| The effects of the atmosphere on light propagating through it have received considerable attention from the astronomical and directed energy communities. As the airborne laser communications efforts capitalizes on this work care needs to be taken to refine this work to apply to the problem at hand. Often for other applications the problem is dominated by the atmosphere close to the earth’s surface. However, for air-air and air-space communications this portion of the atmosphere is not relevant, so care must be taken to insure that the understanding of the atmosphere at high altitudes is at a sufficient level of fidelity. Previously high fidelity was not needed at the higher altitudes since the lower altitude effects dominated the problem.
Another issue particular to airborne applications is that the airflow local to the aircraft, often called the boundary layer, can degrade the optical signal similar to the more conventional atmospheric turbulence. This field of aero-optics is relatively immature although of late it has been receiving more attention. Some of the challenges that remain include determining what types of flows are detrimental to airborne laser communications and what types of flows are benign environments. Such an understanding will help determine installation locations and drive system and sub-system designs if sub-optimal installation locations are required.
Finally, different applications require different performance measurements. Metrics that are appropriate for astronomical sensing or directed energy are not necessarily appropriate or sufficient to describe communications. In this paper a description of metrics for measuring the effect of the propagation media on laser communications are presented and potential mitigating technologies are discussed.
|