Hubble Telescope in Safe Mode!
By Lora Snow
October 12, 2018
NASA put Hubble into safe mode on October 5 after one of its gyroscopes failed. Safe mode is a protective mode in which most of its instruments are turned off. It's designed to keep Hubble stable while ground control troubleshoots how to fix it.
Photograph of Hubble taken by astronauts on the final space shuttle servicing mission to Hubble in May 2009. Credit: NASA
When Hubble rotates, its gyros measure the direction the telescope is turning and the rate of that rotation. Therefore, the gyros are needed to help Hubble turn and point to new targets. The gyro that failed had been “exhibiting end-of-life behavior for approximately a year, and its failure was not unexpected, according to a statement by NASA on October 8.
Hubble actually has six gyros and only uses three of them at a time, but two of them had already failed,
Hubble's Pointing Control System. Credit: NASA
leaving four working gyros. When the most recent gyro failed, this left Hubble with two actively working gyros, and one in reserve. But when NASA powered on the gyro it had in reserve, it didn’t work properly. This left Hubble with only two working gyros.
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NASA personnel and other experts are trying to troubleshoot the problem. NASA said in a statement on October 12, that if they can’t get a third gyro to work, they will operate Hubble “in a previously developed and tested mode that uses just one gyro.”
NASA also said that if Hubble is using only one gyro, it would operate at slightly lower efficiency, but would still be able to “provide excellent science well into the 2020’s."
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