Le refroidissement du plus grand télescope solaire au monde

Le téléscope solaire à haute technologie (ATST), en cours de construction sur l'île de Maui, sera le plus grand téléscope au monde, capable de fournir les images les plus précises de la surface solaire. (en anglais)
The Advanced Technology Solar Telescope (ATST), currently under construction on the Pacific island of Maui, will be the world’s largest solar telescope, able to provide the sharpest views ever taken of the solar surface and resolve the extremely small, violently active, magnetic fields that control the temperature of the corona and the solar winds, flares and x-ray emissions.

A solar-telescope specific problem is the heat generated by the tightly-focused sunlight and large quantities of heat energy. In conventional telescopes, a “Heat Stop” is situated at the prime focus and prevents unwanted solar-disc light from heating and scattering the subsequent optics.

A solar telescope must also dissipate huge amounts of thermal energy: for the upcoming ATST, the thermal load is 2.5MW/m² and must be reduced from an enormous 12MW to merely 300W, i.e. a 40,000 reduction factor. The heat stop assembly, designed by Thermacore, is actively cooled by an internal system of heat pipes that dissipate approximately 1,700 W at peak operating load.

Another challenge is that the heat stop must not only be able to survive this heat load, but also to remain cool enough not to induce any additional turbulence inside the telescope dome: its surface temperature must never be 10°C higher than the temperature of the ambient air as this could provoke turbulence likely to degrade image quality.