Light weight GNSS-based passive radar for remote sensing UAV applications

Nowadays, Unmanned Aerial Vehicles (UAVs) platform are widely employed in a broad range of applications: from environmental monitoring and precise agriculture to humanitarian localization and rescue and prevention of events such as floods, fires, landslides. On the other hand, Global Navigation Satellite System Reflectometry (GNSS-R) is an emerging technique which allows to monitor Earths surface parameters. Recently, this technique has been applied to soil moisture monitoring. In this paper, a prototype of a GNSS-based passive radar, able to exploit GNSS reflected signals from ground for soil moisture monitoring applications is presented. The prototype is able to handle signals coming from three antennas: one up-looking Right-Hand (RH) Circular Polarized antenna, for the direct signal from satellite, and two down-looking antennas, one RH and the other Left-Hand (LH) Circular Polarized, to measure the signals coming after reflection from ground. It is made of low-cost hardware and it is small and lightweight in order to be mounted on board an aircraft or a UAV. It basically serves as data grabber: the collected data are stored to memory for off-line processing. The design and development of the prototype is illustrated and early results of an in-field test campaign are also presented.