First Results of the TOPSAR C-Band/L-Band Interferometer: Calibration and Differential Penetration

The NASA/JPL TOPSAR instrument recently was extended from a single- wavelength C-band (5.6 cm-lambda) dual aperture synthetic aperture radar interferometer to include a second wavelength at L-band (24 cm). Adding the second wavelength invites comparison of wavelength-diverse effects in topographic mapping of surfaces, with the principal goal of understanding the penetration of the radar signals in vegetation canopies, and determining the inferred topographic height. A first analysis of these data was conducted at two sites. Elkhorn Slough near Monterey, California presented flat, vegetation free terrain required for calibrating the radar interferometric parameters. A second site stretching from San Jose to Santa Cruz, CA, which is heavily vegetated, provided the first test case for wavelength diverse penetration studies. Preliminary results show that: (a) the interferometer calibration determined at Elkhorn Slough is extendable to Laurel Quad and gives confidence in the C- and L-band height measurements; and (b) Clear differences are observed between the C- and L-band heights associated with vegetation, with C-band-derived topographic heights generally higher than those from L-band. The noise level in the L-band interferometer is presently the limiting factor in penetration studies.