Despite a rest, Kepler’s problematic gyroscope is still having problems.

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Despite a rest, Kepler’s problematic gyroscope is still having problems.

Three of the wheels are needed for Kepler’s 3.1-foot telescope to have enough sensitivity to detect the minuscule signatures of Earth-sized planets. In an exercise of caution, mission managers switched off Kepler’s reaction wheels for 10 days in January, hoping the break would redistribute lubricant inside the wheel assemblies, reducing friction and allowing the units to cool down.

But friction in wheel no. 4, which has showed friction for much of Kepler’s mission, actually increased in the month following the “wheel rest” period.

The telescope originally had four wheels. One has failed, with a second showing signs of failure. If it goes, the spacecraft will no longer be able to point with enough accuracy to do its primary mission. They might be able to use it to some observations, but its design is such that even these will be of limited value.



  • The Hubble telescope also had lots of problems with gyroscope failures. It had six of them, and several of them were replaced during the Servicing Missions. According to the links below, two or four (Wiki says two, other link says two) gyroscopes were replaced in Service Mission 1 (1993), six were replaced in Service Mission 3 (1999), and six were replaced in Service Mission 4 (2009), That’s about one gyroscope every two years. If Kepler’s gyros die at that rate, it’s expected useful life would be 4 years. Did they have reasons to expect that Kepler’s gyros would last significantly longer? Given that Kepler’s orbit (40 million miles away) means that the telescope can’t be serviced, I wonder why they didn’t put a dozen gyroscopes in it. Hubble had six with three spares, but Kepler only had four, with one spare.

    Several years ago, I had an interesting conversation with someone on an airplane about the failing gyroscopes. The man next to me said that his son worked on the Hubble project, and he said that his son had some inside information about the failing gyroscopes. His son also had some strong opinions about this subject, but the man didn’t want to discuss the details in public. We were going get in touch afterwards to share the details with me, but, unfortunately, we were never able to contact each other afterwards. I’d love to learn more about the inside details of this subject.

  • wodun

    If only we had a space tug.

  • Pzatchok

    Shouldn’t this satellite be one of the easier ones to fix in orbit?

  • joe

    Maybe somthing with a canada arm hooked to would be able to snatch that thing and bring it inside for a tune up, Oh wait, its been dismembered!

  • Pzatchok

    Its one of the few satellites that doesn’t spin for stability, it uses those gyroscopic wheels that are failing.

    If they can’t get into the satellite to replace the wheels maybe they can strap on a new set and plug them into the computer system somehow, then just turn off the old ones.

  • Kepler is in an Earth trailing orbit. Rather than being a few hundred miles (354 miles, for Hubble), Kepler is millions of miles from Earth. For more information, see:

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