Being Earth’s only natural satellite, the moon is crucial for human space exploration and serves as a vital base for additional deep space endeavors. Cislunar space represents an extensive domain for expanding human habitation beyond terrestrial land and oceans. The pursuit, building, and advancement of cislunar space have escalated the need for cislunar navigational capabilities. Currently, GNSS navigation technology has been well-established for Earth and near-Earth regions and is now being extended to encompass the cislunar realm. Concurrently, the progress in small satellite technology presents fresh opportunities for the rapid and effective implementation of small satellite navigation networks. Addressing cislunar navigation needs, this document suggests creating a navigation system in small space using BDS (BeiDou Navigation Satellite System) time-transfer technology on a compact satellite platform in earth-moon libration point orbits. A variety of orbital paths, such as DRO (Distant Retrograde Orbit) and NRHO (Near Rectilinear Halo Orbit), are employed to form a navigational constellation under the framework of a small satellite platform operating in earth-moon libration point orbits; BDS timing is utilized to compensate for limited payload capacity on small satellites as well as limitations in star clock accuracy. This paper presents the design architecture analysis of such a cislunar space small-satellite navigation system employing BDS time-transfer technology while

This study focuses on the nonlinear departure dynamics of spacecraft from the Near Rectilinear Halo Orbit (NRHO) to the outer regions of Selenocentric Space. By carefully selecting the combination of orbital parameters and the order of the evaluation process, it becomes possible to precisely identify the divergence moment and to reliably classify the subsequent dynamical space. An empirical divergence detection algorithm is proposed by integrating multiple parameters derived from multi-body dynamical models, including gravitational potentials and related quantities. In an applied analysis using this method, it is found that the majority of perturbed trajectories diverge into the outer Earth–Moon Vicinity, while transfers into the inner Earth–Moon Vicinity are relatively limited. Furthermore, transfers to Heliocentric Space are found to be dependent not on the magnitude of the initial perturbation but on the geometric configuration of the Sun, Earth, and Moon during the transfer phase. The investigation of the Sun’s initial phase reveals a rotationally symmetric structure in the perturbation distribution within the Sun–Earth–Moon system, as well as localized conditions under which the destination space varies significantly depending on the initial state. Identifying the divergence moment allows for comparative evaluation of the spacecraft’s nonlinear dynamical state, providing valuable insights for the development of safe and efficient transfer strategies from selenocentric or

Satellites deployed from the Gateway in a Near Rectilinear Halo Orbit (NRHO) must be safely delivered their desired destinations in cislunar space and beyond. The presence of simultaneously significant gravitational forces from the Moon, the Earth, and the Sun, along with the absence of atmospheric drag, complicates the mission design problem for cubesats deployed from the Gateway. The current investigation defines candidate green zones for safe satellite deployment, allowing a passive departing spacecraft to avoid recontact with the Gateway as it departs the NRHO vicinity.

The aim of this paper is to revise the suitability of Near- Rectilinear Halo Orbits (NRHOs) as long-term destinations for a new crew-tended space station; referred here as Deep Space Gateway (DSG). NRHOs are a subset of the halo families characterized by promising stability properties. The document presents the formal definition and identification of NRHOs, as in the CR3BP model. Dynamical substitutes of the NRHOs are also refined in the Bi-Circular Model (BCM) by means of a multiple shooting method. Key features such as lunar south-pole coverage, station keeping requirements and accessibility of the orbit are then analysed. Several maintenance strategies based on three different underlying principles are considered and, finally, the accessibility of NRHOs from the Earth and polar Moon orbits is investigated.

