The electromagnetic environment is as sensitive to pollution as any other environment, such as air or water. Depending on the situation, electromagnetic pollution may be called interference, jamming, or noise. In some cases, the cause of this pollution can be mitigated, but not always. This is an issue of increasing concern, as it can cause considerable harmful effects to commercial, academic, and defense operations, all of which are increasingly active in, and dependent on, the electromagnetic environment.
If one spectrum-dependent system is causing interference to another spectrum-dependent system, the ”victim” may report the interference to the spectrum authority for resolution. Within the United States, this authority is typically the Federal Communications Commission or the National Telecommunications and Information Administration. In those situations where the offending system is operating beyond authorized parameters, the regulator may take punitive steps against the offender to protect the victim.
However, even a transmitter operating within authorized parameters, and not in battlefield mode, might interfere with a very sensitive radio receiver. No matter what the cause of interference, including simply the aggregate of countless transmitters in the environment, all contribute to raising the noise floor and are a form of electromagnetic environmental pollution.
Passive systems, which are typically “receive only,” are exceptionally vulnerable and sensitive to electromagnetic pollution. They are usually looking for a specific radio signal emitted from a natural, rather than manmade, radio source. There are many things in nature that radiate unique radio signals, including hydrogen atoms, water molecules, and even lightning. Sensitive passive systems on satellites look down at the Earth to gather signals that help predict the weather. Radio telescopes look up from the ground at distant objects billions of light-years from Earth to gather signals that provide new information about space. It is easy to see how these passive systems play an important role in science and technology.
Passive systems may also play an unintended role of monitoring the general health of the electromagnetic environment. As the noise floor is raised by increased use of radio frequency devices, passive systems are among the first, and greatest, impacted. In fact, one could consider passive systems as a proverbial ”canary in the coal mine" – monitoring and serving as a warning if unacceptable electromagnetic pollution is occurring.
During the early days of coal mining, canaries were used to detect poisonous gasses building up in the mine. Much more sensitive than human miners, canaries would show signs of poison gas sooner, serving as a warning that the air was not healthy. The term has become synonymous to an early indicator of an environment negatively impacted.
With the exponential growth of spectrum use comes an increasing risk of polluting the electromagnetic environment. Active systems may not be well equipped to provide an early warning. Passive systems may need to be the canary in the coal mine. Their heightened sensitivity to negative impacts from other spectrum-dependent systems could be the first step to minimizing such impacts by enabling the identification and mitigation of offending systems, providing an effective approach to “policing” the environment. An additional way to protect the environment could be to establish criteria that a spectrum-dependent system must be capable of performing its intended function while minimizing its impact to the electromagnetic environment in order to be authorized for use.
Much like water and air pollution, electromagnetic pollution is a manmade phenomenon. And, as with other environments, it will take a global effort to minimize pollution in the electromagnetic environment.
Why is this important? Because our modern civilization is dependent on assured access to the electromagnetic spectrum. Protecting the electromagnetic environment and our capabilities within that environment are a necessity.
The Department of the Navy is continually evaluating electromagnetic environmental effects on spectrum-dependent systems as well as seeking ways to reduce its radio frequency footprint to reduce potential “pollution.” Secretary of the Navy Instruction 2400.2A, which provides guidance to protect the electromagnetic environment and the systems operating in it, is just one example of the DON’s commitment to being a good steward of the electromagnetic environment while advancing the operational capabilities of our spectrum-dependent systems.
Tom Kidd is the director for DON Strategic Spectrum Policy in the Office of the Department of the Navy Chief Information Officer.