(meteorobs) Meteor triangulation from sonics

[Matson, Robert D.]

Hi Jake,

Just to confirm, I assume you are using a temperature profile for the
atmosphere and not just a constant temperature when modeling the sound
time-of-flight. Also, in the case of large meteoroids that do not
have a prominent terminal burst, the sonic boom delay for each ground
site depends on that site's closest "distance" (see caveat below) to
the meteor *trajectory* (to first-order, a 3-D line), rather than to
a single point in space. So different sites will be experiencing
sonic booms from different points of the trajectory.

For a terminal burst, you need a minimum of only three ground sites
to do triangulate it (thus the term). Of course, more sites is better
so that you can do a least-squares fit.

For a traveling bow shock, you need a minimum of four ground sites
to determine the 3D line in space (and again more sites is better
to allow for a least squares fit).

Final caveat to confuse things further: the path taken by the earliest
sound wave to reach each observer is not really a straight line, and
in fact deviates significantly from a straight line for sites that
are distant from the supersonic trajectory. It takes some serious
number crunching to solve the high-fidelity meteor triangulation
problem since all the sound wave paths are curved. So, if one is
not up to the task of doing sonic "ray tracing", you should only
use the receiving sites that are closest to the trajectory.

Cheers,
Rob

-----Original Message-----
From: meteorobs-bounces at meteorobs.org
[mailto:meteorobs-bounces at meteorobs.org] On Behalf Of Jake S
Sent: Wednesday, February 08, 2012 7:34 PM
To: Meteor science and meteor observing
Subject: Re: (meteorobs) 2012/02/01 TX Fireball Trajectory Solutions v1

I've made some revisions as well. With the altitude data from Bill
Cooke. Given that it was so shallow and still at 60 km when it passed
by the seismograph greatly alters what I had expected. I would have
expected the sonic boom to not generate such a large pressure wave
until in the more dense lower air. But anyways this high altitude
brings the trajectory farther south. Based on my calculations from the
seismograph, the trajectory Bill Cooke has provided is only about 3km
off which is easily within the uncertainty in my calculations
(especially if the speed of sound is slightly off, colder than a
standard day?)

http://3dradar.wordpress.com/2012/02/09/dfw-tx-222012-0157-utc/
-jake
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