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Articles 31 - 46 of 46
Full-Text Articles in Optics
Temperatures In The Mid-Latitude Mesosphere During Sudden Stratospheric Warmings As Determined From Rayleigh Lidar Data, Leda Sox, Vincent B. Wickwar, Chad Fish, Joshua P. Herron
Temperatures In The Mid-Latitude Mesosphere During Sudden Stratospheric Warmings As Determined From Rayleigh Lidar Data, Leda Sox, Vincent B. Wickwar, Chad Fish, Joshua P. Herron
Graduate Student Posters
Sudden Stratospheric Warmings (SSWs) are major disturbances in the polar region of the winter hemisphere that cause major changes in stratospheric temperature and circulation. SSWs are characterized by a temperature increase of tens of degrees Kelvin, averaged over 60°-90° latitude, and a weakening of the polar vortex that persists for the order of a week at the 10 hPa level (roughly 32 km) [Labitzke and Naujokat, 2000]. The polar vortices are cyclones centered on both of the Earth’s poles that are present from the mid-troposphere to the lower stratosphere. Eastward zonal winds define the strong polar vortices in the winter. …
Ground-Based Observations With A Rayleigh-Mie-Raman Lidar From 15-120 Km, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, David L. Barton, Matthew T. Emerick
Ground-Based Observations With A Rayleigh-Mie-Raman Lidar From 15-120 Km, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, David L. Barton, Matthew T. Emerick
Graduate Student Posters
Rayleigh lidar systems have historically made ground-based observations of the upper atmosphere (stratosphere and mesosphere) from 35-90 km. This technology has helped fill the data collection gap between the troposphere and space. Recently our Rayleigh lidar group at the Atmospheric Lidar Observatory on the campus of Utah State University (42° N, 112° W) upgraded the original lidar system in order to extend the measurement range for neutral densities and temperatures to higher altitudes and has increased the upper limit, so far, from 90 to 110 km. Next, we will extend the lower altitude limit downward to 15 km. This will …
Design, Development, And In-Flight Testing Of A Pointer/Tracker For In-Flight Experiments To Measure Aero-Optical Effects Over A Scaled Turret, Matthew J. Krizo, Salvatore J. Cusumano, Steven T. Fiorino, Ryan Heap, Victor Velten, Joshua Brown, Richard J. Bartell
Design, Development, And In-Flight Testing Of A Pointer/Tracker For In-Flight Experiments To Measure Aero-Optical Effects Over A Scaled Turret, Matthew J. Krizo, Salvatore J. Cusumano, Steven T. Fiorino, Ryan Heap, Victor Velten, Joshua Brown, Richard J. Bartell
Faculty Publications
We address the design, development, and testing of a pointer/tracker as a probe beam for the purpose of making high-speed, aero-optical measurements of the flow over a scaled beam director turret. The tracker uses retro-reflection of the probe beam off of a Reflexite annulus surrounding the turret. The constraints of the design required a near-total-commercial off the shelf system that could be quickly installed and removed in a rented aircraft. Baseline measurements of environmental vibrations are used to predict pointing performance; mitigation of line-of-sight jitter on the probe beam is achieved through passive isolation and the design of relay optics. …
Upgraded Alo Rayleigh Lidar System And Its Improved Gravity Wave Measurements, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham
Upgraded Alo Rayleigh Lidar System And Its Improved Gravity Wave Measurements, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham
Graduate Student Posters
The Rayleigh-Scatter lidar system at the Atmospheric Lidar Observatory (ALO) on the Utah State campus is currently going through a series of upgrades to significantly improve its observational abilities. A specific objective of these upgrades is to expand the altitude range over which backscattered photons can be collected. A second objective is to increase the sensitivity of the instrument to be able to analyze the raw data at finer temporal and/or spatial resolutions. By measuring relative densities, the system will be able to produce absolute temperatures and relative density perturbations, which illustrate gravity wave structures. Gravity wave studies will significantly …
Implementation Of Branch-Point-Tolerant Wavefront Reconstructor For Strong Turbulence Compensation, Michael J. Steinbock
Implementation Of Branch-Point-Tolerant Wavefront Reconstructor For Strong Turbulence Compensation, Michael J. Steinbock
Theses and Dissertations
Branch points arise in optical transmissions due to strong atmospheric turbulence, long propagation paths, or a combination of both. Unfortunately, these conditions are very often present in desired operational scenarios for laser weapon systems, optical communication, and covert imaging, which suffer greatly when traditional adaptive optics systems either cannot sense branch points or implement non-optimal methods for sensing and correcting branch points. Previous research by Pellizzari presented a thorough analysis of various novel branch point tolerant reconstructors in the absence of noise. In this research a realistic model of the Air Force Institute of Technology's adaptive optics system is developed …
