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Angular Velocity calculation. Margin of error?

 
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Robert J Cobain



登録日: 2006.04.25
記事: 77

記事日時: Tue Sep 12, 2006 5:22 am    記事の件名: Angular Velocity calculation. Margin of error? 引用付きで返信

Hi SonotaCo,

Please can you tell me what is the margin of error when calculating the Angular Velocity? Thanks, Robert.
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登録日: 2004.08.07
記事: 9472
所在地: 139.66E 35.65N

記事日時: Tue Sep 12, 2006 4:37 pm    記事の件名: Re: Angular Velocity calculation. Margin of error? 引用付きで返信

Robert J Cobain wrote:
Please can you tell me what is the margin of error when calculating the Angular Velocity?

Well... very difficult question.
There are factors below which concern the accuracy of angle velocity measured by single site UFOAnalyzer.
-angle distance measurement error
---geometrical measurement error
---position to angle conversion error
-----FOV correction error
-time duration measurement error
-averaging improvement
-averaging error (angle velocity is not constant in its path)

Current UFOAnalyzer(V0) does not care about error, so please do not pursuit this in V0.
I will(want to) determine each factor by UFOAnalyzerV2 and make it clear.

All though, roughly saying...I think .....current angle velocity error is .....
When the meteor is middle speed, enough path length, small but bright, then the error might be a few percent.
But....
When the meteor is fast or big or faint, position measurement error become big.
When the meteor is slow, position error results big relative velocity error.
When the meteor is short, time duration error become big factor.
I think, on the worst case, currently, the error might be up to 50%.
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Robert J Cobain



登録日: 2006.04.25
記事: 77

記事日時: Tue Sep 12, 2006 8:00 pm    記事の件名: 引用付きで返信

Hi SonotaCo,

Thanks for the reply, I understand there are many variables but could I ask your opinion on the following meteor,

http://www.meteorlogni.com/Meteors/2006/9/7/M20060907_032748_Ivyhill_WS.avi

which was analyzed to have an AV of 32.6 deg/s .

This is the second fastest meteor I have recorded and I was wondering if it was a good canditate for being a hyperbolic meteor? The fastest Leonid I have captured was only 28.5 deg/s

I think the error should be fairly small in this case because it is quite long, and not too bright?

Cheers, Robert.
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登録日: 2004.08.07
記事: 9472
所在地: 139.66E 35.65N

記事日時: Tue Sep 12, 2006 8:33 pm    記事の件名: 引用付きで返信

Well...
Try check on "Analyze log" in EX page and analyze again.
Then you will get Mxxxxxxxx_xxxxxx.txt in the capture directory.
like below
----
[M20060813_005222_TK1_S2.avi - 1]
frames= 17, cnt= 402 bmax=255 amax= 1
fno= 28, cnt= 3 bmax= 83 amax= 0 bave= 74.67 x= 383.67 y= 237.15 dir=179.4378 alt= 30.5176 ra=164.0078 dec= 84.8422
fno= 29, cnt= 9 bmax= 91 amax= 0 bave= 76.11 x= 380.52 y= 235.72 dir=179.1025 alt= 30.3968 ra=167.0067 dec= 84.6894 av= 9.39
fno= 30, cnt= 14 bmax= 98 amax= 0 bave= 78.14 x= 377.51 y= 234.15 dir=178.7825 alt= 30.2617 ra=169.6761 dec= 84.5120 av= 9.21
fno= 31, cnt= 17 bmax=109 amax= 0 bave= 83.06 x= 374.26 y= 232.17 dir=178.4369 alt= 30.0893 ra=172.3182 dec= 84.2829 av= 10.34
......
fno= 44, cnt= 5 bmax= 73 amax= 0 bave= 66.80 x= 332.24 y= 206.03 dir=174.0840 alt= 27.7244 ra=192.6245 dec= 80.6125 av= 8.81
Angle velocity: Average= 10.23deg/s, Start= 9.58deg/s, Start altitude= 30.09deg
----
this is the measurement result of the meteor's position of each frame.
and the last field "av=xxxx" is the angular velocity of each frame.
plot those to graph. then you will see its main measurement error.

In general, angular velocity is not directly corresponds to the geocentric speed.
Angular velocity differs according to the cross angle between the sight direction and the direction of the radiation point.
For example, when a meteor appears at just radiation point, its observed angular velocity is zero.

