Radio Meteor Detector - Lyriad Meteor

[Al.Grant]

Here is a quick waterfall screen grab from my Radio Meteor Detector of a Lyriad meteor 09:25 (GMT) this morning.

These is an associated mp3 audio file of this meteor here:  http://www.ukstargazer.org/meteor/lyriads-meteor-2015-audio-and-image/  (can't see any way to post it here)

The detector is still getting a regular series of pings, the peak for me was about 6am this morning at 64 per hour.

Al

[Al.Grant]

Shortly after posting the detector picked up another bright/loud hit.

Image and audio file added here:   http://www.ukstargazer.org/meteor/lyriads-meteor-2015-audio-and-image/

[The Admiral]

Interesting capture Al. I got this at 10.33.20 GMT this morning, by far my biggest so far. I like using the 3-D display, but on this occasion it's gawn orf the top! However, I do have a .wav file for it so I'll re-visit it at the end of this week. It must be the same one as yours. It looks as though there were at least two more or less simultaneous impacts.

For one reason or another my capture rates are a lot less than most people get I think, but it seems only to have 'kicked off' after 1 o'clock this morning, peaking between 10.00am and 11.00am, and with a short lull around day-break. Is that what you found?

Ian

[The Admiral]

Hmm, looking at it a bit further I've a feeling that the .wav file isn't long enough to capture the beginning! Drat!!

Ian

[Al.Grant]

HI Ian,

My detection rates certainly has a few peaks & troughts as shown below - my busiest periods during this shower have been 6am-11am

I've still got a whole bunch of images and audio files to check through.  I was at work when I checked the ones I've posted and logged in via TeamViewer but it slowed up too much to check them all.

I've tried the Spec Lab 3D screen, but I keep going back to the waterfall trace.  I guess I like the S:N reading and the Duration on the screen and also I seem to be able to get a longer trace on the waterfall than I do on the 3D, useful for the longer hits  ......  but have to admit the 3D ones do look much cooler 

Al

[The Admiral]

I picked up another biggie this morning at 04.59.09 GMT. I think it was about 19 seconds long, and as I was still using the 3-D display I missed a lot of it. At some point I'll see how much can be retrieved using the audio recording. For what it's worth, here is the last part of the trace.

I agree, the 3-D display does look 'cool', but I'm also fascinated by the signal strength variation that you can see with it. But yes, there are downsides as you indicate, and the inability to view a very long trail in its entirety is certainly one!

The detection rate has also started to pick up again since the early hours, though I'll need to check whether that is genuine or due to significant change in my background noise levels. Anyone else find this? If so, it seems to suggests that the Lyrids  peaked a little later than expected?

Ian

[Al.Grant]

Hi Ian,

I got the same hit at the same time but I'm not sure it's a meteor as it just looks too regular.

I think you can see in the image that it seems to cycle approx every 5 secs.  I'll try look out the audio for that one later

I have seen this same cyclic pattern on a number of occasions.  A similar shot from last year can be found here  http://www.ukstargazer.org/meteor/non-meteors-noise/ (object 3) you'll see the approx 5 sec cycle in that one.  I have spoken to a couple of other people who see this same trace on a fairly regular basis.  One person suggested it could be a satellite or bit of space junk that is rotating.  Don't know if that's correct but it does sort of fit the bill and that's what the Graves radar is designed to track.

I'd be very interested in knowing for sure exactly what it is!

I've seen a steady increase in detections since midnight.

Quick Edit :::::::::::::::::::::::::::::::

I've checked another detector with a similar set up to my own (similar because I'm actually using a modified copy of his script).

He also saw the same hit and although his trace is set to a longer time period than mine the pattern is about the same (just a little more squashed in time)

http://www.lincolnastronomy.org/phil/

I often use this site as a double check as it's not too far from me.

Al

[The Admiral]

I must admit that from my own trace I would have classed it as meteoric in origin, it looks no different to others I've been getting. I agree that on your trace there is a very definite cyclic component, but I would have been inclined (i.e. guess ) to think that what is seen is the cyclic beam direction switching of the Graves radar. This effect has been reported somewhere; I'll try to find it again. I can't help thinking that anything orbiting in space, and detectable, would be moving so fast that there would be a significant Doppler shift, the same as one sees with the Graves reflections from the ISS.

