Author:		Jeannie Walldren
Date:		2008-06-03
History:
	2008-06-03 Jeannie Walldren 
			- Original version
	2009-05-21 Jeannie Walldren 
			- A comparison of the IDL CISSCAL 3.6 files to IDL CISSCAL 3.3 files shows no change.
			- Updated documentation.


This directory contains calibration files for ISIS 3 CISSCAL's dark current correction.
They are derived from Cassini Orbiter ISS Volume 11 Version 2 (i.e. coiss_0011_v2).

	AAREADME_dark_isis3.txt 
		- This document, written for ISIS 3 CISSCAL info.
	darkcurrent_info.txt  
		- Describes original contents used by IDL CISSCAL 3.6
	nac_bias_distortion.cub
		- Copied directly from coiss_0011_v2


The idl CISSCAL darkcurrent calibration directory contains darks* directories 
to store dark image files derived from this model. These files are stored to 
speed up the dark subtraction process.  The ISIS 3 cisscal application does 
not store past dark image files, the array is calculated on the fly each time
the program is run using the parameter cube and label information.


In the idl CISSCAL program file, cassimg_subtractdark.pro, the median parameter files
were used and the derived parameter file usage was commented out, so we are using the 
median *.xdr and *.lbl files to create our parameter cubes.  If newer versions become 
available the following steps can be used to convert them into cubes.

1) Create raw files from xdr
  The .raw files were derived from nac_median_dark_parameters04228.xdr and 
  wac_median_dark_parameters04222.xdr by the following commands in idl:

	openr, params_lun,"nac_median_dark_parameters04228.xdr",/get_lun,/xdr
        params = fltarr(1024,1024,8)
	readu, params_lun, params
	openw, lun_out, "nac_median_dark_parameters04228.raw", /get_lun
	writeu,lun_out,params
	close,params_lun
	free_lun,params_lun
	close,lun_out
	free_lun,lun_out

2) Create isis3 cubes from raw files
  3 CASES:
  For SummingMode = 1, i.e. InstrumentModeId = FULL, 
  the *.raw files were converted in raw2isis with the extension *.full.cub:

	> raw2isis from=nac_median_dark_parameters04228.raw to=nac_median_dark_parameters04228.full.cub
	  samples=1024 lines=1024 bands=8 bittype=real 

  For SummingMode = 2, i.e. InstrumentModeId = SUM2, 
  first, the *.full.cub files were reduced to 512x512 by averaging a 2x2 block of 4 pixels,
  then, to get the sum, each pixel of the reduced cube is multiplied by 4:

	> reduce from=nac_median_dark_parameters04228.full.cub to=nac_median_dark_parameters04228.sum2.cub ons=512 onl=512 
	> fx f1=nac_median_dark_parameters04228.sum2.cub to=nac_median_dark_parameters04228.sum2.cub equation=f1*4 

  For SummingMode = 4, i.e. InstrumentModeId = SUM4, 
  first, the *.full.cub files were reduced to 256x256 by averaging a 4x4 block of 16 pixels,
  then, to get the sum, each pixel of the reduced cube is multiplied by 16:

	> reduce from=nac_median_dark_parameters04228.full.cub to=nac_median_dark_parameters04228.sum4.cub ons=256 onl=256 
	> fx f1=nac_median_dark_parameters04228.sum4.cub to=nac_median_dark_parameters04228.sum4.cub equation=f1*16 


	nac_median_dark_parameters04228.full.cub
	nac_median_dark_parameters04228.sum2.cub
	nac_median_dark_parameters04228.sum4.cub
	wac_median_dark_parameters04222.full.cub
	wac_median_dark_parameters04222.sum2.cub
	wac_median_dark_parameters04222.sum4.cub