Optical-path design and study of fine tracking assembly in space optical communication

An effective means for achieving high tracking accuracy is utilization of coarse and fine compound-axis structure in space laser communication. Firstly, this paper makes an optimization design of whole optical-path structure. Secondly, for enhancing energy density of beacon to make CCD work with high frame rate in the process of fine tracking, a technique is put forward, which uses a single beacon to switch between both different divergence angles. Thirdly, this paper designs an image processing unit of FTA (fine tracking assembly) based on FPGA, which adopts a sub-pixel subdivision technology. Finally, test results indicate that the tracking accuracy can be up to 1.2μrad in one time variance when pixel resolution is 3μrad, which meets the pointing accuracy requirement of space laser communications.