The US government has begun selling blocks of wireless radio frequencies that will be used for the next generation of a communications network known as 5G. But some of these frequencies lie close to what satellites use for key Earth observations – and meteorologists are concerned that 5G transmissions could affect their data collection.
Unless regulators or telecommunications companies take steps to reduce the risk of interference, Earth Observation Satellites flying over the US 5G wireless coverage areas will not be able to accurately detect concentrations of water vapor in the atmosphere. Meteorologists in the United States and other countries rely on that data to feed on their models; Without this information, weather forecasts around the world are likely to suffer.
"This is a global problem," said Jordan Gert, a meteorologist at the University of Wisconsin-Madison.
The National Oceanic and Atmospheric Administration of the United States (NOAA) and NASA are currently locked in high-level negotiations with the Federal Communications Commission (FCC), which oversees US wireless networks. NOAA and NASA have asked the FCC to work with them to protect the frequencies used to observe the Earth from interference, while 5G is redrawing. But the FCC auctioned the first part of the 5G spectrum with minimal protection. The sale ended on April 17 and raised about 2 billion US dollars.
Sharing the sky
Because the United States is such a large communications market, government-made decisions on how to deploy 5G are likely to affect global discussions on how to regulate technology. Regulators from around the world will gather from October 28th in Sharm el-Sheikh, Egypt, to reach international agreements for which frequency companies can use to transfer from 5G and what level of interference with the Earth observation frequencies is acceptable.
Astronomers, meteorologists and other scientists have long worked to share the spectrum with other users, sometimes changing to different frequencies to prevent conflicts. But, "This is the first time we've seen a threat to what we would call crown jewels on our frequencies – those we absolutely must defend are coming what can," says Steven English, a meteorologist at the European Center for Medium-Aged Weather Forecasts in Reading, UK.
They include a frequency of 23.8 gigahertz, on which water vapor emits a weak signal in the atmosphere. Satellites, such as the European MetOp probes, monitor the energy that radiates from Earth at this frequency to estimate humidity in the atmosphere below – measurements that can be taken during the day or night, even if the clouds are present. Meteorologists predict this data in models to predict how storms and other time systems will develop in the coming hours and days.
But the 5G station that is transmitting at almost the same frequency will produce a signal that will look much more like water vapor. "We would not know that this signal is not quite natural," says Gert. Predictions will become less accurate if meteorologists incorporate these bad data into their models.
The recent FCC auction included two sets of frequencies: one between 24.25 and 24.45 gigahertz, the other between 24.75 and 25.25 gigahertz. Wireless equipment emitting near the lower end of that range may obstruct the measurement of 23.8 gigahertz water vapor. The FCC did not respond Naturerequest for comment on this issue.
The situation is similar to having a noisy neighbor in the neighborhood, says Gert. If that person fires the music, a lot of noise is likely to bleed through the wall in your apartment. But if you can convince your face to turn your music around, you can sleep peacefully.
Engineers with radio frequency measure noise in units of decibel watt. Regulators set up controls that limit the permissible noise; multiple-negative numbers show more stringent controls. The FCC auction has set the US 5G noise limit to -20 decibels watt, which is much weaker than the thresholds viewed by virtually every other nation for their systems. For example, the European Commission has settled at -42 decibels per 5G base stations, and the World Meteorological Organization (WMO) recommends -55 decibels watt.
Many hope that WMO numbers will affect regulators to accept stringent noise standards at a meeting in Egypt. Because of the way of thinking, the US proposal will allow over 150 times more noise than the European proposal – and more than 3,000 times more than the WMO plan, says Eric Allaix, meteorologist at Meteo-France in Toulouse, who runs the WMO Steering Group for Coordination radiofrequencies.
There is relatively little research about just how bad weather forecasts could be obtained, as interference will increase to 23.8 gigahertz and other frequencies that are crucial for Earth observations, says Gert. "But the more we lose, the greater the impact," he says.
NOAA and NASA reportedly completed a study on the effects of different levels of noise mixing, but this has not been published, despite the fact that there has been at least one official request from the Congress. A 2010 report by the National Academy of Sciences, Engineering and Medicine concluded that losing scientific access to the 23.8 gigahertz signal would eliminate 30% of all useful microwave data that significantly contribute to global weather forecasts.
And the lack of atmospheric data from the United States could dramatically damage the forecasts for Europe, whose weather patterns are usually governed by US conditions 3-4 days earlier, says English.
The Commerce Department, overseeing NOAA, said it "strongly supports the administration's policy of promoting US leadership in 5G secure networks, while maintaining and improving critical government and scientific missions." NASA administrator Jim Bridgestone declined to comment, but much talked about his concerns about 5G at a meeting of the agency earlier this month. "This is a big deal," Bridgestine said.
The FCC plans to launch its next 5G auction, which will be the biggest ever in the country in December. It will include three more frequency bands – some of which are used for satellite observation of precipitation, sea ice and clouds.
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