On 16 March, the European Space Agency will launch an Earth observation satellite to investigate the Earth's gravitational field with unprecedented resolution and accuracy.
The Gravity and Ocean Circulation Explorer (GOCE) will be placed in a low altitude orbit by the Russian space launch vehicle, Rockot, from the Plesetsk Cosmodrome. Rockot is operated by Eurockot Launch Services, a joint venture between EADS Astrium and the Khrunichev Space Centre.
GOCE carries a highly sensitive gradiometer to measure the variations of the gravity field in three dimensions. The data collected will provide a map of the geoid. It will be accurate to 1-2 cm vertically, but only about 100 km horizontally.
The gravity field at the spacecraft will be somewhere between 9.788 to 9.838 metres per second. It will be measured by 6 accelerometers, capable of detecting accelerations of 1 in 10 million million. They are mounted in orthogogonol pairs and are 100 times more sensitive than any previously flown in space.
The position of the spacecraft itself will be measured via GPS and laser tracking from the ground. GOCE is fitted with a laser reflector.
Such a map will not only greatly improve our knowledge and understanding of the Earth's internal structure, but will also be used to provide much better reference data for ocean and climate studies and ocean circulation.
Practical mission applications will also include construction, planning and surveying as well as providing reference data on sea levels.
The spacecraft had to be designed to orbit the Earth low enough to gather gravitational data, but high enough to filter out disturbances caused by the atmosphere. This resulted in a 260 km orbit and a slender 5 metre shape for aerodynamics.
An ion thruster is able to compensate for atmospheric drag. The thruster is powered by 40 kg of xenon, which will keep it running for the 3-year life of the spacecraft.
Source: www.asmmag.com
