The Soil Moisture and Ocean Salinity satellite launched this month will monitor climate change. SMOS is the first satellite designed to map sea surface salinity and to survey soil moisture on a global scale.

The SMOS mission was conceived in 1988 and developed by the Centre d'Études Spatiales de la Biosphère or Cesbio, which uses instruments in space to study how the Earth's major ecosystems function. Cesbio is based in Toulouse, a mixed French laboratory combining the National Centre for Scientific Research, the University Paul-Sabatier, the National Space Studies Centre (CNES) and the Institute of Research for Development.

"To take measurements regularly and frequently covering the whole of the Earth, we had to find a way of collecting data from space," said Yann Kerr, Director of Cesbio and principal SMOS investigator attached to the ESA.

The laboratory devised a set of antennae mounted on an eight-metre-wide Y-shaped structure to detect moisture from land surfaces and the saltiness from oceans. In orbit, it will be possible to obtain images every three days with a resolution of about 40 kilometres.

Knowledge about the ocean's salinity and how it evolves will make it possible to identify and trace the sea currents that, following the Gulf Stream, play an essential part in climate changes. By studying soil humidity and growth of vegetation, SMOS will provide basic information to improve weather forecasting and anticipation of extreme conditions.

The satellite was developed by the ESA in cooperation with CNES and Spain's Centro para el Desarrollo Tecnológico Industrial.

SMOS is the second satellite in the ESA's Earth Explorer programme which promotes acquisition of new environmental data for the scientific community. It follows the Gravity and steady-state Ocean Circulation Explorer (GOSE) launched in March.

Future Earth Explorers will measure thickness of ice-sheets, study atmospheric dynamics, monitor weakening of the Earth's magnetic field and survey clouds and aerosols.

SMOS was launched from Plesetsk in northern Russia along with a demonstration satellite from the ESA's Project for Onboard Autonomy, Proba-2.

This follow-up to Proba-1, launched in 2001, will demonstrate 17 advanced satellite technologies such as miniaturised sensors for future ESA space probes and a highly sophisticated CCD camera with a wide-angle view of about 120°, while carrying a set of four scientific instruments to observe the Sun and study the plasma environment in orbit.

jane.Marshall@uw-news.com

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