ISIS Application Documentation
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Radiometric correction of Clementine UV/VIS camera images
| Overview | Parameters | Example 1 |
Description
This program performs radiometric corrections to images acquired by the
Clementine spacecraft UVVIS camera. It performs dark subtraction,
readout correction, non-linearity and flat field corrections and
gives the user the option of writing the output image values as radiance
values or as reflectance(I/F) values.
PLEASE NOTE: In the ISIS2 Fortran code the method FIXTEMP uses a REAL*4 (6 digits of accuracy) to store the RIMGID (8 digits) which results in the last digits being lost. In the table that references RIMGID the value is a REAL*4 again resulting in the same loss of precision; this makes the lookup table for temperature corrections inaccurate. ALGORITHM General algorithm applied to data for radiometric correction is described below: Step 1. Global Offset Correction Step1_DN = raw_DN - C4*OffsetModeID - C5 C4 = -8.177 C5 = 15.56 Step 2. Divide by gain Step2_DN = Step1_DN / g(GainModeID) g(GainModeID) g(1) = 1.0 g(2) = 2.907 g(4) = 6.906 Step 3. Dark current correction Step3_DN = Step2_DN - (DC + C3) C3 = 7.13 Non-linearity correction XMUL = ACO + BCO*Step3_DN + CCO*(Step3_DN**2) + DCO*(Step3_DN**3) CorrectedStep3_DN = Step3_DN * XMUL ACO = 1.062 BCO = -.1153E-02 CCO = .6245E-05 DCO = -.1216E-07 Step 4. Temperature-Dependent Offset Correction Step4_DN = CorrectedStep3_DN - C2 * u C2 = .003737 * exp(.0908*(T-273.15)) T = Corrected FocalPlaneTemperature (The value in the labels is not correct. The value used is taken from an interpolated set of values from ACT) u = t + readout time t = ExposureDuration + .0494 readout time = 60.05 + .05*(line # - 1) Step 5. Frame Transfer Correction Step5_DN = Step4_DN - ro ro = column_sum*dt/(t+288*dt) column_sum = sum of all 288 Step4_DN values dt = frame transfer time per row = .00068 t = ExposureDuration + .0494 Step 6. Flat-Field and Exposure Time Normalization Step6_DN = Step5_DN / (FF*t) FF = Filter-dependent flat-field t = ExposureDuration + .0494 The units of Step6_DN are now in counts/ms. Step 7. Normalize to Sun-Moon distance of 1 AU Step7_DN = Step6_DN * (SolarDistance in AU)**2 Step 8a. Conversion to 1 AU Relative Radiance L = Step7_DN / C1 ( L = Radiance in mW/sr-cm**2 ) CenterFilterWavelength C1 415 nm 1.39 750 nm 2.57 900 nm 4.35 950 nm 4.76 1000 nm 2.77 Step 8b. Conversion to Reflectance R = Step7_DN * CR The following CR values were derived by Eric Eliason on 6/20/96. These are slight improvements over Carle Pieter's values because Eric used the most current flat files and Alfred McEwen's non-linearity correction. For more information, see Eric's memo from 6/20/96. CenterFilterWavelength CR 415 nm .021406 750 nm .012266 900 nm .010674 950 nm .010831 1000 nm .024271 Note: if the cub has a compression ratio of 1.0 (the cube is uncompressed) it will use difference flat field file. CategoriesRelated Objects and DocumentsApplicationsHistory
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Parameter GroupsFiles
Settings
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Files: FROM
Description
Specify the input file to be corrected.
| Type | cube |
|---|---|
| File Mode | input |
| Filter | *.cub |
Files: TO
Description
Specify the output file. The result will be the radiometrically corrected image. The output values can either be output as absolute radiance or converted to reflectance (I/F) values.
| Type | cube |
|---|---|
| File Mode | output |
| Pixel Type | real |
| Filter | *.cub |
Settings: CONV
Description
This option allows the output values to be written as absolute radiance or converted to reflectance values (I/F).
| Type | boolean |
|---|---|
| Default | true |
Settings: TCOR
Description
This option defines whether or not to use temperature correction. If disabled, the focal plane temperature read from the labels is used (if it is not equal to zero, otherwise temperature correction is used anyways). When TCOR is enabled, the temperature read from the labels is disregarded and a table is searched based on the orbit number and mission phasederived from the ProductID stored in the labels.
| Type | boolean |
|---|---|
| Default | true |
Settings: DARKCURRENT
Description
This option allows the user to input a constant value for the dark current, or alternatively a cube file with dark current values (default).
| Type | string | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Default | DCFILE | |||||||||
| Option List: |
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Settings: DCCONST
Description
This constant will replace the array of dark current coefficients in the derived dark current file. In most cases, the default should be used for this parameter to indicate the derived dark current file is to be used.
| Type | double |
|---|
Settings: DCFILE
Description
This parameter allows the user to use an alternate dark current file. In most cases, the default should be used for this parameter to indicate the derived dark current file is to be used. The name of the derived dark current file is $ISISDATA/clementine1/calibration/uvvis/dark_5_15_96.cub.
| Type | cube |
|---|---|
| File Mode | input |
| Internal Default | Automatic |
| Filter | *.cub |
Settings: FFFILE
Description
This parameter allows the user to use an alternate flat-field file. In most cases, the default should be used for this parameter to indicate the derived flat-field file is to be used. There is a different version of the flat file for compressed and uncompressed images. The name of the derived flat-field file is $ISISDATA/clementine1/calibration/uvvis/lu[filter]_[un]comp_flat_long.cub. An example for a compressed B filter image is $ISISDATA/clementine1/calibration/uvvis/lub_comp_flat_long.cub.
| Type | cube |
|---|---|
| File Mode | input |
| Internal Default | Automatic |
| Filter | *.cub |
Example 1Calibrating a cube to I/F values using temperature correction Description
Calibrating a cube to I/F values using temperature correction
Command Line
clemuvviscal
clemuvviscal FROM=lua1841h.cub TO=lua1841h.cal.cub TCOR=TRUE
In this example clemuvviscal will calibrate lua1841h.cub using temperature correction.
GUI Screenshot
Input Image
Output Image
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