{"id":6488,"date":"2025-11-26T10:41:43","date_gmt":"2025-11-26T09:41:43","guid":{"rendered":"https:\/\/academiespatiale.fr\/?p=6488"},"modified":"2025-12-19T18:19:50","modified_gmt":"2025-12-19T17:19:50","slug":"le-premier-docteur-issu-du-master-2-newspace-de-lacademie-spatiale-dile-de-france","status":"publish","type":"post","link":"https:\/\/academiespatiale.fr\/index.php\/2025\/11\/26\/le-premier-docteur-issu-du-master-2-newspace-de-lacademie-spatiale-dile-de-france\/","title":{"rendered":"Le premier docteur issu du Master 2 NewSpace de l’Acad\u00e9mie Spatiale d’\u00cele-de-France"},"content":{"rendered":"\n
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\n\t\t\tHome<\/a>\n\t\t<\/span>»<\/span>\n\t\t\tFormation<\/a>\n\t\t<\/span>»<\/span>\n\t\t\tLe premier docteur issu du Master 2 NewSpace de l\u2019Acad\u00e9mie Spatiale d\u2019\u00cele-de-France\n\t\t<\/span><\/div><\/div>\n<\/div>\n\n\n\n

Le 24 novembre 2025, Thomas Lefebvre, ancien \u00e9tudiant du Master 2 NewSpace de l’Acad\u00e9mie Spatiale, a soutenu avec succ\u00e8s sa th\u00e8se intitul\u00e9e : \u00ab Restitution de propri\u00e9t\u00e9s microphysiques et dynamiques de la convection profonde par satellite : pr\u00e9paration de la mission C\u00b2OMODO \u00bb<\/strong><\/p>\n\n\n\n

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Il y a pr\u00e8s de 5 ans, Thomas Lefebvre faisait partie de la toute premi\u00e8re promotion du Master 2 NewSpace. Master en poche, il a poursuivi ses \u00e9tudes par un doctorat au LATMOS (Laboratoire Atmosph\u00e8res et Observations Spatiales), sous la direction d’H\u00e9l\u00e8ne Brogniez.<\/p>\n\n\n\n

Lundi dernier, il est devenu Dr. Thomas Lefebvre apr\u00e8s avoir soutenu avec succ\u00e8s sa th\u00e8se de doctorat. Le jury l’a f\u00e9licit\u00e9 pour la grande qualit\u00e9 de son manuscrit et pour la pr\u00e9sentation transversale, concise et extr\u00eamement claire de sa th\u00e8se.<\/p>\n\n\n\n

Il devient ainsi le premier dipl\u00f4m\u00e9 de notre master \u00e0 obtenir le titre de Docteur. Probablement le premier d’une longue s\u00e9rie. Un grand bravo \u00e0 Thomas pour ses travaux, son engagement et son excellence scientifique !<\/p>\n\n\n\n

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Plus d’infos sur le Master 2 NewSpace
\u2192 UVSQ : Master 2 Enjeux du spatial et nouvelles applications – NEWSPACE<\/a>
\u2192 Universit\u00e9 Paris-Saclay : M2 Enjeux du Spatial et nouvelles Applications – Newspace<\/a><\/p>\n\n\n\n

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R\u00c9SUM\u00c9 (English Below)<\/strong><\/p>\n\n\n\n

La convection profonde joue un r\u00f4le central dans la redistribution de chaleur et d\u2019humidit\u00e9 dans la troposph\u00e8re, dans la circulation atmosph\u00e9rique tropicale et dans le bilan radiatif terrestre global. Elle est \u00e0 l\u2019origine de ph\u00e9nom\u00e8nes extr\u00eames tels que les orages violents, les pluies intenses ou les cyclones tropicaux, mais demeure difficile \u00e0 observer et \u00e0 repr\u00e9senter dans les mod\u00e8les climatiques et de pr\u00e9vision du temps. En parall\u00e8le des campagnes de terrain et des observations au sol, la t\u00e9l\u00e9d\u00e9tection spatiale est devenue essentielle pour observer les syst\u00e8mes convectifs \u00e0 l\u2019\u00e9chelle globale avec une fr\u00e9quence de revisite \u00e9lev\u00e9e. Celle-ci a permis de r\u00e9v\u00e9ler leur morphologie et d\u2019apporter des informations sur leur structure interne, mais la documentation de leur dynamique verticale reste limit\u00e9e.<\/p>\n\n\n\n

