In a press conference on Wednesday afternoon, NASA managers for the Kepler Space Telescope announced that their exoplanet hunter had suffered a major blow -- a loss of a second stabilizing (or reaction) wheel. The wheels help the telescope point to a place in the sky. Kepler has four wheels and needs three to work optimally. In 2012 it lost one reaction wheel. Without at least three working wheels the telescope places itself in "safe mode" -- which basically shuts most of the functions down on the craft to conserve fuel.
Managers of the mission tried their best to focus on the positive, the trillions of bits of data already collected and still being analyzed, and what further data might be gained should mission controllers be successful at reviving the sleeping telescope. "I wouldn't call Kepler down and out just yet," said NASA science chief and AAAS member John Grunsfeld.
Kepler is the first NASA mission capable of finding Earth-size planets in or near the habitable zone, which is the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water. Launched in 2009, Kepler has already identified 132 confirmed planets and 2,740 additional candidates yet to be confirmed.
AAAS Fellow Alan P. Boss of the Carnegie Institution of Washington, is an astrophysicist focused on the search for exoplanets. Boss has been helping NASA plan its search for extrasolar planets since 1988 and continues to be active in helping to guide NASA's efforts.
Boss shared his thoughts on this major setback with AAAS MemberCentral:
I only heard about this disaster as I was walking out my office door, taking a seminar speaker out for a dinner party in [Washington] D.C. I was a sad sack during the dinner party, I am sorry to say.
I am afraid that the loss of this second reaction wheel effectively means the partial loss of Kepler's main science goal: determining the frequency of Earth-sized planets orbiting their stars at distances such that liquid water could occur on the planets' surfaces. Kepler has taken an outstandingly impressive four years of data, but we still need another three or so years of outstandingly impressive data to be certain of the frequency of Earth-size planets. Right now we have enough data to make an intelligent extrapolation about what that number is, but that is not the same as actually determining that number. Kepler was planned to do that for us. There is no other mission in sight that can reproduce for us what Kepler was in the process of doing. The upcoming (2017) NASA TESS Mission will help to push the exoplanet field forward, but it is not designed to find Earth-like planets around sun-like stars, like Kepler was.
This is one of the saddest days in my life. A crippled Kepler may be able to do other things, but it cannot do the one thing it was designed to do.