Temporal variability and statistics of the Strehl ratio in adaptive-optics images

TL;DR

This study analyzes the temporal variability and statistical properties of the instantaneous Strehl ratio in adaptive optics images, revealing insights into phase variance behavior and the impact of wavefront scaling.

Contribution

It provides a detailed statistical analysis of the Strehl ratio and phase variance in adaptive optics, including testing the Marechal approximation and modeling phase variance distribution.

Findings

The phase variance fits a three-parameter Gamma distribution.

Scaling of reconstructed wavefronts significantly affects Strehl ratio distribution.

Negative skewness observed in the Strehl ratio distribution explained by Marechal approximation.

Abstract

We have investigated the temporal variability and statistics of the "instantaneous" Strehl ratio. The observations were carried out with the 3.63-m AEOS telescope equipped with a high-order adaptive optics system. In this paper Strehl ratio is defined as the peak intensity of a single short exposure. We have also studied the behaviour of the phase variance computed on the reconstructed wavefronts. We tested the Marechal approximation and used it to explain the observed negative skewness of the Strehl ratio distribution. The estimate of the phase variance is shown to fit a three-parameter Gamma distribution model. We show that simple scaling of the reconstructed wavefronts has a large impact on the shape of the Strehl ratio distribution.