Aircraft equipped with powerful radar units are forbidden from turning them on when on the ground near people. Explain why this is so.

Radar systems are crucial for the navigation and safety of aircraft, as they serve as eyes that can ‘see’ through darkness, clouds, and all weather conditions. These systems operate by emitting a pulse of high-frequency radio waves that bounce back upon hitting an object – be it another aircraft, terrain, or weather formations like a storm. This reflection, or echo, is then analyzed to determine the distance, size, and speed of the objects detected.

Radar’s ability to provide real-time spatial information makes it indispensable for avoiding mid-air collisions and safely steering through congested airspace. However, the power necessary to emit these radio waves is substantial, and this is where safety concerns come into play, especially when an aircraft is grounded and in close vicinity to people.

Electromagnetic radiation emitted by radar systems belongs to the radiofrequency (RF) range of the electromagnetic spectrum. While these waves are non-ionizing and do not have enough energy to remove tightly bound electrons from atoms, as the ionizing radiation does, they still pose potential health risks.

High intensity RF fields generated by powerful radar equipment can lead to tissue heating. This can result in burns or heat stress, which are immediate health effects. Other potential impacts might include cataracts in the eyes or sterility in males due to the sensitivity of the lens and testicular tissues to heat. There is also a potential link between long-term exposure to RF fields and increased risk of cancer, though this is subject to ongoing research. To manage these risks, strict regulations on exposure limits are imposed, which brings us to the necessity of radiation safety guidelines.

To safeguard the public and professionals from electromagnetic radiation exposure, international bodies such as the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and national agencies like the Federal Communications Commission (FCC) in the United States have established exposure limits. These guidelines are based on thorough scientific evaluation and are designed to prevent recognized adverse health effects.

The safety measures consider the frequency of the radiation, its intensity, and the duration of exposure. Guidelines also differentiate between occupational exposure for trained personnel and general public exposure, with more stringent limits applied to the latter. Adherence to these limits is particularly imperative in environments like airports, where individuals may inadvertently come close to radar emitting devices. This is why aircraft are not allowed to activate their radar systems when grounded. Doing so could exceed the safety thresholds for radiation exposure, especially for ground personnel and bystandiles who might unknowingly be within the radar's range.