Research On Thermal Radiation Characteristics And Effects Of Space Exposure Of Satellites

Research on thermal radiation characteristics of satellite has valuable applications in space technique, communications, navigates and targets detection. As the first protective barrier on the surface of satellite, thermal control coating is vital for the reliable operation of spacecrafts in orbit. However, the rigorous environment in space will exert the harsh effect on the spectral feature of thermal control coatings of spacecrafts. The coatings may be subjected to bombardment of ultra-fine particles and undesired radiation in the outer space. Protons, electrons, atomic oxygen, and ultraviolet radiation in space will induce performance degradation of the coatings on spacecrafts. It changes the thermal radiation characteristics of satellite and brings some unfavorable factors for the infrared stealth and target identification work of satellite. It's much important to further investigate on the degradation performance of thermal control coating exposured in space radiation.As thermal radiation characteristics of satellite to be the main research framework, a numerical model used to study the thermal radiation characteristics was proposed based on the computational simulation method. Especially, the environmental effects of space radiation on the degradation of thermal control coatings were carried out. Predicting model for the degradation of spectral properties of the coatings was established. Furthermore, some analysis on the variation behaviors of thermal radiation characteristics induced by the degradation of thermal control coating was carried out. The main work of this paper includes:1. Modeling research for thermal radiation characteristics of satelliteConsidering the influences of heat flux of space orbit, thermal control modes and heat load, temperature and infrared models of satellite were developed. The numerical models for some typical thermal control suites were proposed. The distributions of both temperature and radiation of satellites were obtained by finite volume method. Sensitivity affected by temperature-dependent parameters such as thermal conductivity and heat capacity were discussed. Infrared imaging model of point source target drawing in the district of detector was established and the distributions of its radiation intensity were produced in circumferential direction. Take into account of radiation transmission characteristic of the backgrounds consisted of earth and atmosphere, the infrared images of the backgrounds were shown in different wavelengths regions.2. Degradation model of solar absorption by thermal control coatingThe rigorous space environment which the thermal control coatings exposed to was introduced and the degradation model of the solar absorption was proposed. Under the guidance of the experimental data both at home and abroad, the formulations which describe the variation of optical parameters of thermal control coatings were deduced by the least square method. The accuracy of the degradation model was verified and degradation behaviors of the absorption factor for some typical thermal control coatings were predicted.3. Modeling for degradation behaviors of spectral properties of thermal control coatingsBy studying the physical components and the energy absorption mechanism, the factors which determine the spectral properties of the coatings are founded. Mathematical expressions for the variations of the influence factors have been introduced for complicated environment. The transmission mechanism of energy incident into a non-uniform refractive index transparent media was deeply studied based on the Mie's theory and Stratified Media theory. Based on these work, a predicting model for the degradation of spectral absorptance properties of the coatings is established. By using the theoretical model, degradation behaviors for both high orbit and low orbit was predicted which validated the above model gives a useful approach for predicting the degradation behaviors of thermal control coatings on spacecrafts in orbit.4. Development of integrated software for the thermal radiation analysis of satelliteBased on WINDOWS-operating system, integrated software for thermal radiation analysis of satellite (ISTRAS) was developed. It provides simulation functions as temperature distributions and infrared characteristic of the satellite. Moreover, it can be used for degradation behavior's research of satellite exposured in space radiation. The software's interface was compiled using MFC visual programming language, one can completed inputs and settings of parameters and related functions in the user's surface. OPENGL graphics library was used to generate the three-dimensional infrared thermal imaging results of target and background.