clemnircal

INTRODUCTION

This program performs radiometric corrections to images acquired by the Clementine spacecraft Near Infrared camera and writes the output image values in units of radiance.

EQUATIONS

Term1 = ( DR(x,y) - digital_offset ) / Gfact(gm)
Term2 = Term1 - bias_global - BIAS(x,y) - (om * V)
Term3 = Term2 / t
Term4 = Term3 - DC(x,y) - 0.730
Term5 = Term4 - therm - thermShape
Term6 = Term5 / FF(x,y)
Term7 = Term6 / OF(x,y)
Term8 = Term7 - AF(x,y)
R(x,y) = Term8 * abscoef

General equations applied to data for radiometric correction are indicated below:

Let: x,y = line and sample position of pixel in an image
R(x,y) = Result of correction in absolute radiance.
DO(x,y) = Result of correction. The output can either be absolute radiance values or they can be converted to reflectance(I/F values
DR(x,y) = Raw input density number
FF(x,y) = Flat-field as a function of filter and line, sample
position. This will be read from an ISIS cube file.
OF(x,y) = Orbit dependent flat file correction.
DC(x,y) = Dark current as a function of compression type,
line, sample position. AF(x,y) = Empirical additive flat-field coefficients at line, sample position.
BIAS(x,y) = Bias correction as a function of compression type, line, sample position.
digital_offset = 9.0
bias_global = 2.0
V = -.91
abscoef = 1.0
g(GainModeID) = Gain factor as a function of insturment GainModeID
g(0) = 2.0235
g(1) = 8.2755
g(2) = 4.9144
g(5) = 0.9443
g(8) = 4.1835
g(9) = 1.3530
g(11) = 15.9844
g(13) = 7.77177
g(16) = 28.1618
g(17) = 24.8658
g(18) = 21.9100
g(19) = 18.6140
g(22) = 6.83130
g(23) = 3.48425
g(24) = 20.3218
g(25) = 17.9433
g(26) = 15.8104
g(27) = 13.4320
g(28) = 9.32361
g(29) = 6.95951
g(30) = 4.75472
g(31) = 2.43896
g(33) = 13.9238
g(34) = 12.2687
g(36) = 7.23501
g(41) = 7.04438
g(42) = 6.16495
g(44) = 3.57405
g(45) = 2.73995
g(46) = 1.88595
g(48) = 11.9078
g(50) = 9.26433
g(52) = 5.39513
g(53) = 4.08125
g(61) = 1.40899
g(62) = 0.964975
gm = Gain_mode of instrument(gm = 1,2,4)
om = Offset_mode of instrument(om = 1,2,3,4,...,31)
t = Optimal integration duration of observation in seconds (function of ExposureDuration on labels in milliseconds.)
therm = Thermal background correction value
thermShape = Thermal shape correction value (always 0.0)

Description

Specify the input file to be corrected.

Type	cube
File Mode	input
Filter	*.cub

Description

Specify the output file. The result will be the radiometrically corrected image.

Type	cube
File Mode	output
Pixel Type	real
Filter	*.cub

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.

Type	cube
File Mode	input
Internal Default	Automatic
Filter	*.cub

Description

The parameter allows the user to use an alternate orbit dependent flat-field file. In most cases, the default should be used for this paramter.

Type	cube
File Mode	input
Internal Default	Automatic
Filter	*.cub

Description

The parameter allows the user to use an alternate emperical additive flat-field file. In most cases, the default should be used for this parameter.

Type	cube
File Mode	input
Internal Default	Automatic
Filter	*.cub

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 file is to be used. The name of the derived dark current file is "$ISISDATA/clementine1/calibration/nir/dark_nir.cub" When InstrumentCompressionType = "CLEM-JPEG-0" the name of the derived dark current file is "$ISISDATA/clementine1/calibration/nir/dark_nir_cmp0.cub"

Type	cube
File Mode	input
Internal Default	Automatic
Filter	*.cub

Description

This parameter allows the user to use an alternate bias file. In most cases, the default should be used for this parameter to indicate the derived bias file is to be used. The name of the derived bias file is "$ISISDATA/clementine1/calibration/nir/bias_nir.cub" When InstrumentCompressionType = "CLEM-JPEG-0" the name of the derived bias file is "$ISISDATA/clementine1/calibration/nir/bias_nir_cmp0.cub"

Type	cube
File Mode	input
Internal Default	Automatic
Filter	*.cub

Description

This parameter allows the user to use an alternate bad pixel file. In most cases, the default should be used for this parameter to indicate the derived bad pixel file is to be used. The name of the derived bad pixel file is "$ISISDATA/clementine1/calibration/nir/badpix_nir.v3.cub" When InstrumentCompressionType = "CLEM-JPEG-0" the name of the derived bad pixel file is "$ISISDATA/clementine1/calibration/nir/badpix_nir_cmp0.v3.cub"

Type	cube
File Mode	input
Internal Default	Automatic
Filter	*.cub

Description

This option allows the user to decide whether to keep or remove known bad pixels. When enabled, DN values of 0.0 in the bad pixel cube are known bad pixels that will be set to NULL in the output.

Type	boolean
Default	true

Description

Apply thermal background correction

Type	boolean
Default	true

Description

Absolute coefficient

Type	double
Default	1.0

Description

DN values greater than this value in the input cube will be set to HRS.

Type	double
Default	240.0

Calibrating a cube to radiance values using nircal

clemnircal nircal FROM=lna3056k.cub TO=lna3056k.cal.cub

Calibrate clemnircal.cub

Calibrate lna3056k.cub In this example clemnircal will calibrate lna3056k.cub using the defaults.

lna3056k.cub before being corrected

Image before correction Parameter Name: FROM This is the input image lna3056k.cub before being corrected with clemnircal.

lna3056k.cub after being corrected

Image after correction Parameter Name: TO This is the input image lna3056k.cub after being corrected with clemnircal. There are scattered NULL pixels because BPFLAG was true, so all known bad pixels were automatically set to NULL.