Thermal Balance Test of Solar Orbiter EUI Instrument Structural and Thermal Model with 13 Solar Constants

Developed by a European consortium led by the Centre Spatial de Liège in Belgium, the Extreme Ultraviolet Imager (EUI) is an instrument onboard the Solar Orbiter ESA M-class mission. At its 0.28AU perihelion, the spacecraft will be exposed to a 13 solar constants solar flux. EUI is protected behind the spacecraft heat shield but for three apertures for its telescopes looking at the Sun in the Extreme-UV. To better reject the unwanted visible light and protect 150nm thick EUV filters, Aluminum coated carbon-fiber-reinforced plastics entrance baffles are located at the front of the instrument. The residual absorbed heat by the entrance filters and baffles is evacuated through heat pipes to a dedicated spacecraft thermal interface.
To verify its thermal design, the instrument structural and thermal model has been tested in a vacuum chamber with a solar simulator providing the 13 solar constants solar flux at the three entrance apertures and dedicated heaters to model the spacecraft heat shield feedthroughs. To assess the off-pointing performance of the entrance baffles, the instrument was mounted onto a rotating structure inside the chamber. The test setup, results and the thermal model correlation will be presented as well as the calibration of the solar simulator divergence and intensity.