Artists impression of the Soil Moisture and Ocean Salinity (SMOS) satellite. Image courtesy of ESA – P. Carril.
The European Space Agency’s (ESA) Soil Moisture and Ocean Salinity (SMOS) satellite has just celebrated ten years in orbit, remarkable for a satellite whose mission life was considered to be a minimum of three years. It was launched on the 2nd November 2009 from the Plesetsk Cosmodrome aboard the Rokot-KM, which also took Proba-2 into space.
It was placed into a sun-synchronous polar orbit at around 750 km above the Earth. It crosses the equator on each orbit at 6.00am and has a repeat cycle of 23 days to pass over exactly the same point on the planet. The satellite carries the Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument, which is a 2D interferometric L-band radiometer with 69 antenna receivers distributed on a Y-shaped deployable antenna array. It has a temporal resolution of three days, with a spatial resolution of around 50 km. It uses the interferometry technique to make worldwide observations of soil moisture over land and salinity over the ocean. This double dataset helps scientists to better understand the water cycle and the exchange process between the Earth’s surface and atmosphere, which in turn enables them to improve the weather and climate modelling.
SMOS is part of the Earth Explorer research missions for ESA’s Living Planet Program which are designed to support the delivery of operational services using Earth Observation (EO) data. It is part of the series of research missions looking at key scientific issues, and to date, the program has launched:
- Gravity field and steady-state Ocean Circulation Explorer (GOCE) mission, known as ESA’s gravity mission was launched on 17 March 2009 and ended on 11 November 2013.
- SMOS, known as ESA’s water mission, the second of these missions is and also sometimes known as Earth Explorer 2.
- CryoSat, known as ESA’s ice mission launched on 8 April 2010.
- Swarm, known as ESA’s magnetic field mission launched on 22 November 2013.
- Aeolus, known as ESA’s wind mission, launched in 2018.
Planned future missions in this series already include Earth Clouds Aerosols and Radiation Explorer (EarthCARE), Biomass – ESA’s forest mission, FLEX – ESA’s plant health mission, and The Far-infrared Outgoing Radiation Understanding and Monitoring (FORUM) mission.
One of the interesting aspects of SMOS is how applications for which it’s data has been used have expanded over time. Not only has it delivered to its original mission, but its data has also been used to measure floating ice, calculate crop-yield forecasts, measure the salinity in smaller seas and hurricane forecasting to name a few!
SMOS has produced a remarkably robust datastream over the last ten years and has definitely delivered on the aim of supporting the delivery of operational services. We know as we use SMOS as part of a soil moisture operational service! To get the coverage for a daily observation we do combine SMOS with EUMETSAT’s Advanced SCATterometer (ASCAT) and NASA’s Advanced Microwave Scanning Radiometer (AMSR-2) data.
We’ve worked with SMOS data in a variety of ways and have a soft spot for this satellite. We’re delighted to celebrate its tenth anniversary and we hope it goes on for many more!
