Improved modelling of propagation and backscattering of millimetre waves in the melting layer

The frequency bands, presently used by space telecommunications systems, are saturated, hence the need for using higher frequencies (EHF). However, for millimetre waves, the atmospheric propagation of electromagnetic waves is more perturbed than at lower bands. Precipitation, clouds and gases are responsible for that. The contribution of the melting layer, in terms of attenuation, is also no more negligible. This atmospheric layer, where ice particles melt into raindrops, still cause problems of characterisation and modelling. Furthermore, the melting layer can be responsible for the phenomenon of frost on the aircraft. Fortunately, this band can be easily detected because of its peak of reflectivity in the millimetre domain. It is for this reason that the melting layer is detected as a ´bright band´ by radar. This study deals with the characterisation and modelling of the melting layer in order to better predict its effects on the performance of spatial telecommunications systems in the EHF domain, and also to assess radar performance for melting layer detection at a distance. Some models already exist and are presented, but they are not entirely satisfactory. It is also for this reason that a new calculation for scattering by a particle is introduced. The results of simulations and a comparison with experimental data are presented.