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Location: UFOUpDatesList.Com > 2007 > Feb > Feb 14

Re: Radar Operation At O'Hare? - Shough

From: Martin Shough <parcellular.nul>
Date: Sat, 13 Jan 2007 16:05:48 -0000
Fwd Date: Sun, 14 Jan 2007 09:25:56 -0500
Subject: Re: Radar Operation At O'Hare? - Shough

>From: Frank Warren <frank-warren.nul>
>To: UFO UpDates - Toronto <ufoupdates.nul>
>Date: Sat, 13 Jan 2007 05:56:44 -0800
>Subject: Radar Operation At O'Hare?


>Is it possible that the UFO was in the 'cone of silence'?

>Moreover, the report indicates that when the object exited the
>airport through the cloud deck, it did so at a very "high rate
>of speed"; if an image was indeed caught by RADAR, (at that
>point) certainly it would appear as an anomaly one would think.

>If in fact the object was in a cone of silence', by O'Hare
>RADAR antennas perhaps it was picked up by another radar
>antenna elsewhere.

>Where is the next closest RADAR antenna in proximity to

The disposition of ATC and ARTC radar heads around Chicago is a
complicated question, not yet fully answered. I supplied my own
summary report on this to NARCAP recently. Some sites are
definitely identifiable, others not - unless Don Ledger has
succeeded in clearing this up; I know he's been trying, no doubt
others have too.

AFAIK so far, the main radars serving the C-90 ATC area around
O'Hare are ASR-9s, of which the FAA National Airspace
Architecture lists three, ORD, ORD#2 & ORD#3. However the site
of only one is known exactly, one approximately, whilst the
third is conjectural, and it is not entirely clear which number
relates to which location. Moreover only two radars are
mentioned in all other sources. There is also joint-use
FAA/military ARSR-3 long range coverage of the region at higher
altitude, plus a number of weather radars (which are not very
favourably placed in terms of space-time resolution as I
discussed in a previous post).

You mention a "cone of silence" but this is a zenithal volume
above an antenna, and an object at  1700-1900 ft could only be
in this cone if it were _immediately_ above an antenna sited on
top of the C Concourse. There is certainly no radar here.

There is an ASR radar antenna on a tower to the west of the
airfield about 0.9 st mi. The elevation angle of the object from
here would be in the region of 18 degrees, well outside the cone
of silence and eminently detectable. However I believe that this
ASR antenna may anyway be the old ASR-7, originally retained as
back-up for the ASR-9 but now disused since the ORD TRACON
facility moved about 50 miles away to Elgin, whilst the #1
antenna is now much further west of the airport. This remains to
be confirmed, but, in any case, the nearest ATC radar does not
have a cone of silence where the object was reported.

I don't want to get into the whole thing in detail here, but
although the C-90 area responsibility extends in theory from
surface to 13,000 ft at O'Hare this doesn't mean that everything
in that volume is detectable let alone paid attention to. Mainly
the concentration is on SSR code traffic, and no controller is
going to be looking for primary targets hanging right over the
gates - even if such a stationary echo were distinguishable from
clutter. The ASR-9 is also able to show precipitation
reflectivity from weather radars overlaid on the same screen
which can occlude primary echoes (this doesn't matter for
controlled aircraft which are shown as big bright data blocks -
 and as Don pointed out these can themselves obscure primary
echoes in a crowded airport environment).

Whether any area radar picked up an object arriving and
departing vertically remains to be determined when the radar
tapes are forthcoming from the FAA. And for that we await the
results of Dick Haines' application.

Martin Shough

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