These payload system requirements still require more design efforts to be performed for a space SAR system of NESZ= -18 dB. This system NESZ has been temporarily selected by considering most terrain distributed targets data in [4] (i.e., the backscattering data for major land cover types shown in Table IV) by excluding the road surfaces which will
be too difficult to detect the ingredients with a low cost space
SAR system defined like ours. However, they, similar to water
surfaces, should be able to be easily discriminated from the
other land cover types in the scene. Note that the data shown
are the mean values (between the incidence angles of 20 ~ 60
degrees) and more data statistics for the land cover types [4] in
terms of HH/HV/VV polarization are available for further
analysis for a dual polarization system (i.e., HH + HV), which
may require more capability on the system radiometric
sensitivity.