Calibration method of spectroradiometer based on direct solar irradiance

The scattering channel of a spectroradiometer, as a commonly used optical parameter measuring device, can measure irradiance in all directions of the sky. To improve the calibration accuracy and efficiency, this paper proposes a spectral radiometer scattering channel calibration method based on direct solar radiation intensity. The direct solar radiation channel of the spectral radiometer can measure the solar radiation transmitted through the atmosphere in real-time and atmospheric transmittance. Combined with the solar radiation intensity at the top of the atmosphere and the optical component parameters of the instrument, the calibration value of the scattering channel of the full band can be obtain. The calibration values obtained by separately calibrating the integrating sphere and the transfer calibration are applied to calculate the all-sky background radiation. The deviation of the transfer calibration from the integrating sphere calibration is calculated and found to have an average deviation of less than 5%. By comparing the spectral radiation calculated using two calibration methods when fixed-point observation is used, it is found that the average deviation is less than 5%. The above comparison shows that the transfer calibration has good calibration accuracy and will be used in devices that measure both direct solar light and atmospheric scattered light.