PDS_VERSION_ID         = PDS3
RECORD_TYPE            = STREAM
OBJECT                 = TEXT
  PUBLICATION_DATE     = 2004-12-07
  INTERCHANGE_FORMAT   = ASCII
  NOTE                 = "Description of distortion directory contents."
END_OBJECT             = TEXT
END
  
Distortion directory:
---------------------

The file nac_focallengths.tab is a sorted list of NAC focal lengths. Average 
focal length with no distortion parameter is 2003.181+/-.27 mm. Maximum 
offset error here would be 0.22 pixels at the corners; little point in doing 
separate filters, so this file is not currently used by CISSCAL. 

The file wac_focallengths.tab is a sorted list of WAC focal lengths using the 
standard distortion coefficient of -6.2x10-5.  The average is 200.956 +/- .15 
mm. Use of an average would introduce a maximum registration error of 0.94 
pixels at the corners (radius-724 pixels). (0.26 mm/ 200.956mm)*724.

Columns for both files are: filter 1, filter 2, focal length (mm), error (mm).