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Air Force Institute of Technology

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Electro-Hydrostatic Actuator Controller Design Using Quantitative Feedback Theory, Ki Ho Kang Dec 1994

Electro-Hydrostatic Actuator Controller Design Using Quantitative Feedback Theory, Ki Ho Kang

Theses and Dissertations

The Electro-Hydrostatic Actuator (EllA) technology offers a higher degree of combat survivability and easier maintainability of the aircraft flight control system, because all the components necessary to operate the actuator are collocated with the actuator. Quantitative Feedback Theory (QFT) is used to design a control system for the EHA. The impact of parameter variations, sensor noise, and flight conditions are explicitly considered in the design process. The solution utilizes a two loop QFT feedback structure. The inner loop structure stabilizes the motor's angular velocity and decreases the outer loop's uncertainty. The outer loop structure controls the RAM piston's position to …

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Head Related Transfer Function Approximation Using Neural Networks, John K. Millhouse Dec 1994

Head Related Transfer Function Approximation Using Neural Networks, John K. Millhouse

Theses and Dissertations

This thesis determines whether an artificial neural network (ANN) can approximate the Armstrong Aerospace Medical Research Laboratories (AAMRL) head related transfer functions (HRTF) data obtained from research at AAMRL during the fall of 1988. The first test determines whether HRTF lends any support in sound localization when compared to no HRTF (Interaural Time Delay only). There is a statistically significant interaction between the location of the sound and whether the HRTF or no HRTF is used. When this interaction is removed using the alternate F.Value, the statistics give the result of equal means for the filters and azimuth. This means …

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Adaptive Beamforming In Frequency-Dispersive Multipath Environments, David A. Murray Dec 1994

Adaptive Beamforming In Frequency-Dispersive Multipath Environments, David A. Murray

Theses and Dissertations

It is well known that an antenna array with N degrees of freedom (DOF) can cancel N - 1 interferers if they approach the array from directions other than that of the desired signal. It has been shown that there are cases in which it is possible for an array with N DOF to effectively cancel more than N - 1 interferers. Specifically, we show how this can be done when there is incident upon an N-element array not only the desired signal and a jammer signal, but more than N - 1 Doppler-shifted multipath copies of the jammer signal …

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A Quantitative Feedback Theory Fcs Design For The Subsonic Envelope Of The Vista F-16 Including Configuration Variation, Scott N. Phillips Dec 1994

A Quantitative Feedback Theory Fcs Design For The Subsonic Envelope Of The Vista F-16 Including Configuration Variation, Scott N. Phillips

Theses and Dissertations

An aircraft's response to control inputs varies widely throughout its flight envelope. The aircraft configuration also impacts control response through variations in center of gravity and moments of inertia. Designing a flight control system (FCS) to accommodate the full flight envelope and configuration set of an aircraft is clearly a complex undertaking. Quantitative feedback theory (QFT) is a design tool which enables the engineer to attack this task in an efficient way. Although QFT is a robust control design technique, it is an interactive algorithm allowing the engineer full control over compensator order and gain. In this research effort, a …

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Silicon Based Microactuators For Telerobotic Tactile Stimulation, Britton C. Read Iii Dec 1994

Silicon Based Microactuators For Telerobotic Tactile Stimulation, Britton C. Read Iii

Theses and Dissertations

Silicon based microelectromechanical (MEM) devices using both surface and bulk micromachining have been realized to provide tactile stimulation. The bulk MEM devices utilize the bimorph principle and are fabricated in a complementary metal oxide semiconductor (CMOS) process through MOS implementation system (MOSIS). The surface MEM devices utilize the electrostatic principle and are fabricated in a complementary metal oxide semiconductor (CMOS) process through MOS implementation system (MOSIS). The surface MEM devices utilize the electrostatic principle and are fabricated in the multi-user MEM process (MUMPS) through MCNC. Eleven major designs are presented and tested to determine if they are suitable to provide …

