AO with LGS and mesospheric layer sensing

We analyze the image quality of an extraterrestrial object imaged by astronomical optical systems through the turbulent atmosphere. The relative increase of the Strehl parameter is calculated under adaptive corrections with laser guide star. We compare the efficiency of adaptive correction for different types of the guide sources. The calculations are performed for different models of the vertical distribution of the structural parameter of the refractive index of the turbulent atmosphere. A special wavefront sensor is applied, which operates with a full-aperture collimated laser beam as a reference wave. This layer-oriented wavefront sensor is used to reconstruct the continuous phase of the reference wave. Our results show that the parameters of the reconstructed field are quite close to that of a plane wave. A significant increase of the Strehl parameter indicates excellent correction of higher order modes, which are usually difficult to sense and correct with traditional LGS techniques using a focused laser beam. A comparative analysis of various atmospheric models revealed some noticeable differences in correlation radii for the plane and spherical waves.

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