On-Orbit Calibration Method for Star Sensors Based on Microvariation in Intrinsic Parameters

Environmental variation in space may lead to microvariation in intrinsic parameters of the optical system, which significantly impacts the accuracy of attitude for star sensors. Currently, on-orbit calibration methods for star sensors mainly treat microvariation in intrinsic parameters as system noise, resulting in the model is not accurate. This article proposes an on-orbit calibration method for star sensors based on microvariation in intrinsic parameters (IPV method). First, we established a mathematical model of "star image variation-intrinsic parameters variation" using angular distance (AD) variation. Then, based on this mathematical model, combined with the extended Kalman filter (EKF) method, the state equation and the measurement equation are established to calibrate the microvariation of intrinsic parameters, and a complete on-orbit calibration method is established. The purpose of this method is to ensure a more accurate attitude of the star sensor, so we adopted a standard of the attitude error to evaluate the calibration performance. Finally, the experimental results show that the IPV method can improve the accuracy of attitude by 35% when using a star sensor with a small field of view (FOV). We also verified the IPV method in the case of distortion, and the results show that the IPV method can still achieve good performance. Therefore, the IPV method can achieve high-precision calibration results, especially suitable for high-precision star sensors with small FOV.