<img alt=“goce_science2_L.jpg” src=“https://blogs.nature.com/news/thegreatbeyond/goce_science2_L.jpg” width=“400” height=“283” align=right hspace=10 border=0 />

European spacecraft Gravity field and steady-state Ocean Circulation Explorer (Goce) begins its finely tuned gravitational measurements this week.

The BBC explains that the mission will track ocean movement and should improve on existing measurements of the Earth’s surface and its gravitational field—known as the geoid. Low solar activity and a calm upper atmosphere this week mean that the ion-powered spacecraft can fly just about 254.75 kilometres above the surface, plus or minus 50 metres, even lower than the 268 kilometres mission planners hoped for. The lower it flies, the more sensitive its measurements, which can detect changes in gravity as small as one 10-trillionth of gravity at the surface.

For Nature’s previous coverage, see Gravity mission to launch (Nature News, 11 March 2009) and on GOCE is Go! (The Great Beyond, 17 March 2009) from the time of Goce’s launch from Plesetsk Cosmodrome in Russia. In case the science proves overwhelming, the European Space Agency has provided a helpful visual demonstration that Goce, (spacecraft, right) will map the gravity (represented here by apples, center) of the Earth (bottom).

Photo: ESA