Aerospace Engineering Commons^™

Signal Quality Monitoring Of Gnss Signals Using A Chip Shape Deformation Metric, Nicholas C. Echeverry

Theses and Dissertations

The Global Navigation Satellite System continues to become deeply em-bedded within modern civilization, and is depended on for confident, accurate navigation information. High precision position and timing accuracy is typically achieved using differential processing, however these systems provide limited compensation for distortions caused by multi-path or faulty satellite hardware. Signal Quality Monitoring (SQM) aims to provide confidence in a receivers Position, Navigation, and Timing solution and to offer timely warnings in the event that signal conditions degrade to unsafe levels. The methods presented in this document focus on implementing effective SQM using low-cost Commercial Off-the-Shelf equipment, a Software Defined Radio, …

Design Of A Hardware Platform For Gps-Based Orientation Sensing, Daniel Eugene Kirkpatrick

Dissertations and Theses

Unmanned aerial vehicles (UAV's) have recently gained popularity in military, civil service, agriculture, commercial, and hobby use. This is due in part to their affordability, which comes from advances in component technology. That technology includes microelectromechanical systems (MEMS) for inertial sensing, microprocessor technology for sequential algorithm processing, field programmable gate arrays (FPGA's) for parallel data processing, camera technology, global navigation satellite systems (GNSS's) for navigation, and battery technology such as the high energy density of lithium polymer batteries.

Despite the success of the technology to date, there remains development before UAV's should be flying alongside manned aircraft or over populated …

Orbital Tori Construction Using Trajectory Following Spectral Methods, Ralph E. Bordner Iii

Theses and Dissertations

By assuming the motion of a satellite about the earth’s geopotential mimics the known Kolmogorov-Arnold-Moser (KAM) solution of a lightly perturbed integrable Hamiltonian system, this research focused on applying trajectory following spectral methods to estimate orbital tori from sampled orbital data. From an estimated basis frequency set, orbital data was decomposed into multi-periodic Fourier series, essentially compressing ephemerides for long-term use. Real-world Global Positioning System (GPS) orbital tracks were decomposed and reconstructed with error from as low as few kilometers per coordinate axis over a 10-week span to tens of kilometers per coordinate axis over the same time period, depending …

Aiding Gps With Additional Satellite Navigation Services, Yasin A. Mutlu

Theses and Dissertations

In modern warfare navigation services are very important. GPS is currently providing service for accurate navigation, except in some areas, especially urban areas, where GPS signals cannot always be tracked by users. In these cases some additional navigation support could be provided by other global navigation satellite systems. If GPS is combined with other navigation systems than the navigation gap will be minor. In this thesis, the effect of combining GPS with other satellite navigation systems, specifically GLONASS, Galileo and Compass, is evaluated in terms of availability and position dilution of precision (PDOP) values. First, satellite constellations are simulated in …

Global Navigation Satellite System Software Defined Radio, Jason M. Mcginthy

Theses and Dissertations

The GNSS world is quickly growing. The United States’ GPS, the European Union’s Galileo, China’s Compass, and Russia’s GLONASS systems are all developing or modernizing their signals, and there will soon be more navigation satellites in space than ever before. The goal of this research was to develop an initial capability for an AFIT GNSS software receiver. This software receiver is intended to be used for research purposes at the Advanced Navigation Technology (ANT) Center. First a GPS-only software receiver was built. It successfully acquired, tracked, and provided reasonable position estimates. Next, the receiver was successfully modified to acquire and …

Failure Detection Of A Pseudolite-Based Reference System Using Residual Monitoring, Michael A. Ciampa

Theses and Dissertations

The 746th TS uses a flight reference system referred to as the Central Inertial and GPS Test Facility (CIGTF) Reference System (CRS). Currently the CRS is the modern standard flight reference system for navigation testing, but high accuracy is dependent on the availability of GPS. A pseudolite system is currently being developed to augment the CRS and supply the capability to maintain high accuracy navigation under normal and jamming conditions. Pseudolite measurements typically contain cycle slips and other errors (such as multipath, tropospheric error, measurement noise) that can affect reliability. Past work relied on the receiver-reported signal-to-noise (SNR) value to …

