Refined Adaptive Optics simulation with wide field of view for the ELT.


M. Chebbo(1), T. Fusco(2), J.-F. Sauvage(2), J.-M. Conan(2), S. Meimon(2), B. Le Roux(1)


(1) Observatoire de Marseille – LAM (2) ONERA


Refined simulation tools for wide field AO systems (such as MOAO, MCAO or LTAO) on ELTs present new challenges. Increasing the number of degrees of freedom (scales as the square of the telescope diameter) makes the standard codes useless due to the huge number of operations to be performed at each step of the AO loop process. This computational burden requires new approaches in the computation of the DM voltages from WFS data. The classical matrix inversion and the matrix vector multiplication have to be replaced by a cleverer iterative resolution of the Least Square or Minimum Mean Square Error criterion (based on sparse matrices approaches).

Moreover, for this new generation of AO systems, concepts themselves will become more complex: data fusion coming from multiple Laser and natural guide stars will have to be optimized, mirrors covering all the field of view associated to dedicated mirrors inside the scientific instrument itself will have to be coupled with split or integrated tomography schemes, differential pupil or/and field rotations will have to be considered, etc … All these new entries should be carefully simulated, analysed and quantified in terms of performance before any implementation in AO systems.

In this paper we present a new E2E simulator, developed to deal with all these specific ELT challenges. It is based on an iterative resolution of the linear model with high number of degrees of freedom (using the sparse matrix) and includes new concepts of filtering and coupling between LGS and NGS to effectively manage modes such as tip / tilt and defocus in the entire process of tomographic reconstruction. The first application of this tool in the frame of the EAGLE project, a flagship instrument of the future E-ELT combining all these issues, is presented.

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