Abstract:
Accurate satellite based positioning revolutionized several industries over the past two decades from agriculture to transportation. However, conventional GNSS receivers consume significant amounts of energy and are too large for many applications, including wildlife-tracking which is critical for conservation efforts and improving our understanding of the global climate. To address this capability gap, we propose a new positioning system to minimize the size, mass, power, and size of the terrestrial tracking device. We analyze, through extensive modeling and simulation, a mission concept that relies on space-based receivers hosted on a constellation of small satellites in low-Earth orbit (LEO) that detect and localize signals from very small transmitter tags. We compare a variety of positioning techniques, including both Doppler and time-of-arrival methods, and evaluate the achievable position accuracy across a wide range of design parameters. Our model also accounts for errors in satellite orbital state knowledge, clock offsets, frequency measurement errors, and ionospheric effects. This thesis will present the results of our end to end system architecture modeling along with a trade study, unified positioning algorithms for doppler and time of arrival measurements, and an accurate state estimation algorithm for satellites in low earth orbit.

Committee:
Dr. Zachary Manchester (advisor)
Dr. Michael Kaess
Kevin Tracy