A Feasibility Study Of A Persistent Monitoring System For The Flight Deck Of U.S. Navy Aircraft Carriers, Jeffrey S. Johnston

Theses and Dissertations

This research analyzes the use of modern Real Time Locating Systems (RTLS), such as the Global Positioning System (GPS), to improve the safety of aircraft, equipment, and personnel onboard a United States Navy (USN) aircraft carrier. The results of a detailed analysis of USN safety records since 1980 show that mishaps which could potentially be prevented by a persistent monitoring system result in the death of a sailor nearly every other year and account for at least $92,486,469, or 5.55% of the total cost of all flight deck and hangar bay related mishaps. A system to continually monitor flight deck …

Modeling Gps Satellite Orbits Using Kam Tori, Rachel M. Derbis

Theses and Dissertations

Global Positioning System (GPS) satellite orbits are modeled using Kolmogorov, Arnold, Moser (KAM) tori. Precise Global Positioning System satellite locations are analyzed using Fourier transforms to identify the three basis frequencies in an Earth Centered, Earth Fixed (ECEF) rotating reference frame. The three fundamental frequencies are 1) the anomalistic frequency, 2) a combination of earth’s rotational frequency and the nodal regression rate, and 3) the apsidial regression rate. A KAM tori model fit to the satellite data could be used to predict future satellite locations. This model would allow rapid determination with fewer computational requirements than the typical method of …

Real-Time Gps-Alternative Navigation Using Commodity Hardware, Jordon L. Fletcher

Theses and Dissertations

Modern navigation systems can use the Global Positioning System (GPS) to accurately determine position with precision in some cases bordering on millimeters. Unfortunately, GPS technology is susceptible to jamming, interception, and unavailability indoors or underground. There are several navigation techniques that can be used to navigate during times of GPS unavailability, but there are very few that result in GPS-level precision. One method of achieving high precision navigation without GPS is to fuse data obtained from multiple sensors. This thesis explores the fusion of imaging and inertial sensors and implements them in a real-time system that mimics human navigation. In …

Use Of Two-Way Time Transfer Measurements To Improve Geostationary Satellite Navigation, Benjamin G. Dainty

Theses and Dissertations

An emerging use of GPS is to provide accurate navigation information for satellites in orbit. The GPS satellites are designed to provide service to terrestrial users, so the antenna array points directly towards the Earth and uses a narrow primary beamwidth. Because GEO altitudes are well above the GPS constellation, the Earth occludes most of the GPS signals to the satellite. Decreased satellite visibility is debilitating, as GPS navigation requires at least four visible satellites to determine position. To assist with the visibility problem, the receiver can look at the GPS satellite transmit antenna side lobes, but this does not …

Development And Testing Of A High-Speed Real-Time Kinematic Precise Dgps Positioning System Between Two Aircraft, Christopher J. Spinelli

Theses and Dissertations

This research involves the design, implementation, and testing of a high-speed, real-time kinematic, precise differential GPS positioning system for use in airborne applications such as automated aerial-refueling and close formation flying. Although many of the current ambiguity resolution techniques use the residuals from the least squares position estimation to determine the true ambiguity set, this thesis presents a novel approach to the ambiguity resolution problem, called the minimum indicator. Instead of assuming the ambiguity set with the lowest residuals is the true set, other special characteristics of the residuals are examined. This increases the confidence that the algorithm has selected …

Development Of A Low-Latency, High Data Rate, Differential Gps Relative Positioning System For Uav Formation Flight Control, Stephen J. Comstock

Theses and Dissertations

In order for Unmanned Aerial Vehicles (UAVs) to be able to fly missions currently performed by manned aircraft, they must be able to conduct in-flight refueling. Additionally, significant fuel savings can be realized if multiple UAV's are able to fly in precise formation and align wingtip vortices. In either case, the precise relative position between the aircraft must be known to an accuracy of only a few centimeters. Previous research at the Air Force Institute of Technology culminated in the development of a relative positioning system for manned aircraft. This thesis presents the development of the next-generation system designed for …

