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Session A10: Complementary PNT: PNT from LEO 2

Performance of Ground User Positioning and timing with a Multi-UAV Based OD-PNT Demonstration System
Penina Axelrad, Mikaela Dobbin, Alex Kenyon, Brian Breitsch, Dennis Akos, Jade Morton, Scott Palo, Ryan Kingsbury, Harrison Bourne, Steve Taylor, Angela Crews, Brodie Wallace, Smead Aerospace Engineering Sciences, University of Colorado Boulder; Logan Scott, Logan Scott Consulting; Khanh Pham, U.S. Space Force / Air Force Research Laboratory
Location: Ballroom B
Date/Time: Wednesday, Jun. 4, 2:50 p.m.

The OD-PNT project has introduced and investigated an on-demand, satellite-based positioning, navigation, and timing concept to provide flexible, alternative frequency, regional radio-navigation services for users in a GPS-denied environment. The core concept is to deliver an alternative PNT capability into a small region of interest (ROI), using highly autonomous, low SWaP payloads in LEO. The payloads are assumed to operate in a largely GNSS-friendly LEO environment, where they can reliably track and monitor all GNSS transmissions, precisely estimate their orbits and synchronize clocks, relying on simultaneous, clear tracking of many GPS/GNSS satellites. Using these high integrity solutions as a starting point, the payloads would autonomously generate radio-navigation signals onboard, initially locked to GPS time and orbital metrology, and then holdover this performance while producing alternative signals autonomously for up to 15 minutes without GNSS access. This time interval just exceeds the maximum length of a LEO satellite pass seen from the Earth surface. The expected performance of such a LEO-based system was evaluated based on error models and simulations.
In parallel with the simulation studies, we designed and implemented an OD-PNT demonstration system, described in previous JNC conferences, with payloads operating onboard small unmanned aerial vehicles (UAVs) tracked by static and moving ground receivers. The focus of this presentation is on the results from the demonstration system testing. Horizontal positioning of the ground receivers using only the OD-PNT signals transmitted from four UAVs travelling along LEO-like arcs across the sky, is shown to be consistent with an independent GPS real-time kinematic (RTK) system at the ~2m (RMS). The first position solution using the OD-PNT signals is achieved using only 5 seconds of sampled data.
The custom multi-UAV-based demonstration system was designed and built to experiment with and validate the signal, payload, and receiver design concepts. It provides the ability to accurately fly desired profiles, which was used in our study to emulate the motion of LEO satellites across the sky. This capability could also be used to produce test scenarios for near/far studies and testing of point-to-point ranging and time-transfer links.

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