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Proceedings Paper

High-contrast imaging with an arbitrary aperture: active correction of aperture discontinuities
Author(s): Laurent Pueyo; Colin Norman; Rémi Soummer; Marshall Perrin; Mamadou N'Diaye; Elodie Choquet
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Paper Abstract

We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a missing segment" . We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime and illustrate the broadband properties of ACAD in the case of the pupil configuration corresponding to the Astrophysics Focused Telescope Assets. Since details about these telescopes are not yet available to the broader astronomical community, our test case is based on a geometry mimicking the actual one, to the best of our knowledge.

Paper Details

Date Published: 27 September 2013
PDF: 16 pages
Proc. SPIE 8864, Techniques and Instrumentation for Detection of Exoplanets VI, 88640Z (27 September 2013); doi: 10.1117/12.2025123
Show Author Affiliations
Laurent Pueyo, Space Telescope Science Institute (United States)
Colin Norman, Johns Hopkins Univ. (United States)
Rémi Soummer, Space Telescope Science Institute (United States)
Marshall Perrin, Space Telescope Science Institute (United States)
Mamadou N'Diaye, Space Telescope Science Institute (United States)
Elodie Choquet, Space Telescope Science Institute (United States)

Published in SPIE Proceedings Vol. 8864:
Techniques and Instrumentation for Detection of Exoplanets VI
Stuart Shaklan, Editor(s)

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