Daytime all-sky radiance distribution pattern for near-earth space SWIR stellar navigation

Short-Wavelength-Infrared (SWIR) stellar navigation technology is a focused area of frontier research in near-earth space. However, in the process of star trackers' optical scheme demonstration, imaging link construction, and algorithm test optimization, large-scale sky background data in JHKs bands with different atmosphere modes, aerosol types, earth-surface types, and sun positions are required as inputs. Although the existing atmospheric radiative transfer code can generate extensive uncontinuous background radiation data, some inherent defects, including high computational complexity, low work efficiency, and long operation time, severely restrict the application in engineering. For the purpose of making sky background radiation data far more productively in action, it is essential to establish the distribution model to describe the characteristics of sky background radiation. Therefore, the daytime all-sky radiance distribution pattern for JHKs bands is built based on the Hosek model, and the Adaptive Moment Estimation (Adam) method is applied to solve and optimize the distribution parameters. The correctness of the distribution pattern is verified based on the measurement data. The results show that the daytime all-sky radiance distribution pattern is constructed exactly and can provide a firm reference for SWIR star trackers' system design and performance evaluation.