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  • richardmitnick 7:58 am on July 31, 2014 Permalink | Reply
    Tags: , , , , , ESA GOCE   

    From ESA: “Lifetime of Gravity Measurements Heralds New Beginning” 

    ESASpaceForEuropeBanner
    European Space Agency

    30 July 2014
    No Writer Credit

    Although ESA’s GOCE satellite is no more, all of the measurements it gathered during its life skirting the fringes our atmosphere, including the very last as it drifted slowly back to Earth, have been drawn together to offer new opportunities for science.

    ESA GOCE Spacecraft
    ESA/GOCE

    Carrying the first 3D gravity sensor in space, this state-of-the-art satellite measured Earth’s gravity with unprecedented accuracy.

    GOCE’s four years in orbit resulted in a series of four gravity models, each more accurate than the last. These models have been used to generate corresponding ‘geoids’ – the surface of a global ocean moulded by gravity alone.

    Shaped by differences in gravity, the geoid is a crucial reference for understanding ocean circulation, sea-level change and ice dynamics.

    2011
    2011 GOCE geoid

    From a mission that just keeps giving, a fifth model has now been produced. It incorporates data collected throughout the satellite’s 42-month operational life.

    The previous geoid, released in March 2013, was based on 27 months of measurements.

    The satellite was designed to orbit at an extremely low altitude of 255 km to gain the best possible gravity measurements. At the end of 2012, low fuel consumption allowed operators to extend its life and start to lower the satellite a further 31 km for even more accurate measurements. This was at the very limit of its capability but maximised the return for science.

    After more than doubling its planned life in orbit, the satellite ran out of fuel and drifted back into the atmosphere in November 2013.
    GOCE reenters atmosphere

    The fifth gravity model and geoid, which ESA has recently made available, includes these final precious measurements, right up until the satellite finally stopped working and ironically succumbed to the force it was designed to measure.

    Although the satellite is no longer in orbit, scientists now have the best possible information to hand about Earth’s gravity, effectively a new beginning for the mission.

    GOCE has already shed new light on different aspects of Earth and surpassed its original scope in a number of ways.

    It is being used to understand how oceans carry huge quantities of heat around the planet and to develop a global height reference system.

    It has provided information about atmospheric density and winds, mapped the boundary between Earth’s crust and upper mantle, and used to understand what is going on in these layers far below our feet.

    layers
    Moho and lithosphere

    And its achievements include mapping a scar in Earth’s gravity caused by the 2011 Japanese earthquake.

    The ultimate geoid model and gravity data will be used for years to come for a deeper understanding of Earth.

    scar
    Gravity scar over Japan

    ESA’s GOCE Mission Manager, Rune Floberghagen, said, “We are very happy with the results of the final, super-low altitude phase of our mission.

    “In fact, efforts made by the mission team and by scientists to secure flight operations at these extreme altitudes and to process the data have resulted in a doubling of the information content and a very significant increase in spatial resolution.

    “Indeed, our new ‘Release 5 solutions’ go well beyond the ambitious objectives we had when the GOCE project started.

    “Scientists worldwide now have a satellite-based gravity field model at hand that will remain the de facto standard for many years to come.”

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 11:32 am on March 8, 2013 Permalink | Reply
    Tags: , , ESA GOCE,   

    From ESA: “GOCE: the first seismometer in orbit” 

    ESASpaceForEuropeBanner
    European Space Agency

    8 March 2013

    Satellites map changes in Earth’s surface caused by earthquakes but never before have sound waves from a quake been sensed directly in space – until now. ESA’s hyper-sensitive GOCE gravity satellite has added yet another first to its list of successes.

    ESA GOCE Spacecraft
    GOCE

    Earthquakes not only create seismic waves that travel through Earth’s interior, but large quakes also cause the surface of the planet to vibrate like a drum. This produces sound waves that travel upwards through the atmosphere.

    The size of these waves changes from centimetres at the surface to kilometres in the thin atmosphere at altitudes of 200–300 km.

    Only low-frequency sound – infrasound – reaches these heights. It causes vertical movements that expand and contract the atmosphere by accelerating air particles.

    Since it was launched in 2009, GOCE has been mapping Earth’s gravity with unrivalled precision, orbiting at the lowest altitude of any observation satellite. But at less than 270 km up, it has to cope with air drag as it cuts through the remnants of the atmosphere.

    The cleverly designed satellite carries an innovative ion engine that instantly compensates for any drag by generating carefully calculated thrusts. These measurements are provided by very precise accelerometers.

    While the measurements ensure that GOCE remains ultra-stable in its low orbit to collect ultra-precise measurements of Earth’s gravity, atmospheric density and vertical winds along its path can be inferred from the thruster and accelerometer data.

    Exploiting GOCE data to the maximum, scientists from the Research Institute in Astrophysics and Planetology in France, the French space agency CNES, the Institute of Earth Physics of Paris and Delft University of Technology in the Netherlands, supported by ESA’s Earth Observation Support to Science Element, have been studying past measurements.”

    See the full article here.

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA Technology


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