The Euclid spacecraft was launched on July 1st 2023 from Cape Canaveral by a Falcon 9 rocket. Following a smooth orbit injection around Lagrange Point 2 (L2) and a successful commissioning phase, the telescope was ready to start its scientific mission. Euclid, a medium-class mission in the Cosmic Vision program of the European Space Agency (ESA), will investigate the evolution of our Universe over the past ten billion years using a visible to near-infrared telescope to survey red shift and weak lensing of galaxies over 35% of the sky. This will permit improving current cosmological models and better understanding the role of dark energy and dark matter. To accomplish its scientific goals, Euclid needs excellent image quality to make sure that the measured features are not induced by the telescope system itself. The required image quality is extremely sensitive to slight variations of the temperature distribution that are caused by changes of the solar illumination associated with different pointing directions and variations of internal power dissipation associated with different usage of the telescope. After on-ground verification by analysis and test, the ultimate verification of the spacecraft, including that of the thermal design performance necessary for the achievement of scientific objectives, was based on feedback from flight data. In-flight, the Euclid thermal design showed the expected performance in controlling the temperature of the satellite in all operative conditions and phases and provided the telescope with the needed thermal stability. This paper describes the most interesting aspects of the in-flight behavior of the Euclid thermal design and provides a general assessment of the thermal model predictions against flight data. The in-flight validation of the thermal results of a complex spacecraft constitutes always a precious opportunity to gather important feedbacks on the thermal design which are invaluable in view of future projects.
Gottero et al. (Sun,) studied this question.