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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Monitoring Land Surface Hydrology Using Cygnss
摘要： The Cyclone Global Navigation Satellite System (CYGNSS) is a constellation of eight small satellites, each of which carries specialized GNSS receivers to record surface-reflected GNSS signals. The L-band signals recorded by CYGNSS have been shown to be sensitive to land surface hydrologic variables, including near-surface soil moisture and inundation extent. However, given certain conditions—such as vegetation cover and surface roughness, CYGNSS observations may be more or less sensitive to these variables. The pseudo-random sampling strategy used by CYGNSS presents new opportunities but also new challenges to the monitoring of land surface hydrology. This work, using South America as a case study, quantifies the ability of CYGNSS to monitor soil moisture and inundation extent for different vegetation and roughness conditions and describes how these measurements could be used to sense changes in surface hydrology over time.
关键词： CYGNSS,inundation,hydrology,soil moisture
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Impact of the Elevation Angle on Cygnss GNSS-R Reflectivity over Different Scattering Media over Land and Ocean
摘要： Earth’s surface bistatic reflectivity LHCP,CyGNSS? profiles are obtained using Global Navigation Satellite Systems Reflectometry (GNSS-R) products from NASA’s Cyclone Global Navigation Satellite Systems (CyGNSS). The focus of this study is to evaluate the influence of the GNSS satellites’ elevation angle e? on LHCP,CyGNSS?. Specific target areas with differentiated scattering media are selected to characterize these profiles as a function of the land-cover type and the wind-speed regimes for ocean-surfaces. In the former case, the main interest is to further understand the function eLHCP,CyGNSS(,...)f??? in preparation of the potential application of the so-called Tau-Omega model to GNSS-R. In the latter case, the objective is to analyze the impact of the coherent scattering component in GNSS-R observables. Preliminary results show LHCP,CyGNSS? increases ~ 3.7 dB over land and ~ 5.3 dB ocean, as e? moves from ~ [70,90]o to ~ [20,40]o.
关键词： CyGNSS,GNSS-R,coherent and incoherent scattering,elevation angle,bistatic reflectivity
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Geophysical Relationship between Cygnss GNSS-R Bistatic Reflectivity and Smap Microwave Radiometry Brightness Temperature Over Land Surfaces
摘要： This work presents an assessment on the correlation between CyGNSS-derived Global Navigation Satellite Systems Reflectometry (GNSS-R) bistatic reflectivity rl? and SMAP-derived brightness temperature BT, over land surfaces. This parametric-study is performed as a function of Soil Moisture Content (SMC), and vegetation opacity τ. Several target areas are selected to evaluate potential differentiated geophysical effects on “active” (as many transmitters as navigation satellites are in view), and passive approaches. Although microwave radiometry has potentially a better sensitivity to SMC, the spatial resolution is poor ~ 40 km. On the other hand, GNSS-R bistatic coherent radar footprint is limited by half of the first Fresnel zone which provides about ~ 150 m of spatial resolution (depending on the geometry). The synergetic combination of both techniques could provide advantages with respect to active monostatic Synthetic Aperture Radar (SAR).
关键词： vegetation opacity,CyGNSS,GNSS-R,land,microwave radiometry,SMAP,multi-static radar,Soil Moisture Content (SMC)
更新于2025-09-10 09:29:36
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A Comparison of Waveform Model Re-Tracking Methods Using Data from CYGNSS
摘要： The CYGNSS mission is a new GNSS-R ocean remote sensing constellation of eight small spacecraft. The measurements from CYGNSS allow for the first time a large, densely sampled, and calibrated GNSS-R dataset to be used for ocean surface altimetry. Re-tracking of the reflected signal correlation waveform is one of the most significant performance limiting components of ocean altimetry retrievals. This work demonstrates the use of empirical methods and physical scattering delay/delay-Doppler waveform models, fit to the measured correlation functions in a least-squares sense, to retrieve the specular reflection delay. We examine the performance of waveform modelling methods as compared to single-point re-tracking methods for the first time with a spaceborne dataset. Particular attention is given to the presence of narrow waveforms in the data set, indicative of coherent, rather than purely diffuse reflection. Re-tracking performance is quantified with statistics of the accuracy and precision and examples are presented for returns demonstrating both diffuse and coherent characteristics.
关键词： waveform modeling,CYGNSS,re-tracking,altimetry
更新于2025-09-09 09:28:46