Geometric Calibration of the ESA Mars Express Orbiter High Resolution Stereo Camera

The high-resolution stereo camera mounted on the Mars Express (MEX) spacecraft of the European Space Agency is specifically designed for planetary photogrammetry and mapping missions. High-precision geometric calibration is required to maintain the geometric quality of satellite imaging. This study aimed to develop a Martian geometric calibration model based on the detector look angle and offset matrix to compensate for systematic errors caused by the camera system parameters, Doppler shift measurements, and other parameters of the interior and exterior orientation during positioning. Moreover, the difficulty in identifying high-precision geometric ground control points from extra-terrestrial imagery was addressed by proposing an iterative Mars Orbiter Laser Altimeter extraction algorithm based on the similarity measure of terrain relief. Using this algorithm, constraint conditions were established, and a calibration model was introduced to achieve in-orbit geometric calibration of the MEX satellite. The proposed method is effective in reducing the distortion of the camera in calibration images from 12 pixels to <1 pixel, both before and after calibration. Moreover, the plane accuracy of validation images improved from approximately 900 to 200 m, while elevation accuracy improved from 500 to 100 m, verifying the effectiveness of the proposed method.