Research On Stable Tracking Technology For Space Laser Communication

Space laser communication technology has received extensive attention due to its large transmission capacity,high transmission rate and strong security.However,due to the small divergence angle of laser,high-precision pointing and tracking technology is required for laser communication terminals to ensure the establishment and maintenance of laser communication links.In this paper,the stable tracking technology in space laser communication is studied,and the work is carried out from tracking unit design,tracking algorithm,and experimental testing.The main research contents and achievements are as follows:(1)The tracking subsystem is designed according to the requirements,including coarse tracking unit and fine tracking unit.The coarse tracking unit realizes large deflection range tracking,and the fine tracking unit realizes high-precision tracking.The deflection angle resolution of the coarse tracking unit matches the field of view of fine tracking,and the accurate measurement technology of beam deflection angle in coarse tracking and fine tracking is discussed.The coarse tracking unit and fine tracking unit are statically investigated.The static adjustment error of coarse tracking is ±40 μrad,the angle measurement resolution of fine tracking unit is better than 10 μrad.(2)The source of tracking error in the tracking process is discussed in detail,and the influence of those sources is analyzed with the tracking model.The motion state equation is established under the uniform motion model,and Gaussian noise is added to simulate the influence of platform vibration error and spot detection error.The tracking process is simulated and analyzed based on the Kalman filter algorithm.The results show that the Kalman filter algorithm has a good suppression effect on Gaussian noise and can compensate more than 90% of the dynamic lag error.The Kalman filter algorithm module is built in the Lab VIEW software platform to verify the effectiveness of the algorithm.(3)The tracking subsystem is built,and the static composite axis tracking experiment is carried out on the composite axis system composed of the coarse tracking unit and the fine tracking unit.The static tracking error of the tracking system is ±5 μrad.The tracking ability and tracking effect of the Kalman filter algorithm are verified and tested.In order to improve the stable tracking ability of the tracking system,an interactive multi-model control algorithm is constructed based on the Kalman filter.During the entire motion process,the tracking error is stable in ±40 μrad.