Determination and correction of the charge transfer efficiency of the pnCCD camera

In CCDs part of the charge released by an absorbed photon is lost during transfer to the readout node. This loss depends on several parameters, in particular on the position where the photon was detected, its energy, the temperature of the CCD, and the saturation of traps by charges preceding along the readout direction. In order to determine how these parameters affect the charge loss of the pn-CCD cameras, we obtained extensive sets of calibration measurements from February 1998 to January 1999. More than three billion events were recorded in flatfield exposures. We present results of a detailed analysis of this data set and describe how they can be used to correct pn-CGD camera, data for charge transfer loss.