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daydark -- Preparation of Daily STIS CCD Dark
daydark infiles basedark
- File name template for input dark file(s). This can be one bias-subtracted, cosmic-ray-rejected daily dark file (a file with "_crj" file suffix), or a list of "raw" dark files.
- Baseline superdark file (typically the most recent weekly delivery of the STIS superdarks; the user should retrieve it from the archive using e.g. bestref).
- (biasfile = "")
- Name of reference bias file to be used in calstis reduction (typically the most recent weekly delivery of the STIS bias files; the user should retrieve this file from the archive using e.g. bestref). If this parameter is left empty, the value of the BIASFILE keyword in the main header of infiles is used. This parameter is only relevant in case infiles is a list of "raw" dark files.
- (outfile= "day_dark.fits")
- Name of output daily superdark file
- (houstemp = INDEF)
- (Optional) CCD housing temperature(s) for these exposures. Note: The housing temperatures are only relevant for observations taken after July 2, 2001. The input format can be an array of numbers divided by commas, or a list identified as "@filename". If the default value INDEF is used, daydark uses the temperatures given in the header keyword OCCDHTAV of the science extension of each input dark file or imset. However, if a houstemp is given, houstemp will override those keyword values. The number of input temperatures in parameter houstemp should be equal to the number of input dark file imsets. If not, the action undertaken can be twofold: (i) If the header keyword OCCDHTAV is present in the science extension of the input imsets, the task will use those values; (ii) If OCCDHTAV is not present, the task will issue an error message asking the user to input a proper number of temperature values in parameter houstemp .
- (maxiter = 40)
- Maximum allowed number of iterations for statistics calculations
- (lower = INDEF)
- Initial lower limit for statistics calculations
- (upper = INDEF)
- Initial upper limit for statistics calculations
- (verbose = no)
- Show results of all iterations on statistics calculations?
- (print = no)
- Show final results of statistics calculations?
The main purpose of DAYDARK is to provide a daily update to the locations and intensities of the hottest pixels in the STIS CCD, by updating the hot pixels that are present in the "baseline" STIS CCD superdarks that are delivered weekly to the archive by those found in daily darks with a short exposure time. After running the DAYDARK script, the actual dark correction has to be done by running the calstis pipeline calibration (e.g., tasks calstis or basic2d ) on the "raw" STIS fits file (the file with "_raw" suffix) after having chosen outfile as the DARKFILE. (One has to use hedit to update the DARKFILE header keyword in the main (zeroth) header of the science file to be calibrated).
The task performs the following steps: (1) The input dark images infiles [typically STIS fits files with "_raw" file suffix] are first joined together into one multi-imset dark file. After that, the task checks whether cosmic ray rejection has already been performed for the file(s) specified as infiles . If so, the calstis step is skipped. If not, calstis will be run to perform bias subtraction and cosmic ray rejection. If the input data were taken after July 2, 2001, the individual bias-subtracted darks are scaled to a reference CCD housing temperature of 18 degrees C prior to summing them into one cosmic-ray rejected dark. The user is notified of the action(s) taken. If appropriate, the log file of the calstis reduction steps is written to output file calstis.log . [NOTE: Users wanting to create daily darks for STIS data taken before May 24, 1998, should retrieve the daily dark file taken in CCDGAIN=4 with _crj suffix (i.e., the "calibrated" image) to save time]. (2) The combined, cosmic-ray-rejected daily dark is normalized to yield intensity units of electrons per second. (3) Iterative statistics are performed on both the daily dark infiles and the "baseline" dark basedark [a file with "_drk" suffix, to be retrieved from the archive, to which it is delivered weekly], in order to neglect hot pixels. "New" hot pixels are defined as pixels having a value higher than 5 sigma above the median dark current of the normalized daily dark. The hot pixels in the baseline dark basedark are replaced by those in the daily dark (the "new" hot pixels). Pixels in the baseline dark having a value below the threshold of 5 sigma above the median dark current of the daily dark are NOT changed. Pixels that have "healed" themselves during the time between the "USEAFTER" date of the baseline dark and the exposure date of the daily dark are given the value of a median-filtered version of the baseline dark.
The result is a superdark with the signal-to-noise of the baseline dark in which the hot pixels have been updated. The level (in electrons per second) above which the pixels are updated is printed out.
INPUT AND OUTPUT IMAGES
The input file template infiles must contain one or more STIS FITS files, with three extensions: science (EXTNAME=SCI), error (ERR), and data quality (DQ). The output file outfile has the same format as (each of) the input file(s), and can be used in the other tasks in the STIS package. The file name of the baseline dark basedark is entered into the DARKFILE keyword in the main header of output image outfile .
1. Create daily superdark from input dark file o4at35010_crj.fits (from proposal 7802). Use "baseline" superdark file hcg14421o_drk.fits (retrieved from the archive).
cl> daydark o4at35010_crj.fits hcg14421o_drk.fits
2. Create daily superdark from input dark files o4wicfa3q_raw.fits, o4wicga8q_raw.fits, o4wichc9q_raw.fits, and o4wicicrq_raw.fits (from proposal 7948). Use "baseline" superdark file j331721ho_drk.fits and bias file j6m1312qo_bia.fits (both retrieved from the archive).
cl> daydark o4wic*raw.fits j331721ho_drk.fits \ >>> biasfile=j6m1312qo_bia.fits 3. Similar to example 1 (using different files), but now override the housing temperature data present in the header keyword OCCDHTAV of the science extension of all input imsets. .nf cl> daydark o6hm2*raw.fits m2f1636oo_drk.fits \ houstemp="17.80,18.10,18.05,17.85"
Task created by Paul Goudfrooij on July 6, 1999. Update for side-2 CCD data issued on April 26, 2002.