Ground Test And Verification Of Pointing,acquisition And Tracking System For Space Optical Communication

The high-performance pointing,acquisition,and tracking(PAT)system is one of the key technologies for space laser communication.To ensure the stability and reliability for the space optical communication,direct and comprehensive ground testing of the PAT system is indispensable.The ground short-distance test method of the PAT system is studied and the main contents and results are as follows:First,the influence of the beam pointing error on the receiving power of the terminal was analyzed.Based on the overall structure of the PAT system,the operation principle of each part and the method of device selection were discussed.The working flow and state switching of the laser link established by the PAT system on both sides of communication were analyzed.Secondly,to meet the challenge of the whole process equivalent test for the acquisition,pointing,and tracking system of space optical communication terminals,a novel plan is proposed to test the PAT directly and fully on the ground with short distance.The communication terminals are transformed to a virtual point under the condition of short distance by establishing an imaging relationship between the emergent light spot in the transmitter and the detecting plane in the receiver.The acquisition process of seeking the small-size antenna in the receiver with a large coverage scanning beam in the transmitter is replaced by seeking a large receiver surface with a narrow laser beam.This point-seeking-surface method can be equivalent to the surface-seeking-point method in the actual space communication.This method solves the problems during ground test,such as being not applicable to see the terminal as the point and the small spot size.Thirdly,two terminals spaced 5 meters apart were employed to construct the short-distance verification platform,with which the PAT function verification and performance test were completed.The experimental results verify that the proposed experimental platform can simulate the acquisition and tracking process.The laser link can be automatically established between the two terminals in the acquisition phase,and then stable tracking can be carried out to achieve viable data transmission.In the tracking phase,the Kalman filter algorithm is used to compensate the lag of system response,and the precision tracking pointing error is kept in the range of-20?20 ?rad.