Satellites traditionally used for weather monitoring have proven to be very useful in environmental monitoring. Thus, the ability to compare the measured radiances from independent instruments has become increasingly important. The Cooperative Institute for Meteorological Satellite Studies (CIMSS) has been intercalibrating five geostationary satellites (GOES-8, -10, METEOSAT-5, -7, GMS-5) with a single polar orbiting satellite (NOAA-14 HIRS and AVHRR) on a routine basis for over a year using temporally and spatially co-located measurements. The primary focus of this effort has been in comparing the 11-µm infrared window channels. Similar efforts are being made for the 6.7-µm water vapor channel. The numerical methods for conducting the routine intercalibration are being updated. This includes updating the radiative transfer forward model used to estimate the differences in calculated brightness temperatures based on spectral differences between satellite instruments. This poster presents the results and effects of those changes on the calculations.