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Today's screenshots are from Martin near Salisbury. The left hand screenshot is from Martin's own receiver system while the others are from the live stream. They show a tail echo lasting ten seconds or more with the spread of Doppler shifts indicating wind shear in the region where the additional ionisation occurred.? The observation from Armagh has a different perspective and hence shape on the display while the one from the Norman Lockyer observatory has only a slightly different perspective to that from the NW Hampshire receivers and they show little difference between Horizontal and Vertical polarisation. You can make your own screenshots of meteor echoes if you go to ?? Brian

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Here are several interesting echoes. Starting with the echo bottom left. This was seen by NW Hampshire with horizontal polarisation and by Armagh but not by NW Hampshire with vertical polarisation or by Norman Lockyer.

The echo upper right seen by NW Hampshire with vertical polarisation and only faintly by Armagh was unseen by Norman Lockyer and NW Hampshire with horizontal polarisation. The distinct straight line start of this echo and it's slight slope from lower left to upper right suggest that the meteor passed through an area with wind shear as the negative Doppler shift at the start suggests and extending reflection path while the positive Doppler shift suggests a reducing reflection path. This cannot be explained by the motion of a meteor. Or can it ?? In the future we hope to be able to answer this question using the raw data from the receivers that has much higher resolution in time that it is not practical to show on the live displays. Brian

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Although fairly quiet an average of two or more echoes per minute have been seen most mornings lately. In today's screenshot the NW Hampshire H Pol receiver sees two echoes only one of which is seen by the co-located V Pol receiver. The very feint echo observed by the Norman Lockyer receiver is most likely the same one seen on both the NW Hampshire receivers while Armagh saw neither. The upper echo seen by the Norman Lockyer receiver appears to have been unseen by any of the other receivers. So once again the observations show that the echoes are directional and linearly polarised despite the incident illumination being Right Hand Circular Polarised. Improvements we are working on will enable accurate correlation of echoes received at the different locations but this will be achieved by post processing as it isn't practical to do so on the live displays. There is guidance on using the system at and more notes are available at ? Brian

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Here are two meteor echoes seen by NW Hampshire along with the full bandwidth horizontal lines which are lightning strikes from a local Thunderstorm unseen by the other receivers.

Note that the lightning interference is stronger on the? vertically polarised system.

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An early start enabled me to capture some interesting echoes this morning while working on other things. You can capture your own observations at

This interesting echo is more or less omni directional and un-polarised. Note the differences in Doppler shifts with Norman Lockyer centred with positive Doppler, NW Hampshire centred with Zero Doppler and Armagh with only slight positive Doppler.??

The spread of Doppler is most likely due to wind shear in the region through which the meteor passed.

This echo is clearly directional and polarised as it was not seen by Armagh or by NW Hampshire with vertical polarisation.? It is possible that the direction in which the receive antennas point accounts for why some receivers see an echo and others don't but this is unlikely as all the antennas cover most of the region illuminated by the beacon and the cut off is gradual.

Brian

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Today's screenshot shows what are most likely the same echo viewed from three different locations. The vertical scales are not precisely aligned due to processing delays, a problem which can be overcome when the raw receiver data with precision timing is available so that echoes viewed from different stations can be correlated precisely. This is not be possible on the live display.? The echo received at Norman Lockyer is feint and has a positive Doppler shift of more than 20Hz while the same echo viewed from Armagh and NW Hampshire has close to zero Doppler shift. The vertical polarised receiver is seeing a slightly stronger echo than the horizontally polarised receiver in this example.

Brian

Circular Polarisation is used to ensure that if the reflecting target has any polarising properties as a wire or cylinder with a diameter small compared to the illuminating wavelength would, that some energy is reflected. If linear polarisation were used and was cross polarised with the reflector little energy would be reflected.

BRAMS for example also use RHCP.?Do you know what polarisation Graves uses ??

If the reflecting object were? for example? a sphere, large in diameter compared to the illuminating wavelength, it would reflect the incident signal with RHCP as? LHCP.

It would be interesting to put this to the test using two co located receivers one with RHCP and one with LHCP.? Sadly with my other commitments I can't volunteer to do that but perhaps someone else would like to investigate ?

I? am not familiar with the acronym GPV ?

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Circular Polarisation is used to ensure that if the reflecting target has any polarising properties as a wire or cylinder with a diameter small compared to the illuminating wavelength would, that some energy is reflected. If linear polarisation were used and was cross polarised with the reflector little energy would be reflected.

BRAMS for example also use RHCP.?Do you know what polarisation Graves uses ??

If the reflecting object were? for example? a sphere, large in diameter compared to the illuminating wavelength, it would reflect the incident signal with RHCP as? LHCP.

It would be interesting to put this to the test using two co located receivers one with RHCP and one with LHCP.? Sadly with my other commitments I can't volunteer to do that but perhaps someone else would like to investigate ?

I? am not familiar with the acronym GPV ?

Brian

Why is th tx antenna CP?
Have you considered a GPV? ?It may help reducing direct wave if horizontal polarised Rex antennas are used.?

yes it's difficult thinking about what the polarisation is the meteoroid ?and then how this is seen at the receiver. ?One needs to consider azimuth and elevation angles

Are these the azimuthal pattern over ground?
Can you calculate what does the elevation pattern looks like.?

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Hello Mike

The X and Y plots look similar but I would not claim that we are able to make any precise measurements of polarisation, just a strong indication. Another problem is that it is very difficult to maintain good circularity far off the Bore Sight for the transmit antenna.

It would be good to have observations with both polarisations from two or more locations.

Brian

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Hello Mike

A good question !? The Moxon rectangle calculator has the facility to calculate the main lobes but I've forgotten how to work it ! I need to re visit it. see

Brian

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?This screenshot shows? the outputs from 4 of the receivers in our network as waterfall displays which can be viewed live at

This example shows an echo seen only by the Norman Lockyer receiver?? and another seen by the Armagh receiver and the NW Hampshire receiver with the Vertically polarised antenna but not by the receiver at the same location with a horizontally polarised antenna. Today's screenshot? illustrates? the? directional and polarised nature of meteor echoes despite being illuminated with circular polarisation.The Malvern receiver is OFF and the Much Wenlock receiver is a development system which currently sees few echoes.

The vertical, time scale of the waterfall is about 30 seconds. Much more detail will be available when we are able to stream the live feeds from the receivers.?

Brian

illustrates the

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Hello Roo

That sounds like a great idea. I've attached? the last four screenshots that I have grabbed. They are fairly representative, with some "typical" echoes, some aircraft and direct signals that need to be recognised and ignored and one of the strange echoes that need more explaining. ? Note that not all receivers see the same echos due to their directional nature and and the H and V systems give different results due to the linear polarisation of the echoes. ? We are working on some improvements to the live display at so there will be some changes in the pipeline. The main ones will be to increase in displayed bandwidth, currently +/-30Hz will increase to +/- 100Hz. Also, currently the dynamic range from dark to bright is about 10dB and linear. We may change that.

If those screen grabs are OK for your purposes you can garb you own from the live stream. Best time is in the first half of the day unless there's a shower.

I also attach a 5th screenshot of one of the more unusual echoes showing a tail with lots of wind shear ?

Ultimately we are working towards making the raw data available that will have greater bandwidth and precision timing with resolution to about 1mS so that results from different receivers can be correlated.

Good Luck

All the best

Brian