on single gyro, send a support tug to provide GNC support, abandon her.
    3) NASA took ownership of some stubby HST class birds from the NRO. Why aren’t those instrumented and flying?

  • echos of the mt’s

    They took ownership of 2 mirrors, not actual hardware. One if going on the Wide Field Infrared Survey Telescope (WFIRST). That is if it ever gets launched in 2024.

  • Robert G. Oler

    no with better plans they would have had a plan ready

  • duheagle

    Seems like waiting until it’s actually needed to check on the functionality of a backup unit wasn’t maybe the best idea. If the problem with the backup gyro had been known already, all this scrambling for a solution uploadable from the ground could have proceeded with less haste if started a long time ago. The solution – if one there is – could now be quickly applied instead of having to be invented under pressure.