May 5, 2010

SMOS Struggling With Interference

Despite continued interference issues, Europe's SMOS satellite is transmitting valuable new data on the way water is cycled across the globe.

The satellite was launched in November to track changes in the wetness of soils and the salinity of the oceans using a microwave antenna.

The detailed maps will soon be released for the eyes of the scientific community. But there are still some issues as SMOS is blinded by radar networks and media links in some areas of the world.

The radio frequency interference is proving to be a frustration for the team. The part of the electromagnetic spectrum in which SMOS sees the planet is supposed to be reserved for Earth observation.

The problem zones are most notable in Southern Europe, the Middle East and along the Asian continent.

Dr. Yann Kerr, one of the SMOS principal investigators, told BBC News that these interferences are damaging the signal over a much larger area. Interferences in Africa, for example, particularly in Khartoum and South Africa, are affecting a good part of Africa, he added.

And Africa is "one of the areas of the world where information on soil moisture for better water resources management is crucial. So it's really a hindrance," Kerr told BBC.

The European Space Agency satellite will complete its commissioning phase in the next month, and the first results from early observations were presented at the European Geosciences Union meeting.

SMOS has a single instrument -- an interferometric radiometer called Miras. Miras measures nearly 26 feet across and has the appearance of helicopter rotor blades.

Miras measures changes in the moisture content of the soil and ocean salinity by studying variations in the natural microwave emissions (L-band) that rise from the surface of the planet. Tracking of these emissions will have broad applications, but should improve weather forecasting and warnings of extreme events, such as droughts or deluges.

Early data received suggests that Miras is performing relatively well. It has mapped out subtle features that will be of huge importance to hydrologists, meteorologists and oceanographers, as well as other fields.

During a recent rain event that soaked much of eastern Australia, Miras observed how the soil dried out over the days that followed.

"In several instances, we had phenomena that we identified but which seemed highly improbable," said Dr Kerr. "We saw banana-shaped features in the data and we wondered if it was a problem with the instrument or RFI. But then we looked with rain radars and saw exactly the same pattern, so it was obviously a rain event."

SMOS is also transmitting some fascinating data on the polar regions. Scientists can recognize where ice thins at the rocky edges of Antarctica. They are even able to see melt-water sitting on top of sea-ice.

The observations made using SMOS and Miras will be very useful to researchers studying changes in the cryosphere.

Progress is also being made in dealing with the man-made emissions that are interfering with Miras operational frequencies.

The European Space Agency is working with different authorities around the world -- such as the International Telecommunications -- to try to identify the sources of interference and shut them down. The SMOS team is also learning how to tune its algorithms to filter out some of the interferences.

The United States is also showing support for the cause. The US is expected to launch two L-band missions of its own this decade. SMAP will measure soil moisture, and Aquarius will monitor water salinity. The effort will be a joint venture with Brazil.

"In some ways it's a pity for SMOS that we are the first L-band mission in space, because we will basically look at all these things as the first people," commented Dr Susanne Mecklenburg, the SMOS mission manager.

The Chinese are possibly also working on an instrument that will hopefully help in switching off the sources over Asia, where a large part of the contamination is filtering through, Mecklenburg said.


On the Net: