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The effect of a coronagraph on the statistics of Adaptive Optics Pinned Speckles

Published online by Cambridge University Press:  11 October 2004

C. Aime ,
R. Soummer ,
C. Aime  and
R. Soummer
C. Aime
Affiliation:
UMR 6525 LUAN, University of Nice Sophia-Antipolis, 06108 Nice Cedex 2, France
R. Soummer
Affiliation:
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD21218, USA
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Abstract

In this communication we study the statistics of Adaptive Optics remnant speckles, and we discuss how a coronagraph can defeat the noise associated with these speckles. At high Strehl Ratio regimes, residual speckles are pinned on the diffraction rings of the airy pattern. It can be shown that these speckles are due to small defaults of the wavefront, amplified by the coherent part of the wave and that the statistics of their intensity can be described by a modified Rice distribution. At low flux levels, a Poisson-Mandel transformation provides an analytical expression of the Probablility Density Function. We show the results of a numerical simulation and compare the results to the theoretical model. Simple analytical expressions can be derived for the variance of the noise.We discuss the efficiency of a coronagraph in terms of Signal to Noise Ratio, based on the analysis of the noise contributions which can be reduced by a coronagraph.

Type
Research Article
Information
European Astronomical Society Publications Series , Volume 12: Astronomy with High Contrast Imaging II , 2004 , pp. 89 - 101
Copyright
© EAS, EDP Sciences, 2004

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