I think it may be too early to say it was hyperbolic or not.
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登録日: 2004.08.07
記事: 9472
所在地: 139.66E 35.65N

記事日時: Tue Sep 12, 2006 8:52 pm    記事の件名: 引用付きで返信

another answer Wink

I roughly calculated.
maximum angular velocity for not hyperbolic meteor is almost 36deg/sec.
assuming Vg=72km/s, altitude=100km,distance=100km(elv=90deg(zenith)) and the radiation point is elv=0deg.

when observed at elv = 60deg, then the max will be 32deg/s
and elv = 45deg, 27deg/s

this is not accurate, just a hint.
---------------
your M20060907_032748_Ivyhill_WS is in fair condition for calculation(not too slow or big or....).
I think the error of angular velocity is less then 10%.

How much was the elevation of the meteor Question
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Robert J Cobain



登録日: 2006.04.25
記事: 77

記事日時: Tue Sep 12, 2006 10:01 pm    記事の件名: 引用付きで返信

Hi SonotaCo,

Thanks for the info, I will try and produce the graph you mentioned!

As regards the elevation, it is about 60 degrees, although I cannot tell exactly as I am in work and the database is at home! UFOAnalyzer did not report that it was a member of any known stream.

Armagh have also captured this meteor and I reported it to them as having a very large angular velocity. They are working on their own analysis software since they are an academic organisation and cannot rely on the UFOAnalyzer! Sad

Robert.
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登録日: 2004.08.07
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記事日時: Wed Sep 13, 2006 9:51 am    記事の件名: 引用付きで返信

Hi Robert
Robert J Cobain wrote:
Armagh have also captured this meteor and I reported it to them as having a very large angular velocity. They are working on their own analysis software ....


Great!! Please let us know the result when analysis ends.
I am interested in this very much.
I have not been paying much attention on whether a meteor is hyperbolic or not.
But, surely it is very interesting theme which we can find it.
I will add this to my memo.
SonotaCo
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Robert J Cobain



登録日: 2006.04.25
記事: 77

記事日時: Wed Sep 13, 2006 4:10 pm    記事の件名: 引用付きで返信

Hi SonotaCo,

These were the results, thanks for pointing out this feature of the UFOA I didn't realise existed!

[M20060907_032748_Ivyhill_WS.avi - 1]
frames= 15, cnt= 5604 bmax=255 amax= 37
fno= 44, cnt= 4 bmax= 41 amax= 0 bave= 36.25 x= 356.50 y= 309.00 dir= 59.6343 alt= 65.5483 ra= 5.1772 dec= 38.4310
fno= 45, cnt= 41 bmax= 68 amax= 0 bave= 43.68 x= 368.61 y= 305.17 dir= 61.4405 alt= 64.8078 ra= 3.8290 dec= 38.3507 av= 26.49
fno= 46, cnt= 123 bmax=121 amax= 0 bave= 53.15 x= 383.34 y= 300.61 dir= 63.5169 alt= 63.8859 ra= 2.1945 dec= 38.2403 av= 32.19
fno= 47, cnt= 222 bmax=165 amax= 0 bave= 56.54 x= 398.43 y= 296.10 dir= 65.5213 alt= 62.9229 ra= 0.5276 dec= 38.1163 av= 32.91
fno= 48, cnt= 312 bmax=211 amax= 0 bave= 59.96 x= 414.59 y= 291.23 dir= 67.5193 alt= 61.8619 ra=358.7515 dec= 37.9557 av= 35.20
fno= 49, cnt= 433 bmax=255 amax= 5 bave= 66.22 x= 431.52 y= 286.07 dir= 69.4598 alt= 60.7186 ra=356.9008 dec= 37.7542 av= 36.88
fno= 50, cnt= 632 bmax=255 amax= 33 bave= 68.97 x= 447.78 y= 280.53 dir= 71.1392 alt= 59.5641 ra=355.1323 dec= 37.4905 av= 35.63
fno= 51, cnt= 772 bmax=255 amax= 37 bave= 65.91 x= 463.65 y= 275.58 dir= 72.7073 alt= 58.4495 ra=353.4286 dec= 37.2443 av= 34.41
fno= 52, cnt= 812 bmax=255 amax= 38 bave= 61.52 x= 479.84 y= 270.84 dir= 74.2280 alt= 57.3174 ra=351.7128 dec= 36.9928 av= 34.78
fno= 53, cnt= 731 bmax=255 amax= 22 bave= 57.73 x= 496.61 y= 265.99 dir= 75.7057 alt= 56.1363 ra=349.9570 dec= 36.7130 av= 35.81
fno= 54, cnt= 607 bmax=255 amax= 4 bave= 54.24 x= 513.65 y= 261.17 dir= 77.1172 alt= 54.9334 ra=348.1985 dec= 36.4129 av= 36.10
fno= 55, cnt= 454 bmax=214 amax= 0 bave= 50.21 x= 530.85 y= 256.31 dir= 78.4499 alt= 53.7125 ra=346.4500 dec= 36.0869 av= 36.18
fno= 56, cnt= 303 bmax=139 amax= 0 bave= 38.68 x= 546.93 y= 251.65 dir= 79.6084 alt= 52.5628 ra=344.8427 dec= 35.7544 av= 33.58
fno= 57, cnt= 141 bmax= 52 amax= 0 bave= 18.74 x= 555.67 y= 249.03 dir= 80.2012 alt= 51.9328 ra=343.9807 dec= 35.5593 av= 18.18
fno= 58, cnt= 17 bmax= 18 amax= 0 bave= 15.94 x= 564.79 y= 246.09 dir= 80.7823 alt= 51.2637 ra=343.0893 dec= 35.3345 av= 19.01
Angle velocity: Average= 31.94deg/s, Start= 34.29deg/s, Start altitude= 62.92deg
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登録日: 2004.08.07
記事: 9472
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記事日時: Wed Sep 13, 2006 5:55 pm    記事の件名: 引用付きで返信

