537
A MICROWAVE RADIOMETRIC IMAGERY OP
THE TERRESTRIAL ENVIRONMENT
Teng Xuyan
Changchun Institute of Physics, Academia Sinica
P. 0. Box1035 Changchun,China
ABSTRACT
The aim of this paper is to give a brief report about the
initial advance in microwave radiometry of China. A microwave
radiometric imagery of the terrestrial environment is descr
ibed and the results of a preliminary analysis are presented.
It has been shown that the microwave radiometric imagery can
provide a lot of environmental information of the earth and
serves the purpose of the environmental assessment, on an
all weather, day and night basis.
INTRODUCTION
In the field of remote sensing techniques, a unique data in
the form of imagery yielded by the scanning microwave radio
meter, is called microwave radiometric imagery, i.e.MICRAD
imagery. Sometimes it is also called microwave thermal image.
The earliest known effort to obtain MICRAD imagery was atte
mpted by Bell Telephone Laboratories about 1954 (1 ). But the
MICRAD imagery didn't develop in depth until in the late
1960s and the early 1970s, based on varieties of waveband of
MICRAD imagery obtained from aircraft flights and surface-
based measurements. Standing in the forefront of this rese
arch field are United States ( such as the Naval Weapons
Center ) (2), West Germany (3) and Switzerland (4), et al. .
In particular, the passive microwave imaging systems on the
Nimbus satellites ( E to G ) have produced the global micro-
wave spectral imagery at the orbit height (5 ) .In China, the
study for microwave radiometric imagery of the terrestrial
environment is a newly emerging problem and it was impossible
to study this imagery until the airborne microwave radiometer
was developed in 1977.
The MICRAD imagery, which records a random thermal radiation
of the terrestrial environment in the microwave specrum, is
different from either visual imagery or radar imagery.In ge
neral, the essential characteristics of the MICRAD imagery
are as follows. The first, since a radiometer is capable of
operating in any weather condition with essentially no degra
dation in performance if a proper choice of operating frequ
ency is made, the cloud, fog, haze, smoke, precipitation at
the intensity of light rain have no or little affect on the
MICRAD imagery. The second, the MICRAD imagery is able to
carry some special informations which cannot be found out in
visual or IR imagery due to different region of electromag
netic spectrum. Substances with different surface emittance
and roughness can be discriminated. The third, informations
from not only the surface, but the subsurface of a certain
depth, can be given in the MICRAD imagery on the basis of
