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Location: UFOUpDatesList.Com > 2007 > Jan > Jan 3

Re: The '06 O'Hare UFO - Shough

From: Martin Shough <parcellular.nul>
Date: Wed, 3 Jan 2007 16:31:53 -0000
Fwd Date: Wed, 03 Jan 2007 11:47:06 -0500
Subject: Re: The '06 O'Hare UFO - Shough

>From: Michael Tarbell <mtarbell.nul>
>To: ufoupdates.nul
>Date: Tue, 02 Jan 2007 10:39:55 -0700
>Subject: Re: In the sky! A bird? A plane? A... UFO?

>>From: Martin Shough <parcellular.nul>
>>To: <ufoupdates.nul>
>>Date: Mon, 1 Jan 2007 15:35:15 -0000
>>Subject: Re: In the sky! A bird? A plane? A... UFO?


>>Well, a number of ground staff and pilots as witnesses to a low-
>>altitude daylight object over a major airport has to add up to
>>one of the most intriguing cases I've heard for a while. I hope
>>references to any follow-up investigations get posted here.

>Hi Martin,

>This is intriguing indeed. The observation that the passage of
>the object created a "hole" in the overcast is particularly
>interesting. There would seem to only be two ways for this to
>happen (but perhaps an atmospheric scientist will chime in):

>(1) the water droplets in the cloud were heated to the vapor
>state; or,

>(2) the size distribution of the droplets was modified such
>that they no longer were effective scatterers at visible

>For case #1 it should be possible to put constraints on the
>radiative power of the object based on the size of the "hole".
>It seems that a black body radiator would have to be extremely
>hot to produce such an effect, to the extent that it would glow
>in visible wavelengths (at odds with the dark grey color
>ascribed to it). But perhaps it radiated at a specific
>wavelength (e.g., microwaves).

>For case #2, the most straightforward scenario is that the
>droplets coalesced into larger ones and rained out, but the
>mechanism to bring this about is not obvious. Perhaps some
>local stratification of electric charge?

>In principle the appearance of this "hole" would have altered
>the radar signature if the cloud as well, although I wouldn't
>know if this could be detected by airport systems. I defer to
>your radar expertise here.

Hi Mike

I don't have info on the radar set-up at O'Hare but in general I
wouldn't expect useful coverage of areas directly over the
airport buildings by any ATC radars at O'Hare. They probably
would probably be eliminating cloud or rain anyway by a mixture
of techniques such as circular/elliptical polarisation and
doppler MTI. So you're right about changing radar
characteristics of the cloud but this could be academic unless
there was weather radar active at the time, which obviously
would be optimised to detect the cloud deck.

Changes in droplet size, shape, density and velocity might all
be detected, in principle, but whether or not the "hole" would
actually be seen even then would be uncertain I think, because
how the radar wavelength and all these other variables relate to
the droplet density and the angle of elevation at which the
cloud deck is illuminated would determine how far the radar
could "see into" the cloud, not to mention the size of the hole
in relation to the range, azimuth and altitude dimensions of the
radar's resolution cell, which might be much larger than the

It's a good point though that _if_ we had reliable data on a
volume of cloud evaporated then it might be possible to do this
calculation. I recall there was case, I believe in the northern
US or Canada in 1947, where a bolide-like UFO was photographed
apparently cutting a swathe through cloud and Projectr Sign
noted the possibility of doing a similar calculation (though
I've always wondered in that case whether the apparent path
through the cloud might not be shadow cast by a trail far above,
having seen similar effects caused by high jet contrails). But
anyway it's interesting.

As for how a "hole" might form, yes a narrow band emission in a
mm/cm range optimised for absorption by water droplets seems
more likely than a broad spectrum one. If not evaporation then
charge separation is one means, as you suggest. Mechanical
and/or thermal displacement of the air could also be factor.

If there was a real UFO that went straight up then it may be
that radars off of the airfield had a better chance of seeing it
- if not ARTCC then maybe places like KPWK the Chicago Executive
Airport only about 8 nm away, a continuously open public
airfield with ILS and largely military traffic that may well
have Airfield Control radar though I don't know.

Two other points worth noting here about visibility from the
Tower: Apparently the UFO was seen "sitting motionless over
Concourse C of the United terminal. No controllers saw the

According to AirNav:


there are two limits to visibility from the O'Hare tower. (This
is presumably the tower shown on the FAA Airport Diagram at:

at 905 ft MSL, but that height matches the "new tower at 250 ft
AGL" mentioned by Don Ledger in another post, and Don says this
is still being built, so I don't know.)

Anyway, a portion of Taxiway Y near the United Airlines hangar
is apparently not visible from the Control Tower, though the
nature of the obstruction is not described. If the United
terminal and the United hangar are physically nearby, then this
implies the possibility of resricted visibility from this Tower
in the direction of the UFO, though only up to a certain unknown
elevation of course. Probably this is irrelevant.

There is also another restriction:


The approach end of Runway 32 Right is in a direction roughly NE
from the Tower shown on the FAA map. Presumably cold weather is
very possible in November in Chicago. If so then the steam plume
could have restricted tower visibility to the NE. Whether this
has any relevance to the position of the UFO I've no idea but
it's worth bearing in mind.

The remote possibility that a "hole" in low cloud could be
related to some 'belch' in the exhaust plume from a
malfunctioning airport heating plant has occurred to me, but I
don't think it very likely!

Martin Shough

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