<p>In this thesis the problem of multitarget tracking in multistatic sensor networks is studied. This thesis focuses on tracking airborne targets by utilizing transmitters of opportunity in the surveillance region. Passive Coherent Location (PCL) system, which uses existing commercial signals (e.g., FM broadcast, digital TV) as the illuminators of opportunity for target tracking, is an emerging technology in air defence systems. PCL systems have many advantages over conventional radar systems such as low cost, covert operation and low vulnerability to electronic counter measures.</p> <p>One of another opportunistic signals available in the surveillance region is multipath signal. In this thesis, the multipath target return signals from distinct propagation modes that are resolvable by the receiver are exploited. When resolved multipath returns are not utilized within the tracker, i.e., discarded as clutter, potential information conveyed by the multipath detections of the same target is wasted. In this case, spurious tracks are formed using target-originated multipath measurements, but with an incorrect propagation mode assumption. Integrating multipath information into the tracker (and not discarding it) can help improve the accuracy of tracking and reduce the number of false tracks.</p> <p>In this thesis, these opportunistic measurements, i.e., commercial broadcast signals measurements in PCL tracking and resolvable multipath target return measurements in multipath assisted tracking are exploited. We give the optimal formulations for all of the above problems as well as the performance evaluations using PCRLB. Simulation results illustrate the performance of the algorithms.</p> / Doctor of Philosophy (PhD)

In the aviation industry, digitally produced and presented flight, navigation, and aircraft information is commonly referred to as glass flight decks. Glass flight decks are driven by computer-based subsystems and have long been a part of military and commercial aviation sectors. Over the past 15 years, the General Aviation (GA) sector of the aviation industry has become a recent beneficiary of the rapid advancement of computer-based glass flight deck (GFD) systems. While providing the GA pilot considerable enhancements in the quality of information about the status and operations of the aircraft, training pilots on the use of glass flight decks is often delivered with traditional methods (e.g. textbooks, PowerPoint presentations, user manuals, and limited computer-based training modules). These training methods have been reported as less than desirable in learning to use the glass flight deck interface. Difficulties in achieving a complete understanding of functional and operational characteristics of the GFD systems, acquiring a full understanding of the interrelationships of the varied subsystems, and handling the wealth of flight information provided have been reported. Documented pilot concerns of poor user experience and satisfaction, and problems with the learning the complex and sophisticated interface of the GFD are additional issues with current pilot training approaches. A case study was executed to explore ways to improve training using GFD systems at a Midwestern aviation university. The researcher investigated if variations in instructional systems design and training methods for learning glass flight deck technology would affect the perceptions and attitudes of pilots of the learnability (an attribute of usability) of the glass flight deck interface. Specifically, this study investigated the effectiveness of scenario-based training (SBT) methods to potentially improve pilot knowledge and understanding of a GFD system, and overall pilot user experience and satisfaction. Participants overwhelmingly reported positive learning experiences from scenario-based GFD systems flight training, noting that learning and knowledge construction were improved over other training received in the past. In contrast, participants rated the usability and learnability of the GFD training systems low, reporting various problems with the systems’ interface, and the learnability (first-time use) of the complex GFD system. However, issues with usability of the GFD training systems did not reduce or change participant attitudes towards learning and mastering GFD systems; to the contrary, all participants requested additional coursework opportunities to train on GFD systems with the scenario-based flight training format.

A student-based university environment for engineering design and development is much different from a product development environment within the aerospace industry. Therefore, a different approach to systems engineering should be considered. By its very nature, a university product development laboratory thrives on creativity and rejects bureaucracy. Experience shows that continuity and discipline within a project is crucial for success. The practice of systems engineering enables technical project discipline. Systems engineering is the art and science of developing an operable system that meets requirements within imposed constraints. The purpose of this thesis is to describe the systems engineering processes and techniques necessary for a student-based project, and explicitly show how to implement these processes. Although attempts have been made to utilize a few systems engineering techniques in past projects, many students did not properly and consistently apply those techniques to the technical design work. The goal of the thesis is to tailor the NASA systems engineering processes to a student-based design laboratory environment and to apply the methodologies to the mission design of Paradox. The Picosatellite for Autonomous Rendezvous and Docking on-Orbit eXperiment, or Paradox, is the second of four missions to demonstrate autonomous rendezvous and docking with a picosatellite-class satellite. A strong technical contribution highlighted within the thesis involves developing an open architecture rendezvous targeting algorithm for the Paradox mission in the face of large mission architecture uncertainties. The robust targeting algorithm builds from previous work utilizing an optimizer based on the Clohessey-Wiltshire equations and an iterative Lambert targeter. The contribution extends the rendezvous transfer times by including a multi-revolution Lambert targeter. The rendezvous algorithm will perform successfully given any launch vehicle and target spacecraft vehicle supporting the notion of an open architecture to satisfy the mission. The development of the algorithm is embedded within the context of the systems engineering processes to clearly showcase the intimate connection between systems engineering processes and the technical engineering design of a mission. / text

