Study On Ground Calibrations Of High Spectral Resolution UV-VIS Imaging Spectrometer

For past decades,it had extremely requirements on high spectral resolution imaging spectrometers as satellite-borne detectors in designs,functions,and performances,especially precision,to adapt for the rapid development of remote sensing technology and satisfy its needs.The high precision of space optical remote sensors depends on the performances of the instruments and quantitative inversion analyses,which obtain the amounts of target gases from the primitive data.The accurate ground calibration is an indispensable technology of quantitative inversion analyses,and it needs to face the complexities of the ground tests and calibrations for high precision optical remote sensing imaging instruments.Therefore,it is necessary to build up a complete ground calibration system for space-borne optical imaging spectrometer in demand.The study on high precision ground calibrations in this dissertation is completed for the High Spectral Resolution UV-VIS Imaging Spectrometer,a double channels imaging spectrometer working at the spectral range from 300 nm to 500 nm based on the hyperspectral imaging technology.The contents of this dissertation are organized as follows:In chapter 1,there is a comprehensive introduction to the recent international and domestic developments of space optical remote sensors and ground calibrations of high spectral resolution imaging spectrometers.The High Spectral Resolution UV-VIS Imaging Spectrometer is mentioned from the structure,the principle,and the main performances.According to those,the requirements on ground calibrations in this dissertation are explicit.In chapter 2,the instrument with a low voltage mercury lamp source is demonstrated for the ground spectral calibration of High Spectral Resolution UV-VIS Imaging Spectrometer.The results show that the spectral range of the High Spectral Resolution UV-VIS Imaging Spectrometer is from 375 nm to 500 nm in visible channel with an uncertainty of 0.02798 nm.In order to achieve an accurate slit function of the spectrometer,the slit function measuring device is created related to the characteristics of large fields,wide wavelength ranges,and high spatial and spectral resolutions.The output of the slit function measuring device is a series of well-distributed narrow band spectrum,and the slit function of the spectrometer is obtained from the device output.The results show that the slit function of the spectrometer is approximately fitting Gaussian distribution.The spectral resolution in the field edge is slightly below to the one in the field center due to the smile effect.The overall spectral resolution of Hyperspectral imaging spectrometer is between 0.42 nm and 0.5nm.In chapter 3,the study is focused on the measurements of the field and the spatial response functions of the High Spectral Resolution UV-VIS Imaging Spectrometer by using the slit function measuring device.The results show that the total field of the imaging spectrometer is 112.5°,and the spatial response function is approximately fitting Gaussian distribution.The spatial resolution of sub-satellite points is between 1.36 ° and 1.62 °,and the spatial resolution in the field edge is between 1.48 ° and 1.81°.In chapter 4,the contents are about the radiance calibration of the High Spectral Resolution UV-VIS Imaging Spectrometer.Firstly,the calibration theory is discussed on the principle and method.Secondly,the radiance calibration is performed by the diffuser method.The experiment is carried out with the irradiance standard lamp(F18)and standard diffusers,which are known BRDF.There were two methods which named distance method and BRDF method in data processing.The results show that the uncertainty of the radiance calibration which calculated by distance method was 3.2%-4.9%,the maximal deviation of the two methods was 5.3% because the diffuser was non-standard Lambertian surface.In chapter 5,the measuring methods of polarization sensitivity for Dual Babinet Compensator Pseudo-depolarizer(DBCP)and the instrument are studied.The depolarization performance is tested after the working principle demonstrated.The results show that the DBCP has a better depolarization performance in no more than 15° of the incidence angle that the depolarizer owns a depolarizationin better than 99%,the uncertainty of the measurement is 2.9‰ as well as uncertainty of the High Spectral Resolution UV-VIS Imaging Spectrometer is 2.1%.In chapter 6,diffuser calibration and testing in the High Spectral Resolution UV-VIS Imaging Spectrometer are studied.Firstly,the descriptions of the diffuse properties are introduced,and the BRDF measurement principle and method are discussed.Then the BRDF of diffuse aluminum plate and PTFE were tested and the results were compared.The results show that the aluminum diffuser's BRDF dropped about 50% with large scattering angle,the results were 10% by a change of material of polytetrafluoroethylene(PTFE)which experiment conditions wassame as the previous,the uncertainty of the measurement is 4.1%.