On-Orbit Geometric Calibration of Star Camera Based on Block Pointing Model and Angular Distance Consistency
Star cameras provide high-accuracy attitude determination for optical satellites, enabling precise geometric positioning of imagery without ground control points. However, affected by launch vibrations and thermal variations, the on-orbit geometric distortion differs significantly from ground measurement results, degrading attitude determination accuracy. Traditional methods typically rely on a physical model to characterize distortion, suffering from low accuracy at the detector edges. This article proposes a novel on-orbit geometric calibration method based on a block pointing model and angular distance consistency (BPMADC). Based on geometric distortion characteristics, the pointing calibration models for the main and local blocks are established. Using the consistency of stellar angular distances, the distortion parameters are solved without interference from attitude parameters. An order-staged solution and weight optimization are proposed to improve calibration accuracy. The calibration accuracy of star camera B of the Luojia3-02 satellite is improved from 0.352 pixels to 0.214 pixels. Furthermore, distortions at the detector edges are effectively calibrated. Validation data acquired on October 2, October 12, November 9, and November 26 are used to evaluate the calibration accuracy and stability of the camera parameters across different stellar regions and measurement times. The improvement rates are 48.249%, 26.856%, 44.049%, and 41.547%, respectively. Furthermore, experimental results demonstrate that the proposed method effectively improves geometric calibration accuracy and supports high-precision attitude determination for optical satellites.