No abstract

Because the microwave dielectric constant of dry vegetative matter is much smaller (by an order of magnitude or more) than the dielectric constant of water, and because a vegetation canopy is usually composed of more than 99% air by volume, it is proposed that the canopy can be modeled as a water cloud whose droplets are held in place by the vegetative matter. Such a model was developed assuming that the canopy “cloud” contains identical water droplets randomly distributed within the canopy. By integrating the scattering and attenuation cross‐section contributions of N droplets per unit volume over the signal pathlength through the canopy, an expression was derived for the backscattering coefficient as a function of three target parameters: volumetric moisture content of the soil, volumetric water content of the vegetation, and plant height. Regression analysis of the model predictions against scattering data acquired over a period of four months at several angles of incidence (0°–70°) and frequencies (8–18 GHz) for HH and VV polarizations yields correlation coefficients that range from .7 to .99 depending on frequency, polarization, and crop type. The corresponding standard errors of estimate range from 1.1 to 2.6 dB.

No abstract

Tlze Actii%c Microwaiv Instruinerit {AMI) isU conihinatiori of a C-band (5.3 GHz), VV polarization, Synthetic Apcwurc Radar {SAR), arid a Wind Scatterometer. It is being carried on the first European Remote Sensing Satellite ERS-1. I t s primary geophysical data products are ocean surface wind speed and direction, ocean w m v length and direction, and high resolution radar-mapping of land, ocean, ice, and coastal zones.The ERS-1 payload also includcs a radar altinieter. an alongtrack scanning infrared radiometer, a microwa1.e sounder, a precision range arid range ratc merrsuririg equipnient, arid a laser retro-rcflector. ERS-l will he in a polar orbit for glohal mapping. Prelaunch testing has shown that the qualiw of the AMI datrr products are meeting the mission objectives with margin.