Scientists unveiled a new weapon in the battle against global warming last week: a 16ft torpedo-shaped probe that will swoop over the atmosphere to measure Earth's gravity with unprecedented accuracy.
The Gravity and Ocean Circulation Explorer, or Goce, has been dubbed the Ferrari of space probes because of its elegant design and will be launched early next year on a Russian SS-19 missile. Scientists say its data on Earth’s gravitational field will be vital in understanding how ocean currents react to the heating of our planet over the next few decades.
“Gravity is the force that drives the circulation of the oceans,” said Dr Mark Drinkwater, Goce’s project scientist. “Until we understand its exact role we cannot predict how the seas —and planet — will behave as the climate gets warmer. That is why Goce is being launched.”
Ocean currents take a third of all the heat that falls on equatorial regions and carries it to higher latitudes. One of the most important is the Gulf Stream, which scientists fear could soon be destroyed or diverted by melting Arctic ice. But they need to know all the gravitational effects that influence the stream’s course across the Atlantic before they can make accurate predictions.
The problem is that Earth’s gravity is not constant. The planet is flattened at the poles, for example, so gravity is stronger there, and weaker at the equator. “There are all sorts of wiggles and bumps in Earth’s gravity field,” said Dr Chris Hughes, of the Proudman Oceanographic Laboratory in Liverpool.
“Each will influence ocean currents, which have a crucial role in moving heat around the world. If we are to understand how climate change is going to affect the planet, we have to have a precise picture of its gravity field.”
Goce, which will cost the European Space Agency £ 200m to build and launch, has been put together by Thales Alenia Space Italia. And while most satellites are simply boxes with instruments bolted on, Goce is sleek and elegant; last week it was described by project manager Andrea Allasio as “the Ferrari of space probes”.  Covered with silver-blue solar cells, it must fly low because it could not measure Earth’s gravity with sufficient accuracy in deep space.
'It has to get close to make its measurements,' said Professor Reiner Rummel, of Munich Technical University.
However, as Goce skims above the Earth at a height of 150 miles it will encounter drag from the outer edges of the atmosphere. To prevent it losing height, an ion rocket will be fired constantly to keep it in its correct orbit. Computers will send 10 messages a second to its engines to ensure the probe orbits at the right height. To measure Earth's gravity the probe will use GPS devices to plot its exact position and a gradiometer, a machine that can detect fluctuations of a million millionth in Earth's gravity. This data will be transmitted daily and used to build a model of Earth's shape that is accurate to within a centimetre, as well as putting together a highly accurate gravity map of the planet.
'Once we combine that data with observations of sea height and ocean current flow - information that is provided by other satellites - we will get a clear idea of what our oceans are doing,' added Hughes. 'Then we will get a better picture of how the seas are changing as the world heats up.'