[meteorite-list] 10.04.14 AZ Daytime Fireball: Direct compass measurements

From: Matson, Rob D. <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Sat, 11 Oct 2014 21:01:51 +0000
Message-ID: <4A4FA25E4DFE584AA580F4F069F9B4401CE436EF_at_EMP-EXMR104.corp.leidos.com>

Hi Steve/All,

First off, I want to thank you for having an all-sky camera that was operating
during the daytime and captured this event. As far as I know, it is the only
image/video record of the 4 October fireball itself, though of course there
are many images of the smoke trail clouds. Without the video record, it
would have been much more difficult to determine the bolide's true
flight direction, and of course the video also provides an accurate time
for the event. The timing is important, because without it one can only
estimate how much time has elapsed between the event and the images
of the smoke trails taken minutes later.

I've spent a little over 40 hours on this fireball, unfortunately much of it
wasted chasing coincidental radar returns that were aligned with the
fireball's NE azimuth from Flagstaff. Initially these radar returns looked
promising because they were at a reasonable range from Flagstaff for
a typical fireball terminal altitude (25-35 km), and they appeared in the
scans immediately following the event (which we knew thanks to Steve's
camera). As encouraging as the timing and location of the radar hits
were, there were reasons for concern. Hits at roughly the same location
but at lower altitude were present well before and after the meteor
occurred, which I initially ascribed to bad luck. But with the known
reduced sensitivity of NEXRAD over the last couple years, I should have
raised the red flag a bit higher than I did. Bottom line is that these radar
hits are spurious and unrelated to the fall.

The reason I know this is that I've got decent triangulation solutions for
the smoke trail images combined with Steve's video which put the
terminal altitude MUCH lower than is typical: certainly less than 20 km,
and possibly as low as 15 km! We also know the entry angle was very
steep, in a roughly NE to SW direction, based on parallax between
the various sites. For instance, Steve's camera saw the fireball start at
an elevation of about 25 degrees, azimuth ~50 degrees. The terminus
was at around an azimuth of 46.5-degrees (pending refinement of
my calibration solution for Steve's camera). Steve mentioned that with
a compass he measured a terminal azimuth of 43 degrees, but I'm
pretty confident it's a few degrees more than this. We'll eventually
track down the source of the discrepancy. (For instance, the magnetic
declination for Flagstaff is 10.76 degrees -- about a quarter degree
higher than the 10.5 he used, so that will increase his azimuth to
~43.3. But that still leaves a 3-degree discrepancy.)

Steve was also good enough to travel out to the Bellemont NWS
site that took an image of the smoke trails several minutes after
the fireball. He wrote:



________________________________________
From: Meteorite-list [meteorite-list-bounces at meteoritecentral.com] on behalf of Steve Schoner via Meteorite-list [meteorite-list at meteoritecentral.com]
Sent: Saturday, October 11, 2014 1:20 PM
To: meteorite-list at meteoritecentral.com
Subject: [meteorite-list] 10.04.14 AZ Daytime Fireball: Direct compass measurements

Hello, all,

Being that my all sky camera was damaged by lightning in July and replaced in August, and being that it did capture the image of this event near a prominent tree, I went up on the roof for direct measurements with two of my British WWII prismatic compasses.

Keep in mind my node6 camera is aligned to the North Celestial Pole (North Star). The north star is a Cepheid variable, and unless it brightens to mag 2 it is very difficult to see with the All Sky camera. It's position is 10.5 degrees to the wast of the magnetic pole.

Yesterday at Bellemont Weather Station right under and in line with the camera that took shots of the smoke clouds,I determined that they were at between 35 and 36 degrees magnetic readings. These reading are as close as I can determine as to the position of the clouds that day; 5 to 6 min later. But these smoke clouds might have drifted to the east in those five min and the degree readings would then be off maybe a degree or more depending on the wind speed 15 to 60 miles up.

Bellemont Weather Station:
Average 35.5 degrees NE add 10.5 degrees for Celestial Pole, making it 45.5 degrees NE from Celestial North.

With respect to my "node6" rooftop camera, I studied the image captured and though the fireball image is small it traveled down to the right side of a pine tree on the shaded side. So with my compass in hand and taking measurements of where I think it vanished above or behind the tree I came out with 32-33 degrees NE.

Flagstaff node6 All Sky Camera:
Average 32.5 degrees NE add 10.5 degrees for Celestial Pole, making it 43 degrees NE.


Estimated elevation above the horizon of burnout (terminal burst) from both locations determined with Bendix A-7 Bubble Sextant:

-13 degrees at Bellemont.

Estimated from the larger and higher elevation smoke cloud (terminal burst). The lower one measured at 7.25 degrees above horizon was the furthest away the fireball entry point. and at a much higher altitude in the smoke train.


~15 degrees at Flagstaff.

Such elevations above horizon considering the lowest burnout at 15 miles would place the fireball termination no closer than about 75 miles North East of Flagstaff and Bellemont. If it ended at 20 miles or higher, then even farther away.

That stated, it ended out in the middle of the Din`e(Navajo) and or Hopi Reservations.

Please be mindful that for all intents on reservation lands you are on Sovereign Nation grounds, almost like stepping into another county. If you do some searching out there get permission first.

Steve Schoner

BTW: Now I need to get back to work and make some petrographic slides.

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Received on Sat 11 Oct 2014 05:01:51 PM PDT