Design Of The MMX Rover Attitude Control System For Autonomous Power Supply

Abstract

The Martian Moons eXploration (MMX) mission led by the Japan Aerospace Exploration Agency (JAXA) aims at studying Phobos and Deimos. It includes a small rover that will explore Phobos, carried out jointly by the French Space Agency (CNES) and the German Aerospace Center (DLR). With its fixed solar array, the rover does not receive enough energy in nominal driving orientation to recharge its battery. Therefore, an attitude control system manages the rover orientation, using the locomotion system and a sun sensor. The specifics of the control loop such as movements limitations or tranquilization periods are due to the dynamic interactions with the regolith. This paper presents the attitude control system (SKA) architecture, through the various challenges encountered: limited design flexibility with major changes during the development, small knowledge of Phobos' expected soil, very tight schedule to meet the JAXA delivery date. The design drivers were to create the simplest and most robust system to orient the rover in order to maximize the battery recharge, while ensuring the rover stability and addressing the above issues. A particular focus is made on the preliminary simulation results. Finally, the way forward is outlined with the SKA development and validation steps.