Monday March 17th was a very happy day for the European Space Agency (ESA): the first of a new family of ESA satellites - called the Earth Explorers – successfully lifted off from the Plesetsk Cosmodrome in Northern Russia, 800 km north of Moscow.
The new satellite’s name is GOCE - Gravity field and steady-state Ocean Circulation Explorer – although it has been dubbed « the Ferrari of the space »,
for its stylish shape that reminds you of a formula one car. Greeted by ESA General Director Jean-Jacques Dordain with the words «Go, GOCE, go!», GOCE-the-Ferrari-spacecraft sped away for a 24 months long race high above our planet. On March 20th, Flight Operations Director Pier Paolo Emanuelli said : «Everything is working well and we have a healthy satellite».
The dimensions of the satelitte are : 5.3 m in length, 1 m in diameter and weighs one ton. It’s the first satellite featuring an «arrow-like» aerodynamic design: this is to limit the drag of the residual atmosphere at an altitude of 260 km, where GOCE will swoop on a polar orbit.
GOCE is equipped with a highly sophisticate gradiometer, made of six accelerometers, 100 times more sensitive than any previously flown in space. It will measure the variations of the Earth’s gravity field in three dimensions, with an accuracy of 1-2 cm vertically. GOCE is also equipped with a 12-channel GPS receiver, that permanently measures the satellite's position.
Gravity is a natural, invisible force that pulls two masses together. On Earth – as well as within the Earth - mass is not equally distributed. The gravitational force varies from place to place around the planet. For example, the force of gravity is weaker at the Equator and stronger at the poles : if you travel to Antarctica, you would weight a few more grams than usual (and this is not a result of the EWC!). The gravity is different over a mountain ridge and over a deep ocean trench. But why do we need to map the Earth ‘s gravity field ?
The data collected by ESA’s GOCE satellite will be processed to produce the most accurate Earth’s gravity map. This map is called the geoid. Since the gravity force isn’t the same all over the planet, the geoid doens’t look perfectly round but rather lumpy and bumpy like a potato.
Precise knowledge of the geoid will help scientists to better understand how the Earth works and better address the impact of climate change.
Ocean circulation plays an important role in the distribution of heat around the Earth: to understand how the oceans behave will greatly improve climate-forecasting models. Thanks to GOCE – we will know with great precision the value of the sea-level change.
GOCE high resolution gravity measurements will also improve estimates of the thickness and mass of the polar ice sheets, as well as the thickness of the polar sea-ice, both of which are witnesses of climate change effects. It will also improve our knowledge of the bedrock in Greenland and Antarctica.
The GOCE mission cost 350 million Euros (including launcher and operations). Planning and construction of the satellite involved 45 European companies led by Thales Alenia Space.
The Earth Explorer missions have been designed by ESA to promote research on the Earth's atmosphere, biosphere, hydrosphere, cryosphere and interior. Among the two other ESA missions which are scheduled for launch before the end of 2009 is CryoSAT-2, which will determine variations in the thickness of the Earth's continental ice sheets and marine ice cover to further our understanding of the relationship between ice and global warming. CryoSat-2 replaces CryoSat, which was lost at launch in 2005. The combination of GOCE and CryoSAT-2 will give us the best estimate of sea ice coverage, especially in the Arctic.
ESA has been dedicated to observing the Earth from space ever since the launch of its first meteorological mission Meteosat in 1977. Envisat, the largest satellite launched from Europe in 2002.
For more inforamtion please see: http://www.esa.int