Radio meteor detection
Detecting meteors by catching radio signals that bounce off the trails of electrified air they leave behind.
As a meteoroid races through the upper atmosphere, it knocks electrons free from atoms, leaving a short-lived trail of ionised air. That trail can reflect radio waves. If a distant transmitter is beyond your horizon, you normally can't hear it; but when a meteor trail appears in the right place, the signal bounces down to your receiver for a fraction of a second or longer. This method is called forward scatter.
Radio detection works in daylight, cloud and moonlight, so it reveals showers that are impossible to see by eye, such as the daytime Arietids in June. Professional meteor radars measure speeds and directions of huge numbers of meteors, helping to map meteoroid streams.
Amateurs can join in with modest equipment: a suitable antenna, a radio receiver, often a software-defined radio plugged into a computer, and free logging software. In much of Europe many observers listen to the powerful French space-surveillance radar called GRAVES, on 143.05 megahertz. Each meteor appears as a brief 'ping' or a streak on a scrolling frequency display. Counts can be compared hour by hour and with visual results. Check your country's rules on antennas and radio use.
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