Tropospheric scintillation spectra and transversal wind speed for satellite links at very low elevation angles

Simultaneous measurements of tropospheric scintillation on three different satellite beacons at Ka-band are analyzed. The links have elevation angles of 3.3, 21.8 and 22 degrees. Corner frequency of scintillation is used to calculate the transverse wind speed on each of the links and this is compared with the predictions from a numerical weather model. Results for the two links with higher elevation angle show good agreement with each other as well as with the model data. For the link with elevation angle of 3.3 degrees good match with model data is achieved only when theory applicable for outer scale of turbulence smaller than the Fresnel zone is used. Significant changes in scintillation corner frequency during rain events are also observed for the 3.3 degree link. The results indicate that scintillation at very low elevation angles can be composed of different phenomena, leading among others, to different frequency dependence.