Euclid AOCS: Fine Guidance Sensor modelling and simulation

The present document is written for the Master degree course in Aerospace engineering of Politecnico di Torino, during a six month thesis internship in Thales Alenia Space site of Turin (TO), Italy. Scope of the work is to build a simulation tool, in Matlab environment, of FGS attitude sensor, supporting tests on the Engineering Qualification Model of the same. The sensor is designed in the context of European Space Agency Euclid mission, whose optic scientific instruments require unprecedented pointing performances. Its main goal is to compensate thermoelastic deformations induced errors on attitude determination, being part of an innovative Attitude and Orbit Control System architecture. More in details, the content of the document foresees in the first chapter an introduction to Euclid mission objectives and design. So, the second one continues the description, focusing on the architecture and operations in scientific mode of AOCS. Therefore, third chapter goes down to FGS design level, showing its main assemblies and functionalities. Furthermore, a summary of its modes of operation is presented, especially of the tracking ones and related timing sequences. Fourth chapter, instead, introduces some spacecraft attitude determination techniques and it shows the theoretical bases of the ones applied by FGS sensor. Fifth chapter treats the main contributors to performances of such a Charge Coupled Device based sensor and it lists measurement requirements and expected budget in terms of errors on attitude angles. Core of thesis is the sixth chapter. It explicits the test process and the role of the simulator in support to that. There, other scripts written out of simulator, but fundamental in test input files generation, are also cited. They are partially reported in appendices A and B. Seventh chapter describes the implemented model of FGS and it shows the results of specific scenarios. Consequently, the final chapter comments on them and it explores future applications. Main script of simulator is reported in appendix C.