Radio Detection of Meteors
The screens above are displaying the detection of meteors as they enter the Earth’s
atmosphere, primarily over the southern UK and northern France.
Using modest equipment we can detect the meteors that are travelling
at very high speed when they hit our atmosphere and a large amount of energy is
released which leaves a trail of ionised gas in the atmosphere that can be short
or long depending on a number of factors.
There is a
powerful radio transmitter located near Dijon in France that sends out radio
waves to detect satellites and space junk. Ordinarily this signal travels from
the transmitter out into space and the detection system at the Norman Lockyer
Observatory would not be able to pick up this signal. However, when a meteoroid enters the atmosphere
the ionised gas trail can
reflect radio waves.
These reflected signals are seen on our detection screens. They are seen as sudden peaks on the 3D screen and the
colour lightens the stronger the reflected signal becomes, known as “pings”.
The size and speed of these detections help us to determine
relative speeds and sizes of meteors. If the ionised
stream remains for any length of time, then the detection will be seen to
continue for a longer time. This is what is called an “over-dense”
meteor, because the ionised trail is still reflecting the signal after the meteor
has already burned out (ablated).