Abstract：Accurate spectral irradiance measurement is very important in the field of Earth observation. In optical radiation measurement, a cosine diffuser is often used to improve the accuracy of irradiance measurement results at different azimuths. The cosine response characteristic is the key factor of the spectral irradiance sensor in the field measurement. This paper studied the cosine response characteristics of the commonly used spectral irradiance instrument for ground object observation, and a spectral irradiance experimental measurement system was established. The variation rules of the instrument's spectral irradiance measurement results at different angles were obtained through experimental methods, and the cosine curve was fitted by MATLAB software. The influence of the traditional angle response normalization method and the offsetting angle response normalization method on the instrument cosine error was analyzed. Compared with the traditional normalization method, the maximum cosine error of the spectral irradiance instrument was reduced from 11.2% to 7.7% by using the offsetting normalization method, and it was almost independent of the wavelength changes. This is mainly due to the limitation of the optical path structure inside the instrument and the diffused material. When the incidence angle θ changes, the spectral irradiance angle response deviates from the cosine function. Therefore, based on the cosine response characteristics of the instrument and the experimental results of cosine error, a method for correcting the cosine error of the spectral irradiance was proposed. By extrapolating the single wavelength fitting function to all bands for correction processing, the deviation between the correction value of the instrument's spectral irradiance and the standard cosine response curve is less than 1.7%, and the cosine error is reduced from 8% to less than 2% in the range of -55~55°. The correction method greatly reduces the influence of cosine error on the instrument's measurement results, improves the instrument's measurement accuracy under different azimuths, and meets the high precision application requirements of field measurement, such as earth observation and ocean remote sensing.
王玲玲，李 玲，潘 江，代彩红，吴志峰，王彦飞. 余弦响应误差对光谱辐射照度测量的影响规律及修正方法研究[J]. 光谱学与光谱分析, 2025, 45(06): 1739-1743.
WANG Ling-ling, LI Ling, PAN Jiang, DAI Cai-hong, WU Zhi-feng, WANG Yan-fei. Study on the Effect of Cosine Response Error on Spectral Irradiance Measurement and Its Correction Method. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(06): 1739-1743.
