[meteorite-list] Fwd: First cut at wind-shifted, predicted impact coordinates

From: Mike Hankey <mike.hankey_at_meteoritecentral.com>
Date: Sun, 24 Jan 2010 13:37:36 -0500
Message-ID: <f0a794131001241037r71f2b243vdee75f8997702eb7_at_mail.gmail.com>

Hi,

Meteor wizard Rob Matson has taken a first crack at estimating a
strewnfield for the Lorton Meteorite.

I have plotted the points in Google Earth. You can see some maps and
download the KMZ file here:

http://www.mikesastrophotos.com/astro-photos/lorton-meteorite-estimated-strewnfield-version-1/

Its looking like the Fort Belvoir Golf Course could be prime hunting grounds.

Rob is the only person I know of who is qualified to do this type of
work and willing to share it with the meteorite community. Rob's work
has been instrumental in numerous meteorite discoveries and we all owe
him a debt of gratitude.

Thanks Rob!

Mike




Hi Guys,

I've done some serious data-gathering and number-crunching
today to come up with a hunting corridor for you. Here are
my current best assumptions based on witness observations,
images of the dust cloud, the impact location, and upper
atmospheric radiosonde data for the balloon launched from
Sterling, VA, about an hour after the fall:

Entry angle: ~55-60 degrees from horizontal (i.e. steep)
Flight direction:? Azimuth +191 (11 degrees west of south)
Average wind velocity from 5-16 km altitude:? 70 knots
Average wind direction from 5-16 km altitude:? Az 90 (east)

Using an example break-up altitude of 25 km at an initial
velocity of 15 km/sec, the rotation of the strewn field
relative to flight direction ends up being 40-50 deg clockwise,
which is quite significant. Here are where masses of various
sizes end up, both in Lat/Long and distance/bearing from the
308 g find:

?Mass??? Longitude? Latitude? Dist (mi) Bearing
-------? ---------? --------? --------- -------
? 3 g??? -77.12929? 38.73888???? 5.2????? 59.3
? 5 g??? -77.14419? 38.73268???? 4.3????? 58.7
?15 g??? -77.16179? 38.72688???? 3.2????? 56.0
?40 g??? -77.18079? 38.71908???? 2.1????? 52.6
120 g??? -77.19569? 38.71088???? 1.1????? 50.6
(308 g)? -77.21159? 38.70068???? -0-????? N/A
1150 g?? -77.22609? 38.69048???? 1.1???? 228.0
3750 g?? -77.24249? 38.67848???? 2.3???? 227.4

The reason the masses aren't round numbers is that my program
includes ablation, so while the simulated stones started off
with nice round numbers like 100 g and 1 kg at altitude, the
ablated masses are a fraction of the original.

So where are these locations? The 120-gram mass ends up near
Rhondda Drive, a couple hundred meters NW of Richmond Highway
and Telegraph Rd. The 40-gram mass ends up on the north end
of Ft. Belvoir. The simulated 15-grammer ends up on the Ft.
Belvoir golf course. But 5-gram stones would be off the base
to its north, north of John J. Kingman Rd. And 3-gram stones
end up in the southwest corner of Huntley Meadows Park.

Going in the other direction (heavier masses), the ~1.1 kilo
simulated mass above ends up very close to I-95, a little
west of Morris Ginsberg & Co.? And the largest mass I ran
crosses over to the other side of I-95 on Landfill Drive. ;-)

If you connect all these dots, you should find quite a bit
of searchable real estate.? My advice is on a map to draw a
45 degree angle southwest of the doctor's office for heavier
stones, and a ~55-degree angle NE of the 308-g find for the
lighter stuff (that's 55-degrees clockwise from north).

I'll continue to search for better observations that can
yield a more accurate entry angle.? We really need a good
observer who had a side view of the event and can tell us
what the slope was like relative to the horizon.? --Rob
Received on Sun 24 Jan 2010 01:37:36 PM PST