Geometric Calibration of Parameters in the Perpendicular-Orbit Circular Scanning Satellite Camera

Perpendicular-orbit circular scanning satellites overcome the conflict between ground resolution and width observed in traditional optical satellites by using a perpendicular-orbit circular scanning imaging method and splicing along the orbit, achieving a balance between an ultra-large width and a high resolution. However, laboratory calibrations of perpendicular-orbit circular scanning satellites exhibit large errors due to the influence of factors such as the thermal and mechanical environment of space during the launch and operation of satellites, and thus, they cannot be applied. In this paper, we start by analysing the in-camera azimuth element errors of perpendicular-orbit circular scanning satellites, then derive a probe element pointing angle calibration model from the physical in-camera calibration model and carry out in-camera parameter calibration based on simulated image data from an ultra-wide perpendicular-orbit circular scanning satellite. Edge and centre strips were selected for the experiment, and a certain number of control points were placed uniformly near the middle column (perpendicular orbit) of the image in each strip and covering all row directions (along orbit). Checkpoints were uniformly selected across a range of widths. The results show that in-orbit geometric calibration can significantly improve the direct-to-ground positioning accuracy of perpendicular-orbit circular scanning satellites, with the positioning accuracy error shown to be better than 30 m within a width of 300 km, 30 m within a width of 1000 km, and 50 m within a width of 2000 km.