Helicopter-borne scatterometer measurements at L, C, and X bands during the 1994 BOREAS field campaigns

During the late summer and early fall of 1994, radar backscatter measurements were taken using a three-band helicopter-borne radar as part of the BOREAS experiment. The radar is an FM-CW scatterometer that operates at L (1.5 GHz), C (5.5 GHz) and X (10 GHz) bands with all four linear polarizations and incidence angles ranging from 5° to 40°. Ground-based canopy architecture measurements were also taken at the jack pine sites. In this paper, the authors present the results of the radar measurements taken during the 1994 field campaigns. Plots of the backscattering coefficient as a function of incidence angle for the L-band and C-band data are presented. At L-band, the backscattering decreases by 15 dB from an incidence angle of 5° to 20°. The decrease over this range of angles at C-band is 3 dB. These results suggest that the low angle returns at L-band are dominated by scattering from the ground while the low angle returns at C-band are a combination of scattering from the ground and the canopy. Relative backscattered power versus range curves for L-band and C-band at incidence angles of 5° and 30° are also presented to support this conclusion