Kepler Telescope Idled by Balky Reaction Wheel

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Science operations for NASA’s exoplanet-hunting Kepler telescope were suspended Jan. 17 when the spacecraft was placed into a 10-day safe mode to evaluate a balky reaction wheel, mission manager Roger Hunter wrote in an online post.

“This is similar to a normal safe mode configuration, but with thrusters maintaining attitude instead of reaction wheels,” Hunter wrote. “Resting the wheels provides an opportunity to redistribute internal lubricant, potentially returning the friction to normal levels.”

Spinning reaction wheels allows spacecraft controllers to change a spacecraft’s orientation.

According to Hunter’s note, controllers noticed earlier this month that one of Kepler’s three remaining reaction wheels required an unusually high amount of torque to turn. The craft was built with four reaction wheels, one of which failed in July.

After the 10-day rest period, the Kepler team will begin the three-day process of returning the telescope to operational mode. Science observations will resume then, at which time the Kepler team will post another mission update, Hunter said.

The $150 million Kepler telescope, built by Ball Aerospace & Technologies Corp., launched in 2009 and wrapped up its three-and-a-half year primary science mission in 2012. Extended mission operations, which are supposed to run through late 2016, began in November.

Kepler is searching for signs of Earth-like planets in other solar systems. The telescope looks for the tell-tale flicker that occurs when a planet transits — or passes in front of — its system’s star. According to Kepler mission parameters, three such transits are required before astronomers will consider the possibility that they have discovered a new planet.

According to a Jan. 7 NASA press release, sent the same week astronomers gathered in Long Beach, Calif., for a meeting of the American Astronomical Society, Kepler had discovered 105 potential planets, up from 33 potential planets in early 2012.