
Accession Number : ADA116837
Title : Effect of Ground Terrain on Millimeter Wave Propagation.
Descriptive Note : Final technical rept. 1 Jan 8031 Aug 81,
Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE RESEARCH LAB OF ELECTRONICS
Personal Author(s) : Kong,J A ; Shin,R T
PDF Url : ADA116837
Report Date : Apr 1982
Pagination or Media Count : 28
Abstract : In the active and passive microwave remote sensing of earth terrain using radars and radiometers, the scattering effects due to medium inhomogeneities and surface roughness play a dominant role in the determination of radar backscattering crosssections and the brightness temperatures. Two theoretical models have been developed to characterize terrain media: (1) a random medium model where scattering effects can be accounted for by introducing a randomly fluctuating part in the permittivities; (2) the discrete scatterer model where discrete scatterers are imbedded in a homogeneous background medium. The earth terrain is then modelled as layers of such scattering media bounded by rough surface with air above and homogeneous halfspace below. In matching the theoretical results with experimental data collected from vegetation and snow fields, the following findings are summarized: (1) for radar observations near nadir, rough surface effects are important; (2) for snow fields the horizontal correlation length is greater than the vertical correlation length whereas for vegetation field their relative sizes depend on the types of vegetation; (3) the vertically polarized backscattering cross section is always larger than the horizontally polarized backscattering cross section for half space scattering media and may become smaller for a twolayer model; (4) for snow field displaying a diurnal change, a threelayer model including a thin top layer caused by sunlight illumination must be used; (5) the correspondence between the continuum random model and the discrete spherical model can be verified when the vertical and horizontal correlation lengths are equal. (Author)
Descriptors : *Radio transmission, *Terrain, Millimeter waves, Vertical orientation, Radiative transfer, Scattering, Backscattering, Surface roughness, Variations, Radar correlation
Subject Categories : Radiofrequency Wave Propagation
Distribution Statement : APPROVED FOR PUBLIC RELEASE