Under construction.
Meteors are little rocks or dust, coming from a Comet. See the picture below a meteorite rock.
Comets are relatively small celestial bodies that revolve around a star in an often elongated elliptical orbit and consist of ice, gas and dust.
A very well known Comet is the Comet of Halley. See picture below.
In picture below, another comet, called NEOWISE, clearly seen in The Netherlands, juli 2020 .
Often the meteors travel in swoarms through our galaxy in an elliptical track. There are a lot of swoarms in our galaxy. All do have a name. For instance the Perseïden, Leoniden. The Perseïden meteors are entering our atmosphere in August of every year. The source of the Perseïden is the comet Swift Tuttle. When they enter our atmosphere with a speed of 60 till 120 km/sec, they are being burned. This gives a light signal Also an ionization spure around the burning . Sometimes the y are burned complete and sometimes incomplete. You see them often as a lightened stroke in the clear and dark sky. The burning can take a while in time, like a spur and or can explode, or a combination of both. Most of the meteors do not reach the surface. When they do, they are called a meteorite. Meteorites are sometimes be found on our planet..
See picture below the burning stroke of a meteor in visible light.
A wonderful sight.
But we can see them only with a clear and dark sky. When the sky is cloudy, it is not possible. And in our country, The Netherlands, it is often very cloudy.
But there is a way to see them with that cloudy sky. And that is possible by the aid of radio signals.
The way we do that, I like to explain in this post.
When a meteor, which penetrates our atmosfhere it will be burned, there will be formed a ionization around it. This ionization has the chracteristic to reflect radio signals.
And that is the characteristic we use to make a meteor visible by radio.
In picture below we see how things happen.
First we need a radiotransmitter to transmit a radiosignal (at the right). The trransmitter must be located beyond the horizon. This signal is reflected by the ionization spure of the meteor when is burning in our atmosphere. The reflection is received a the radio receiver beyond the horizon (at the left).
The audio of the receiver output is fed to the audio input of a computer. On this computer a software program is installed, suitable to convert the reflected audio signal and making it visible on a screen of the computer. On this screen we the meteor presence.
At home I use a simple SDR receiver, The transmitter is often a radio bacon, for instance in I use oftene the radar transmitter of Graves in northern France. This is a very powerful transmitter. The frequency is 143,050 Mhz.
But we use another characteristic for making it visible and used in the software, that is the Doppler frequency shift.
The ionization spur is moving. So the received frequency of the reflected signal is changing, because the meteor moves to us or moves away from us. When moving to us, the frequency is increasing. moving away it is decreasing. That is the Doppler frequency shift.
So we see in the screen of Spectrum Lab a horizon small stroke. To the left or to the right of the mainfrequency of the transmitter.
See in the pictures below the SpectrumLab picture of meteors. They a kind of complex reflections. The first 2 pictures we see a horizontal reflection of a starting ionized spur (see the time scale in the x-as) The horizontal axis is the frequency of the bacon signal. After that spur the meteor explodes and changes in different spurs apart from each other. Each spur has a different frequency, due to the Doppler frequency shift.
The 3th picture in the mid, a reflection just above us. No Doppler frequency shift occured. At the upper another reflection, a smal spur.
When the horizontal reflection spur meteor is just between the transmitter and receiver in distance, we hear a “ping”. On the screen we a kind of dot. When the meteor is closer to the transmitter, we see a short spur, we hear a “pieuw”. The closer the object is to the transmitter the longer the spur, the “pieuw”is. So at very close distance a very long spur occurs, so a “pieuwww”.
The software program, I use at home is SpecLab. The receiver is a SDR receiver, the SDRPlay RSP1 a. The antenna for receiving Graves is a discone antenna.
Ofcourse you can use other transmitters, like the bacons of Dourbes or Ieper. But you need then a better antenna with more gain. A three element yagi is suficient, with or without a preamplifier. Dourbes and Ieper are using low power.
Dourbes is situated in the midd of Belgium and Ieper in the west of it.
But we can see more reflections on the screen. Especially a lot when using Graves. We see then almost horizontal strokes over the whole frequency scale. These are reflections of airplanes. A lot, because Graves has a stronger signal strengh on my antenna.
Als nice to see.