Coating and surface finishing definition for the Solar Orbiter/METIS inverted external occulter

摘要: The METIS coronagraph aboard the Solar Orbiter mission will undergo extreme environmental conditions (e.g., a thermal excursion of about 350 degrees throughout various phases), due to peculiar spacecraft trajectory that reach a perihelion 0.28 AUs. is characterized by an innovative design for the occultation system allows halve load inside instrument while guaranteeing stray light reduction required solar coronagraph. Inverted External Occulter (IEO) concept revolutionizes the classical scheme, exchanging usual positions entrance aperture (that now outermost element facing Sun) with actual occulter spherical mirror coronagraph boom). chosen material IEO manufacturing Titanium, as trade o_ between light weight, strength and low expansion coefficient. A 2 years long test campaign has been run define geometry, and its results are addressed in previous dedicated papers. This work describes further campaign aimed at defining surface and edge finishing, support flange geometry Titanium coating. Various finishing were installed on prototype occulting their performance in reduction compared. was designed order reduce overall weight, control accentuate suppression performance. coating a particularly delicate issue. black necessary assess issues, typically critical for visible coronagraphs. Black not standard process, thus several space qualified black coatings experimented characterized. impact coatings evaluated, the reflectivity BRDFs measured paper.