Observations With The Most Sensitive Rayleigh-Scatter Lidar, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham
Observations With The Most Sensitive Rayleigh-Scatter Lidar, Leda Sox, Vincent B. Wickwar, Joshua P. Herron, Marcus J. Bingham
Graduate Student Posters
The mesosphere is the most unexplored region of the atmosphere. Its altitude range of 50-85 km lies in between the reaches of data collecting instruments like weather balloons and satellites. For this reason, remote sensing systems, such as lidar, which are able to employ ground-based instruments to make extensive measurements in this difficult to detect region. The Rayleigh-scatter lidar at USU is currently being redeveloped to be the most powerful and sensitive of its kind. This type of lidar exploits light and particle interactions, like those that account for the blue color of the sky, to make relative density and …
Characterization Of Pollen Particles Using Lidar, Leda Sox
Characterization Of Pollen Particles Using Lidar, Leda Sox
Graduate Student Posters
We have observed pollen in the local troposphere using the depolarization capabilities of a LIDAR (Light Detection and Ranging) system. The polarization characteristics of the received LIDAR signal, along with supplemental pollen forecast data, allowed me to characterize the shape of the pollen particles.
A Computational Tool For Evaluating Thz Imaging Performance In Brownout Conditions At Land Sites Throughout The World, Seth L. Marek
A Computational Tool For Evaluating Thz Imaging Performance In Brownout Conditions At Land Sites Throughout The World, Seth L. Marek
Theses and Dissertations
This study quantifies terahertz (THz) or sub-millimeter imaging performance during simulated rotary-wing brownout or whiteout environments based on geographic location and recent/current atmospheric weather conditions. The atmospheric conditions are defined through the Air Force Institute of Technology Center for Directed Energy (AFIT/CDE) Laser Environmental Effects Definition and Reference or LEEDR model. This model enables the creation of vertical profiles of temperature, pressure, water vapor content, optical turbulence, and atmospheric particulates and hydrometeors as they relate to line-by-line layer extinction coefficient magnitude at wavelengths from the UV to the RF. Optical properties and realistic particle size distributions for the brownout and …
Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema
Closed-Loop Adaptive Optics Control In Strong Atmospheric Turbulence, Todd M. Venema
Theses and Dissertations
A self-referencing interferometer based closed-loop adaptive optics controller is developed which is designed to operate effectively under strong turbulence conditions. The aberrated optical field is modeled stochastically and then estimates of the state of the system are developed using a steady-state, fixed-gain Kalman filter. The phase of the optical field is considered the state of the system which is wrapped in a limited range of (-π, π]. This phase is unwrapped through the use of a least-squares reconstructor which has been modified to work effectively in the presence of branch points associated with strong turbulence. The conjugate of the optical …
Limitations Of Segmented Wavefront Control Devices In Emulating Optical Turbulence, Michael D. Plourde
Limitations Of Segmented Wavefront Control Devices In Emulating Optical Turbulence, Michael D. Plourde
Theses and Dissertations
Using a device to act as a surrogate for atmospheric turbulence in a laboratory is necessary to build and test optical systems for imaging, lidar, laser weapons, and laser communications. Liquid-crystal spatial light modulators (LC SLMs) and segmented micro-electro-mechanical-system (MEMS) deformable mirrors (DMs) are commonly used devices for altering wavefronts in order to simulate a portion of atmospheric turbulence. The best location of these devices was theoretically analyzed to obtain the broadest possible range of atmospheric conditions. It was found that two phase screens should be placed at the beginning of the optical path to achieve maximum turbulence strength for …
Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch
Coherent Differential Absorption Lidar For Combined Measurement Of Wind And Trace Atmospheric Gases, Grady James Koch
Electrical & Computer Engineering Theses & Dissertations
A lidar system was developed for making combined range-resolved measurements of wind speed and direction, water vapor concentration, and carbon dioxide concentration in the atmosphere. This lidar combines the coherent Doppler technique for wind detection and the differential absorption lidar (DIAL) technique to provide a multifunctional capability. DIAL and coherent lidars have traditionally been thought of and implemented as separate instruments, but the research reported here has shown a demonstration of combining the coherent and DIAL techniques into a single instrument using solid-state lasers. The lasers used are of Ho:Tm:YLF, which operates at a wavelength of 2 μm. This wavelength …
