Radio quiet zone

A legally enforced area where transmitting is restricted so a telescope can hear.

Radio astronomy deals in signals so faint that a mobile phone on the Moon would be one of the brighter sources in the sky. Around the largest dishes, national regulators restrict transmitters — the zone around Green Bank covers 34,000 km² and extends to microwave ovens and petrol engines in the immediate area. The threat now comes from above: satellite constellations transmit continuously, from everywhere, and no terrestrial quiet zone can be drawn around the sky. Some of the mitigation is unexpectedly domestic. Green Bank's inner zone runs on diesel generators with spark suppression, the site uses no Wi-Fi, and staff drive vehicles chosen for having no electronic ignition. It is a working demonstration of the scale of the problem: the observatory is protecting itself from the twentieth century, not just from the twenty-first.