Atmospheric turbulence modelling and monitoring for satellite-to-ground optical communications

Free-space optical communication (FSOC) between satellites and the ground will revolutionize space communications, boosting global connectivity and enabling increased data exchange for Earth observation, deep space probes and human space exploration. As this revolution is ongoing, the propagation of optical communication signals in the atmosphere remains a significant challenge, namely due to atmospheric turbulence. The influence of atmospheric turbulence on optical waves is known as optical turbulence (OT), which is the focus of this thesis. While numerous OT models and monitoring instruments have been developed for astronomical sites, facing similar issues affecting the quality of observations, their application to FSOC sites is limited. By reviewing existing astronomical OT models and instruments, this thesis highlights their limitations at FSOC sites. It also presents novel OT models based on meteorological parameters derived from radiosonde observations or numerical weather prediction simulations. These new models enable continuous OT prediction, for both daytime and nighttime operations, with a particular focus on the atmospheric boundary layer. Furthermore, several approaches to obtain OT measurements from wavefront sensor observations are explored in this work. The integration of OT measurements with prediction models to improve short-term OT forecast is presented, paving the way for the future development and operation of robust FSOC networks.