Design and verification of a hyperspectral instrument for atmospheric and water optical properties observations.

Long-term, continuous in-situ observations of atmospheric and water optical properties are crucial for understanding the impacts of climate change, revealing pathways of atmospheric material transport, and studying air-sea interactions. For ocean color satellite sensors, sustained in-situ measurements are crucial in supporting their on-orbit calibration, the validation of high-level data products, and the development of data processing algorithms. This study presents what we believe to be a novel autonomous instrument called the hyperspectral sun photometer (HSP) designed for long-term, continuous, and synchronous measurement of atmospheric and water optical properties. The HSP delivers measurements across the 400-1020 nm spectral range with a spectral resolution of 1 nm. The performance of the HSP was evaluated through comparative observations with the CE-318 T sun photometer. The results demonstrate that within the visible spectrum, the HSP and CE-318 T achieve consistent results at common wavelengths: the discrepancy in aerosol optical depth (AOD) is within 7%, while the maximum difference in water-leaving radiance is only 4.74% at 667 nm. The temporal stability of HSP observations for different targets verifies its operational robustness. In summary, the HSP can serve as a stable instrument for the synchronous in-situ measurement of atmospheric and water optical properties.