CATS: continuous turbulence characterization station for both optical link and astronomical support

The optical turbulence measurement and characterization has become an essential information for optical link (telecommunication, telemetry, time transfert, ...) and for high-angular resolution imagining in astron- omy. For example, it has an impact on the quality and on the bit error rate of optical communication signals and it decrease the resolution of astronomical images. The J.L. Lagrange Laboratory of the Observatoire de la Côte d’Azur has a long and recognized expertise in atmospheric optics and turbulence for astronomical purposes. We have developed recently a new generation of autonomous instruments for daytime and night- time atmospheric optical turbulence measurement. In 2015, a complete instrumental platform, the Calern Atmospheric Turbulence Station (CATS) has been installed at the Calern observatory. CATS is an auto- matic station equipped with a set of complementary instruments using original techniques for monitoring optical turbulence from the first meters above the ground up to the top of the atmosphere including the dome seeing. The station is based on 4 instruments. PML measures continuously the vertical profiles of the refractive index structure constant Cn2 with a high vertical resolution (~ 100m at ground level). GDIMM monitors the wavefront coherence parameters (seeing, isoplanatic angle, coherence time, scintillation, outer scale). A weather station provides the ground meteorological conditions (pressure, temperature, relative humidity, wind speed and direction). And the nighttime cloud fraction is given by an all-sky camera. Another instrument called INTENSE (INdoor TurbulENce Sensor) is occasionally associated with CATS station to measure the seeing inside the dome of the 1.5m MeO telescope to evaluate its contribution to the whole turbulence. A new tool has been integrated to CATS station consisting in a forcasting model using the Weather Research and Forecasting (WRF) system coupled to a turbulence model to predict daytime and nighttime meteorological and optical turbulence conditions for the next 48h.