![](\"http:\/\/www.esa.int\/var\/esa\/storage\/images\/esa_multimedia\/images\/2018\/08\/the_satellite_on_the_edge_of_space\/17663746-1-eng-GB\/The_satellite_on_the_edge_of_space_small.jpg\")
<\/p>\n\t\t\t\t\t<\/p>\n
\nGOCE (pronounced go-chay), the Gravity Field and Steady-State Ocean Circulation Explorer, was one of ESA\u2019s most remarkable missions. Operating in the lowest-ever orbit of any Earth observation satellite, GOCE was on the edge of space; flying at an altitude of just 224 km.\n<\/p>\n
\nLaunched in 2009 on a Rockot<\/a> launcher from northern Russia, GOCE spent four years mapping Earth\u2019s gravity with unrivalled precision, resulting in a unique model of the \u2018geoid<\/a>\u2019 \u2014 the hypothetical shape that the surface of the oceans would take under only the influence of Earth\u2019s gravity and rotation, ignoring the influence of winds and tides.\n<\/p>\n \nBetter understanding of Earth\u2019s gravity field and it\u2019s associated geoid provides insight into global ocean circulation<\/a> patterns, and these play a crucial role in climate regulation.\n<\/p>\n \nIn order to determine this, the \u201cmathematical figure of the Earth\u201d<\/a>, GOCE had to fly as low in orbit as possible, so as to sense the minute variations in Earth\u2019s gravitational field. This \u2018fast and low\u2019 orbit presented unique challenges to mission teams at ESA\u2019s ESOC<\/a> mission control in Germany, from where GOCE was flown.\n<\/p>\n \n\u2018Skimming’ the atmosphere, GOCE was flying so low around Earth (about half the altitude of the International Space Station) that the air was still rather dense, meaning it experienced significant drag forces during its life in orbit.\n<\/p>\n \nHowever in order to ensure the measurements taken by GOCE were of true gravity, the satellite had to be kept in \u2018free-fall\u2019. So, along with its distinctive aerodynamic design, GOCE had an electric ion propulsion engine that would generate tiny forces, between 1 and 20 millinewtons (mN), that continually and instantaneously compensated for variations in air drag.\n<\/p>\n \nAfter four years at work on the edges of space, on 11 November 2013, GOCE succumbed to the force it had been studying. It reentered Earth\u2019s atmosphere over the Falkland islands, where it disintegrated and burnt up, and unusually for any spacecraft in it’s final days, the spacecraft was spotted<\/a> by an observer on Earth during the process.\n<\/p>\n \nChristoph Steiger, Spacecraft Operations Manager for GOCE looks back: "Operating GOCE was special. Flying a spacecraft far lower than any other Earth observation mission posed special challenges for mission control at ESOC, such as predicting GOCE’s orbit correctly in a highly variable drag environment. Re-entry operations were particularly exciting. Because GOCE was designed to withstand high levels of drag, it was still sending data up to 1.5 hours before re-entry, at little more than 100 km altitude."\n<\/p>\n \n"While it was sad to see GOCE come to an end, team members could move on to their next projects with the good feeling of having gotten the most out of a truly unique mission."<\/p>\n","protected":false},"excerpt":{"rendered":" \nGOCE (pronounced go-chay), the Gravity Field and Steady-State Ocean Circulation Explorer, was one of ESA’s most remarkable missions. Operating in the lowest-ever orbit of any Earth observation satellite, GOCE was on the edge of space; flying at an altitude of just 224 km.\n<\/p>\n \nLaunched in 2009 on a Rockot<\/a> launcher from northern Russia, GOCE spent four years mapping Earth’s gravity with unrivalled precision, resulting in a unique model of the ‘geoid<\/a>’ — the hypothetical shape that the surface of the oceans would take under only the influence of Earth’s gravity and rotation, ignoring the influence of winds and tides.\n<\/p>\n \nBetter understanding of Earth’s gravity field and it’s associated geoid provides insight into global ocean circulation<\/a> patterns, and these play a crucial role in climate regulation.\n<\/p>\n \nIn order to determine this, the “mathematical figure of the Earth”<\/a>, GOCE had to fly as low in orbit as possible, so as to sense the minute variations in Earth’s gravitational field. This ‘fast and low’ orbit presented unique challenges to mission teams at ESA’s ESOC<\/a> mission control in Germany, from where GOCE was flown.\n<\/p>\n \n‘Skimming’ the atmosphere, GOCE was flying so low around Earth (about half the altitude of the International Space Station) that the air was still rather dense, meaning it experienced significant drag forces during its life in orbit.\n<\/p>\n \nHowever in order to ensure the measurements taken by GOCE were of true gravity, the satellite had to be kept in ‘free-fall’. So, along with its distinctive aerodynamic design, GOCE had an electric ion propulsion engine that would generate tiny forces, between 1 and 20 millinewtons (mN), that continually and instantaneously compensated for variations in air drag.\n<\/p>\n \nAfter four years at work on the edges of space, on 11 November 2013, GOCE succumbed to the force it had been studying. It reentered Earth’s atmosphere over the Falkland islands, where it disintegrated and burnt up, and unusually for any spacecraft in it’s final days, the spacecraft was spotted<\/a> by an observer on Earth during the process.\n<\/p>\n \nChristoph Steiger, Spacecraft Operations Manager for GOCE looks back: “Operating GOCE was special. Flying a spacecraft far lower than any other Earth observation mission posed special challenges for mission control at ESOC, such as predicting GOCE’s orbit correctly in a highly variable drag environment. Re-entry operations were particularly exciting. Because GOCE was designed to withstand high levels of drag, it was still sending data up to 1.5 hours before re-entry, at little more than 100 km altitude.”\n<\/p>\n \n“While it was sad to see GOCE come to an end, team members could move on to their next projects with the good feeling of having gotten the most out of a truly unique mission.”<\/p>\n","protected":false},"author":5,"featured_media":615444,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[27],"tags":[],"class_list":["post-515395","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-multimedia"],"_links":{"self":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/515395","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=515395"}],"version-history":[{"count":2,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/515395\/revisions"}],"predecessor-version":[{"id":515938,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/posts\/515395\/revisions\/515938"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=\/wp\/v2\/media\/615444"}],"wp:attachment":[{"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=515395"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=515395"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceweekly.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=515395"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}<\/p>\n