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

The slope directory contains the VICAR-format "slope files" derived during 
ground calibration, and used by the calibration software as flatfields. 
These files have units of picoamp-ms/DN, but are normalized to the average 
of the inner 400x400 pixels before use.

Database files are also included which specify the slope files as functions
of filter combination and temperature. There are three different database
files: slope_db_1.tab is the original, and contains some outdated naming 
conventions; slope_db_2.tab is considered best, and is the one currently 
used in CISSCAL; slope_db_3.tab is the newest, but contains some files that 
have been found to introduce excess noise into the images.   

The old/ directory contains obsolete slope files. Specifically:

  slope.slp130.old (replaced by a window median filtered version)
  slope.slp201.old (old version had invalid VICAR format)

In the fall of '03, the NAC slope files were replaced with new versions 
corrected for anti-blooming pixel pairs (since the originals were created
from images that had anti-blooming mode turned on). The changes to these 
files are documented in the document pair_removal.txt, also included in this 
directory.