Can we rescue Kepler, exoplanet search? NASA says it's worth a try

A NASA team began efforts to revive the ailing Kepler telescope on Thursday, sending commands to two failed "reaction wheels" that help the craft focus its equipment on distant stars.

According to a NASA statement, engineers tested one of the failed wheels -- reaction wheel 4, which failed in May. The team members found they could get the wheel to spin counterclockwise, but not clockwise. Kepler project manager Roger Hunter called the result "an interesting development," but stressed that it would take more tests to figure out whether it would be possible to get Kepler's reaction wheels working again.

He added that tests on wheel 2, which stopped working in July 2012, would take place on Monday.

According to an article Thursday by Discovery News, wheel 4 was considered the more seriously damaged of the two. Charlie Sobeck, deputy project manager at NASA’s Ames Research Center, said scientists worked on the balkier wheel first because they hoped to "learn any lesson on the wheel that’s less likely to respond, and then we’ll move on to the better bet."

Kepler monitors a small patch of sky in the Milky Way in search of small dips in the light coming from stars. The dips can indicate that an orbiting planet is passing between the star and Kepler.

As my colleague Amina Khan reported in May, the telescope can't focus well without three functioning reaction wheels -- it needs a different wheel to control its movement in three different axes.  When wheel 4 stopped responding to commands this spring, it left Kepler with only two working wheels, and therefore "essentially useless for hunting planets by watching for their transits in front of stars."

At the time, even as NASA began thinking about a recovery effort, scientists mourned Kepler, which had at that point found more than 2,700 candidate and 132 confirmed planets since its launch, in 2009. "Tears are coming to my eyes on and off," UC Berkeley astrophysicist and Kepler co-investigator Geoff Marcy said at the time. "I really think this telescope was a gift to our civilization."

Even if Kepler can no longer look for exoplanets, Khan wrote, NASA officials have stressed that it is possible the instrument could have as-yet-undetermined scientific uses.

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