Fusion Of Imaging And Inertial Sensors For Navigation, Michael J. Veth

Theses and Dissertations

The motivation of this research is to address the limitations of satellite-based navigation by fusing imaging and inertial systems. The research begins by rigorously describing the imaging and navigation problem and developing practical models of the sensors, then presenting a transformation technique to detect features within an image. Given a set of features, a statistical feature projection technique is developed which utilizes inertial measurements to predict vectors in the feature space between images. This coupling of the imaging and inertial sensors at a deep level is then used to aid the statistical feature matching function. The feature matches and inertial …

Optimal Geometric Deployment Of A Ground Based Pseudolite Navigation System To Track A Landing Aircraft, Matthew P. Crawford

Theses and Dissertations

With much of the military and civilian communities becoming dependent on GPS technology to navigate it has become imperative that the navigation systems be tested in situations in which GPS does not work. This testing is especially necessary for precise tasks such as landing an aircraft. Currently, research is being conducted into using a pseudolite-based reference system to use as a truth model for the GPS jamming test. Pseudolite systems have been proven to provide sub-centimeter level accuracy in the horizontal plane; however in the vertical plane the position error is still in the decimeter to meter level range. This …

Methods For Aiding Height Determination In Pseudolite-Based Reference Systems Using Batch Least-Squares Estimation, John H. R. Amt

Theses and Dissertations

There are many situations in which GPS is either unable to provide the desired level of accuracy or is unavailable. Use of a pseudolite-based reference system for navigation can be a means for positioning during these times. While there are advantages in using a pseudolite-based reference system, there are still implementation issues and deficiencies that must be addressed. In many cases, a pseudolite system with ground-based transmitters has difficulty determining the height of the receiver accurately. This is due to the poor vertical observability inherent in the geometry of the system. A common approach in naval applications for solving the …

The Use Of X-Ray Pulsars For Aiding Gps Satellite Orbit Determination, Dennis W. Woodfork Ii

Theses and Dissertations

This research proposes the use of an existing "signal of opportunity" - namely x-ray pulsars - to improve the accuracy and robustness of the GPS satellite and clock estimation algorithm. Improvement in satellite and clock accuracy results in a direct benefit to the user. A simulation has been developed to determine the effects of using x-ray pulsar measurements on the GPS Operational Control Segment. The epoch-specific position, velocity, and clock errors of all GPS satellites in the constellation were estimated using both pseudoranges and time-difference-of-arrival (TDOA) measurements from pulsars. The primary measure of accuracy is a constellation Signal-In-Space Range Error …

Tightly-Coupled Image-Aided Inertial Navigation System Via A Kalman Filter, Michael G. Giebner

Theses and Dissertations

Inertial navigation systems and GPS systems have revolutionized the world of navigation. Inertial systems are incapable of being jammed and are the backbone of most navigation systems. GPS is highly accurate over long periods of time, and it is an excellent aid to inertial navigation systems. However, as a military force we must be prepared to deal with the denial of the GPS signal. This thesis seeks to determine it, via simulation, it is viable to aid an INS with visual measurements.

Development And Simulation Of A Pseudolite-Based Flight Reference System, Terry J. Bouska

Theses and Dissertations

Current flight reference systems are vulnerable to GPS jamming and also lack the accuracy required to test new systems. Pseudolites can augment flight reference systems by improving accuracy, especially in the presence of GPS jamming. This thesis evaluates a pseudolite-based flight reference system which applies and adapts carrier-phase differential GPS techniques. The algorithm developed in this thesis utilizes an extended Kalman filter along with carrier-phase ambiguity resolution techniques. A simulation of the pseudolite-based positioning system realistically models measurement noise, multipath, pseudolite position errors, and tropospheric delay. A comparative evaluation of the algorithms performance for single and widelane frequency measurements is …

