Mercury radio science experiment of the mission BepiColombo

Mercury has always excited a great interest in the scientific establishment because of its proximity to the Sun that represents, however, the principal obstacle for its observations from Earth and spacecraft exploration. BepiColombo is, therefore, one of the most challenging long-term planetary projects that foresees two spacecraft dedicated to the exploration of Mercury's environment. The mission allows better understanding of the planet itself as well as the formation of our Solar System. The density of Mercury does not conform to that of the other terrestrial planet and for this reason the evaluation of Mercury's interior structure is one of the fundamental objectives of the mission. The Mercury Orbiter Radio Science Experiment (MORE) is one of BepiColombo's investigations, designed to provide an accurate estimation of Mercury's gravity field and Love number k2 by means of highly stable, multi-frequency radio links in X and Ka band. Gravity not only provides crucial information on the interior structure of the planet, but also, allows a good orbit determination of the spacecraft. After an introduction to the mission and the MORE experiment, we report on numerical simulations aiming at a realistic assessment of the attainable accuracy in the determination of Mercury's gravity field. The best results are obtained with a batch-sequential filter, which proves to cope well the complexity of the noise and dynamical models.