A Multi Stage Pointing Acquisition and Tracking (PAT) Control System Approach For Air to Air Laser Communications

摘要

Nearly half a century has passed since the laser was modulated, providing for the first time a means to send high speed information at distance over a beam of light. Simple in concept, this method of communication can provide data rates that far exceed communications by radio waves, however requiring an extremely accurate and stable line of sight (LOS) between the transmitting laser and light detector. Today engineers are faced with a much greater challenge as they seek to apply laser communications over hundreds of kilometers in the open atmosphere aboard aircraft in flight. Disturbing vibrations on the aircraft together with atmospheric scintillation introduces pointing and tracking errors in the LOS that can either degrade or entirely prohibit the ability to communicate by laser. This is where communications turns to control engineering for solutions. For relatively low power lasers with small divergence, mechanisms and their controls must be capable of pointing, and then tracking within a few microradians over a field of regard (FOR) that exceeds a full hemisphere. This presents a formidable problem for this disturbance environment.