ESA and EADS-CASA sign contract to build instrument for the SMOS mission

A significant milestone in the development of ESA’s Soil Moisture and Ocean Salinity (SMOS) mission was reached last week when the contract to build the payload was signed between ESA and EADS (European Aeronautic Defence and Space Company)-CASA from Spain.

The contract, worth 62 million euros, was signed in Madrid, Spain on 11 June 2004 at the premises of the CDTI (Centre for Development of Industrial Technology). EADS-CASA now heads an industrial consortium of more than 20 companies from all over Europe, and is committed to construct the innovative MIRAS (Microwave Imaging Radiometer using Aperture Synthesis) instrument that will form the core of the SMOS mission.

Scheduled for launch in early 2007, SMOS is the second Earth Explorer Opportunity mission to be implemented as part of ESA’s Living Planet Programme. The main aim of the mission is to further the development of climatological, meteorological and hydrological models by observing soil moisture over the Earth’s landmasses and sea-surface salinity over the oceans for a period of at least 3 years. At the signing ceremony, Prof. José Achache, ESA’s Director of Earth Observation Programmes, stated that, “SMOS will provide a major advancement in our ability to model and understand the global hydrological cycle.”

The moisture in soil and the salt in the oceans are intrinsically linked to the Earth’s water cycle and climate. Currently, in-situ measurements for soil moisture are sparse, but if we are to better understand the water cycle so that the forecasting of climate, weather and extreme events such as floods can be improved more data are urgently required. The same is true for data on ocean salinity – only a small fraction of the ocean is sampled on any regular basis. However, salinity is an important factor driving the currents in the ocean and in turn ocean circulation plays a crucial role moderating the climate. Therefore, comprehensive data on ocean salinity would greatly improve our knowledge of the conditions that influence global ocean circulation and thus climate.

Not only will this mission further our understanding of the Earth system, but it will also demonstrate a new measuring technique by adopting a completely different approach in the field of remote sensing. SMOS will carry the first-ever polar-orbiting satellite-borne
2-D interferometric radiometer. From an altitude of 763 km, the novel MIRAS instrument has been designed to capture images of microwave radiation emitted from the surface of the Earth at L-band (1.4 GHz).

MIRAS is made up of a central structure and three deployable arms. There are 69 antenna elements, so-called LICEF receivers, which are equally distributed over the central structure and three arms. Each LICEF is an antenna-receiver integrated unit that measures the radiation emitted from the Earth at L-band. The measuring principle takes advantage of the fact that moisture and salinity influence the emissivity of soil and seawater, respectively. From the information gathered, scientists will be able to derive maps of soil moisture and ocean salinity on a global scale.

Now that the contract has been signed to go ahead and build the payload the SMOS mission has taken a significant and exciting step forward in its development.