NASA's planet-hunting telescope, Kepler, has been having problems over the past year, and it looks like it's suffered another failure that may put the future of the mission at risk.
Kepler trails after the Earth as we orbit the Sun, constantly pointing at a collection of stars near the constellation Cygnus, watching those stars for 'transits' — when a planet passes in front of the star, causing us to see the star's light dim. The telescope stays focused on those stars by using a collection of 4 wheels that rotate its mirrors, thus conserving fuel that would otherwise be needed to adjust the telescope position. It can operate with only three of the four wheels, but one wheel (#2) had already completely failed last year, and it appears as though another one, #4, which had also been giving them trouble lately, has now failed too.
When the mission team contacted Kepler for an update on Tuesday, May 14th, they found the telescope in safe mode, where it uses its thrusters to keep its mirrors steady. Switching it back to normal operations, they tested the wheels and all indications were that the troubled wheel had failed completely. The team returned the telescope back to safe mode and are now looking into other options for recovery.
With this failure, the future of the mission may be in jeopardy, and there is already some pessimism circulating about this. However, it's far too soon, at the moment, to call it quits on Kepler.
Having the telescope's reaction wheels working is certainly the ideal situation, but that was simply to keep the mission going as long as possible. Without the wheels, it will simply need to use fuel to keep its mirrors steady, and according to the Kepler team, they have enough fuel for several months.
Also, according to the NASA press statement, they can use a newly programmed 'Rest Point State' mode, which can extend those months into years. Rest Point State "is a loosely-pointed, thruster-controlled state that minimizes fuels usage while providing a continuous X-band communication downlink."
As New Scientist writer Lisa Grossman tweeted, quoting Kepler principle investigator William Borucki during the NASA teleconference:
Borucki: @nasakepler probably has habitable Earths in existing data. "most interesting and exciting discoveries are coming in the next 2yrs"
— Lisa Grossman (@astrolisa) May 15, 2013
So, this isn't the greatest news to get about the Kepler mission, but it's not over yet and the Kepler team certainly hasn't bought in to the pessimism.
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As of February, the telescope has already revealed 114 confirmed planets orbiting other stars ('exoplanets'), plus there are another 2,740 'candidates' that have yet to be confirmed by other observations, and those results represent only a fraction of the data that Kepler has gathered so far. Ground-based telescopes are working to confirm the candidate planets, and the Kepler team and citizen science efforts like Planet Hunters are still going through the data to find more.
So, even if the telescope were to completely and irretrievably fail, they still have enough data from the past four years to keep them busy with new discoveries, possibly some of the most important discoveries yet to come.
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