Airbus Defence and Space

SMOS – a many-studded star

The water mission

Thanks to a ‘technological revolution’ led by Airbus Defence and Space in Spain, the SMOS mission is delivering something completely new in the history of Earth observation – the measurement from space on a global scale of soil moisture over landmasses and salinity levels in oceans.

The MIRAS instrument flown on SMOS is a technological masterpiece, the product of more than 10 years of R&D under the leadership of Airbus Defence and Space in Spain

The MIRAS instrument flown on SMOS is a technological masterpiece, the product of more than 10 years of R&D under the leadership of Airbus Defence and Space in Spain © Airbus Defence and Space

These two parameters, for both of which there has hitherto been a paucity of data, are of key scientific interest as they are determining factors in the world’s hydrological cycle processes (evaporation, precipitation, filtration, and ocean current patterns). Data from the mission give insights into how climate change is affecting the water cycle, with myriad benefits for meteorology, climatology, water resource management, risk management, and agriculture

The sole instrument is MIRAS (Microwave Imaging Radiometer using Aperture Synthesis), the real star of the mission and the result of over 10 years of research and development. It collects observations by measuring microwave radiation emitted from the Earth’s surface – based on the contrast between the electromagnetic properties of liquid water and dry soil, and between fresh and saline water. The huge inherent challenge was that, to do this, it needs to operate in L-band, long wavelength, classically requiring a very large antenna, which would be too big to be carried on a satellite … 

SMOS © ESA / AOES Medialab

SMOS © ESA / AOES Medialab

 

The ingenious solution was to design a Y-shaped configuration studded along its three arms with a multitude of tiny antenna receivers which in correlation ‘mimic’ a much larger antenna aperture. This structure could be folded up for launch and unfurled once the satellite was in its operational orbit. With a deployed diameter of eight metres, MIRAS is actually bigger than its host satellite, and is what gives SMOS its distinctive three-pointed form.

For the first time, data on soil moisture and sea-surface salinity have been combined on one map. (© Cesbio, Ifremer, CATDS)

For the first time, data on soil moisture and sea-surface salinity have been combined on one map. © Cesbio, Ifremer, CATDS

 

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