# Testing turbulence model at metric scales with mid-infrared VISIR images at the VLT

## TL;DR

This study analyzes turbulence at various scales using mid-infrared and visible images from the VLT, revealing deviations from the Kolmogorov model and suggesting potential for diffraction-limited imaging at large apertures without adaptive optics.

## Contribution

It demonstrates that turbulence at the VLT deviates from Kolmogorov theory and is better modeled by the von Karman model with a specific outer scale, impacting future high-resolution imaging.

## Key findings

- Turbulence departs from Kolmogorov model at VLT scales.
- Data fits von Karman model with ~30 m outer scale.
- Infrared image quality improves faster than lambda^{-1/5}.

## Abstract

We probe turbulence structure from centimetric to metric scales by simultaneous imagery at mid-infrared and visible wavelengths at the VLT telescope and show that it departs significantly from the commonly used Kolmogorov model. The data can be fitted by the von Karman model with an outer scale of the order of 30 m and we see clear signs of the phase structure function saturation across the 8-m VLT aperture. The image quality improves in the infrared faster than the standard lambda^{-1/5} scaling and may be diffraction-limited at 30-m apertures even without adaptive optics at wavelengths longer than 8 micron.