Demonstrating the first 24-hour continuous vertical monitoring of the atmospheric optical turbulence

Abstract

We report what is believed to be the first example of fully continuous, 24-hour vertical monitoring of atmospheric optical turbulence. This is achieved using a novel instrument, the 24-hour Shack-Hartmann Image Motion Monitor (24hSHIMM). Optical turbulence is a fundamental limitation for applications such as free-space optical communications, where it limits the achievable bandwidth, and ground-based optical astronomy, restricting the observational precision. Knowledge of the turbulence enables us to select the best sites, design optical instrumentation and optimise the operation of ground-based optical systems. To illustrate our advance we show a 35-hour continuous measurement of the vertical optical turbulence coherence length, time and angle, the Rytov variance and a four-layer vertical profile. Due to its portability and ability to work in stronger turbulence, the 24hSHIMM can also operate in urban locations. We show that this single instrument can replace the large number of turbulence measurement solutions, providing the field with a single optical turbulence monitor, for all but the most demanding of applications.