It's a capital improvement project the size of the entire planet, replacing one wireless architecture created this century with another one that aims to lower energy consumption and maintenance costs.

Two senators this week urged the Federal Communications Commission (FCC) to rein in the expansion of next-generation wireless into high-band spectrum, citing concerns from NASA and other scientific organizations. Specifically, scientists are concerned that 5G operations in the 24 GHz band could interfere with weather forecasting, the senators warned.

"Don't allow wireless companies to operate in a 24 GHz band until vital weather forecasting operations are protected, " Democratic Sens. Ron Wyden of Oregon and Maria Cantwell of Washington wrote in a letter to the FCC. "To continue down the path the FCC is currently on, to continue to ignore the serious alarms the scientific community is raising could lead to dangerous impacts to American national security, to American industries, and to the American people. "

In 2016, the FCC approved new rules opening up high-band frequencies, making the US the first country in the world to make frequencies above 24 GHz available for 5G. Then-FCC Commissioner Tom Wheeler called the move a "game-changer" for the US. The FCC began auctioning spectrum between 24.25 and 25.25 GHz (the 24 GHz band) this past March.

However, scientists from the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA) and elsewhere have warned that emissions from commercial broadband transmissions in the 24 GHz band could interfere with the collection of water vapor data.

The senators released an internal US Navy memo, issued in March, that explains the issue: Due to the physical properties of the atmosphere, scientists can only accurately measure water vapor in the 23.6-24 GHz band. This data is vital for meteorological and oceanographic models -- it's used to measure things like precipitation and wave height, and to determine the trajectory and intensity of tropical cyclones. However, NOAA and NASA expect interference from the adjacent 5G band that "will result in a partial-to-complete loss of remotely sensed water vapor measurements, " the memo says.

"Naval operations will continue but with a probable degradation of weather and ocean models, resulting in increased risk in Safety of Flight and Safety of Navigation, and degraded Battlespace Awareness for tactical operational advantage, " the memo concludes.

The Navy memo says the FCC could reduce out-of-band interference by tightening bleed-over limits to from -20 dB to -57 dB. In their letter, Wyden and Cantwell specifically asked the agency to refrain from awarding any final licenses to bidders in the 24 GHz spectrum auction until it approves those new limits.