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Optical simulations for design, alignment, and performance prediction of silicon pore optics for the ATHENA x-ray telescope
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Paper Abstract

The ATHENA X-ray observatory is a large-class ESA approved mission, with launch scheduled in 2028. The technology of silicon pore optics (SPO) was selected as baseline to assemble ATHENA’s optic with hundreds of mirror modules, obtained by stacking wedged and ribbed silicon wafer plates onto silicon mandrels to form the Wolter-I configuration. In the current configuration, the optical assembly has a 3 m diameter and a 2 m2 effective area at 1 keV, with a required angular resolution of 5 arcsec. The angular resolution that can be achieved is chiefly the combination of 1) the focal spot size determined by the pore diffraction, 2) the focus degradation caused by surface and profile errors, 3) the aberrations introduced by the misalignments between primary and secondary segments, 4) imperfections in the co-focality of the mirror modules in the optical assembly. A detailed simulation of these aspects is required in order to assess the fabrication and alignment tolerances; moreover, the achievable effective area and angular resolution depend on the mirror module design. Therefore, guaranteeing these optical performances requires: a fast design tool to find the most performing solution in terms of mirror module geometry and population, and an accurate point spread function simulation from local metrology and positioning information. In this paper, we present the results of simulations in the framework of ESA-financed projects (SIMPOSiuM, ASPHEA, SPIRIT), in preparation of the ATHENA X-ray telescope, analyzing the mentioned points: 1) we deal with a detailed description of diffractive effects in an SPO mirror module, 2) we show ray-tracing results including surface and profile defects of the reflective surfaces, 3) we assess the effective area and angular resolution degradation caused by alignment errors between SPO mirror module’s segments, and 4) we simulate the effects of co-focality errors in X-rays and in the UV optical bench used to study the mirror module alignment and integration.

Paper Details

Date Published: 19 September 2017
PDF: 32 pages
Proc. SPIE 10399, Optics for EUV, X-Ray, and Gamma-Ray Astronomy VIII, 103990H (19 September 2017); doi: 10.1117/12.2274905
Show Author Affiliations
D. Spiga, INAF - Osservatorio Astronomico di Brera (Italy)
D. Della Monica Ferreira, DTU Space (Denmark)
B. Shortt, European Space Research and Technology Ctr. (Netherlands)
M. Bavdaz, European Space Research and Technology Ctr. (Netherlands)
E. Bergback Knudsen, Technical Univ. of Denmark (Denmark)
G. Bianucci, Media Lario Technologies S.r.l. (Italy)
F. Christensen, DTU Space (Denmark)
M. Civitani, INAF - Osservatorio Astronomico di Brera (Italy)
M. Collon, cosine B.V. (Netherlands)
P. Conconi, INAF - Osservatorio Astronomico di Brera (Italy)
S. Fransen, European Space Agency (Netherlands)
F. Marioni, Media Lario Technologies S.r.l. (Italy)
S. Massahi, DTU Space (Denmark)
G. Pareschi, INAF - Osservatorio Astronomico di Brera (Italy)
B. Salmaso, INAF - Osservatorio Astronomico di Brera (Italy)
A. S. Jegers, DTU Space (Netherlands)
K. Tayabaly, Politecnico di Milano (Italy)
G. Valsecchi, Media Lario Technologies S.r.l. (Italy)
N. Westergaard, DTU Space (Denmark)
E. Wille, European Space Research and Technology Ctr. (Netherlands)

Published in SPIE Proceedings Vol. 10399:
Optics for EUV, X-Ray, and Gamma-Ray Astronomy VIII
Stephen L. O'Dell; Giovanni Pareschi, Editor(s)

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