Friday, July 6, 2012

SMOS satellite measurements improve as ground radars switch off

European Space Agency: Over a dozen radio signals that have hindered data collection on ESA’s SMOS water mission have been switched off. The effort also benefits satellites such as NASA’s Aquarius mission, which measures ocean salinity at the same frequency.

We all know what happens when you place a cell phone too close to a speaker: seconds before the phone rings, that obnoxious buzz interrupts your favourite song. This is radio interference – an unwanted reception of radio signals. Not only can it interrupt the music from your stereo, it can also impede satellite measurements.

ESA’s Soil Moisture and Ocean Salinity (SMOS) satellite was launched in 2009 to improve our understanding of our planet’s water cycle. In order to do this, it measures the microwaves emitted by Earth in the 1400–1427 MHz range. 

SMOS immediately revealed that many unlawful signals were being transmitted around the world in this frequency range, rendering some of its measurements unusable for scientific purposes. Over the years, ESA has investigated exactly where the interference is coming from.

As national authorities have collaborated with ESA to pinpoint the origin and switch these unlawful emissions off, the interference has waned. One of the largest areas of contamination in the northern hemisphere is over the North Pacific and Atlantic oceans, primarily from military radars....

In May 2011, radio frequency interference (RFI) still hindered salinity readings. Over a dozen RFIs were switched off prior to May 2012, making salinity measurements more accurate thereafter.  Credits: N. Reul, IFREMER/CATDS

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