(meteorobs) 2012/02/01 TX Fireball

[Bill Cooke]

We have spent the last few days analyzing the Sandia camera videos kindly provided by James Beauchamp and Kevin Palivec (also thanks to Esko Lyytinen for his insight and comments). These have enabled us to determine a decent trajectory for the meteor; unfortunately the meteor entered at a shallow angle and its path/duration was so long (18.5 seconds) that the linear approximation used in the trajectory codes (MILIG, courtesy of J. Borovicka, and SMETS) is not valid, resulting in a possible error of several (~5) kilometers in the final position. Consequently, we did not attempt the dark flight calculations needed to determine the impact zone, as an error of 5 kilometers in position at 30-40 km altitude would translate to over a hundred square kilometers of uncertainty in the meteorite fall area. I can say that a solution using the first hundred frames of video (meteor is above 65 km altitude) yields a trajectory consistent with the Edgewood doppler returns; all other solutions put the meteor path about 20 km to the north of the radar signature.

Here are the beginning and end coordinates of the meteor, based on a solution involving all 976 points (frames) from the 3 videos:

Meteor beginning point: 99.176 W, 32.108 N at an altitude of 92 km
Meteor end point: 96.357 W, 32.745 N at an altitude of 43 km

Mean residuals in trajectory fit (residuals show systematic trends due to breakdown of linear path approximation)

Coleman: -0.045 km vertical, 0.703 km horizontal
Hawley: -1.889 km vertical, -1.711 km horizontal
OKC: +1.302 km vertical, -0.123 km horizontal

Again, the end point is NOT the impact location; it represents the meteor position in the last frame in the OKC all sky camera video.

Average speed is 16.3 +/- 1.4 km/s
Initial meteor speed: ~18 +/- 1 km/s
End meteor speed: 9.8 +/- 4 km/s

I am confident this meteor produced meteorites. Seen by our camera way over in New Mexico, it was very bright, with peak absolute magnitude around -14 (lower limit). Mass estimates from the light curve range from about 20 kg to just over a metric ton (1017 kg), depending on whose equations/technique you use. I consider a few hundred kg likely, but would find it hard to argue against the metric ton figure. How much mass made it to the ground is anyone's guess, but be assured that this was a BIG rock that blazed across the Texas sky.

The gory details are in this pdf file: http://www.billcooke.org/events/20120202_0157.pdf
The complete meteor trajectory (text file) is here: http://www.billcooke.org/events/smets.txt

Reference for MILIG: Borovicka J.: The comparison of two methods of determining meteor trajectories
from photographs. Bull. Astron. Instit. Czechoslovakia, 41, 391-396 (1990)

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