Motivated by the near-future re-exploration of 1 the cislunar space, this paper investigates dynamical substitutes of the Earth-Moon’s resonant Near-Rectilinear Halo Orbits (NRHOs) under the Elliptic-Circular Restricted Four-Body Problem formulation of the Earth-Moon-Sun system. This model considers that the Earth and Moon move in elliptical orbits about each other and that a third body, the Sun, moves in a circular orbit about the Earth-Moon barycenter. By making use of this higher-fidelity dynamical model, we are able to incorporate the Sun’s influence and the Moon’s eccentricity, two of the most significant perturbations of the cislunar environment. As a result of these perturbations, resonant periodic NRHOs of the Earth-Moon Circular Restricted Three-Body Problem (CR3BP) are hereby replaced by two-dimensional quasi-periodic tori that better represent the dynamical evolution of satellites near the vicinity of the Moon. We present the steps and algorithms needed to compute these dynamical structures in the Elliptic-Circular model and subsequently assess their utility for spacecraft missions. We focus on the planned orbit for the NASA-led Lunar Gateway mission, a 9:2 synodic resonant L2 southern NRHO, as well as on the 4:1 synodic and 4:1 sidereal resonances, due to the proximity to the nominal orbit and their advantageous dynamical properties. We verify that the dynamical equivalents of these orbits preserve key dynamical attributes such as eclipse avoidance and near-linear

After completion of a resupply mission to NASA's proposed Lunar Orbital Platform - Gateway, safe disposal of the Logistics Module is required. One potential option is disposal to heliocentric space. This investigation includes an exploration of the trajectory escape dynamics from an Earth-Moon Near Rectilinear Halo Orbit (NRHO) and applies these insights to the design of a low-cost heliocentric Logistics Module disposal option. The effects of the solar gravitational perturbations are assessed in both the bicircular restricted 4-body problem and in an ephemeris force model.

low-energy cislunar orbit transfers between a near-rectilinear halo orbit (NRHO) and a distant retrograde orbit (DRO) and orbit maintenance for a period In orbital mechanics, a distant retrograde orbit (DRO) is a highly stable retrograde orbit around the smaller of two bodies, passing outside the system's L1 and L2 Lagrange points. It is typically discussed in spacecraft orbits of natural satellites. The craft orbit is retrograde: moving in the direction opposite to the direction in which the moon orbits the planet. The orbit is distant: it passes In orbital mechanics, a distant retrograde orbit (DRO) is a highly stable retrograde orbit around the smaller of two bodies, passing outside the system's L1 and L2 Lagrange points. It is typically discussed in spacecraft orbits of natural satellites. The craft orbit is retrograde: moving in the direction opposite to the direction in which the moon orbits the planet. The orbit is distant: it passes above the Lagrange points, rather than being near the moon. Considering more distant orbits, the synodic period gets longer and approaches that of the moon going around the planet. The sidereal period can become much longer than the moon's orbital period. A hypothetical example with Europa has a sidereal period about eight times the orbital period of Europa. DROs have been researched for several decades. In April 2022, CNSA's Chang'e 5 orbiter became the first to enter the orbit, followed by NASA's Orion Spacecraft during the Artemis 1 mission which entered in November 2022. Two more CNSA spacecraft, DRO A and B, attempted in 2024, but were left in lower orbits due to a failure of the YZ-1S upper stage. Despite the earlier problems, by August 2024 the DRO A and B appeared to have reached their orbit. The stability of a DRO is defined in mathematical terms as having very high Lyapunov stability, where an equilibrium orbit is "locally stable if all solutions which start near the point remain near that point for all time". On…

Near Rectilinear Halo Orbits (NRHOs) are stable or nearly stable orbits that are defined as part of the L1 and L2 halo orbit families in the circular restricted three-body problem. Within the Earth-Moon regime, the L2 NRHOs offer candidate trajectories for the upcoming Gateway mission. The spacecraft, however, incurs continuous deviations due to unmodeled forces and orbit determination errors in this dynamically sensitive region. The current investigation focuses on a technique to maintain the spacecraft near a virtual reference orbit despite these uncertainties. For the stationkeeping scheme, flow dynamics in the region are utilized to categorically identify appropriate maneuver and target locations. The investigation reflects the impact of various factors on maneuver cost and efficacy. Additional feedback control is applied for phasing constraints.

