Study On Polarization Properties Of Skylight In Different Moon Phases

Due to the influence of scattering particles in the atmosphere,the sky light is polarized and forms a stable and regular polarization pattern in the sky.Insects like Cataglyphis and Dung beetle could recognize skylight polarization pattern through the dorsal rim area of their compound eyes.The ability of insect inspires researchers to develop bionic polarization navigation.At present the polarization pattern of sunlight has been greatly improved in the study of skylight polarization law.Because the testing environment and period are limited,there are lest studies on the polarization pattern of skylight at night.Hence,in order to explore the law of polarization pattern of night skylight and provide the foundation for application of bionic polarization navigation at night,the polarization pattern of night skylight in different moon phases was studied in this paper.Firstly,the scattering process of skylight was analyzed and the reason for polarization properties of skylight was demonstrated.Secondly,when the moon and sun are in different directions,the theoretical polarization patterns are simulated based on single Rayleigh scattering theory.The polarization pattern of skylight on land in different moon phases and the polarization pattern of waxing gibbous moon at sea were tested.The polarization pattern of skylight was studied through an analysis of neutral point and the direction of the meridian in the polarization pattern.A contrastive study of measured polarization pattern in different moon phases was carried to study the effect of moon phase on polarization pattern of skylight at night.The measured polarization pattern was compared with theoretical polarization pattern of moonlight and sunlight to analyze the difference between the measured result and the theoretical simulation.At the same time the law of polarization of night skylight was explored.The comparative results showed that when the illuminated area of moon is larger,the measured polarization pattern of skylight has the same rules as the theoretical pattern after nautical twilight,and it accords with Rayleigh scattering theory.When the illuminated area of moon is smaller,the measured polarization pattern of skylight is easily affected by artificial lighting.So the measured polarization pattern doesn't accord with theoretical pattern,but the measured polarization pattern also has stable polarization pattern.The polarizarion pattern of moonlight at sea is similar to that on land.The angle of polarization and the direction of the meridian of the measured results accord with theoretical pattern,so Rayleigh scattering theory could be uesd to analyze the law of skylight polarization pattern at sea.