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Experimental Definition For Implantation Of The Afit Cortical Multielectrode Array, Adam G. Spenik Dec 1994

Experimental Definition For Implantation Of The Afit Cortical Multielectrode Array, Adam G. Spenik

Theses and Dissertations

A two-dimensional multiplexed array of 256 electrodes (16 x 16) has been fabricated using conventional CMOS fabrication techniques. The size and spacing of the electrodes (160 x 160 µm squares with center-to-center spacing of 250 µm) approximate that of the cortical columns. The device is mounted on a small biocompatible package and a protocol to implant this package on the visual cortex of a ferret and a Rhesus monkey was developed and approved. An instrumentation setup to record the data from the device is described as well as the methods used to demultiplex the data. Testing of the device in …

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Processing Of Wide-Angle Synthetic Aperture Radar Signals For Detection Of Obscured Ground Targets, Richard J. Sumner Dec 1994

Processing Of Wide-Angle Synthetic Aperture Radar Signals For Detection Of Obscured Ground Targets, Richard J. Sumner

Theses and Dissertations

This thesis investigates advanced processing techniques for the detection of radar targets in the presence of clutter. It is assumed that the radar data available consist of multi-aspect angle, fully polarimetric Synthetic Aperture Radar (SAR) images. Various techniques are introduced and tested on available SAR data. These techniques attempt to exploit the multi-aspect angles in order to extract target characteristics not available in any single image. SAR images are manipulated in such a way to decrease the probability of false alarms in the target detection process. Target detection performance of the techniques is presented and compared. The techniques are shown …

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Compensated Deconvolution From Wavefront Sensing, Lori A. Thorson Dec 1994

Compensated Deconvolution From Wavefront Sensing, Lori A. Thorson

Theses and Dissertations

The U.S. Air Force has a continuing mission to obtain imagery of earth-orbiting objects. One of the means for obtaining this imagery is through the use of ground-based observatories. A fundamental problem associated with imaging objects through the atmosphere is that atmospheric turbulence inflicts a large, random aberration on the telescope which effectively limits the realizable resolution to that of a much smaller telescope. Several approaches have been taken to overcome these effects including pure post processing, pure adaptive optics, and hybrid techniques involving both adaptive optics and image post processing. One key result from past approaches is that partially …

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Advanced Formation Flight Control, Michael J. Veth Dec 1994

Advanced Formation Flight Control, Michael J. Veth

Theses and Dissertations

In this thesis, the formation flight control problem is continued from four previous theses. Automatic formation flight involves controlling multiple aircraft equipped with standard Mach-hold, altitude hold, and heading-hold autopilots to maintain a desired distance from a lead aircraft or "rabbit". Changes in the rabbit's states are treated as disturbances to the system and rejected. Previous research is advanced in the following areas: Higher-order aircraft-autopilot models are included into the design and a new feedback control law is employed, resulting in more accurate simulations. An energy tracking scheme is developed and is shown to reduce wing aircraft energy excursions. Finally, …

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Polarization Sensitivity Of Monopulse Radar Boresight Error Induced By Large, Ogive Radomes, Kelce S. Wilson Dec 1994

Polarization Sensitivity Of Monopulse Radar Boresight Error Induced By Large, Ogive Radomes, Kelce S. Wilson

Theses and Dissertations

The dependence of Boresight Error (BSE) on incident Electric Field (E-Field) polarization tilt angle is investigated. BSE, defined as the angular difference between a target's actual and radar-indicated position, is influenced by the radome used to protect the antenna. A - reliable computer model for predicting the BSE of electrically large radar-radome systems has been demonstrated and used to investigate the dependence of radome-induced BSE for various combinations of scan angle, element polarization, and incident E-Field polarization. The analysis includes a development of a transmission-depolarization model to justify the results of the computer model. Results compare very well with empirical, …

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Perceptual Based Image Fusion With Applications To Hyperspectral Image Data, Terry A. Wilson Dec 1994

