Effect of Salinity on the Dielectric Properties of Geological Materials: Implication for Soil Moisture Detection by Means of Radar Remote Sensing

• Published in: IEEE transactions on geoscience and remote sensing Vol. 46; no. 6; pp. 1674 - 1688
• Main Authors: Lasne, Y., Paillou, P., Freeman, A., Farr, T., McDonald, K.C., Ruffie, G., Malezieux, J.-M., Chapman, B., Demontoux, F.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.06.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical models; Applied geophysics; Backscatter; Dielectric losses; Dielectric materials; Dielectric mixing model; Dielectric properties; Earth sciences; Earth, ocean, space; evaporites; Exact sciences and technology; Geology; integral equation model (IEM); Internal geophysics; Moisture content; Permittivity; polarimetry; Polarization; radar backscattering; Radar detection; Radar remote sensing; Salinity; Soil moisture; Studies; synthetic aperture radar (SAR); experimental studies; microwaves; mixing; arid environment; networks; dielectric constant; frequency; exploitation; Earth; Mars; integral equation model (IEM); conductivity; Dielectric mixing model; water content; models; salinity; polarimetry; soil moisture; dielectric properties; radar backscattering; remote sensing; backscattering; evaporites; interplanetary comparison; sand; synthetic aperture radar (SAR); radar methods; sodium chloride
• ISSN: 0196-2892; 1558-0644
• DOI: 10.1109/TGRS.2008.916220

We consider the exploitation of dielectric properties of saline deposits for the detection and mapping of moisture in arid regions on both Earth and Mars. We present simulated and experimental study in order to assess the effect of salinity on the complex permittivity of geological materials and, therefore, on the radar backscattering coefficient in the [1-7 GHz] frequency range. Laboratory measurements are performed on sand/sodium chloride aqueous mixtures using a vectorial network analyzer coupled to an open-ended coaxial dielectric probe. We aim at calibrating and validating semiempirical dielectric mixing models. In particular, we evaluated the dependence of the real and imaginary parts of complex permittivity on the microwave frequency, water content, and salinity. Our results confirm that if the real part is mainly affected by the moisture content, the imaginary part is more sensitive to salinity. In addition to the classic formulas of mixing models, the ionic-conductivity losses, which are due to mobile ions in the saline solution, are taken into account in order to better assess the effect of salinity on the dielectric properties of mixtures. Dielectric mixing models are then used as input parameters for the simulation of the radar backscattering coefficients by means of an analytical model: the integral equation model. Simulation results show that salinity should have a significant impact on the radar backscattering recorded in synthetic aperture radar data in terms of the magnitude of the backscattering coefficient. Moreover, our results suggest that VV polarization provides a greater sensitivity to salinity than HH polarization.