Lunar Node – 1: Initial Flight Results and the Role of Surface Pseudolites in Lunar Navigation

On February 22, 2024, Intuitive Machines NOVA-C landed on the lunar surface, carrying a cadre of NASA scientific and technology demonstration payloads. This mission marked the first delivery of NASA instruments to operate from the lunar surface since Apollo. One of these payloads was Lunar Node -1 (LN-1), a navigation beacon demonstration that was designed and built by NASA’s Marshall Space Flight Center. The payload’s main goal was to demonstrate and provide insight into lunar surface-based radio navigation aids. LN-1 successfully conducted multiple one-way transmissions to Deep Space Network (DSN) ground receivers using its S-band transmitter, while being disciplined by an onboard Space Chip Scale Atomic Clock. LN-1 transmitted to DSN almost daily during lunar transit and during two surface passes. These passes evaluated two navigation approaches: performance and stability of ranging using time-based transfer techniques on a cubesat size and grade platform, as well as one-way pseudonoise ranging approaches. To assess performance, the measurements were compared to independent navigation solutions such as one-way and two-way Doppler tracking and visual verification of the landing location from orbital platforms. These results are compared with ground-based testing and continued evaluation of the flight-space platform using multiple grades of oscillators for maintaining clock and frequency stability. These focus on the timing stability of platform in deep-space and variations in state determination. Given these insights, this paper provides additional description and evaluation of applying this approach in a broader lunar navigation architecture. Analysis is provided to develop timing requirements and assessment of operational scenarios, such as orbit and surface location determination. Additionally, the results support discussion as to how surface pseudolites could best be used within standard signal definitions, such as defined in the LunaNet Interoperability Specifications. Lastly, the paper will discuss challenges and next steps of a follow-on payload to LN-1.