The ESA-ANISAP study: estimate of tropospheric scintillation along a LEO-LEO link through high resolution radiosonde data

This work describes the procedure developed in the framework of the ESA-ANISAP study to obtain, for a given atmospheric profile, an estimate of scintillation effects in a LEO-LEO link. In this procedure, the refractive-index structure constant profiles describing the intensity of turbulence, are derived by applying the vertical gradient approach to high resolution radiosonde data. The fact that turbulence in the free atmosphere is confined to vertically thin layers is accounted for by identifying the turbulent layers through the analysis of the Richardson number profiles. Then, the derived structure constant profiles are inserted into a parametric scintillation model to create a scintillation disturbance estimate consistent with the considered atmospheric profile. In the parametric model, the troposphere is described as a spherically symmetric turbulent medium. Rytov‟s first iteration solution for weak fluctuations is used to derive an expression for two quantities of interest to evaluate the performances of the Normalized Differential Spectral Attenuation for the estimate of the total content of water vapour along the propagation path between two LEO satellite, namely: the variance of amplitude fluctuations of the wave and the correlation between the fluctuations at different frequencies. The influence on these quantities of some turbulence characteristics which are not known with confidence, like the outer scale length and the behaviour of the spectrum in the input range, is also investigated.