The Kepler spacecraft is an American space observatory, the space-based portion of NASA's Kepler Mission to discover Earth-like planets orbiting other stars. The spacecraft, named in honor of the 17th-century German astronomer Johannes Kepler, was launched in March 2009 with a planned mission lifetime of at least 3.5 years; in 2012, the mission was extended to 2016. The Kepler mission is specifically designed to survey a portion of our region of the Milky Way galaxy to discover dozens of Earth-size planets in or near the habitable zone and determine how many of the billions of stars in our galaxy have such planets. Kepler's only instrument is a photometer that continually monitors the brightness of over 145,000 main sequence stars in a fixed field of view. This data is transmitted to Earth, then analyzed to detect periodic dimming caused by extrasolar planets that cross in front of their host star. Kepler is a project under NASA's Discovery Program of relatively low-cost, focused science missions. Construction and initial operation were managed by NASA's Jet Propulsion Laboratory, with Ball Aerospace responsible for developing the Kepler flight system. The Ames Research Center is
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