Fast interference localization to protect global navigation satellite service operations
Keywords: Aeronautics and Astronautics.

Global Navigation Satellite Systems (GNSS) have become an invisible utility at the core of many modern industries. It is responsible for the safe and reliable navigation of ships and planes, for providing timing required by communications infrastructure and the financial industry, and for being a driving sensor in the autonomous future. It is so critical that many nations, or groups of nations, around the world have spared no expense to develop their own independent systems to not rely on another nation's system. However, by the time the signal reaches the Earth's surface its power is well below the noise floor, and, like any radio system, it is susceptible to interference. This interference, whether intentional or not, can cause disastrous effects on those relying on the reception of GNSS effects. Therefore, the goal of the work presented in this thesis is to develop and demonstrate in real-world environments an autonomous system capable of localizing the source of GNSS interference on a time scale of minutes and hours instead of the days and even months it can take today. To accomplish this, this thesis presents contributions to the hardware required to enable rapid localization from an unmanned aerial vehicle and to the algorithms needed to operate day or night with or without GNSS for navigation. Previous work on rapid signal localization from an unmanned aerial vehicle relied on three core elements: a sensor to provide a spatial view of the signal strength, an algorithm to observe direction of arrival, and a set of algorithms to estimate the source and plan a path to collect the best measurements possible. This thesis mimics the same flow but provides significant improvements to each step in the process and additionally adds capabilities of navigating in a GNSS denied environment potentially posed by a GNSS interference source. Each improvement to the process is not just theoretical in nature, each system is implemented and tested in real-world environments. This thesis presents a shift from a bulky physical rotation modality to provide a spatial view of the signal strength (known as a received signal strength pattern) to an electronic rotation modality using a lightweight antenna array, significantly increasing the rate of bearing observations possible -- and therefore data into the estimation algorithm -- and de-coupling the spatial sensing from the vehicle platform. To observe direction of arrival from a spatial view, this thesis presents a robust algorithm that enables capabilities in real-world environments previously not possible. The algorithm developed represents a given measured received signal strength pattern by the "lobes" present within the pattern without the need for modules of the antenna itself. The resulting representation enables the algorithm to perform even in the harshest of real-world environments. To demonstrate these capabilities and the versatility of this algorithm, the algorithm is implemented on thousands of received signal strength patterns generated onboard an unmanned aerial vehicle in harsh environments typical of real-world deployment. Finally, this thesis presents the development of a test platform capable of 24/7 operations in a GNSS denied environment using an infrared camera. This test platform enables flight testing of the entire system in real-world environments to better inform the system's capabilities and expected performance outside of a laboratory environment. These real-world tests, comprising of nearly 20 successful GNSS independent, autonomous signal source localizations, are crucial in informing and demonstrating the capabilities of a system as it would apply in non-laboratory conditions, adding an additional dimension over a merely theoretical analysis of different sensors and algorithms required