Galileo disposal strategy: stability, chaos and predictability

TL;DR

This paper investigates the complex dynamical environment of the MEO region for Galileo satellites, revealing how chaos and resonances influence disposal strategies and proposing criteria for optimal satellite end-of-life management.

Contribution

It introduces a systematic approach to analyze the stability and chaos in MEO, providing new criteria for effective satellite disposal strategies based on resonance structures.

Findings

MEO region exhibits a rich structure of secular resonances causing chaos.

Resonance analysis can identify stable and unstable zones for satellite disposal.

Explicit criteria for disposal strategies are derived from fixed point analysis.

Abstract

Recent studies have shown that the medium-Earth orbit (MEO) region of the Global Navigation Satellite Systems is permeated by a devious network of lunisolar secular resonances, which can interact to produce chaotic and diffusive motions. The precarious state of the four navigation constellations, perched on the threshold of instability, makes it understandable why all past efforts to define stable graveyard orbits, especially in the case of Galileo, were bound to fail; the region is far too complex to allow of an adoption of the simple geosynchronous disposal strategy. We retrace one such recent attempt, funded by ESA's General Studies Programme in the frame of the GreenOPS initiative, that uses a systematic parametric approach and the straightforward maximum-eccentricity method to identify long-term stable regions, suitable for graveyards, as well as large-scale excursions in eccentricity, which can be used for post-mission deorbiting of constellation satellites. We then apply our new results on the stunningly rich dynamical structure of the MEO region toward the analysis of these disposal strategies for Galileo, and discuss the practical implications of resonances and chaos in this regime. We outline how the identification of the hyperbolic and elliptic fixed points of the resonances near Galileo can lead to explicit criteria for defining optimal disposal strategies.