Enhanced, Fast-running Scaling Law Model of Thermal Blooming and Turbulence Effects on High Energy Laser Propagation

A new scaling law model is presented to rapidly simulate thermal blooming and turbulence effects on high energy laser propagation, producing results approaching the quality normally only available using wave-optics code, but at much faster speed. The model convolves irradiance patterns originating from two distinct scaling law models, one with a proficiency in thermal blooming effects and the other in turbulence. To underscore the power of the new model, results are verified for typical, realistic scenarios by direct comparison with wave optics simulation

Estimating Turbulence Distribution over a Heterogeneous Path Using Time‐lapse Imagery from Dual Cameras

Knowledge of turbulence distribution along an experimental path can help in effective turbulence compensation and mitigation. Although scintillometers are traditionally used to measure the strength of turbulence, they provide a path-integrated measurement and have limited operational ranges. A technique to profile turbulence using time-lapse imagery of a distant target from spatially separated cameras is presented here. The method uses the turbulence induced differential motion between pairs of point features on a target, sensed at a single camera and between cameras to extract turbulence distribution along the path. The method is successfully demonstrated on a 511 m almost horizontal path going over half concrete and half grass. An array of Light-Emitting Diodes (LEDs) of non-uniform separation is imaged by a pair of cameras, and the extracted turbulence profiles are validated against measurements from 3D sonic anemometers placed along the path. A short-range experiment with a heat source to create local turbulence spike gives good results as well. Because the method is phase-based, it does not suffer from saturation issues and can potentially be applied over long ranges. Although in the present work, a cooperative target has been used, the technique can be used with non-cooperative targets. Application of the technique to images collected over slant paths with elevated targets can aid in understanding the altitude dependence of turbulence in the surface layer

Re-Visiting Acoustic Sounding to Advance the Measurement of Optical Turbulence

Optical turbulence, as determined by the widely accepted practice of profiling the temperature structure constant, C2T, via the measurement of ambient atmospheric temperature gradients, can be found to differ quite significantly when characterizing such gradients via thermal-couple differential temperature sensors as compared to doing so with acoustic probes such as those commonly used in sonic anemometry. Similar inconsistencies are observed when comparing optical turbulence strength derived via C2T as compared to those through direct optical or imaging measurements of small fluctuations of the index of refraction of air (i.e., scintillation). These irregularities are especially apparent in stable atmospheric layers and during diurnal quiescent periods. Our research demonstrates that when care is taken to properly remove large-scale index of refraction gradients, the sonic anemometer-derived velocity structure constant, C2v, coupled with the similarly derived turbulence-driven index of refraction and vertical wind shear gradients, provides a refractive index structure constant, C2n, that can more closely match the optical turbulence strengths inferred by more direct means such as scintillometers or differential image motion techniques. The research also illustrates the utility and robustness of quantifying Cn2 from C2T at a point using a single sonic anemometer and establishes a clear set of equations to calculate volumetric C2n data using instrumentation that measures wind velocities with more spatial/temporal fidelity than temperature

Understanding Newborn Behavior and Early Relationships: The Newborn Behavior Observations (NBO) System Handbook

Giving infants a voice helps parents understand their baby\u27s unique strengths and needs. This observational tool and handbook gives clinicians a systematic way to help parents respond with confidence to their newborn\u27s individual needs--and build a positive parent-professional relationship in the process. Flexible, easy to integrate into everyday practice, and based on more than 25 years of research and clinical experience, this system includes a short, easy-to-use, interactive observational tool. With the Newborn Behavioral Observations (NBO) system, clinicians will have a structured set of 18 observations for infants from birth to approximately 3 months of age. Including parents as partners, professionals guide the observation, discuss the infant\u27s abilities and behaviors with the parents, encourage parents\u27 insights and questions, and suggest specific ways to support the child\u27s development. This book also provides a complete guide to the NBO, including realistic case studies, step-by-step how-to instructions, and color photos illustrating each NBO item. More than a tool, this handbook helps clinicians improve their daily work by providing in-depth information on infant development, cultural competence, premature and at-risk infants, family-centered care, and more

Implications of Four-dimensional Weather Cubes for Improved Cloud-free Line-of-sight Assessments of Free-space Optical Communications Link Performance

We advance the benefits of previously reported four-dimensional (4-D) weather cubes toward the creation of high-fidelity cloud-free line-of-sight (CFLOS) beam propagation for realistic assessment of autotracked/dynamically routed free-space optical (FSO) communication datalink concepts. The weather cubes accrue parameterization of optical effects and custom atmospheric resolution through implementation of numerical weather prediction data in the Laser Environmental Effects Definition and Reference atmospheric characterization and radiative transfer code. 4-D weather cube analyses have recently been expanded to accurately assess system performance (probabilistic climatologies and performance forecasts) at any wavelength/frequency or spectral band in the absence of field tests and employment data. The 4-D weather cubes initialize an engineering propagation code; which provides the basis for comparative percentile performance binning of FSO communication bit error rates (BERs) as a function of wide-ranging azimuth/elevation; earth-to-space uplinks. The aggregated; comparative BER binning analyzes for different regions; times of day; and seasons applying a full year of 4-D weather cubes data provided numerous occasions of clouds; fogs; and precipitation events. The analysis demonstrated the utility of 4-D weather cubes for adroit management of CFLOS opportunities to enhance performance analyses of point-to-point as well as evolving multilayer wireless network concepts