Wide-range Fine Pointing Mechanism for optical inter-satellite communications

A WFPM (Wide-range Fine Pointing Mechanism) composed of electromagnetic actuators and flexible support system has been developed for optical inter-satellite communications. The actuators, which consist of four moving-coil-type motors with long strokes, ensure a wide scan range. The support system, which consists of a metal center pivot and four thin springs, allows a mirror to be rotated freely about a vertically constant point; the mirror can be rotated about the X- and Y- axes simultaneously. A digital control system with gap sensor feedback has been designed to drive the WFPM. This system features a two-degrees-of-freedom robust controller that incorporates a disturbance cancellation algorithm to cut off low-frequency vibrations from the satellite body for highly precise tracking. Use of the WFPM by the acquisition and tracking terminal significantly shortens acquisition time and ensures accurate tracking. Acquisition and tracking tests show fast acquisition time (104ms) and high tracking precision (two micro-radians). The WFPM has the potential to play an essential role in helping to produce high-speed inter-satellite communications and broadband communications networks in outer space.