Corrects an EPIC-pn event list for spatial variations in the charge-transfer-inefficiency (CTI). This task should be run on the event file produced after all of the other CTI and gain corrections have been applied.
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 [2]. These can be represented, and corrected for, by a spatial CTI correction.
The task implements two methods for spatial CTI corrections: the original method as described in details in [1] and available via setting task parameter SD20method=N and the method in [3], described in details in [2] and activated with SD20method=Y.
The spatial CTI correction in the original method is derived from ground-based tests with
a number of laboratory X-ray lines, while the SD20 method is based on actual XMM-Newton observations using
the fluorescent copper line Cu K
at 8 keV (element=CU) and the
manganese line Mn K at 6 keV (element=MN) from the internal iron-55 calibration source,
available in CalClosed observations.
Due to the scarcity of CalClosed observations in Extended Full Frame (eFF) mode, it is not possible to derive a correction with element=MN for this mode. The results from copper indicate that the spatial offsets in FF and eFF are rather different and it is not advisable to use the FF-derived MN correction for eFF mode.
To avoid the corrections being applied twice, a keyword SPATCTIC is set in the header of the EVENTS extension when the task terminates successfully.
