X-BAND SAR AND SCATTEROMETER DATA INVERSION BASED ON GEOMETRICAL-OPTICS MODEL AND KALMAN FILTER APPROACH

This paper describes the activity performed in the framework of the 19 90 AVIOSAR 580 SAR and scatterometer Italian campaign over the Matera test site. The experiment has been carried out to ascertain the reliab ility of surface scattering models in order to tackle with the data in version problem. To achieve this goal, physical and geometrical featur es of 38 homogeneous bare soil fields are considered as a result of gr ound truth data collection. X band - VV polarization sigma(o) values f rom the HUTSCAT scatterometer at 45-degrees and from the CCRS airborne SAR sensor at the incidence angles between 50-degrees and 62-degrees are compared with those obtained from modeled data. The SAR data have been calibrated using both corner reflectors and extended natural targ ets. The backscatter variability due to surface roughness has been ana lyzed. Due to the characteristics of the analyzed data set, i.e., high incidence angle and surfaces with large root mean square slope profil e m, the SPM and PO models were not suitable for many fields in the sc ene; on the other hand, a good agreement between theoretical predictio ns and experimental data is found when the Geometrical Optics (GO) mod el is used. A threshold value for m as function of the incidence angle is found and a physical interpretation of this behavior is also propo sed. After the assessment of the GO model results, the problem of retr ieving the real part of the soil relative dielectric constant Re(epsil on(tau)) and m value is addressed as well, considering the extended Ka lman filter approach. The comparison between the obtained values and t he experimental data shows the reliability of the inversion approach, thus encouraging the use of more sophisticated backscattering models.