Perceptual Based Image Fusion With Applications To Hyperspectral Image Data, Terry A. Wilson

Theses and Dissertations

Development of new imaging sensors has created a need for image processing techniques that can fuse images from different sensors or multiple images produced by the same sensor. The methods presented here focus on combining image data from the Airborne Visual and Infrared Imaging Spectrometer (AVIRIS) hyperspectral sensor into a single or smaller subset of images while maintaining the visual information necessary for human analysis. Three hierarchical multi-resolution image fusion techniques are implemented and tested using the AVIRIS image data and test images that contain various levels of correlated or uncorrelated noise. Two of the algorithms are published fusion methods …

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Reduction Of Off-Boresight Fields For A Tem Horn Antenna, Dennis J. Wolstenholme Dec 1994

Reduction Of Off-Boresight Fields For A Tem Horn Antenna, Dennis J. Wolstenholme

Theses and Dissertations

This research involves the design, modeling, and testing of both tapered periodic surfaces (TPS) and transverse electromagnetic (TEM) horns. The goal is to reduce the off-boresight fields for a TEM horn and increase the peak-to-peak field levels on boresight. This is accomplished by applying a TPS to the free space end. Two tapers are designed - one that approximates an exponential impedance function and one that approximates a triangular impedance function. Both reduce the off-boresight fields of the TEM horn. In most cases the exponential taper reduces the field levels further than the triangular taper. This research shows that a …

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Improving The Performance Of Spiral Antennas By Using Passive Scatterers, Joseph S. Zaren Dec 1994

Improving The Performance Of Spiral Antennas By Using Passive Scatterers, Joseph S. Zaren

Theses and Dissertations

The purpose of this study was to explore the viability of improving the performance of cavity-backed antennas. Traditionally antenna cavities are filled with electromagnetic absorber to mitigate interference effects that would otherwise cause the antenna radiation pattern to vary widely at different frequencies. The approach used in this research was to replace the absorber with dielectric slabs, some of which contained arrays of dipoles. These dipole arrays were modeled as frequency selective surfaces using two periodic moment method based - computer programs and one transmission line program. A systematic study was performed that identified the effect of changing the dipole …

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A Decision Support Model For Establishing A Plastics Recycling Program, Deven M. Dalcher Dec 1994

A Decision Support Model For Establishing A Plastics Recycling Program, Deven M. Dalcher

Theses and Dissertations

This research focuses on the development of a decision support model for the establishment of a plastics recycling program. The decision support model focuses on identifying the end-product uses and material specifications first. Once the end-product specifications have been identified, the recycling program can be designed. The model will provide solid waste managers an effective decision-making tool to evaluate the economic feasibility of establishing a plastics recycling program.

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Design, Fabrication, Modeling, And Optical Characterization Of Organic Polymer Nonlinear Directional Couplers, John N. Berry Dec 1994

Design, Fabrication, Modeling, And Optical Characterization Of Organic Polymer Nonlinear Directional Couplers, John N. Berry

Theses and Dissertations

This research was an investigation into the suitability of a recently developed polymer, polyphenylene, as a material for integrated optical circuits (IOCs). Polymers show great promise in the area of IOCs because of material processing advantages, compatibility with most existing integrated circuit technology, and relatively strong nonlinear optical characteristics. This thesis contains an overview of: dielectric waveguides, linear and nonlinear directional coupler theory; various models useful in the design and analysis of optical waveguides; the fabrication of three different waveguide designs; the experimental apparatus and procedure used to optically characterize the waveguides; and the experimental results of the characterization. Waveguiding …

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Design And Characterization Of Resonant Cavity Light-Emitting Diodes, Thomas M. Fitzgerald Dec 1994

Design And Characterization Of Resonant Cavity Light-Emitting Diodes, Thomas M. Fitzgerald

Theses and Dissertations

This thesis describes an investigation into the emission properties of Resonant Cavity Light Emitting Diodes (RCLED). RCLEDs are a new photonic device that promise laser-like properties of narrow output frequency spread and high output power, without the usual laser disadvantages of shorter lifetime and increased maintenance and lifetime costs. Specifically, this thesis examines the functional dependence between emitted wavelength and the RCLED microcavity, and attempts to correlate theory with experimental data. This thesis introduces a classical wave interference model that calculates the Spontaneous Emission Enhancement Factor (Z-) with angular dependence.

