Radar polarimetry has finally reached its golden age with the recent launch of fully polarimetric satellite SARs; ALOS PASAR and TerraSAR with experimental polari- metric mode, and more recently RADARSAT-2 with oper- ational polarimetric modes at various incidence angles (be-

polarized SAR systems. It is shown that the circular hybrid transmitting architecture limits the dynamic range of HH, HV, and VV . Conventional polarimetric linear polarized systems permit separate routage of the cross-polarized HV and VH voltage to the same receiver, and this offer the possibility of the improvement of the cross-polarized return of 6 to 9 dB in term of signal to noise ratio (S/N). The information provided by compact-hybrid SAR is compared to the one available with fully polarimetric SAR. Operating with only one transmitting antenna polarization, Hybrid only uses half of the space of polarization information provided by fully polarimetric SAR, which exploit the diversity of both the transmitting and receiving polarizations for optimum target characterization. This limits the efficiency of Hybrid in the exploitation of both wave and target Poincaré sphere parameters. These parameters generated from fully polarimetric SARs permit a complete characterization of target scattering type and heterogeneity for the optimum extraction of target geophysical parameters. The cross-polarization HV backscattering cannot be accurately reconstructed from the Compact dualpolarization, and dual linear polarized mode (HH-HV or VV-VH) or single polarization mode HV should be measured to meet the calibration requirement of 0.5 dB for certain applications, such as biomass measurement. At severe Faraday rotation conditions, conventional RR-RL (Right-Right, Right-Left) circular polarized SAR and Hybrid RH-RV, whose radiometric RR and RL information is not affected by Faraday rotation, are recommended.