zx 
de 
ct 
X 
> 
Il 
   
  
  
1,2 lower and upper boundary of spectral interval (8...13 um) and 
$, = Spectral detectivity of instrument (see fig.1) 
L, (T) = radiance according to Planck's law e 
Te (H) - measured surface temperature at flight level H and 
T, (0) - apparent surface temperature (altitude: 0 m) 12.8 
Ty, = spectral transmission of an atmospheric layer The 
t (H) = Spectral transmission of the whole atmospheric layer between sen- Gu 
Sor and target Se 
T, (h) = air temperature at hight H. 
T of 
Fig.. 
Rel. Resp. 8 
$Te 
100. SW j 
$04 3 
$94 YN Lona Wve Passfilter (Germsnium) 
704 DFVLR Scanner BENDIX M^S o 
60 | ds 
50 4 z : 
40 1 3s 
304 à 2 8 
eui ® 
204 Spectral Response of Hg Cd Te 9 
104 S 
Da53c409 « WIS. 900 2 M 19 15° Wows 2 
Fig. 1: Spectral Response of the system e 
Computation of the spectral transmission was performed by using formulas of Fig. 
KONDRATYEV 1972. 
The radiant temperatures T.(0) were determined with an accuracy of 0.1 K using itera- Becau 
tive techniques. This was done for all scan angles because the mass of absorbing have 
gas varies with increasing scan angle. Fig.2 shows the calculated corrections as a A stu 
function of scan angle. follo 
X-A 
Correction of Reflection 
Natural surfaces are non-ideal black bodies. Therefore the radiometric measured tem- with 
peratures are always lower than the true surface temperatures. The difference between 
them increases with decreasing emissivity of the surface. Part of the atmospheric 
radiance is reflected into the instrument and causes the measuring of a higher ra- 
diance than that of the apparent surface temperature. This can be corrected by 
using (2). 
A A A 
2 2 2 1 
S ox Ly (Tg (0)dA sj $5 € L, (T)dA + J $4 (1-e ) 7 G di (2) 
A M M 
with £j = Spectral emissivity of the surface 
Gy = radiance of the atmosphere at wave length à A 
T - true surface temperature shall 
forme 
The computation was done with an average value of e - 0.972 for water (BUETTNER coeff 
136 
EY à —