AOCS dimensioning of Tech for Space Care demonstration satellites

The increasing development of the space sector has resulted in a significant augmentation of space objects in Low Earth Orbit. As a consequence, new major concerns have emerged for active spacecraft and future missions, due to an enhanced risk of collision and the accumulation of artificial debris in space. This has resulted in a growing demand for a sustainable and safe use of space in recent years. The implementation of new on-board technologies capable of taking these requirements into account, and the consequent adaptation of the Attitude and Orbit Control Systems (AOCS), become critical in order to meet the performance criteria of new space missions. In this context, CNES is monitoring the development of innovative AOCS units within the R&T framework, in connection with the implementation of the French Space Operations Act, aiming to protect against orbital debris and avoid generating them. In particular, the CNES "Tech for Space Care" initiative envisages the operation of demonstration nanosatellites carrying this new type of technologies in order to validate them in flight. The purpose of this thesis is to contribute to the system definition of a “Tech for Space Care” demonstrator integrating a passive magnetic detumbler proposed by one of the R&Ts in connection with CNES. This device is conceived as an innovative AOCS technology to be used in future missions in order to eventually facilitate Active Debris Removal operations, notably challenged by tumbling motion caused by accumulated perturbations on dead satellites. Moreover, this study involves the development and the modification of MATLAB/Simulink AOCS simulators in order to test the inclusion of the proposed technology in a reference mission. These simulators enable to evaluate its impact on general AOCS performance indicators (pointing offset angles, instabilities, saturation of actuators etc.) as well as the effectiveness and robustness of the proposed control strategies, with a view to verify the feasibility of the envisaged mission. In the first part of this document, the system architecture and the AOCS of the chosen reference mission, the working environment and tools are presented. Then, the detumbler is characterized in terms of sensitivity to the variation of its sizing parameters. The second part deals with the creation and the insertion of a configurable Simulink model of the device into the MATLAB/Simulink AOCS simulator of the reference mission, in order to correctly size the device so as to ensure the detumbling function in the End-of-Life phase of the satellite. On the other hand, the degradation of mission performance imposing the need for corrective actions, the introduction of a feedforward controller in addition to the reference feedback control loop is proposed, analysed and validated.