jointcal: Simultaneous Astrometry & Photometry for thousands of Exposures with Large CCD Mosaics

Abstract

The jointcal package simultaneously optimizes the astrometric and photometric calibrations of a set of astronomical images. In principle and often in practice, this approach produces distortion and thoroughput models which are more precise than when fitted independently. This is especially true when the images are deeper than the astrometric reference catalogs. In the “Astromatic” software suite, this simultaneous astrometry functionality is fulfilled by “SCAMP”. The code we describe here has similar aims, but follows a slightly different route. Jointcal is built on top of the the LSST Data Management software stack.