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| | | | | | | | | GOCE in orbit | |
ESA's gravity mission GOCE
Launched on 17 March 2009, ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) was developed to bring about a whole new level of understanding of one of Earth's most fundamental forces of nature – the gravity field.
Dubbed the 'Formula 1' of satellites, this sleek high-tech gravity satellite embodies many firsts in its design and use of new technology in space to map Earth's gravity field in unprecedented detail. As the most advanced gravity space mission to date, GOCE will realise a broad range of fascinating new possibilities for oceanography, solid Earth physics, geodesy and sea-level research, and significantly contribute to furthering our understanding of climate change.
Although invisible, gravity is a complex force of nature that has an immeasurable impact on our everyday lives. It is often assumed that the force of gravity on the surface of the Earth has a constant value, but in fact the value of 'g' varies subtly from place to place. These variations are due to a number of factors such as the rotation of the Earth, the position of mountains and ocean trenches and variations in density of the Earth's interior.
| | | GOCE to map gravity as never before |
Over its life of about 20 months, GOCE will map these global variations in the gravity field with extreme detail and accuracy. This will result in a unique model of the 'geoid', which is the surface of equal gravitational potential defined by the gravity field – crucial for deriving accurate measurements of ocean circulation and sea-level change, both of which are affected by climate change. GOCE-derived data are also much needed to understand more about processes occurring inside the Earth and for use in practical applications such as surveying and levelling.
| | GOCE takes six simultaneous measurements of the gravity field | |
Since the gravitational signal is stronger closer to Earth, the 'arrow-like', five metre-long GOCE satellite has been designed to cut through what remains of Earth's atmosphere at just 250 km above the surface. This low-orbiting satellite is the first mission to employ the concept of 'gradiometry' - the measurement of acceleration differences over short distances between an ensemble of proof masses inside the satellite.
GOCE is equipped with three pairs of ultra-sensitive accelerometers arranged in three dimensions that respond to tiny variations in the 'gravitational tug' of Earth as it travels along its orbital path. Because of their different positions in the gravitational field they all experience gravitational acceleration slightly differently. The three axes of the gradiometer allow the simultaneous measurement of six independent but complementary components of the gravity field.
In order to measure gravity, there can be no interference from moving parts so the entire satellite is actually one extremely sensitive measuring device.
Mission objectives
- to determine gravity-field anomalies with an accuracy of
1 mGal (where 1 mGal = 10–5 ms–2).
- to determine the geoid with an accuracy of 1-2 cm.
- to achieve the above at a spatial resolution better than
100 km.
Last update: 15 January 2010 | |
| | More information ESA's Gravity Mission - GOCE Brochure (revised) 2006 (pdf)ESA's Schwerkraft Mission - GOCE Brochure (German) 2007 (pdf)Poster archive Earthnet Online - GOCE
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