Update: On October 21, 2013, the ESA announced that the GOCE mission had officially come to an end with the satellite’s fuel tanking running out of Xenon. The ESA has a web page set up for the latest information about the scientific results and reentry for GOCE.
September 13, 2013: Launched on March 17, 2009 by the European Space Agency (ESA), the low altitude satellite GOCE is set to run out of fuel around October of this year. GOCE, which stands The Gravity field and steady-state Ocean Circulation Explorer was launched with the purpose of mapping the Earth’s gravity field at a high level of detail.
After collecting data from altitudes ranging between 255 and 235 km, the GOCE satellite carried a gravity gradiometer which was used to calculate density differences in the crust and oceans of the Earth. The end result was the most accurate model of the geoid ever produced.
According to the ESA, the new geoid model is “crucial for deriving accurate measurements of ocean circulation, sea-level change and terrestrial ice dynamics. The geoid is also used as a reference surface from which to map the topographical features on the planet. In addition, a better understanding of variations in the gravity field will lead to a deeper understanding of Earth’s interior, such as the physics and dynamics associated with volcanic activity and earthquakes.”
The image below represents the new geoid model produced by GOCE data. With blue for the low values and red/yellows for high values, the image shows deviations in height (–100 m to +100 m) from an ideal geoid.
The GOCE mission captured data that enabled it to measure other features such as the moho (short for Mohorovičić discontinuity); the boundary between Earth’s crust and mantle. The European Space Agency agency produced the first global high-resolution map of the moho from data from ESA’s GOCE gravity satellite via its the GOCE Exploitation for Moho Modelling and Applications project – or GEMMA.
The moho was named after Croatian seismologist Andrija Mohorovičić who discovered in 1909 that there is a change in seismic speed 50 km under the earth’s surface. The earth’s moho ranges from about 70 km in depth in mountainous areas, like the Himalayas, to 10 km beneath the ocean floor.
For the first time, it is possible to estimate the Moho depth worldwide with unprecedented resolution, as well as in areas where ground data are not available. This will offer new clues for understanding the dynamics of Earth’s interior, unmasking the gravitational signal produced by unknown and irregular subsurface density distribution.
Another unexpected benefit was the measurement of earthquakes. Scientists analyzing data from the satellite discovered after the 2011 Japan earthquake that GOCE sensed the displacements caused by the Earth’s atmosphere.
Most of GOCE is expected to disintegrate in space but some parts may enter the Earth’s atmosphere. ESA’s Space Debris Office will be monitoring the descent and will report on reentry predictions and risk assessments.