| Spectral radiometric calibration is the basis and prerequisite for the quantitative application of remote sensing information.The laboratory establishes the radiation response model of the remote sensor through continuous spectral radiation sources with radiation standards,and modifies the calibration model parameters through site/onboard calibration during the orbit.At present,UV remote sensing is tending to develop with high resolution and high precision.However,the accuracy of UV band radiation working standard is low and the aperture of continuous spectrum radiation source is small.Therefore,it is of great significance to carry out the research of radiation standard transfer for the calibration of large-aperture UV remote sensor.On the basis of summarizing and analyzing the existing radiation standard transfer links,the paper proposes the UV band radiation standard transfer theory and algorithm based on the filter radiometer,constructs the UV continuous spectrum radiation source radiation physical model,uses the polynomial combined with Planck’s blackbody radiation law model for the blackbody light source,and derives the optimized iterative algorithm to solve the radiation physical model.The radiation output has a function expression,which can be used for color temperature estimation,The radiation standard transfer of continuous spectrum radiation source at 232-350 nm is realized.In combination with the problems of low responsivity in the UV band and serious out-ofband leakage of the filter,a filter radiometer based on the sun-blind phototube is designed as the UV standard transfer radiometer.The characteristics of the sun-blind phototube such as out-of-band leakage suppression and response nonlinearity are researched using the system-level spectral responsivity measurement method.The results show that the out-of-band leakage is effectively suppressed,and the response nonlinearity is less than ± 0.5%in the working dynamic range.According to the radiation transfer theory of integrating sphere,the design parameters of Lambert surface source are optimized,the process of integral polytetrafluoroethylene pressed coating with an inner diameter of 2.2 meters is proposed,and the ultraviolet fluorescence effect of the coating is discussed.By introducing a high-power external xenon lamp light source and cooperating with a hightemperature resistant precision electric aperture,the UV radiation output adjustment with high brightness and large dynamic range is realized.The research on the optical characteristics of the high-brightness,large-aperture UV integrating sphere radiation source shows that its angular nonuniformity is less than 1.04%in the range of ±30°,and its plane nonuniformity is less than 0.94%,and its radiation brightness reaches 5 times of the solar constant at 250 nm.Finally,the standard transfer method based on the sun-blind filter radiometer is applied to the UV continuous spectrum radiation source.In order to verify the accuracy of radiation transfer,the radiometer was used to measure the irradiance standard lamp,and the irradiance value of the standard lamp was fitted using the optimized iterative algorithm based on the physical model.The result was compared with the irradiance standard value given by the NIM,and the maximum deviation was 1.44%,which verified the correctness of the method,and also verified the normal state of the filter radiometer.Secondly,the method is applied to the developed large-aperture and highbrightness UV integrating sphere radiation source.The spectral radiance of the source is obtained through the established xenon lamp radiation physical model and the optimized iterative algorithm fitting,and the uncertainty is better than 5%.The radiation physical model of the continuous spectrum radiation source is constructed.The filter radiometer based on the sun-blind phototube is used as the UV standard transfer radiometer.The optimized iterative solution algorithm is used to fit the output radiance of the light source to be measured,and the transfer of the radiation scale to the continuous spectrum radiation source to be measured is realized.The standard transfer method is applied to the developed large-aperture,high-brightness UV continuous spectrum radiation source to realize the transfer of the radiation standard to the radiation source.It provides a high-brightness calibration source for the establishment of the radiation response model of the laboratory before the launch of the UV remote sensors,and provides a guarantee for the application of high-precision UV remote sensing information quantification. |
