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Abstract: The concept of pyramid wavefront sensors PWFS has been around about adecade by now. However, there is still a great lack of characterizingmeasurements that allow the best operation of such a system under real lifeconditions at an astronomical telescope. In this article we, therefore,investigate the behavior and robustness of the pyramid infrared wavefrontsensor PYRAMIR mounted at the 3.5 m telescope at the Calar Alto Observatoryunder the influence of different error sources both intrinsic to the sensor,and arising in the preceding optical system. The intrinsic errors includediffraction effects on the pyramid edges and detector read out noise. Theexternal imperfections consist of a Gaussian profile in the intensitydistribution in the pupil plane during calibration, the effect of an opticallyresolved reference source, and noncommon-path aberrations. We investigated theeffect of three differently sized reference sources on the calibration of thePWFS. For the noncommon-path aberrations the quality of the response of thesystem is quantified in terms of modal cross talk and aliasing. We investigatethe special behavior of the system regarding tip-tilt control. From ourmeasurements we derive the method to optimize the calibration procedure and thesetup of a PWFS adaptive optics AO system. We also calculate the totalwavefront error arising from aliasing, modal cross talk, measurement error, andfitting error in order to optimize the number of calibrated modes for on-skyoperations. These measurements result in a prediction of on-sky performance forvarious conditions.

Autor: D. Peter, M. Feldt, B. Dorner, T. Henning, S. Hippler, J. Aceituno


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