Аuthors

Neryadovskaya D. V.

Moscow Aviation Institute (National Research University), 4, Volokolamskoe shosse, Moscow, А-80, GSP-3, 125993, Russia

e-mail: neryadovskayadv@yandex.ru

Abstract

This paper investigates the dynamics of a tether system anchored to the   or   libration point of the Mars–Phobos system, designed for collecting regolith from the surface of Phobos. This system offers a promising approach for interacting with the surface of a small celestial body without requiring a full landing, a significant advantage given the weak gravity and substantial dynamical perturbations that complicate conventional landing and sampling operations. Particular focus is placed on the motion of the spacecraft connected to the tether and the feasibility of controlling its position relative to Phobos' surface. A control law is proposed that incorporates the viscoelastic properties of the tether material, perturbations from Mars'   polar oblateness, and the eccentricity of Phobos' orbit. These factors are integrated into the mathematical model to provide a more accurate representation of the system dynamics near the libration points. The proposed control law enables two primary operational modes. The first mode is stabilization relative to the equilibrium position, in which the spacecraft is maintained at a prescribed position relative to either the libration point or the target surface region. The second mode, controlled swinging, involves directed oscillatory motion above the surface, facilitating displacement between different regions without direct landing. Numerical simulations demonstrate that for a positive value of the control parameter (cross-coupling parameter), the system's oscillations decay over time, indicating stable, controlled motion. Conversely, a negative value of this parameter leads to unbounded oscillation growth, indicating a loss of stability. Qualitatively identical results were observed for both the and libration points, demonstrating the universality of the proposed control law and its applicability across various configurations of the Mars–Phobos tether system.

Keywords:

tether system; libration point; control; stabilization; swinging

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