{"id":519,"date":"2016-11-27T23:00:58","date_gmt":"2016-11-27T23:00:58","guid":{"rendered":"https:\/\/blogs.futura-sciences.com\/frankel\/?p=519"},"modified":"2017-04-05T07:03:36","modified_gmt":"2017-04-05T07:03:36","slug":"schiaparelli-lecons-dun-echec","status":"publish","type":"post","link":"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/","title":{"rendered":"Schiaparelli\u00a0: le\u00e7ons d\u2019un \u00e9chec"},"content":{"rendered":"

\"schiaparelli-vu-de-dessus\"<\/a>
\n<\/a>
\n<\/a>Dans un pr\u00e9c\u00e9dent article, nous avions soulign\u00e9 combien il \u00e9tait difficile de se poser sur Mars, et qu\u2019il fallait d\u2019abord passer par des \u00e9checs et en tirer des le\u00e7ons pour ma\u00eetriser la s\u00e9quence. Avec l\u2019\u00e9crasement de sa sonde Schiaparelli, l\u2019Europe en a fait aujourd\u2019hui les frais, mais heureusement a r\u00e9colt\u00e9 suffisamment de donn\u00e9es pour reconstituer le sc\u00e9nario de l\u2019accident.<\/p>\n

Si les Sovi\u00e9tiques n\u2019ont connu que des \u00e9checs lors de leur demi-douzaine de tentatives d\u2019atterrissage sur Mars, la r\u00e9f\u00e9rence reste les Etats-Unis qui n\u2019ont connu qu\u2019un seul \u00e9chec sur sept tentatives\u00a0: apr\u00e8s Viking 1 & 2\u2014coup de ma\u00eetre lors de leurs premi\u00e8res tentatives en 1976\u2014puis Pathfinder en 1997, et avant la s\u00e9rie ininterrompue de succ\u00e8s avec Spirit et Opportunity en 2004, Phoenix en 2008 et Curiosity en 2012, l\u2019exception fut le crash de Mars Polar Lander en 1999. Or, co\u00efncidence troublante ou maillon faible des s\u00e9quences d\u2019atterrissage sur Mars, l\u2019\u00e9chec de Schiaparelli lui ressemble bigrement.<\/p>\n

On se rappelle de cet \u00e9chec de 1999 qui fut ressenti comme un camouflet par la NASA. \u00c0 trop tirer sur le budget, les ing\u00e9nieurs avaient fait des impasses dans les simulations m\u00e9caniques de l\u2019atterrissage. Or apr\u00e8s avoir perdu l\u2019engin et s\u2019\u00eatre r\u00e9sign\u00e9 \u00e0 refaire ces co\u00fbteuses simulations, les ing\u00e9nieurs am\u00e9ricains se sont aper\u00e7us que lorsqu\u2019elle d\u00e9pliait ses pieds \u00e0 un kilom\u00e8tre d\u2019altitude\u2014pieds muni d\u2019un capteur de contact cens\u00e9 transmettre \u00e0 l\u2019ordinateur de bord l\u2019ordre de couper les r\u00e9trofus\u00e9es une fois au sol\u2014la sonde fut secou\u00e9e au point que les capteurs ont m\u00e9pris la vibration pour le contact en question. Moteurs coup\u00e9s \u00e0 un kilom\u00e8tre d\u2019altitude, Mars Polar Lander est all\u00e9e en chute libre s\u2019\u00e9craser au sol.<\/p>\n

\"Le<\/a>
Le crat\u00e8re d’impact (en noir) du crash de la sonde Schiaparelli sur Mars<\/figcaption><\/figure>\n

Pour Schiaparelli, la reconstitution \u00e0 partir des donn\u00e9es retransmises est la suivante. C\u2019est lors du d\u00e9ploiement du parachute principal \u00e0 12\u00a0kilom\u00e8tres d\u2019altitude que des vibrations plus importantes que pr\u00e9vu ont transmis \u00e0 l\u2019ordinateur de bord des mesures erron\u00e9es lui faisant croire, une vingtaine de secondes plus tard, que la sonde \u00e9tait d\u00e9j\u00e0 au sol. Vers 4 kilom\u00e8tres d\u2019altitude, l\u2019ordinateur s\u2019est donc m\u00e9lang\u00e9 les pinceaux, command\u00e9 le largage du parachute, suivi d\u2019un bref allumage anarchique puis extinction des r\u00e9trofus\u00e9es, et Schiaparelli a plong\u00e9 en chute libre, pour s\u2019\u00e9craser au sol \u00e0 une vitesse frisant les 500 kilom\u00e8tres\/heure, les r\u00e9servoirs de propergol \u00e0 peine entam\u00e9s ayant de surcro\u00eet explos\u00e9 lors du choc.<\/p>\n

