An Architecture Study for Low-Power Satellite-Based Wildlife Tracking

Accurate satellite-based positioning has revolutionized several industries over the past two decades, from agriculture to transportation. However, conventional GNSS receivers consume significant energy and are too large for many wildlife-tracking applications, which are of critical importance to conservation efforts and our understanding of the global climate. To address this capability gap, we propose a new positioning system designed from the outset to minimize the size, mass, power, and cost 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 that detect and localize signals from very small transmitter tags. We compare a variety of signal modulations, frequencies, and positioning techniques, including both Doppler and time-of-arrival methods, and evaluate the transmitter power required, minimum number of satellites, and achievable position accuracy across a range of design parameters. Our model accounts for errors in satellite orbital state knowledge, clock offsets, frequency measurement errors, and ionospheric effects. This paper presents the results of our extensive trade study, as well as hardware field experiments performed outdoors using flight-traceable software-defined radio receivers.