The eight tonne, ten-meter (33-foot) long module and its 10 data-collecting instruments, have also proved to be so reliable that it will now carry on for another five to seven years, said mission director Henri Laur.

More than 900 scientists gathered in the Swiss lakeside town of Montreux this week for an ESA conference on satellite observation of the world's land, oceans, ice and atmosphere, which also marked Envisat's fifth anniversary.

The 250 gigabytes of data the satellite beams to earth every day has allowed them to literally map out changes in levels of pollutants from industry or transport or even to spot oil tankers that illicitly clean out their tanks on the high seas.

"You can see the impact of economic change on the environment," Laur said.

"Emissions have remained stable in Europe and the United States but have increased sharply in China," he explained.

A spectometrer on the satellite can measure levels of carbon dioxide and methane -- two of the main greenhouse gases blamed for climate change -- in the earth's atmosphere.

"Our understanding of the phenomenon has benefitted enormously from satellite observations," Laur underlined. "There are many things that we would not have seen otherwise."

Envisat, which fits into a network of earth observation satellites, helped determine the speed of the meltdown of glaciers in Greenland, which has doubled in the space of 10 years.

It also revealed a three millimetre increase in sea levels, and the extent of the warming of the oceans, according to ESA.

Another instrument, a radar altimeter, can measure the rate of thinning of the melting polar icecap, even at night or beneath cloud cover.

The 230 technicians at ESA's data processing centre at Frascati, Italy, have also been used to spot deliberate environmental damage by oil tankers venting their tanks.

Since oil is heavier than water, the satellite can spot the telltale hyrdocarbon trail because its smoothes the surface waves of the sea.

"Envisat is well known to tanker captains," Laur said.

"We think that they know our orbit, when we pass overhead," he added.

Laur said observations by Envisat helped to reduce illegal fishing off France's Kerguelen Islands in the Indian Ocean by 90 percent.

Envisat is likely to be replaced after 2012 by an armada of smaller satellites called "Sentinel", each with a specialised task in observing the chemistry of the earth's atmosphere.

However, ESA is still seeking funding from its 17 member states for the broader project, which would allow continued European monitoring of greenhouse gases.

Laur said the meeting in Montreux, which ends on Friday, underlined that such monitoring was "very important."

Email This Article

Related Links
Envisat
Making money out of watching earth from space today