Estimation of atmospheric turbulence parameters from Shack-Hartmann wavefront sensor measurements

Abstract

The estimation of atmospheric turbulence parameters is of relevance for: a) site evaluation & characterisation; b) prediction of the point spread function; c) live assessment of error budgets and optimisation of adaptive optics performance; d) optimisation of fringe trackers for long baseline optical interferometry. The ubiquitous deployment of Shack-Hartmann wavefront sensors in large telescopes makes them central for atmospheric turbulence parameter estimation via adaptive optics telemetry. Several methods for the estimation of the Fried parameter and outer scale have been developed, most of which are based on the fitting of Zernike polynomial coefficients variances reconstructed from the telemetry. The non-orthogonality of Zernike polynomial derivatives introduces modal cross coupling, which affects the variances. Furthermore, the finite resolution of the sensor introduces aliasing. In this article the impact of these effects on atmospheric turbulence parameter estimation is addressed with simulations. It is found that cross coupling is the dominant bias. An iterative algorithm to overcome it is presented. Simulations are conducted for typical ranges of the outer scale (4 to 32m), Fried parameter (10 cm) and noise in the variances (signal-to-noise ratio of 10 and above). It is found that, using the algorithm, both parameters are recovered with sub-percent accuracy.

arXiv commentAccepted for publication by MNRAS

References in corpus (12)

• The bright end of the z ~ 7 UV Luminosity Function from a wide and deep HAWK-I survey
• Atmospheric turbulence forecasting with a General Circulation Model for Cerro Paranal
• Ground-based astrometry with wide field imagers. V. Application to near-infrared detectors: HAWK-I@VLT/ESO
• Turbulence velocity profiling for high sensitivity and vertical-resolution atmospheric characterization with Stereo-SCIDAR
• Testing turbulence model at metric scales with mid-infrared VISIR images at the VLT
• Zernike expansions of derivatives and Laplacians of the Zernike circle polynomials
• Atmospheric image blur with finite outer scale or partial adaptive correction
• Seeing, Wind and Outer Scale Effects on Image Quality at the Magellan Telescopes
• Peak-locking centroid bias in Shack-Hartmann wavefront sensing
• Statistics of Turbulence Parameters at Maunakea using multiple wave-front sensor data of RAVEN
• Comparison of fringe-tracking algorithms for single-mode near-infrared long-baseline interferometers
• Atmospheric turbulence profiling with unknown power spectral density

Cited by in corpus (6)

• The Three Hundred Project: quest of clusters of galaxies morphology and dynamical state through Zernike Polynomials
• PRIME: Psf Reconstruction and Identification for Multiple sources characterization Enhancement. Application to Keck NIRC2 imager
• Pushing Point spread function reconstruction to the next level. Application to SPHERE/ZIMPOL
• Integrated turbulence parameters' estimation from NAOMI adaptive optics telemetry data
• Adaptive Optics Telemetry Standard: Design and specification of a novel data exchange format
• Towards virtual access of adaptive optics telemetry data