By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by allandale

Meteor detecting

All Topics | Latest Posts

Search for:  in Thread Title in  
SillyOldDuffer18/06/2018 17:31:13
2927 forum posts
593 photos

Posted by Jon on 18/06/2018 16:54:55:.

...

Used to like making HF beams.

Having a gigantic birdcage on your roof should be a status symbol. Ideally it should glow in the dark. My neighbours are so unimaginative. They even think owning a lathe is eccentric. Ho hum.

Andrew Tinsley18/06/2018 18:11:09
737 forum posts

Hello Muzzer,

Point taken, I must be more careful about my prefixes!

Andrew.

Neil Wyatt18/06/2018 19:44:58
avatar
Moderator
13584 forum posts
577 photos
68 articles

Hmm... that mast is only 4m high, not 32 feet. It's stood upright for about 15 years with a weather station on top with similar windage...

Jon Lawes18/06/2018 20:08:06
avatar
99 forum posts
Posted by SillyOldDuffer on 18/06/2018 17:31:13:

Posted by Jon on 18/06/2018 16:54:55:.

...

Used to like making HF beams.

Having a gigantic birdcage on your roof should be a status symbol. Ideally it should glow in the dark. My neighbours are so unimaginative. They even think owning a lathe is eccentric. Ho hum.

If your lathe is eccentric may I suggest balancing the chunk or wedging the baseplate?

daveb18/06/2018 21:54:36
567 forum posts
10 photos
Posted by Rik Shaw on 18/06/2018 07:50:57:

Thirty something years ago we were camping on a site by Chesil beach. It was a clear but moonless night around two in the morn and black as your hat when I unzipped the tent flap to visit the site toilet. What I saw near took my breath away. I have never seen so many stars in the sky before or since. I saw two shooting stars before I had even reached the lav - an unforgettable memory! (the stars - not the lav) cheeky

Rik

Light pollution makes it difficult to see the night sky, mountains are probably the best place to view, if you haven't seen it before you will be amazed at the number of stars in the sky.

Dave

Rik Shaw18/06/2018 22:25:51
avatar
1133 forum posts
318 photos

Good point Dave and as you observe, light pollution is a problem, but back then and in such an isolated location with zero local lighting the sparkling magnificence was still pretty impressive with a milky way to die for!

Rik

Doubletop19/06/2018 06:39:50
avatar
359 forum posts
4 photos
Posted by Neil Wyatt on 17/06/2018 20:53:02:
Posted by Rik Shaw on 17/06/2018 20:44:51:

With that Sky dish pointing earthward you are unlikely to receive anything other than Mrs Dales Diary or Gardeners Question Time laugh

Rik

Sadly the Sky dish is accurately aligned...

For OPTUS D1 and Home and Away and Neighbours?

Journeyman19/06/2018 10:28:31
avatar
498 forum posts
68 photos

I have to ask: Why do you want or indeed need to detect meteors? It sounds about as useful as George Merryweather's Tempest Prognosticator. If the meteor is big enough you will definitely know if it has become a nearby meteorite devil

John

Jon Gibbs19/06/2018 10:45:05
738 forum posts

It sounds a fun thing to try.

I did some research into meteor burst communications a while back - trying to maximize the data throughput - because as the ionization trail dies away the reflectivity, and hence the link capacity, diminishes.

The problem with meteors as a means of communication is that they are not regular throughout the day. The earth mops up lots more meteors at 6am local time than it does at 6pm where only those travelling faster than the earth can graze the ionosphere.

Jon

Geoff Theasby19/06/2018 10:56:37
542 forum posts
14 photos

Bernard Lovell, using ex-radar equipment, at Jodrell Bank in 1946, was the first to discover and detect meteors during the day.

Geoff

Neil Wyatt19/06/2018 17:34:06
avatar
Moderator
13584 forum posts
577 photos
68 articles
Posted by Journeyman on 19/06/2018 10:28:31:

I have to ask: Why do you want or indeed need to detect meteors? It sounds about as useful as George Merryweather's Tempest Prognosticator. If the meteor is big enough you will definitely know if it has become a nearby meteorite devil

John

Why sit in a workshop making useless objects when you could be out in the fresh air?

devil

Edited By Neil Wyatt on 19/06/2018 17:34:20

Neil Wyatt19/06/2018 17:38:41
avatar
Moderator
13584 forum posts
577 photos
68 articles
Posted by Jon Gibbs on 19/06/2018 10:45:05:

It sounds a fun thing to try.

I did some research into meteor burst communications a while back - trying to maximize the data throughput - because as the ionization trail dies away the reflectivity, and hence the link capacity, diminishes.

The problem with meteors as a means of communication is that they are not regular throughout the day. The earth mops up lots more meteors at 6am local time than it does at 6pm where only those travelling faster than the earth can graze the ionosphere.

Jon

Funnily enough although that's generally true, at the moment the current shower is the 'Daylight Arietids' which comes roughly from the direction of the sun and over the last half hour I was picking up one every minute or two.

Neil Wyatt19/06/2018 23:08:57
avatar
Moderator
13584 forum posts
577 photos
68 articles

How about this for a biggy?

The long line is the meteor slowing down, the big 'flash' is the ionisation cloud. Probably...

Doubletop20/06/2018 04:24:54
avatar
359 forum posts
4 photos

Neil

Can you describe what we are looking at here please?

I've been wondering what it is you are receiving. From what I’ve read here I guess it is the signal from the source being reflected of the ionisation trail. But what are you capturing? The reflected broadcast FM signal, the doppler shifted CW component or both?

As your last note suggests ‘slowing down’ so I guess you are getting the doppler shift in the X axis but is Y amplitude and the ‘big flash’ being the stronger reflected signal from the ionisation cloud? As I also guess the display is aggregated over time how is that represented?

If you are getting the doppler shifted signal can you determine the velocity of the vector in the axis towards the receiver?

Pete

Geoff Theasby20/06/2018 05:06:08
542 forum posts
14 photos

I was going to let Neil explain, but I had this idea...

This is a HDSR display, generated in the computer. It is listening to Graves radar, on 143.0488 MHz, which it can not hear, but when a meteor passes, the Graves signal is reflected, leaving a trail on the 'Waterfall' display.

Imagine a loom weaving cloth, which slowly lengthens, as the shuttle passes back & forth through the 'shed' formed by the raising and lowering of the alternate threads. If something is trapped in there, a lump will form, and be incorporated into the cloth. This is like a waterfall display.

Geoff

Doubletop20/06/2018 05:34:12
avatar
359 forum posts
4 photos

Geoff

Thanks; a bit early in the day?

I get the concept of a waterfall display. So Y is time, with current time at the bottom and and X is frequency rising from left to right.

Pete

(edited  I've just realised I can zoom the image)

 

Edited By Doubletop on 20/06/2018 05:37:02

Doubletop20/06/2018 06:10:41
avatar
359 forum posts
4 photos

The main signal has a doppler shift of 900Hz and (using an online calculator) a velocity of ~950m/sec or 2125mph (towards Neils house)

Pete

( could well be wrong....)

Geoff Theasby20/06/2018 08:55:24
542 forum posts
14 photos

Early? I'm often conscious, if not compos mentis, earlye in the morning.

Geoff

Neil Wyatt20/06/2018 09:34:20
avatar
Moderator
13584 forum posts
577 photos
68 articles

To try and answer multiple posts.

As Geoff says it's a 'waterfall' display but falling upwards, so the oldest data is at the top.

Frequency is the x-axis and brightness/colour shows signal strength.

The big blob is probably a stationary, or just moving with the atmosphere, cloud/trail of ionisation left behind by the meteor. I haven't fully calibrated the receiver, but it's about 200Hz out so that would move the column close to the radar frequency of 143.050 MHz showing little doppler shift*.

The streak is probably a return from the intense (moving) patch of ionisation at the location of the meteor itself.

It's a good detection as most tracks only show one or other of these features, and typically much smaller.

What confuses me is that if the blob represents a velocity near zero, the trace suggests the meteor moves towards and then away from the receiver.

But... the Arietid meteor radiant was just below the horizon a bit beyond north-west. This suggests it came in from the direction of the north Atlantic heading south east, and where the line crosses the blob would represent the point of its closest approach. When the ISS passes over you see exactly the same sort of frequency shift through zero, although it changes much more gradually.

The frequency drop is 1,450 Hz (distance between two ends of the trail).

This makes the line of sight velocity change about 3,143 metres per second (yes online calculator!)

3.1kms/sec seems fast, but the Arietids arrive with a velocity of about 39 km/s.

A bit of trig gives an angle of about five degrees, OK that's rough and ready and assumes we see the full trace but does suggest the meteor was observed nearly fromxwwuio the side, providing a sensible explanation for the doppler shift going through zero.

Neil

*the Graves frequency is 143,050,000. Tuning to 143,048,800 and listening to the upper sideband means that an unshifted signal will be at 143,050,00-143,048,800 = 1,200Hz.

The fact I'm getting it at about 930Hz suggests the tuning calibration is 270Hz out, but measurements of terrestrial staions suggests.

Doubletop20/06/2018 10:23:53
avatar
359 forum posts
4 photos

Neil

Thanks; I'm getting to understand this so some degree, helped when I found I could zoom the image and read the detail.

Surely you can't use the total frequency shift as the indication of velocity as it represents closing and receding velocities? You can only use the deviation from the fundamental +ve and -ve

Alternatively could it be the case that the range of the crossing is so great that the closing velocity is relatively minimal and the bright cluster, on the fundamental, is really the main signal with minimal doppler shift. As your array has a wide beamwidth the cluster exits for all the time it is within your beamwidth. Indicated by the height of the cluster (Y). Then the frequency shifts being some sort of spectral noise or harmonics that exist for the duration of the event being at the same time as main cluster? Basically, for any point in time during the event there is a large return on the fundamental plus a secondary signal that sweeps +ve to -ve as the event progresses. It would be good to see a plot with an expanded (Y) axis.

In the case of the ISS, as it is so close, there would be doppler shift so it would also be interesting to see a plot of the ISS to see what the ISS spectrum looks like for comparison.

Pete

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Email News - Join our newsletter

Love Model Engineering? Sign up to our emails for the latest news and special offers!

Support Our Partners
Eccentric July 5 2018
Eccentric Engineering
Expo Tools July 14
Ausee.com.au
Allendale Electronics
Sarik
SPG Tools October Seventeen
ChesterUK
Shapiro
TRANSWAVE Converters
Warco
emcomachinetools
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

Visit the Model Engineer
Exhibition website

Model Engineer Exhibition