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As of the first of May 2024 - the LVST is back on line.
What are meteors and how can we use radar to detect them?
'Meteors', commonly known as 'shooting stars' are the bright trails of 'Meteoroids' small pieces of space debris from asteroids or comets.
Meteor trails are formed when tiny particles, maybe the size of a grain of sand, impact the Earth’s upper atmosphere at an approximate height of 90 km and generate a strong shock wave in the air. A huge temperature differential is generated across the shock boundary and the radiant heat vaporises the surface of the particle. This causes the ablation of the particle and ionisation of the atoms of the material, producing radiation across a broad optical spectrum.
Very bright meteors are often called fireballs and are created by larger pieces of rock about the size of a small pebble. Sometimes, if a meteoroid has enough velocity (>11.2 km/sec), it can bounce of the atmosphere and escape the Earth's gravity to journey back out into space on an altered orbit. Very occasionally, a large rock lights up the sky and either hits the ground or disintegrates in the lower atmosphere as an air-burst. A meteorite with enough energy to create a crater is often referred to as a 'bolide'. Very tiny particles, often shed from comets, have a much slower and less dramatic descent through the Earth's atmosphere. These particles when found on the ground are known as micrometeorites.
The human eye and brain combination is extremely effective but it is unable to detect very small, fast moving and short duration meteors. It is also impossible for the human eye to see other than huge meteors during daylight hours. Radar, on the other hand, can detect the ionised trails of faint meteors lasting less than second and at all hours of the day and night.
Radar is effective because, in the meteor trail, ionised particles (electrons) are opaque to and reflect radar waves. When the radar pulses generated by the Graves transmitter intercept the ionised meteor trail they are reflected back towards the LVST receiver.
The higher the density of electron trail created the higher the intensity of the reflection.
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