vimscal
Radiometric correction of Cassini VIMS camera images.
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:
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.
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 Lambright | 2009-06-24 | Original version |
| Steven Lambright | 2009-08-03 | The solar distance calculation is now much more likely to succeed |
| Steven Lambright | 2009-12-16 | Better error handling - fewer temporary files left around |
| Steven Lambright | 2009-12-17 | Sped up program by not searching a pvl much more than necessary, improved error messages |
| Steven Lambright | 2010-02-19 | Now closing calibration files when done with them |
| Steven Lambright | 2010-07-23 | If the solar remove coefficient cannot be calculated then a default value will be used now instead of giving an error |
| Steven Lambright | 2010-11-23 | Added an option to not do dark current correction |
| Steven Lambright | 2012-09-28 | 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 Sucharski | 2013-09-09 | 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 Wilson | 2016-09-15 | 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 Wilson | 2017-01-03 | 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. |