The SWIFT BAT Software Guide Version 6.3 30 ... - HEASARC - Nasa

150 APPENDIX D. BAT SOFTWARE TOOL REFERENCE
D.11 BATHOTPIX
D.11.1 NAME
bathotpix - locate and mask out hot pixels in a BAT detector image
D.11.2 USAGE
bathotpix infile outfile
D.11.3 DESCRIPTION
bathotpix locates hot pixels in a BAT detector plane image. Hot pixels can be a source of noise in
subsequent image processing steps, and so should usually be excised.
This tool uses a histogram-based approach to locate the hottest and coldest pixels in the image.
Given a distribution of counts, the “centermost” portion is selected as being good (the “keepfract”
amount). If keepfract is 0.98, then 98% of the detectors are selected as good. The selection window
is further enlarged by bands on either side using the guardfract and guardval parameters. Values
outside the selection window are considered to be “cold” (too low) or “hot” (too high).
The output of the tool is a quality map of the same dimensions as the detector image. Values
stored in the map are determined by the keywords below, but typically a value of 0 indicates a good
pixel. This mask can be input into downstream image processing stages. The second extension,
BADPIX, is a binary table containing a list of bad pixels.
Users can submit an existing detector mask using the detmask parameter. Pixels with bad
quality are ignored by bathotpix in computing the distribution and selection windows. By default,
the input mask is logically AND’d with the result, so that the output is the cumulative record of
excised pixels. By default, BAT detector gaps are also excised.
D.11.4 PARAMETERS
infile [filename ]
Input file name containing a detector plane image.
outfile [filename ]
Output detector mask image.
(detmask = “NONE”) [string ]
Input detector mask image. Pixels with bad quality are ignored in the bathotpix analysis.
(row = 1) [integer ]
Image number to process, where the first image is number 1. This applies both to files with
multiple image extensions (where ‘row’ selects the extension number) and to files with one
binary table extension (where ‘row’ selects the table row).