MOPEX Online Manual
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Modules: Detect Radhit
Namelist Trigger: run_detect_radhit
Output Directory Keyword: DMASK_DIR
Default Output Directory: <output_dir>/Dmask/
Depends on: Input files
Important Notes: This module is not normally required for Spitzer data, as it has already been run by the SSC when creating the BCD frames that users download from the Spitzer archive.
If overwrite_Dmasks = 1 is set in the Mosaic namelist, MOPEX will overwrite the input mask files rather than creating new masks.
Output Directory Keyword: DMASK_DIR
Default Output Directory: <output_dir>/Dmask/
Depends on: Input files
Important Notes: This module is not normally required for Spitzer data, as it has already been run by the SSC when creating the BCD frames that users download from the Spitzer archive.
If overwrite_Dmasks = 1 is set in the Mosaic namelist, MOPEX will overwrite the input mask files rather than creating new masks.
PURPOSE
-
This module does single frame radhit rejection. It is the simplest of
the outlier rejection
schemes. Bright detections with small areas are classified as radhits.
By default, single frame radhit rejection is already run during the
Spitzer MIPS and IRAC BCD pipeline processing. The radhit pixels are
flagged in the status masks provided with the BCD products. So if
DCE_STATUS_MASK_LIST is specified in the namelist, this module
does not need to run again if the masks are satisfactory.
PARAMETER BLOCK
-
&DETECT_RADHIT
Segmentation_Threshold = 3,
Detection_Max_Area = 3,
Radhit_Threshold = 10,
&END
INPUTS
Segmentation_Threshold: (float) The number of sigma above the mean to be used as the initial threshold used for cluster detection.
Detection_Max_Area: (int) The maximum number of pixels in a connected area (cluster) which could be classified as radhits.
Radhit_Threshold: (float) In order to classify a cluster of pixels as a radhit, at least one of the pixels should be greater than this threshold in sigma. This parameter should be set much higher than the segmentation threshold value.
OUTPUTS
-
New DCE Mask Files (*_dmask.fits): Once the radhits are detected,
this module will either produce mask images containing radhit pixels, or update the input masks if overwrite_Dmasks = 1 is set in the namelist (see the discussion below, and Mosaic Namelist Options for more information on the overwrite_DMasks trigger). These flagged pxels are rejected
by setting Bit 9 in the DCE_Status_Mask_Fatal_BitPattern (see Appendix 2: Fatal Bit Patterns for more information).
DISCUSSION
The first and most basic method of outlier rejection is the single frame outlier detection that represents spatial filtering of input images. It is performed on the input images. In the automated MIPS and IRAC pipelines, this step is included in the standard BCD processing. It is designed to detect relatively bright and spatially small radhits. The algorithm is a variant of image segmentation, and is based on the idea that when a relatively low detection threshold is applied, for each bright point source a large number of pixels will be detected above the threshold. Bright detections with small areas are, therefore, classified as radhits. The output of this module depends on the trigger overwrite_Dmasks, set in the Global Parameters section of the Mosaic namelist. The default value is 0, which will instruct MOPEX to create new mask files. If set to 1, MOPEX will overwrite the input mask files rather than creating new ones. The input masks are specified in the Input Files part of the namelist, with the keyword DCE_STATUS_MASK_LIST, and are not necessarily actually called *dmask.fits (in fact, we recommend using the IMasks with IRAC data).| Contents | ~ | Previous: Mosaic Modules - MedFilter | ~ | Next: Mosaic Modules - Fiducial Image Frame |
