Orbital Behaviour of the Inner Faint Jovian Satellites: Modelling the Motion of JXIV Thebe

Abstract

Since their discovery by the Voyager space probes, the jovian satellites Jxiv Thebe, Jxv Adrastea and Jxvi Metis have not been extensively observed. The closeness to the bright planet Jupiter and the faintness of these objects explain this fact. Nevertheless several series of observations exist and have not yet been used to improve our knowledge of the motions of these satellites. In this article we will gather these observations and acquire new ones in order to fit them and to get an improved model of the motions. Former works have been done in the past which proved the ability to perform campaigns of observations of Jxiv Thebe from a one-meter telescope at the Pic du Midi observatory in the French Pyrenean mountains. A first analytical model was issued from this former work (Colas, 1991) and we intend to improve this model. In the near future we plan to deal both numerically and analytically with this problem and to increase the total amount of the astrometric observations of the faint jovian inner satellites thanks to new campaigns. At the present time, we have gathered a part of the existing observations and we have reduced some of them. We have developed a numerical model and fitted this model on a first series of observations spanning from 1985 to 1999. The purpose of this work is to get an improved dynamical model including the maximum amount of disturbing effects allowing us to search for small unexpected residuals which could be a signature of faint effects due to the jovian environment.