The Derivation, Properties, and Value of Kepler’s Combined Differential Photometric Precision

The Kepler Mission is searching for Earth-size planets orbiting solar-like\nstars by simultaneously observing >160,000 stars to detect sequences of transit\nevents in the photometric light curves. The Combined Differential Photometric\nPrecision (CDPP) is the metric that defines the ease with which these weak\nterrestrial transit signatures can be detected. An understanding of CDPP is\ninvaluable for evaluating the completeness of the Kepler survey and inferring\nthe underlying planet population. This paper describes how the Kepler CDPP is\ncalculated, and introduces tables of rms CDPP on a per-target basis for 3-, 6-,\nand 12-hour transit durations, which are now available for all Kepler\nobservations. Quarter 3 is the first typical set of observations at the nominal\nlength and completeness for a quarter, from 2009 September 18 to 2009 December\n16, and we examine the properties of the rms CDPP distribution for this data\nset. Finally, we describe how to employ CDPP to calculate target completeness,\nan important use case.\n