Study On The Characteristic Of The Whole Sky Background Radiation

Background sky radiation means the spatial distribution of sunlight absorbed and scattered by particles in the atmosphere. It is extensively used in the area of retrieving aerosol optical properties, detecting atmospheric components and the spatial distribution of clouds, detecting and identifying of space target.To measure the whole sky brightness distribution, a new method was proposed. Fixed point observation and full-sky scanning of 350～1100nm can be realized. Spectral resolution is 0.5nm. Fixed point observation can obtain sky brightness of any direction in the sky. Full-sky scanning can achieve the brightness of the range of level 0～360° and pitching 0～90°. The measured data is compared to simulated data by MODTRAN5 and integral luminance meter, and the reasons of error are analyzed.Using the measurement system carry out experiment in Hefei. After one scanning of the whole sky,649 samples of radiance can obtained. Measuring position of each sample is used as pixel, some wavelength’s radiance of the position is used as gray level. The distribution of whole sky background radiation spectrum band is obtained.The characteristic of sky background radiation distribution is drawed by the preliminary analysis of measured data. From the observed data, with the decreasing zenith angle of the sun, the sky brightness increases; in the sunny day, all sky background radiance distribution is symmetric about connection of the sun and the zenith. Clouds affect the distribution of the sky brightness. In the end, the effect of different atmosphere mode, types of aerosols and atmospheric visibility on the sky brightness were analyzed.