Estudo Astrométrico dos Satélites Galileanos de Júpiter

Abstract

Progress in astrometry and in dynamical modeling of planetary systems have made possible the accurate estimation of tidal effects in natural moons and their planets. These studies have provided essential constraints on short and long term dynamics, including interior and formation processes. This improvement has been made mostly within the Saturn system with the results of Cassini space mission. It was a collaborative mission between the National Aeronautics and Space Administration (NASA), the European Space Agency (ESA) and the Agenzia Spaziale Italiana (ASI). In the Jovian system's case, most of the astrometry originate from ground-based observations. At the current time, no space missions are orbiting this system. However, the Jupiter Icy Moons Explorer (JUICE) from ESA and the Europa Clipper from NASA are currently being prepared. Both space missions are scheduled to be launched in the next decade (the 2020s). Even though ground-based astrometry is necessary, the classical CCD methods are unable to obtain accurate positions due to Jupiter brightness. This classical astrometry obtains positions with uncertainties in the 150 milliarcseconds (mas) level, roughly 450 kilometers (km) at Jupiter distance. This difficult motivates the search for alternative methods to acquire Galilean satellite's positions with uncertainties bellow the 30 mas level (~ 90 km). In this project, we analyze alternative techniques to obtain the astrometry of this system. We explore the mutual phenomena technique, the mutual approximation, stellar occultation, and stacking image procedure. These techniques were applied to observations made at the Observatório do Pico dos Dias (OPD), the Observatoire de Haute-Provence (OHP), and observations made at different stations in Brazil and South America. These observations were a collaboration between professionals astronomers and the amateur community. Within this project, we organized three observational campaigns: The Brazilian mutual phenomena campaign in 2014-2015, the mutual approximation campaign between 2016 and 2019, and the campaign to observe the stellar occultation by Europa in March of 2017. Most observations in this project were made with the narrow band Methane filter centered in 889 nm with a width of 15 nm. This filter efficiently eliminates Jupiter's scattered light, allowing images with higher quality. In this thesis, we gathered reductions and analyses processes of these astrometric techniques and their application to observations. In the mutual phenomena context, we analyze 47 light curves observed in our campaign in 2014-2015 and re-analyze 25 events observed in 2009; the mean uncertainty was in the 10 mas level (~ 30 km). In the mutual approximation context, we analyzed 127 separation curves observed between 2016 and 2019; the mean uncertainty was also around 10 mas (~ 30 km). Also, we analyzed the first stellar occultation by the Galilean moon Europa ever observed and determined a position with an uncertainty below 1 mas (~ 3 km). At least, we obtained preliminary results of the stacking image technique applied to the Galilean moons. We analyzed 9 nights of observation between 2018 and 2019, and we determined absolute positions with uncertainties in the 20 mas level (~ 60 km). The astrometric methods analyzed in this project can be adapted to other systems, and the positions we furnished will be used in dynamical studies aiming the development of new and more precise ephemerides for the Galilean moons. These improved orbits will contribute to the study of tidal dissipation in this system, ultimately providing more information about the interior of these satellites. Also, these improved orbits will help to prepare JUICE and Europa Clipper space missions.