Study On The Thermal Control Technique For Detector Components In Geostationary Solar X-EUV Imager

The observation and forecast of solar activity have both significant scientific meaning and application values.Solar X-EUV Imager is the newest generational space solar observational instrument,which adopts the internationally original creation that integrates both the X ray and the EUV imaging functions into one system.The imager is onboard the FY-4,Chinese geostationary meteorological satellite.The detector,as the key part of X-EUV imager,has to operate in low teperature.To control the temperature levels and the temperature gradients superior to the requirement,and further safeguard the imager obtain high quality pictures and optical parameters,it's necessary to study on the thermal control technique of the whole detector components.This paper firstly reviews the research significance and current research status of observing solar activity,concludes some typical thermal control technologies that used in domestic and international space solar observational instruments,next combine with solar X-EUV imager's characteristics,detector components' thermal control problems and this paper's research contents are demonstrated.To obtain the accurate external heat fluxes of imager with attitude change,the relative position among the imager,the sun and the earth is analyzed firstly,imager's attitude varies with time is calculated according to its sun monitoring mission,and finally the instantaneous external heat fluxes of imager are calculated based on both the environmental mapping planes after its attitude change and the radiation view factors given by direct integration method,by Matlab software.The results indicates that under the same orbit conditions,the total heat fluxes of imager with attitude change decreases dramatically by 372.5 W/m2 and 771.5 W/m2 compare to the stable attitude,in March equinox and December solstice respectively.,the heat fluxes on the +Z direction plane where optical entrace is located increases by 2 times,and especially the heat fluxes of this plane would flunctuate wildly when the imager entere into the earth shadow.These computational results provide good guidance for imager's thermal design in the next step.Move on to describe the thermal design for detector component,which includes: analyses the detector assembly's characteristics both in structure and the layout of internal heat sources,to help determine the location of radiating plane;analyses and finds the key thermal design parameters that affect detector's temperature by considering both the thermal design demands about CCD's low temperature and huge temperature difference with the surrounding components;uses the method of combining both the initiative thermal control and the passive thermal control technologies to carry out detailed thermal design.And then,to reduce the locally high temperature and thermal stress in space electronic devices as much as possible,a layout optimization and thermal design method based on genetic algorithm is proposed.Takes a PCB(Printed Circuit Board)in electrical box as an analysis object,its thermal resistance network model is constructed,and the mean square error of components' temperature is formulated as the objective function.Move on to use genetic algorithm by Matlab to obtain an optimized layout of 14 components in PCB,which arrange irregularly and is various in both boundary dimensions and power consumption.Finally,specific thermal design is implemented based on the optimized layout.IDEAS/TMG software is used to validate the model,the simulation results illustrates the junction temperature of all components are controled in the range of 50? to 67?,which satisfies the thermal control target of lower than 85?,moreover,compare to the empirical layout,the mean square error and maximum value of optimized layout components' temperature decreases 47.2% and 19.5% respectively,and it proves the feasibility and effectiveness of this layout optimization and thermal design strategy.Next,this paper demonstrates the thermal simulation of imager's detector component: to begin with,defines the extremely high and low working conditions according to the characteristics of heat fluxes and thermal control targets,next builds the finite element model of the whole imager by IDEAS/TMG and calculates the temperature levels of detector components under defined working conditions.The computational results show that,the minimum temperature of CCD during low temperature condition of March equinox is-64.3?,the maximum temperature of CCD during high temperature condition of December solstice is-50.4?,which satisfies the thermal control targets of-65? to-50?,and confirms the thermal control system that designed for detector components is able to provide a suitable thermal environment for imager's detector.Finally,this paper works out both the thermal balance experiment and thermal model correction problems of the detector components.The experimental results show that,the temperature of CCD can be maintain at the range of-65? to-50?,which verifies the validity of thermal design.In order to use experimental data to deduce a group of thermal design parameters that meets the practically thermo physical characteristics of detector components,to further minimize the temperature difference between experiment and simulation,this paper presents a thermal model parameters' modification procedure based on LHS(Latin Hypercube Sampling)and Powell method.To begin with,takes a series of experimental data in one of the tested conditions as correcting references,next establishes the objective function of 10 temperature monitoring points through least squares error fitting method,uses LHS to sample 20 thermal design parameters evenly and then implements relevant simulations,sorts these parameters by Spearman rate coefficients,move on to implement the layered correction of thermal design parameters by Powell method.Finally,these corrected arguments is set as the finite element model's parameters,and the results show that the temperature difference between simulation and experiment under the corrected working conditions is less than 2?,which verifies the corrected method is reasonable and effective.