Method of reducing photon noise and turbulence for laser guide-star detection on large-aperture telescopes

Abstract

Adaptive optics systems (AOSs) rely on good estimation of a distorted wavefront. Two problems make centroid detection difficult, namely, the problem of a relatively large subaperture that brings high-order aberrations and that of a large laser guide-star spot that brings in a large photon noise. To solve these problems, we proposed an estimation method based on Poisson statistics to reduce the photon noise, and the high-order aberrations are partly separated from a spot image to well estimate the slope in the subaperture. Simulation results indicate that our method performs better than the weighted center-of-gravity (WCOG) method and correlation method (CM). Under the condition of SNR =20 and r0=13cm The root-mean-square values of the residual wavefront using the proposed method are approximately 10%, 50%, and 35% lower than those of the COG, WCOG, and CM, respectively. The proposed method would be highly beneficial for ground-based astronomical AO systems intended to provide moderate to high Strehl ratios at near infrared wavelengths on larger than 10m-aperture telescopes.