The results of the space radiation experiments carried out on board the first two Korean technology demonstration microsatellites are presented in this research. The first satellite, KITSAT-1, launched in August 1992, carries a radiation monitoring payload CRE (Cosmic Ray Experiment) for characterizing the low-Earth orbit (LEO) radiation environment. The CRE consists of two sub-systems: the Cosmic Particle Experiment(CPE) and the Total Dose Experiment(TDE). In addition, SEU rates of the program memory and the RAM disk are also monitored. The peculiar behavior observed in the TDE (Total Dose Experiment) 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℃ to 80℃ while it is being irradiated with $Co^60$ γ-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, and 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. The second satellite, KITSAT-2, launched in September 1993, carries a newly developed 32-bit OBC, KASCOM (KAIST Satellite Computer) in addition to OBC186. SEUs occurred in the KASCOM, as well as in the program memory and RAM disk memory, have been monitored since the beginning of the satellite operation. These two satellites, which are very similar in structures but different in orbits, provide a unique opportunity to study the effects of the radiation environment characterized by the orbit. KOMPSAT-1, which will be launched in the end of 1999, carries a space environment monitoring package SPS(Space Physics Sensor). SPS consists of two sub-systems : the High Energy Particle Detector (HEPD) and the Ionosphere Measurement Sensor (IMS). The IMS measures the {\rm in-situ} electron temperature and density in the ionosphere. This measurement is performed by operating one circular sensor plate (ETS) and one cylindrical antenna (LP) in a mode which provides a characteristic Langmuir probe measurement. The circular sensor plate is swept in voltage of 30 kHz sine oscillation with three different amplitudes and the DC component of the shifted voltage of the 30 kHz sine oscillation due to the surrounding plasma is measured with the corresponding amplitude. The DC component of the voltage shift is used to derive the electron temperature. The HEPD is to characterize the low altitude high energy particle environment and the effects on the microelectronics due to these high energy particles. It consists of four sensors: Proton and Electron Spectrometer(PES), Linear Energy Transfer Spectrometer(LET), Total Dose Monitor(TDM), and Single Event Monitor(SEM). 35 MeV proton beam from the medical KCCH cyclotron, at Korea Cancer Center Hospital in Seoul, is used to calibrate the PES. Primary proton beam of 35 MeV scattered by polypropylene target is converted to various energy protons according to the elastic collision kinematics. In this calibration, the threshold level of the proton in the PES can be determined and the energy ranges of PES channels are also calibrated.
