Acquisition, pointing, and tracking architecture for laser communication

Art for capture of the terminal in the laser communications system of free space, and pursuit, It includes that capture ひいて pursues a terminal so that it may be acted as Stare of the data laser beam which exchanged the beacon laser beam between terminals and were exchanged with the terminal based on the feedback from detection of a beacon laser beam. The beacon laser beam used for capture has a bigger spread than the beacon laser beam used for pursuit. A gimbal provides the rough steering of a data laser beam, and a steering mirror provides a precise steering. The GPS position data exchanged via RF link may be used for directions in early stages of a beacon laser beam for capture. A chop is carried out and a beacon laser beam is distinguished with different chopping frequency so that the beacon wavelength with all the same terminals can be used.