Performance Tradeoff Study Of A Gps-Aided Ins For A Rocket Trajectory, Muhittin Istanbulluoglu

Theses and Dissertations

The Turkish Air Force (TuAF) has started a project to launch a satellite using only Turkish resources. Primary motivation behind this research is to assist TuAF's project by keeping up with these innovations in the navigational arena. The basic challenge in navigation system design is to decide which navigation system (or systems) and implementation techniques will be used, depending on accuracy requirements. The two primary navigation systems that will be integrated in this research are the Inertial Navigation System (INS), and the Global Positioning System (GPS). The Kalman filter algorithm is used to integrate INS and GPS. The rocket (Atlas …

Using The Gps To Collect Trajectory Data For Ejection Seat Design, Validation, And Testing, Brian R. Tredway

Theses and Dissertations

The dynamic characteristics of an aircraft ejection seat are a crucial concern when evaluating aircraft ejection systems and their ability to separate aircrew members safely from disabled aircraft. Every ejection seat model undergoes real-time dynamic tests to determine potential injury to aircrew members during ejection. Ejection seat tests are conducted at high-speed test tracks. The test track facilities provide the required telemetry and high-speed photography to monitor and validate the aircraft escape system performance. Ejection seat test and evaluation requires very accurate position and velocity determination during each test run to determine the relative positions between the aircraft, ejection seat, …

Broadcast Vs Precise Gps Ephemerides: A Historical Perspective, David L. M. Warren

Theses and Dissertations

In most recent years, both high-resolution imagery systems and images were only available to military and national security organizations. Distinctive changes within the commercial image industry allowed space-borne pioneers to provide high-resolution images. Space-borne Image Company's Ikonos satellite provides a 1-meter resolution for the past 3 years. Current development of .5-meter resolution will be offered in the near future. Access of these images is available in ground stations located worldwide in different regions. Studies have shown that these high quality images are eye-catching and may serve a purpose through its design; on contrary high cost and accessibility does not met …

Estimation Of Relative Satellite Formation Elements In Near Circular Orbits, Ralph E. Bordner Iii

Theses and Dissertations

Precise relative position determination of satellite formation elements in near circular orbits is the focus of this thesis. A Bayes filter is used for the estimator with the dynamics solution obtained by solving the time periodic, linearized system via Floquet theory. This approach is similar to that of the traditional Clohessy-Wiltshire treatment, however much more of the system's behavior is retained by using a linear, time periodic system. The dynamics model includes all zonal harmonics of the Earth as well as sectoral, tesseral, and air drag perturbations. The filter algorithm was fed three types of simulated measurements: relative Carrier-Phases Differential …

Development And Testing Of A Multiple Filter Approach For Precise Dgps Positioning And Carrier-Phase Ambiguity Resolution, Paul E. Henderson

Theses and Dissertations

The most precise relative positioning obtained using differential GPS depends on accurately determining carrier-phase integer ambiguities. To achieve high precision, many current static and kinematic algorithms use a floating-point solution until enough information becomes available to fix the carrier-phase ambiguities accurately. A mew method is presented that uses a multiple model Kalman filter to resolve the carrier-phase integer ambiguities. This method starts with the floating-point results, yet smoothly and rapidly attains the precision of the correct fixed-integer solution, eliminating the need to decide when to switch from the floating to the fixed-integer solution. This method is based on a theoretically …

Design And Analysis Of On-Orbit Servicing Architectures For The Global Positioning System Constellation, Gregg A. Leisman, Adam D. Wallen

Theses and Dissertations

Satellites are the only major Air Force systems with no maintenance, routine repair, or upgrade capability. The result is expensive satellites and a heavy reliance on access to space. At the same time, satellite design is maturing and reducing the cost to produce satellites with longer design lives. This works against the ability to keep the technology on satellites current without frequent replacement of those satellites. The Global Positioning System Joint Program Office realizes that it must change its mode of operations to quickly meet new requirements while minimizing cost. The possibility of using robotic servicing architectures to solve these …

