Euro satellite to map Earth''s gravity A satellite that can measure tiny variations in the Earth''s gravitational field will be one of Europe''s most challenging space missions to date.
The Gravity Field and Steady-State
Ocean Circulation Explorer (Goce), due for launch next year, looks like a spy plane from a movie.
According to a report by the BBC, its arrow shape, fins, and electric engine help keep the satellite stable as it flies through the wisps of air still present at an altitude of 260 kilometres. Goce data will have many uses, probing hazardous volcanic regions and bringing new insight into ocean behaviour.
"If we want to improve our climate models then we need to improve our knowledge of how the oceans move, and Goce will help us do that," mission scientist Dr Mark Drinkwater, from the European Space Agency, told BBC.
Students are taught that the acceleration due to gravity at the Earth''s surface is 9.8m per second squared — but, in truth; this figure varies around the
planet depending on the nature of the material underfoot.
The planet is far from a smooth sphere; the radius of the
globe at the equator is about 20 kilometre longer than at the poles. This ellipsoid is then marked by tall mountain ranges and cut by deep ocean trenches. The Earth''s interior layers are also not composed of perfect shells of homogenous rock — some regions are thicker or denser.
Such factors will cause the gravitational force at the surface to deviate from place to place by very small but significant amounts.
The Goce will map these
differences. This information will then be used to fashion what is, in essence, an idealised globe. Scientists call it the geoid. The geoid is of paramount interest to oceanographers who study the causes of the "hills" and "valleys" on the sea surface. If local gravity differences are not creating these features, then other factors such as currents, winds and tides must be responsible.