Schizophrenia is a severe neuropsychiatric disorder characterized by positive, negative and cognitive symptoms with poor functional outcomes, placing an enormous burden on the individual, caregivers and society. Although deficits in cognition are an integral part of the disease and the best predictor of functional outcomes, there is as yet no established treatment addressing them. Avoidance of a hidden place on a continuously rotating arena (Carousel) requires cognitive control and is a rodent model of cognitive coordination of information from dissociated spatial frames, which is impaired in acute pharmacological and neurodevelopmental model of schizophrenia. Cognitive training on the Carousel during adolescence alleviates adult cognitive deficit in a neurodevelopmental model of schizophrenia and improves neural coordination (oscilations in the beta and gamma band), which is thought to be necessary for cognition. We examined if cognitive training during adolescence eliminates the deficit in neuronal coordination observed in adult rats after acute systemic NMDA receptor antagonist MK-801 (0.15 mg/kg). During adolescence, rats were either trained in spatial avoidance on Carousel or merely handled. As adults, rats received two 5-min exploration sessions in the same (A/A) or in two distinct...

<div>The orbits of interest for potential missions are stable or nearly stable to maintain long term presence for conducting scientific studies and to reduce the possibility of rapid departure. Near Rectilinear Halo Orbits (NRHOs) offer such stable or nearly stable orbits that are defined as part of the L1 and L2 halo orbit families in the circular restricted three-body problem. Within the Earth-Moon regime, the L1 and L2 NRHOs are proposed as long horizon trajectories for cislunar exploration missions, including NASA's upcoming Gateway mission. These stable or nearly stable orbits do not possess well-distinguished unstable and stable manifold structures. As a consequence, existing tools for stationkeeping and transfer trajectory design that exploit such underlying manifold structures are not reliable for orbits that are linearly stable. The current investigation focuses on leveraging stretching direction as an alternative for visualizing the flow of perturbations in the neighborhood of a reference trajectory. The information supplemented by the stretching directions are utilized to investigate the impact of maneuvers for two contrasting applications; the stationkeeping problem, where the goal is to maintain a spacecraft near a reference trajectory for a long period of time, and the transfer trajectory design application, where rapid departure and/or insertion is of concern.</div><div><br></div><div>Particularly, for the stationkeeping problem, a spacecraft incurs continuous deviations due to unmodeled forces and orbit determination errors in the complex multi-body dynamical regime. The flow dynamics in the region, using stretching directions, are utilized to identify appropriate maneuver and target locations to support a long lasting presence for the spacecraft near the desired path. The investigation reflects the impact of various factors on maneuver cost and boundedness. For orbits that are particularly sensitive to epoch time and possess distinct characteristics in the higher-fidelity ephemeris model compared to their CR3BP counterpart, an additional feedback control is applied for appropriate phasing. The effect of constraining maneuvers in a particular direction is also investigated for the 9:2 synodic resonant southern L2 NRHO, the current baseline for the Gateway mission. The stationkeeping strategy is applied to a range of L1 and L2 NRHOs, and validated in the higher-fidelity ephemeris model.</div><div><br></div><div>For missions with potential human presence, a rapid transfer between orbits of interest is a priority. The magnitude of the state variations along the maximum stretching direction is expected to grow rapidly and, therefore, offers information to depart from the orbit. Similarly, the maximum stretching in reverse time, enables arrival with a minimal maneuver magnitude. The impact of maneuvers in such sensitive directions is investigated. Further, enabling transfer design options to connect between two stable orbits. The transfer design strategy developed in this investigation is not restricted to a particular orbit but applicable to a broad range of stable and nearly stable orbits in the cislunar space, including the Distant Retrograde Orbit (DROs) and the Low Lunar Orbits (LLO) that are considered for potential missions. Examples for transfers linking a southern and a northern NRHO, a southern NRHO to a planar DRO, and a southern NRHO to a planar LLO are demonstrated.</div>

Digital beamforming is a powerful signal processing technique used in many communication and radar sensing applications. However, despite its many advantages, its high cost makes it a less popular choice than other directional antenna options. The development of a low cost architecture for digital beamforming would make it a more feasible option, allowing it to be used for a number of new applications. Specifically, the Collaborative, Adaptive Sensing of the Atmosphere (CASA) project’s Distributed Collaborative Adaptive Sensing (DCAS) system, a low cost weather radar system, could benefit from the incorporation of digital beamforming into small, inexpensive but highly functional radars. Existing DBF architectures are implemented in complex systems which include a number of expensive processing modules and other associated hardware. This project shows a low-cost digital beamforming architecture that has been developed by utilizing today’s powerful and inexpensive FPGA devices along with recently available low-voltage-differential-signaling enabled multi-channel analog to digital conversion hardware. The utilization of commercially available devices rather than custom hardware allows this architecture to be manufactured at a fraction of the cost of most. This makes it a viable alternative to the classic dish antennas for the DCAS system, allowing a reduction in size and cost which will benefit deployment. The flexibility of an FPGA-based DBF system will result in a more robust radar system. With this in mind, an architecture has been developed, fabricated and evaluated.