Optimization Of A Gps-Based Navigation Reference System, Jason B. Mckay

Theses and Dissertations

The development of increasingly accurate new aircraft navigation systems has caused the Air Force to develop a new Navigation Reference System to test them, called the Submeter Accuracy Reference System (SARS). The SARS is an inverted GPS system which consists of an array of GPS receivers on the ground and an airborne pseudolite mounted on the test aircraft. The SARS will provide a proof position estimate that is used to check the navigation system under test. Unfortunately, ground based inverted GPS systems tend to suffer from high geometric sensitivity to measurement errors. This research tackles the problem of optimizing the …

A Differential Gps Aided Ins For Aircraft Landings, Ryan L. Britton

Theses and Dissertations

The Department of Defense (DOD) and the commercial airline industry are in the process of replacing the instrument landing system (ILS) for aircraft precision approach landings. The use of differential Global Positioning System (DGPS) is thought to be a viable replacement for ILS precision approaches. This thesis explores the integration of an INS, DGPS, Barometric Altimeter, Pseudolite, and Radar Altimeter for a tanker type and a single engine aircraft precision approach. These devices are integrated using an extended Kalman filter (EKF). For the tanker type aircraft federal Aviation Administration (FAA) requirements for a Category I and a Category II precision …

Velocity Determination For An Inverted Pseudolite Navigation Reference System, Jeffrey M. Hebert

Theses and Dissertations

As navigation systems continue to improve in performance and features, the Air Force must develop better Navigation Reference Systems (NRS) to keep pace with technology. Specifically, with the advent of enhanced, integrated Global Positioning System (GPS) and Inertial Navigation System (INS) navigators, emphasis is placed on the measuring performance in the presence of GPS jamming. To meet these needs, a new NRS, dubbed the Sub-Meter Accuracy Reference System (SARS), is being developed by the 746th Test Squadron, Holloman AFB, New Mexico. SARS uses a unique, inverted GPS pseudolite positioning system to determine a reference trajectory. This research investigates two post …

Wing Flexure Compensation For Aircraft Attitude And Position Determination In An Inverted Carrier-Phase Positioning System, Bradley W. Mahlum

Theses and Dissertations

In response to the ever increasing accuracies in inertial navigation systems, the U. S. Air Force must develop higher accuracy reference systems. These reference systems must also be small enough to be utilized in the testing of navigation systems onboard fighter aircraft. One such proposed system utilizes carrier-phase Global Positioning System (CPGPS) transmitters mounted on MM-9 pods with receivers on the ground. This research examines one possible method of utilizing this system to determine the attitude and position of the aircraft, given position estimates for the transmitter's locations. The transmitter positioning algorithm showed that the geometry will be problematic for …

Design And Analysis Of A Navigation System Using The Federated Filter, Stephen J. Delory

Theses and Dissertations

The purpose of this paper was to design and analyse a federated filter design, to be used for retrofit of an Embedded GPS/INS (EGI) navigation unit into an existing Kalman filter-based air navigation system. A design was selected and simulations were conducted in the Distributed Kalman Filter Simulation software (DKFSIM). As well, a centralized Kalman filter design was simulated under identical conditions for comparison purposes. The federated filter was shown to be a feasible design, with accuracy in position and velocity very close to centralized Kalman filter values. The federated filter design also showed some attractive fault detection and isolation …

Systems Analysis Of Gps Electrical Power System Redesign, Kevin J. Walker

Theses and Dissertations

A systematic analysis is applied to the electrical power subsystem of the Global Positioning Satellite (GPS) system. Results determined the most appropriate power source and conversion system Options. Photovoltaic solar arrays, the current power system, were not included in the analysis. The best electrical power subsystem options found in the analysis include a solar power source with either a dynamic or direct conversion technique, and a direct conversion nuclear source. The two solar options are designed, at a low level of detail, to provide the same level of power the current GPS photovoltaic solar array system provides. These two designs …