The astrometry of the natural planetary satellites applied to their dynamics before and after Gaia

International audienceThe natural planetary satellites are observed since centuries in order to understand their dynamics and their evolution. A high level astrometric accuracy is necessary for this purpose. The arrival of Gaia makes necessary to perform the ground-based observations in the scope of the future data provided by Gaia. About 50 observations by Gaia of each satellite will be available, and the Gaia star catalogue will allow to reduce the astrometric observations with a high level accuracy. This is true for observations made at the present time, made in the future, and made in the past thanks to a new reduction of old observations such as photographic plates. We analyse the different status of the satellites depending on the system of which they belong. This will decide the astrometric observing programmes of the natural planetary satellites for the next years