(meteorobs) meteoroid orbit vs parent body (comet)

[Hartwig Lüthen]

Hi
I recently played around with perseid orbits a bit. Petra and Joerg 
Strunk and myself had set up 2 cameras near the German town of Herford 
this year.  I wrote me a software to export Metrec meteor data to UFO 
orbit. We had a 13km baseline and a large number of meteors.

Since these were perseids, we knew what types of orbits to expect. In 
fact we got a number of orbits which were quite consistent with 
published values for node, arg of perihelon, inclination and q. 
Excentricty varied in these orbits quite a bit, but I think that's 
normal for stream meteors. On the other hand, we had a number of orbits 
that were far off. The geocentric parameters (altitude of first 
detection, final altitude) looked however quite reasonable throughout 
our data.

UFO orbits (and most other double station software) computes a radiant 
from the two trails and uses it and the velocity of the meteor for 
computing the heliocentric orbit. Errors can result from inaccuracy of 
the radiant position and from velocity errors.

The accuracy of the radiant depends on geometrical factors (how close 
did the meteor appear to the radiant, how long were the trails etc) and 
from astrometric accuracy. Generally it should improve if the baseline 
was longer than the very short 13km of our experiment.

The accuracy of velocity is of much more fundamental concern, especially 
for faint video meteors. In many of these the meteor was visible on 5 
frames only. It may have emerged at the very end of frame 1, and it may 
have ended at the very beginning of frame 5. On the other hand it could 
have emerged at the beginning of frame 1 and ended at the end of frame 
5. So we cannot decide if the duration was 5 frames or 3 frames.  This 
error translates directly into an uncertain velocity determination and 
will affect the resulting orbits drasticaly. I figured out that playing 
around with the velocity of meteors with unreasonable orbits within the 
margin of error could convert them into well-behaved perseid orbits in 
many cases.

Velocity error will be reduced if the meteor is recorded on more frames, 
e.g. on 10 or 15 frames. One also should switch off all Mintron/Watec 
frame integration modes whatsoever.

Cheers
Hartwig



chiayk schrieb:
> Hi folks:
> 
>          How accurate is the 2-station meteor orbit obtained from say 
> one single meteor from two adequately spaced stations  videoccd setup in 
> terms of the calculated meteoriod  6 parameters vs Parent Comet.  ie  
> Arg of Perihelion /Ascending note/ Inclination/Perihelion distance/ e/ 
> a. Do we expect close matching to the parent body (comet) ?
> Is there any example - tabulated numeric examples to show these.
>         Thanks
>  
> rgds
> ykchia
> 
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