The L1 L^1 -Liouville property on graphs

In this paper we investigate the $L^1$-Liouville property, underlining its connection with stochastic completeness and other structural features of the graph. We give a characterization of the $L^1$-Liouville property in terms of the Green function of the graph and use it to prove its equivalence with stochastic completeness on model graphs. Moreover, we show that there exist stochastically incomplete graphs which satisfy the $L^1$-Liouville property and prove some comparison theorems for general graphs based on inner-outer curvatures. We also introduce the Dirichlet $L^1$-Liouville property of subgraphs and prove that if a graph has a Dirichlet $L^1$-Liouville subgraph, then it is $L^1$-Liouville itself. As a consequence, we obtain that the $L^1$-Liouville property is not affected by a finite perturbation of the graph and, just as in the continuous setting, a graph is $L^1$-Liouville provided that at least one of its ends is Dirichlet $L^1$-Liouville

Processing tools refinement for the JIRAM arrival to Jupiter

The JUNO mission, launched on August 2011 with the goal of investigating the origin and evolution of Jupiter, reached Jupiter in July 2016. The months preceding the JUNO orbit insertion have been crucial for all the instrument teams to check the status and working abilities of the respective experiments. JIRAM (Jupiter Infrared Auroral Mapper), with its imager and slit spectrometer operating over the 2-5μm spectral range will attempt to reveal the deep atmospheric composition -3 to 7 bars- in hot spots, to analyze the infrared auroral emissions of the H3 + molecules ionized by the Jovian magnetosphere currents and to detect the morphology and vertical structure of the clouds. Many different processing tools are in preparation to exploit the incoming JIRAM data. Here some results pertaining to the image quality optimization and the visualizations that can be obtained from the spectrometer data management are reported. <P /

The Comparative Exploration of the Ice Giant Planets with Twin Spacecraft: Unveiling the History of our Solar System

In the course of the selection of the scientific themes for the second and third L-class missions of the Cosmic Vision 2015-2025 program of the European Space Agency, the exploration of the ice giant planets Uranus and Neptune was defined "a timely milestone, fully appropriate for an L class mission". Among the proposed scientific themes, we presented the scientific case of exploring both planets and their satellites in the framework of a single L-class mission and proposed a mission scenario that could allow to achieve this result. In this work we present an updated and more complete discussion of the scientific rationale and of the mission concept for a comparative exploration of the ice giant planets Uranus and Neptune and of their satellite systems with twin spacecraft. The first goal of comparatively studying these two similar yet extremely different systems is to shed new light on the ancient past of the Solar System and on the processes that shaped its formation and evolution. This, in turn, would reveal whether the Solar System and the very diverse extrasolar systems discovered so far all share a common origin or if different environments and mechanisms were responsible for their formation. A space mission to the ice giants would also open up the possibility to use Uranus and Neptune as templates in the study of one of the most abundant type of extrasolar planets in the galaxy. Finally, such a mission would allow a detailed study of the interplanetary and gravitational environments at a range of distances from the Sun poorly covered by direct exploration, improving the constraints on the fundamental theories of gravitation and on the behaviour of the solar wind and the interplanetary magnetic field.Comment: 29 pages, 4 figures; accepted for publication on the special issue "The outer Solar System X" of the journal Planetary and Space Science. This article presents an updated and expanded discussion of the white paper "The ODINUS Mission Concept" (arXiv:1402.2472) submitted in response to the ESA call for ideas for the scientific themes of the future L2 and L3 space mission

The crucial role of HST during the NASA Juno mission: a "Juno initiative"

In 2016, the NASA Juno spacecraft will initiate its one-year mission around Jupiter and become the first probe to explore the polar regions of Jupiter. The HST UV instruments (STIS and ACS) can greatly contribute to the success of the Juno mission by providing key complementary views of Jupiter's UV aurora from Earth orbit. Juno carries an ultraviolet Spectrograph (UVS) and an infrared spectral mapper (JIRAM) that will obtain high-resolution spectral images providing the auroral counterpart to Juno's in situ particles and fields measurements with the plasma JADE and JEDI particle detectors. The Juno mission will be the first opportunity to measure simultaneously the energetic particles at high latitude and the auroral emissions they produce. Following programmatic and technical limitations, the amount of UVS data transmitted to Earth will be severely restricted. Therefore, it is of extreme importance that HST captures as much additional information as possible on Jupiter's UV aurora during the one-year life of the Juno mission. This white paper is a plea for a "Juno initiative" that will ensure that a sufficient number of orbits is allocated to this unique solar system mission.Comment: Paper submitted to the Space Telescope Science Institute in response to the call for HST White Papers for Hubble's 2020 Visio

Faint Luminescent Ring over Saturn’s Polar Hexagon

Springtime insolation is presently advancing across Saturn's north polar region. Early solar radiation scattered through the gaseous giant's atmosphere gives a unique opportunity to sound the atmospheric structure at its upper troposphere/lower stratosphere at high latitudes. Here, we report the detection of a tenuous bright structure in Saturn's northern polar cap corresponding to the hexagon equatorward boundary, observed by Cassini Visual and Infrared Mapping Spectrometer on 2013 June. The structure is spectrally characterized by an anomalously enhanced intensity in the 3610-3730 nm wavelength range and near 2500 nm, pertaining to relatively low opacity windows between strong methane absorption bands. Our first results suggest that a strong forward scattering by tropospheric clouds, higher in respect to the surrounding cloud deck, can be responsible for the enhanced intensity of the feature. This can be consistent with the atmospheric dynamics associated with the jet stream embedded in the polar hexagon. Further investigations at higher spectral resolution are needed to better assess the vertical distribution and microphysics of the clouds in this interesting region

