A preliminary result of self-calibration bundle adjustment of Chang'E-2 stereo imagery

Abstract

The high resolution lunar global images acquired by Chang'E-2 (CE-2) CCD camera orbiter are of great importance for lunar science research as well as preparation of the landing and surface operation of Chang'E-3 (CE-3) lunar rover. In this paper, a rigorous geometric model of CE-2 CCD camera is developed based on the push-broom imaging principle. A self-calibration bundle adjustment (SCBA) method is proposed to eliminate the inconsistencies between forward- and backward-looking images, which are caused by the inaccuracy of exterior orientation (EO) parameters and the uncertain relationship between the two CCD line arrays of the camera. The interior orientation (IO) model is refined by adding several additional parameters and the EO parameters are fitted by a third-order polynomial model. Strategies for ensuring the robustness and reliability of the solution are also adopted, including EO pseudo observations selection, reasonable weight determination, and truncated singular value decomposition method. After adjustment, the inconsistencies between the forward- and backward-looking images are eliminated effectively by reducing the image-space residuals from around 20 pixels to sub-pixel. Based on the adjustment, high precision DEM (Digital Elevation Model) and DOM (Digital Ortho Map) of a local area at Sinus Iridum (pre-selected CE-3 landing site) are generated automatically.