The European Solar Telescope will have an aperture of 4.2 m, an Adaptive Secondary Mirror (ASM) and a complex Multi Conjugate Adaptive Optics (MCAO) solution to satisfy the science quality requirements. A testbench has been designed to test different AO strategies (SCAO, GLAO and MCAO) with a scaled model of the EST MCAO system. The objective of this testbench is to obtain knowledge about the different optical, wavefront reconstruction and control challenges of the MCAO problem. One key difference between night AO and solar AO is the use of correlations as a necessary process to perform the slopes computation when SH-WFS are used. Furthermore, the correlation algorithms have a known impact on the performance of the adaptive optics, as it can introduce measurement errors in the control loop.

This work analyses the computation performance of the typical correlations methods, based on distance norms (absolute difference and squared difference) or Fast Fourier Transform (FFT). It will be assed the impact of subpixel algorithms in terms of computation efficiency as well. Our study will also include a comparison of the different algorithms performance in closed-loop to develop the trade-off between computational efficiency and the resulting control quality. As a final point, we will be stating the scalability of these results to the EST case discussing possible methods to improve the overall processing load, such as parallelization.

Nicolás Rodríguez, Instituto de Astrofísica de Canarias (IAC)