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Sensing and Control of Segmented Mirrors with a Pyramid Wavefront Sensor in the Presence of Spiders by Schwartz, Noah; Sauvage, Jean-François; Correia, Carlos; Petit, Cyril; Quiros-Pacheco, Fernando; Fusco, Thierry; Dohlen, Kjetil; Hadi, Kacem El; Thatte, Niranjan; Clarke, Fraser; Paufique, Jérome; Vernet, Joel is a scholarly article available to read on EtoBox.

What is Sensing and Control of Segmented Mirrors with a Pyramid Wavefront Sensor in the Presence of Spiders about?

The segmentation of the telescope pupil (by spiders & the segmented M4) create areas of phase isolated by the width of the spiders on the wavefront sensor (WFS), breaking the spatial continuity of the wavefront. The poor sensitivity of the Pyramid WFS (PWFS) to differential piston leads to badly seen and therefore uncontrollable differential pistons. In close loop operation, differential pistons between segments will settle around integer values of the average sensing wavelength. The differential pistons typically range from one to ten times the sensing wavelength and vary rapidly over time, leading to extremely poor performance. In addition, aberrations created by atmospheric turbulence will contain large amounts of differential piston between the segments. Removing piston contribution over each of the DM segments leads to poor performance. In an attempt to reduce the impact of unwanted differential pistons that are injected by the AO correction, we compare three different approaches. We first limit ourselves to only use the information measured by the PWFS, in particular by reducing the modulation. We show that using this information sensibly is important but will not be sufficie

Author

Schwartz, Noah; Sauvage, Jean-François; Correia, Carlos; Petit, Cyril; Quiros-Pacheco, Fernando; Fusco, Thierry; Dohlen, Kjetil; Hadi, Kacem El; Thatte, Niranjan; Clarke, Fraser; Paufique, Jérome; Vernet, Joel

Published

2018

Language

EN