Optimization of the occulter for the Solar Orbiter/METIS coronagraph

摘要: METIS (Multi Element Telescope for Imaging and Spectroscopy investigation), selected to fly aboard the Solar Orbiter ESA/NASA mission, is conceived perform imaging (in visible, UV EUV) spectroscopy of solar corona, by means an integrated instrument suite located on a single optical bench sharing same aperture satellite heat shield. As every coronagraph, highly demanding in terms stray light suppression. Coronagraphs history teaches that particular attention must be dedicated occulter optimization. The occulting system interest due its innovative concept. In order meet strict thermal requirements Orbiter, design has been optimized moving entrance pupil at level external S/C shield, thus reducing size aperture. scheme based inverted external-occulter (IEO). IEO consists circular A spherical mirror rejects back disk-light through IEO. breadboard assembly (BOA) manufactured tests front two simulators Marseille, France Torino, Italy). first measurement campaign carried Laboratoire d'Astrophysique de Marseille. this paper we describe BOA design, laboratory set-up preliminary results.