Two Broken Wheels Crippled NASA's $600 Million Telescope

NASAAn artist's rendition of the Kepler telescope, which ended its prime planet hunting mission. The $600 million Kepler space telescope ended its primary exoplanet hunting mission after two of four wheels that move and point the telescope were damaged beyond repair.

One of the wheels stopped working in July last year. With only three wheels the telescope could still maneuver enough to continue its mission. That only lasted another ten months, until the second wheel stopped functioning properly in May, when NASA officials noticed that the spacecraft was drifting off course.

Kepler was launched in March 2009 on a three-year mission to search for Earth-sized planets in our region of the Milky Way galaxy circling stars like our sun in the habitable zone — a distance that would allow that world to support liquid water.

The spacecraft began its four-year extended mission in November 2012. Throughout its time in space, Kepler confirmed 135 exoplanets, or planets outside of our solar system, and has a database of 3,548 planet candidates.

Kepler's exoplanet hunting mission is over, but the instrument is not dead. The telescope still works and astronomers have put out a call to find ways to use the spacecraft with its two operating wheels.

Back home, scientists expect to make hundreds of new discoveries as they comb through years worth of data collected by Kepler.