Kepler mission: A mission to find earth-size planets in the habitable zone

The Kepler Mission is a NASA Discovery-class mission designed to continuously monitor the brightness of 100,000 main sequence stars to detect the transit of Earth-size and larger planets. It is a wide field of view photometer with a Schmidt-type telescope and an array of 42 CCDs covering the 100 sq. degree field-of-view (FOV). It has a 0.95 m aperture and a 1.4 m primary and is designed to attain a photometric precision of 20 parts per million (ppm) for 12^th magnitude solar-like stars for a 6.5-hour transit duration. It will continuously observe 100,000 main sequence stars from 9^th to 15^th magnitude in the Cygnus constellation for a period of four years with a cadence of 4 measurements per hour. The photometer is scheduled to be launched in 2007 into heliocentric orbit. A ground-based program to classify all 450,000 stars brighter than 15^th magnitude in the FOV and to conduct a detailed examination of a subset of the stars that show planetary companions is also planned. Hundreds of Earth-size planets should be detected if they are common around solar-like stars. Ground-based spectrometric observations of those stars with planetary companions will be made to determine the dependences of the frequency and size of terrestrial planets on stellar characteristics such as type and metallicity. A null result would imply that terrestrial planets are rare.