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Proceedings Paper

Lyot-based low order wavefront sensor: implementation on the Subaru Coronagraphic Extreme Adaptive Optics System and its laboratory performance
Author(s): Garima Singh; Olivier Guyon; Pierre Baudoz; Nemanja Jovanovich; Frantz Martinache; Tomoyuki Kudo; Eugene Serabyn; Jonas G. Kuhn
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Paper Abstract

High throughput, low inner working angle (IWA) phase masks coronagraphs are essential to directly image and characterize (via spectroscopy) earth-like planets. However, the performance of low-IWA coronagraphs is limited by residual pointing errors and other low-order modes. The extent to which wavefront aberrations upstream of the coronagraph are corrected and calibrated drives coronagraphic performance. Addressing this issue is essential for preventing coronagraphic leaks, thus we have developed a Lyot-based low order wave front sensor (LLOWFS) to control the wavefront aberrations in a coronagraph. The LLOWFS monitors the starlight rejected by the coronagraphic mask using a reflective Lyot stop in the downstream pupil plane. The early implementation of LLOWFS at LESIA, Observatoire de Paris demonstrated an open loop measurement accuracy of 0.01 λ/D for tip-tilt at 638 nm when used in conjunction with a four quadrant phase mask (FQPM) in the laboratory. To further demonstrate our concept, we have installed the reflective Lyot stops on the Subaru Coronagraphic Extreme AO (SCExAO) system at the Subaru Telescope and modified the system to support small IWA phase mask coronagraphs (< 1λ/D) on-sky such as FQPM, eight octant phase mask, vector vortex coronagraph and the phase induced amplitude apodization complex phase mask coronagraph with a goal of obtaining milli arc-second pointing accuracy. Laboratory results have shown the measurement of tip, tilt, focus, oblique and right astigmatism at 1.55 μm for the vector vortex coronagraph. Our initial on-sky result demonstrate the closed loop accuracy of < 7 x 10-3 λ/D at 1.6 μm for tip, tilt and focus aberrations with the vector vortex coronagraph.

Paper Details

Date Published: 7 August 2014
PDF: 9 pages
Proc. SPIE 9148, Adaptive Optics Systems IV, 914848 (7 August 2014); doi: 10.1117/12.2057211
Show Author Affiliations
Garima Singh, Subaru Telescope, National Astronomical Observatory of Japan (United States)
LESIA, CNRS, Observatorie de Paris (France)
Olivier Guyon, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Jet Propulsion Lab. (United States)
Pierre Baudoz, LESIA, CNRS, Observatorie de Paris (France)
Nemanja Jovanovich, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Frantz Martinache, Observatoire de la Cote d'Azur, CNRS, Univ. de Nice Sophia-Antipolis (France)
Tomoyuki Kudo, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Eugene Serabyn, Jet Propulsion Lab. (United States)
Jonas G. Kuhn, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 9148:
Adaptive Optics Systems IV
Enrico Marchetti; Laird M. Close; Jean-Pierre Véran, Editor(s)

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