Although the Federal Communications Commission (FCC) announced its plans to sell 24GHz wireless spectrum for 5G networks well in advance of its March auction, two U.S. senators are accusing the agency of imperiling critical weather forecasting activities by offering frequencies too close to existing users. In a letter to FCC Chairman Ajit Pai, senators Ron Wyden and Maria Cantwell are now calling on the FCC to prevent carriers from using that millimeter wave spectrum until the issue has been resolved — a potential speedbump for winners of the 24GHz auctions.

According to the senators, the FCC moved forward with a 24.25-25.25GHz auction despite objections from National Aeronautics and Space Administration, the National Oceanic and Atmospheric Administration, and members of the American Meteorological Society, who pointed out that although existing weather forecasting activities take place on the adjacent 23.6-24GHz block of spectrum, the close proximity of new signals could create interference. Specifically, they suggest that the FCC’s 0.25GHz buffer between forecasters and cellular users won’t be adequate, since new cellular towers will be using higher-powered transmitters.

Meteorologists are concerned that they’ll be unable to collect data on water vapor, potentially impacting forecasts used for national defense, fishing, farming, and other public purposes. It’s unclear whether the agency could trim down some of the already auctioned spectrum, increasing the buffer, or move existing users further away from the 24.25GHz beginning of the 5G spectrum block.

In an apparent effort to slow the 24GHz deployment process down, the senators are asking the FCC for a variety of documents — materials to justify its sidestepping of meteorologists’ objections, as well as its plans to handle consequences in the event that either weather forecasting is impacted or an international body rejects the FCC’s conclusions on 24GHz wireless emissions. The materials are being requested by June 11.

The FCC opened its 24GHz auction in March and concluded the majority of bidding in mid-April, with an assignment phase commencing on May 3. Approximately $2 billion was raised in the auction across multiple carriers prior to the senators’ letter.