ROSETTA CIVA-P DATA CALIBRATION DESCRIPTION                                   
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Revisions                                                                     
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2015-06-26   first issue,                                                     
                                                                              
Purpose                                                                       
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This document describes the  calibration of the CIVA-P  data                  
delivered in the CIVA level 2 data set.                                       
                                                                              
Introduction                                                                  
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The calibration of CIVA-P raw images is realized in                           
the following steps (applied in that order):                                  
                                                                              
1) Non-linearity correction                                                   
                                                                              
The TH7888A detector presents a strong deviation                              
from linearity when the signal is higher than ~ 80%                           
of the saturation level. This saturation level depends                        
on the camera, on the gain setting and on the                                 
temperature of the detector. A linearity correction                           
transformation which includes the subtraction of the offest                   
has therefore been applied to level 1 CIVA images which                       
reach levels close to saturation (CIVA 1, CIVA 2, CIVA 3                      
and CIVA4). The linearity files providing the actual DN level                 
from the measured DN level (1024 floating point values)                       
are civa1scale.txt, civa2scale.txt, civa3scale.txt,                           
civa4scale.txt. The offset was evaluated as 18.4 DN, 19 DN,                   
13 DN and 20.9 DN for these four cameras.                                     
                                                                              
Cameras CIVA 5, CIVA 6 and CIVA 7 have low DN values,                         
hence the corrected values correspond to the subtraction                      
of an offset of 17.8 DN, 20.5 DN and 14.5 DN for CIVA 5,                      
CIVA 6 and CIVA 7 respectively.                                               
                                                                              
Regions of images from the CIVA 1, CIVA 2, CIVA 3 and CIVA 4                  
cameras are saturated. This situation is indicated in                         
the image file by a value of the recovered DN equal to                        
the maximum floating value of the transformation table                        
"provided in ""civaNscale.txt"" (N=1 to 4). "                                 
                                                                              
Level 3 will contain following steps:                                         
Geometrical correction                                                        
Photometric correction (Flat field)