A Review of GNSS-R/SoOP-R for Essential Hydrological Climate Variables Detection

Global navigation satellite system-reflectometry (GNSS-R) is a kind of promising remote sensing technique, which utilizes the reflected signals of GNSS for geophysical parameters detection. Its applications on ocean surface are earlier and more mature. However, in recent years, with the development of spaceborne satellite exploration programs such as TechDemoSat-1, cyclone GNSS (CYGNSS) and Fengyun 3E,its advantages and potential in land remote sensing research have gradually emerged. The research work of the existing mechanism model is summarized. Meanwhile, this paper reviews the research status of spaceborne GNSS-R and other signal of opportunity reflection remote sensing (SoOP-R). GNSS-R's applications on soil moisture, vegetation, soil freeze-thaw monitoring are focused on, while the research status of the latest SoOP-R technology in root zone soil moisture and snow water equivalent is also summarized. In this way, we hope to promote the development of this technology in the detection of major climatic and meteorological parameters for the hydrological cycle to a certain extent.