Monte-Carlo simulations featuring Kolmogorov phase screens have long been used in understanding both the effects of atmospheric turbulence on imaging and the performance of turbulence mitigation methods. We have developed a new, high fidelity, non-Kolmogorov phase screen model that allows the orientation of anisotropy to vary arbitrarily. Our model is used to generate simulated video sequences ...

The wavefront aberrations induced by atmospheric turbulence can severely degrade the performance of an optical imaging system Adaptive optics refers to the process of removing unwanted wave front distortions with the use of a phase corrector before the image is formed The basic idea in adaptive optics is to control the position of the surface of a deformable mirror in such a way as to approxima...

In this paper we analyze the beam combining and atmospheric propagation of high-power lasers for directed-energy (DE) applications. The large linewidths inherent in high-power fiber, and to a lesser extent, slab lasers cause random phase and intensity fluctuations occurring on subnanosecond time scales. To coherently combine these high-power lasers would involve instruments capable of precise p...

It is impossible to measure, simulate, predict, and understand the earth’s atmosphere without taking into account its turbulent nature. When simulating the macrostructure of atmospheric flows, because of practical limitations, there is no way to simultaneously and explicitly simulate small-scale turbulence or even microphysical processes. Yet, the small scales can significantly impact the large...

The angular resolution of an astronomical telescope is often limited primarily by atmospheric turbulence, and this resolution limitation is conventionally referred to as atmospheric seeing. A systematic study of the wavelength dependence of this effect was conducted using the 1.5 m McMath solar telescope of Kitt Peak National Observatory, and this study is reported here. Telescope resolution wa...

The structure constant of the atmospheric refractive index is used for characterizing the turbulence strength and for predicting the scintillation of electromagnetic waves in atmosphere. It is measured continuously in Prague using an optical scintillometer. First monthly and seasonal statistics obtained from the data gathered in the summer 2011 are provided. Lognormal distribution parameters ar...

Practical autonomous aerial refueling between unmanned tanker and receiver aircraft using the probe-anddrogue method requires a reliable relative position sensor integrated with a robust relative navigation and control algorithm. The system must provide successful docking in the presence of disturbances caused by both the tanker wake vortex and atmospheric turbulence. This paper develops a refe...

The NTU/ Purdue nonhydrostatic numerical model has been developed over the last 6 years to predict atmospheric motions and conditions for both the mesoscale (200 m to 200 km) and large scale turbulence scale (20 m to 200 m). It is a fully explicit, compressible three-dimensional code and has compared quite to a wide variety of known analytical solution or observed situations including the Bould...

A Multi-channel free-space optical (FSO) communications system based on orbital angular momentum (OAM)-carrying beams is studied. We numerically analyze the effects of atmospheric turbulence on the system and find that turbulence induces attenuation and crosstalk among channels. Based on a model in which the constituent channels are binary symmetric and crosstalk is a Gaussian noise source, we ...

In this study, the authors theoretically study the performance of direct-detection free-space optical communication systems using binary phase-shift keying subcarrier-intensity modulation and avalanche photodiode (APD). The system biterror rate and channel capacity are theoretically derived in cases of log-normal and gamma-gamma channel models for weakto-moderate and moderate-to-strong atmosphe...