Simulation Study of Cygnss Observability of Dynamic Inundation Events

The Cyclone Global Navigation Satellite System (CYGNSS) has recently shown exciting potential for GNSS reflectometry (GNSS-R) to resolve small-scale and dynamic hydrological features over land (such as rivers, lakes, wetlands, and urban flooding), even when obstructed by dense vegetation. Since CYGNSS is a small satellite constellation, sub-daily measurement frequencies provide a unique opportunity to observe short timescale changes. However, since CYGNSS observations occur in sparse, quasi-random tracks, it is more difficult to understand the true observability of events as compared to imaging instruments. Changes in SNR that would indicate a dynamic change in the scene are confounded by inherent variability due to other sources, including vegetation, geometry changes, instrument gain calibration, and surface roughness due to wind. While the literature does detail the use of CYGNSS measurements to map surface water changes, the lack of valid ground data makes it difficult to quantify the true accuracy. Here, we present results from a simulation study currently underway that utilizes a GNSS-R coherent scattering model to understand the observability and accuracy of CYGNSS measurements of dynamic changes in inland water bodies. The goal is to quantify the sensitivity and resolution of observations of dynamic spatial and temporal variations of inland water bodies.