DETECTION OF THE ANGLE CHANGE BETWEEN CAMERA AND STAR TRACKER BASED ON STAR OBSERVATION

Abstract. Satellites in orbit are affected by changes in thermal environment and other factors, and the angle of optical axis between the camera and star tracker (Cam-ST) changes. As a result, the attitude measurement error of the orbital period appears, leading to a decrease in the accuracy of the geometric positioning of the image. This paper proposes a star observation mode, using the stars as the control point, so as to detect the angle change between the Cam-ST throughout the orbital period. This paper is based on 20 sets of star observation data from the Jilin-1 video satellite. Through methods such as star point extraction and pre-recognition, the camera's pointing in the inertial space is obtained. Then the angle with the optical axis of star tracker (ST) is calculated, and the error law of the angle between the Cam-ST is obtained. The experimental results show that the Cam-ST optical axis angle will produce a regular error change during the satellite orbit period. After fitting, the error of the angle between the camera and the star tracker (Cam-ST) is reduced from 47.86" to 5.63". Through the method of star observation, the errors between Cam-ST angle can be effectively improved. The high accuracy of the camera's pointing measurement within the orbit period range is of great significance for satellite global mapping without ground control points (GCPs).