In flight stray light estimate for the Solar Orbiter/Metis coronagraph

Federico Landini; Marco Romoli; Gianalfredo Nicolini; Fabio Frassetto; Roberto Susino; Lucia Abbo; Vincenzo Andretta; Aleksandr Burtovoi; Chiara Casini; Paolo Chioetto; Alain J. Corso; Vania Da Deppo; Yara De Leo; Michele Fabi; Silvano Fineschi; Federica Frassati; Catia Grimani; Petr Heinzel; Giovanna Jerse; Alessandro Liberatore; Giampiero Naletto; Maurizio Pancrazzi; Giuliana Russano; Clementina Sasso; Daniele Spadaro; Marco Stangalini; Daniele Telloni; Luca Teriaca; Michela Uslenghi; Cosimo Volpicelli; Paola Zuppella

doi:10.1117/12.2688578

12 July 2023 In flight stray light estimate for the Solar Orbiter/Metis coronagraph

Federico Landini, Marco Romoli, Gianalfredo Nicolini, Fabio Frassetto, Roberto Susino, Lucia Abbo, Vincenzo Andretta, Aleksandr Burtovoi, Chiara Casini, Paolo Chioetto, Alain J. Corso, Vania Da Deppo, Yara De Leo, Michele Fabi, Silvano Fineschi, Federica Frassati, Catia Grimani, Petr Heinzel, Giovanna Jerse, Alessandro Liberatore, Giampiero Naletto, Maurizio Pancrazzi, Giuliana Russano, Clementina Sasso, Daniele Spadaro, Marco Stangalini, Daniele Telloni, Luca Teriaca, Michela Uslenghi, Cosimo Volpicelli, Paola Zuppella

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Proceedings Volume 12777, International Conference on Space Optics — ICSO 2022; 1277704 (2023) https://doi.org/10.1117/12.2688578
Event: International Conference on Space Optics — ICSO 2022, 2022, Dubrovnik, Croatia

Abstract

After the 10th February 2020 launch (04:03 UTC), Solar Orbiter has recently begun its Nominal Mission Phase and is collecting imaging data as never seen before due to its peculiar orbit. The Metis coronagraph produces maps of the linearly polarized visible light corona in the wavelength band 580-640 nm and UV maps in the Lyman alpha H i 121.6 nm line. Metis is a coronagraph characterized by an innovative external occultation system that has a twofold function: reduce the thermal load and remove the diffraction due to the external occulter support. The positions of the entrance pupil (which is called Inverted External Occulter, IEO) and of the actual occulter are switched so that the pupil is the surface facing the solar disk and the occultation is performed by a spherical mirror, M0. M0 is positioned 800 mm behind IEO and reflects the disk light back through the IEO aperture. An Internal Occulter (IO) is conjugated to the IEO with respect to the primary mirror. IO is mounted on a motorized 2-axis stage that allows to perform in-flight fine adjustments to its position. During the on-ground calibration campaign the contribution of the stray light due to the diffraction from the IEO and scattering off the optics was measured. The measurement was carried out by using the OPSys facility in Torino (Italy), which is equipped with a clean environment and a source that simulates the solar disk divergence. A stray light measurement in flight is not trivial due to the presence of the solar corona. Nevertheless, an IO position optimization campaign has been conducted in order to reduce the stray light. A procedure was developed in order to minimize the stray light level on the instrument focal plane. This contribution reports on the procedure and on the results.

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Federico Landini, Marco Romoli, Gianalfredo Nicolini, Fabio Frassetto, Roberto Susino, Lucia Abbo, Vincenzo Andretta, Aleksandr Burtovoi, Chiara Casini, Paolo Chioetto, Alain J. Corso, Vania Da Deppo, Yara De Leo, Michele Fabi, Silvano Fineschi, Federica Frassati, Catia Grimani, Petr Heinzel, Giovanna Jerse, Alessandro Liberatore, Giampiero Naletto, Maurizio Pancrazzi, Giuliana Russano, Clementina Sasso, Daniele Spadaro, Marco Stangalini, Daniele Telloni, Luca Teriaca, Michela Uslenghi, Cosimo Volpicelli, and Paola Zuppella "In flight stray light estimate for the Solar Orbiter/Metis coronagraph", Proc. SPIE 12777, International Conference on Space Optics — ICSO 2022, 1277704 (12 July 2023); https://doi.org/10.1117/12.2688578

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