A daytime sky analytical model of the degree of polarization for JHKs bands

Abstract

The navigation technology of the near-earth space star sensors based on short-wave-infrared (SWIR, especially for JHKs bands) is a focused frontier research area. The research group has built an analytical model of daytime zenith radiance, which has a practical guiding value for optical system design, physical process simulation, and software integration development. However, it is not inadequate to consider only the spectral energy distribution of the sky background. In order to expand the approach of star identification, improve the contrast of target-to-background, and enhance the sensitivity of star detection, it is necessary to consider the polarization pattern of the daytime sky. Therefore, a sky analytical model of the degree of polarization for JHKs bands is constructed based on the Rayleigh sky model, which comprehensively takes into account the depolarization effect caused by the reflection of the earth-surface, the anisotropy of the air molecules, and the Mie scattering of the aerosol particles. The model's fitting precision is evaluated based on the error between raw data and analytical values, and the model's validity is confirmed based on the deviation between measurement data and simulation data. The results indicate that the analytical model of daytime sky degree of polarization is constructed exactly and can provide a more robust reference for the star sensor's project demonstration, performance assessment, and optimization design based on SWIR technology.