The first camera prototype of the PLATO mission successfully tested at CSL

The Centre Spatial de Liège (CSL) has just completed the first vibration tests of the first camera model, 26 of which will be embarked on board the PLATO Space Observatory of the European Space Agency. In addition to its technical involvement in this mission - which should be launched in 2026 - the University of Liège also has many astrophysicists involved in the scientific and data analysis part of the mission.

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he CSL has just successfully completed the alignment and vibration tests of the first prototype camera on board PLATO - PLAnetary Transits and Oscillations of stars. PLATO is a European Space Agency (ESA) mission of the Cosmic Vision programme whose objective is to find and study a large number of extra-solar planetary systems, focusing on the properties of terrestrial planets in the habitable zone around bright stars other than our sun, using methods based on transit photometry. PLATO has also been designed to study the seismic activity of stars, allowing precise characterisation of the planet's host star, including its age. 

Within the framework of this mission, CSL has been designated, thanks to funding from the Belgian Science Policy (Belspo), to carry out the assembly, alignment and vibration resistance tests of the 26 cameras that will be put into orbit, as well as the three or four prototype cameras that will precede the flight models. The images from these 26 cameras will be used to collect data, including photometric data, on planets located in solar systems other than our own. The fact that the mission includes 26 cameras meant that an automated alignment method had to be developed in order to carry out the task 26 times in a relatively short space of time," explains Aline Hermans, engineer and project manager for the CSL. Various methods were proposed and tested on digital models before being applied in the laboratory. One of the complexities of the alignment lies in the fact that it is carried out at room temperature, whereas the operational temperature is strongly negative. This leads to a high noise level at the detector and makes it necessary to take into account thermal expansions with accuracies of only a few microns. ». The CSL will test a second prototype in May 2021, then a qualification model in early 2022, followed by the alignment of the 26 flight cameras between July 2022 and April 2024.

A new scientific adventure in which many astrophysicists from the ULiège's STAR Research Institute and Astrobiology will also take part, preparing and participating in the analysis of the data that will be provided by PLATO. PLATO will use the technique known as "transits" to detect and characterize exoplanets by measuring the very low periodic attenuation of the star's radiation when a planet passes between it and the satellite. "By applying a method called asteroseismology, similar to seismology on Earth, vibrations will reveal the internal structure of stars. This will make it possible to measure the age of stars and the planets they house accurately," explains Thierry Morel, astrophysicist at the Laboratory of Theoretical Stellar Astrophysics and Asteroseismology (STAR Research Institute / Faculty of Sciences) of ULiège.. "This information is crucial for a better understanding of how stars and their planets form and evolve and may allow us to determine whether or not our system is an exception in the Universe. In order to carry out these measurements, the satellite will be placed in orbit around the sun at the Lagrange L2 point, just over 1.5 million kilometres from our planet, opposite the sun (between the Earth and Mars).  PLATO is scheduled for launch in 2026.