Modeling of the lower atmosphere to facilitate improved laser propagation
Abstract
Modeling of the lower atmosphere to facilitate improved laser propagationabstract:The principal objective of this proposed projec"t is to develop an accurate Cn2 profilemodel in the atmosphere next to the ground as a function of altitude, h, that will properly"characterize the lower atmospheric turbulence relevant to laser beam propagation in weakturbulence conditions as well as in deep tu"rbulence~in particular, to High Energy Laser (HEL)propagation. To do so will require an extensive set of measurements from various" platforms toacquire data at various altitudes that can be used to achieve this first objective. A secondaryeffort in this regard is to develop inner scale (l0) and outer scale (L0) of turbulence models thatalso change as a function of altitude. To properly ch"aracterize atmospheric turbulence for laserbeam propagation applications it is known that all three parameters, Cn2, l0, and L0, ar"e necessaryto describe various statistical characteristics imposed by the turbulence on the laser beam. Theconventional Cn2 profil"e model, called the HV-5/7 model, characterizes Cn2 in the loweratmosphere by a decaying exponential function but it does not compa""re well with experimentaldata at heights below 1 km. The more recently developed HAP Cn2 profile model, whichdescribes Cn2 in the"" lower atmosphere by a power-law function, has been shown to provide amuch better fit with available experimental data. Early versi"ons of the power-law model used anh-4/3 behavior for daytime characterization of increasing altitude and h-2/3 behavior for nightti"me.However, taking the temporal hour of the day into account for determining the proper transitionof the power-law coefficient bet"ween daytime and nighttime conditions is crucial for propercharacterization of the lower atmosphere. Refining this variable power-law is another objectiveof this research effort.The approach we propose is to develop physics-based models of the optical turbulenc"e,develop second-order and fourth-order statistical models for the effects on the propagating laserbeam and conduct validation mea"surements over instrumented extended ranges featuring strongoptical turbulence conditions. The project brings to bear an extended set of characterizationinstruments that are available and can be used on our test ranges at the Kennedy Space Center(KSC) and elsew"here. These test ranges provide us with a variety of ground conditions such asgrass, concrete, and also maritime environments, with" distances up to 5 Km.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 20, 2017
- Source ID
- N000141812054
Entities
People
- Robert Crabbs
Organizations
- Office of Naval Research
- United States Navy
- University of Central Florida Board of Trustees