Ian

[Al.Grant]

I must admit that from my own trace I would have classed it as meteoric in origin, it looks no different to others I've been getting. I agree that on your trace there is a very definite cyclic component, but I would have been inclined (i.e. guess ) to think that what is seen is the cyclic beam direction switching of the Graves radar. This effect has been reported somewhere; I'll try to find it again. I can't help thinking that anything orbiting in space, and detectable, would be moving so fast that there would be a significant Doppler shift, the same as one sees with the Graves reflections from the ISS.

Ian

Cheers Ian,

I had seen something about the beam pattern at Graves but couldn't tie it in with that cycle, I'll need to have another look.  

Strange that it doesn't happen on every long trace though.

Good point on the lack of Doppler effect ....  I'd just be happy to know what it is and if it does turn out to be meteors then I'm happy!

[The Admiral]

I found the reference, but it was in connection with moonbounce using the Graves transmitter. See http://dk5ec.de/graves.htm; it's on p5 of the downloadable pdf from that page.

I must admit the only figures I've seen about the Graves switching periods don't quite tie in with what we observe (see for example the "document about the Graves radar algorithm" on this site http://www.itr-datanet.com/~pe1itr/graves/), where a 3.7 second period is referred to. But these are all old references and I cannot find anything out about the current beam switching regime - it may have changed since. It has to be something like that, though, I'd have thought it's too regular to be a result of the trail itself. I can't explain why it doesn't always appear though. Perhaps it has something to do with the orientation of the trail in respect to the transmitter. Who knows?

Ian

[The Admiral]

Al, doing some measurements on your trace, it looks as though each strong band is ~1.56s long, repeated every 4.75s, Interestingly, 4.75 is (3 x 1.56)! And as far as can be seen, they seem to be pretty precise. So, if it's not aliens, I'd put my bets on the transmitter regime.

Ian

[The Admiral]

Steve Nickolls sent me a trace recently (I hope he doesn't mind me mentioning it!) which showed nice detail of this pulsing. It was about 12.09 on the 18th. We're not sure if it was a meteor or the Graves signal breaking through because of the climatic conditions. I didn't pick it up, but then my sensitivity is poor. Here is the trace and  you can see clearly defined regions of fairly constant signal strength. I've estimated the durations of each of these.

a=0.72s;

b=1s;

c=1.4s (hmm, not sure if this region can be split into two, and it's interesting it is ~ 2x the other durations);

d=0.77s

e=0.75s

The cycle repeat time is 4.78s (yup, I know they don't quite add up to this, but call it experimental error  )

Make of this what you will.

Ian

[Al.Grant]

Al, doing some measurements on your trace, it looks as though each strong band is ~1.56s long, repeated every 4.75s, Interestingly, 4.75 is (3 x 1.56)! And as far as can be seen, they seem to be pretty precise. So, if it's not aliens, I'd put my bets on the transmitter regime.

Ian

I'm sure it must be aliens    .....  But saying that would only result in a government cover up .... So I'll settle for the transmitter profile causing it.

Steve Nickolls sent me a trace recently (I hope he doesn't mind me mentioning it!) which showed nice detail of this pulsing. It was about 12.09 on the 18th. We're not sure if it was a meteor or the Graves signal breaking through because of the climatic conditions. I didn't pick it up, but then my sensitivity is poor. Here is the trace and  you can see clearly defined regions of fairly constant signal strength. I've estimated the durations of each of these.

Steves pulses-1.JPG

a=0.72s;

b=1s;

c=1.4s (hmm, not sure if this region can be split into two, and it's interesting it is ~ 2x the other durations);

d=0.77s

e=0.75s

The cycle repeat time is 4.78s (yup, I know they don't quite add up to this, but call it experimental error  )

Make of this what you will.

Ian

I've had a look back and it looks like I got the same hit as Steve, but it was only fairly weak . 

I've got the audio file for that big hit earlier and think I'll run it through a spectrum analyser just out of curiosity .....  assuming I find a few mins spare!

Al

[SteveNickolls]

Hi Al and Ian, sounds like you have both been having fun the last few days! I like the screenshots. I have just checked and have these which correspond well with yours.

Thanks too Ian for analysing the peculiar line signal, I have seen it a few times over the past week but it never lasts very long whereas when I used to see it last year it would last for hours at a time and get counted as hundreds of detections.

In a few days I will post a graph of the detections over the recent shower period.

Cheers,

Steve

[The Admiral]

Steve, I hadn't appreciated that in the past you had the trace for hours at a time. Must surely be particular propagation conditions prevailing at the time, allowing you to receive the Graves signal.

