B6.3 Euclid satellite on orbit commissioning

Massimiliano SAPONARA

Head, Guidance, Navigation and Control Section, Thales Alenia Space Italia

Italy

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Euclid is a space-based optical/near-infrared survey mission of the European Space Agency (ESA) designed to investigate the nature of dark energy, dark matter and gravity by observing their signatures on the geometry of the Universe and on the formation of large structures over cosmological timescales. It has been launched On July 1, 2023 on board Falcon 9 rocket and it is designed for 6 years of nominal survey operations to cover about one third of the entire sky. The Euclid Spacecraft is composed of a Service Module and a Payload Module. The Service Module hosts all sub systems and it was in particular designed to provide the extremely accurate pointing and thermal stability required by the scientific observations. The Payload Module adopted a 1.2 m three-mirror anastigmatic Korsch type telescope, with very high optical quality on a wide field-of-view, and it hosts the sensors of two scientific instruments, the visible imager and the near-infrared spectro-photometer.. During a period of about 5 months after launch, all spacecraft functionalities were systematically tested by a joint team composed by ESA and Industry, in order to prove the on-orbit performance of all subsystems and to allow the start of routine operations. The largest part of the activities was devoted to the Attitude and Orbit Control Subsystem (AOCS), which embeds a Fine Guidance Sensor (FGS) and a cold-gas Micro Propulsion subsystem (MPS) necessary to achieve the stringent pointing requirements. Commissioning of the High Gain Antenna (HGA) and its control logic was also crucial to maximise the data-volume to be transferred to Ground, as well as the verification of the expected performance of the CCSDS File Delivery Protocol (CFDP), which allows to directly download the data files from the Mass Memory Unit (MMU). The decontamination, the cool down to operating temperature and the calibration of the telescope completed the preparation for the scientific operations. The paper will describe the commissioning approach and the measured results, which allowed to declare the satellite ready for scientific calibrations and later for nominal survey.