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

From: Paul Harris <paul_at_meteoritecentral.com>
Date: Sun, 24 Jan 2010 11:58:33 -0800
Message-ID: <4B5CA669.9030604_at_meteorite.com>

Hi Mike,

Yes, Rob does amazing work and finds an incredible number of meteorites
too. So many in fact that I often wondered how he was able to transport
them all home at the end of a hunt. Then one day while Jim and I were
out hunting I discovered the answer...

http://www.meteorite.com/rob.jpg

Jim and I are looking forward to seeing everyone soon at Tucson!
http://www.meteorite-times.com/tucson/

Paul




Mike Hankey wrote:
> 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
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Received on Sun 24 Jan 2010 02:58:33 PM PST