The Hubble telescope has three pairs of two gyroscopes, with each pair consisting of a primary and back-up gyroscope. All three are of a similar design, and NASA said it was not surprised that this third gyro failed. According to NASA, the gyro that failed last week had been exhibiting end-of-life behavior for about a year, and its failure was not unexpected.
"If the outcome indicates that the gyro is not usable, Hubble will resume science operations in an already defined "reduced-gyro" mode that uses only one gyro", Chou wrote.
Hubble's success is due in no small part to five servicing missions flown by space shuttle crews, including an initial visit in 1993 to fix the telescope's flawed optics and the final visit in 2009 that replaced the gyros and provided additional upgrades.
Now one of the remaining three isn't working as expected, leaving Hubble with just two working gyros and it needs at least three for optimal operations.
Only two of those enhanced gyros are now running.
"There isn't much difference between 2- [gyros] and 1, and it buys lots of extra observing time", tweeted Rachel Osten, the deputy mission head for Hubble at the Space Telescope Science Institute, late October 7.
The telescope, which travels the Earth at about five miles per second - equivalent to driving from America's East to West Coast in just 10 minutes - faces out to space to take pictures of planets, stars and galaxies to help scientists learn about the solar system. That extended lifetime is something the astronomical community "wants desperately", she added.
Gyroscopes are needed to keep Hubble pointed in the right direction during observations. Although science operations are expected to resume fairly soon, the current issues raise concerns about the future of the invaluable scientific instrument.