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Frame Selection Performance Limits For Statistical Image Reconstruction Of Adaptive Optics Compensated Images, Stephen D. Ford Dec 1994

Frame Selection Performance Limits For Statistical Image Reconstruction Of Adaptive Optics Compensated Images, Stephen D. Ford

Theses and Dissertations

The U.S. Air Force uses adaptive optics systems to collect images of extended objects beyond the atmosphere. These systems use wavefront sensors and deformable mirrors to compensate for atmospheric turbulence induced aberrations. Adaptive optics greatly enhance image quality; however, wavefront aberrations are not completely eliminated. Therefore, post-detection processing techniques are employed to further improve the compensated images. Typically, many short exposure images are collected, recentered to compensate for tilt, and then averaged to overcome randomness in the images and improve signal-to-noise ratio. Experience shows that some short exposure images in a data set are better than others. Frame selection exploits …

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Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell Dec 1994

Flow Visualization Of A Turbulent Shear Flow Using An Optical Wavefront Sensor, Daniel W. Jewell

Theses and Dissertations

The research reported here investigated the use of a shearing interferometer (SI) wavefront sensor to determine the effects of shear-layer turbulence on an optical wavefront. A collimated helium-neon laser beam was propagated through a plane shear-layer produced by mixing helium and nitrogen at different velocities. Since the gases have different indices of refraction, the optical wavefront was distorted by different amounts by each gas. The SI measured the wavefront slope across the sampled area of the wavefront. The shear-layer was viewed from two orthogonal directions. This document contains shadow graphs, interference patterns imaged by each of the SI's six cameras, …

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Image Perception Wavelet Simulation And Enhancement For The Visually Impaired, Lemuel Ray Myers Jr. Dec 1994

Image Perception Wavelet Simulation And Enhancement For The Visually Impaired, Lemuel Ray Myers Jr.

Theses and Dissertations

This research delves into the area of image enhancement for the visually impaired. Binocular macular degeneration a visual impairment, affects many Americans; since this condition could not be corrected with conventional glasses the literature suggested using an enhancement system which used a pre-emphasis algorithm to enhance the input image for output to the observer. The work of Dr. Eli Peli, a pioneer in the field of image enhancement, is examine and reproduced. Since his work concentrated mainly on frequency analysis of images, the bulk of this research involves using discrete wavelet analysis to augment that work. A biorthogonal wavelet set …

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Laser Beam Propagation In Non-Kolmogorov Atmospheric Turbulence, Bruce E. Stribling Dec 1994

Laser Beam Propagation In Non-Kolmogorov Atmospheric Turbulence, Bruce E. Stribling

Theses and Dissertations

Several observations of atmospheric turbulence statistics have been reported which do not obey Kolmogorov's power spectral density model. These observations have prompted the study of optical propagation through turbulence described by non-classical power spectra. This thesis presents an analysis of optical propagation through turbulence which causes index of refraction fluctuations to have spatial power spectra that obey arbitrary power laws. The spherical and plane wave structure functions are derived using Mellin transform techniques and are applied to the field mutual coherence function (MCF) using the extended Huygens-Fresnel principle. The MCF is used to compute the Strehl ratio of a focused, …

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Multispectral Detection Of Ground Targets In Highly Correlated Backgrounds, Jason E. Thomas Dec 1994

Multispectral Detection Of Ground Targets In Highly Correlated Backgrounds, Jason E. Thomas

