Design and early development of a UAV terminal and a ground station for laser communications

TL;DR

This paper presents the design and initial development of a laser communication system for UAVs, featuring a MEMS retroreflector terminal and a ground station with advanced tracking and power management.

Contribution

It introduces a novel MEMS-based retroreflector terminal for UAV laser communication and a ground station with GPS-aided tracking and polarization-based optical path management.

Findings

Successful conceptual design of UAV laser communication terminal.

Implementation of a real-time UAV position determination system.

Development of an adaptive laser power control method.

Abstract

A free-space laser communication system has been designed and partially developed as an alternative to standard RF links from UAV to ground stations. This project belongs to the SINTONIA program (acronym in Spanish for low environmental-impact unmanned systems), led by BR&TE (Boeing Research and Technology Europe) with the purpose of boosting Spanish UAV technology. A MEMS-based modulating retroreflector has been proposed as a communication terminal onboard the UAV, allowing both the laser transmitter and the acquisition, tracking and pointing subsystems to be eliminated. This results in an important reduction of power, size and weight, moving the burden to the ground station. In the ground station, the ATP subsystem is based on a GPS-aided two-axis gimbal for tracking and coarse pointing, and a fast steering mirror for fine pointing. A beacon-based system has been designed, taking advantage of the retroreflector optical principle, in order to determine the position of the UAV in real-time. The system manages the laser power in an optimal way, based on a distance-dependent beam-divergence control and by creating two different optical paths within the same physical path using different states of polarization.