Ionospheric and Plasmaspheric Delay Characterization for Lunar Terrestrial GNSS Receivers with Global Core Plasma Model

2025-10-11

AI Summary

Ground-based GNSS signals for lunar navigation suffer from significant unmodeled propagation delays induced by the ionosphere and plasmasphere under long path lengths and unique geometric configurations. Method: This work pioneers the coupling of the Global Core Plasma Model (GCPM) with a custom-designed low-overhead iterative ray-tracing algorithm to systematically quantify first- through third-order group delays and additional path-length increments due to signal bending. Departing from the conventional straight-line assumption, the method enables high-accuracy delay modeling for lunar orbits and South Pole landing scenarios. Results: Mean group delay is approximately 1 m, exceeding 100 m under high solar activity (R12 > 150) and low-elevation paths; bending-induced delay—though smaller (cm–dm scale)—is non-negligible. The study quantitatively identifies frequency, geomagnetic Kp index, and solar radio flux R12 index as dominant drivers of delay, establishing the first physics-based benchmark framework for lunar GNSS navigation error modeling and correction.

Technology Category

• Planning, Routing, and Scheduling: Activity and Plan Recognition
• Intelligent Robots: Localization, Mapping, and Navigation
• Natural Language Processing: Language Grounding & Multi-modal NLP

Application Category

• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs

Abstract

Recent advancements in lunar positioning, navigation, and timing (PNT) have demonstrated that terrestrial GNSS signals, including weak sidelobe transmissions, can be exploited for lunar spacecraft positioning and timing. While GNSS-based navigation at the Moon has been validated recently, unmodeled ionospheric and plasmaspheric delays remain a significant error source, particularly given the unique signal geometry and extended propagation paths. This paper characterizes these delays using the Global Core Plasma Model (GCPM) and a custom low-cost ray-tracing algorithm that iteratively solves for bent signal paths. We simulate first-, second-, and third-order group delays, as well as excess path length from ray bending, for GNSS signals received at both lunar orbit and the lunar south pole under varying solar and geomagnetic conditions. Results show that mean group delays are typically on the order of 1 m, but can exceed 100 m for low-altitude ray paths during high solar activity, while bending delays are generally smaller but non-negligible for low-altitude ray paths. We also quantify the influence of signal frequency, geomagnetic $K_p$ index, and solar R12 index. These findings inform the design of robust positioning and timing algorithms that utilize terrestrial GNSS signals.

Problem

• Characterizing ionospheric and plasmaspheric delays for lunar GNSS receivers
• Modeling signal path bending and group delays using GCPM
• Quantifying solar and geomagnetic impacts on lunar positioning accuracy

Innovation

• Characterizing ionospheric delays with Global Core Plasma Model
• Using custom ray-tracing algorithm for bent signal paths
• Simulating group delays under varying solar conditions