[meteorite-list] Wisconsin Meteorite Data?

From: Rob Matson <mojave_meteorites_at_meteoritecentral.com>
Date: Sat, 22 May 2010 16:16:24 -0700
Message-ID: <GOEDJOCBMMEHLEFDHGMMCEIFEDAA.mojave_meteorites_at_cox.net>

[Forwarding to List from home e-mail account]

Hi Keith,

> So what information do we have in regards to the Meteor itself?
> Size estimate at entry?
> Altitude of initial explosion event?
> Estimated number of explosive events?
> Angle of entry? (I've heard 10 degrees?)
> Estimated entry speed?

I can answer some of these. I don't have a good estimate on the initial
size, but I think it's safe to say that it was greater than 1000 kg based
on the mass of recovered material, typical ablation % for a shallow entry,
and the low recovery fraction to date.

The earliest evidence of the bolide on Doppler radar was at an altitude
of 28.3 km +/- 0.9 km (altitude uncertainty based on 1-degree radar beam
width). Based on the videos I've seen of the bolide, there were at
least 7 fragmentation events.

The entry angle was 12.7 degrees based on the apparent slope of the
bolide as seen in the Milwaukee video (which was 11.2 degrees), coupled
with the known initial fragmentation location, and well-determined
flight bearing from NEXRAD Doppler.

The entry speed could be estimated fairly accurately using the Milwaukee
video, but it would require someone to go to the Milwaukee camera site
and measure angles to some landmarks visible in the video to establish
the pixel scale. I ~can~ say that based on the entry angle and the amount
of time that the bolide was visible, the initial entry velocity was
somewhere in the range of 22 to 36 km/sec.

So, if someone can go to the Milwaukee camera site and measure the true
angular separation of, say, a couple foreground buildings visible in
the video, then the entry velocity can be pinned down more accurately,
and the pre-encounter meteoroid orbit determined.

--Rob
Received on Sat 22 May 2010 07:16:24 PM PDT