Theses and Dissertations

Multispectral detection methods attempt to discriminate targets in a dominant clutter background using multiple images of the same real-world scene taken in different narrow spectral bands in the infrared. Detection is possible due to the empirically observed phenomenon that the radiance of man-made objects, such as a tank or truck, often lies off the main spectral correlation axis of that of natural backgrounds. Radiometric measurements of several vehicles and a tree canopy background taken over three days in June. 1994 were used to examine the factors affecting multispectral detection. Results clearly showed that the processes which provide for higher spectral …

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An Improved Heuristic For Intercontinental Ballistic Missile Crew Scheduling, Michael D. Shirley Jr. Dec 1994

An Improved Heuristic For Intercontinental Ballistic Missile Crew Scheduling, Michael D. Shirley Jr.

Theses and Dissertations

Creating monthly schedules for missile crews is a complex and time-consuming problem. Thousands of events must be scheduled for several hundred missile officers. The rules and regulations governing the problem are numerous, and there are currently no established measures for missile crew schedules. The scheduling software currently available only schedules a fraction of the events. The objectives of this research were to create a rule-based heuristic which could quickly produce feasible or near-feasible schedules, to make the scheduling process paperless, and to develop possible measures of effectiveness for missile crew schedules. The research was successful in each of these areas. …

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Computing Norad Mean Orbital Elements From A State Vector, Dwight E. Andersen Dec 1994

Computing Norad Mean Orbital Elements From A State Vector, Dwight E. Andersen

Theses and Dissertations

NORAD maintains and disseminates mean orbital elements on Earth-orbiting satellites in the form of Two-Line Element Sets (TLE). Five mathematical propagator models were developed for NORAD's use to predict the position and velocity using TLEs. This study investigated two approaches, Newton's method and direct iteration, to inverting this process by iterating to obtain NORAD-compatible mean orbital elements from a position and velocity state vector and the drag term. The Newton's iteration method was developed but not tested. The less computationally intensive direct iteration method was developed, coded in FORTRAN, and tested. The initial guess and subsequent corrections in the iterative …

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A Systems Engineering Approach To Environmental Risk Management: A Case Study Of Depleted Uranium At Test Area C-64, Eglin Air Force Base, Florida, Charles M. Carter, Kristina M. Fortmann, Stephen W. Hill, Robert M. Latin, Edward J. Masterson, Joseph A. Roh, Sujay R. Setlur Dec 1994

A Systems Engineering Approach To Environmental Risk Management: A Case Study Of Depleted Uranium At Test Area C-64, Eglin Air Force Base, Florida, Charles M. Carter, Kristina M. Fortmann, Stephen W. Hill, Robert M. Latin, Edward J. Masterson, Joseph A. Roh, Sujay R. Setlur

Theses and Dissertations

Environmental restoration is an area of concern in an environmentally conscious world. Much effort is required to clean up the environment and promote environmentally sound methods for managing current land use. In light of the public consciousness with the latter topic, the United States Air Force must also take an active role in addressing these environmental issues with respect to current and future USAF base land use. This thesis uses the systems engineering technique to assess human health risks and to evaluate risk management options with respect to depleted uranium contamination in the sampled region of Test Area (TA) C-64 …

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Tracking And Impact Prediction Of Earth-Crossing-Objects (Ecos) On A Collision Course With Earth, Gregory A. Bishop Dec 1994

Tracking And Impact Prediction Of Earth-Crossing-Objects (Ecos) On A Collision Course With Earth, Gregory A. Bishop

Theses and Dissertations

This study investigated the effectiveness of Earth-based angles only observations in determining the orbit of various hypothetical Earth-Crossing-Objects (ECOs). 'True' trajectories were simulated specifically for Earth-Crossing- Comets (ECCs) by numerically integrating in a Restricted Three Body system. Starting at Earth impact points, the state vectors were reverse-propagated" to a proposed detection time. Observations (obs), with state-of-the-art accuracy, were then simulated with error induced by a Gaussian random number generator; these were used in a least- squares differential corrector to estimate the positions of the ECOs. State vectors and covariance matrices were then propagated to the impact times and axis lengths …

