The peculiar behavior observed in the TDE (Total Dose Experiment) on board the KITSAT-1 is identified as the thermal effect due to the change in the eclipse rate of the satellite. Similar behavior is seen in the laboratory experiment as the temperature of the RADFET, the TDE sensor, is varied from 20 degrees C to 80 degrees C while it is being irradiated with Co-60 gamma-ray source. Present study focuses on the modeling effort of separating the radiation and thermal effects from the complicated data in which these two effects are simultaneously present. We derive the device parameters from the non-thermal irradiation data, cmd then include thermal annealing and conversion of oxide charges to estimate the oxide trap and interface state charges in the case of thermal variation. The model fits the experimental data quite successfully, which will enable us to estimate the pure radiation effect on the TDE experienced in space.