DUAL-FREQUENCY INTERFEROMETRIC SAR OBSERVATIONS OF A TROPICAL RAIN-FOREST

Repeat-pass, interferometric, radar observations of tropical rain-fore st collected by the Shuttle Imaging Radar C (SIR-C) in the state of Ro ndonia, Brazil, reveal signal coherence is destroyed at C-band (5.6-cm ) in the forest, whereas L-band (24-cm) radar signals remain strongly coherent over the entire landscape. At L-band, the rms difference in i nferred topographic height between the forest and adjacent clearings i s 5 m, equivalent to the height noise. Atmospheric delays are large, h owever, forming kilometer-sized anomalies with a 1.2-cm rms one way. R adar interferometric studies of the humid tropics must therefore be co nducted at long radar wavelengths, with kilometric baselines or with t wo antennas operating simultaneously.