A Physics-Informed Error-Propagation Framework for Four-Quadrant Sun Sensors: Modeling and Experimental Validation

High-precision solar irradiance and attitude measurements require sun sensors with stringent pointing accuracy. However, narrow-FOV Four-Quadrant Analog Sun Sensors (FQASS) are strongly affected by coupled structural, electronic, and optical errors. This work presents a unified methodology that integrates sensor design, error modeling, and calibration-based compensation. Quantitative error analysis is combined with electronic response calibration, full-FOV angular calibration, and ray-tracing simulation to develop a physics-informed error-propagation framework. Experiments using a dual-axis scanning system verify that the proposed method accurately reproduces full-FOV error behavior and effectively suppresses systematic errors. After compensation, the central-FOV error is reduced to 0.0188°(3σ), most full-FOV errors remain within 0.0294°(1σ), and the maximum error is 0.0506°. The method provides a reliable and generalizable solution for high-precision error characterization and compensation in FQASS.