Optical measurements of atmospheric particles from airborne platforms: in situ and remote sensing instruments for balloons and aircrafts

Multiwavelength laser backscattersondes (MAS) have been widely used from a variety of airborne platforms for in situ measurements of optical properties of clouds and atmospheric particulate as well as their phase and com- position. Recently, a new miniaturized LIDAR (MULID) has been developed using state-of-art technology for balloon borne profiling of the same quantities. A description of the two instruments, a survey of preliminary re- sults obtained during test flights and indications for future use are given

JUNO/JIRAM's view of Jupiter's H3+ emissions

The instrument JIRAM (Jovian Infrared Auroral Mapper), on board the NASA spacecraft Juno, is both an imager and a spectrometer. Two distinct detectors are used for imaging and spectroscopy. The imager acquires Jupiter images in two bands, one of which (L band, 3.3-3.6 μm) is devoted to monitor the H+3 emission. The spectrometer covers the spectral region from 2 to 5 μm (average spectral resolution 9 nm) with a 256 pixels slit, that can observe the same scene of the L band imager with some delay. JIRAM scientific goals are the exploration of the Jovian aurorae and the planet’s atmospheric structure, dynamics and composition. Starting early July 2016 Juno is orbiting around Jupiter. Since then, JIRAM has provided an unprecedented amount of measurements, monitoring both Jupiter’s atmosphere and aurorae. In particular the camera has monitored Jupiter’s poles with unprecedented spatial resolution, providing new insights in both its aurorae and the polar dynamic. The main findings obtained by the L imager are detailed pictures of Jupiter’s aurorae showing an extremely complex morphology of the H+3 distribution in the main oval and in the moon’s footprints. The spectrometer has enabled to measure the distribution of both H+3 concentration and temperature. The analysis of the north auroral region limb observations shows that the peak density of H+3 is above 750 km and that often it is anticorrelated to the temperature, confirming the infrared cooling effect of H+

Juno's Earth flyby: the Jovian infrared Auroral Mapper preliminary results

The Jovian InfraRed Auroral Mapper, JIRAM, is an image-spectrometer onboard the NASA Juno spacecraft flying to Jupiter. The instrument has been designed to study the aurora and the atmosphere of the planet in the spectral range 2-5 μm. The very first scientific observation taken with the instrument was at the Moon just before Juno's Earth fly-by occurred on October 9, 2013. The purpose was to check the instrument regular operation modes and to optimize the instrumental performances. The testing activity will be completed with pointing and a radiometric/spectral calibrations shortly after Jupiter Orbit Insertion. Then the reconstruction of some Moon infrared images, together with co-located spectra used to retrieve the lunar surface temperature, is a fundamental step in the instrument operation tuning. The main scope of this article is to serve as a reference to future users of the JIRAM datasets after public release with the NASA Planetary Data System

Una Perspectiva de la Integralidad. A 10 años de la creación del Consejo Social de la Universidad Nacional de La Plata

Since democratic recovery, the National Public Universities have recognized the importance of Extension as the main expression of the Social Commitment of Public Universities. In the UNLP, the statutory reform of 2008 implied an important recognition of this activity by specifying its scope and meaning. Based on this and in a context of progress and consolidation of social organizations in the social and political life of the country, the UNLP promoted actions that made possible a greater insertion in the territory, as well as an opening to different social actors, by means of the creation and consolidation of the Social Council. Through the consensual construction of a communitarian agenda and a permanent interactoral work, the Social Council intends to address the main socio-economic, political, cultural and environmental problems of the Region, collectively agreeing on strategies to address them. Since its creation, the Social Council has carried out a unique experience, which intends to contribute to the reorientation of teaching, research, transfer and extension practices, bettering a comprehensive training of future professionals, ultimately consolidating increasingly democratic citizenships. The purpose of this article is to present the perspective and reflections arising from the experience of the Social Council, developed since its creation in 2010.Desde la recuperación democrática las Universidades Nacionales Públicas han reconocido la importancia de la Extensión como la principal expresión del Compromiso Social Universitario. En la UNLP la reforma estatutaria del 2008 implicó un importante reconocimiento a la misma al precisarse sus alcances y significado. En base a ello y en un contexto de avance y consolidación de las organizaciones sociales en la vida social y política del país, la UNLP impulsó acciones que posibilitaron una mayor inserción en los territorios y una apertura a los diferentes actores sociales mediante la conformación del Consejo Social. A través de la construcción consensuada de una agenda comunitaria y de un permanente trabajo interactoral, el Consejo Social se&nbsp;propone abordar las principales problemáticas socio económicas, políticas, culturales y ambientales de la Región y acordar colectivamente estrategias de abordaje de las mismas. Desde su creación el Consejo Social ha llevado a cabo una experiencia que espera contribuir a la reorientación de las prácticas de docencia, investigación, transferencia y extensión, contribuyendo a la formación integral de los futuros profesionales, aportando a la consolidación de ciudadanías cada vez más democráticas. El propósito de este artículo es presentar la perspectiva y reflexiones surgidas a partir de la experiencia del Consejo Social, desarrollada desde su creación en 2010