Kepler was launched on 7 March 2009. The primary objective of the mission was to survey a single area of the sky (in the direction of Cygnus) to determine the frequency of Earth-sized planets in the habitable zone of their parent stars. A secondary objective was to study the interior physics of stars via asteroseismology. Of course, the high photometric precision and nearly continuous observing window has enabled science across a wide range of astrophysics. The spacecraft has a wide, optical bandpass designed tomaximize the flux throughput from solar-like stars. On May 11, 2013, the spacecraft lost operation of a second reaction wheel, effectively ending the original mission. A second survey, called "K2", began in March of 2014 using the two remaining reaction wheels to balance with the solar wind. The K2 mission points at many different fields in the sky (called "Campaigns") along the ecliptic. Although it has worse precision that the original mission, it's still very good, and as a bonus, the trick of balancing the spacecraft with the solar wind forces the spacecraft to observe many different fields that include lots of interesting targets that were not observed with the original mission.
I'm a member of the "cloud-kepler" project (on GitHub
), an open-source project designed to find infrequent or aperiodic transit signals. Why look for such signals? Well, if they are "infrequent" then they probably have a very long orbital period and are likely to be missing from the mission's own catalog of planets. These long-period planets are very interesting, since they could be circum-binary exoplanets, exoplanets in the habitable zones of hotter stars, or planets orbiting at several AU that offer comparisions with the sample of closer, highly irradiated planets. If they are "aperiodic", then the planet is undergoing significant gravitational interactions with other bodies in the system, which allows for additional measurements (like masses) that can't otherwise be obtained from the photometry data alone. These planets are also likely to be missing from the mission catalog of planet candidates, since they don't have a strictly periodic signal that the mission pipeline looks for.