XMM-Newton Science Analysis System: User Guide

4.4.5 Correcting an EPIC-pn event file for spatially-dependent CTI effects.

As of SAS v12.0, the task epspatialcti allows to correct an EPIC-pn event file for spatially-dependent CTI effects. Measurements of the spectra of bright extended sources have shown that there is a pixel-to-pixel variation in the energy scale which is mainly caused by CTI changes due to partial trap saturation. epspatialcti corrects for this effect making the response much more uniform.

This task should be run on the event file produced after all of the other CTI and gain corrections have been applied. That is to say, on the event files produced by epproc or epchain. It is currently recommended to apply this correction for observations taken in FullFrame and ExtendedFullFrame modes. There is some evidence that it may also produce an improvement in LargeWindow and SmallWindow modes, however, it should not be applied for Timing mode or Burst mode observations.

The task implements two methods for spatial CTI corrections, both accesible via the task parameter SD20mode. By default, the Sanders et al. ([13]) method will be applied.

To avoid the corrections being applied twice, a keyword SPATCTIC is set in the header of the EVENTS extension when the task terminates successfully.