Spitzer Documentation & Tools
IRS Instrument Handbook

5.3  Description of Modules in the Dark Calibration Pipeline (Creation of dark.fits)

This pipeline consists of two parts. First, individual input files raw.fits are processed through a pipeline that is a subset of the BCD one. This pipeline is denoted as Dark Calibration Pre-processing. Second, multiple pre-processed products are combined through an ensemble pipeline, to yield one output dark calibration file. See Figure 5.9.  The selection of files to be combined in the ensemble is done manually; the names of these files are contained in lists in text format. The products described in this section are not available in the Spitzer Heritage Archive, but can be generated by running CUPID.

Figure 5.9  Dark Calibration Pipeline Flow Chart. This pipeline consists of two steps: Pre-processing, up to DARKBASE, and ensemble processing, which combines several DARKBASE outputs (drk.fits). The figure above illustrates the case of three drk.fits that are combined to produce the output dark.fits.

5.3.1             Dark Calibration Pre-Processing Pipeline

The input file raw.fits is processed through the modules CVTI2R4, SNEST_IRS, DNTOFLUX, RADHIT_SAT, SATCOR, DROOPOP, ROWDROOP, and DARKBASE. The modules and their execution are exactly as described in Section 5.1. The outputs of this pipeline are drk.fits, drku.fits, and dmask.fits

5.3.2             Dark Calibration Ensemble Pipeline

This ensemble pipeline consists of only one module, DARKEST. Multiple input drk.fits files are combined.       DARKEST

The module DARKEST (“Dark Estimator”) computes the median of several input files drk.fits, whose names are listed in the text file filelist_flux.txt. Other inputs to the module are the corresponding uncertainty files drku.fits and DCE masks dmask.fits, respectively listed in the text files filelist_unc.txt, and filelist_dmask.txt. These input lists are made manually by the user.

The processing of each pixel is done independently of other pixels. The module computes the median of the input files drk.fits.  The output is dark_flux.fits.  This file can be used in subsequent BCD pipelines, as shown in Figure 5.2, during the operation of the module CUBESUB.

The output dark calibration mask, dark_cmask.fits, has bit # 10 set if the spatial standard deviation in a 2×2 pixel2 boxcar exceeds a threshold. Bit # 13 is set whenever a pixel is fatally masked in the pmask.fits of the corresponding instrument channel.