A laboratory experiment for a new free-standing pupil mask coronagraph

K. Haze; K. Enya; T. Kotani; L. Abe; T. Nakagawa; H. Matsuhara; T. Sato; T. Yamamuro

doi:10.1117/12.925845

21 September 2012 A laboratory experiment for a new free-standing pupil mask coronagraph

K. Haze, K. Enya, T. Kotani, L. Abe, T. Nakagawa, H. Matsuhara, T. Sato, T. Yamamuro

Proceedings Volume 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave; 84425B (2012) https://doi.org/10.1117/12.925845
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

This paper presents the results of a laboratory experiment on a new free-standing pupil mask coronagraph for the direct observation of exoplanets. We focused on a binary-shaped pupil coronagraph, which is planned for installation in the next-generation infrared space telescope SPICA. Our laboratory experiments on the coronagraph were implemented inside a vacuum chamber (HOCT) to achieve greater thermal stability and to avoid air turbulence, and a contrast of 1.3×10^-9 was achieved with PSF subtraction. We also carried out multi-color/broadband experiments to demonstrate that the pupil mask coronagraph works, in principle, at all wavelengths. We had previously manufactured a checker-board mask, a type of binary-shaped pupil mask, on a glass substrate, which had the disadvantages of light loss by transmission, ghosting from residual reflectance and a slightly different refractive index for each wavelength. Therefore, we developed a new free-standing mask in sheet metal, for which no substrate was needed. As a result of a He-Ne laser experiment with the free-standing mask, a contrast of 1.0×10⁻⁷ was achieved for the raw coronagraphic image. We also conducted rotated mask subtractions and numerical simulations of some errors in the mask shape and WFEs. Speckles are the major limiting factor. The free-standing mask exhibited about the same ability to improve contrast as the substrate mask. Consequently, the results of this study suggest that the binary-shaped pupil mask coronagraph can be applied to coronagraphic observations by SPICA and other telescopes.

Citation Download Citation

K. Haze, K. Enya, T. Kotani, L. Abe, T. Nakagawa, H. Matsuhara, T. Sato, and T. Yamamuro "A laboratory experiment for a new free-standing pupil mask coronagraph", Proc. SPIE 8442, Space Telescopes and Instrumentation 2012: Optical, Infrared, and Millimeter Wave, 84425B (21 September 2012); https://doi.org/10.1117/12.925845

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KEYWORDS

Coronagraphy

Point spread functions

Photomasks

Infrared telescopes

Space telescopes

Infrared radiation

Numerical simulations

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