[meteorite-list] RE: You are wrong Robert, that's a METEOR!

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:22 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4EDDA_at_US-Torrance.mail.saic.com>

Hello Bj=F8rn and List,

> I really don't know how you arrived at your numbers.
> And I'm really not (that) interested.
> BECAUSE, if you have garbage in -> garbage out, as we all know.

That's a shame that you're not interested because putting blinders
on doesn't make the math go away. I spent the time to write the
software to analyze this problem -- HAVE YOU?! I'm dealing with
hard numbers and you're still looking at pretty pictures.

> You don't know where the observers are...

Exactly? No. Believe me, that would be nice to know but no one
has yet published them, and so the best I can do is go with what's
on the maps for their town locations:

Porthcawl 51.4769 N, 3.7078 W
Pencoed 51.5092 N, 3.5144 W

I'll be happy to run more accurate coordinates if someone can supply
them, but the exact relative locations are not what's driving the
solution -- the tilts of the tracks are. More on this later.

> you don't know the field of the two different cameras,

I only need the field of view of one of them, and I sensibly chose
the Porthcawl camera since the horizon is in the FOV, and because
I at least know it's a cell phone camera image, which means it's
fairly wide field of view. I can estimate the location of the sun
(below the horizon) in the image with reasonable error bars due to
symmetric sky brightness to the left and right of the vertical line
intersecting the sun's location. The horizontal field of view is
greater than 60 degrees and probably closer to 90 degrees based
on optical specs I've seen for several cellular phone camera
lenses.

> you don't know the azimuth of the two sighting lines,

But I can certainly place bounds on them based on the time of
the Porthcawl image (and excursions from that time), and the
range of azimuth angles left of the sun that result from different
assumptions about the cell phone camera FOV and the sun's horizontal
position (below the horizon). If you extend the track to the
horizon, the azimuth at the horizon (call it HorAz) works out
to be between 255 and 266 degrees in the Porthcawl image -- and
believe me this range of uncertainty is generous.

Since Porthcawl is located at azimuth 255 as seen from Pencoed,
it follows from simple geometry that if you assume a HorAz of
anywhere from 255-266 for the Porthcawl image, the HorAz for
the Pencoed image cannot be greater than this. It can be
less, but not by more than 3 degrees.

> you don't know the altitude angle in the sky for the
> meteor head.

I could estimate it if I wanted, but there's no need because
it has absolutely no bearing on the problem. The problem can
be solved from the horizon azimuths and track tilts alone.

> You can't even be sure of the time.

It's at least as late at 7:13pm -- and I ran excursions out to
7:30pm because the time is important to the solution.

> And you rotate the image to get the steepness of the tail you
> wish...

Not the steepness *I* wish -- the steepness dictated by the clouds
in BOTH scenes. Here again I've been generous by running excursions
to steepnesses beyond what is reasonable. Why don't YOU tell me
what you think the track tilts are in the two images? The difference
in the tilts is THE most critical parameter to the solution.

> You make a LOT of *assumptions* of this values, and you have
> your BLACK BOX method which you never really explained.
> Do you think anyone can trust the results you might get??

That's up to them. My reputation in solving related problems
hundreds of times more difficult is already established. Do
a Google search on Iridium flares, SkyMap, Columbia debris
trajectory analysis, and the Park Forest bolide if you doubt
my mathematical abilities.

> Until we get more verified numbers, I can't compute anything here.

The difference between you and me is that I'm at least willing
to work with what I've got, and by varying parameters I have
determined which ones are important and which ones are secondary
to the problem.

> BTW, give me your guessing, HOW FAR AWAY ARE THOSE CLOUDS, Robert?!!
> (Those right in front of the meteor head.) GIVE ME YOUR GUESS.
> That answers the riddle I posed yesterday.............
> I know the answer, you see.

Well, if you really know the answer, then you must know their altitude.
And if you know the altitude and the distance, then you can determine
the field of view of the cell-phone camera image.

I don't happen to know the clouds' altitude or the Porthcawl camera
FOV, so I can only give you an equation in terms of both:

Range from Porthcawl (in km) ~=3D Cloud Height in km / SIN(0.9*FOV)

For example, if the Porthcawl camera has a 90-degree horizontal FOV,
and the clouds are at 30,000' (9.14 km), then their range is about
65 km. The range from Pencoed would be about 14 km greater.

In closing, I don't know why you're getting upset with me for
doing all this work. This sounds like a classic case of shoot the
messenger because he isn't reporting the answer you want to hear.
Frankly, I could give a hoot weather it's a bolide or not -- it
makes absolutely no difference to me. It was just an interesting
problem, made more tantalizing by the lack of hard data and the
requirement to be inventive and resourceful. And in the end, I
at least ended up with a useful tool I can apply to any future
similar situation.

Now, if important new information comes to light -- like the
Porthcawl picture was taken at 8:30pm, or one or both of the
observers was in a completely different location than I've modeled,
fine. I'll run the numbers again. Perhaps the answer will come
out more to your liking. But based on the best present information,
the contrail could not have been produced by a bolide.

Cheers,
Rob
Received on Mon 06 Oct 2003 06:20:59 PM PDT