Subjects: Geosciences >> Geochemistry submitted time 2019-04-10
Abstract： " In the past two decades, Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a new remote sensing technique for soil moisture monitoring. Some experiments showed that the antenna of V polarization is more favorable to receive the reflected signals, and the interference pattern technique (IPT) was used for soil moisture and other geophysical parameters retrieval. Meanwhile, the lower satellite elevation angles are most impacted by the multipath. However, electromagnetic theoretical properties are not clear for GNSS-R soil moisture retrieval. In this paper, the Advanced Integral Equation Model (AIEM) is employed using the wave synthesis technique to simulate different polarimetric scattering at the specular directions. Results show when the incidence angles are larger than 70º, scattering at RR polarization (The transmitted signal is Right Hand Circular Polarization (RHCP), while the received one is also RHCP) is larger than that one at LR polarization (The transmitted signal is RHCP, while the received one is Left Hand Circular Polarization (LHCP)), while scattering at LR polarization is larger than that at RR polarization for the other incident angles（1º~70º）. There is an apparent dip for VV and VR scattering due to the Brewster angle, which will result in the notch in the final receiving power and this phenomenon can be used for soil moisture retrieval or vegetation corrections. The volumetric soil moisture (vms) effects on their scattering are also presented. The larger soil moisture will result in lower scattering at RR polarization, and this is very different from the scattering of the other polarizations. It is interesting to note that the surface correlation function only affects the amplitudes of the scattering coefficients at much less level, but it has no effects on the angular trends of RR and LR polarizations.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Geodestics submitted time 2019-04-10
Abstract： " GNSS-R is a new promising remote sensing technique, which utilizes the reflected signals of GNSS constellation to remotely sense the ocean or land surface. At present, most of the existing research are based on the experimental observations, few theoretical studies have been carried out. This paper has developed a fully polarization GNSS-R delay Doppler map for land geophysical parameters study. This theoretical model was based on the ocean surface GPS scattering model, after the modifications, it has been used for the land surface. As for the calculations of land geophysical parameters (bare soil and vegetation), random surface scattering model and the first order radiation transfer equation model were used. Effects of bare soil and vegetation parameters on the delay Doppler maps were simulated. In order to use the polarization information for backward inversion, our developed theoretical model has the ability of fully polarizations calculations, i.e. RR, LR, HR and VR pol. This theoretical model is a mechanism tool for the data explanation of space borne mission, experimental campaign design, data simulations and the backward inversion algorithm development. "
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Geodestics submitted time 2019-04-10
Abstract： " GNSS-R has been emerged as a new and promising remote sensing technique in recent years. Due the strong penitration properties of L band microwave length, it is suitable to monitor soil moisture using this technique. According to different remote sening platforms, progresses of soil moisture monitoring using GNSS-R technique with ground-based, tower-based, airborne and space borne platforms are presented in this paper, while a detail review of GNSS-R joint with microwave radiometer is also given in this paper. "
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Geodestics submitted time 2019-04-04
Abstract： " In order to extend the applications GNSS-R/IR（GNSS-Reflectometry /Interferometric Reflectometry ) remote sensing technique to soil freeze/thaw process detection, soil(frozen/thawn) mixing permittivity models are employed to calculate the soil permittivity. Bistatic full-polarizationcoherentscattering model and random roughness surface scattering model are used to calculate the coherent and non-coherent scattering, which result in the variations of GPS multipath observables and DDM（Delay Doppler Map） waveforms, respectively. When the soil freeze/thaw process occurs, theoretical simulations indicate that soil freeze/thaw process induce the abrupt permittivity changes and affect the obvious variations of GNSS-R/IR signals.In this way, theoreticalfundamentals for soil freeze/thaw process detections are presented.
Peer Review Status:Awaiting Review
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