Efficiency of end effect probes for in-situ permittivity measurements in the 0.5–6GHz frequency range and their application for organic soil horizons study

tThe remote signatures measured at microwave frequency above land surfaces are strongly dependent onthe permittivity of the soil, which is linked to its moisture content. Thus, soil permittivity is a key param-eter when algorithms are developed for the retrieval of hydrologic parameters from remote sensing data.Soil permittivity measurements are generally carried out in the laboratory because in-situ measurementsare more difficult to obtain. The study presents the development of two probes (N and SMA probes) forin situ soil permittivity measurements (i.e. measurements of dielectric properties). They are based on theend effect phenomenon of a coaxial waveguide and so are called end effect probes in this paper. Resultsobtained on well-known materials (water and polytetrafluoroethene) are compared with correspond-ing data obtained by laboratory approaches (Von Hippel’s method and resonant cavity) and show goodagreement from 0.5 GHz up to ∼3.5 GHz and 6 GHz for N and SMA probes respectively. Then measure-ments made on concrete and mineral soil are reported to underline the efficiency of end effect probesfor in-situ dielectric measurements. Finally, through work undertaken in the framework of the EuropeanSpace Agency’s SMOSHiLat project, we demonstrate the applicability of the two probes for measurementsperformed within these frequency ranges in complex material such as organic soil horizons.