Dans ce contexte, la mission Convective Core Observation through MicrOwave Derivative in the trOpics (C\u00b2OMODO) vise \u00e0 mieux comprendre les nuages convectifs et leurs processus de formation. Elle repose sur un tandem de radiom\u00e8tres micro-ondes passifs observant successivement une m\u00eame sc\u00e8ne avec un d\u00e9calage de 45 \u00e0 135s. Cette configuration originale permet d\u2019exploiter les mesures et leurs variations temporelles pour restituer des informations microphysiques et dynamiques.<\/p>\n\n\n\n

Les travaux de cette th\u00e8se visent \u00e0 pr\u00e9parer l\u2019exploitation de cette mission du CNES en d\u00e9veloppant des m\u00e9thodes d\u2019inversion de propri\u00e9t\u00e9s microphysiques et dynamiques \u00e0 l\u2019aide d\u2019algorithmes d\u2019apprentissage automatique et d\u2019une approche variationnelle. Ils s\u2019appuient sur des simulations de la convection tropicale coupl\u00e9es \u00e0 un mod\u00e8le de transfert radiatif. Ces travaux montrent que les observations pr\u00e9sentent une sensibilit\u00e9 verticale suffisante pour distinguer diff\u00e9rents niveaux d\u2019altitude, qu\u2019elles sont fortement influenc\u00e9es par la glace et sensibles \u00e0 la nature des hydrom\u00e9t\u00e9ores. L\u2019introduction de la dimension temporelle relie directement les variations radiom\u00e9triques rapides \u00e0 l\u2019\u00e9volution de la distribution de glace et offre un acc\u00e8s in\u00e9dit aux propri\u00e9t\u00e9s dynamiques des syst\u00e8mes convectifs.<\/p>\n\n\n\n

Deux approches compl\u00e9mentaires ont \u00e9t\u00e9 d\u00e9velopp\u00e9es. L\u2019apprentissage automatique a d\u2019abord \u00e9t\u00e9 utilis\u00e9 pour classifier les diff\u00e9rentes structures nuageuses des syst\u00e8mes convectifs et restituer des variables g\u00e9ophysiques int\u00e9gr\u00e9es verticalement. En parall\u00e8le, une m\u00e9thode variationnelle originale, VARAND\u00b2, a \u00e9t\u00e9 con\u00e7ue pour exploiter directement les mesures du tandem et restituer des propri\u00e9t\u00e9s dynamiques verticalement r\u00e9solues. L\u2019algorithme, fond\u00e9 sur un op\u00e9rateur d\u2019observation dynamique couplant transfert radiatif et advection verticale, restitue simultan\u00e9ment le profil de contenu en glace ainsi que des param\u00e8tres dynamiques d\u00e9crivant les ascendances convectives. Les r\u00e9sultats de ces deux m\u00e9thodes confirment le potentiel du tandem C\u00b2OMODO pour restituer conjointement des propri\u00e9t\u00e9s microphysiques et des indicateurs dynamiques de la convection profonde.<\/p>\n\n\n\n

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\u2014 English Version \u2014<\/em><\/p>\n\n\n\n

Deep convection plays a central role in the redistribution of heat and moisture in the troposphere, tropical atmospheric circulation, and the Earth\u2019s global radiation budget. It is responsible for extreme phenomena such as severe thunderstorms, heavy rainfall, and tropical cyclones, yet it remains difficult to observe and represent in weather and climate models. Alongside field campaigns and ground-based observations, satellite remote sensing has become essential for observing these systems at the global scale with a high revisit frequency. It has revealed the morphology of convective systems and provided information on their internal structure, but documentation of their vertical dynamics remains limited.<\/p>\n\n\n\n

In this context, the Convective Core Observation through MicrOwave Derivative in the trOpics (C\u00b2OMODO) mission aims to improve our understanding of convective clouds and their formation processes. It relies on a tandem of passive microwave radiometers that successively observe the same scene, separated by 45 to 135s. This novel configuration makes it possible to exploit the measurements and their temporal variations to retrieve microphysical and dynamical information.<\/p>\n\n\n\n

This thesis aims to prepare the scientific exploitation of this CNES mission by developing inversion methods for microphysical and dynamical properties using machine-learning algorithms and a variational approach. It builds on simulations of tropical convection coupled with a radiative transfer model. The results show that the observations exhibit sufficient vertical sensitivity to distinguish different altitude levels, that they are strongly influenced by ice, and that they are sensitive to hydrometeor types. Introducing the temporal dimension directly links rapid radiometric variations to the evolution of the ice distribution and provides unprecedented access to the dynamical properties of convective systems.<\/p>\n\n\n\n

