Overview of focal plane wavefront sensors to correct for the low wind effect on SUBARU/SCExAO

S. Vievard, S. P. Bos, F. Cassaing, A. Ceau, O. Guyon, N. Jovanovic, C. U. Keller, J. Lozi, F. Martinache, D. Mary, A. Montmerle-Bonnefois, L. M. Mugnier, M. N’Diaye, B. Norris, A. Sahoo, J. F. Sauvage, F. Snik, M. J. Wilby, A. Wong

Research output: Contribution to conferencePaper

Abstract

The Low Wind Effect (LWE) refers to a phenomenon that occurs when the wind speed inside a telescope dome drops below 3m/s creating a temperature gradient near the telescope spider. This produces phase discontinuities in the pupil plane that are not detected by traditional Adaptive Optics (AO) systems such as the pyramid wavefront sensor or the Shack-Hartmann. Considering the pupil as divided in 4 quadrants by regular spiders, the phase discontinuities correspond to piston, tip and tilt aberrations in each quadrant of the pupil. Uncorrected, it strongly decreases the ability of high contrast imaging instruments utilizing coronagraphy to detect exoplanets at small angular separations. Multiple focal plane wavefront sensors are currently being developed and tested on the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument at Subaru Telescope: Among them, the Zernike Asymmetric Pupil (ZAP) wavefront sensor already showed on-sky that it could measure the LWE induced aberrations in focal plane images. The Fast and Furious algorithm, using previous deformable mirror commands as temporal phase diversity, showed in simulations its efficiency to improve the wavefront quality in the presence of LWE. A Neural Network algorithm trained with SCExAO telemetry showed promising PSF prediction on-sky. The Linearized Analytic Phase Diversity (LAPD) algorithm is a solution for multi-aperture cophasing and is studied to correct for the LWE aberrations by considering the Subaru Telescope as a 4 sub-aperture instrument. We present the different algorithms, show the latest results and compare their implementation on SCExAO/SUBARU as real-time wavefront sensors for the LWE compensation.

Original languageEnglish (US)
StatePublished - Jan 1 2019
Event6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019 - Quebec City, Canada
Duration: Jun 9 2019Jun 14 2019

Conference

Conference6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019
CountryCanada
CityQuebec City
Period6/9/196/14/19

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Keywords

  • Coronography
  • Focal plane wavefront sensing
  • High contrast imaging
  • Low wind effect
  • SCExAO
  • Spiders

ASJC Scopus subject areas

  • Space and Planetary Science
  • Control and Systems Engineering
  • Mechanical Engineering
  • Electronic, Optical and Magnetic Materials
  • Astronomy and Astrophysics
  • Instrumentation

Cite this

Vievard, S., Bos, S. P., Cassaing, F., Ceau, A., Guyon, O., Jovanovic, N., Keller, C. U., Lozi, J., Martinache, F., Mary, D., Montmerle-Bonnefois, A., Mugnier, L. M., N’Diaye, M., Norris, B., Sahoo, A., Sauvage, J. F., Snik, F., Wilby, M. J., & Wong, A. (2019). Overview of focal plane wavefront sensors to correct for the low wind effect on SUBARU/SCExAO. Paper presented at 6th International Conference on Adaptive Optics for Extremely Large Telescopes, AO4ELT 2019, Quebec City, Canada.