TY - CONF
T1 - Mitigate the impact of ELT architecture on AO performance
T2 - 5th Adaptive Optics for Extremely Large Telescopes, AO4ELT 2017
AU - N'Diaye, M.
AU - Martinache, F.
AU - Jovanovic, N.
AU - Lozi, J.
AU - Guyon, O.
AU - Norris, B.
AU - Ceau, A.
AU - Mary, D.
N1 - Funding Information:
This work is supported by the European Research Council (ERC) through the KERNEL project grant #683029 (PI: F. Mar-tinache). M.N. would like to thank Alain Spang for the very engaging conversations on the identification and diagnostic of the island effect by Couder in 194920 with a Foucault knife-edge test on an 80 cm telescope at Observatoire de Haute Provence. This work was supported by the Astrobiology Center (ABC) of the National Institutes of Natural Sciences, Japan and the directors contingency fund at Subaru Telescope. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Publisher Copyright:
© 2017 Instituto de Astrofisica de Canarias. All rights reserved.
PY - 2017
Y1 - 2017
N2 - Island effects (IE) are critical piston difierential aberrations between neighbouring pupil segments on ground-based telescopes that degrade the quality of Adaptive optics (AO) images on 8m-class telescopes in good observing conditions. Due to telescope architecture, these residual errors lead to a loss of observing time, up to 20% as observed on the VLT during the direct imaging observations of planetary companions with SPHERE. These effects are expected to be even more critical with ELTs as these observatories will present more complex architectures. Measuring these effects however prove very challenging for most of the state-of-the-art AO wavefront sensors. A first successful diagnosis of these aberrations has recently been obtained on SPHERE with ZELDA, the Zernike wavefront sensor for the measurement of residual aberrations in coronagraphic systems. In this communication, we focus on the Asymmetric Pupil Fourier-wavefront sensor (APF-WFS) that relies on point source images to retrieve wavefront errors with an interferometric analysis. Assuming the archetypal four-quadrant aperture geometry in 8m class telescopes, we define aberration modes based on piston, tip, and tilt over the pupil quadrants and derive a calibration matrix for the LWE measurement in closed-loop operation with our sensor. Using the sensor mask present in Subaru/SCExAO, we perform first tests on a real system with an internal source and on sky, showing the ability of our sensor path to control these wavefront errors in the small aberration regime. Our approach looks very promising for the IE issue in the perspective of ELTs.
AB - Island effects (IE) are critical piston difierential aberrations between neighbouring pupil segments on ground-based telescopes that degrade the quality of Adaptive optics (AO) images on 8m-class telescopes in good observing conditions. Due to telescope architecture, these residual errors lead to a loss of observing time, up to 20% as observed on the VLT during the direct imaging observations of planetary companions with SPHERE. These effects are expected to be even more critical with ELTs as these observatories will present more complex architectures. Measuring these effects however prove very challenging for most of the state-of-the-art AO wavefront sensors. A first successful diagnosis of these aberrations has recently been obtained on SPHERE with ZELDA, the Zernike wavefront sensor for the measurement of residual aberrations in coronagraphic systems. In this communication, we focus on the Asymmetric Pupil Fourier-wavefront sensor (APF-WFS) that relies on point source images to retrieve wavefront errors with an interferometric analysis. Assuming the archetypal four-quadrant aperture geometry in 8m class telescopes, we define aberration modes based on piston, tip, and tilt over the pupil quadrants and derive a calibration matrix for the LWE measurement in closed-loop operation with our sensor. Using the sensor mask present in Subaru/SCExAO, we perform first tests on a real system with an internal source and on sky, showing the ability of our sensor path to control these wavefront errors in the small aberration regime. Our approach looks very promising for the IE issue in the perspective of ELTs.
KW - Adaptive optics
KW - Data analysis
KW - High angular resolution
KW - Telescopes
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M3 - Paper
AN - SCOPUS:85049306092
Y2 - 25 June 2017 through 30 June 2017
ER -