The use of Global Navigation Satellite Systems (GNSS) to increase spacecraft autonomy for orbit determination has gained renewed momentum following the Lunar GNSS Receiver Experiment (LuGRE), which demonstrated feasible onboard GPS and Galileo signal reception and tracking at lunar distances. This work processes in-phase and quadrature (IQ) snapshots collected by the LuGRE receiver in cis-lunar space and on the lunar surface to assess multi-frequency, multi-constellation signal availability. Signals from additional systems beyond GPS and Galileo, including RNSS and SBAS constellations, are observable and successfully acquired exclusively in the recorded IQ snapshots. These observations provide the first experimental evidence that signals from multiple constellations, including systems not supported by LuGRE realtime operations, are detectable at unprecedented distances from Earth. Useful observables can be extracted from the IQ snapshots, despite minimal sampling rates, 4-bit quantization, and short durations (200 ms-2 s), through a hybrid coherent/non-coherent acquisition stage compensating for code Doppler. These observations are exploited to tune simulation tools and to perform extended simulation campaigns, showing that the inclusion of additional constellations significantly improves availability; for a 26 dB-Hz acquisition threshold, the fraction of epochs with at least four visible satellites increases from 11% to 46% of the total epoch count. These findings indicate that BeiDou, RNSS, and SBAS signals can substantially enhance GNSS-based autonomy for lunar and cislunar missions.

翻译：利用全球导航卫星系统（GNSS）提升航天器轨道确定的自主性，在月球GNSS接收机实验（LuGRE）之后获得了新的发展动力；该实验证明了在月球距离上可实现星载GPS与Galileo信号的接收与跟踪。本研究处理了LuGRE接收机在月球空间及月表采集的同相与正交（IQ）快照数据，以评估多频、多星座信号的可用性。除GPS与Galileo外，来自其他系统（包括RNSS与SBAS星座）的信号在记录的IQ快照中亦可观测并成功捕获。这些观测首次提供了实验证据，表明包括LuGRE实时运行未支持系统在内的多星座信号，在距离地球前所未有的遥远距离处仍可被探测。尽管采样率极低（4比特量化，持续时间仅200毫秒至2秒），通过采用补偿码多普勒的混合相干/非相干捕获阶段，仍可从IQ快照中提取有效观测量。这些观测结果被用于优化仿真工具并开展扩展仿真实验，结果表明引入额外星座可显著提升可用性：在26 dB-Hz捕获门限下，至少四颗卫星可见的历元比例从总历元数的11%提高至46%。这些发现表明，北斗、RNSS与SBAS信号可大幅增强月球及月球空间任务中基于GNSS的自主导航能力。