Hi Robert

From your data, I estimate the angular velocity was 35.4+/-0.2 km/sec at elevation 60.0deg.
If assume the altitude of the meteor at 60.0deg is 120km, then the geocentric velocity must be greater than 98km/s.
98km = 120km/sin(60deg)*tan(35.4deg)
If assume the altitude of the meteor at 60.0deg is 100km, then the geocentric velocity must be greater than 82km/s.

Now, I support that it was a hyperbolic meteor.

I will wait the result of simultaneous observation.
I am ready to say congratulations.



snap.gif
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last part deceleration may be the effect of explosion
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Robert J Cobain



登録日: 2006.04.25
記事: 77

記事日時: Wed Sep 13, 2006 9:08 pm    記事の件名: 引用付きで返信

Hi SonotaCo,

Thanks for producing the graphs and calculations! I agree that it is looking very likely that this is a meteor with a hyperbolic orbit. Very Happy Unfortunately Tolis Christou from Armagh Observatory is at a meteor workshop in the Netherlands and then at another conference in Berlin next week, so he does not have much time to investigate things at the moment.

Have you checked your own records which are much more extensive than mine for hyperbolic meteors? And if so, what proportion are hyperbolic? I am sure that I have other hyperbolic meteors in my archives too, but this particular one stood out as a good candidate for accurate analysis.

Cheers, Robert.
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Robert J Cobain



登録日: 2006.04.25
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記事日時: Wed Sep 13, 2006 9:44 pm    記事の件名: 引用付きで返信

Hi SonotaCo,

I don't think that we should be too confident that this is a hyperbolic meteor since if the meteor is only 80km up then the speed would not be enough for a hyperbolic orbit, but I suppose we need to wait and see what Tolis has. Robert.
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登録日: 2004.08.07
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記事日時: Wed Sep 13, 2006 10:01 pm    記事の件名: 引用付きで返信

Hi Robert
I agree.
But I still support hyperbolic because high speed meteor lights at high altitude.
The graph below shows the relation between start altitude and its velocity (observed by MSS-WG).



hv.gif
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登録日: 2004.08.07
記事: 9472
所在地: 139.66E 35.65N

記事日時: Sun Sep 17, 2006 9:26 am    記事の件名: 引用付きで返信

Hi Robert

I have searched our network data in Japan.
There are over 12000 simultaneous observation(2004 to now).
There are more than 40 observations that is calculated as having over 90km/s.
But many of them are very short, and others have not enough cross angle.
Finally, all of them was thought as insufficient accuracy.

I did not search angular velocity itself, but this may be more correct.

Huum... It seems it is very difficult to find accurate hyperbolic meteor.
In other words, it will be very precious if hyperbolic meteor is accurately observed.

Robert J Cobain wrote:
I don't think that we should be too confident that this is a hyperbolic meteor since if the meteor is only 80km up then the speed would not be enough for a hyperbolic orbit, but I suppose we need to wait and see what Tolis has. Robert.
Surely it is.
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Robert J Cobain



登録日: 2006.04.25
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記事日時: Sun Sep 17, 2006 7:24 pm    記事の件名: 引用付きで返信

Hi Tolis,

This is a very interesting result, thanks for taking the time to have a look at your records.

As you know there is much argument about the existence of hyperbolic meteors and some research has suggested that there are quite a lot of them. I think that it we can say that hyperbolic meteors are very very rare, this is a good result in itself and as you say, finding such a meteor would be a very precious thing. Robert.
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Robert J Cobain



登録日: 2006.04.25
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記事日時: Tue Sep 19, 2006 4:08 am    記事の件名: 引用付きで返信

Quote:
Hi Tolis,


Oops, Embarassed
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