Differential spectral attenuation measurements at microwaves in a LEO-LEO satellites radio occultation geometry: a novel approach for limiting scintillation effects in tropospheric water vapor measurements

The DSA (Differential Spectral Attenuation) approach, presented in a companion paper in this conference's proceedings, has the potential to provide the total content of water vapor (IWV, Integrated Water Vapor) along the propagation path between two Low Earth Orbiting (LEO) satellites. The interest towards the DSA, based on the ratio of simultaneous measurements of the total attenuation at two relatively close frequencies in the K-Ku bands, was moved by the need for limiting the effects of tropopheric scintillation and by the fact that DSA measurements are highly correlated to the IWV along the LEO-LEO link. However, the impact of tropospheric scintillation in a LEO-LEO radio occultation geometry using frequencies above 10 GHz still has to be thoroughly investigated. In this paper we focus on the analysis of such effects, taking into account the fact that the formulations presented in the literature have to be modified in order to fit the specific problem under consideration. Specifically, an expression is derived for the variances of the amplitude and phase fluctuations of the wave, their spectrum and the correlation between fluctuations at different frequencies. In particular, the latter is extremely useful to evaluate the potential of the DSA approach through simulations whose results are reported in the last part of the paper.