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Breaking the FoV vs. thickness rule in MCAO

Abstract 111

Submitted by Roberto RAGAZZONI


R. Ragazzoni


INAF - Astronomical Observatory of Padova (ITALY)


In current approaches for MCAO the extension of the Field of View (i.e. the angles of the rays used to sense a certain layer) is inversely proportional to the thickness of the layer that can be corrected up to a certain extent. This contributes to makes the LGS MCAO correction more demanding in ELTs (as rays are coming from a larger angle) and mades MCAO with solely NGSs to an upper limit in sky coverage (because extending the FoV to catch the light from more stars translates into a poorer correction). This result, however, is obtained under closed-loop, linear fashion, regimes. I show how to overcome this, leading to ultimate geomterical limits in terms of pupil overlap, enlarging the available FoV for searching suitable natural guide stars by an order of magnitude, opening new perspectives for LGS-less MCAO system for ELTs.

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