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Effects Of Photon Noise On Unconstrained Minimization Techniques For Iterative Blind Deconvolution, Derek K. Davis Dec 1994

Effects Of Photon Noise On Unconstrained Minimization Techniques For Iterative Blind Deconvolution, Derek K. Davis

Theses and Dissertations

In recent years, imaging through atmospheric turbulence has interested military scientists seeking to improve optical surveillance of satellites. Adaptive optics was a step toward achieving diffraction-limited resolution from ground-based telescopes. Unfortunately, adaptive optics only partially compensate for atmospheric blurring, therefore post processing of images is required. Processing methods in use today require knowledge of the impulse response of the optical system to reconstruct imagery, but this information is seldom known. This thesis looks at a new metal of processing compensated imagery, called blind deconvolution, which assumes very little or no a priori information about the impulse response. In particular, this …

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An Analysis Of The Kc-135 Three-Person Cockpit, Robert A. Deivert Dec 1994

An Analysis Of The Kc-135 Three-Person Cockpit, Robert A. Deivert

Theses and Dissertations

In an effort to quantitatively determine the utility of mission effectiveness of the KC-135, this research used value-focused thinking to measure the impact of replacing the KC-135 navigator with upgraded avionics. A Value Model was developed as a hierarchy with fundamental objectives at the highest level and attributes at the lowest level. Weights were assigned to show the contribution each level had to the one above it. The attributes were given a score and an additive model was used to determine utility with and without a navigator. Break-even analysis and net present value calculations were done to show the costs …

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Voice Analysis Using The Bispectrum, Deborah A. Douglass Dec 1994

Voice Analysis Using The Bispectrum, Deborah A. Douglass

Theses and Dissertations

The theory of the bispectrum has been studied, though very few practical applications have yet been considered in any depth. One application mentioned in the literature is the use of the bispectrum for voice signal processing. The aim of this thesis was to research the bispectrum towards the particular application of speech enhancement. The technique is based on the fact that the bispectrum is zero for a Gaussian white noise signal, arid the bispectrum of two signals added together is the sum of the two signal bispectra. Theoretically, processing signals in the bispectra domain should increase the signal-to-noise ratio of …

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Optimization Of A Nutation Damper Attached To A Spin-Stabilized Satellite, Brady P. Hauboldt Dec 1994

Optimization Of A Nutation Damper Attached To A Spin-Stabilized Satellite, Brady P. Hauboldt

Theses and Dissertations

This study uses linearized equations of motion for a rigid body with an attached spring-mass-damper to maximize the decay rate of a satellite's coning motion. An analysis of the numerical eigenvalues is presented which leads to an optimal relationship between relevant parameters: damper placement, spring constant, damping coefficient, system moments of inertia, and damper mass fraction. The coupled system's eigenvalues do not provide truly critical damping, thus the real eigenvalue parts are minimized in order to achieve damping which requires the minimum amount of time. A comparison between this optimal design method and a classical method concludes a noticeable improvement …

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The Effects Of An Integrated Space Support Node On Theater Air Combat, Paul J. Helt Dec 1994

The Effects Of An Integrated Space Support Node On Theater Air Combat, Paul J. Helt

Theses and Dissertations

The Air Force requires a methodology to assess alternative means for providing integrated space support data, collected from imagery space platforms, to enhance overall theater warfighting capability. This research examines imagery systems supporting the warning, surveillance, and weather missions, alternative concepts to integrate this imagery data, and models their influence on air-to-ground and limited ground-to-air combat in five potential theaters of operation. These theaters were Northeast Asia, Southeast Asia, Southeast Europe, the Caribbean, and Central America. Influence diagram decision analysis techniques were used to identify and quantify the key variables within the three space-based mission areas effecting air combat planning …

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