ESA GNC Conference Papers Repository

Airbus Defence and Space is developing the Eurostar Neo telecom satellite product line, supported by ESA and CNES in the frame of the ARTES 14 program. Eurostar Neo product is built on the heritage from the E3000 telecom product, which already featured electric raising capability and fully-electric station keeping, in order to deliver a fully electric orbit raising (EOR) transfer phase. To achieve a fully-electric EOR, the Eurostar Neo platform introduced a number of innovations to ensure that the electric thrust direction is optimized at all times in order to control the fuel consumption and to reduce the duration of EOR phase. Certainly the greatest challenge has been the management of the high disturbance torques during the pre-EOR phase. Coupled with the existing and future launchers capability, the large range of platform size covered by the Eurostar Neo product indeed led to significant gravity gradient and aerodynamic torques during the first days of the mission. Torque management is therefore key for those orbits with low perigee (below 400 km) before the electrical thrusters are operational. A simple and innovative solution has been developed based on a wheel-controlled cruise mode. This wheel cruise mode actually serves two purposes: it is used nominally before the EOR starts and as a robust backup mode during the EOR. It relies on a specific attitude guidance law coupled with a dedicated Solar Array guidance, which aim at minimizing aerodynamic and gravity gradient torques close to the perigee. A dedicated on-board orbit propagator (OBOP) has also been designed to compute the orientation of the Earth-linked AOCS mission reference frame, in order to reach the required precision for SADM & attitude commanding, which is a key contributor to the mode robustness in the early EOR phase. In addition, Eurostar Neo AOCS has driven the introduction of Airbus Defence and Space auto-coding development process. This process allows reducing the development time and cost, as well as providing more agility in the AOCS development. It relies in particular on a unique functional architecture which groups the AOCS processing according to their processing type. This paved the way to the concurrent development of AOCS software for both Eurostar Neo full-electric platform and Eutelsat Quantum chemical platform at the same time. Eurostar Neo and Eutelsat Quantum AOCS design is indeed based on common architecture, functions and mode management. AOCS software has been qualified in March 2021. Last but not least, spacecraft autonomy has been increased through simplified FDIR and recovery operations. The principle of AOCS FDIR is a hierarchical failure recovery adapted to the failure detection. The global principle of this hierarchical FDIR is to minimize the number of HW reconfiguration, to maintain mission as long as possible, i.e. satellite Earth pointing, and to ensure recovery in a mode where all used equipment units are either monitored or have been reconfigured. The recovery from on station safe mode to nominal mode has been made fully automatic, without mission interruption in most anomaly cases, leading to an easy-to-use platform.