Coarse tracking technology of secondary imaging Coude-type laser communication terminal

When the Coude-type laser communication terminal coarse tracking detector receives the beacon light in a large field of view, it needs to pass through the telephoto unit, a plurality of Coude mirrors, a beam splitter, and a thick tracking lens group, so the long beacon light transmission path results in a significant increase in the optical aperture of following sub-optical path coarse tracking branch. At the time of capture, telescopic units and Coude mirrors have relative motion with the coarse tracking detectors, there are many beacon light transmission links and the tracking model is complex. To solve these two problems, first, three kinds of traditional Coude light paths are compared, the secondary imaging Coude optical path is selected and designed to reduce the optical aperture of the subsequent sub-optical path, which is conducive to the subsequent light and miniaturization design of the sub-beam path. Subsequently, the tracking model of the secondary imaging Coude-type laser communication terminal is deduced, the tracking model is established by the mirror matrix and coordinate transformation, and the tracking model is simulated by Matlab-Simulink; finally, through the ground test, the tracking performance of the terminal is evaluated. The maximum target miss distance of azimuth tracking is 84.65 μrad(3σ), and the maximum target miss distance of pitch tracking is 56.33 μrad(3σ), which satisfies the communication requirements of 150 μrad(3σ). The secondary imaging Coude-type structure and tracking model meet the requirements of coarse tracking acquisition and tracking of inter-satellite laser communication.