Redução de imagens astronômicas obtidas a partir do solo: preparando-se para a astrometria da missão espacial Gaia.

Abstract

This work aims at contributing to a more refined ground-based astrometry from the PRAIA code (Platform for the Reduction of Astronomical Images Automatically), more specifically, that of small solar system bodies. Such refinement is now possible thanks to the results of the Gaia space mission that will provide, until its end (2019+), astrometric accuracies reaching the microarcssecond. This leads us to a new scenario, where the errors from ground-based astrometry will depend almost exclusively on our ability to improve both the quality of the observations and the reduction procedure (instead of, for instance, being limited by the systematic errors in reference catalogs). In this context, we focuse on writing a code to support PRAIA to correct the star positions for the chromatic refraction, essential to reach the milliarcsecond accuracy level from ground-based CCD images. To accomplish this task, we use fortran routines made available by the SOFA (Standandards of Fundamental Astronomy), a stellar spectra data set, and a code to determine interstellar extinction. Such an effort will enable us, for example, to accurately predict stellar occultations by satellites or grazing stellar occultations by rings of small bodies. astrometry; Gaia; Reduction of celestial coordinates; chromatic refraction.