PDS_VERSION_ID         = PDS3
RECORD_TYPE            = STREAM
OBJECT                 = TEXT
  PUBLICATION_DATE     = 2018-08-06
  INTERCHANGE_FORMAT   = ASCII
  NOTE                 = "Description of darkcurrent directory contents."
END_OBJECT             = TEXT
END

Darkcurrent directory:
----------------------

The files nac_derived_dark_parameters* and wac_derived_dark_parameters* 
contain parameters for the CISSCAL dark interpolation model, in standard
binary XDR format. Values represent electron emission from each pixel as
measured in eight exposure bins spanning the range of commandable camera 
exposure times. The files nac_dark_parameters* and wac_dark_parameters* 
are the same, but have had various artifacts removed, including saturated 
pixels, low-frequency horizontal ringing, and residual hot pixel streaks. 
They have also been median-filtered. These are the files used by the dark 
subtraction algorithm in CISSCAL 3.7 and subsequent versions.

In addition, the files NAC_hotpix* and WAC_hotpix* contain lists of 
erroneously bright "hot pixels" measured at various times over the course 
of the mission. CISSCAL selects the list of hot pixels closest in time to 
the image to be calibrated, and incorporates these data into the simulated 
dark. The hot pixel filenames contain the fractional year identifying the 
measurement epoch, as well as the file creation date.

The darks* directories are where CISSCAL writes the dark image files 
derived from this model, with directories named according to the epoch of 
the hot pixel file used. These directories are created automatically the 
first time the dark algorithm is invoked for an image in a particular 
epoch. Because of this, it is necessary that the user have write permission 
to the $CalibrationBaseDir/darkcurrent/ directory on the computer running 
CISSCAL.