Hubble Telescope Put Into Safe Mode Following Gyroscope Failure


The nearly 30-year-old telescope is rapidly nearing its end of life.

The Hubble Space Telescope is in trouble. According to an update from NASA, one of the telescope’s gyroscopes has failed, leaving Hubble with only two working gyros. Until the problem has been fixed, the telescope has been put into ‘safe mode,’ suspending its scientific experiments. It’s unclear how exactly NASA is going to move forward, but this news likely means the venerable telescope’s days are numbered.

The Hubble Telescope has been surveying the cosmos for nearly 30 years, so it’s not surprising that some of its parts are getting old. In particular, the telescope’s gyros have often failed in the past, so having one fail now is not unexpected.

“The gyro lasted about six months longer than we thought it would,” said Hubble deputy mission head Rachel Osten in a tweet. “[We] almost pulled the plug on it back in the spring.”

The gyroscopes on Hubble are small spinning wheels that rotate the spacecraft and keep it stabilized. In space there’s no friction, so Newton’s Third Law of Motion is in full force: When the gyroscope wheels rotate one way, the entire rest of the spacecraft rotates in the opposite direction.

As some of the few moving parts on Hubble, these gyroscopes have a much shorter lifespan than the rest of the telescope. In fact, Hubble only needs three but comes with six just in case. The initial six gyros installed in the telescope when it was launched have even been completely replaced during the last service mission in 2009.

But with this latest failure, Hubble is down to only two reliable gyros. There is a third gyro that might be able to work, but last time NASA tested it there were some issues. The agency hasn’t released any info on next steps yet, but it’s likely they’ll try to fix the problems with this gyro before considering other options.

If that fails, chances are NASA’s next plan is to run the telescope with only a single gyro. With only one gyro Hubble is restricted in what parts of the sky it can look, because it can only rotate in one direction at a time. But Hubble will still be able to do some useful science, and dropping down to one gyro instead of two effectively doubles its lifespan.

“There isn’t much difference between 2 [gyros]and 1, and it buys lots of extra observing time,” said Osten. “The plan has always been to drop to 1-gyro mode when two remain.”

It’s crucial that Hubble remain operational for at least the next few years, because its replacement, the James Webb Space Telescope, has been delayed until at least 2021. If Hubble breaks down completely before that date, astronomers will be without a space telescope. That could delay crucial science for a few years at least, so hopefully Hubble still has plenty of life left.


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