Concern is mounting for NASA’s prolific Kepler exoplanet-hunting space telescope — a reaction wheel critical for stabilizing the spacecraft’s position is showing signs of increased friction, forcing mission managers to switch the mission into a 10-day “safe mode.”

“Earlier this month during a semi-weekly contact with the spacecraft, the team detected an increase in the amount of torque required to spin one of the three remaining reaction wheels,” said Kepler mission manager Roger Hunter in a mission update on Jan. 17. “Increased friction over a prolonged period can lead to accumulated wear on the reaction wheel, and possible wheel failure.”

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The internal reaction wheels are critical to maintain the position and orientation of Kepler, which continuously stares at one patch of our galaxy watching for slight dips in brightness of over 145,000 main sequence stars near the constellation Cygnus. These dips in brightness are caused by extrasolar planets — or exoplanets — passing in front of their host stars, blocking a fraction of starlight. Kepler then records these “transits,” allowing astronomers to detect exoplanetary candidates and, after more transits, alien worlds can be confirmed.

To date, Kepler has identified 2,740 exoplanetary candidates, with 105 of them being confirmed as real. It’s thought that 90 percent of Kepler’s candidates will be confirmed.

Unfortunately, if the reaction wheel glitch persists, the historic $600 million mission could be over. However, mission engineers hope that a 10-day rest for the space telescope will result in Kepler returning to normal duties.

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Following the failure of one of the four reaction wheels in July 2012, managers have already implemented measures to prolong the life of the remaining three and by resting them for 10 days, they hope that internal lubricants will be redistributed, allowing the troubled wheel to return to its low-friction state.

“Once the 10-day rest period ends, the team will recover the spacecraft from this resting safe mode and return to science operations. That is expected to take approximately three days,” Hunter added.

Image credit: NASA