NASA announced a failure of the Kepler space telescope. A reaction wheel no longer works. It’s a type of flywheel that’s part of a gyroscopic system that allows to point the observatory with very high precision without using its thrusters. This is a big problem that threatens to put an end to the Kepler mission, at least the one carried out for four years.

Launched on March 7, 2009 on a Delta II rocket, the Kepler space telescope has found more than 2,700 candidate planets, meaning observations of stars that could have planets. 130 of those candidates have been confirmed and as always in these cases the amount of data is really huge and it will take years to perform all the analyzes.

The mission of the Kepler space telescope was supposed to last three and half years. In November 2012 it was extended until 2016 because the observatory was working properly. Unfortunately, now the mission will probably be interrupted due to the failure of one of the reaction wheels.

Kepler has four reaction wheels that were part of a very precise and sophisticated pointing system. They are powered by the energy generated by the solar panels therefore this system can operate for an indefinite time. The pointing system needs at least three reaction wheels to function properly and last year one of them had already failed.

The second reaction wheel started giving problems during this year. Unfortunately, these devices suffer from mechanical friction problems that over time can cause a failure and NASA has a team of engineers who develop new solutions to prolong their life. This type of system is in fact used on various spaceships therefore Kepler’s problem isn’t isolated.

In the course of May Kepler entered twice the so-called “safe mode”, meaning it stopped its operations in response to an abnormal situation to avoid worse damage. In recent days, an attempt to reorient the space telescope has shown the impossibility of moving the reaction wheel that was already causing concern.

NASA has approved Kepler’s transition to the so-called “Point Rest Mode”, basically a parking mode where the space telescope is stable with a low fuel consumption while they decide what to do with it. The Kepler space telescope is in orbit around the Sun, not around the Earth, so even if the Space Shuttle’s were still operating it would be impossible to go to fix it.

One possibility is to try to reactivate the reaction wheel that failed last year hoping that in the meantime the lubricant redistributed restoring its functionality enough for the pointing system to work. Another proposal is to use the thrusters along with the remaining reaction wheels and possibly take advantage of the pressure from the solar wind, the problem is to obtain adequate pointing precision.

It’s also possible that Kepler will be used in other ways that don’t require great  pointing accuracy but that would mean that its days as a “planet hunter” are really over. It would be a shame but in the worst case scenario its mission was a great success.

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