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Photon sieves as EUV telescopes for Solar Orbiter

We elaborate about obtaining images of the solar disc and of the solar corona at discrete wavelengths along the EUV emission solar spectrum on board the Solar Orbiter spacecraft. Refractive optics cannot be used. The thermal load is twenty five times higher than on a near Earth orbit. As on one side the efficiency of a stenopeic device is too low, and as on the other side mirrors exposed directly to the light and to the particles emitted by the Sun may severely degrade during time, we investigated using the EUV analog of a Fresnel lens, i.e. a photon sieve. An opaque self supporting flat piece of heat resistant metal let the solar light shine through a large numbers of a few thousand holes properly designed in positions and diameters in order to obtain constructive interferences at some focus. We report about practical experiments in the visible.