# European Space Agency (ESA)
Earth Observation Satellites

ERS-1 ERS-2 AMI/SAR Future

Today's environmental threats lie just over the horizon : deforestation ... the greenhouse effect ... the ozone hole - global problems calling for a global research effort and global solutions.

Part of the answer lies in space because only satellites have the global overview it takes to deliver the continuous flow of environmental measurements we need for a fuller understanding of the Earth as a living system.

Europe's contribution to this effort began with Meteosat. It is continuing with ERS-1 and ERS-2, the complex forerunners of a new generation of even more ambitious ENVISAT, METOP and Meteosat second generation missions.

## METEOSAT

Meteosat's weather images are an everyday feature of European television. But most of us are not aware of how dependent we all are upon accurate weather forecasting, needed especially in the fields of electrical power generation, public works, agriculture, road and air traffic control.

Meteosat-1, was launched in 1977, followed by five other satellite of the same family in 1981, 1988, 1989, 1991 and 1993. Three of them are currently still in service. The 7th Meteosat is scheduled for launch as from 1997. Each is equipped with an imaging radiometer, a special telescope to measure the radiance of the Earth and its cloud cover in the visible, thermal infrared and water-vapour spectral bands.

The Meteosat satellites are financed and owned by Eumetsat, an international organisation of 17 European weather services. ESA was responsible for developing and launching the spacecraft, and until the end of 1995 also operated them on behalf of Eumetsat.

## ERS

ERS-1 is the most sophisticated Earth observation satellite ever developed in Europe. It weighs well over two tons and, fully deployed, covers almost 12 metres Ñ a big bird circling the Earth once every 100 minutes, 780 km up, beaming down data at a mind-boggling 120 megabits per second.

ERS-1's payload consists essentially of two specialised radars plus an infrared sensor. The Active Microwave Instrument - the biggest on-board system - produces extremely detailed images of a 100 km swath of the Earth's surface : 4.5 million pixels per second, downlinked directly to Earth. In wind and wave modes, the instrument measures continuously and globally wind speed and direction and ocean wave parameters.

The Radar Altimeter, the second instrument, measures with fantastic precision variations in the satellite's height above sea-level and ice. And the third Instrument, the Along-Track Scanning Radiometer, constructs detailed pictures of the thermal structure of the seas and oceans from surface temperature measurements correct to better than O.5 degrees Celsius.

In April 1995, ESA launched ERS-2, a carbon copy of ERS-1 with one important difference: ERS-2's payload includes a new instrument (GOME), purpose-designed to measure stratospheric and tropospheric ozone - an important step in the race to fully assess yet another environmental challenge. No other satellite can compete with ERS capabilities. On a global scale ERS is giving scientists more confidence in modelling the climate of our planet. Regionally it keeps a close eye on coastlines, marine pollution and land use changes.

ERS-1 Overview
ERS-2 Takes Over Where ERS-1 Left Off
Active Microwave Instrument (AMI)/Synthetic Aperture Radar (SAR)
Future of ESA Earth Observation

ESA/ESRIN User Service