Listening to meteors - how the technique works
Date: 19 November 2001
Depicts: Reflection of radio signals
Copyright: ESA 2001. Illustration by Medialab
During the daytime, high-frequency radio waves are reflected back to Earth by the ionosphere. A meteor entering the Earth's atmosphere is slowed down and deposits most of its ionised matter below the ionosphere, at an altitude of about 90 km, in the process creating a small ionised cloud which drifts slowly with the atmospheric winds until it disappears. Radio waves reflect off this moving cloud creating echos (known as type 2) which are detected by the receiver.
At night-time there are fewer and less dense ionospheric layers and the high-frequency radio waves can escape into space. These can intercept high speed meteors as they enter the upper atmosphere and produce short-lasting echoes (type 1), typically lasting 1 second, which have a large shift in frequency.
Last Update: 1 September 2019