calstis -- Process STIS images (imaging and spectrum) through the different steps of the STIS Pipeline calibration.
- Input file name to be processed through calstis.
- (wavecal = "")
- Input raw wavecal file. If this value is null (the default), the name of the wavecal file will be gotten from the primary header of the input file, using keyword WAVECAL.
- (outroot = "")
- Root for output file names. If this value is null (the default), the output file names will be constructed from the input name. If outroot ends in "/" it will be interpreted as a directory, and the input file name will be appended and used as the basis of the output file names. Otherwise, the output file names will be constructed by appending such strings as "_flt.fits" to outroot (or if outroot ends in "_raw.fits", that string will be replaced by "_flt.fits", etc.).
- (savetmp = no)
- Save all temporary files created by calstis?
- (verbose = yes)
- Print time stamps at each operation as it takes place?
The task calstis provides routine calibration for STIS data. The task performs a 2-D image reduction (basic2d task), cosmic-ray rejection (crreject task, for CCD images only), 1-D extraction (x1d task), 2-D rectification (x2d task), and processes wavecals (wavecal task). By setting the appropriate switches in the primary header of the input image, either one or all of the functions specified above can be performed.
INPUT AND OUTPUT IMAGES.
The input STIS images are contained in extensions in FITS files, with three extensions in an image set: science (EXTNAME=SCI), error (ERR), and data quality (DQ). There may be multiple image sets (or imsets) in the input file, and if so calstis will read each imset, calibrate it, and write the resulting three extensions to the output FITS file. If performing cosmic-ray rejection (CRCORR = "PERFORM"), then the output file will contain only one imset (SCI,ERR,DQ).
The name of the output file is normally set by the task itself (but see outroot), by appending to the rootname of the input file the appropriate suffix that will indicate the last step in the calibration process that the file went through. The current output filename suffixes are:
- The flat fielded science data. The output file has been 2-D calibrated only (basic2d). This suffix is used for all MAMA observations. For CCD observations this file contains the individual imsets, that is, not CR-rejected or combined, but the DQ extensions indicate which pixels were identified as being affected by cosmic rays and rejected when summing to create the _crj file.
- The cosmic-ray rejected and flat fielded science data. Valid only for CCD observations that have been cosmic-ray rejected.
- _x1d (or _sxif CR-rejected)
- One dimensional extracted spectra. It is a binary table.
- _x2d (or _sxif CR-rejected)
- Two dimensional extracted spectra or geometrically corrected image.
REFERENCE FILES and PROCESSING STEPS
The names of the reference files (images and tables) to be used by calstis (and consequently by all the other processing tasks) are specified in the primary header of the input image, under the section CALIBRATION REFERENCE FILES. Refer to the help pages of basic2d, crreject, wavecal, x1d, and x2d for a complete explanation of the reference files and their related keywords in the primary header of the input image.
When an environment variable is used as part of a reference file name (e.g. "oref" in PFLTFILE = "oref$h230851ao_pfl.fits"), there are several points that should be borne in mind. The environment variable must be set in the Unix shell before logging into IRAF, and the directory name must include the trailing "/", e.g.:
setenv oref /data/reffiles/stdata/
Setting an IRAF environment variable oref will simply not work. If the reference files are in the default directory, oref can be set to ./ rather than editing the header to remove "oref$" from each of the reference file names. Furthermore, note that the file name is specified in the header using IRAF notation rather than Unix, i.e. "oref$h230851ao_pfl.fits" instead of "$oref/h230851ao_pfl.fits".
Input and output files to this task depend on which steps are set to PERFORM in the input parameter switches in the primary header of the input image under the section CALIBRATION SWITCHES. The acceptable input values for each switch are (PERFORM | OMIT | COMPLETE). COMPLETE has the same effect as OMIT. In the output image, those keywords which were set to PERFORM in the input image and for which processing was succesfully performed are set to COMPLETE.
The following switches are available:
- For basic 2-D image reduction (see help for basic2d):
ATODCORR BIASCORR DQICORR DARKCORR LORSCORR FLATCORR GLINCORR SHADCORR LFLGCORR PHOTCORR BLEVCORR
- Combine observations to reject cosmic rays (crreject). Available for CCD images only.
- Use wavecal to adjust wavelength zeropoint. Set it to PERFORM if wavecals will be used to determine the MSM offset.
- Perform 1-D spectral extraction. If set to PERFORM a 1-D spectral extraction will be performed.
- Rectify 2-D spectral image. If set to PERFORM the input image will be 2-D rectified.
- If set to PERFORM, the output 1-D extracted spectra and 2-D rectified images will be corrected for the earth's heliocentric velocity. Note that for medium and high dispersion, the Doppler shift due to the spacecraft velocity around the earth will already have been corrected by the on-board software.
- If set to PERFORM, the output 1-D extracted spectra and 2-D rectified images will be converted to absolute flux units.
- Apply dispersion solutions during 1-D extraction. (This step is always done for 2-D rectification.)
1. To calibrate CCD observations in the data set with the rootname "o3s40604o" with multiple images per file (i.e. CRSPLIT > 1 or EXTEND > 3). To perform basic 2-D image reduction and cosmic-ray rejection only. In this case the reference files are in the directory "/data/reffiles/stdata/". Note that we must have assigned oref as an environment variable before starting the cl, and the value must include the trailing "/". First set the appropriate switches in the primary header of the input file to PERFORM.
cl> show oref /data/reffiles/stdata/ cl> calstis o3s40604o_raw.fitsThe ouput file will have the suffix _crj (o3s40604o_crj.fits)
2. Calibrate the same file as in the previous example, but use "o3s40607o_wav.fits" as the wavecal, and write the output files in the directory above the default directory.
cl> calstis o3s40604o_raw.fits outroot="../" \ wavecal="o3s40607o_wav.fits"
Iraf task written by S. Hulbert. CALSTIS routines written by P. Hodge, J.C. Hsu, and I. Busko.