Green eye in the sky

FOR three minutes, the night sky lit up on March 1, 2002, at the European Space Agency (ESA) launch centre at Kourou in French Guiana on the northern coast of South America. It was from here that an Ariane-5 rocket blasted off and put into orbit ENVISAT - the largest and most expensive satellite ever built in Western Europe. And with this development, a new chapter in the monitoring of the world's environment was scripted.

Carrying 10 unique instruments falling into three categories (see box: Fully loaded satellite), the 8.5-tonne, 25-metre-high ENVISAT is as big as a double-decker bus. Satellites of ENVISAT's size are unlikely to be launched again. "It's the last of the dinosaurs," says one UK digital sensing expert. The flying behemoth will revolve around the earth every 100 minutes and will provide unprecedented data on the health of the sick earth. Apart from studying other things, the satellite will sense the warmth of the oceans, the height of the waves, count plankton, measure algae, map rainforests and grassland, gauge snow and ice cover and garner information on greenhouse gases, global warming and the status of ozone layer. It will give a comparative picture of all the interactive elements which will assist political decision-making on climate change. "ENVISAT will be the first satellite to contribute to monitoring of compliance of the Kyoto Protocol," says Harmut Grassl, former director of the World Climate Research Programme. Scientist John Burrows of University of Bremen concurs and feels that the satellite is "an effective instrument for monitoring the Montreal and Kyoto treaties".

The total cost of the ENVISAT programme is US $2 billion, distributed over 15 years. ENVISAT represents not just huge investments but years of painstaking research and preparation by 14 different countries - the 13 members of the ESA and Canada - as well. The satellite has been built by a 50-company team including British firm Astrium, which was lead contractor for the satellite superstructure. It is designed to operate in a sun-synchronous orbit for five years. Although there were glitches hours before take-off, in the end it was all's well that ends well for the manufacturers and the scientists involved in the project. The successful launch of ENVISAT not only re-establishes the reliability of the Ariane- 5 rocket, it is also a comeback of sorts because in June 1996 the rocket's maiden test met with failure and exploded 37 seconds after lift-off. The result: four uninsured scientific satellites worth US $500 million crashed into mangrove swamps.