Seasat over-land scatterometer data. II. Selection of extended area and land-target sites for the calibration of spaceborne scatterometers

For pt.I see ibid., vol.27, no.5, p.592-605 (1989). The post-launch performance verification for future scatterometers can use extended area land targets to calibrate antenna gain patterns and to verify and monitor deployment configurations. For the Ku-band Seasat scatterometer, a region of tropical rain forest in the Amazon basin was used as a homogeneous extended-area land target. As this region is continuously being deforested, other regions are investigated for calibrating scatterometers. The global backscatter coefficients ( sigma ⁰) are compared to classifications of natural vegetation and cultivation intensity and the variability with the time during the three-month mission is studied. The statistical variability of sigma ⁰ is compared with prior estimates resulting from the known variability of the instrument parameters and communication noise. Data from selected forested regions with relatively homogeneous sigma ⁰ and little time-dependence are presented.