561 
(1) Relative Detector Responsivity Evaluation 
Detector relative gain and offset were computed from image data histogram 
and compared with those computed from the pre-launch gain and offset values 
which were provided by NASA. Primary objectives of this analysis are to evaluate 
TM detector responsivity stability and to examine the applicability of the 
-pre-launch responsivity data to the radiometric correction. Several scenes 
in path 20 (received on July 25, 82), path 15 (Nov 2, 82) were used for the 
analysis. / 
The following results were obtained. 
(a) Stability of relative gain and offset depends upon band No. and scene. 
Band | is most variable with scene, while Bands 3 and 4 exhibit most stable 
responsivity characteristics. Relationship between the pre-launch relative 
responsivity and the image-derived post-launch relative responsivity is shown 
in Fig. 3. From the figure, it is seen that the responsivity change during 
the period is fairly small. 
(b) Linearity between the pre-launch responsivity and post-launch responsivity 
also varies with band No. Here again Bands 3 and 4 exhibited good linearity. 
Correlation rate of relative gain varied around 0.90 - 0.95 for Bands 3 and 
4 and 0.6 - 0.9 for other bands. Relative offset correlation rate varied 
0.7 - 0.9 for Bands 3 and 4 and 0.3 - 0.8 for other bands. As shown in Fig.35; 
in general, good linearity holds between the pre-launch and post-launch respon- 
sivity. 
  
  
La ve TH DETECTOR RELATIVE GAIN se La + TM DETECTOR RELATIVE GAIN == 
RECEPTIONe 828725 RECEPTION» 821182 
PATH 28 ROV 38 PATH 15 ROW = 
BAND NL = 4 BAND NO = d 
SI.OICTR = 3 ST.OTCIR = 8 
Ye LUZ KI-+ 2185 Y= 22855 X + 21124 
CORREL + 4.9914 CORRE| - 3.9839 
8 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
3 3 
GAIN 3 = 
2 = 
(B4/D8) & g 
1.88 | 
a. 38 i i 
2æ 1.58 i.82 1.84 1.84 
PRE-LAUNCH PRE-LALNCH 
2.58 *» TM DETECTOR RELATIVE OFFSET > : 2.58 =o TH DETECTOR RELATIVE OFFSET oe 
RECEPTION= 828775 RECIPT Ie 221122 
PATH 15 ROW 35 
BAND MO = 3 
ST.DICIR = 5 1 
Ye 18883 X + 41118 
CORREL = 38577 
2 3 
OFFSET 3 3 
(B3/D5) 2 2 
1.88 i x 
2.58 1.88 1.58 2.88 2. S8 
PRE-1 AUNCH PRE-LAUNCH 
(a) July 25 22 | (b) Nov. 2, . 92 
Fig. 3 Relationship between pre-launch detector responsivity and 
post-launch detector responsivity.