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Wednesday, May 21, 2014

Earth Scientists React to Possible Loss of Russian GPS Stations

As reported by ScienceInsider:  A Russian government threat to disconnect 11 GPS receivers used for geophysical research and to fine-tune the satellite navigation system is drawing concern from scientists—and questions from the country’s minister for industry.

The threat is just one element of the tit-for-tat diplomatic and rhetorical firefight that has broken out between Russia and the United States in the wake of Russia’s annexation of Crimea in Ukraine. Last week, senior Russian officials said they were considering an array of moves aimed at U.S. space programs, including pulling out of the International Space Station in 2020 and barring the use of Russian rocket motors by U.S. firms. Officials also threatened to turn off 11 land-based GPS receivers on Russian soil by 1 June unless the United States agreed to install similar units for Russia’s GLONASS satellite navigation system on U.S. territory.

Experts say the shutdown—if carried out—would have little impact on the GPS. The passive stations, which only receive GPS signals, are primarily used to ensure correct tracking of GPS satellites. “As these stations are very few, their impact on the accuracy of the positional measurements is insignificant,” says Konstantin Kuimov, head of the Moscow State University department of astrometry and time service. “The accuracy of the positioning at present is the question of decimeters. Now, it would worsen a little bit.” GPS users won’t notice any change, he says.

The impact on science, however, could be a bit greater. That’s because earth scientists use data from the receivers to track the slow, subtle movements of continents and land surfaces. “The situation with geophysical measurement is much worse” because the receivers are vital to providing “a serious set of statistical data,” Kuimov says. “The statistical data makes it even possible to measure the variations in the rotation of the Earth and the seismic activity of the planet. It is only the positioning satellites that make it possible to measure the [movements] of the surface in millimeters.” 

Researchers use both navigation systems—GPS and GLONASS—to make such measurements, Kuimov notes. So he and other researchers would like to see GLONASS stations on U.S. territory (a move that has been under negotiation). Ideally, he says, such stations ultimately would be evenly spaced around the world.

If Russia follows through with the threat, the impact will depend on how long the base stations remain inaccessible, says Jeffrey Freymueller, a geophysicist at the University of Alaska, Fairbanks. “If the Russians eventually share the data, we’ll be able to reprocess everything and eventually recover full precision results, but if they actually remove the equipment for the long term then over time it will become an increasing problem, as it will compromise the global coverage,” Freymueller says. “Before there were these stations in Russia, for example, it was difficult to do large-scale tectonic studies in China because we could not define what was the stable Eurasian plate well enough to express motions relative to stable Eurasia. Eventually, we will slip back toward that situation if there is no continuing data from Russia, although we still have the past data so it will never be as bad as it was.”

The threat to turn off the receivers “is a purely political decision,” Kuimov says. “No one needs it except politicians. In fact, it just demonstrates Russia’s disloyal attitude [toward] the U.S., in response to the disloyal attitude of the U.S. [toward] Russia.”

The threat also appears to have sown discord within the Russian government. On 13 May, the day after the threat surfaced, Denis Manturov, Russia’s minister of industry and trade, suggested that it didn't make sense. “Technically, it can be done,” he said. “But what is the purpose of that?”