MAY 8, 2009

CALCOS v2.8.2 Release Notes

Relevant Trac tickets and PRs:

Trac PR Updates
394 62433 Modify wavecal processing in CALCOS.
401 62440 For CALCOS, add the option to bin a csum image.
406 62590 In CALCOS, revise the code for the dispersion relation.

Overview

  • There are four new command-line options, to compress and/or bin the csum image and to allow the user to provide a text file to override wavecal shifts in the dispersion direction.
  • Wavecal processing has been modified. Chi square minimization is now used instead of cross correlation to find the shift in the dispersion direction. Two values of this shift are now printed (they're usually the same); one is the value originally determined (labeled "orig."), and the other is the one that will be applied. The latter could be based on an average of the shifts of the other stripes, or it could have been overridden by the user (see below).
  • The new command-line options are:

  --compress parameters (compress csum image)
  --binx X_bin_factor (csum binning in X)
  --biny Y_bin_factor (csum binning in Y)
  --shift filename (file to specify shift values)

The first three are for the csum file. The fourth gives you the option to specify the shift in the dispersion direction, overriding the value that calcos finds.

The csum image (either FUV or NUV) may be binned in either the X (dispersion) or Y axis (but not in the PHA axis). If 'binx' or 'biny' is not specified, the default binning for that axis will be used; currently the default binning is 1, i.e. no binning. Independently of binning, the csum image may be compressed (this uses the pyfits on-the-fly compression option). The compression parameters are given as a string consisting of two components separated by a comma; the default value is "gzip,-0.1". The first part is the compression type, which may be "gzip", "rice", or "hcompress". The second part is the quantization level, which specifies how the floating-point image values are to be converted to integer before compression. If the quantization level is positive, it is interpreted as a value relative to the RMS noise level in the image background; a value of 16, for example, means that the quantization level will be 1/16 of the noise level. If the quantization level is negative, it's the actual floating-point increment that corresponds to a difference of one in the scaled integer image. The compression in pyfits supports other parameters such as tile shape, and parameters for hcompress, but these are not currently supported in calcos. The shift file (option --shift filename) may be specified in order to override values of the wavecal shift (shift1a, shift1b, shift1c) in the dispersion direction. This is a text file with five columns:

rootname   fpoffset   flash number   segment/stripe   shift1

The first four columns are used for identifying which particular lamp exposure is to be overridden; however, any or all of those columns may be given as "any" (without quotes), which matches any value. All strings are case insensitive. Blank lines and lines beginning with "#" will be ignored. A single shift file can be used for an entire association; that's why rootname is included as a selection criterion. The rootname in this context is the portion of the file name that precedes the suffix. The rootname is taken from the actual name of the raw file, rather than from the ROOTNAME keyword, so that if the raw file has been renamed without changing the keyword, the name in the shift file will be the name that most people would expect. It is redundant to specify both rootname and fpoffset. Both are included to make it easy to set shift1 to the same value for all rootnames for a given fpoffset. If rootname is specified, fpoffset can be given as "any", and vice versa.

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