(meteorobs) 2012/02/01 TX Fireball - darkflight results

[Matson, Robert D.]

Hi Bill,

 

The computed results are lining up very well indeed with some of those

radar returns, particularly the clusters south of Lake Tawakoni, the
single

hit over Rains, the double hits north of Lake Fork Reservoir, and a pair
of

hits south of Lake Bob Sandlin. Now all we have to do is find a
meteorite

close to one or more of those radar returns and/or along the impact

trajectory to confirm the great collective analysis work!   --Rob

 

From: Bill Cooke [mailto:cookewj at comcast.net] 
Sent: Thursday, February 09, 2012 3:42 PM
To: Meteor science and meteor observing
Cc: Mike Hankey; ELPALLSKY; Marc D. Fries; Matson, Robert D.; James
Beauchamp; Kevin Palivec; Esko Lyytinen
Subject: (meteorobs) 2012/02/01 TX Fireball - darkflight results

 

This morning I reversed my earlier position and decided to ask my team
to perform the necessary calculations to compute an impact zone. This is
a 2 step process - first, each observed fragment of the meteor (only 1
piece in this case) has to have its trajectory extrapolated via a single
body ablation code from the last observed position to the point where it
is no longer ablating, i.e., when the speed drops below 4 km/s. This
position is then used as the start point for the darkflight
calculations, which take the meteor all the way to the ground.

 

3 sets of calculations were performed - two of the sets were done by my
team here at MSFC, with densities of 2.3 (carbonaceous chondrite) and
3.7 g/cc (ordinary chondrite). We did not take into account the winds,
as our code is a work in development (we can only handle winds in an
average sense). However, I also asked the Meteor Physics Group at the
University of Western Ontario to do a 3rd set of calculations; their
numbers do account for the wind data and assume a density of 3.7 g/cc.

 

The results are given in the purple, yellow, and orange columns of this
table:

 

http://www.billcooke.org/events/texas_darkflight_2012Feb02.pdf

 

They are plotted here:

 

http://www.billcooke.org/events/Darkflight_all.jpg

 

The masses are not your usual 1g, 10g, 100g, 1 kg sizes. I just took
whatever came out of the ablation code and ran them through the
darkflight. Normally we would iterate on the ablation until we got a
starting mass at the last observed position which would ablate down to
one of the standard sizes I just mentioned. However, I feel that these
adequately characterize the lengthy fall area, caused by the shallowness
of the meteor trajectory. As I expected, this is a lot of territory to
cover, and it is quite possible meteorite fragments could have landed in
the area lakes.

 

I believe that Mark Fries and Rob Matson have identified some doppler
signatures that may help the hunters out there. Hopefully something will
be found soon.

 

Regards,
Bill Cooke
NASA Meteoroid Environment Office
Marshall Space Flight Center
Email:william.j.cooke at nasa.gov

Office: 256 544-9136

 

 

 

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.meteorobs.org/pipermail/meteorobs/attachments/20120209/31f7c249/attachment.html