D3.7.3 Software to Output Metrics That Keep Track of Improvements to the Pipeline Sky Subtraction

Aaron Watkins, Chris Collins, Sugata Kavira

Low surface brightness science contains much of the potential discovery space for LSST, in galaxies, solar system, and Milky Way research. Unfortunately, the authors (i.e. LSST:UK work package WP3.7) have previously demonstrated that the current LSST data reduction pipeline’s sky subtraction routine over-subtracts flux in the outskirts of extended objects, making low surface brightness science with LSST a potentially very difficult enterprise. Changes to the pipeline are thus required to ensure that LSST’s scope is not limited in this way. As WP3.7 develop an alternative sky-subtraction routine to resolve this issue, it is necessary to track improvements using quantitative metrics. This in turn requires software that can measure and output these metrics alongside regular runs of the pipeline. This report details the current state of such software, which WP3.7 are now making available to the LSST:UK community. The authors also describe future plans for the software, to address its current slow speed and to more easily integrate some version of it into the LSST pipeline itself for use by the data management team.