Kepler Mission's field of view, diagram. 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. This is an example of how it analyses a targeted star field. 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.