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Comparison of Reconstruction and Control algorithms on the ESO end-to-end simulator OCTOPUS

Abstract 186

Submitted by Iciar MONTILLA


I. Montilla (1), C. Béchet (2, 3), M. LeLouarn (2), C. Correia (4), M. Tallon (3), M. Reyes (1), É. Thiébaut (3)


(1) IAC; (2) ESO; (3) CRAL; (4) ONERA


Extremely Large Telescopes are very challenging concerning their Adaptive Optics requirements. Their diameters, the specifications demanded by the science for which they are being designed for, and the planned use of Extreme Adaptive Optics systems, imply a huge increment in the number of actuators in the deformable mirrors. It is necessary to study new reconstruction algorithms to implement the real time control in Adaptive Optics at the required speed. In the frame of the E-ELT Design Study (European Community’s FP6) we have studied the performance, applied to the case of the European ELT, of three different algorithms: the matrix-vector multiplication (MVM) algorithm, considered as a reference; the Fractal Iterative Method (FrIM); and the Fourier Transform Reconstructor (FTR). The algorithms have been tested on ESO´s OCTOPUS software, which simulates the atmosphere, the deformable mirror, the sensor and the closed-loop control. The MVM is the default reconstruction and control method implemented in OCTOPUS, but it scales in O(N2) operations per loop so it is not considered as a "fast algorithm" for wave-front reconstruction and control on an Extremely Large Telescope. The two other methods are the fast algorithms studied in the E-ELT Design Study. The performance, as well as their response in the presence of noise and with various atmospheric conditions, has been compared for the first light Single Conjugate Adaptive Optics configuration for the E-ELT, with a 42 m diameter and with a total amount of 5402 actuators. Those comparisons made on a common simulator allow to enhance the pros and cons of the various methods, and give us a better understanding of the type of reconstruction algorithm that an ELT demands.

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