Antenna and propagation aspects of a future GNSS-reflectometry mission

Global Navigation Satellite System Reflectometry (GNSS-R) is a passive sensing method to measure properties of the Earth's surface, of oceans, or of the atmosphere by analyzing reflected navigation signals from GNSS satellites such as GPS (Global Positioning System). The reflected signals can be measured with ground based, air borne, or space based sensors, and the applications reach from altimetry, ocean wind retrieval, soil moisture to vegetation growth analysis. The principle of GNSS-R was presented a few decades ago. Meanwhile, GNSS-R is already used in ground based GNSS sites, performance analyses/demonstrations for in-orbit measurements are carried out, and orbit missions are ongoing. The present study introduces the concept and some of its variations. It describes initial and ongoing research, and it presents propagation aspects of a future CubeSat mission to measure the height of oceans and ice areas and study the sea ice extend. Finally, the design of a L-band patch antenna array is presented that will be used to detect both the direct and the reflected GNSS signals.