Extension of SPIS to simulate dust electrostatic charging, transport and contamination of lunar probes

A modification of the Spacecraft Plasma Interaction Software has been undertaken under ESA contract 4000107327/12/NL/AK (SPIS-DUST). The primary goal is to provide mission designers with an engineering tool capable of predicting charged dust behavior in a given plasma environment involving a spacecraft / exploration unit in contact with complex topological features at various locations of the Moon’s surface. The tool also aims at facilitating dust contamination diagnostics for sensitive surfaces such as sensors optics, solar panels, thermal interfaces, etc. In this paper, the new user interface and the new numerical solvers developed in the frame of this project is presented. The pre-processing includes the building of a 3D lunar surface from a topology description (i.e. a point list), an interface to position the spacecraft and a merging interface for the spacecraft elements in contact with the lunar surface. Concerning the physical models, the new solvers have been developed in order to model the physics of the ejection of the dust from the soils, the dusts charging and transport in volume and the dust interaction and contamination of the spacecraft. The post-processing includes the standard outputs of SPIS for the electrostatic computation and the plasma plus dedicated instruments for the diagnosis of the dusts. A set of verification test cases are presented in order to demonstrate the new capabilities of this version of SPIS in realistic conditions

New SPIS capabilities to simulate dust electrostatic charging, transport, and contamination of lunar probes

The spacecraft-plasma interaction simulator has been improved to allow for the simulation of lunar and asteroid dust emission, transport, deposition, and interaction with a spacecraft on or close to the lunar surface. The physics of dust charging and of the forces that they are subject to has been carefully implemented in the code. It is both a tool to address the risks faced by lunar probes on the surface and a tool to study the dust transport physics. We hereby present the details of the physics that has been implemented in the code as well as the interface improvements that allow for a user-friendly insertion of the lunar topology and of the lander in the simulation domain. A realistic case is presented that highlights the capabilities of the code as well as some general results about the interaction between a probe and a dusty environment

Revisiting and modelling the woodland farming system of the early Neolithic Linear Pottery Culture (LBK), 5600–4900 B.C

International audienceThis article presents the conception and the conceptual results of a modelling representation of the farming systems of the Linearbandkeramik Culture (LBK). Assuming that there were permanent fields (PF) then, we suggest four ways that support the sustainability of such a farming system over time: a generalized pollarding and coppicing of trees to increase the productivity of woodland areas for foddering more livestock, which itself can then provide more manure for the fields, a generalized use of pulses grown together with cereals during the same cropping season, thereby reducing the needs for manure. Along with assumptions limiting bias on village and family organizations, the conceptual model which we propose for human environment in the LBK aims to be sustainable for long periods and can thereby overcome doubts about the PFs hypothesis for the LBK farming system. Thanks to a reconstruction of the climate of western Europe and the consequent vegetation pattern and productivity arising from it, we propose a protocol of experiments and validation procedures for both testing the PFs hypothesis and defining its eco-geographical area

A HYDRAULIC CONDUCTIVITY MODEL POINTS TO POST-NEOGENE SURVIVAL OF THE MEDITERRANEAN OLIVE

Research on the subfossil record and paleoecology of Olea europaea suggests a new interpretation of its history and ecology with reference to the Mediterranean climatesince the Neogene. New results are based on the wood anatomy of ancient and extant Olea and a model estimating hydraulic conductance established for wild forms belonging to Olea europaea subsp. europaea. These suggest that during glacial periods wild olive populations survived in protected microenvironments, particularly riparian habitats. Thereafter, the postglacial expansion of olive associated with climatic warming took place from these refuge areas. This new evidence suggests that the continued existence of Olea in Mediterranean areas since the Neogene was made possible either by preferential survival of Olea lineages adaptable to the Holocene climate or from enhanced adaptation to extreme environmental variation, a trait possibly originating from Tertiary predecessors and maintained in postglacial olive populations

Investigation of electrostatic potential barrier near an electron-emitting body

Electrons emitted on spacecraft surfaces can generate negative potential barriers. This may affect the equilibrium potential of the spacecraft, which can be driven more negative and jeopardise plasma measurements by repelling low energy particles. This phenomenon is investigated with the help of a numerical method based on the turning point formalism to classify orbits and which is validated with a PIC code. Comparison with spacecraft data in the magnetosphere is performed

Systèmes agrosylvopastoraux oleaster-olive greffés dans le nord du Maroc

International audienceThis book has been published by Allenvi (French National Alliance for Environmental Research) to coincide with the 22nd Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) in Marrakesh. It is the outcome of work by academic researchers on both sides of the Mediterranean and provides a remarkable scientific review of the mechanisms of climate change and its impacts on the environment, the economy, health and Mediterranean societies. It will also be valuable in developing responses that draw on “scientific evidence” to address the issues of adaptation, resource conservation, solutions and risk prevention. Reflecting the full complexity of the Mediterranean environment, the book is a major scientific contribution to the climate issue, where various scientific considerations converge to break down the boundaries between disciplines.Cet ouvrage, publié par l’Alliance nationale de recherche sur l’environnement (Allenvi) à l’occasion de la 22e Conférence des Parties de la Convention Cadre des Nations unies sur le changement climatique (COP22) de Marrakech, est le fruit de la mobilisation de chercheurs et d’universitaires des deux rives de la Méditerranée. Il constitue une synthèse scientifique exceptionnelle sur les mécanismes du changement climatique, ses impacts sur l’environnement, l’économie, la santé et les sociétés de la Méditerranée. Il représente par ailleurs un précieux outil pour élaborer des réponses, fondées sur l’ « évidence scientifique », en matière d’adaptation, de conservation des ressources, de solutions ou de prévention des risques. Mettant en exergue toute la complexité de l’environnement méditerranéen, cet ouvrage est une contribution scientifique majeure à la question climatique, au croisement des questionnements scientifiques dans une perspective de décloisonnement disciplinaire

Potential Barrier in the Electrostatic Sheath Around Geotail, Cluster and BepiColombo spacecraft

In this paper, a fully self-consistent model of the plasma around an electron emitting central body in a spherically symmetric geometry is applied to analyse the electrostatic sheath around magnetospheric spacecraft in low density plasma. For all the case studied, it is shown that non-monotonic potential with negative potential barrier can exist. The magnitude and the location of the potential barrier in regions of the magnetosphere with large Debye length plasma are discussed

Potential barrier in the electrostatic sheath around a magnetospheric spacecraft

Plasma and field measurements on board magnetospheric spacecraft can be influenced by the spacecraft potential and emitted particles such as photoelectrons and secondary electrons. There exist contradictory requirements for, on one hand, minimizing the spacecraft potential and, on the other hand, minimizing perturbations in the sheath and contamination by spacecraft-generated electrons. Assessment and mitigation of such effects therefore require improved quantitative modeling of the spacecraft electrostatic sheath. In this paper a fully self-consistent model of the plasma around an electron-emitting central body in a spherically symmetric geometry is used to analyze the electrostatic sheath around an idealized magnetospheric spacecraft. Although the model is too simplistic to allow detailed comparisons with observations, it helps to analyze the phenomenon of potential barrier occurrence and some global characteristics, which can be relevant to conductive magnetospheric spacecraft like Geotail or Cluster. It is shown that nonmonotonic potential with negative potential barrier can exist all around a positively charged spacecraft even in the case of realistic illumination pattern. The magnitude of the potential barrier in regions of the magnetosphere with large Debye-length plasma is found to be as large as a few volts negative for small positive spacecraft potential but that it quickly vanishes when the potential is increased by a few volts. Furthermore, the location of the potential barrier is found to be much more variable than previously predicted