By Helen Briggs
BBC News science reporter, Frascati
Mission control is growing increasingly concerned about the fate of Europe's ice monitoring spacecraft, Cryosat.
The £90m (135m euro) satellite was launched at 1902 local time (1602 BST) from the Plesetsk Cosmodrome in northern Russia.
It was due to make a circuit of Earth before separating from the upper stage of the rocket 90 minutes after launch.
But mission controllers have failed to receive the signal from the spacecraft indicating the procedure was a success.
Volker Liebig, director of Earth Observation Programmes at the European Space Agency, said it did not mean the mission was lost but it raised concerns among all the teams involved.
"We have no information on what the status of the mission is - whether separation has taken place or not and whether the satellite is healthy," he told scientists gathered at Esa's European Space Research Institute, in Frascati, near Rome, to watch the launch by satellite link.
They had clapped and cheered as the rocket cleared the dense forest around the launch pad and headed into orbit.
The satellite carries a sophisticated radar altimeter that will measure the height and angle of ice surfaces with unprecedented precision.
The data returned on the three-year European Space Agency mission will help test ideas about climate change.
It rode into space on a Rockot vehicle, a converted SS-19 intercontinental ballistic missile.
The rocket, which in the Cold War would have been armed with nuclear weapons, has been modified for peaceful space duties.
Professor Chris Rapley, director of the Cambridge-based British Antarctic Survey, said the mission will provide definitive data on the Earth's polar regions.
"Cryosat is going to open up a completely new window on how the ice masses of the Earth are behaving, in particular the sea ice," he told the BBC News website.
"We saw reports recently about how the Arctic has the lowest extent of sea ice ever so that's quite some concern, but it will also tell us about whether the ice sheets are shrinking or growing.
"We know that in some parts they are growing but we know that in other parts that they are losing ice and Cryosat is going to give us the definitive data on that."
From a final altitude of 720km, it will get an outstanding view of the world's ice fields.
It will fly over both the Arctic and Antarctic with each trip around the planet, in an orbit that takes it to within a couple of degrees of the poles.
Cryosat is the first of Esa's so-called Earth Explorer missions. These are relatively low-cost projects that seek quick answers to some important environmental questions.
THE EARTH'S ICE COVER
Two types of polar ice: The ice that covers land and the ice that floats on the sea
The large Greenland and Antarctic ice sheets cover 10% of the Earth's land area
Surface measurements and overflights suggest Greenland's ice is undergoing melting
Data from the Antarctic points to melting at the edges and some growth in central regions
Considerable thinning of Arctic sea ice has been recorded by nuclear subs since the 1950s
Observations from space are more extensive, but overall there remains a paucity of data
In the case of Cryosat, the quest is for some definitive data on the behaviour of polar ice.
Previous satellite measurements, submarine and surface readings point to rapid melting in some areas, particularly in the Arctic Ocean where the extent of summer ice has just reached a record minimum this year.
But Cryosat's unique radar altimeter will see ice masses at vastly improved resolutions, even picking details at the edges of ice bodies where steep slopes and sharp shelving have challenged previous observations.
It will give superior information not just on ice extent but on ice volume, too, which is critical to understanding the scale of any melting trend. The data will be fed into computer models to improve their simulations of future climate change.