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USGS

ISIS Application Documentation


vimscal

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Radiometric correction of Cassini VIMS camera images.

Overview Parameters

Description

This program applies a dark current and a flat field correction to images, then converts the output units to either specific energy or I/F.

Dark Current:
The dark current correction for VIS consists of reading a binary ".tab" file from $cassini/calibration/vims and subtracting derived values from this file.
The dark current correction for IR consists of reading the sideplane data (stored in a SideplaneIr table in the cube) and subtracting this from the input cube. If "CompressorId" is available then the sideplane data was already subtracted from the file, but the linear fit capabilities are still available to re-do the dark current with a linear fit instead of the default subtraction. If spectral summing is on then no dark current can be applied. If spectral editing is on then the linear fit on the dark current can not be applied. Sideplane keywords for IR are as follows:
  • None = No dark current subtraction (applied by the instrument)
  • Sideplane = Sideplane was subtracted only without fitting a line
  • Fit Delta = Sideplane was previously subtracted so the difference between the sideplane and linear fit function subtracted
  • Fit = A linear fit was applied to the dark current values and the result was subtracted


Flat Field:
For both VIS and IR this determines the correct file from $cassini/calibration/vims/flatfield and divides the input data by the flat field data.

Subareas
The offset and swath keywords will be respected by running "crop" on the calibration files appropriately and using the cropped calibration files.

Categories


History

Steven Lambright2009-06-24 Original version
Steven Lambright2009-08-03 The solar distance calculation is now much more likely to succeed
Steven Lambright2009-12-16 Better error handling - fewer temporary files left around
Steven Lambright2009-12-17 Sped up program by not searching a pvl much more than necessary, improved error messages
Steven Lambright2010-02-19 Now closing calibration files when done with them
Steven Lambright2010-07-23 If the solar remove coefficient cannot be calculated then a default value will be used now instead of giving an error
Steven Lambright2010-11-23 Added an option to not do dark current correction
Steven Lambright2012-09-28 Fixed the default value for the solar remove coefficient. Without this fix, some resulting files had I/F values much larger than 1.0. Fixes #1143.
Tracie Sucharski2013-09-09 The Ir exposure duration in the Vims labels is incorrect due to the inaccuracy of the Vims clock. The Ir exposure duration needs a correction factor of 1.01725 applied before using. References #1759.
Tyler Wilson2016-09-15 Updated vimscal to make use of RC19 files. Instead of having one calibration cube for solar/specific energy/wavecal data, there are now 14 cubes (one for each year in the range 2004:2017). This is because of the wavelength calibration shift as a function of time described in "The VIMS Wavelength and Radiometric Calibration White Paper", Roger N. Clark, Robert H. Brown, Dyer M. Lytle. Draft submitted to the NASA Planetary Data System: 07/19/2016. Changes to the application are minimal. The BandBin:Center keyword value was also updated for all calibrated cubes to reflect the new knowledge concerning wavelength shifts. Fixes #4370.
Tyler Wilson2017-01-03 Added the ability for users to select which flatfield file they want to use during calibration. The default option is to continue using the original flatfield files. References #4370.

Parameter Groups

Files

Name Description
FROM Input Isis cube
TO Output Isis cube

Options

Name Description
UNITSOutput units
FLATFIELDFlatfield file
IRORIGDARKDo not smooth IR Dark Current
DARKDo Dark Current Corrections
X

Files: FROM


Description

Use this parameter to choose an Isis cube to be calibrated. To ensure that it contains all needed keywords in its label, input cube should have been imported using vims2isis and, if "I/F" is chosen, input cube must have been run through spiceinit application.

Type cube
File Mode input
Filter *.cub
Close Window
X

Files: TO


Description

Use this parameter to select the output filename of the calibrated Isis cube.

Type cube
File Mode output
Pixel Type real
Filter *.cub
Close Window
X

Options: UNITS


Description

Type string
Default IOF
Option List:
Option Brief Description
SPECENERGYSpecific Energy This option indicates that the output is in terms of specific energy (ergs/sec/spectel).
IOFI/F This option indicates that the output is in terms of solar flux (I/F). Input cube must have been run through the spiceinit application.
Close Window
X

Options: FLATFIELD


Description

Type string
Default 2006Flat
Option List:
Option Brief Description
2006FLAT2006 Flatfield
2006SSFLAT2006 Spectrally Summed Flatfield
2013FLAT2013 Flatfield
Close Window
X

Options: IRORIGDARK


Description

By default Isis will fit a line to the dark current values, on each band, across the lines since there is one dark value per line. The linear fit value will be applied correctly even if a dark current was applied to this cube beforehand. This disables the line fitting for the dark current. This parameter has no effect for VIS cubes.

Type boolean
Default false
Close Window
X

Options: DARK


Description

If this is false then no dark current values will be subtracted.

Type boolean
Default true
Close Window