Research On Acquisition, Pointing & Tracking Technique For Satellite Optical Communication Systems

Inter-satellites laser communication is superior to RF communication in speed, secrecy, volume, weight, and power dissipation. As a promising technology for space activities, Inter-satellites laser communication will play a prominent role in future free-space communication network.In inter-satellites laser communication system, when satellites start communication, they must finish the processes of acquisition, pointing and tracking (APT). The first step for APT system is to scan and capture the position of target satellite. Expect for the narrow laser beam divergence and large transmission distance, the instability of satellite and vibrations in the system as well add up the great difficulty to the scan and capture, which makes the process quite difficult. Therefore, to design an APT system with high performance is the guarantee of the normal inter-satellite communication, which is also one of the difficulty and key techniques in free-space laser communication.After analyzing the main task of the APT system, this paper proposes a novel scheme for scan and capture of optical communication terminal based on TMS320LF2407 DSP chip and, meanwhile, presents the designs of the software and hardware for the drive system. Considering the characteristics of vibrations in the practical communication environment, the paper adopts a fuzzy-PI arithmetic in the close loop control to fulfill the self-adjustment of the parameters, which has high dynamic and static performance. Furthermore, this paper also analyses and compares several scanning methods of laser beam, and implements the spiral and raster spiral scanning arithmetic.The experimental results indicate that the control system is well-designed and feasible with a reliable performance, and it has achieved the scheduled dynamic and static requirement.