PDS_VERSION_ID        = PDS3                                                  
RECORD_TYPE           = "STREAM"                                              
                                                                              
OBJECT                = TEXT                                                  
  PUBLICATION_DATE    = 2005-12-31                                            
  NOTE                = "Description of the CALIB directory"                  
END_OBJECT            = TEXT                                                  
END                                                                           
                                                                              
        CALIB Directory Contents                                              
                                                                              
This file describes the contents of the calibration directory.  The Deep      
Impact calibration pipeline used the files in this directory to reduce raw    
data.  The files were the result of the analysis of ground-based, thermal-    
vacuum and in-flight data for the instrument.  For more information           
about these files, the analysis, and the calibration pipeline, see the        
'Deep Impact Instrument Calibration' paper included on the Deep Impact        
documentation volume, DIDOC_0001.                                             
                                                                              
The calibration data were provided as FITS image files or ASCII tables.       
The following file naming convention was used:                                
                                                                              
  CCCCC/IIIIII-YYMMDD-V-M-FFF.{FIT,TAB}                                       
  |     |      |      | | |                                                   
  |     |      |      | | Optional temperature, or place holder value         
  |     |      |      | | such as '1' or '999'                                
  |     |      |      | |                                                     
  |     |      |      | Instrument/image mode (1 through 9)                   
  |     |      |      |                                                       
  |     |      |      File version (1, 2, etc.)                               
  |     |      |                                                              
  |     |      Date from which file is valid.  This is not the date the file  
  |     |      was created.  A value of '020601' indicates the file was       
  |     |      created from thermal-vacuum data.  A value of '000101' was     
  |     |      used a place holder.  It provides no useful information        
  |     |      but was required to keep the pipeline running.                 
  |     |                                                                     
  |     Instrument designation (e.g. ITSVIS for ITS)                          
  |                                                                           
  Directory for the type of calibration file (e.g. FLAT for flat fields)      
                                                                              
Here is an example of a complete file name, FLAT/ITSVIS_020601_2_9_1.FIT:     
                                                                              
    - FLAT     Flat field                                                     
    - ITSVIS   ITS Instrument                                                 
    - 020601   Effective date of 2002-06-01; this flat was produced from      
               thermal vacuum data and can be applied to flight data          
               unless superseded by a flat field with a more recent           
               effective date for the given instrument mode                   
               to images acquired on 2005-07-01 UTC or later.                 
    - 2        Version 2 of the file for the specified effective date         
    - 9        Instrument (image) mode 9                                      
    - 1        Place holder because ITS did not have filters                  
    - .FIT     FITS file                                                      
                                                                              
Calibration files are grouped into subdirectories by type:                    
                                                                              
  ABSCALVS                                                                    
  --------                                                                    
  This subdirectory contains one table for the absolute calibration           
  constants for each instrument (image) mode.  The first column               
  specifies the constant for converting raw data numbers to units of          
  radiance, W/(M**2 SR UM).  The second column specifies the constant         
  for converting from units of radiance to units of reflectance               
  (i.e., I-over-F or the observed radiance over the input solar radiance).    
                                                                              
  ADCLUT                                                                      
  ------                                                                      
  This subdirectory contains a lookup table for the correcting for            
  uneven bit weighting caused by the analog-to-digital conversion.            
  The single table applies to all instrument modes.  As of this archive,      
  the corrections had not been derived.  Therefore, the input pixel           
  values are the same as the output values to prevent the automated           
  calibration pipeline from changing the data.                                
                                                                              
  BADPIX                                                                      
  ------                                                                      
  This subdirectory contains maps that identify bad pixels for each           
  instrument mode.  Bad pixels are set to 1.  Good pixels are set to 0.       
  Overscan columns and rows at the edges of the CCD array are set             
  flagged as good (0).  There is one horizontal row of warm pixels near       
  the top and bottom of each map.  These rows are flagged as bad (1).         
                                                                              
  BIAS                                                                        
  ----                                                                        
  This subdirectory contains a bias correction map for each instrument        
  mode.                                                                       
                                                                              
  DECOMPRS                                                                    
  --------                                                                    
  This subdirectory contains the four lossy lookup tables used to             
  decompress raw data.                                                        
                                                                              
  DRKMODEL                                                                    
  --------                                                                    
  This subdirectory contains maps for modeling the dark signal for each       
  instrument mode.                                                            
                                                                              
  FLAT                                                                        
  ----                                                                        
  This subdirectory contains flat fields for each instrument mode.            
                                                                              
  GAIN                                                                        
  ----                                                                        
  This subdirectory contains a quadrant gain correction map for each          
  instrument mode.  The values were normalized to the gain correction at      
  launch.  All pixels within a given quadrant have the same value.            
                                                                              
  PSF                                                                         
  ---                                                                         
  This subdirectory contains a dummy point-spread function used by the        
  calibration pipeline when one is not available.  It is a centered           
  delta function to prevent changes to the data.                              
                                                                              
  XTALK                                                                       
  -----                                                                       
  This subdirectory contains tables that specify the amount of gain           
  from electronic cross talk that occurs between all possible                 
  combinations of the four quadrants of the CCD.  There is one table          
  for each instrument mode.  However, after this data set was delivered       
  to PDS for the review, it was discovered that the calibration pipeline      
  used in incorrect tables, containing all zeros, for instrument modes 2      
  through 9.  The tables for these modes should have been identical to        
  the table for mode 1.  However, this omission has a negligible effect       
  (less than one percent) on the calibrated data.                             

 Name                                       Last modified      Size  Description
 Parent Directory                                                -   
 abscalvs/                                  13-Jul-2006 17:16    -   
 adclut/                                    13-Jul-2006 17:17    -   
 badpix/                                    23-Dec-2005 15:01    -   
 bias/                                      23-Dec-2005 15:10    -   
 decomprs/                                  13-Jul-2006 17:18    -   
 drkmodel/                                  30-May-2006 14:43    -   
 flat/                                      13-Jul-2006 16:07    -   
 gain/                                      23-Dec-2005 15:19    -   
 psf/                                       23-Dec-2005 19:02    -   
 xtalk/                                     24-Sep-2006 15:07    -   
 calinfo.txt                                25-Sep-2006 10:01  9.8K