First-Time Soil Moisture Retrieval Using Single-Frequency Dual-Polarization GNSS-R with Airborne GLORI Data

摘要: Abstract-PolarizationwasonceoverlookedinGNSS-Rstudies.However,inrecentyears,it has garnered increasing interest.Thispaper explores dualpolarizationfor single-frequency data fromthe airborne GLORI experiment.Building on theoretical analysis,wehaveappliedseveralretrievalalgorithmsfor soilmoistureestimation.Initially, only the surface reflectivity of LR and RRpolarizations was examined.As additional surface parameters,suchassurfaceroughnessandvegetation,wereincorporatedintothe algorithm, the retrieval accuracy, as indicated by RMSE,improved from around 0.07 to 0.03.The accuracyretrieved by RRpolarization appearsslightlybetter than that of LRpolarization.However,when both dual polarizations were considered,theretrievalaccuracymatchedthatofusingonlyonepolarization.Whensurfaceroughness,LAI,andincidenceangleare takenintoaccount, the retrieval accuracy, as indicated by RMSE,is 0.0344.Thissuggeststhatdualpolarizationholdsgreatpotentialforsoilmoisture estimation.GLORI data is the first publicly availabledualpolarizationGNSS-Rdatathatincludesbothcoherentandnoncoherent scattering. This paper also discusses the noncoherentscattering properties of LR andRRpolarizations.In the realm ofcoherent scattering,it is observed that thescatteringproperties atLR polarizationexceed thoseatRRpolarization.However,thistrendreversesfornoncoherentscattering,whereinthescatteringproperties atLRpolarization are diminished compared to those atRR polarization for corresponding land surface types.Theanalysis of dual polarizations data will benefitfuture data miningformoreaccuratesoilmoistureretrievalandthedesignoffuturepolarizationGNSS-Rpayloads.Whiletheretrievalaccuracywiththe consideration ofnoncoherent scattering properties indicatesthatnot only coherent scattering but also noncoherent scatteringshould be included in future GNSS-R data sets, they arecomparableforfuturesoil moistureretrievalalgorithms.Index Terms—polarization,coherent scattering,non-coherentscattering,GNSS-R,soil moisture,surface roughness,vegetation.