March 17, 2009

GOCE Launches To Map Earth’s Gravity

ESA's Gravity field and steady-state Ocean Circulation Explorer (GOCE) successfully launched on schedule Tuesday with plans to provide an unprecedented view of Earth's gravity field.

GOCE launched via a Russian Rockot vehicle from the Plesetsk cosmodrome in Russia at 1421GMT on Tuesday.

Mission managers must now wait for about 90 minutes after lift-off before GOCE separates from its rocket.

GOCE was expected to launch on Monday, but technical problems forced mission managers to suspend the countdown just seven seconds before lift-off.

A spokesperson for the Khrunichev space center said the decision to postpone the launch was not influenced by a problem with the rocket or the spacecraft.

In a written statement, ESA said the doors of the launch service tower failed to open, causing the tower to stay in position "and not move back as required for launch."

The first of ESA's series of "Earth Exploring" missions, GOCE is the result of a consortium of 45 companies throughout 13 European countries. So far, ESA has approved six Earth Exploring missions; a seventh is in discussion, according to BBC News.

GOCE will use gradiometry "“ the measurement of gravitational differences an ensemble of test masses inside the satellite.

GOCE's gradiometer is the most sophisticated ever to be intended for a satellite, according to Andrea Allasio, of Thales Alenia Space in Italy.

The $450 million spacecraft will gather information necessary to record gravitational anomalies to create a map of the Earth's geoid "“ the reference surface of the planet.

The craft will provide scientists with a view of the effects of human activity in relation to climate change, sea level change and ocean circulation.

"Our current knowledge of the Earth's gravity is incomplete," Danilo Muzi, ESA's GOCE program manager, told BBC News.

"Gravity is the force we experience daily; it keeps our feet on the ground. But there is this general misconception that it is constant everywhere on the globe, which is not true. If we go to the North Pole we will weigh more than if we are at the equator."

The craft not only features revolutionary tools, its appearance also represents a change of pace from previous satellite missions.

"This is the most beautiful satellite that has ever been built - and for good reason," said Reiner Rummel, from the Technical University of Munich, Germany.

The arrow fin-shaped satellite will use QinetiQ's T5 ion thrusters to compensate for movement from atmospheric drag. Requiring only 40kgs of propellant for the whole 30-month GOCE mission, the thrusters are about ten times more efficient than rocket thrusters used in the past.

"QinetiQ's electric engines act as cruise control for the spacecraft, continuously compensating for this atmospheric drag and quite literally preventing the spacecraft from falling out of the sky," the technology firm said in a written statement.

"It has been designed to fly at an extremely low orbital altitude, just 250km (155 miles) above Earth. For this reason it has an eye-catching aerodynamic shape and will actively compensate for the air drag by using the finely controlled thrust of QinetiQ's ion engine," said Volker Liebig, Director of Earth Observation Programs at ESA.

"We are an enabling technology on this mission; it couldn't happen without us," said Neil Wallace from Qinetiq. "But then this mission has many such technologies."

Images Courtesy ESA


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