Observatoire de Paris Institut national de recherche scientifique français Univerité Pierre et Marie Curie Université Paris Diderot - Paris 7

Sauf exception, les séminaires ont lieu sur le site de Meudon, dans la salle de conférence du bâtiment 17.

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Séminaires passés

  • Lundi 25 octobre 2021 à 11h00

    Exploring the near-Earth asteroid diversity : the ANIME CubeSat mission concept

    Davide Perna (INAF - Observatoire de Rome)

    The “Asteroid Nodal Intersection Multiple Encounters” (ANIME) mission concept has been developed in response to the 2020 Italian Space Agency (ASI) call for ideas for future CubeSat missions. ANIME aims to explore three near-Earth asteroids (NEAs), selected by virtue of their peculiar and yet unexplored size and physical regimes, as well as their relevance in terms of planetary protection. Thanks to an optimized trajectory, the targets are encountered during their passages through their orbital nodes. The 12U ANIME spacecraft will flyby two “potentially hazardous asteroids”, and then rendezvous in 2028 with baseline target 2000 SG344. This 40-m-sized asteroid is an order of magnitude smaller than previously visited ones, and its study will allow us to constrain the latest theories about planetary system formation scenarios, addressing questions about the monolithic vs. cohesive vs. rubble-pile aggregation structure of small asteroids.

    I will present and discuss the ANIME mission concept, which has been developed by a team from Italian INAF observatories and universities.

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  • Lundi 4 octobre 2021 à 16h00 (En visioconférence)

    Comparison between laboratory reflectance spectroscopy and simulated unresolved observations of primitive small bodies

    Sandra Potin (LESIA)

    Reflectance spectroscopy is a common tool used to retrieve physical and mineralogical information on Solar System planetary bodies. However, the reflectance spectrum of a surface depends on several parameters, including the illumination condition and observing geometry. The observed reflectance of small bodies is generally compared to laboratory measurements of meteoritic samples or terrestrial analogues to assess the composition and alteration history of the target’s surface.

    Laboratory measurements are performed in a controlled environment, where the composition and texture of the sample are known and the illumination and observing geometry is fixed. However, if the spectroscopic observations of the small body are unresolved, its reflectance is integrated over the whole observed surface, which averages spatial compositional and textural heterogeneities and changes in the illumination and observation geometries due to both the shape of the object and the topography of its surface (slopes, craters, …).

    First I will highlight the effects of the illumination and observation geometry on the reflectance spectra of meteorites. Then I will compare reflectance spectra acquired in the laboratory and simulated unresolved observations of small bodies. Finally I will discuss the limits of the comparison between meteorites and small bodies.

    Pour assister au séminaire :

    Avec CarbonFreeConf (qui vous donne accès à plus de fonctionnalités) :
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  • Vendredi 1er octobre 2021 à 11h00 (En visioconférence avec Zoom)

    Cassini at Jupiter : radio emissions and magnetospheric dynamics

    Philippe Zarka (LESIA)

    This seminar deals with the results obtained with Cassini’s radio instrument (built in LESIA - actually DESPA) during the Jupiter fly-by of 2000-2001. First I will briefly recall the flux calibration of the data and the results on Jupiter’s radio components, their spectrum, power and and beaming obtained and published in 2004. Then I will focus on new results just accepted in the JGR, obtained from the same data but including also this time the polarization information. These results concern the physical relationship between auroral radio components, the localization of their source in Jupiter’s magnetosphere, and the relative control of their variations by the planetary rotation and by the solar wind. With this work, we have tried (and hopefully succeeded) to reduce the entropy of the complex Jovian radio zoo. The next stepinvolves modeling via the ExPRES code developed in LESIA. Our results provide a frame to interpret the present radio observations by Juno and the future ones by JUICE, and a firmer ground to extrapolate our understanding of the Jovian magnetosphere to astrophysical systems (exoplanets).

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  • Lundi 27 septembre 2021 à 16h00 (En visioconférence)

    De CH4 à HCl en passant par HDO et H2O : 3 ans de recherche active des gaz trace martiens par le spectromètre ACS sur TGO

    Franck Montmessin (LATMOS)

    Le Trace Gas Orbiter (TGO) de l’ESA est le premier volet du programme de l’ESA ExoMars.
    L’orbiteur a atteint Mars en octobre 2016 et a achevé sa phase d’aéro-freinage en mars 2018 après laquelle la mission scientifique de TGO a pu démarrer. L’objectif majeur de TGO est de détecter, cartographier et remonter aux sources de gaz traces, dont certains pourraient être révélateurs d’une activité résiduelle géophysique, voire même biologique, sur Mars ; le plus emblématique d’entre eux étant le méthane. A bord de TGO, l’Atmospheric Chemistry Suite (ACS) est le spectromètre développé par l’IKI (Moscou) et auquel le LATMOS a été partie prenante. ACS couvre un domaine de longueur d’ondes allant de 0.7 à 15 mm où toutes les espèces gazeuses connues ou attendues sur Mars possèdent une signature diagnostique et offre une résolution spectrale qui n’avait jamais été atteinte par aucune autre mission martienne par le passé.
    Après 3 ans passés en orbite autour de Mars, l’heure est venue de faire un premier bilan du travail exploratoire réalisé par ACS. De ses tentatives répétées de confirmer la présence du méthane à son ébauche de caractérisation du cycle de H2O conjointement à celui de HDO en passant par sa découverte de HCl, ACS et TGO refaçonnent peu à peu notre compréhension des mécanismes physico-chimiques qui régissent la composition et le comportement de l’atmosphère de Mars.
    Ces résultats et leur portée pour la science martienne seront présentés au cours de ce séminaire.

    ESA’s Trace Gas Orbiter (TGO) is the first component of ESA’s ExoMars programme.
    The orbiter reached Mars in October 2016 and completed its aerobraking phase in March 2018, after which the TGO science mission could start. The main objective of TGO is to detect, map and trace back the origin of trace gases, some of which could be indicative of residual geophysical and even biological activity on Mars, the most emblematic of which is methane. On board TGO, the Atmospheric Chemistry Suite (ACS) is the spectrometer developed by IKI (Moscow) and in which LATMOS has been involved. ACS covers a wavelength range from 0.7 to 15 mm where all known or expected gaseous species on Mars have a diagnostic signature and offers a spectral resolution that has never been achieved by any other Mars mission in the past. After 3 years in Mars orbit, it is time to make a first assessment of the exploratory work done by ACS.
    From its repeated attempts to confirm the presence of methane, to its tentative characterisation of the H2O cycle in conjunction with that of HDO, to its discovery of HCl, ACS and TGO are gradually reshaping our understanding of the physico-chemical mechanisms that govern the composition and behaviour of Mars’ atmosphere. These results and their significance for Martian science will be presented during this seminar.

    Pour assister au séminaire :

    Avec CarbonFreeConf (qui vous donne accès à plus de fonctionnalités) :
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