Analysis of Tracking Gimbal Angles for Inter-Satellite Optical Communication System Between Two Orbits

Abstract

This study focuses on the maximum angular velocity of the tracking gimbal, which can be one of the constraints for inter-satellite optical communication crosslinks between two intersecting orbits in a constellation. The angular constraint is due to the limits of both the tracking gimbal movement and the establishment of laser links. The torque caused by the angular acceleration of the gimbal can have little effect on the attitude control of the entire satellite. General formula and analysis for the azimuth and elevation gimbal angles in the satellite body-fixed coordinates system, including the case between rapid passing two orbits, have been shown in this study. Sensitivity analysis for various orbital phase and altitude differences is performed for some values. When the optical link vector passes near the zenith direction of the 2-axis gimbal, the angular velocity of the azimuth or elevation angle may increase beyond the constraint value. For avoiding this problem, it is necessary to set the phase difference between the satellites in both orbits. The margin of the altitude difference between both orbits can also mitigate the peak of rapid angular changes when they cross.