Optimal robust sun-pointing control for the Eutelsat 172B, a large geostationary electrical-propelled satellite, is addressed in this thesis. For spacecraft which propulsion module is based exclusively on high-power electric engines, it is crucial to guarantee the optimal power production during the whole mission. Moreover, for telecommunication satellites is fundamental to maintain the desired pointing to fulfill mission and operational requirements, despite external perturbations that could affect their orientation. To optimize the power generation, guaranteeing proper solar-array sun-tracking, while tracking the desired Earth-pointing orientation of the satellite and its payloads, a first-order Sliding Mode Controller and a Tube-based Robust Model Predictive Control strategy have been implemented, combined with a controller for arrays sun tracking.