The article of the freeze/thaw dynamic of high-latitude Earth surfaces is extremely important and informative for monitoring the carbon cycle, the climate change, and the security of infrastructures. Current methodologies mainly rely on the use of active and passive microwave sensors, while very few efforts have been devoted to the assessment of the potential of observations based on signals of opportunity. This article aims at assessing the performance of spaceborne Global Navigation Satellite System Reflectometry (GNSS-R) for high-spatial and high-temporal resolution monitoring of the Earth-surface freeze/thaw state. To this aim, reflectivity values derived from the TechDemoSat-1 (TDS-1) data have been collected and elaborated, and thus compared against the soil moisture active passive (SMAP) freeze/thaw information. Shallow subsurface soil temperature values recorded by a network of in situ stations have been considered as well. Even if an extensive and timeliness cross availability of both types of experimental data is limited by the spatial coverage and density of TDS-1 observations, the proposed analysis clearly indicates a significant seasonal cycle in the calibrated reflectivity. This opens new perspectives for the bistatic L-band high-resolution satellite monitoring of the freeze/thaw state, as well as to support the development of next-generation of GNSS-R satellite missions designed to provide enhanced performance and improved temporal and spatial coverage over high latitude areas.

中文翻译：

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通过 GNSS 反射计监测冻融状态：TechDemoSat-1 数据分析

高纬度地球表面冻结/融化动态的文章对于监测碳循环、气候变化和基础设施安全非常重要和信息丰富。当前的方法主要依赖于有源和无源微波传感器的使用，而很少致力于基于机会信号评估观测潜力。本文旨在评估星载全球导航卫星系统反射计（GNSS-R）在地球表面冻结/融化状态的高空间和高时间分辨率监测中的性能。为此，收集并详细阐述了源自 TechDemoSat-1 (TDS-1) 数据的反射率值，从而与土壤水分主动被动 (SMAP) 冻结/解冻信息进行了比较。还考虑了由原位站网络记录的浅层地下土壤温度值。即使两种类型的实验数据的广泛和及时交叉可用性受到 TDS-1 观测的空间覆盖范围和密度的限制，建议的分析也清楚地表明校准反射率存在显着的季节性周期。这为冻结/解冻状态的双基地 L 波段高分辨率卫星监测开辟了新的前景，并支持下一代 GNSS-R 卫星任务的开发，旨在提供增强的性能和改进的时间和空间覆盖在高纬度地区。即使两种类型的实验数据的广泛和及时交叉可用性受到 TDS-1 观测的空间覆盖范围和密度的限制，建议的分析也清楚地表明校准反射率存在显着的季节性周期。这为冻结/解冻状态的双基地 L 波段高分辨率卫星监测开辟了新的前景，并支持下一代 GNSS-R 卫星任务的开发，旨在提供增强的性能和改进的时间和空间覆盖在高纬度地区。即使两种类型的实验数据的广泛和及时交叉可用性受到 TDS-1 观测的空间覆盖范围和密度的限制，建议的分析也清楚地表明校准反射率存在显着的季节性周期。这为冻结/解冻状态的双基地 L 波段高分辨率卫星监测开辟了新的前景，并支持下一代 GNSS-R 卫星任务的开发，旨在提供增强的性能和改进的时间和空间覆盖在高纬度地区。