The National Research Council's Committee on the Scientific Use of the Radio Spectrum and the Committee on Radio Frequencies issued a report Spectrum Management for Science in the 21st Century that warns of interference to observations of phenomena on the Earth as well as in space. Most readers are familiar with the problem radio astronomers face receiving distant signals from galaxies far away. That's why channel 37 is not available for TV broadcasting and transmissions in areas around radio astronomy observatories are tightly controlled.
Another problem with RF pollution on the ground, or "electronic fog" as the report calls it, is not as well known. More than 20 satellites are currently in orbit using passive RF sensors to monitor very weak emissions that can be used for applications ranging from agriculture to weather forecasting. Potential sources of interference range from cell phones to aircraft radar to wireless computer networks.
"White spaces" where there are no transmissions are becoming harder to find. The report suggests development of technology to allow sharing by time as well as by frequency. Transmitters in a certain frequency range would be shut down briefly to allow scientific observations.
In the closing paragraphs of the summary, the NRC makes the case for reserving spectrum for passive purposes:
"In one sense spectrum for passive purposes including Earth remote sensing and radio astronomy can be likened to parkland preserved for public use. The true societal value of small parcels of land, especially in crowded urban areas, defies monetization and as such these parcels require proactive measures for their preservation and shared use."
The report went on to say that these "passive services" described provide several "critical" paybacks to society as a whole, with environmental predictions and "scientific Intellectual Value." It added that due to the valuable function performed by the small portion of spectrum under
"Although the impacts of the passive services are difficult to quantify," the document said. "[T]hey are valuable to society by providing vital information for climate and weather studies, and in allowing astronomical studies of the heavens. The quiet radio bands, like public parks, deserve protection."
The NRC report makes several recommendations to preserve quiet radio spectrum. The summary says the recommendations "provide a pathway for putting in place the regulatory mechanisms and associated supporting research activities necessary to accomplish this important task." It concludes, "[t]he committee believes that such a pathway will also lead to greater efficiency in active use of the spectrum, which should benefit all direct and indirect consumers of wireless telecommunications and data services."
Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.
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