AIRS

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Q.  How do I calculate brightness temperatures from AIRS L1B data?  

A.  If AIRS L1B channel frequency and radiance are:

nu in cm^-1
flux in milliWatts/(m^2 cm^-1 steradian)

use constants:

h = 6.6260755e-27 erg s
k = 1.380658e-16 erg/K
c = 2.99792458e+10 cm/s

test to ensure that radiance flux is not -9999 (value if invalid)

then calculate

c1 = h*c/k
c2 = 2*h*c*c

and the brightness temperature is:

BT = (c1*nu)/alog( 1.0 + ( (c2*nu^3)/flux) )

where alog returns the natural logarithm

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