The ESA gravity mapping satellite, Goce, has entered its targeted orbit to begin operations. The tiny and strangely beautiful probe will wind its way round the Earth as the planet rotates underneath it, measuring the gravitational attraction of the planet below to an accuracy equivalent to a gravitational pull 10,000,000,000,000 times lower than the surface attraction.
One side of the spacecraft is covered in solar panels constantly illuminated by the Sun. The other side radiates excess heat into space, ensuring the probe is at a constant equilibrium. Goce has been put into an orbit of 255 km, below the expected altitude of 268 km, possible due to the low level of solar activity leading to a cooler, less expanded upper atmosphere.
The satellite will take measurements of the gravitational attraction of the Earth, which deviates due to the shape and composition of the Earth deviating. The Earth bulges at the equator and has different densities of crust material as well as different heights to its surface. Flows of material beneath the crust can also be detected through their altering of the composition and therefore density of that part of the planet.
Further details can be found on the BBC website.