When the ERS project began, it was seen as providing a remote-sensing satellite to provide systematic, repetitive, global coverage of the ocean, coastal zones and ice caps. It soon took on an "environmental" mantle. The ERS 1 has exceeded its planned operational life by 50% and has acquired, more than half a million radar-images, of all parts of the world. It has revolutionised many areas of Earth sciences.

Demand for its images has exceeded all expectations and is growing by 30% a year, with thousands of scientific, academic and industrial users all over the world. About 60% of the data goes free of charge to 270 research teams headed by principal investigators, while 7% is purchased by commercial users, largely through the ERS Consortium of Eurimage (Italy), Spot (France) and Radarsat (Canada).

The ERS 1 has monitored oil slicks from tanker disasters; determined the extent of flooding; measured tectonic movements after earthquakes; mapped the ocean floor under the Arctic ice cap; and revealed more details about climate-affecting phenomena, such as the Pacific Ocean's El Nino current.

An immediate practical application of ocean data, for example, is that merchant and other ships are able to steer clear of headwinds and heavy seas, using wind-speed and wave-height data from the ERS. This could lead to a 5% reduction in fuel consumption by the world's merchant fleet, twice paying the manufacturing costs of the satellite, says ESA.

The ERS 1 will be operated in tandem with the ERS 2 for a period, thanks to emergency funding which averted the threatened shutdown of the ERS 1, which is well past its lifetime, but remains in good working order. The ERS 2 is designed to operate until 1998 and will be succeeded by ESA's next-generation Earth-observation spacecraft, the Envisat. Extensive re-use of available technologies has enabled ESA to keep ERS 2 development to a $650 million budget, 60% of the cost of the ERS 1, which went over budget and was launched four years later than planned.

By operating the satellites in tandem, the number of measurement points for the radar altimeter will be doubled, improving global climatic monitoring. More accurate, synthetic-aperture radar (SAR)-derived, three-dimensional digital maps of the land surface will also result as images are returned of specific areas, providing anything from high-value cartographic products to measurements of the shifts within a few centimetres of the Earth's crust.

Combinations of two or three frames, of the same area taken on different dates, in a different primary colour, digitally analysed or superimposed, allows the SAR to reveal changes in the structure and humidity of the Earth's surface.

Source: Flight International