K2

K2 was the name of a mission reusing the Kepler spacecraft for additional similar science. The K2 mission ran from 2014 until 2018 after which Kepler was retired, having run out of fuel. As before, K2 monitored stellar brightness to detect transits as well as other uses of such observations. Kepler's primary mission had terminated due to equipment failure, leaving too few working reaction wheels to maintain the direction it was pointed at. K2 used the remaining reaction wheels along with solar radiation pressure to control its direction, with somewhat less precision but sufficient to produce results. The regions of the celestial sphere in which this method was workable were limited and depended upon the spacecraft's position in relation to the Sun, which shifts over the course of its orbit. To make use of the workable regions, K2 monitored selected survey fields for limited periods of time.

Among its projects were surveys for transits across nearby M dwarfs (M-type star, red dwarf). This is similar to the TESS mission, but K2's sensitivity and reach were different than TESS's and K2 carried out longer observation periods, since TESS is dedicating its limited time to covering more of the sky.

EPIC stands for Ecliptic Plane Input Catalog, a catalog of stars chosen for K2 observation.