Study On UV-VUV Solar Spectrometer And Spectral/Radiation Calibration

Solar radiation is the most important energy source of the earth,and its energy change has a wavelength dependence,the change of energy at UV-VUV band is more obvious.Long-term monitoring influence of solar activity changes on solar UV-VUV spectral radiation,and studying on characteristics of background changes for radiation energy,which are of great significance for research solar physics,atmospheric physics and climate physics.Long-term montoring of small change in solar activity,which requires monitoring instrument with high-precision,high-stability and high-accuracy,etc.However,the high-precision calibration of monitoring instrument is the necessary guarantee of high-accuracy measurement.In this paper,developing relevant research whose spaceborne UV-VUV solar spectrometer and spectral/radiation calibration for the long-term monitoring of small change in solar activity,laying the foundation for guarantee obtaining high-precision,high-resolution and high-accuracy of solar spectral irradiance data on-orbitm and the research has important application value.Based on that fully understanding the characteristics whose high rejection-ratio of stray light and small,light weight in the research of spaceborne UV-VUV solar spectrometer,the theory whose concave grating dispersion subtraction of double monochromator,the principle whose wavelength scanning mechanism determines the wavelength accuracy of spectrometer.For the characteristic of weak signal in solar ultraviolet spectrum,the performance of photomultiplier tube is studied,a set of quantum efficiency calibration system based on standard vacuum phototube is constructed,and the standard transmission of the phototube is completed,meanwhile the direct measurement of the quantum efficiency of the phototube in the band of 150nm-300nm is realized.Verifying the response differences in different windows and the temperature response characteristic of photomultiplier tube.And providing theoretical basis for detector seclection of the research of spaceborne UV-VUV solar spectrometer.In order to meet the requirement of high-precision radiation calibration,the key performance of spectrometer was studied,especially the stability,thus guiding the optimization of calibration methods.The feasibility of the combined design of fused quartz plate and diffuse transmission plate is verified,which can improve the long-term stability of the optical system of the spectrometer.The signal to noise ratio(SNR)of the spectrometer system was analyzed and theoretically estimated,and a set of system SNR measurement device under atmospheric environment was constructed.The SNR measurement was completed and compared with the theoretical estimation results.Aiming at the stray light with high rejection ratio of 60D,the stray light measurement was completed by using the method of liquid absorption tank with high rejection ratio,which solved the problem of developing ultraviolet band filter with more than 70D.A set of linear measuring device was constructed by using the new method of double flux superposition combined with neutral filter to realize the linear measurement with high precision and large dynamic range,and the dynamic range reached the order of 105.The total uncertainty of linear measurement of the spectrometer system was 0.48%.In order to meet the radiation calibration research,and achieve high-precision calibration requirement,the spectral calibration method of spectrometer with high spectral resolution was studied and implemented.The wavelength precision and wavelength repeatability were obtained by using line spectrum lamp,which laid a foundation for the high-precision radiation calibration of spectrometer.Based on the theory of radiation calibration whose the synchrotron radiation with primary standard transfered standard source deuterium lamp.The total uncertainty of the calibration spectrometer of PTB standard deuterium lamp at 165nm-320nm band was 5.40%;NIST halogen tungsten lamp calibration spectrometer at 250nm-310nm band,the total uncertainty is 2.80%;The difference of irradiance responsity of the two calibration sources were compared and analyzed.On the basis of uncertainty analysis of calibration,in order to solve the problem that the accuracy of VUV band calibration of spectrometer is less than 3%absolute calibration.Using German PTB synchrotron radiation source as the standard for the absolute calibration of the UV-VUV solar spectrometer in progress.The influence of the polarization of synchrotron radiation on the calibration accuracy of the spectrometer is analyzed theoretically,and a set of polarization response measurement deviece was constructed,meanwhile the polarization responsivity of the spectrometer is obtained.The diffuser reduced the polarization effect which is analyzed and verified.In order to ensure the signal is constant and reduce the effect of polarization to radiation calibration accuracy,proposing a method of rotation calibration to eliminate polarization,the polarization effect reduced to 0.5%.finally,the scheme of the UV-VUV solar spectrometer synchrotron radiation calibration whose uncertainty is forecaste analyzed.It is clear that the total uncertainty of absolute calibration by this scheme is increased to 2.2% under the condition that all indexes of the UV-VUV solar spectrometer meet the requirements of absolute calibration accuracy,provided that the uncertainty transmitted in each link of the calibration process is guaranteed.