Development of a Lunar Surface Navigation Pseudolite Testbed

As the successful initial launch of the NASA Artemis program begins the process of returning astronauts to the moon and generates new commercial opportunities, Lunar navigation remains a critical challenge. Multiple proposals for Lunar Navigation Satellite System architectures have been developed to support exploration, science, and commercial endeavors on the lunar surface. However, these constellations require significant fiscal budgets, Earth-based ground station support, and have limited initial horizontal ranging performance, reducing their capabilities on the lunar surface. We propose a novel lunar surface-based Position, Navigation, and Timing (PNT) and emergency broadcast pseudolite system to support regional operations over exploration critical areas. This research is focused on developing a lunar pseudolite testbed with two primary objectives: testing lunar surface communication and radionavigation techniques and characterizing the performance of low-cost, commercially available radio frequency (RF) hardware alternatives for supporting lunar operations. The work is comprised of four primary phases: (1) development and testing of the communication and radionavigation protocols in a benchtop environment, (2) integration of terrestrial pseudolite testbed, (3) over-the-air demonstrations with multiple pseudolite units, and (4) characterizing the relative range, absolute positioning, and time synchronization performance with different software defined radios and reference oscillators. Pseudorandom noise (PRN) code ranging is the baseline relative positioning methodology, with tests leveraging a variety of PRN codes developed for both satellite and pseudolite navigation systems. Signal tracking, pseudorange estimation, and absolute position estimates will be obtained by modifying open-source Global Navigation Satellite System (GNSS) software engines. Hardware tests will be conducted to characterize the short- and long-term clock positioning errors with different families of oscillators.