Europe at the forefront
When it comes to remote sensing for civilian purposes, Europe is today’s undisputed leader. With its roots in the 1970s, it is a success that looks all set to continue.
Earth observation for civilian purposes is a space discipline that very quickly inspired the Europeans. As early as 1977, ESA launched Meteosat 1, the first optical satellite charged with observing our world from a geostationary orbit. Devoted to meteorology, it has been followed by a series of increasingly sharp-eyed successors – we are currently at Meteosat-7 – operating at every possible wavelength, both visible and infrared. This family of satellites are in geostationary orbit at a height of 36 000 kilometres and are thus fixed above an area of the Earth’s surface that they observe continuously.
Spot, Envisat and the others
In 1978 a second series of satellites was launched: the Spot (Satellite Pour l’Observation de la Terre) family, born of cooperation between France, Belgium and Sweden. Five Spot satellites have been launched to date, travelling in lower, circular and heliosynchronous orbits at a height of 830 kilometres. The latest, Spot-5, produces images showing details of 2.5 metres on the ground in black and white (panchromatic) and 10 metres in colour (multispectral).
ESA has also developed and launched a number of scientific satellites, such as the ERS (European Remote Sensing satellite) programme of radar satellites. Two satellites of this family were built under this programme adopted back in 1982, one of which, the ERS-2, is still in orbit today. It has since been joined by the giant Envisat satellite.
However, ESA’s Earth observation resources are not limited to these major programmes alone.
‘Third party’ missions
The European Space Agency also makes its ground facilities available to third countries for the receiving, processing and archiving of images obtained by other Earth observation devices. It was in the framework of one of these third party missions that an ESA experimental satellite, the small Belgian Proba (Project for on-board Autonomy), was launched. Originally positioned in orbit in 2001, this technological demonstration satellite was supposed to remain in space for a year at the most. However, such was its operational performance that this tiny orbital platform (weighing just 100 kilograms) is today still continuing to supply ever more surprising images of our planet, thanks to its high resolution camera and compact British-made multispectral imager.
Targeting the future
Today there can be no denying the attraction of Earth observation. Many projects are in the pipeline, both in Paris, headquarters of the European Space Agency, and in Frascati, on the outskirts of Rome, home of ESRIN, the ESA centre for Earth observation programmes.
This European enthusiasm and the many projects planned for the future are attracting scientists from every continent, including the United States. “Quite simply because Europe has made it a priority, whereas the United States is at present cutting back on its Earth observation budgets,” explains Simonetta Cheli, head of public and institutional relations at ESA-ESRIN, Italy. “More and more US scientists working in this field are seeking to cooperate with European researchers so that they can benefit from the new data obtained by our orbiting instruments.”
Envisat, a “global” European success
The most ambitious Earth observation satellite ever built is a ‘child’ of ESA. Over the past five years, Envisat (ENVIronment SATellite) has been a mine of information about our planet.
Launched in March 2002, this giant among satellites (weighing eight tons and equipped with ten scientific instruments) produces 280 gigabytes of data every day.
“In April 2007, at the scientific conference in Montreux (Switzerland) on the occasion of the fifth anniversary of Envisat, more than a thousand researchers from 50 countries came to present their scientific results obtained thanks to the Envisat data,” explains Henri Laur, director of the Envisat mission at the ESA. “About 1200 scientific projects were presented. And it is not finished yet!” Envisat is set to remain operational until 2010. But even after it ceases its orbit observations, the data produced in the course of its active life will remain a first-rate source of information, continuing to be incorporated into new algorithms and to provide new information about our biosphere. “The great strength of this satellite is the vast quantity of data obtained simultaneously as its many sensors orbit the same part of the world,” continues Henri Laur. “These data relate to emerged land masses, oceans, the cryosphere, our atmosphere and of course the many interactions between these various components. This is why a growing number of the scientific results obtained by virtue of its observations concern the climate and its development.”
Among the satellite’s most remarkable instruments is the Asar imaging radar, the Aatsr thermometer, and the Meris optical sensor which is just as interested in the colours of the ocean as in the vegetation cover of the land, with a ground precision of around 300 metres.