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Overachieving SMOS mission primed for continued success

27 Mar 2023

SMOS in orbit

ESA’s Soil Moisture and Ocean Salinity mission (SMOS) was the second Earth Explorer launched in 2009. Over 13 years on, having already vastly exceeded its predicted lifetime and initial objectives, the mission has been further extended until at least the end of 2025.

SMOS carries a one-of-a-kind instrument, an L-band radiometer (MIRAS) that measures variations of faint microwave emissions associated with soil moisture and sea surface salinity.

Measuring soil moisture helps us better understand hydrology, for example drought and flood risks. Monitoring sea surface salinity, meanwhile, improves our ability to discern ocean circulation. Both parameters are essential for climate predictions.

The continuous 13 year ‘climate dataset’ of SMOS now supports the monitoring of essential climate variables as part of ESA’s Climate Change Initiative (CCI), the Copernicus Climate Change Service (C3S), and the Intergovernmental Panel on Climate Change (IPCC) annual report, amongst others. 

Experimental explorer to essential climate dataset

One of the major successes of ESA’s Earth Explorer is that its pioneering missions, whilst being primarily responsible for introducing new Earth Observation technologies, have gone above and beyond to become integral to operational services.

For well over a decade SMOS has met its initial objective of providing in-situ validated, highly accurate global maps of soil moisture every three days and sea surface salinity averaged every 10-30 days.

More recently the mission has been able to provide daily estimates of sea ice in the Northern Hemisphere, with datasets combining with those of ESA’s ice mission, CryoSat, into a novel sea ice thickness product. The product portfolio now also includes soil freeze/thaw and ocean extreme winds.

A major step was when SMOS became the first ever Earth Explorer mission to provide data in near-real time, an asset that opened up operational uses.

Since 2019 the mission’s data have been integrated by the European Centre for Medium-Range Weather Forecasts (ECMWF), improving the accuracy of its global weather forecasts. SMOS data are also assimilated by the Copernicus Marine service (CMEMS) Arctic Model System, and hurricane forecasters worldwide.

An ever-expanding range of applications

Versatility is another tenet of ESA’s Earth Explorer missions, and SMOS continues to find new applications.

Vegetation has been an area of particular focus in recent years. Drought monitoring has proved invaluable in predicting vegetation health and agricultural yield, giving a boost to food security in data-scarce regions.

In a 2019 study, SMOS data were used along with that of NASA and JAXA to show that forest degradation was the primary driver of carbon loss in the Brazilian Amazon. Similar work has been applied to measure the impact of climate change and land-use on the forests and savannas of Africa.

The unique multi-angular viewing capability of SMOS that allows for the simultaneous retrieval of soil moisture and vegetation has also enabled SMOS to help map ocean acidification thanks to its sea surface salinity data.

Other applications include emergency management of forest fires, and an improved ability to predict locust invasions, as well as risks from mosquito-borne illnesses and cholera.

SMOS has even taken on space weather. Thanks to its wide field of view, the satellite captures images from the sun as well as Earth, allowing us to detect solar radio bursts associated with solar flares. Moreover, SMOS data can track the progression of the roughly 11 year solar cycle. 

The first SMOS for Space Weather workshop recently explored further innovation in this area, including the use of machine learning methods to incorporate SMOS data into space weather models.

To 2025 and beyond

Though SMOS will be well into its second decade in orbit come 2025, it remains unique. There’s no instrument quite like it in orbit. A major goal of the next extension period is therefore to continue the provision of its L-band radiometer data until those of a follow-on mission become available.

One such mission is Copernicus Imaging Microwave Radiometer (CIMR). Set to launch in 2028, CIMR will continue the legacy of SMOS to monitor sea-surface temperature, sea-ice concentration and sea-surface salinity. 

“SMOS has led to countless societal benefits that will improve Earth Observation and essential operational services for many years to come,” says SMOS Mission Manager, Klaus Scipal.

“With the IPCC’s most stark report yet highlighting the multiple imminent threats posed by climate change, it is paramount that invaluable climate records like that of SMOS continue to inform decision makers. We’re excited to see what the mission continues to offer through to 2025 and beyond.”