Azimuth Antenna Maximum Likelihood Estimation by Persistent Point Scatterers in SAR Images

This paper addresses the problem of estimating the azimuth antenna pattern by using a set of persistent point scatterers (PPS) retrieved from a stack of interferometric synthetic aperture radar images. This is achieved by means of a maximum likelihood estimation. PPS emerge as a restricted subset of the well known persistent scatterers, for which many applications have been described in the literature. PPS have a more stringent property since they explicitly require an impulsive trend feature; a good degree of isolation from the neighboring targets is further necessary to estimate the antenna pattern by means of digital spotlight focusing. A statistical model for PPS is provided and experimentally validated; the sufficient number of PPSs necessary to get a given accuracy for the azimuth antenna estimation is also suggested. Results using both simulated and real X-band Cosmo Skymed data are eventually illustrated.