Two complementary approaches have been developed. Machine learning was first used to classify cloud structures within convective systems and to retrieve vertically integrated geophysical variables such as IWP. In parallel, a novel variational method, VARAND\u00b2, was designed to exploit the tandem measurements directly and to retrieve vertically resolved dynamical properties. The algorithm, based on a dynamic observation operator coupling radiative transfer and vertical advection, simultaneously retrieves the ice water content profile along with dynamical parameters describing convective updrafts. The results of these two methods confirm the potential of the C\u00b2OMODO tandem to jointly retrieve microphysical properties and dynamical indicators of deep convection.<\/p>\n\n\n\n

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Composition du jury<\/strong><\/p>\n\n\n\n

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  • C\u00e9line CORNET<\/strong> (Rapportrice) \u2013 Professeure, Laboratoire d\u2019Optique Atmosph\u00e9rique, Universit\u00e9 de Lille<\/li>\n\n\n\n
  • J\u00e9r\u00f4me VIDOT<\/strong> (Rapporteur) \u2013 Directeur de recherche, CNRM\/M\u00e9t\u00e9o-France\/CNRS<\/li>\n\n\n\n
  • Philippe CHAMBON<\/strong> (Examinateur) \u2013 Directeur de recherche, CNRM\/M\u00e9t\u00e9o-France\/CNRS<\/li>\n\n\n\n
  • Ziad HADDAD<\/strong> (Examinateur) \u2013 Directeur de recherche \u00e9m\u00e9rite, Jet Propulsion Laboratory<\/li>\n<\/ul>\n\n\n\n

    Encadrement<\/strong><\/p>\n\n\n\n

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    • H\u00e9l\u00e8ne Brogniez<\/strong> (Directrice de th\u00e8se) \u2013 Professeure, Laboratoire des Sciences du Climat et de l\u2019Environnement, UVSQ<\/li>\n\n\n\n
    • Laura Hermozo<\/strong> (Co-directrice) \u2013 Ing\u00e9nieure, CNES.<\/li>\n\n\n\n
    • Fr\u00e9d\u00e9ric Chevallier<\/strong> (co-encadrant) \u2013 Ing\u00e9nieur-chercheur, Laboratoire des Sciences du Climat et de l\u2019Environnement, CEA.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"

      Le 24 novembre 2025, Thomas Lefebvre, ancien \u00e9tudiant du Master 2 NewSpace de l’Acad\u00e9mie Spatiale, a soutenu avec succ\u00e8s sa th\u00e8se intitul\u00e9e : \u00ab Restitution de propri\u00e9t\u00e9s microphysiques et dynamiques de la convection profonde par satellite : pr\u00e9paration de la mission C\u00b2OMODO \u00bb Il y a pr\u00e8s de 5 ans, Thomas […]<\/p>\n","protected":false},"author":1,"featured_media":6494,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_EventAllDay":false,"_EventTimezone":"","_EventStartDate":"","_EventEndDate":"","_EventStartDateUTC":"","_EventEndDateUTC":"","_EventShowMap":false,"_EventShowMapLink":false,"_EventURL":"","_EventCost":"","_EventCostDescription":"","_EventCurrencySymbol":"","_EventCurrencyCode":"","_EventCurrencyPosition":"","_EventDateTimeSeparator":"","_EventTimeRangeSeparator":"","_EventOrganizerID":[],"_EventVenueID":[],"_OrganizerEmail":"","_OrganizerPhone":"","_OrganizerWebsite":"","_VenueAddress":"","_VenueCity":"","_VenueCountry":"","_VenueProvince":"","_VenueState":"","_VenueZip":"","_VenuePhone":"","_VenueURL":"","_VenueStateProvince":"","_VenueLat":"","_VenueLng":"","_VenueShowMap":false,"_VenueShowMapLink":false,"footnotes":""},"categories":[5],"tags":[],"class_list":["post-6488","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-formation"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/posts\/6488","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/comments?post=6488"}],"version-history":[{"count":11,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/posts\/6488\/revisions"}],"predecessor-version":[{"id":7294,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/posts\/6488\/revisions\/7294"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/media\/6494"}],"wp:attachment":[{"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/media?parent=6488"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/categories?post=6488"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/academiespatiale.fr\/index.php\/wp-json\/wp\/v2\/tags?post=6488"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}