Kepler Mission space telescope, artwork. The Earth and the Moon are at centre right. The Sun is at bottom left. An alien star and planets (distance not to scale) are at top left. NASA's Kepler Mission is designed to discover Earth-like planets orbiting other stars. A 0.95-metre diameter telescope called a photometer will scan 100,000 stars in the Milky Way for evidence of Earth-sized terrestrial planets that transit the star's path. The mission was launched on March 7th, 2009, and will orbit the Sun for at least 3.5 years. The mission is named in honour of German astronomer Johannes Kepler.