To evaluate the results from studies on atmospheric propagation and laser remote effects, the prevailing atmosphere properties are fully taken into account. The atmosphere acts on the laser radiation through its limited optical transmissivity, through the presence of aerosols and through turbulence induced refractive index fluctuations. The consequences are a general weakening of the power along the propagation path, a reduction of the radiation intensity at the target and reduced positioning accuracy. Weather measurement technology tailored to the issues related to atmospheric propagation and ongoing studies on the behaviour of the optical turbulence near the ground allow the integration of the laser data acquired locally at a national and international level.
The atmospheric properties around the beam path are continuously measured and recorded in a standardised manner. In addition to the conventionally collected parameters such as global radiation, ozone, air pressure, humidity, wind speed and direction, temperature (ground and air at different heights above ground level), the refractive structure function Cn2 – which describes the optical turbulence – is measured using a scintillometer and the visibility is determined by a distrometer. For a detailed description of the interaction between the atmosphere and the laser radiation, micrometeorological measurements are taken simultaneously and as close as possible to the active laser radiation.