Optimisation des opérations de Rendez-vous et conception GNC pour les opérations de proximité sur une orbite cislunaire NRHO Le projet Deep Space Gateway (DSG) se présente comme l’une des plus prometteuses collaborations internationales de la prochaine décennie. Il inclut la mise en place d’un avant-poste spatial dans un environnement cislunaire, servant de relais pour des missions (habitées ou non) d’exploration. L’orbite cible pour la station sera une Near Rectilinear Halo Orbit (NRHO) située a proximité d’un point de Lagrange Terre-Lune (EML). Les activités opérationnelles de Rendez-vous et de Docking (RVD) sont de la plus haute importance afin de mener à bien l’assemblage de la station puis les diverses opérations de maintenance. Le module Orion sera en charge de ces opérations et devra également assurer les missions de ravitaillement et les vols habités au départ ou à destination de la DSG. La littérature au sujet des questions de RVD dans le problème à deux corps sur des Orbites terrestres ou lunaires basses quasi-circulaires (LEO et LLO respectivement) est très vaste et les cas d’application pratique ne manquent pas : citons par exemple les RVD manuels des missions Apollo. Cependant, la complexité dynamique des modèles a trois corps ou plus fait qu’à ce jour aucun RVD l n’a été réalisé dans des régions proches des points de Lagrange, où les modèles képlériens ne sont plus applicables. Malgré la présence de nombreuses publications sur les trajectoires et orbites a proximité des points de Lagrange et des transferts dans le domaine cislunaire, la communauté scientifique ne dispose à ce jour que de très peu de résultats sur les opérations de RVD dans les environnements non-képlériens. L’intérêt suscité par la mise en route du projet DSG et des premiers vols du module Orion a néanmoins vivement relancé l’intérêt de la communauté sur le sujet. L’ISAE-Supaéro a développé avec ses partenaires (parmi lesquels l’Agence Spatiale Européenne, et Airbus Defence and Space) des outils semi-analytiques de modélisation et de calcul d’orbites de type NRHO, DRO, Lyapunov, Halo et Lissajou à proximité des points de Lagrange dans le problème circulaire restreint a trois corps (CR3BP). Ceci constitue un solide point de départ pour étendre les stratégies de RVD aux environnements cislunaires avec prise en compte des contraintes matérielles et opérationnelles des missions à venir. Ce doctorat propose le développement d’outils théoriques et de méthodes numériques de mécanique orbitale permettant d’exploiter les spécificités de l’astrodynamique non-linéaire pour réaliser des opérations de RVD en milieu cislunaire. Il s’agira de définir les contraintes propres à ce nouveau cadre opérationnel et de proposer des modèles répondant aux attentes des agences spatiales internationales et de l’industrie pour préparer l’exploration spatiale de demain. Nous nous intéresserons à des opérations de RVD entre la DSG, cible du rendez-vous et placée sur une orbite NRHO autour de EML2, et des véhicules provenant d’orbites terrestres. Nous proposerons en particulier un design de système de Guidage, Navigation et Contrôle (GNC) qui s’appuiera sur les capacités technologiques actuelles et à venir des senseurs et actionneurs embarqués.

observations, while near-rectilinear halo orbits (NRHOs) provide long-term stability and continuous communication with Earth, making them well suited A subsatellite, also known as a submoon, moonlet or informally a moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet. It is inferred from the empirical study of natural satellites in the Solar System that subsatellites may be rare, albeit possible, elements of planetary systems. In the Solar System, the giant planets have large collections of natura There is a possible detection of a ring system around Saturn's natural satellite Rhea that led to calculations that indicated that satellites orbiting Rhea would have stable orbits. The rings suspected were thought to be narrow, a phenomenon normally associated with shepherd moons; however, targeted images taken by the Cassini spacecraft failed to detect any subsatellites or rings associated with Rhea, at least no particles larger than a few millimeters, making the chance of a ring system around Rhea slim.