Launched in 2009, the Kepler Mission is surveying a region of our galaxy to determine what fraction of stars in our galaxy have planets and measure the size distribution of those exoplanets. Although Kepler completed its primary mission to determine the fraction of stars that have planets in 2013, it is continuing the search, using a more limited survey mode, under the new name K2.

KOI is the Kepler Objects of Interest catalog listing observed Kepler targets which are flagged as potentially having exoplanets but may be false positives caused by other types of transient detection. This catalog is produced by the Kepler project and brought to MAST via NExScI.