Projected Pupil Plane Pattern (PPPP) with artificial Neural Networks

Yang, H; Gonzalez, C; Bharmal, NA; de Cos, F

doi:10.1093/mnras/stz1362

Projected Pupil Plane Pattern (PPPP) with artificial Neural Networks

Yang, H; Gonzalez, C; Bharmal, NA; de Cos, F

Authors

H Yang

C Gonzalez

Dr Nazim Bharmal n.a.bharmal@durham.ac.uk
Senior Adaptive Optics Scientist

F de Cos

Abstract

Focus anisoplanatism is a significant measurement error when using one single laser guide star (LGS) in an Adaptive Optics (AO) system, especially for the next generation of extremely large telescopes. An alternative LGS configuration, called Projected Pupil Plane Pattern (PPPP) solves this problem by launching a collimated laser beam across the full pupil of the telescope. If using a linear, modal reconstructor, the high laser power requirement (∼1000 W) renders PPPP uncompetitive with Laser Tomography AO. This work discusses easing the laser power requirements by using an artificial Neural Network (NN) as a non-linear reconstructor. We find that the non-linear NN reduces the required measurement signal-to-noise ratio (SNR) significantly to reduce PPPP laser power requirements to ∼200 W for useful residual wavefront error (WFE). At this power level, the WFE becomes 160 nm root mean square (RMS) and 125 nm RMS when r0 = 0.098 m and 0.171 m respectively for turbulence profiles which are representative of conditions at the ESO Paranal observatory. In addition, it is shown that as a non-linear reconstructor, a NN can perform useful wavefront sensing using a beam-profile from one height as the input instead of the two profiles required as a minimum by the linear reconstructor.

Citation

Yang, H., Gonzalez, C., Bharmal, N., & de Cos, F. (2019). Projected Pupil Plane Pattern (PPPP) with artificial Neural Networks. Monthly Notices of the Royal Astronomical Society, 487(1), 1480-1487. https://doi.org/10.1093/mnras/stz1362

Journal Article Type	Article
Acceptance Date	May 11, 2019
Online Publication Date	May 22, 2019
Publication Date	Jul 31, 2019
Deposit Date	May 21, 2019
Publicly Available Date	May 23, 2019
Journal	Monthly Notices of the Royal Astronomical Society
Print ISSN	0035-8711
Electronic ISSN	1365-2966
Publisher	Royal Astronomical Society
Peer Reviewed	Peer Reviewed
Volume	487
Issue	1
Pages	1480-1487
DOI	https://doi.org/10.1093/mnras/stz1362