Precision Bounds in GNSS-R Ocean Altimetry

Global navigation satellite systems (GNSS) signals offer a promising opportunity to perform mesoscale altimetry with worldwide coverage using small satellites. However, unlike the signals used in classical altimeters, the GNSS signals have smaller bandwidth and lower transmitted power. This paper analyzes the achievable height precision of the Global Navigation Satellite System Reflectometry (GNSS-R) altimeters based on the Cramér-Rao bound for time-delay estimation. Precision bounds for the composite signals GPS L1 and L5 and Galileo E1, E5, and E6 in a spaceborne mission scenario are assessed, and the optimum receiver bandwidths which minimize them are obtained.