Help for MASTERTIR

PURPOSE:

   MASTERTIR is a program that accepts as input MASTER TIR radiance at sensor 
image data and outputs upwelling radiance at surface for the thermal infrared
channels (Channels 41-50).  Also required as input are a valid MODTRAN input
file, to define the atmospheric model, and a MASTER TIR spectral response
file.


OPERATION:

   MASTERTIR takes as input the 10 Channels of MASTER TIR radiance at sensor
data in units of Watts per square meter per steradian per micrometer, and a
file containing the the MASTER TIR spectral response functions. This second
file must be a VICAR labelled file consisting of ten lines (one for each TIR
channel) and 800 samples (one for the spectral response at each wavelength
from 7.00 to 14.99 micrometers, in 0.01 micrometer increments). The spectral 
response functions must be normalized, i.e., the sum of all values on each 
line must be 1.0.
   The atmospheric model used is defined by a user supplied MODTRAN input
file.  MASTERTIR uses these parameters to run MODTRAN twice; once with a
nadir looking geometry, and once for the case of viewing at maximum deflection
from nadir.  From these two runs, the atmospheric transmittance, path
radiance, and downwelling sky radiance at surface are calculated for the ten
MASTER TIR bandpasses.  The downwelling sky radiance values are placed in
the VICAR label of the output dataset.
   Values of transmittance and path radiance are calculated for each pixel
location in the scene by interpolation, where it is assumed that each
quantity varies linearly with path length.
   The upwelling radiance at surface is then computed by the following 
formula:

        Rad(at sensor) = RAD(upwelling)*transmittance + Rad(path)

It should be noted that the output quantity (upwelling radiance) of MASTERTIR
differs from the output quantity of TIMSCAL2 (surface emitted radiance). It
it includes both the surface emitted component plus the surface reflected
component.
   The output dataset consists of 10 channels of real (32 bit floating
point) pixels, in units of Watts per square meter per steradian per
micrometer.  These units are the same as the input units, but different than
the units produced by this program prior to November, 2004.  The downwelling
sky irradiance values that are placed in the VICAR label are in units of 
milliWatts per square meter per micrometer.  To convert to radiance in units 
consistent with the output images, one must divide by 1000.0*pi.


WRITTEN BY:  Ron Alley         August 12, 1998

COGNIZANT PROGRAMMER:  Ron Alley

REVISION: 1.4 Nov 12, 2004