Assessment of GNSS Availability in Cis-Lunar Space Using LuGRE IQ Samples: Experimental Results, Simulations and New Records

Recent advances in lunar exploration have renewed interest in exploiting Global Navigation Satellite System (GNSS) for navigation in cis-lunar space and on the lunar surface. In this context, the pioneering Lunar GNSS Receiver Experiment (LuGRE) experiment produced an unprecedented dataset of raw observables and short In-Phase Quadrature (IQ) batches on the L1 and L5 bands, enabling analyses that extend well beyond the payload's operational capabilities. This work presents post-processing results from dual-frequency IQ batches collected by the LuGRE payload, demonstrating the presence of multi-frequency signals from Global Positioning System (GPS), Galileo, Regional Navigation Satellite System (RNSS), and Satellite-based Augmentation System (SBAS). Despite their lower fidelity compared to the operational tracking channels, these batches allow us to report - for the first time - the reception and acquisition of Wide Area Augmentation System (WAAS), Algerian Satellite Based Augmentation System (AL-SBAS), European Geostationary Navigation Overlay Service (EGNOS), and BeiDou signals from the lunar surface, as well as the first recorded reception of Indian Regional Navigation Satellite System (IRNSS) (NavIC), Quasi-Zenith Satellite System (QZSS), MTSAT Satellite Augmentation System (MSAS), BeiDou SBAS (BDSBAS), and BeiDou signals from lunar orbit. Estimated Carrier to Noise Density Ratio (C/N0) values provide insight into propagation conditions and serve as reference data for calibrated simulations of lunar operations. A simulation tuned using the C/N0 values retrieved from the low-fidelity IQ batches indicates improved signal availability and reduced Geometric Dilution Of Precision (GDOP) when RNSS and SBAS constellations are included. The detection of strong SBAS signals on the lunar surface further suggests potential applications for future lunar navigation, provided that suitable corrections and precise ephemerides are available.