Help for MASTERTOA

PURPOSE:

   MASTERTOA is a program that accepts as input MASTER TIR radiance at sensor 
image data and outputs expected upwelling radiance at the top of atmosphere
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:

   MASTERTOA 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 900 samples (one for the spectral response at each wavenumber
from 601 to 1500). 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.  MASTERTOA uses these parameters to run MODTRAN three times; once with a
nadir looking geometry, once for the case of viewing at maximum deflection
from nadir, and once with the observer at the top of atmosphere, nadir viewing.
From these three runs, the atmospheric transmittance and path radiance are 
calculated for the ten MASTER TIR bandpasses, for paths from the surface to 
the MASTER altitude, at all viewing angles. Also calculated are the path
radiance and the transmittance from the surface to the top of atmosphere,
nadir looking.  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 
formulas:

	Rad(at surface) = (Rad(at sensor)-Rad(path)) / transmittance
        Rad(at top of atmosphere) = RAD(at surface)*transmittance + Rad(path)

        (In the formulas above, transmittance and Rad(path) refer to
         the surface to MASTER path in the first formula, and surface
         to top of atmosphere in the second formula.)

   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.  Note that these units differ from the units that this program
output 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         May 12, 2000

COGNIZANT PROGRAMMER:  Ron Alley

REVISION: Version 1.1   November 12, 2004