\"Test<\/a>
Test du parachute de Schiaparelli: il reste du travail \u00e0 faire<\/figcaption><\/figure>\n

Si les ing\u00e9nieurs de l\u2019ESA se veulent optimistes, notant que c\u2019\u00e9tait bien lors de cette mission de validation technique que l\u2019\u00e9chec \u00e9tait permis, pour \u00ab\u00a0ajuster le tir\u00a0\u00bb et ne pas se rater la fois suivante, ils n\u2019ont plus de carte joker\u00a0: cette mission suivante ExoMars de 2020 est tr\u00e8s pr\u00e9cieuse et tr\u00e8s co\u00fbteuse, et pour la science martienne comme pour la r\u00e9putation de l\u2019Europe, esp\u00e9rons que les le\u00e7ons ont \u00e9t\u00e9 tir\u00e9es.<\/p>\n","protected":false},"excerpt":{"rendered":"

Dans un pr\u00e9c\u00e9dent article, nous avions soulign\u00e9 combien il \u00e9tait difficile de se poser sur Mars, et qu\u2019il fallait d\u2019abord passer par des \u00e9checs et en tirer des le\u00e7ons pour ma\u00eetriser la s\u00e9quence. Avec l\u2019\u00e9crasement de sa sonde Schiaparelli, l\u2019Europe en a fait aujourd\u2019hui les frais, mais heureusement a r\u00e9colt\u00e9 suffisamment de donn\u00e9es pour reconstituer … Continuer la lecture de Schiaparelli\u00a0: le\u00e7ons d\u2019un \u00e9chec<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_links_to":"","_links_to_target":""},"categories":[15,4],"tags":[],"class_list":["post-519","post","type-post","status-publish","format-standard","hentry","category-opinions","category-sciences"],"yoast_head":"\nSchiaparelli\u00a0: le\u00e7ons d\u2019un \u00e9chec - Carnets de bord d\u2019un martien, le blog de Charles FRANKEL, g\u00e9ologue<\/title>\n<meta name=\"description\" content=\"Crash de Schiaparelli sur Mars\u00a0: les raisons d'un \u00e9chec\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/\" \/>\n<meta name=\"twitter:label1\" content=\"\u00c9crit par\" \/>\n\t<meta name=\"twitter:data1\" content=\"Charles Frankel\" \/>\n\t<meta name=\"twitter:label2\" content=\"Dur\u00e9e de lecture estim\u00e9e\" \/>\n\t<meta name=\"twitter:data2\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/\",\"url\":\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/\",\"name\":\"Schiaparelli\u00a0: le\u00e7ons d\u2019un \u00e9chec - Carnets de bord d\u2019un martien, le blog de Charles FRANKEL, g\u00e9ologue\",\"isPartOf\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/blogs.futura-sciences.com\/frankel\/wp-content\/uploads\/sites\/7\/2016\/11\/Schiaparelli-vu-de-dessus.jpg\",\"datePublished\":\"2016-11-27T23:00:58+00:00\",\"dateModified\":\"2017-04-05T07:03:36+00:00\",\"author\":{\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/#\/schema\/person\/c6bf521c6d19bf22fb19fb2b3d6fcf63\"},\"description\":\"Crash de Schiaparelli sur Mars\u00a0: les raisons d'un \u00e9chec\",\"inLanguage\":\"fr-FR\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"fr-FR\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/2016\/11\/27\/schiaparelli-lecons-dun-echec\/#primaryimage\",\"url\":\"https:\/\/blogs.futura-sciences.com\/frankel\/wp-content\/uploads\/sites\/7\/2016\/11\/Schiaparelli-vu-de-dessus.jpg\",\"contentUrl\":\"https:\/\/blogs.futura-sciences.com\/frankel\/wp-content\/uploads\/sites\/7\/2016\/11\/Schiaparelli-vu-de-dessus.jpg\",\"width\":630,\"height\":315},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/blogs.futura-sciences.com\/frankel\/#website\",\"url\":\"https:\/\/blogs.futura-sciences.com\/frankel\/\",\"name\":\"Carnets de bord d\u2019un martien, le blog de Charles FRANKEL, g\u00e9ologue\",\"description\":\"La science ? 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