GOCE achieves a satellite first

PARIS, May 26 (UPI) -- The European Space Agency says its GOCE spacecraft has achieved a first in the history of satellite technology -- remaining completely free from drag.

"I am very pleased to see another world premier by GOCE, after having already demonstrated the most sensitive gradiometer technology ever flown in space," Volker Liebig, ESA's director of Earth observation programs, said.

Launched March 17, GOCE -- the Gravity field and steady-state Ocean Circulation Explorer -- is designed to measure Earth's gravity field with unprecedented accuracy. However, that means the satellite has to orbit Earth as low as possible where the gravitational signal is stronger, but also where the fringes of the atmosphere remain.

The ESA said GOCE is able to achieve drag-free flight by employing an electric ion propulsion system mounted at the back of the satellite, relative to its direction of flight. Unlike conventional fuel-driven engines, the system uses electrically-charged xenon to create a gentle thrust, the space agency said. The system continually generates tiny forces, depending on how much drag the satellite experiences as it orbits Earth.

GOCE was recently switched to drag-free mode as part of its commissioning and instrument calibration activities and the system was found to work perfectly.

During its life of about 24 months, GOCE will map global variations in the Earth's gravity field with extreme detail and accuracy.