Radar tracking stations are searching for Europe's missing Cryosat spacecraft, Lunched from Russian Plesetsk Cosmodrome amid concerns it has broken up over the ocean.
Russian space officials said the flight broke up and crashed into the sea, after it have lifted off at 19.02 local time (16.02 BST) but Esa has not yet confirmed it.
The Ј90m (135m euro) mission was designed to monitor how climate change was affecting the Earth's ice masses.
Early signs suggested the launch had been successful, but the satellite went missing some 90 minutes later.
Chief scientist Duncan Wingham of University College London said the mission was either lost or in an unknown orbit around the Earth.
He said: "Space is a risky business, it always has been.
"If we're lucky we might be in an orbit we could recover from. Until they locate it, we won't know." The satellite was launched on a Rockot vehicle, a converted SS-19 intercontinental ballistic missile, reports BBC
European Space Agency spokesman Franco Bonacina said ground stations did not see if the rocket's third stage fired to put the satellite into the correct orbit.
"We don't really know what's happening right now," he told Reuters.
The satellite was launched at about 1500 GMT on Saturday on board a Rokot launcher, which is a converted inter-continental ballistic missile.
News agencies reported that Russia's space troops had ordered a halt into all launches using the rocket until an investigation is carried out into what went wrong.
Equipment on board Cryosat is designed to allow it to take precise measurements of the polar ice caps, which some scientists believe are thinning as a result of global warming and could lead to higher sea levels.
Photo: ESA P.T.