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calpolar stsdas.hst_calib.fos.spec_polar



calpolar -- Process calibrated FOS spectropolarimetric datasets.


calpolar input output badwp


The calpolar task performs the routine spectropolarimetric processing of FOS data and is equivalent to the special mode processing performed by the calfos task when the keywords "MOD_CORR=YES" and "GRNDMODE=SPECTROPOLARIMETRY". This task provides the additional freedom to manipulate or massage the flux calibrated data (the c1h file) prior to polarization processing and to exclude spectra at individual waveplate positions through the use of the task parameter badwp, which accepts a list of "bad" waveplate positions. Bad waveplate positions can be identified in individual datasets using the comparesets task. Also, multiple flux calibrated datasets for a given object can be averaged using the pcombine task, and then reprocessed with calpolar to recompute the polarization spectra from the averaged flux data.

The input data must be flux calibrated files (c1h), along with the corresponding wavelength (c0h), error (c2h), and data quality (cqh) files. The root names of all of these files must agree with the root name specified in the input parameter. The output of this task is an FOS special mode file (c3h) which is in the standard format of FOS polarimetry data files.

If the spectropolarimetry data were acquired during the post-COSTAR epoch as indicated by the Science header keyword/value pair, KYDEPLOY=T, and a post-COSTAR calibration file is available, the post-COSTAR polarimetry corrections will be applied. However, it should be noted that if no post-COSTAR polarimetry calibration file for the PCPHFILE calibration file keyword is provided, calfos will not abort. Instead, warning messages will be issued and the data in the output c3h file will still be calibrated, but the additional post-COSTAR correction will not have been applied.


input [file name]
The filename of the input FOS observation data set. If only the rootname is specified, then the extension is assumed to be c1h. Using the same rootname as the specified c1h file, the task also looks for the calibrated wavelength file, which must have the extension c0h, the calibrated error file, which must have the extension c2h, and the calibrated data quality file, which must have the extension cqh.
output [file name]
The rootname of the output FOS polarimetry data file. If no value is specified for this parameter, the default will be to use the value passed to input. The output file produced is the "special statistics" file which will have the extension c3h.
(badwp = "0") [string]
List of bad waveplate positions. Spectra from these waveplate positions will not be used in the calculation of the polarization spectra.


1. Perform polarimetry processing for the dataset y00vk108r. All files for this dataset are in the directory spec$. Output files are to have the same root name as the input files.

  sp> calpolar spec$y00vk108r ""

2. Process the dataset y00vk901r and produce output files with a root name of test186 in the subdirectory temp. Exclude waveplate positions 7 and 8 from the processing.

  sp> calpolar y00vk901r temp/test186 badwp="7,8"


Version 3.2 (May 1999) of calpolar incorporates changes to the way that post-COSTAR POLSCAN = 4 data is processed. No post-COSTAR instrumental polarization correction can be made for this data. Consequently, the results contain significant instrumental polarization. Please refer to FOS Instrument Science Report 150 for a discussion of the magnitude and uncertainties of instrumental polarization introduced by COSTAR.


Author: Howard Bushouse, STSDAS


For assistance using this or any other tasks, please contact or call the help desk at 410-338-1082.


calfos, comparesets, pcombine, plbias, polbin, polnorm

Type "help spec_polar opt=sys" for a tutorial on FOS polarimetry.

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