{"id":6597,"date":"2012-09-18T16:50:12","date_gmt":"2012-09-18T21:50:12","guid":{"rendered":"http:\/\/bucktownbell.com\/?p=6597"},"modified":"2012-09-18T16:50:12","modified_gmt":"2012-09-18T21:50:12","slug":"tandem-satellites-probe-the-moons-interior","status":"publish","type":"post","link":"http:\/\/bucktownbell.com\/?p=6597","title":{"rendered":"Tandem satellites probe the Moon&#8217;s interior"},"content":{"rendered":"<blockquote><p>GRAIL\u2019s two probes, named Ebb and Flow by schoolchildren in a NASA competition, were launched in September 2011 (see <a href=\"http:\/\/nature.com\/doifinder\/10.1038\/477016a\">\u2018Twins to Probe Moon\u2019s Heart\u2019<\/a>). The first probe began orbiting the Moon on 31 December 2011, with the second joining the next day. By March, they had begun detailed mapping. The two spacecraft exchange radio signals, recording fluctuations in their relative positions that are then used to reveal tiny accelerations and decelerations caused by variations in the Moon\u2019s gravitational field. The average altitude of the primary mission was 55 kilometres \u2014\u00a0 much lower than the orbit used by the Gravity Recovery and Climate Experiment (GRACE), a similar gravity-mapping mission for Earth that has to fly higher to avoid atmospheric friction. Occasionally, the GRAIL operations team brought the craft lower than 20 kilometres to further improve the resolution of the data. \u201cNothing beats flying low,\u201d says Zuber.<\/p><\/blockquote>\n<p>via <a href=\"http:\/\/www.nature.com\/news\/tandem-satellites-probe-the-moon-s-interior-1.11419\">Tandem satellites probe the Moon&#8217;s interior : Nature News &amp; Comment<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>GRAIL\u2019s two probes, named Ebb and Flow by schoolchildren in a NASA competition, were launched in September 2011 (see \u2018Twins to Probe Moon\u2019s Heart\u2019). The first probe began orbiting the Moon on 31 December 2011, with the second joining the &hellip; <a href=\"http:\/\/bucktownbell.com\/?p=6597\">Continue reading <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[737],"tags":[845,513,772,512],"class_list":["post-6597","post","type-post","status-publish","format-standard","hentry","category-stem","tag-moon","tag-nasa","tag-satellite","tag-space"],"_links":{"self":[{"href":"http:\/\/bucktownbell.com\/index.php?rest_route=\/wp\/v2\/posts\/6597","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/bucktownbell.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/bucktownbell.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/bucktownbell.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/bucktownbell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6597"}],"version-history":[{"count":1,"href":"http:\/\/bucktownbell.com\/index.php?rest_route=\/wp\/v2\/posts\/6597\/revisions"}],"predecessor-version":[{"id":6598,"href":"http:\/\/bucktownbell.com\/index.php?rest_route=\/wp\/v2\/posts\/6597\/revisions\/6598"}],"wp:attachment":[{"href":"http:\/\/bucktownbell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6597"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/bucktownbell.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6597"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/bucktownbell.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6597"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}