Research On Fast Acquisition And Stable Tracking Method With Narrow Beacon In Satellite Optical Communication Link

Satellite optical communication(SOC)has the characteristics of large capacity,high confidentiality,strong anti-interference and so on,which is one of key techniques of High-Speed/Real-Time Space-Ground Integrated Network(SGIN).SOC laser link should be required to be quickly established and stably maintained.Early SOC system generally uses a wide beacon for bidirectional acquisition and tracking,and the divergence is typically in an order from hundreds of microradian to milliradians,which leads to more than 10 W power to generate wider beacon.And separate power supply,light source,shaping light and splitting light path are also required,which would make terminal weight,size and power consumption increasing greatly.In order to adapt development of SOC networking,the terminal should be highly integrated,small and lightweight,which allows for the use of narrow beacon.Due to the factors of long distance of link,small divergence,relative movements,platform vibrations and so on,it is necessary to develop high efficient pointing,acquisition and tracking(PAT)system to establish inter-satellite laser link when narrow beacon is used.However,for technical confidentiality,there are few reports on study of narrow beacon acquisition/tracking technology.Therefore,this dissertation focuses on the establishment and maintenance of SOC links based on narrow beacon,and studied the methods of rapid acquisition,stable tracking and in-orbit performance optimization.Firstly,the dissertation has established a quick narrow beacon based acquisition model,and given a method to evaluate the acquisition performance.The acquisition probability and average acquisition time influenced by satellite drift have been studied.A multi-scann acquisition has been proposed and simulated.Under the condition of limited scanning time,the method of multi-field scanning can be used to quantitatively predict the best scanning field for different satellite drift rates,and effectively improve the acquisition probability of narrow beacon satellite laser links.By establishing bidirectional/stable tracking model of narrow beacon SOC link in theory,the time-domain form and equivalence transformation relationship of the large closed loop stability controller with bidirectional beam were given.Based on the typical 2nd dynamic system theory,the relationship between the tracking angle error and the CCD angle-error measurement was studied in detail,as well as the compensation effect of tracking angle error based on the factors of angle-error measurement,signal to noise ratio,beam divergence angle,and so on.Considering the application requirements of the stability of different types of SOC links,an approach with optimizing configuration of tracking control parameters under condition of limited terminal resources,was further proposed and simulated,which improves the stability of tracking significantly.Considering the characteristics of narrow beacon SOC links,a series of in-orbit optimization methods of beam tracking were proposed,including the static/dynamic calibration in acquisition/tracking coordinate system,as well as the rapid switching method of detection between acquisition and tracking.By using static calibration method of acquisition/tracking coordinate system,the uncertainty of acquisition can be reduced effectively in the initial stage of optical communication link,and thus the in-orbit acquisition performance of narrow beacon laser link could be ensured;by using dynamic calibration method of acquisition/tracking coordinate system,the concentricity of receive beacon and signal light can be corrected in real time,and it would promote the performance of tracking and communication based on narrow beacon;by using the rapid switching method of detection between acquisition and tracking,the adaptive optimization threshold segmentation was proposed to improve the precision of threshold segmentation,and could detect the location of the beacon light in the acquisition stage quickly and accurately,which also could ensure a rapid switching from acquisition mode to tracking mode,to improve the overall performance of the SOC link system.Finally,the dissertation carried out the ground tests and in-orbit verification for the proprosed narrow beacon acquisition/tracking optimization methods,as well as the in-orbit optimization methods.Using indoor dynamic docking test equipments,the demonstration of narrow beacon acquisition and tracking optimization method has been carried out for verification;using ground external field point-to-point test system,the acquisition-and-tracking rapid switching method has been conducted;using the HY-2 LEO/Ground and SJ13 GEO/Ground in-orbit tests,the narrow beacon acquisition and tracking optimization method have been verified in-orbit,by combining with the techniques of in-orbit static coordinate calibration,dynamic coordinate calibration,and acquisition-and tracking rapid switching method,and so on,to achieve optimization of the overall performance of SOC link system.This dissertation has improved the optimization design and in-orbit optimization method of acquisition and tracking in the SOC link system,providing a reference for the optimization design of narrow beacon acquisition-tracking subsystem,which could potentially applied in SOC network and High-Speed/Real-Time SGIN in the future.