Anjali Rawat, Virginia Tech; Aaron J. Rosengren, University of California San Diego; Shane D. Ross, Virginia Tech; Bhanu Kumar, European Space Operations Centre (ESA-ESOC)
https://doi.org/10.64861/ZQCQ5523
Keywords: Cislunar, Translunar, Earth–Moon–Sun, Spatiography
Abstract:
Modern discourse, especially in policy-driven narratives, has increasingly used “cislunar” as a convenient umbrella for the broad beyond-GEO dynamical theater, often spanning libration-point neighborhoods, transfer corridors, and lunar vicinity operations. While sociolinguistically understandable, this broadening is scientifically unhelpful: it collapses dynamical handoffs that govern predictability, observability, and long-term evolution, and it blurs the distinction between regions that are Earth-organized, Moon-organized, or increasingly Sun-organized. For space domain awareness (SDA), where regime-dependent sensitivity and model fidelity directly impact catalog maintenance, search design, maneuver inference, and conjunction assessment, a physically grounded partition of the circumterrestrial environment is not a semantic luxury but an operational requirement.
This paper develops a spatiography for SDA beyond GEO by fusing two complementary viewpoints that have largely evolved in isolation. The first is a “patched” restricted three-body picture, revived from the mid-century work of Krafft Ehricke and Su-Shu Huang, in which the circumterrestrial domain is organized by two restricted three-body problems at different scales. At the smaller scale, the Earth-Moon restricted three-body problem provides a topologically faithful representation of the cislunar and circumlunar gateway geometry, including the collinear bottlenecks and associated zero-velocity surfaces that govern transit, capture, and escape relative to the Moon. At the larger scale, a Sun-(Earth-Moon) restricted three-body approximation organizes the outer stability structure of translunar motion, clarifying the handoff by which trajectories cease to be meaningfully Earth-bound and become increasingly structured by Sun-centered phase-space geometry. The patched depiction, in which Earth-Moon boundary curves are juxtaposed with the large-scale gateway, makes explicit why translunar motion is neither purely geocentric nor purely heliocentric: it is a limited-stability transitional domain, Moon-perturbed at its inner edge and increasingly sensitive near the outer gateway.
The second viewpoint is a secular perturbed-Kepler framework that supplies physically intuitive and operationally measurable “parity boundaries” for onset phenomena. First, we define the onset of the cislunar regime by the Laplace-radius criterion: the distance at which the secular contributions from lunisolar perturbations become comparable to, and then exceed, those from Earth oblateness, changing the dominant drivers of orbital plane and apsidal evolution. This boundary provides a rigorous dynamical definition of xGEO, separating a terrestrial regime where J2-driven precession dominates from a regime where the lunisolar architecture shapes long-term behavior. Second, we define the onset of translunar behavior by a lunisolar tidal parity: the distance at which the secular tidal perturbations induced by the Moon and by the Sun on a geocentric orbit are comparable in strength. Crossing this boundary corresponds to a change in the dominant external organizer of long-term evolution: lunar-tide-dominated structure yields to increasingly solar-tide-dominated structure, and geocentric motion begins to inherit the character of the Sun-Earth problem. This lunisolar tidal-parity criterion captures when translunar trajectories become dynamically more solar-conditioned even while remaining inside Earth’s broader sphere of influence.
To demarcate the circumlunar regime in a manner consistent with both dynamical systems and classical mission-design practice, we introduce a third boundary tied to the Moon’s effective sphere of influence in a patched-conics sense. Rather than relying on a single heuristic radius, we revive Battin’s refined, direction-dependent lunar sphere-of-influence construction derived from a perturbed formulation. This provides a more accurate operational divider for when Moon-centered approximations (and selenocentric tracking, covariance evolution, and maneuver modeling) become appropriate, and it complements the Earth-Moon L1/L2 gateway perspective by supplying a practical boundary for navigation and estimation.
The contribution is therefore not a new theater but a restored dynamical grammar for an old one: a unified spatiography linking (i) gateway topology from patched restricted three-body models, (ii) secular parity boundaries from perturbed-Kepler theory, and (iii) a refined circumlunar sphere-of-influence boundary relevant to operational approximations. We show how these partitions can be used to (a) classify trajectories and objects beyond GEO into regimes with distinct predictability and sensitivity profiles, (b) select appropriate force-model fidelity and reference frames for orbit determination and covariance management, and (c) design sensor tasking strategies that respect regime-dependent time scales (e.g., revisit cadence, observability windows, and growth of uncertainty). The resulting framework is intended to support SDA practitioners with physically interpretable boundaries and a principled taxonomy for beyond-GEO operations, replacing a single overloaded cislunar label with definitions that align language, dynamics, and observability.
Date of Conference: September 15-18, 2026
Track: Astrodynamics