isis_voyager_processing_notes.txt   RRH  2009_08_07  17:13

The following set of commands takes a Voyager image in PDS format,
reads it into ISIS, calibrates the intensity, and reprojects it for
a sinusoidal projection map.

Other ISIS commands can be used to correct spacecraft pointing before reprojection,
and to perform other types of projections.  There are also additional commands
for performing various photometric corrections, and for combining images
taken with different filters.

These commands use the new voyager processing instructions given in March 2009
on the ISIS help system at:
<http://isis.astrogeology.usgs.gov/IsisSupport/viewtopic.php?t=1970&highlight=>
These differ from the ones I used to generate the Howell & Lopes 2006 images.
Apparently those older ones are now out-of-date.

Further notes on ISIS processing are contained on the web page:
<http://faculty.gg.uwyo.edu/rhowell/data_analysis/data_analysis.html>

Voyager C1638942.IMQ is a good Loki image used in the 2006 paper.
Voyager images are names by the "FDS" clock time when they were taken,
in this case "16389.42".


---------------------------
Open a Konsole window

Run following to properly configure system for ISIS:
. $ISISR/sys/sh/3rdparty_path.sh

Start ISIS system by typing:
TAE

Note:  Often the following routines were run with "tutor pds2isis", etc.
"Tutor" lets you interactively set the parameters.  Once they are set you type "run".

If you know all the parameters you can just set them all on the command line.
I've listed multiple parameters on separate lines but really they should all be 
entered on a single line.  In most cases there are additional optional parameters.


COMMAND		PARAMETERS				 		COMMENTS

pds2isis 	from=C1638942.IMQ					Convert from PDS to ISIS format.
		to=c1638942.cub
		transtab=$ISISVOYDATA/vgr2isis_translation.def.3

vgrfixlabel	from=c1638942.cub					Fix label info in image.

levinit		from=c1638942.cub					Initialize as "Level 0" image

lev_findrx	from=c1638942.cub					Find "reseua" marks on image.

remrx		from=c1638942.cub					SKIP THIS STEP FOR NOW.
		to=newname.cub						DO NOT WANT HIDDEN ARTIFACTS
									WHICH CAN ARISE FROM REMOVAL.
									IF YOU RUN THIS, USE newname.cub
									IN THE FOLLOWING.

voycal		from=c1638942.cub					Calibrate intensity
		to=c1638942_cal.cub


									Before you run the next lev1tolev2 command, delete
									any "tfile.dat" file in the directory, otherwise
									the command will fail.


lev1tolev2	from=c1638942_cal.cub					Prepare to reproject the image.
		mappars=SINU:305					Specify output as sinusoidal proj., Central long=305.
		km=1							Specify output resolution as 1km (small pixels)

geom		from=c1638942_cal.cub					Actually perform reprojection.
		to=c1638942_sinu305.cub
		dninterp=nearest_neighbor    (or bilinear)		Keep blocky pixels, or interpolate for smooth ones.



Once done, either within "TAE" or from command line, the following will view the reprojected image:
qview c1638942_sin305.cub
                        

exit									will exit ISIS TAE system.

-----------Additional notes--------------------------

ISIS "Processing" Levels
There are 5 levels of processing for Voyager and Galileo data sets, they are:

    * Level 0 : Raw file conversion
    * Level 1 : Radiometric/geometric correction and artifact removal
    * Level 2 : Projection
    * Level 3 : Photometric correction and Tone matching
    * Level 4 : Seam removal 



Voyager filter characteristics are available on the PDS rings site.
The Voyager 1 info is at <http://pds-rings.seti.org/voyager/iss/inst_cat_wa1.html#filters>
For both Voyager 1 and 2 the conversions are:
Fltr#   Vgr 1 Narrow Angle      Vgr 1  Wide Angle
0       CLEAR #0                Methane-JST
1       VIOLET                  BLUE
2       BLUE                    CLEAR
3       ORANGE                  VIOLET
4       CLEAR #4                SODIUM-D
5       GREEN #1                GREEN
6       GREEN #2                METHANE-U
7       ULTRAVIOLET             ORANGE