XMM-Newton Science Analysis System
badpixfind (badpixfind-1.37) [xmmsas_20070708_1801-7.1.0]
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- To quote fhelp cleansis (the ASCA equivalent routine) - Warning:
This is an analysis tool, not a program to run blindly: Clean, check, repeat.
- As regards how much of the badpixfind
routine can safely be
incorporated into the PPS, we believe that the number of bad pixels found by
may depend sensitively on the input parameters (thresholds
etc.). The task has been and is being developed so that an automatic running
(and importantly, usage in badpix) can be performed. Tests on many
datasets have been performed to find the most favourable parameter settings
(which will be different for MOS and pn). The default settings have been set
to reasonable values for MOS analysis. They are very conservative for pn
analysis however, a more favourable pn parameter setting being:
- The searching algorithms within badpixfind can be performed within
user-defined energy ranges. This will make any automatic usage of badpixfind
a little safer, the noiser, very low energy photons being ignorable. For PN,
the events are selected via their PHA values, for MOS, via their
- It is possible for a bad pixel map to be produced (with optionally, areas
outside the FOV masked out also). This is described
throughout the task description (see especially the user's description and the
parameters and examples section). This map can be fed into evselect
create `masked' images, lightcurves etc.
- Searching for `flickering' pixels is possible, as described
in the user's description. This, as with all of the mode 1 routines, must
not be used blindly - any number of effects could lead to a `flickering'
pixel (a bright source/feature passing briefly into the pixel, a genuinely variable
source, CCD edge effects etc). It is recommended that
a smallish number of flickertimesteps is used (5). Larger numbers
lead to lots more small number statistics and sometimes
(especially for MOS) very large arrays.
- It is believed that this task is inapplicable to timing and burst modes, and
will not be accessed.
- In obtaining the exposure information, for the pn, the LIVETIME
attribute is read. For MOS, the EXPOSURE attribute is read. In the case
of merged, calibrated event lists the LIVETInn attribute corresponding to the
appropriate chip is read for both PN and MOS.
XMM-Newton SOC/SSC -- 2007-07-09