Quantifying factors affecting optical turbulence propagation using a controlled towed vehicle from an aircraft

Abstract

High Energy Laser (HEL) systems are advantageous for their precision against small surface targets, lethality, and ability to deliver power. Yet their performances are impacted by atmospheric turbulence and aerosols. It is thus crucial to quantify such atmospheric effects to aid the optical system design and/or to predict their operational conditions. The main objective of this study is to quantify optical turbulence in the marine atmospheric boundary layer that impacts ship-based optical systems. I utilized measurements from the Coupled Air Sea Processes and Electromagnetic Ducting Research (CASPER) East field campaign. In particular, the Controlled Towed Vehicle (CTV) tethered to the CIRPAS Twin Otter research aircraft was analyzed for horizontal and vertical variabilities of the structure function parameter, Cn2, and the associated components of temperature, humidity, and the cross-correlation between the two. I identified the predominant contributions of temperature perturbations to Cn2 similar to that over land. The effects of water vapor are negligibly small. However, temperature and humidity correlations can contribute 20% of the total Cn2 in unstable conditions. In stable conditions, this term becomes consistently negative. The dependence of Cn2 on wind speed and thermal stability was illustrated using individual examples as well as all available data.