[meteorite-list] DoD Satellites Detect March 2003 Bolide Over Park Forest

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:21:04 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4EB76_at_US-Torrance.mail.saic.com>

Hi All,

Regarding the discrepancy between the apparent bolide trajectory
(SE --> NW) as derived from the Park Forest strewnfield data, and
the NNE trajectory reported by DoD sensors, Steve Arnold wrote:

> Even with the possibility of a reverse strewnfield, that would
> need to place the fireball coming in from the NW going SE.
> Match that up with the eyewitness accounts that Steve Witt
> mentioned, and I would have to say that there is an error in
> the report. I know, it is totally impossible for some people
> to think that anyone who works for the government could ever
> be wrong about anything.

I think I can lay to rest any concerns that there was a mistake
in the DoD report -- the bolide did indeed travel from SSW to
NNE, and far from contradicting the eyewitness accounts, it is
in complete agreement with them. You see, with a trajectory
this steep coupled with the lack of range information (observers
on the ground can really only measure "apparent" bearing), it
is not possible to accurately determine the true bearing from
one observer's viewpoint. For observers south of Chicago, the
trajectory defined by the DoD report will indeed result in a
meteor that appears to be headed almost due northwest. To see
for yourselves, download the following .GIF file that I generated
with my SkyMap program:

<http://members.cox.net/mojave_meteorites/pftrack.gif>

SkyMap has a rocket trajectory mode that allows me to plug in
times, latitudes, longitudes and altitudes for a trajectory.
I took the DoD linear impact coordinates (41.56 N, 87.67 W)
and back propagated a 20-km/sec constant velocity path using
the 22.3-deg flight azimuth and 62.3-deg-from-horizontal
flight path angle in the report. (Don't pay too much attention
to the time-tags -- I decelerated the bolide somewhat below
10-km altitude so that I could get a few more points on the
track. This doesn't affect the track direction, just the
spacing of the times.) The bottom line is that despite the
22.5 deg (NNE) true heading, the bolide appears to be heading
toward azimuth 315, which is due northwest.

The observer coordinates I used were 41.5 N, 87.6 W, which is
in the rough vicinity of Chicago Heights. I can rerun the
program for other specific observer coordinates if anyone
is interested, since the apparent trajectory is very sensitive
to observer location.

Cheers,
Rob
Received on Sun 13 Jul 2003 05:26:52 PM PDT