The European Space Agency launched its CryoSat-2 satellite on a 140 million-euro ($190 million) mission to measure the thickness of ice on Greenland, Antarctica and the polar seas.

The launch from the Baikonur Cosmodrome in Kazakhstan was aired live on ESA's Web site. It comes four years after the original satellite was lost due to a failure of the launcher. About 17 minutes after liftoff, the agency confirmed the first signal from the CryoSat-2 was received in Malindi, Kenya.

"This time the launcher worked beautifully: We are in orbit," ESA Director-General Jean-Jacques Dordain said. "It's one additional contribution from ESA to better understand the planet Earth and climate change."

United Nations scientists have highlighted melting ice as a harbinger of climate change, and in 2007 said oceans will likely rise by as much as 59 centimeters (23 inches) by 2100 as a result of global warming. The loss of sea ice can increase the rate of warming by leaving dark, heat-absorbing ocean exposed.

The European Aeronautic, Defense & Space Co. satellite will use a technique called altimetry that employs radar to gauge the elevation of floating ice and grounded ice caps. The readings over the mission's 3 1/2-year lifespan will enable scientists to better monitor how quickly ice is melting as the Earth warms, according to the agency.

In its 2007 report, the UN said uncertainty surrounds the amount ice caps may contribute to sea-level rise, a statement supported by scientific studies since then, some of which show melting in Greenland and Antarctica accelerating, and others indicating a possible slowdown.

"We know from our radar satellites that sea ice extent is diminishing but there is still an urgent need to understand how the volume of ice is changing," ESA's Director of Earth Observation Programmes, Volker Liebig, said in an e-mailed statement. "To make these calculations, scientists also need information on ice thickness, which is exactly what our new CryoSat satellite will provide."