Astrometry with PRAIA

PRAIA - Package for the Reduction of Astronomical Images Automatically - is a suite of astrometric and photometric tasks designed to cope with huge amounts of heterogeneous observations with fast processing, no human intervention, minimum parameterization and yet maximum possible accuracy and precision. It is the main tool used to analyse astronomical observations by an international collaboration involving Brazilian, French and Spanish researchers under the Lucky Star umbrella for Solar System studies. In this paper, we focus on the astrometric concepts underneath PRAIA, used in reference system works, natural satellite and NEA astrometry for dynamical and ephemeris studies, and lately for the precise prediction of stellar occultations by planetary satellites, dwarf-planets, TNOs, Centaurs and Trojan asteroids. We highlight novelties developed by us and never reported before in the literature, which significantly enhance astrometry precision and automation. Such as the robust object detection and aperture characterization (BOIA), which explains the long standing empirical photometry/astrometry axiom that recommends using apertures with 2 - 3 sigma (Gaussian width) radius. We give examples showing the astrometry performance, discuss the advantages of PRAIA over other astrometry packages and comment about future planed astrometry implementations. PRAIA codes and input files are publicly available for the first time at: https://ov.ufrj.br/en/PRAIA/. PRAIA astrometry is useful for Solar System as well as astrophysical observations.