The €140m (£122m) CryoSat-2 is a replica built by the European Space Agency, but with some additional instruments. The satellite is currently in orbit after a successful separation and has sent communication signals which have been received by a ground team in Malindi, Kenya. The satellite will be able to measure the thickness of Arctic and Antarctic ice to within a centimetre - an accuracy unmatched until now. Lift-off was shown live online and took place during the scheduled launch of 1457 BST.
The melting of sea ice, ice caps and glaciers across the planet is one of the clearest signs of global warming and the UK-led team of scientists will use the data from CryoSat-2 to track how this is affecting ocean currents, sea levels and the overall global climate.
Duncan Wingham, a climate physicist at University College London and the lead scientist for both missions, is hoping this will be second time lucky. "Satellites have transformed our knowledge of what is happening to these distant and uninhabited parts of the planet. CryoSat-2 will help unravel the consequences of the dramatic changes in the poles that we've seen in the past two decades."
Wingham said that, without CryoSat-2, there would be a significant gap in the data needed to track climate change. "The data we do have is patchy because the instrumentation on the earlier generation of satellites was not designed to deal with the ice-sheets," said Wingham.
The first CryoSat mission was launched from the Plesetsk cosmodrome in northern Russia on 8 October 2005, but it crashed into the icy sea shortly afterwards, due to a malfunction in the launch vehicle.
Approval for a successor mission to CryoSat was given by Esa within months of the accident. The new probe was built using improved electronics and batteries, and an extra radar altimeter, a device that will fire microwaves at the Arctic and Antarctic ice to reveal its thickness.
Scientists have already shown that the amount of sea ice in the Arctic is falling, and the latest data confirms the long-term trend. But some data also suggests that the ice that remains is thinning. If the measurements from CryoSat-2 bear out this thinning theory, it would mean the ice is being lost more quickly. Scientists are concerned that the loss of sea ice is leading to a feedback effect where the newly exposed, darker ocean absorbs more sunlight, warming the water yet further. In addition, sea ice can block glaciers on land from falling into the ocean, so its loss could raise sea levels.
"We are altering the Arctic climate far faster than anywhere else on Earth," said Wingham. "We're changing the whole structure of the Arctic Ocean, but we still don't know what the consequences will be. We have to find out what is going on up there. CryoSat-2 will do that."
Another antenna on CryoSat-2 will measure the shape of the ice and tell researchers about slopes and ridges at the edges of the great Antarctic and Greenland ice sheets.
Alan O'Neill, director of the National Centre for Earth Observation at the University of Reading said: "These measurements are absolutely crucial to our understanding of climate variability and climate change. Not only are they early indicators of climate change because of feedbacks in the system. But they're not remote from what affects people's lives and the weather that affects the rest of the planet. The polar regions are connected to the rest of the planet by the atmosphere and the ocean."
Richard Francis of Esa, who led the team that built CryoSat-2, said scientists were holding their breath until launch. "There'll be a lot of relief when we acquire that signal [after launch], I can tell you."