polarization characteristics may also be used. The motivation and 
rationale for the use of multispectral scanners have been summarized 
previously [3, 4] and includes higher information capacity, sensing 
outside the spectral region of photographic film sensitivity, and 
electronic recording. The sensed signal is the sum of two components, 
a reflected and an emitted signal. Radiation from the sun, sky, and/or 
laser source falls on the terrestrial scene. The objects' optical 
properties due to their chemical or biological composition and geometrical 
arrangement combined with the spectral and spatial distribution of the 
source (as modified by the atmosphere) determine the amount and spectral 
character of the radiation reflected (or scattered) in a specified 
direction. The reflected radiation from the object is then attenuated 
by the atmosphere before reaching the sensor along with a contribution 
scattered from the atmosphere. Objects with temperature greater than 
absolute zero emit electromagnetic radiation with the objects' optical 
and geometric properties determining the amount of radiation emitted in 
a specific direction. This radiation from the object is also attenuated 
by the atmosphere which adds a component emitted from the atmosphere. 
The basic equation for the total spectral radiance, Lys at the multi- 
spectral scanner is: 
S 
Oo) + 1{bb,2A,T)e (A) ]+ L 
= T(A) | p^(43 E 
X sine, df 
1 pA 
e 
2 
path spectral radiance from atmospheric emission and 
scattering along path between sensor and object; 
= 0 i 
L OU. 9 > h) is albedo dependent 
angles which define sensor-object path 
directional distribution of emissivity for object; 
(A) = (À, b.11.9 925 LT are perpendicular and 
parallel polarization components 
blackbody spectral radiance given by Planck's distribution 
spectral irradiance from direction 9450» on object with 
integral taken over illuminating hemisphere; 
E, = EQ, [Il 0.0) 
bidirectional spectral reflectance for object; 
pe (à) = (Q, Lb 11,9,:95:0,,032; for semi-transparent 
material radiation scattered from within adds to p^. 
atmospheric spectral transmittance as a function of 
path to sensor at height h; T70()) = 1.,0,,0,,h)