Plasmasphere and Ionosphere characterization from cislunar environment.

GNSS signals serve as signals of opportunity for Earth observation, characterizing the dispersive effects of free electrons in the ionosphere and plasmasphere, a major source of positioning bias via group delay, phase advance, and Total Electron Content (TEC)-driven distortion. This work presents the methodology behind the first-ever catalogue of dispersive GNSS occultation arcs observed across cislunar space during the Lunar GNSS Receiver Experiment (LuGRE), a NASA-ASI mission demonstrating lunar-surface positioning, navigation, and timing through GNSS. A dedicated pipeline identifies and classifies crossings as ingress, egress, or tangent arcs using dual-frequency GPS/Galileo observables and Slant TEC, Rate of TEC (ROT), and ROT Index (ROTI); results are validated via geometry-based grazing-altitude analysis. The method identified 229 dispersive arcs, achieving 95.6% agreement with the geometric reference, offering a resource to study Earth’s plasma environment from cislunar space.