The Kepler Observatory (Telescope) fully assembled but without it's surrounding spacecraft support structures. The space observatory is named after the 17th century German astronomer Johannes Kempler. It's mission is to discover Earth-like planets orbiting other stars. It was launched on March 7, 2009, and remains active to this date. Kepler's only instrument is a photometer (pictured here) that monitors the brightness of over 145,000 main sequence stars in a fixed field of view. In this way any periodic dimming caused by extrasolar planets can be analyzed as they cross in front of their host star.