Decorrelation of GNSS-R Reflected Signals: Analytical Modeling

We propose an analytical solution of the scattering for the evaluation of the decorrelation time of reflected signals of opportunity. We consider spaceborne receivers and an approximated solution of the covariance of the scattered field under the Kirchhoff approximation. The case of an infinite illuminated surface showing gentle undulations is studied. It is discussed how the near-specular scattering, collected over land targets by a receiver from space, decorrelates as a function of the receiver movement and of the statistical parameters describing the illuminated surface. The study gives information of interest for the design of future bistatic missions, especially for GNSS reflectometry. The interpretation of data from space, which typically shows strong fluctuations, can also be supported.