Help for MIVISTIR

PURPOSE:

   MIVISTIR is a program that accepts as input MIVIS TIR brightness temperature
at sensor image data and outputs upwelling radiance at surface for the thermal 
infrared channels.  Also required as input are a valid MODTRAN input file, to 
define the atmospheric model, the MIVIS TIR spectral response file, and the 
MIVIS radiance lookup table.


OPERATION:

   MIVITIR takes as input the 10 Channels of MIVIS TIR brightness temperature
at sensor data in units of degrees Celsius, multiplied by 10, a file 
containing the the MIVIS TIR spectral response functions, and the MIVIS
temperature to radiance lookup table. The 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 third file must be a temperature to radiance lookup table
in the format common to MIVIS, MASTER, MAS, and TIMS.
   The atmospheric model used is defined by a user supplied MODTRAN input
file.  MIVISTIR 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
MIVIS 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 MIVISTIR
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 halfword (16 bit signed
integer) pixels, in units of milliWatts per square meter per steradian per
micrometer.  Note that these units are 1000 times smaller than the input
units.


WRITTEN BY:  Ron Alley         November 68

COGNIZANT PROGRAMMER:  Ron Alley

REVISION: New