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Proceedings Paper • Open Access

Stray light calibration for the Solar Orbiter/Metis solar coronagraph
Author(s): F. Landini; M. Romoli; S. Fineschi; C. Casini; C. Baccani; E. Antonucci; G. Nicolini; G. Naletto; P. Nicolosi; D. Spadaro; V. Andretta; M. Castronuovo; M. Casti; G. Capobianco; G. Massone; R. Susino; V. Da Deppo; F. Frassetto; M. Pancrazzi; L. Teriaca; U. Schuehle; K. Heerlein; M. Uslenghi

Paper Abstract

The Solar Orbiter/Metis visible and UV solar coronagraph redefines the concept of external occultation in solar coronagraphy. Classical externally occulted coronagraphs are characterized by an occulter in front of the telescope entrance aperture. Solar Orbiter will approach the Sun down to 0.28 AU: in order to reduce the thermal load, the Metis design switches the positions of the entrance aperture and the external occulter thus achieving what is called the inverted external occultation. The inverted external occulter (IEO) consists of a circular aperture on the Solar Orbiter thermal shield that acts as coronagraph entrance pupil. A spherical mirror, located 800 mm behind the IEO, back rejects the disklight through the IEO itself. To pursue the goal of maximizing the reduction of the stray light level on the focal plane, an optimization of the IEO shape was implemented.

The stray light calibration was performed in a clean environment in front of the OPSys solar disk divergence simulator (at ALTEC, in Torino, Italy), which is able to emulate different heliocentric distances. Ground calibrations were a unique opportunity to map the Metis stray light level thanks to a pure solar disk simulator without the solar corona. The stray light calibration was limited to the visible light case, being the most stringent. This work is focused on the description of the laboratory facility that was used to perform the stray light calibration and on the calibration results.

Paper Details

Date Published: 12 July 2019
PDF: 16 pages
Proc. SPIE 11180, International Conference on Space Optics — ICSO 2018, 111802I (12 July 2019); doi: 10.1117/12.2536009
Show Author Affiliations
F. Landini, INAF – Osservatorio Astrofisico di Arcetri (Italy)
M. Romoli, Univ. degli Studi di Firenze (Italy)
S. Fineschi, INAF – Osservatorio Astrofisico di Torino (Italy)
C. Casini, Univ. degli Studi di Firenze (Italy)
C. Baccani, INAF – Osservatorio Astrofisico di Arcetri (Italy)
E. Antonucci, INAF – Osservatorio Astrofisico di Torino (Italy)
G. Nicolini, INAF – Osservatorio Astrofisico di Torino (Italy)
G. Naletto, Univ. of Padova, CNR-IFN (Italy)
P. Nicolosi, CNR-IFN (Italy)
D. Spadaro, INAF – Osservatorio Astrofisico di Catania (Italy)
V. Andretta, INAF – Osservatorio Astronomico di Capodimonte (Italy)
M. Castronuovo, Agenzia Spaziale Italiana (Italy)
M. Casti, INAF – Osservatorio Astrofisico di Torino (Italy)
G. Capobianco, INAF – Osservatorio Astrofisico di Torino (Italy)
G. Massone, INAF – Osservatorio Astrofisico di Torino (Italy)
R. Susino, INAF – Osservatorio Astrofisico di Torino (Italy)
V. Da Deppo, CNR-IFN (Italy)
F. Frassetto, CNR-IFN (Italy)
M. Pancrazzi, Univ. degli Studi di Firenze (Italy)
L. Teriaca, Max Planck Institute for Solar System Research (Germany)
U. Schuehle, Max Planck Institute for Solar System Research (Germany)
K. Heerlein, Max Planck Institute for Solar System Research (Germany)
M. Uslenghi, INAF-IASF (Italy)


Published in SPIE Proceedings Vol. 11180:
International Conference on Space Optics — ICSO 2018
Zoran Sodnik; Nikos Karafolas; Bruno Cugny, Editor(s)

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