Daytime forecast of optical turbulence for optical communications

Abstract

In recent years, forecast of optical turbulence has been developed for astronomical sites. It enables flexible scheduling of observations during the night, and improves the control of adaptive optics systems. Nowadays, there is also a need for optical turbulence forecast during daytime at locations considered for future satellite-to-ground optical communications, for example in cities. In this work, a numerical approach to forecast refractive index structure parameter (Cn2) profiles for optical communication sites is presented. It relies on the Weather Research and Forecasting software, with the boundary layer considered separately. Indeed, it is shown that during daytime and at non-astronomical sites, the boundary layer has a great impact on seeing conditions. This motivates the use of hybrid Cn2 profiles, separating the free atmosphere from the surface layer. This approach is applied to Tenerife, Spain, where the European Space Agency has already built an optical ground station. Measurements of integrated parameters (seeing) are available at this location, and are compared with the forecast integrated parameters. The current limitations of the model can thereby be highlighted