Cheers

Ian

[SteveNickolls]

Hi,

I have come across this site http://www.itr-datanet.com/~pe1itr/graves/ which notes the GRAVES radar pattern changed in 2012- (sic)" The radar pattern is recently (july 2012) changed. There seems to be a 1.6 second tx sequence. sometimes it looks like 0.8 seconds." This would tie in quite closely Ian with the observed 0.72-0.77 seconds :-)

Cheers,

Steve

[SteveNickolls]

Hi Ian, sorry I missed your last post (was helping putting the shopping away). Yes it was in September and October last year, looking back at my notes I made the comment of settled high pressure at the time.

Cheers,

Steve

[SteveNickolls]

The specific dates in September were 10th-11th September 2014, the times were firstly between 19h12m 55s - 22h 28m 50s UTC on the 10th then at 00h 50m.00s -04h 38m 30s UTC on the 11th. So this went on for several hours. In October I noticed a similar signal being detected and I took a screen shot around 16 hrs 15m UTC on the 26th (see attached file), At the time I couldn't reconcile the signal to the timings for GRAVES.

Cheers,

Steve

26th October 2014.docx

[The Admiral]

Thanks Steve, you know I had previously but briefly looked at that link, but didn't pick up on that specific comment!

Your file shows the cycling nicely, but the one on the 18th just gone shows better detail I think.

Cheers

Ian

[The Admiral]

While doing a bit of web research I had a look at David Morgan's site (http://www.dmradas.co.uk/Downloads.html). I'm sure it is well know to you guys, but there are some interesting articles on the latest downloads link. I'd previously read his "Detection of Meteors by Radar" notes, and I've just quickly skimmed through his notes "Speculation on Meteor Echoes 2012), and they are quite extensive, albeit a bit technical. All good stuff. I don't think there was anything on receiving the Graves signal through ionospheric propagation though. I need to sit down in a quiet corner and digest that one! He's also well qualified, having spent some time at Jodrell Bank.

Ian

[The Admiral]

Harking back to my Short Wave Listener (SWL) days, I've been Googling VHF propagation and found a number of sites where it is discussed. You might wish to have a look at http://www.dxfm.com/content/propagation.htm. It's an easy read description of the various forms of propagation by which DXers (DX - long distance) achieve their goals, and might give an insight into the occasional direct reception of the Graves signals. It would be easier to understand, perhaps, if the signals were actually beaming in our direction, but of course they are beamed to the South. So I guess some form of fairly stable scattering (i.e. other than from meteors) must take place in order for us to detect it.

Ian

[SteveNickolls]

Thanks for this Ian, more reading methinks :-)

Cheers,

Steve

[SteveNickolls]

Ian, I have just got to page 17 and read this, "In the case of amateur meteor radar observations with commercial grade receivers when using the Graves CW Radar, it is probable that the strongest returns will be obtained under specular reflection conditions where the RCS is large.  In such cases the resolved LOS Doppler shift is likely to be due to the decelerating - (possible stationary) -plasma plume and will be a small fraction of the ‘head plasma’ velocities of around 20km/s.  Any Doppler shift from the radial expansion of the plume is so small it can be ignored

It is unlikely that an amateur receiver will detect many highly Doppler shifted returns from head echoes for three reasons:

• Fewer meteors will appear head on than at all other angles
• The head echo RCS is small and the returned signal level will be low
• The bandwidth of commercial communications receivers using SSB demodulation is limited to a few kHz.  To detect the full Doppler shift from a 70km/s head plasma requires a bandwidth of 33kHz at 143MHz.  Thus any observed Doppler shifts would be limited to around 3kHz, equivalent to ~6km/s

These arguments suggest that amateurs are unlikely to see high Doppler shifts from meteors."

Does this explain the preponderance of deaccelerating trails we have observed?

Cheers,

Steve

[Cath]

I thought maybe you might be getting reflections from commercial aircraft. But the LOS for an aircraft at 33000 feet is limited to about 220 miles from a ground level point. We used too find ourselves using aircraft reflection for over the horizon comms on VHF quite often, and that's using far far lower transmit powers.

Could be possible to get reflections off high alititude balloons, their's a few about from time to time released from both pros and hams for various reasons that can drift 100's of miles.

Other than that, I guess without tropospheric propagation, you're stuck with reflections/refractions from orbiting junk and/or real meteors.

[SteveNickolls]

Thanks Cath for your comments, I had considered aircraft but not balloons. Over the past 11 days the number of such incidences with the signal have been few and short lived at that but last year I had reception over several hours over an evening and the following morning and had to explain it to myself as being an atmospheric effect.

Best regards,

Steve