The orbits of outer planetary satellites using theGaiadata

Abstract

ABSTRACTLaunch of the Gaia space observatory started a new era in astrometry when the accuracy of star coordinates increased by thousands of times. Significant improvement in accuracy was also expected for the coordinates of the Solar system bodies. Gaia Data Release 3 (DR3) provided us with the data that could be used to test our expectations. In this work, we refine the orbits of a number of outer planetary satellites using both ground-based and Gaia observations. From 13 outer satellites observed by Gaia, we chose 6 to obtain their orbits. Some specific moments in using observations of outer satellites made by Gaia are demonstrated. These peculiarities stem from scanning motion of Gaia, in particular from the fact that the accuracy of observations is significantly different along and across the scanning direction. As expected, Gaia observations proved to be more precise than those made from Earth, which results in more accurate satellite ephemerides. We estimate accuracy of the ephemerides of considered satellites for the interval between 1996 and 2030. As astrometric positions published in Gaia DR3 were not corrected for the relativistic light deflection by the Sun, we took into account this effect, which slightly diminished the rms residuals. In addition, relativistic light deflection by the giant planets was estimated, which, as it turned out, can be neglected with the given accuracy of Gaia observations.