Demonstrating predictive wavefront control with the Keck II near-infrared pyramid wavefront sensor. (arXiv:1909.05302v1 [astro-ph.IM])
<a href="http://arxiv.org/find/astro-ph/1/au:+Jensen_Clem_R/0/1/0/all/0/1">Rebecca Jensen-Clem</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bond_C/0/1/0/all/0/1">Charlotte Z. Bond</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cetre_S/0/1/0/all/0/1">Sylvain Cetre</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+McEwen_E/0/1/0/all/0/1">Eden McEwen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wizinowich_P/0/1/0/all/0/1">Peter Wizinowich</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ragland_S/0/1/0/all/0/1">Sam Ragland</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mawet_D/0/1/0/all/0/1">Dimitri Mawet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Graham_J/0/1/0/all/0/1">James Graham</a>
The success of ground-based instruments for high contrast exoplanet imaging
depends on the degree to which adaptive optics (AO) systems can mitigate
atmospheric turbulence. While modern AO systems typically suffer from
millisecond time lags between wavefront measurement and control, predictive
wavefront control (pWFC) is a means of compensating for those time lags using
previous wavefront measurements, thereby improving the raw contrast in the
post-coronagraphic science focal plane. A method of predictive control based on
Empirical Orthogonal Functions (EOF) has previously been proposed and
demonstrated on Subaru/SCExAO. In this paper we present initial tests of this
method for application to the near-infrared pyramid wavefront sensor (PYWFS)
recently installed in the Keck II AO system. We demonstrate the expected
root-mean-square wavefront error and contrast benefits of pWFC based on
simulations, applying pWFC to on-sky telemetry data saved during commissioning
of the PYWFS. We discuss how the performance varies as different temporal and
spatial scales are included in the computation of the predictive filter. We
further describe the implementation of EOF pWFC within the PYWFS dedicated
real-time controller, and, via daytime testing at the observatory, we
demonstrate the performance of pWFC in real time when pre-computed phase
screens are applied to the deformable mirror.
The success of ground-based instruments for high contrast exoplanet imaging
depends on the degree to which adaptive optics (AO) systems can mitigate
atmospheric turbulence. While modern AO systems typically suffer from
millisecond time lags between wavefront measurement and control, predictive
wavefront control (pWFC) is a means of compensating for those time lags using
previous wavefront measurements, thereby improving the raw contrast in the
post-coronagraphic science focal plane. A method of predictive control based on
Empirical Orthogonal Functions (EOF) has previously been proposed and
demonstrated on Subaru/SCExAO. In this paper we present initial tests of this
method for application to the near-infrared pyramid wavefront sensor (PYWFS)
recently installed in the Keck II AO system. We demonstrate the expected
root-mean-square wavefront error and contrast benefits of pWFC based on
simulations, applying pWFC to on-sky telemetry data saved during commissioning
of the PYWFS. We discuss how the performance varies as different temporal and
spatial scales are included in the computation of the predictive filter. We
further describe the implementation of EOF pWFC within the PYWFS dedicated
real-time controller, and, via daytime testing at the observatory, we
demonstrate the performance of pWFC in real time when pre-computed phase
screens are applied to the deformable mirror.
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