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Proceedings Paper

Stray-light analyses of the METIS coronagraph on Solar Orbiter
Author(s): S. Fineschi; P. Sandri; F. Landini; M. Romoli; V. DaDeppo; F. Frassetto; E. Verroi; G. Naletto; D. Morea; E. Antonucci; D. Spadaro; V. Andretta
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Paper Abstract

The METIS coronagraph on board the Solar Orbiter mission will have the unique opportunity of observing the solar outer atmosphere as close to the Sun as 0.28 A.U., and from up to 35° out-of-ecliptic. The telescope design of the METIS coronagraph includes two optical paths: i) broad-band imaging of the full corona in linearly polarized visible-light (VL: 580-640 nm), ii) narrow-band imaging of the full corona in the ultraviolet (UV) Lyman α (121.6 nm). This paper describes the stray-light analyses performed on the UV and VL channels of the METIS Telescope with the nonsequential modality of Zemax OpticStudio. A detailed opto-mechanical model of the METIS Telescope is simulated by placing the CAD parts of all the sub-assemblies at the nominal position. Each surface, mechanical and optical, is provided with a modelled coating and BSDF reproducing the optical and the diffusing properties. The geometric model allows for the verification of the correct functioning of the blocking elements inside the telescope and for an evaluation of the stray-light level due to surface roughness. The diffraction off the inner edge of the IEO on the plane of the IO is modelled separately from the contributor of the surface micro-roughness. The contributors due to particle contamination and cosmetic defects are also analysed. The results obtained are merged together and compared to the requirements of stray-light. The results of this analysis together with those from two different analyses based on a Montecarlo ray-trace and a semi-analytical model are consistent with each other and indicate that the METIS design meets the stray-light level requirements

Paper Details

Date Published: 25 September 2015
PDF: 18 pages
Proc. SPIE 9604, Solar Physics and Space Weather Instrumentation VI, 96040K (25 September 2015); doi: 10.1117/12.2203629
Show Author Affiliations
S. Fineschi, INAF - Astrophyical Observatory of Torino (Italy)
P. Sandri, CGS S.p.A. (Italy)
F. Landini, INAF - Astrophysical Observatory of Arcetri (Italy)
M. Romoli, Florence Univ. (Italy)
V. DaDeppo, CNR-IFN LUXOR Lab. (Italy)
F. Frassetto, CNR-IFN Padua Univ. (Italy)
E. Verroi, CISAS, Padua Univ. (Italy)
G. Naletto, Padua Univ. (Italy)
D. Morea, CGS S.p.A. (Italy)
E. Antonucci, INAF - Astrophyical Observatory of Torino (Italy)
D. Spadaro, INAF - Astronomical Observatory of Catania (Italy)
V. Andretta, INAF - Astronomical Observatory of Capodimonte (Italy)

Published in SPIE Proceedings Vol. 9604:
Solar Physics and Space Weather Instrumentation VI
Silvano Fineschi; Judy Fennelly, Editor(s)

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