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Session E2: LEO for Positioning, Navigation, and Timing

Xona PULSAR User Performance Assessment
Thyagaraja Marathe, Tyler G.R. Reid, Andrew Neish, Kazuma Gunning, Simon Banville, Xona Space Systems
Date/Time: Wednesday, Sep. 18, 2:35 p.m.

Global Navigation Satellite Systems (GNSS), including GPS, are an invisible utility that provide Position, Navigation, and Timing (PNT) services to more than 6.4 billion devices, globally. These devices operate in a diverse set of downstream industries including automotive, maritime, aviation, infrastructure, and robotics. GNSS now faces more challenges than ever, with growing threats from Radio Frequency (RF) interference and cybersecurity that limit service availability and integrity. In response to these challenges, Xona Space Systems is developing an alternate global PNT service to provide the navigation and timing performance required to support current and future demands. Xona’s global PNT service, named PULSAR, will be delivered though a constellation of near 260 small satellites in Low Earth Orbit (LEO). PULSAR satellites will transmit modern navigation signals that yield significant enhancement in position accuracy, availability, and security compared to the state-of-the-art. Xona’s first demonstration satellite was launched in May 2022 on the SpaceX Transporter-5 mission. This marks the first time a commercial company has launched a dedicated PNT mission.

We present relevant trades in a commercial LEO PNT system and the resulting expected user performance. For the constellation, this includes trades on altitude, number of satellites, and elevation mask sensitivity. Satellite passing time varies as a function of the orbit height. Satellites in the LEO orbits travel from horizon to horizon in about 10-15 minutes compared to GNSS in MEO at 4-6 hours. We also explore orbital configurations including Walker Delta and Walker Star configurations to provide different levels of coverage ranging from visibility for GNSS augmentation to positioning capability with comparable dilution of precision to GPS. These results motivate a staged roll out plan to first deliver GNSS enhancement and time transfer services as a steppingstone to the ultimate constellation delivering full, independent PNT. As such, Xona’s first phase deployment targets the launch of approximately 32 satellites to provide a 1-in-view LEO GNSS enhancement service over mid-latitude population centers. Ultimately, the target is a constellation of near 260 satellites to deliver GPS-level satellite visibility and dilution of precision in the long-term. These satellites are designed for on-orbit flexibility and faster refresh cycles to keep pace with ever increasing PNT demands. We showcase the expected coverage and PNT performance at each stage of deployment.

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