IRS Pipeline Masks

The masks described in this page are FITS files of 16-bit (integer) pixel type, unless otherwise noted. If the FITS file is 2-dimensional (one plane), it has 128 X 128 pixels. If it is 3-dimensional, it has 128 X 128 X n pixels, where n is number of frames or planes.

Bmask "BCD mask." 2-D. Stores pixel conditions encountered during a pipeline run. Created by imagest (mode 1) at about 2/3 into the pipeline, when the main input/output 3-D FITS file is converted to a 2-D plane (a slope image). Updated up to the end of the science thread. Uses the Dmask as input, masking conditions similar to the latter. However, sample-to-sample information is not retained. Instead, if one or more samples along a ramp are tagged in the Dmask, the corresponding pixel is tagged in the Bmask. Additional conditions tagged in Bmask (on a pixel-by-pixel basis) are: only one or zero samples were used to compute a slope; flatfield was not applied or was questionable; slremov or cross-talk was not applied; pixel masked in the Pmask. SOSDL-SIS-PD-3005
Dmask "DCE mask." 3-D. Stores pixel conditions encountered during a pipeline run. Created by cvti2r4 very early in the pipelines, and updated up to the point where the main input/output 3-D FITS file is converted to a 2-D plane (at about 2/3 into the pipeline). Typical conditions masked are saturation, radiation hits, data "missing" in downlink, uncorrectable non-linearity, etc. Each of these conditions can be identified sample-by-sample in the 3-D FITS file. SOSDL-SIS-PD-3001
Pmask "Pixel mask." 2-D. Masks semi-permanent bad pixel conditions. For the current IRS pipeline, only two conditions are masked: "Warm" pixels are those immediately adjacent to permanently hot pixels; some bleeding into them is evident in lab data. Bit # 9 is set for them. "Hot" pixels are saturated all the time, and are masked by setting bit # 14. Typically, a hot pixel is surrounded by ~4 "warm" pixels. There are typically a handful of hot pixels in each IRS array. SOSDL-SIS-CL-3005
Flatfield Cmask "Calibration mask for the flatfield." 2-D. Primarily, masks pixels outside the illuminated order regions of each array. More precisely, these pixels are outside the "expanded" wavesamp order regions. Created by the flatcal thread. Typically bit # 7 is set for masked pixels. The purpose of this mask is to prevent division of BCD signal by the flatfield, in regions outside the illuminated orders (actually slightly wider, by ~ 1 pixel, so as to avoid a sharp edge in the flatfielded orders). SOSDL-SIS-CL-3016
Dark Cmask "Calibration mask for dark-current." 3-D. Masks pixel samples where dark-current subtraction will not be done by the pipeline (cubesub module). Created by the darkcal ensemble thread (darkest module). Typically, bits # 11, 13 are set for masked pixel samples, meaning that a 2X2 boxcar average is too noisy, or that the pixel was masked by the Pmask, respectively. In the darkcal ensemble, an average dark frame is computed from several input darks. A peculiarity of the output ensemble Cmask (this mask) is that its values are independent of the input Dmasks of the various darks that went into the average. SOSDL-SIS-CL-3010
Lincal Cmask "Calibration mask for non-linearity model." 2-D. Masks pixels where correction for non-linearity in ramps will not be done by the pipeline (lineariz module). Created by the lincal pre-processing thread. In the lincal ensemble thread we simply apply a logical OR operation on the several input Cmasks, on a pixel-by-pixel basis. Typically, bit # 12 is set, meaning that the pixel was masked by the Pmask. SOSDL-SIS-CL-3003
(or Fmask)
"Field-of-View (FOV) mask." 2-D. This mask is an input to the 2-D coadder. Bits identify FOV to which a pixel belongs. Allowance is made for a pixel belonging to more than one FOV. The FITS header contains the correspondence of bit values and FOV identifiers. SOSDL-SIS-CL-3021
Amask "Coadd 2-D mask." 2-D. Produced by the 2-D coadder. The only conditions presently masked are: too few values were coadded for the pixel (currently < 3); pixel fatally masked in Bmask (flatap not applied; only one or no useable samples in the pixel ramp; masked in Pmask). SOSDL-SIS-CL-3020
QAmask "QATool mask." 2-D. This mask is an input to QATool (its last occurrence in the pipeline, for the BCD product). The purpose of this mask is to exclude fatally masked pixels in the P and Bmasks, and pixels outside the illuminated order regions of the array, during statistics computations by QATool. Created by the QAmask module, using as input Omask, Bmask, and Pmask. This module outputs, as QAmask, a mask similar to Omask, except that pixels fatally masked by the P and Bmasks are converted to zero. The fatal conditions are the most serious ones in P and Bmask: flatfield not applied for the pixel; only one or no useable samples in the pixel ramp; pixel is warm; pixel is hot. The resulting QAmask has values greater than or equal to 1 in the illuminated regions, and zero outside the regions or where a pixel is fatally masked. The module QATool will exclude from statistics any pixels whose QAmask value is less than 1. Not available
Lmask "Stray Light mask." 2-D. Used by the slremov module. The only two pixel values are 0 or 1 (exclude or include in computations, respectively). The "include" pixels are in the inter-order regions of the short-low array. These pixels define an "H-shape" region, where stray light is to be estimated by the module. In the absence of stray light, the "H-shape" region would be completely un-illuminated. SOSDL-SIS-CL-3013
Omask "Order mask." 2-D. Used by the module QAmask. Pixels within a given order have the value of the order number. Else (outside the orders) they are zero. SOSDL-SIS-CL-3017
Umask "Un-illuminated region mask." 2-D. Formerly, a rectangular box defined un-illuminated regions for statistics calculations by the modules droopres and darkbase. Now, the Umask defines such regions in between the spectral orders; there can be multiple such regions in a given IRS array. Values of pixels are 0 or 1 (1 is in desired un-illuminated regions). The Umasks do not consist of the entire inter-order regions, though. Instead, areas where stray light or optical cross-talk is significant were avoided. For example, very narrow areas in between closely spaced orders were avoided. SOSDL-SIS-CL-3012
Wavesamp_wmask Not available
Wavesamp_omask Not available
Wavesamp_offset mask Not available

Last updated: Aug. 29, 2003. Sergio Fajardo-Acosta.