Regression Analysis Of Radar Measured Optical Turbulence With Synoptic Scale Meteorological Variables, Diana L. Hajek
Regression Analysis Of Radar Measured Optical Turbulence With Synoptic Scale Meteorological Variables, Diana L. Hajek
Theses and Dissertations
A key issue to the USAF's Airborne Laser (ABL) program is the ability to accurately predict the level of optical turbulence that the ABL will encounter at its flight levels. The optical turbulence must be characterized so that the range and range variation of the ABL can be determined. Gravity wave spectra resulting from frontal or jet stream passage are presumed to cause layers of optical turbulence; however, exact relationships between optical turbulence and synoptic scale meteorological phenomena are unclear. This study assesses the statistical relationship between optical turbulence and synoptic scale variables through multiple linear regression. The optical turbulence …
Deconvolution From Wavefront Sensing Using Optimal Wavefront Estimators, Scott R. Maethner
Deconvolution From Wavefront Sensing Using Optimal Wavefront Estimators, Scott R. Maethner
Theses and Dissertations
A cost effective method to improve the space surveillance mission performance of United States Air Force (USAF) ground-based telescopes is investigated and improved. A minimum variance wavefront estimation technique is used to improve Deconvolution from Wavefront Sensing (DWFS), a method to mitigate the effects of atmospheric turbulence on imaging systems that does not require expensive adaptive optics. Both least-squares and minimum variance wavefront phase estimation techniques are investigated, using both Gaussian and Zernike polynomial elementary functions. Imaging simulations and established performance metrics are used to evaluate these wavefront estimation techniques for a one-meter optical telescope. Performance metrics include the average …
Characterization Of Atmospheric Turbulence Over Long Horizontal Paths Using Optical Slope Measurements, Eric E. Silbaugh
Characterization Of Atmospheric Turbulence Over Long Horizontal Paths Using Optical Slope Measurements, Eric E. Silbaugh
Theses and Dissertations
Atmospheric turbulence has long been recognized as one of the fundamental factors affecting optical systems operating through the atmosphere. Turbulence over vertical paths has been well characterized, both theoretically and experimentally. Much less is known about turbulence over long, horizontal paths. Perturbations of the wave front phase can be measured using a Hartmann wave front sensor (H-WFS). Theoretical expressions for the tilt removed structure function of the H-WFS slope measurements were derived and evaluated using quadrature. These slope structure functions are functions of the phase structure function. The Kolmogorov turbulence model was assumed. Simulated H-WFS slope measurements were generated using …
Performance Impacts For Actuator Misalignments And Failures In Large- Aperture Adaptive-Optic Telescopes, Timothy D. Hogan
Performance Impacts For Actuator Misalignments And Failures In Large- Aperture Adaptive-Optic Telescopes, Timothy D. Hogan
Theses and Dissertations
Large-aperture telescopes require adaptive optics in order to compensate for atmospheric turbulence which would otherwise negate the resolution advantages of using large apertures. This investigation analyzes the impacts of misalignments and failures, in the deformable mirror actuators, upon the performance of such systems. A numerical simulation of a standard adaptive optics system is used to generate characteristic optical transfer function OTF and signal-to-noise ratio SNR performance metrics. The performance impacts of the misalignments are shown to be dependent upon the Fried parameter effective telescope diameter, the source object brightness, and the control system time delay. The degree of performance degradation …
Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee
Characterization Of Laboratory Generated Turbulence By Optical Phase Measurements, Eric P. Magee
Theses and Dissertations
The resolution achieved by an optical imaging system in the presence of the random effects of the atmosphere is severely degraded from the theoretical diffraction limit. Techniques exist for recovering near diffraction limited performance of an imaging system in the presence of atmospheric turbulence. As opposed to laboratory testing, testing image enhancement techniques in the Earth's atmosphere imposes many limitations. Unfavorable weather conditions could result in the loss of time and money invested in conducting the experiments. With a properly characterized turbulence generator, with statistics that match those of the atmosphere, experimental testing of image enhancement techniques can be conducted …