Measurement of sky background luminance characteristics

Sky background luminance is very important in imaging and optical information transition in space. The existing sky luminance simulation codes, such as Modtran cant be suitable for different climate and global location. Therefore, we developed a sky luminance measurement device and obtained a lot of experimental data. By analyzing these data, we found that in homogeneous sky background, the sky spectral luminance decreases with the increase of solar angle in general, but when the angle between observation direction and ground plane is less than 30, the luminance increases with the decreasing solar angle. In fine and cloudless sky background, the sky luminance is concentrated at short-wave band, while in cloudy background there is obvious redshift of the luminance spectrum.