Accession Number : ADA116837

Title :   Effect of Ground Terrain on Millimeter Wave Propagation.

Descriptive Note : Final technical rept. 1 Jan 80-31 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 back-scattering cross-sections 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 half-space 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 two-layer model; (4) for snow field displaying a diurnal change, a three-layer model including a thin top layer caused by sun-light 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