Time-Series-Driven Lunar Link Availability and Performance at Ka- and Q-Band

Future lunar communications networks must coordinate direct-to-Earth and relay paths while accounting for time-varying geometry and atmospheric fading at terrestrial terminals. This study develops a time-series framework for evaluating these effects at 19.7 GHz (Ka band) and 39.4 GHz (Q band) using Alphasat measurements collected at Tito Scalo and Spino d’Adda from 2015 through 2024. The measured attenuation is separated into gaseous, cloud, rain, and scintillation components, and component-specific elevation scaling is applied along direct lunar-surface and representative near-rectilinear halo-orbit relay geometries generated using NASA/JPL SPICE. Synchronized site and path selection preserves the chronology required to calculate attenuation CCDFs, fade durations, fade-event counts, and operational availability. The results show that Q band, as expected, requires greater atmospheric margin when compared to Ka band, while Tito Scalo–Spino d’Adda diversity reduces severe attenuation exceedance and persistent fades for both frequencies. Satellite relay access raises the geometry-limited availability from approximately 15–18% for the direct lunar-surface path to 30–35%; combined site and direct-lunar-or- satellite-relay selection reaches approximately 37–38% for the adopted geometry. The framework demonstrates how measured terrestrial propagation time series can support first- and second-order assessment of candidate lunar ground-network architectures.