Design of Phasing Trajectories From a Low Lunar Orbit To a Near Rectilinear Halo Orbit

The paper presents three different approaches to the design of a phasing trajectory in a cislunar environment, where the third body perturbation is considered non-negligible. The working framework is the one proposed by the ESA’s Heracles mission in witch the passive target spacecraft -LOP-G- is orbiting on a Near Rectilinear Halo Orbit and the Lunar Ascent Element must reach that orbit from a Low Lunar Parking Orbit to start the rendezvous procedure. In this scenario the authors propose three different ways to design such phasing manoeuvre under the Circular Restricted Three Body Problem hypotheses: Lambert/Differential correction, Hohmann/Differential correction and Optimization. The three approaches are compared in therms ofV consumption, accuracy and time of flight. Finally, a selected solution is also validated under the Restricted Elliptic Three Body Problem Hypotheses

Thrust Expenditure Feasibility Analysis for Rendezvous Operations in Cis-Lunar Space

In recent years, Moon exploration has become a primary objective within most space agencies worldwide. The Lunar Space Gateway program ARTEMIS (or LOP-G) is an example of mission proposal for technology feasibility in terms of autonomous (and later manned) operations of a space station orbiting the L2 Earth – Moon Lagrangian point. Rendezvous and docking (berthing) are tasks that are envisioned to be performed fully autonomously. The focus of the paper falls in this category, whereby an active module called Lunar Ascender Element (LAE), returning from the lunar surface, shall be able to operate an automatic rendezvous mission with the LOP-G station. The paper concentrates, in particular, with the feasibility analysis needed to assess the engines’ thrust capabilities to provide appropriate propulsion for open loop and closed loop control during rendezvous. The capability of providing the desired amount of thrust is not only linked to the actual guidance commands, but also to the nature of the motors. The rendezvous maneuver sequence, dynamics and hold points are first defined, and the thrust distribution and configuration detailed for the specific mission. The guidance logics are described, and the implementation of a passively safe trajectory outlined. Based on the dynamic model of the system, and the assumed actuator model, the main causes of unfeasibility are listed. The paper continues by analyzing the sensitivity of the thrust profile at each motor with respect to the control allocation algorithm, the duration of the maneuver, the duration of each impulse (assuming a two-impulse maneuver), and the location of the berthing port within a selected near rectilinear halo orbit around the Moon. The tests take into account how the parameters influence the Delta V required to perform the mission. The authors wish to remark that this analysis is critical to the design of rendezvous and berthing (docking) operations, since feasibility is necessary for the success of the mission, and it provides a structured computation of a realistic parameter space in the relative motion in the presence of a third body perturbation

A model for liquid-striped liquid phase separation in liquids of anisotropic polarons

The phase separation between a striped polaron liquid at the particular density and a high density polaron liquid is described by a modified Van der Waals scheme. The striped polaron liquid represents the pseudo gap matter or Wigner-like polaron phase at 1/8 doping in cuprate superconductors. The model includes the tendency of pseudo- Jahn-Teller polarons to form anisotropic directional bonds at a preferential volume with the formation of different liquid phases. The model gives the coexistence of a first low density polaron striped liquid and a second high density liquid that appears in cuprate superconductors for doping larger than 1/8. We discuss how the strength of anisotropic bonds controls the variation the phase separation scenarios for complex systems in the presence of a quantum critical point where the phase separation vanishes.Comment: 10 pages, 3 figure

Analysis of an Experimental Cortical Network: i) Architectonics of Visual Areas 17 and 18 After Neonatal Injections of Ibotenic Acid; Similarities with Human Microgyria

Lesions of cortical areas 17 and 18 have been produced in newborn kittens by local injections of the excitotoxin ibotenic acid (ibo). Twenty-four hours after an injection on postnatal days 2 or 3, the gray matter of areas 17 and 18 near the center of the injection appears completely destroyed, with the exception of a one-to-two cell-thick layer at the bottom of layer I. Intact migrating neurons and radial glia can be found light- and electron-microscopically in the region affected. During the following weeks a several hundred micron thick cortex reforms. In the adult, this cortex consists of superficial layers I, II and III as proven by cytoarchitectonics, continuity with the corresponding layers of the normal cortex and cellular composition. We believe that the recovery is due to completion of migration by neurons spared by the ibo injection. More severe destruction of cerebral cortex, i.e. complete loss of the neuronal layers or their reduction to a few cell-thick mantles can be obtained with ibo injections at the end of the second or, respectively, first postnatal week. Severity of lesion also depends on the dose of ibo injected. There are interesting similarities between the ibo-injured cortex and two human neocortical displasias: microgyria and ulegyria

Analysis of an Experimental Cortical Network: ii) Connections of Visual Areas 17 and 18 After Neonatal Injections of Ibotenic Acid

Lesions of cortical areas 17 and 18 were produced in newborn kittens by local injections of the excitotoxin ibotenic acid. In the adult this results in a microcortex which consists of superficial layers I, II and III, in the absence of granular and infragranular layers. Horseradish peroxidase, alone or wheat germ agglutinin conjugated, was injected in the microcortex or in the contralateral, intact areas 17 and 18. The microcortex maintains several connections characteristic of normal areas 17 and 18 of the cat. It receives afferents from the dLGN, and several visual areas of the ipsilateral and contralateral hemisphere. However, it has lost its projections to dLGN, superior colliculus, and, at least in part, those to contralateral visual areas. Thus some parts of the microcortex receive from, but do not project into, the corpus callosum. In addition, the microcortex maintains afferents from ipsilateral and contralateral auditory areas AI and AII which are normally eliminated in development

Bearings-Only Guidance in Cis-Lunar Rendezvous

The current plans of returning to the Moon involve rendezvous and docking/berthing operations with a passive permanent station, whose targeted orbit is a Near Rectilinear Halo Orbit. In this work a preliminary guidance algorithm for the close-range rendezvous phase is proposed, based on a sample mission application, assuming the active chaser can measure relative angles only to the target. The navigation performance is affected by the maneuvers performed because their execution is necessary to make the problem observable. The relative motion equations with third body perturbation are considered directly in the guidance algorithm, with the additional aim of improving observability during the approach trajectory. Numerical simulations are presented to validate the proposed methodology