Estimating Atmospheric Wind Speeds From Gemini Planet Imager AO Telemetry

TL;DR

This paper introduces two novel methods to estimate atmospheric wind speeds from AO telemetry data, aiding in better characterization of turbulence for improved adaptive optics performance.

Contribution

It presents two new techniques for estimating effective wind velocity using pseudo-open loop WFS slopes, validated with simulations and preliminary Gemini data.

Findings

Methods successfully estimate wind velocity from telemetry

Simulated results validate the approaches

Preliminary Gemini data shows promising estimates

Abstract

The Earth's atmosphere is comprised of turbulent layers that result in speckled and blurry images from ground-based visible and infrared observations. Adaptive Optics (AO) systems are employed to measure the perturbed wavefront with a wavefront sensor (WFS) and correct for these distortions with a deformable mirror. Therefore, understanding and characterising the atmosphere is crucial for the design and functionality of AO systems. One parameter for characterizing the atmosphere is the atmospheric coherence time, which is a function of the effective wind velocity of the atmosphere. This parameter dictates how fast the AO system needs to correct for the atmosphere. If not fast enough, phenomena such as the wind butterfly effect can occur, hindering high-contrast coronographic imaging. This effect is a result of fast, strong, high-altitude turbulent layers. This paper presents two methods for estimating the effective wind velocity, using pseudo-open loop WFS slopes. The first method uses a spatial-temporal covariance map and the second uses the power spectral density of the defocus term. We show both simulated results and preliminary results from the Gemini Planet Imager AO telemetry.