XMM-Newton Science Analysis System


emproc (epicproc-2.20) [xmmsas_20160201_1833-15.0.0]

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Bad Pixels

emproc has a more sensitive algorithm for bad pixels detection which is embadpixfind (refer to this tash for further information). This task has been developed for finding bad pixels in an EPIC-MOS image in a completely automatic way.

If part of the exposure is affected by flares, this can seriously reduce the power of the bad pixels search (flares act as noise for the bad pixels and make detecting them more difficult). Therefore an intermediate flare screening is necessary (Fig ). The bright pixels (which can perturb the flare screening) are flagged using ebadpixupdate. The resulting files are used to generate Good Time Intervals outside flares. Then the bad pixel search is run a second time on the data outside flares, in incremental mode.

Before applying this flare screening, we check the data quality inspecting the field of view value of each CCD (GATTI flare screening in Fig 3.1). If we obtain a value greater than 3 arcmin, we consider that the flare screening can be applied.

For embadpixfind the algorithm is called a third time (incrementally) on energies below 500 eV (and after flare screening), unless findlowener=N. This sometimes detects bad pixels more easily, because most appear at low energy.

Parts of the observation can be excluded from the search for bad pixels by giving emproc an additional GTI file via the parameters withbadpixgti and badpixgti.

For instance:

emproc withbadpixgti=yes badpixgti=mygti.ds