Wavelength (pm) 
Figure 3. Transmission of the different channels of the prototype 
The calibration curve for the broadband channel is given in Figure 4. C 0 and S are the regression 
coefficients of the least square fitted line and R is the correlation coefficient. 
- 6 - 4 - 2 0 2 4 6 
w (jiW) 
Figure 4. Calibration of the broadband channel of the prototype 
The experimental sensitivity in this channel is S= 630 ct/pW. The responsivity of the detector given by the 
constructor is 120 V/W; this implies a theoretical sensitivity of the prototype of 1200 ct/pW. Thus, the ratio of 
the experimental to theoretical sensitivities is about 0.5. The experimentally derived values of the narrowband 
channels are 750, 640, and 430 ct/pW, respectively for the 8.7, 10.5 and 11.5 pm filters. 
4.2.2. Noise. The theoretical noise of the prototype was estimated for two spectral domains of interest at 
various temperatures. The NEDT is given by 
NEDT.-^. (5) 
— . A . Q 
dl 
The theoretical NEDT computed for 1-pm wide wavelength bands is shown in Table 3. The results show that 
while the NEDT in the 8-14 pm window is satisfactory, the noise in the 3.7 pm window remains critical with 
regards to the required characteristics given in Section 2. This is due to the low spectral energy contained in 
this particular region of the spectrum. 
813