Controlling petals using fringes: discontinuous wavefront sensing through sparse aperture interferometry at Subaru/SCExAO

V. Deo; S. Vievard; N. Cvetojevic; K. Ahn; E. Huby; O. Guyon; S. Lacour; J. Lozi; F. Martinache; B. Norris; N. Skaf; P. Tuthill

doi:10.1117/12.2629865

29 August 2022 Controlling petals using fringes: discontinuous wavefront sensing through sparse aperture interferometry at Subaru/SCExAO

V. Deo, S. Vievard, N. Cvetojevic, K. Ahn, E. Huby, O. Guyon, S. Lacour, J. Lozi, F. Martinache, B. Norris, N. Skaf, P. Tuthill

Author Affiliations +

Proceedings Volume 12185, Adaptive Optics Systems VIII; 121850Z (2022) https://doi.org/10.1117/12.2629865
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Abstract

Low wind and petaling effects, caused by the discontinuous apertures of telescopes, are poorly corrected - if at all - by commonly used workhorse wavefront sensors (WFSs). Wavefront petaling breaks the coherence of the point spread function core, splitting it into several side lobes, dramatically shutting off scientific throughput. We demonstrate the re-purposing of non-redundant sparse aperture masking (SAM) interferometers into low-order WFSs complementing the high-order pyramid WFS, on the SCExAO experimental platform at Subaru Telescope. The SAM far-field interferograms formed from a 7-hole mask are used for direct retrieval of petaling aberrations, which are almost invisible to the main AO loop. We implement a visible light dual-band SAM mode, using two disjoint 25 nm wide channels, that we recombine to overcome the one-lambda ambiguity of fringe-tracking techniques. This enables a control over petaling with sufficient capture range yet without con icting with coronagraphic modes in the near-infrared. We present on-sky engineering results demonstrating that the design is able to measure petaling well beyond the range of a single-wavelength equivalent design.

Conference Presentation

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V. Deo, S. Vievard, N. Cvetojevic, K. Ahn, E. Huby, O. Guyon, S. Lacour, J. Lozi, F. Martinache, B. Norris, N. Skaf, and P. Tuthill "Controlling petals using fringes: discontinuous wavefront sensing through sparse aperture interferometry at Subaru/SCExAO", Proc. SPIE 12185, Adaptive Optics Systems VIII, 121850Z (29 August 2022); https://doi.org/10.1117/12.2629865

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