Cameron Harvey

GNSS-Reflectometry has been demonstrated as a new Earth Observation technique with much potential. Surrey’s GNSS-Reflectometry instrument has been used on TechDemoSat-1 and the NASA CYGNSS constellation to measure ocean winds. Reflections are also retrieved over land and ice. SSTL is continuing its work with an experiment on the 17 kg DoT-1 satellite, and leads a consortium in the ESA Scout HydroGNSS mission concept. The resolution of GNSS reflections is assumed to be around 25 km over the ocean, but when there is a flat surface, the reflections become coherent, and the resolution approaches the Fresnel zone of approximately 500 metres. These properties make GNSS-R a potential tool for assessing soil moisture and flooding under canopies. High resolution could also allow GNSS-R to map ice edges with greater accuracy than currently used radiometers. Coherent reflectometry could also increase the resolution of freeze/thaw monitoring over permafrost, and open the door for altimetry using GNSS. The processing scheme currently used on the instruments assumes that signals are incoherent, and crucial information such as carrier phase is not being collected. This project aims to investigate alternative processing schemes for collecting coherent signals from GPS and the wider bandwidth Galileo signals. Raw data collected by TechDemoSat-1 can be used to test new signal processing schemes, and there is the potential for involvement and implementation of algorithms on the DoT-1 and HydroGNSS satellite missions.