[meteorite-list] 2nd recovered U.S. fall of 2016 - more details

From: Matson, Rob D. <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu, 25 Feb 2016 18:22:19 +0000
Message-ID: <4A4FA25E4DFE584AA580F4F069F9B440B52592A8_at_EMP-EXMR104.corp.leidos.com>

Hi All,

Some further information about the circumstances leading to the successful
meteorite recovery east of Lubbock, TX. First off, Mike Hankey deserves special
notice since often the first indication we have of a new potential fall is the
AMS website that he maintains. Marc Fries was the first to spot the nice
Lubbock radar returns for this fall -- less than 18 hours after the event! I
compiled those, and additional returns I found in the Amarillo radar, and
then went on a search for seismic signatures or videos that could be used
to pin down the time of the event. One Youtube video surfaced right away,
taken from a dashcam on highway 183 near Euless, Texas:

https://www.youtube.com/watch?v=qMkeVGSlV7o

Pat Branch did some quick work measuring terminus angles, concluding that
the vector lined up perfectly with the radar returns east of Lubbock. I soon
located two more videos, one from some still undetermined location near
Augusta, Kansas (east of Wichita) and some 580 km (!) from the fall:

https://www.youtube.com/watch?v=YPDoZYfH4ko

and another from a dashcam near Edmond, OK, north of Oklahoma City:

https://www.youtube.com/watch?v=qPb7jrtX4p0

Pat Branch was successful in contacting the driver of this car who provided
his exact location. There are numerous landmarks in this video that allowed
me to determine reasonably accurate starting and ending directions. Triangulating
this video with the one from Euless led to a fairly steep fireball entry angle and
a nearly due west trajectory.

However, upper atmospheric winds were relatively strong (over 100 mph to
the southeast,) and not surprisingly this is the trend we see in the radar returns.
All that remained was to get an accurate time for the event so that meteorite
masses could be estimated (based on the time delay between the fall and
when various radar volumes were scanned). Unfortunately, none of the
three videos above has a sufficiently accurate timetag.

But here again Pat came to the rescue. Rob Ferguson (the provider of the
Edmond, OK dashcam) emailed Pat telling him that the fireball was also
captured by the Oklahoma Dept. of Emergency Management's tower cam,
and that a friend of his (Putnam Reiter) works there and pulled the video for
him. This has a great, unobstructed view of the event, being up on a tower
some 200 feet! Most importantly, it has a very accurate timetag, being
regularly synced with a NTP server. So we now knew the beginning of the
event was at 3:44:08 UT (21:44:08 CST). I determined that the earliest radar
returns of the fall were from Amarillo NEXRAD at 3:45:49.7, just 99 seconds
after the beginning of dark flight (~21:44:11 UT). This was how we knew
meteorites were on the ground for sure, since dust or even small pebbles
can't fall that far in less than 2 minutes.

Anyway, this is getting a bit long and I want to get these details out
there sooner rather than later in order to credit some of the important
players that made this all happen. Hopefully it gives you a sense of the
amount of detective work goes into chasing down these falls, and how
much of a team effort it is.

Cheers!
Rob
Received on Thu 25 Feb 2016 01:22:19 PM PST