The Earth Radiation Budget Experiment (ERBE) is an operational system of radiometric instruments placed in Earth orbit by the National Aeronautics and Space Administration (NASA). Its purpose is to monitor those components of the Earth radiation budget which influence the weather and climate. The active cavity radiometer (ACR) instruments on board the ERBE satellites are periodically calibrated against internal standards and against the relatively well-known solar constant. In order to better understand the dynamic behavior of the instruments, a high resolution dynamic model has been developed and used to simulate the solar calibration. The instrument dynamic model consists of two elements: a radiation distribution factor model and a finite element model of the heat conduction process. The distribution factors, which lie at the heart of the simulation, distribute the thermal radiation incident to the instrument aperture over the diffuse-specular active cavity surface. The results of the model for a transient analysis during solar calibration are compared with two sets of operational data provided by NASA. Very acceptable agreement is found between the model results and the operational data. / Master of Science