Kepler Mission Schmidt corrector plate. The Schmidt corrector plate is located at the radius of curvature of the primary mirror and removes spherical aberration from the optical distortions. The corrector plate is made out of fused silica. 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. Photographed at a Ball Aerospace facility.