| As a common optical detection instrument,the spectroradiometer is mainly composed of an optical tracking and acquisition system,a two-dimensional control turntable and a fixed base.The optical tracking and acquisition system is mounted on the two-dimensional control turntable for spectrum acquisition in both horizontal and tilt directions,and the side wall of the turntable has an embedded development board for the development of the instrument control software.The development board is connected to the server through a transmission protocol,and a human-machine interface is designed at the server display control terminal for real-time control.In the development stage of the instrument,higher automation,standardization and humanization are needed.Depending on the way the solar radiation outside the atmosphere passes through the atmosphere and reaches the sky or the ground,the spectroradiometer can measure in both direct and scattering modes,obtaining spectral information of direct solar radiation in the direct measurement mode and scanning the whole sky and obtaining real-time spectra in the scattering measurement mode.In the data processing stage,the accuracy of direct and scattering calibration methods directly affects the accuracy of the inversion of atmospheric optical parameters,so the study of calibration is a common research project for spectroradiometers.Long-term observations of spectroradiometers are a relatively scarce resource,and long-term observations of fixed locations and analysis of optical properties can be explored in depth.Based on the above,the research of this paper is shown as follows:(1)Based on the structure of the original spectroradiometer,redesign the instrument hardware development board to adapt to various functions;in the embedded development board control software development,improve the problems of the original control software to achieve faster and more automated acquisition of spectra,and compile and debug the software;in the human-computer interaction interface of the display and control terminal,redesign the interface to make it more user-friendly,and improve the real-time data transmission,mapping and other functions;(2)In depth study on the calibration method of spectroradiometer direct radiation.Then,we propose a hybrid calibration method based on the modified Langley method,which can obtain the calibration value in the strong absorption band in combination with the solar irradiance at the top of the atmosphere,and also conform to the instrument response law.In the actual measurement process,the precipitable water measured by the modified Langley calibration method and the hybrid calibration method are compared with the precipitable water measured by the POM radiometer,and it is found that the measurement results of the hybrid calibration method are closer to those of the POM radiometer,and the average relative error is less than 10%.The transmittance data is also calculated using the modified Langley calibration and the hybrid calibration method,and compared with the transmittance data measured by the POM radiometer,the relative error of the hybrid calibration method is smaller in the 940nm water vapor strong absorption band;(3)The scattering channel calibration method of spectroradiometer is studied in depth,and the transfer calibration method based on the solar irradiance at the top of the atmosphere is proposed.The traditionally used integrating sphere calibration method is costly and cumbersome.The sun itself is a stable light source,and the calibration of the top-of-atmosphere solar irradiance is transferred to the scattering channel based on the calibration value of the direct channel instrument,combined with the instrument optical parameters.In the actual measurement,comparing the background radiation distribution of the whole sky calculated by integrating sphere calibration and transfer calibration,it is found that the average relative error is below 5%;for the spectral irradiance,the average relative error of the two methods is also below 5%,which has great application value in the actual measurement;(4)Observations are carried out in the western suburbs of Hefei Science Island area using spectroradiometers.The atmospheric transmittance,aerosol optical thickness,atmospheric precipitable water,sky background radiation distribution and atmospheric irradiance in different directions are obtained from the observed raw data through calibration and data processing,and the changes of these optical parameters in the Hefei area during the observation period are analyzed to verify the laws of spectral absorption and scattering.Actual measurements shows that the improved spectroradiometer has a more standard process in hardware expansion and development and is less prone to unpredictable failures;the design of the embedded and master software makes the instrument more automated for self-starting measurements and complete functionality.The experimental validation results show that the proposed direct channel hybrid calibration method and scattering channel transfer calibration method are more accurate and do not rely on external calibration instruments,which is more cost effective.The accumulation of spectroradiometer data can enrich the research on the characterization of atmospheric optical parameters in the Hefei area and improve the understanding of radiation transmission. |
