In the design of the future generation ELTs the support structures for the secondary mirror (also known as spiders) lead to a piston on each of the pupil segments created by the spiders, known as ”island effect”. In this talk we focus on fast and stable reconstruction methods to cope with the island effect. We present and compare wavefront reconstruction algorithms and highlight their performance in a METIS- like AO system. We focus on FEWHA (Finite Element-Wavelet Hybrid Algorithm), Poke Matrix Inversion using a set of predefined DM influence functions and new methods for a direct segment piston estimation in combination with the P-CuReD (Preprocessed Cumulative Reconstructor with Domain decomposition). The results are backed up by Octopus (the full AO end-to-end simulator from ESO) simulations highlighting stable Strehl ratios for our simulation setting.
Andreas Obereder, Stefan Raffetseder, Victoria Hutterer, and Iuliia Shatokhina, "Dealing with spiders on ELTs: using a Pyramid WFS to overcome residual piston effects," Proc. SPIE 10703, Adaptive Optics Systems VI, 107031D (Presented at SPIE Astronomical Telescopes + Instrumentation: June 13, 2018; Published: 10 July 2018); https://doi.org/10.1117/12.2313419.
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