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

Griffiths, Ryan; Osborn, James; Farley, Oliver; Butterley, Timothy; Townson, Matthew; Wilson, Richard


Ryan Griffiths

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Ollie Farley
Post Doctoral Research Associate


Hamid Hemmati

Bryan S. Robinson


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.


Griffiths, R., Osborn, J., Farley, O., Butterley, T., Townson, M., & Wilson, R. (2023). The 24hSHIMM: a continuous day and night turbulence monitor for optical communications. In H. Hemmati, & B. S. Robinson (Eds.), Proceedings Volume 12413, Free-Space Laser Communications XXXV.

Conference Name Free-Space Laser Communications XXXV
Conference Location San Francisco, United States
Start Date Jan 28, 2023
End Date Feb 3, 2023
Acceptance Date Jan 18, 2023
Online Publication Date Mar 15, 2023
Publication Date Mar 15, 2023
Deposit Date Mar 21, 2024
Publisher SPIE
Volume 12413
Series ISSN 0277-786X
Book Title Proceedings Volume 12413, Free-Space Laser Communications XXXV
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