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Proceedings Paper • Open Access

ASPIICS/PROBA-3 formation flying solar coronagraph: Stray light analysis and optimization of the occulter
Author(s): F. Landini; A. Mazzoli; M. Venet; S. Vivès; M. Romoli; P. Lamy; G. Massone

Paper Abstract

The “Association de Satellites Pour l'Imagerie et l'Interferometrie de la Couronne Solaire”, ASPIICS, selected by ESA for the PROBA-3 mission, heralds the next generation of coronagraph for solar research, exploiting formation flying to gain access to the inner corona under eclipse-like conditions for long periods of time. A detailed description of the ASPIICS instrument and of its scientific objectives can be found in [1].

ASPIICS is distributed on the two PROBA 3 spacecrafts (S/C) separated by 150 m. The coronagraph optical assembly is hosted by the “coronagraph S/C” protected from direct solar disk light by the occulting disk on the “occulter S/C”.

The most critical issue in the design of a solar coronagraph is the reduction of the stray light due to the diffraction and scattering of the solar disk light by the occulter, the aperture and the optics. In the present article, we deal with two of these issues:

- The analysis of the stray light inside the telescope.

- The optimization of the external occulter edge, in order to eliminate the Poisson spot behind the occulter and to lower the stray light level going through the entrance pupil of the telescope.

This work was performed in the framework of the ESA STARTIGER program which took place at the Laboratoire d’Astrophysique de Marseille (LAM) during a 6-month period from September 2009 to March 2010.

In general, it is a very complicated task to combine the above two stray light issues together in the simulation and design phase as it requires to consider the propagation inside the telescope of the light diffracted by the external occulter. Actually, the present literature only reports diffraction calculations performed for simple occulting systems (i.e., two disks and serrated disk). A more pragmatic approach, also driven by the tight schedule of the STARTIGER program, is to separate the two contributions, and perform two different stray light analyses. This paper is dedicated to the description of both analyses: in particular, the first part is dedicated to the evaluation of the stray light inside the telescope, assuming a simple disk as occulter, and a preliminary baffle design is presented; the second part describes the investigation on the geometry of the external occulter, with a detailed description of the laboratory setup that has been designed and implemented to compare together several types of occulting systems.

Paper Details

Date Published: 20 November 2017
PDF: 7 pages
Proc. SPIE 10565, International Conference on Space Optics — ICSO 2010, 105651R (20 November 2017); doi: 10.1117/12.2309173
Show Author Affiliations
F. Landini, Sez. Astronomia, Univ. di Firenze (Italy)
A. Mazzoli, Univ. de Liège (Belgium)
M. Venet, Lab. d'Astrophysique de Marseille (France)
S. Vivès, Lab. d'Astrophysique de Marseille (France)
M. Romoli, Sez. Astronomia, Univ. di Firenze (Italy)
P. Lamy, Lab. d'Astrophysique de Marseille (France)
G. Massone, INAF - Osservatorio Astrofisico di Torino (Italy)

Published in SPIE Proceedings Vol. 10565:
International Conference on Space Optics — ICSO 2010
Errico Armandillo; Bruno Cugny; Nikos Karafolas, Editor(s)

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