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Location: UFOUpDatesList.Com > 2007 > Jan > Jan 20

Re: Radar Operation At O'Hare? - Warren

From: Frank Warren <frank-warren.nul>
Date: Sat, 20 Jan 2007 06:09:55 -0800
Fwd Date: Sat, 20 Jan 2007 13:58:17 -0500
Subject: Re: Radar Operation At O'Hare? - Warren

>From: Martin Shough <parcellular.nul>
>To: <ufoupdates.nul>
>Date: Sat, 13 Jan 2007 16:05:48 -0000
>Subject: Re: Radar Operation At O'Hare?

>>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


Sorry for the slow response... this one slipped through the

>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.

Thank you for clearing that up.

>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

Thanks Martin for this important information; this "sheds light"
on exactly what an operator would have to contend with in regards
to what's appearing on the screen; methinks the layman assumes
it's a "black and white issue" - clearly it's not.

I look forward to Dick's findings.



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