An Earth-Limb-Constrained Framework for On-Orbit Geometric Calibration of GEO Wide-Field Area-Array Cameras

On-orbit geometric calibration is essential for maintaining the geometric positioning performance of optical remote sensing cameras throughout their operational lifetime. Existing calibration approaches primarily rely on ground control points (GCPs) or stellar observations, which are often constrained by reference availability, observation conditions, and operational requirements, particularly for GEO wide-field imaging systems. To address these limitations, this paper proposes an Earth-limb-constrained framework for on-orbit geometric calibration of GEO wide-field area-array cameras. The proposed framework establishes geometric constraints by relating the observed Earth limb to reference Earth limb geometry derived from the camera imaging geometry and the WGS-84 reference ellipsoid. A unified geometric calibration model is developed by introducing an equivalent camera-to-inertial attitude representation, and terrain elevation information from the Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) is further incorporated as a local geometric constraint during calibration parameter estimation. The calibration parameters are estimated by minimizing the elevation residuals of multiple Earth limb observations through nonlinear optimization. The proposed framework is validated through both simulation and real GEO on-orbit experiments. Simulation results under different attitude-error settings demonstrate accurate parameter recovery and stable convergence, while experiments using thirteen GEO image scenes show an approximately 69% improvement in geometric positioning accuracy. An additional ablation experiment confirms that incorporating SRTM terrain-elevation information further improves the calibration performance. These results demonstrate the effectiveness and practical applicability of the proposed framework for GEO wide-field area-array cameras. By reducing the dependence on GCPs and dedicated stellar observations, the proposed framework provides a practical approach for the long-term geometric performance maintenance of GEO optical remote sensing systems.