Looking for water exchanges

By measuring the temperature of the reflection of the Earth’s surface in the microwave frequency range


Plesetsk Cosmodrome, Russia — The second satellite in ESA???s Earth Explorer series ??? the Soil Moisture and Ocean Salinity (SMOS) mission was launched into orbit on 1 November from northern Russia.

SMOS will play a key role in the monitoring of climate change on a global scale.

It is the first ever satellite designed both to map sea surface salinity and to monitor soil moisture on a global scale.

It features a unique interferometric radiometer that will enable passive surveying of the water cycle between oceans, the atmosphere and land.

SMOS is a 658-kg satellite developed by the European Space Agency (ESA) in cooperation with France???s CNES and Spain???s Centro para el Desarrollo Tecnol??gico Industrial (CDTI).

It is based on the Proteus small satellite platform designed and built by Thales Alenia Space and its payload is composed of a single instrument, the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS), developed by EADS CASA Espacio.

MIRAS is an interferometer that connects together 69 receivers mounted on three deployable arms to measure the temperature of the reflection of the Earth’s surface in the microwave frequency range.

This temperature is linked to both the actual temperature of the surface and its conductive characteristics, which are in turn linked to soil moisture for land surface and to water salinity for sea surface.

“The data collected by SMOS will complement measurements already performed on the ground and at sea to monitor water exchanges on a global scale. Since these exchanges ??? most of which occur in remote areas ??? directly affect the weather, they are of paramount importance to meteorologists” said Volker Liebig, ESA???s Director of Earth Observation Programmes.

“Moreover, salinity is one of the drivers for the Thermohaline Circulation, the large network of currents that steers heat exchanges within the oceans on a global scale, and its survey has long been awaited by climatologists who try to predict the long-term effects of today???s climate change,” Liebig added, witnessing the launch from the Plesetsk Cosmodrome.

SMOS is the second satellite launched under the Earth Explorer programme conducted by ESA to foster the acquisition of new environmental data for the science community.

It follows the Gravity and steady-state Ocean Circulation Explorer (GOCE), also launched on a Rockot, in March 2009.

Some 70 minutes after launch, SMOS successfully separated from the Rockot???s Breeze-KM upper stage. Shortly after, the satellite???s initial telemetry was acquired by the Hartebeesthoek ground station, near Johannesburg, South Africa.

Following the launch of ESA???s SMOS satellite on 2 November, the French space agency CNES, which is responsible for operating the satellite, has confirmed that the instrument???s three antenna arms have deployed as planned, and that the instrument is in good health.

During launch and the first few orbits around Earth, the Soil Moisture and Ocean Salinity (SMOS) instrument???s antenna arms remained safely folded up. Now, these three arms folded-out and now form a large three-pointed star shape.

With its unusual shape, measuring eight metres across, SMOS can be dubbed a ???star in the sky???.

Learn more at www.esa.int/esaCP/SEMM1MCUE1G_index_0.html

More Earth Explorers are already undergoing preparation. Cryosat-2, which will measure the thickness of the ice sheets, is due for launch in February 2010.

It will be followed by ADM-Aeolus to study atmospheric dynamics and the Swarm mission to monitor the weakening of the Earth???s magnetic field, in 2011, as well as by the EarthCARE mission on clouds and aerosols in 2013.

About ESA

The European Space Agency (ESA) is Europe???s gateway to space. Its mission is to shape the development of Europe???s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.

Web: www.esa.int