The Gravity field and steady-state Ocean Circulation Explorer (GOCE) is one of ESA’s Earth Explorer satellites, a series of spacecraft that will improve our understanding of climate processes and changes on the planet. The scheduled launch date is Monday, 27 October 2008 at 15:21 Central European Time. [Editor's Note: The GOCE launch has recently been delayed. The new launch date is now sometime after February 2009 due to a problem with the guidance system of the launch vehicle. We will give you more information on the revised date when it becomes available.]

GOCE is designed to measure the variations in the Earth’s gravity field. The GOCE results will provide precise data to make highly accurate gravity models that will be used, amongst other things, to fine tune ocean circulation and sea level climate models. This should lead to better climate change predictions and better monitoring of the changes that are taking place on the planet.

To gather the data, GOCE will fly at only 260 kms above the surface of the Earth, skimming through the very outer edge of the atmosphere, for 20 months and carry super sensitive accelerometer packages to measure the acceleration of gravity to an accuracy of 0.00001ms-2. Earth’s gravity varies due to the non-circular shape of the planet, the uneven distribution of land and ocean, mountains and the internal structural differences within the planet.

Currently, no spacecraft launch has attempted any form of carbon neutrality.

The spacecraft looks a lot like a large futuristic dart. The solar panels (spacecraft is where solar panels originated) that power it have to withstand temperatures from -170 to +160°C as it plunges into eclipse and gets heated by the sun and Earth reflected sun energy (the Albedo Effect). There are no moving parts on the spacecraft so as not to affect the precise gravity measurements. It is around 1100kgs in weight, 5 metres long and has a Xenon-fuelled ion engine.

The GOCE spacecraft will launch from the Plesetsk Cosmodrome in Northern Russia, on a converted SS-19 Stiletto inter-continental ballistic missile (ICBM). Since the Cold War ended, these missiles have been put to better use in launching satellites rather than 5megaton nuclear warheads. The launcher is now aptly called Rockot.

However, even though GOCE and other earth observation satellites are helping us to understand the changes the earth is going through, a typical satellite launch produces hundreds of tons of polluting gases injected throughout the atmosphere. Some, like Soyuz (a launch vehicle used by the Russians), use kerosene and so its carbon footprint for a launch is approximately 700 tons, which is about the carbon footprint of 120 typical North American cars driven for a year.

Other launcher vehicles use highly toxic chemicals, like the ICBMS and the noxious chemicals in the boosters are much worse for the environment than kerosene. Currently, no spacecraft launch has attempted any form of carbon neutrality.


Find information about the ESA-ESTEC GOCE mission: http://www. esa. int/esaLP/LPgoce. html
A GOCE stimulation: http://www. esa. int/SPECIALS/GOCE/SEMNVU3G6KF_1.html#subhead1

Trevor Williams is a University of Victoria Mechanical Engineering PhD candidate specialising in renewable energy, power grid modelling and plug-in hybrid electric vehicles. He has a bachelors in Aeronautical Engineering, a Masters in Management Science and over 23 years international experience in the space industry, having worked on Earth observation and telecommunications satellites.

Via:www.greenmuze. соm

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