External Parameter Recalibration of the Binocular Cameras Onboard the Chang’e-4 Lunar Rover

There is a pair of binocular cameras for navigation onboard the Chang’e-4 lunar rover. Although the cameras were calibrated before launch, it is necessary to calibrate them again after landing on the moon, especially the external parameters. In this article, an image of a solar panel containing parallel-line features is used for recalibration. According to the collinear equations of an image point, object point and projection centre, the algebraic relationship between the slope k and intercept t parameters of a line in the image and the external parameters of the cameras are deduced. Through this algebraic relationship, we propose an external parameter recalibration method based on an image that includes parallel lines on a plane in the object space. Three experiments were carried out to evaluate the effectiveness and reliability of the proposed method.