Instruments on Hubble in safe mode; NASA is trying to understand why

The Hubble Space Telescope over Earth, photographed under STS-125, Service Mission 4, May 2009.
Enlarge / The Hubble Space Telescope over Earth, photographed under STS-125, Service Mission 4, May 2009.

On Monday, NASA announced that the Hubble Space Telescope’s scientific instruments were in an extended shutdown after problems arose in late October. The problems arose when incorrect internal communication caused the scientific instruments to switch to safe mode twice over a two-day period. Everything outside the instruments behaves normally, so the telescope is not in danger.

Earlier this year, Hubble spent an extended period in safe mode due to power supply issues that supply the primary payload computer. Because the power supply affected a variety of hardware, the problems were difficult to diagnose.

In this case, the problems seem to be simpler, at least superficially. The instrument package on Hubble uses an internal synchronization signal to ensure that everything is recorded at the same time, enabling instruments to respond to commands in the correct order. On October 23, one of these synchronization signals could not be detected, causing all the scientific instruments to go into safe mode. A simple reset of the instruments made everything work again.

But on October 25, the scientific instruments recorded the loss of several synchronization signals, and all went into safe mode again. Given the recurring and seemingly escalating nature of the problem, NASA has left the instruments in that state ever since.

NASA says its engineers are assessing the behavior of the instruments and reviewing Hubble’s hardware setup to find out what could be causing the problem. This information will be used to devise test procedures that will allow NASA to narrow down the culprits and come up with a repair procedure.

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