Remote Sensing with GPS Signals on Low Earth Orbit Satellite

GNSS reflectometry (GNSS-R) is a remote sensing technique. It is based on a multi-static radar structure that uses the navigation systems' satellites as transmitters, the Earth's surface as target and a receiver that can be ground located, airborne or on board a space vehicle. The reflected signal that reaches the receiver is very weak, and its characteristics depend on several factors, such as the system geometry and the state and nature of the reflecting surface. This paper analyzes the case of a receiver located in a Low Earth Orbit (LEO) satellite intended to process GPS signals reflected over the ocean surface. Scattering models for the reflected signals are used to calculate the mean power level that is expected in different geometry and sea-state scenarios. With these results, the minimum requirements for the receiver antenna are determined in order to succesfully process the reflected signals, taking a first step on the way to design a complete GNSS-R receiver.