Determining the radiant of meteors using Graves

[John101]

Pondering an interesting read

http://www.rtl-sdr.com/

Drop down the page to…

May 19, 2015

DETERMINING THE RADIANT OF METEORS USING THE GRAVES RADAR

Sure wish we had one of those arcingsparkers this side of the big pond!

And for whom SDR# toll (to include me) …

May 19, 2015

LIST OF ALL SDRSHARP PLUGINS FROM RTL-SDR.RU

John

N3AAZ

FM19xb

[The Admiral]

Thanks for the 'heads-up' on this one John. I had a look at the original article and I guess that there is some 'interesting' mathematics (or math as our American colleagues would say ) involved in this study, not to mention computing time. Very much an interesting experiment, though judging by their conclusions they didn't appear to be very successful in achieving their goal. I am personally uncertain as to exactly what we are seeing with the rapidly changing Doppler traces. I'd like to think that they are indeed meteor head reflections from a slowing meteor, but there can be other interpretations, such as the effect of resolving the forward velocity in the receiver direction, which changes with angle, or indeed, even whether amateur equipment is sensitive enough to detect true meteor head reflections (see the article by David Morgan "Speculation on Meteor Echoes", http://www.dmradas.co.uk/Downloads.html).

Having had a look through some material on the IMO site, I see that they also refer to determining the radiant, but the method appears to require as many as 6 receiver set-ups:

"Meteor path determination with a series of basic stations

Consider a set-up with only "basic stations." In this case, only the time of appearance of the meteor signal and its profile are measured at the different sites. For the path of the meteor to be determinable from these observations, at least six stations have to observe the meteor, since the position (three degrees of freedom) and the velocity vector (another three degrees of freedom) have to be found, and only the time of appearance is an accurate measurement.

The time observations of six stations result in a set of six non-linear equations with six variables. This set is very hard to solve analytically [24]. Furthermore, this method does not take into account the deceleration of the meteoroid body, which can be significant. Though theoretically the deceleration can be introduced by using the velocity information in the Fresnel oscillations, a set-up with only time-determining stations is probably not very feasible, and more than six stations per set-up would be needed in practice, as it is possible that a given meteor is not observable at all station sites."

So perhaps trying to achieve their goals with just 2 stations is a bit optimistic. But then again, they are using a different type of analysis.

Still, it's all good stuff. And yes, it is very convenient having the Graves transmitter on our doorstep (in the UK). Without it, I think we'd be quite limited.

Ian

[Ronnie67]

Well guys this is over my head, been reading some of your posts and though find it somewhat fascinating I have no idea what going on lol, I thought I would pop on over to this topic to see what discussions you are all having, so hope you do not mind, I cannot help in any of your queries, I give you all a thumbs up before I leave you all.

Ronnie   

[The Admiral]

Well, to be honest, I'm not sure I really understand what we are seeing in these meteor traces either

Ian

[Ronnie67]

lol, though I dont know what you are talking about above, I am interested in meteors so I am going to keep popping on over here and read your finds, what equipment are you using and are you scanning these meteors, plus is there a program I can access to maybe learn a little more

Ronnie

[The Admiral]

Ronnie, the concepts are really fairly easy to follow. You are probably aware that when a meteor careers into the upper atmosphere it ionises the air and so leaves a trail of ionised plasma behind it. This has the property of reflecting radio waves for a short period, and it is these reflections we are trying to detect. Specifically, we use the transmissions from a powerful transmitter near Dijon, France (the Graves transmitter). Tuning to its frequency one generally detects nothing as it is too far away, and in any case it beams towards the south, but whenever a meteor enters the atmosphere in the right place the plasma trail reflects these transmissions and we may be able to detect them. These appear as short pulses, fractions of a second long, or particularly during meteor showers, some reflections can last many seconds. These signals can appear quite varied, and trying to identify what they represent is the hard bit!

So in principle one needs a radio receiver capable of receiving signals in the region of 144MHz, and a suitable aerial pointing SE. If you don't have a radio receiver there are now available so called software defined radios (SDRs), or "dongles", which can be had at reasonable cost, which plug into the USB port on your computer, and you use free software to complete the radio. Most of us use these. To take it further, one can use a programmable frequency analyser application, again free to download, and do some fancy analysis.

Generally, there's not a lot of activity on this forum, but if you look at http://stargazerslounge.com/topic/220150-new-to-meteor-detecting/ there's a lengthy thread about getting set up for meteor detecting.

Also, on this site there are some useful and very readable downloadable articles if you want to look into it further.

Cheers - Ian