ESA GNC Conference Papers Repository

BepiColombo is one of ESA’s cornerstone missions; it will study and understand the composition, geophysics, atmosphere, magnetosphere and history of Mercury, the least explored planet in the inner Solar System [1]. It is a joint mission between ESA and the Japan Aerospace Exploration Agency (JAXA). The BepiColombo spacecraft is being developed by AIRBUS Defence and Space. Both to build the three spacecraft modules and to place the two orbiters into orbit at Mercury are an industrial and technological challenge requiring best engineering practices and effort. The thermal conditions become already critical during cruise when approaching the inner solar system and are also a main driver of the very high sensitivity of the spacecraft performance to attitude excursions. Additionally, three major changes in the spacecraft configuration over mission resulting from each of the module separations increase the AOCS complexity in comparison to other missions. The BepiColombo AOCS is required to control and safeguard the spacecraft under these hard environmental and spacecraft constraints while still achieving the demanding scientific pointing requirements. This paper presents an overview of the AOCS design including the most original features like the complex safe and survival mode concept based on uninterrupted attitude knowledge through on-board computer resets, the autonomous High Gain Antenna guidance smoothing algorithm, and the gyro-stellar harmonic drift estimator.