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Subaru Seminars are
usually held in Room 104 of the Hilo Base Facility, adjacent
to the main lobby. Everyone is welcome to attend. If you would like to
give a seminar, please contact Subaru seminar organizers
(Hyewon Suh, Tae-Soo Pyo, Nagayoshi Ohashi)
by email : sseminar_at_subaru.naoj.org (please change"_at" to @).
May 17, Friday, 3pm in 104A
How to deal with the Pyramid Wavefront Sensor non-linearity: use of an analytic model to predict the Optical Gains in closed loop operation
Vincent Chambouleyron (LAM/ONERA, France)
Extremely Large Telescopes have chosen the Pyramid Wave-Front Sensor (PWFS) over the widely used Shack-Hartmann Wave-Front Sensor (SHWFS) to perform their Single Conjugate Adaptive Optics (SCAO) mode. The PWFS is a Fourier-filtering based sensor which has proven to be strongly efficient for astronomical purposes. It however shows non-linearity behaviors that lead to a reduction of its sensitivity while working around a non-null phase. This effect degrades the performance of the closed loop and prevent from accurate correction of Non-Common-Path Aberrations (NCPA). Thanks to a new breakthrough in the theoretical description of the PFWS which use a convolutive model to describe the sensor, we show that it is possible to analytically predict the behavior of the PWFS in closed-loop operation. This model allows us to explore the impact of residual phases on the properties of the PFWS measurements in term of sensitivity and dynamic range. We used the benefits of this theoretical approach to demonstrate that it is possible to build robust and agile strategies to control our system by compensating the measurements of the PWFS with a minimum knowledge of the turbulence shape.