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)

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.