Thermal Control Design Of Spatial Reference Blackbody Source And Characteristic Analysis Of Phase Change Fixed Point

During the long-term orbit operation,due to the impact of shock,vibration and natural aging,the calibration accuracy of the space payload is reduced due to the inevitable drift of quantity value,and the uncertainty in the calibration process is expanded.Therefore,the construction of a traceable spatial reference blackbody source plays an important role to the development of climate monitoring,weather forecasting,disaster prevention and mitigation,infrared remote sensing,and radiation calibration,et al.A spatial reference blackbody source traceable to international system of units(SI)is constructed in this thesis,and the characteristics of the cavity normal emissivity and the micro phase change fixed point are studied in depth.The research is of great significance for the development of spatial reference blackbody source and micro phase change fixed point and metrological traceability.The on-orbit metrological traceability technology of platinum resistance is introduced systematically,and based on this technology and the emissivity on-orbit measurement technology,a mechanical structure of spatial reference blackbody source with temperature traceability is constructed.And six kinds of micro phase change fixed points filled with mercury(Hg),water(H2O),gallium(Ga),gallium indium alloy(Ga-In),gallium-tin alloy(Ga-Sn),and 70 degrees Celsius alloy are applied,its working temperature range is 230K-350 K.In addition,the space reference source energy transfer model is developed by the mechanism of radiation-heat conduction-phase change coupled heat transfer,a preliminary thermal analysis is performed on the space reference black body source,and the position,size and resistance of the heater are determined.Numerical simulation and experimental study on the emissivity of spatial reference blackbody source cavity are carried out.A directional emissivity calculation model was established based on Backward Monte Carlo method(BMCM)and bidirectional reflection distribution function(BRDF)on the surface of the material.The numerical simulation shows that the normal emissivity of the pure diffusion isothermal black body cavity in the 8-14μm band is 0.999172.The normal emissivity based on the controlled background emissivity measurement platform is 0.9990 with an uncertainty of 0.117%.In addition,the effects of detection distance,temperature non-uniformity,and radiation characteristics of the material surface BRDF emissivity are analyzed through emissivity calculation model.A large number of numerical simulations prove that the above factors have different degrees of influence on the emissivity in measurement,and the performance of spatial reference blackbody source can be improved by enhancing the backward reflection capability on the cylinder.The characteristics of the fixed point of the micro-phase transition are thoroughly studied based on the spatial reference blackbody source energy transfer model.On the one hand,the relationship between heating power and steady state temperature of the system is analyzed,the results of numerical simulation and experiment in vacuum radiance temperature standard facility prove that the logarithmic model better conforms to the relationship between heating power and steady state temperature.On the other hand,the effects of initial value,input heat flux,and system adiabaticity on the characteristics of micro phase change fixed point are studied.A large number of numerical simulations prove that the performance of the micro phase change fixed point(Ga)can be effectively improved by reasonably regulating the input heat flux and the system adiabaticity.