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Journal of Astronomical Telescopes, Instruments, and Systems • Open Access

Coronagraph-integrated wavefront sensing with a sparse aperture mask

Paper Abstract

Stellar coronagraph performance is highly sensitive to optical aberrations. In order to effectively suppress starlight for exoplanet imaging applications, low-order wavefront aberrations entering a coronagraph, such as tip-tilt, defocus, and coma, must be determined and compensated. Previous authors have established the utility of pupil-plane masks (both nonredundant/sparse-aperture and generally asymmetric aperture masks) for wavefront sensing (WFS). Here, we show how a sparse aperture mask (SAM) can be integrated with a coronagraph to measure low-order differential phase aberrations. Starlight rejected by the coronagraph’s focal plane stop is collimated to a relay pupil, where the mask forms an interference fringe pattern on a subsequent detector. Our numerical Fourier propagation models show that the information encoded in the fringe intensity distortions is sufficient to accurately discriminate and estimate Zernike phase modes extending from tip-tilt up to radial degree n=5, with amplitude up to λ/20 RMS. The SAM sensor can be integrated with both Lyot and shaped pupil coronagraphs at no detriment to the science beam quality. We characterize the reconstruction accuracy and the performance under low flux/short exposure time conditions, and place it in context of other coronagraph WFS schemes.

Paper Details

Date Published: 12 June 2015
PDF: 12 pages
J. Ast. Inst. Sys. 1(3) 039001 doi: 10.1117/1.JATIS.1.3.039001
Published in: Journal of Astronomical Telescopes, Instruments, and Systems Volume 1, Issue 3
Show Author Affiliations
Hari Subedi, Princeton Univ. (United States)
Neil T. Zimmerman, Princeton Univ. (United States)
N. Jeremy Kasdin, Princeton Univ. (United States)
Kathleen A. Cavanagh, Princeton Univ. (United States)
A. J. Eldorado Riggs, Princeton Univ. (United States)

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