The 24hSHIMM: a continuous day and night turbulence monitor for optical communications

Ryan Griffiths*, James Osborn, Ollie Farley, Timothy Butterley, Matthew J. Townson, Richard Wilson

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

23 Downloads (Pure)


We present the 24-hour Shack-Hartmann Image Motion Monitor (24hSHIMM), the first truly continuous, 24-hour optical turbulence monitor. Atmospheric optical turbulence is a significant limitation for free-space optical communications and other technologies. Knowledge of the turbulence conditions allows for the selection of favourable sites for optical ground stations. It also enhances operations though providing data for assimilation into turbulence forecasting models and real-time monitoring of conditions. The 24hSHIMM uses a Shack-Hartmann wavefront sensor to measure a low-resolution vertical optical turbulence profile, from which the coherence length, angle and Rytov variance are calculated. Additionally a vertical wind speed profile from meteorological forecast data is used to calculate the coherence time. Due to its portability, the instrument can operate in a wide variety of locations, even urban, to provide continuous information about the atmospheric turbulence. To demonstrate this, we show parameters recorded at the astronomical observatory in La Palma for a continuous 36-hour period. With its wide array of capabilities, the 24hSHIMM offers strong support for future research in free-space optics.

Original languageEnglish
Title of host publicationFree-Space Laser Communications XXXV
EditorsHamid Hemmati, Bryan S. Robinson
Place of PublicationBellingham, US
Number of pages5
ISBN (Electronic)9781510659315
Publication statusPublished - 15 Mar 2023
Externally publishedYes
EventFree-Space Laser Communications XXXV 2023 - San Francisco, United States
Duration: 30 Jan 20231 Feb 2023

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceFree-Space Laser Communications XXXV 2023
Country/TerritoryUnited States
CitySan Francisco

Cite this