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

[Bill Cooke]

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





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