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A key aspect of dust adhesion to space equipment is the accumulation of charge under the space plasma environment. Recent models and experiments show possible negative charging of dust grains under vacuum ultra-violet (VUV) illumination. Macroscopic potential measurements conducted during a test campaign show that both positive and negative average charging can be reached under VUV mymargin irradiation pending on vacuum chamber configuration, suggesting that both situations can exist at lunar surface. Simulations of dust charging at microscopic scale are conducted with the SPIS software to evaluate electrical charge and electric field amplifications induced by the granular structure of the lunar regolith. A multilayer pile of dust is modeled under lunar conditions. Grains from the first two layers tend to microscopically acquire both negative and positive charge patches when illuminated with a 45° VUV incidence angle, this differential charging being less pronounced under normal incidence angle. It is also found that dust deeply buried in the lunar soil may charge more negative due to the collection of environmental electron only. This effect is thought to reinforce the grain supercharging model presented by other authors. We show, however, that such charge development may be limited by electrical conduction pending on dust electrical properties.

International audience; To represent the time spent by space materials on ground before launch, the measurement of secondary electron emission properties is performed after long duration exposure to ambient atmosphere and humidity. The observed change with respect to pristine samples have an impact on the estimation of worst-case surface charging levels in geostationary orbit, especially for a spacecraft in eclipse. It is therefore recommended to adequately outgas the samples with respect to the expected flight conditions and ageing effects.

This paper defines a series of severe plasma environments in terms of spacecraft surface charging in geostationary orbit. In-flight plasma measurements are used to extract environments associated with large absolute spacecraft potentials and fluxes. An exhaustive list of events is selected over 15 years of Los Alamos National Laboratory data between the 1990s and 2000s. Electron spectra are compared to the literature and guidelines, especially the strong event measured by the Spacecraft Charging at High Altitude satellite in 1979. The impact on a telecommunications spacecraft of such charging environments is simulated numerically with the Spacecraft Plasma Interaction Software. The correlation between the model results and the instrument data indicates that the numerical approach is reliable for estimating charging risks in operational conditions. Measured environments are ranked on their susceptibility to generate significant charging and electrostatic discharge risks.

The internal magnetic field of Jupiter is known to be highly multi-polar, not only from the direct measurements performed by the Voyager and Pioneer probes but also from the unusually complex shape of the northern auroral oval. The limited amount of data obtained from the Voyager and Pioneer flybys do not permit accurate determination of the topology of the magnetic field, as they barely constrain, even the octupole contribution to the field. This does not allow one to reproduce the position of the auroras nor satisfactorily explain the shape and frequency range of the Jovian radio arcs. Successive attempts have been made to constrain the higher– degree field using the position of the Io auroral footprint where the auroras are due to currents generated close to Io and carried along the magnetic field lines. Thus, the auroral spots should map to Io’s orbit. VIPAL, the latest model of this kind is a 5th degree model. However, the VIPAL model was limited by three factors: the main constraints come from a unique L-shell, the difficulty of mixing Jovigraphic and magnetic data, and the non-linearity of the problem. These issues lead to numerically demanding computations, with the scale of computation increasing as the square of the model degree. We have developed a new method for computing the magnetic field using in-situ and auroral constraints (ISaAC) which we have applied to the computation of the Jovian magnetic field, based on Voyager, Pioneer, Galileo magnetic measurements and constrained by Io’s, Europa’s and Ganymede’s auroral footprint locations.

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.

[1] The goniopolarimetric methods, also known as direction finding, are powerful methods which are used to obtain the intensity, the polarization, and the position of the low-frequency radio sources in the sky plane. These methods have been applied to several auroral sources and to the solar wind sources. The results obtained by these methods have allowed us to drastically improve our understanding of the processes occurring in the concerned regions. These methods are only valid for point source, or weak extended sources, whereas in many cases extended or multiple sources are expected. Some methods allow to obtain the characteristic size of the source, but not its shape or the intensity distribution inside it. In the present paper a method is proposed which can determine the intensity distribution inside an extended, but one-dimensional source and which can be applied to observations of two close sources. Application to simulated auroral and solar wind emissions are also presented.

Context. Since the first extra-solar planet discovery in 1995, several hundreds of these planets have been discovered. Most are hot Jupiters, i.e. massive planets orbiting close to their star. These planets may be powerful radio emitters.Aims. We simulate the radio dynamic spectra resulting from various interaction models between an exoplanet and its parent star, i.e. exoplanet-induced stellar emission and three variants of the exoplanet’s magnetospheric auroral radio emission (full auroral oval, active sector fixed in longitude, and active sector fixed in local time).Methods. We show the physical information about the system that can be drawn from radio observations, and how this can be achieved. This information includes the magnetic field strength and the rotation period of the emitting body (planet or star), the orbital period, the orbit’s inclination, and the magnetic field tilt relative to the rotation axis or offset relative to the center of the planet. For most of these parameters, radio observations provide a unique means of measuring them.Results. Our results should provide the proper framework of analysis and interpretation for future detections of radio emissions from exoplanetary systems – or from magnetic white dwarf-planet or white dwarf-brown dwarf systems –, that are expected to commence soon as part of extensive programs at large radiotelescopes such as LOFAR, UTR2 or the GMRT. Our methodology can be easily adapted to simulate specific observations, once effective detection is achieved.