Partway through DM-18417, it became clear that illumination correction appears to be needed to eliminate false positive sources from difference imaging on nights with high sky brightness. While illumination correction is a standard step in the DECam community pipeline (CP), and "illumcor" CP data products exist for the HiTS2015 dataset, we have never used them with the LSST Science Pipelines.
This ticket is to add the ability to ingest, and subsequently use during ISR, the illumination correction calibration products provided by the DECam community pipeline. They are multi-extension FITS files much like the "cpBIAS" and "cpFLAT" masterCals we have been using, and should be able to be ingested and used in a similar way.
There will be Mappers.