A European satellite that monitors sea ice thickness and soil moisture is frequently being blinded over Europe and the Russian Arctic due to heavy interference since Russia’s invasion of Ukraine. The interference is in a microwave frequency that almost all countries, including Russia, have agreed to keep clear.
“Since the Russia-Ukrainian war, we have been heavily affected and we lose significant amounts of data over Europe,” at the European Space Agency told 91av.
The , launched in 2009, works by detecting faint microwave emissions from Earth’s surface. It exploits the fact that, for instance, wet soil emits more microwaves than dry soil.
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Because ice emits more microwaves than liquid water, SMOS can also detect sea ice and how thick it is up to around a metre, but can’t tell if the ice is thicker than this. It also works only in winter when there is no thawing, says at the Alfred Wegener Institute in Bremen, Germany, who works on the sea ice data.
SMOS detects microwaves with a frequency between 1400 and 1427 megahertz – this includes the 1420 MHz frequency at which hydrogen gas emits, which is important to astronomers. This band is protected by the International Telecommunication Union (ITU).
“The decision to protect the band is agreed to by all ITU member states,” says a spokesperson for the ITU.
That means these nations shouldn’t use this frequency, and that all devices should be designed to ensure they do not accidentally produce signals at this frequency. Russia is a member of the ITU.
However, there has always been some low-level interference from devices such as wireless security cameras and radios that emit at these frequencies, either because their designers were unaware of the regulations or failed to ensure there were no unintentional emissions in this range.
“As these are illegal devices, we have the means to remove them and we closely work with national authorities to do so,” says Scipal. “It is a tedious work, but we manage to keep the numbers and their impact low.”
Interference from military radars and jammers is a different matter that, in practice, nothing can be done about, he says. “We clearly see those sources in regions of geopolitical tension.”
The interference isn’t continuous, so on some orbits the satellite is still able to get useful measurements from the region, says Kaleschke. “The data quality is reduced, but we are not totally blind,” he says.
NASA’s SMAP satellite, which has a radar in addition to detecting natural microwaves, is also helping fill in some of the gaps, says Kaleschke. The SMOS and SMAP data were already being combined, he says, as SMAP’s radar can measure sea ice thickness of more than a metre, while SMOS is more accurate for thin ice.
One explanation for the interference could be Russian attempts to jam the signal that GPS-guided munitions used by Ukraine rely on, says freelance radar engineer . These operate at the frequencies of 1164 to 1215 MHz, 1215 to 1300 MHz and 1559 to 1610 MHz.
“These frequencies are actively jammed by the Russians,” he says. “It is quite possible that these jammers simply interfere in the entire range between 1200 and 1600 MHz.”
Some older radars can operate in the 1400 to 1427 frequency range, says Wolff, but he thinks it is unlikely these are being used in the war. That said, Russia’s extraordinarily high losses of equipment in Ukraine .
