| On Dec.13th2012, Chang’e-2 probe made a success flyby of Asteroid 4179 Toutatis at a speed of 10.73 km/s in deep space of about 7 million kilometers away from the Earth with 770 m nearest distance, acquiring a series of optical images with high resolution better than 3m. It is the first time human acquire such clear images of Asteroid4179 in the world. In this paper, we process the radiation calibration data of imaging camera,obtaining original intensity of asteroid and its real surface radiance to study 4179 reflection characteristics of an asteroid’s surface, more details are given below.(1)A 1.6 m integrating sphere and spectrum radiator is used to obtain Chang’e-2solar panels monitor’s backup camera, which is the imaging camera of Asteroid 4179.Acquiring calibration data at ten radiance level, and RGB three spectrum.(2)The radiation calibration data of imaging camera are processed by least square fitting method, obtaining relative calibration correction matrix, recovering original intensity of asteroid 4179 and calibration data to reduce pixel response difference caused by inconsistent problem. By calibration results, we plan to acquire absolute calibration coe?cient,and recover original intensity of asteroid and its real surface radiance.(3) According to the Nicodemus’ s reflectance definition proposed by Hapke, the directional-hemispherical reflectance of Toutatis is obtained. The average surface albedo on R, G, B spectrum are obtained, respectively, and the asteroid’s surface albedo is calculated.Data indicate that, Toutatis is, somewhat, a red body in visible spectrum.The research approach based on spatial optical image are applicable to planetary science. This paper obtain surface spectral albedo and surface distribution of asteroid4179 based spatial optical image for the first time. The result of this study are high precision and provide support for further analysis of asteroid 4179 surface local optical properties as well as morphological features. |
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