Design of optical antenna for space optical communications and coarse pointing error analysis

Compared to current radio-frequency technology, Free-Space Optical (FSO) communication holds tremendous advantages, such as higher data rates, high security, light weight, smaller size, and less power. FSO communication has attracted considerable attention for space activities. Optical antenna and Acquisition, Pointing and Tracking (APT) system are crucial technologies of FSO communication. The tasks of optical antenna include narrowing the diverging angle of transmitted beam, assure the wavefront quality of beam transmitted and received, and improve angular resolution for fine pointing. For a Chinese space mission, a 4-mirror off-axis optical system coupled with Coude path is designed. The telescope is mounted on a 2-axis gimbal mechanism to implement coarse pointing. The optical terminals were launched in 2018. The ground-to-satellite and inter-satellite bi-directional communication demonstrations are carried out successfully. The performance of the optical terminal satisfies all requirements of the mission.