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Europe is to press ahead with its Earthcare space laser mission, despite a 30% rise in its probable final cost.

The satellite will study the role clouds and atmospheric particles play in a changing climate.

But the difficulty in finding a workable design for the spacecraft's lidar instrument means its total budget will now top 590m euros (£500m).

Member states of the European Space Agency are convinced though that Earthcare will deliver invaluable data.

Delegates to the 18-nation alliance this week accepted the findings of a review that assessed the technical risks of proceeding.

They also heard a clear message from the scientific community that Earthcare would do pioneering research.

"The Programme Board confirmed the conclusions of the independent assessment," said Dr Volker Liebig, Esa's director of Earth observation.

"This re-affirmed the high scientific value of the Earthcare mission - that there are unique synergies between all the instruments and it makes no sense to remove any of them. The board is confident that all has been done to reach the mission objectives in the 'costs at completion' which are at the moment foreseen," he told ³ÉÈË¿ìÊÖ News.

Earthcare is one of Esa's proposed Earth Explorers - a series of spacecraft that will do innovative science in obtaining data on issues of pressing environmental concern.

Three missions have so far gone into orbit, returning remarkable new information on gravity, polar ice cover, soil moisture and ocean salinity.

Earthcare will study how clouds and aerosols (fine particles) form, evolve and affect our climate, the weather and air quality.

Scientists say knowledge gaps in such areas severely hamper their ability to forecast future change.

Different sorts of cloud have different effects. For example, low cloud can help cool the planet while high cloud can act as a blanket.

Developing the primary instrument on Earthcare to get at this information has proved extremely problematic, however.

Prime contractor, Astrium-France, has had a torrid time arriving at a design that will reliably work in the vacuum of space.

A fundamental re-configuration of the lidar has added significantly (140m euros) to the projected total mission cost.

It has also delayed the mission's probable launch date to 2016 - two years later than recent estimates.

Concerned about developments, member state delegations had requested a review of the project's status.

The lidar will fire pulses of ultraviolet light down into the atmosphere.

From the way this light is scattered back to the spacecraft, scientists can build up a picture of where in the atmosphere different cloud types and aerosols reside.

Combined with the data from three other instruments onboard, it should then be possible to work out the implications for the energy budget of the Earth.

"The board was asked to look into a potential de-scoping of the mission, but it was the clear view of all the scientists that the breakthrough Earthcare will deliver comes from the combination of all the instruments," Dr Liebig said.

Europe has yet to fly a space lidar mission and so developing this expertise is seen as an important technology goal for Esa.

Earth observation is currently the agency's biggest programme, representing a fifth of its total budget or 844m euros in 2011.

The extra cost of Earthcare will need to be absorbed, but Dr Liebig said the tendency of all high-technology missions to slip over time meant the additional expenditure could be managed in an affordable way.

Like all Esa missions, Earthcare will be a pan-European effort. However, the mission has particular significance for the UK.

The main structure of the spacecraft will be built in Britain (Astrium-UK at Stevenage), as will two of its instruments, at SSTL (Guildford) and SEA Group Ltd (Frome).

The fourth instrument on Earthcare is being supplied by Japan.

Jonathan.Amos-INTERNET@bbc.co.uk, external