1. THE RADIATORS 
Electromagnetic radiation is generated whenever char- 
ged particles are accelerated. The objective of remote 
sensing is to detect and record energy in a selected por- 
tion of the electromagnetic spectrum. The electromagne- 
tic spectrum of interest to remote sensing is shown in 
Figure 1. together with the atmospheric properties that 
most strongly affect remote sensing. 
According to the two types of remote sensing systems, 
the active systems utilize artificial energy sources, the 
passive systems the natural level of radiation emanating 
from a given scene. | 
The level of energy reflected or emitted from objects 
normally varies with wavelenght through the elektromagne- 
tic spectrum. The signature of an object on an image is 
governed by the amout of energy transmitted to sensor wit- 
hin the wavelength range in which that sensor images. The- 
refore, a unique tonal signature of an object can often 
be identified if the sensed energy is brokan down into 
| chosen wavelength bands. Discrimination capability can 
generally be improved. However, this multispectral ima- 
ging technique appears to be relatively simple, compli- 
cations arise due to uncertainties of variations related 
to the following factors: /a/ spectral characteristics 
of the source of illumination, /b/ illumination angles 
of incidence, /o/ effects of the atmosphere, /à/ reflec- 
tance and emittance characteristics of the objects, 
/e/ altitude of the sensor systems, /f/ data reduction, 
and /g/ data interpretation techniques. 
A specification of these factors and uncertainties 
associated with their distribution, measurement, and re- 
lative importance is necessary in order to identify and 
measure the object-to-back-ground contrast ratios in ma- 
ny remote sensing operations. 
Intensive research is being conduoted in the fields 
of /1/ acceleration of charged partioles, /2/ the trans- 
fer of energy, /3/ better understanding of the nature