UFO UpDates
A mailing list for the study of UFO-related phenomena
'Its All Here In Black & White'
Location: UFOUpDatesList.Com > 2011 > May > May 16

Re: Radar Detection Of UFOs

From: Martin Shough <parcellular.nul>
Date: Sun, 15 May 2011 18:34:07 +0100
Archived: Mon, 16 May 2011 06:45:19 -0400
Subject: Re: Radar Detection Of UFOs


>From: Ralph Howard <rhjr.nul>
>To: <post.nul>
>Date: Sat, 14 May 2011 16:02:53 -0400
>Subject: Re: Radar Detection Of UFOs

>>From: Peter Davenport <director.nul>
>>To: <post.nul>
>>Date: Fri, 13 May 2011 06:37:06 -0700
>>Subject: Re: Radar Detection Of UFOs

>>>From: Martin Shough <parcellular.nul>
>>>To: <post.nul>
>>>Date: Thu, 12 May 2011 18:37:21 +0100
>>>Subject: Re: Radar Detection Of UFOs

>>>>From: Ralph Howard <rhjr.nul>
>>>>To: post.nul
>>>>Date: Thu, 12 May 2011 08:55:27 -0700 (PDT)
>>>>Subject: Radar Detection Of UFOs [was: SETI Summary]

><snip>

>>>>... keeping up with this website makes a lot of
>>>>sense, because of the potential for NEXRAD recording
>>>>something
>>>>anomalous.

>>>It is intriguing. I want to take a closer look. Thanks for the
>>>tip.

<snip>

>Thanks Martin and you also Peter for bringing out these points.
>One thing to each of you - Peter, I've read about your idea for
>a passive system and for what little it's worth I agree 100% it
>would do the job. Martin, the first time I saw some of your
>posts here in recent years, I looked through my 200+ UFO books
>and grabbed my copy of UFOs 1947-1987 and saw that "Yep, it's
>_that_ Martin Shough!" I remembered your article (Radar And The
>UFO I think), and I'm honored to converse with you. (That is
>you, right?) The wonders of the Internet age...

Hi Ralph

Yes, that's me. Now a lot older and perhaps a little wiser. A
quarter-century on it still rankles that I was never shown
proofs of that piece and that my text came out mangled!

>So - these shortcomings you point out, Martin. I guess a
>question I'd ask you is, given NEXRAD shortcomings, if Dr. Fries
>and his crew deem the system worthy of monitoring for meteor
>re-entries, might we on the UFO side also _potentially_ expect to
>see anomalous returns of interest? Not that I myself have the
>time, I've got all I can handle in GA! But how valuable, or not,
>do you think it might be if Somebody in UFO research somewhere,
>can keep up with it? Call this question 1.

>Question 2 might be, what about in UFO case work? For UFO
>sightings I've pitched within MUFON the idea of looking at
>NEXRAD (and I'm not the first) (but lately, might be!) because
>the data are free & fast & easy to get. And, can be ordered for
>dates say 1, 6 or 12 months back. Obviously the short sighting
>durations versus NEXRAD's 6-minute-apart or 10-minute-apart
>updates are a problem, but we do have long-duration sightings
>and on some of them (multiple witnesses, bright colored lights,
>substantial altitude & stationary behavior) I might argue that
>a _lack_ of a return is telling us something (i.e. it really
>ought to be there).  So - what do you think of its value when
>investigating selected cases that have, say, long durations and
>are high up enough to be above ground clutter? The technical
>material you can find online says NEXRAD can and does detect
>birds, insect swarms, aircraft, and so on. Why not UFOs?

I looked further at what Fries and others are doing, with the 3D
renderings and so on, and was impressed. But I think their
results show why I was sceptical about the idea at first blush.
Context is all. What's impressive is how, with a lot of
technology and human expertise, they can infer at least
something from almost no data!

As you can see, what they are doing is taking reports from
eyewitnesses or video or other sources, using trigonometry and
photogrammetry to calculate likely meteor tracks, and then going
to the NEXRAD coverage to look for possible confirmation.
Sometimes they find a few scattered pixels of echo in the likely
area. Without the triangulated sighting reports and videos these
would be nothing but a few specks of noise in the radar picture.
There's a good deal of guess work. I suspect that if these radar
plots were analysed raw it would be very hard to show any
significance, but with the knowledge that something probably did
fall there they are sometimes able to infer a trend from just a
few pixels, which they think might help refine a predicted
impact point. So this is not much use for real-time "UFO
detecting" but could be useful after the fact.

I have tried using weather radar in this way in a couple of
cases, both times with at best ambiguous results. One was the
Nov 2006 Chicago O'Hare sighting where I looked at NEXRAD. You
can read about that in the NARCAP report. The other was in the
April 2007 Channel Islands case. You can find the reports on
that at my website. In fact you can get the NARCAP report there
as well.

But even with relatively long-duration sightings like these
where observers describe a thing staying basically put for some
time , experience suggests that you end up interpolating between
a very few data points and using guesswork and cunning, because
the total dwell-time in the radar coverage is so very short, the
effective resolution cell is so big (data block are about a
square km) and there are always ambiguities. In the Channel
Islands case there was only one weather radar anywhere in the
area, on Jersey. And even where there is overlapping NEXRAD
cover part of the problem will be that in these UFO cases we're
dealing with very low targets. A target at about 1000ft, say, is
going to be below the horizon for radars a few tens of miles
away, so in practice you may not have the chance of more than
one single pixel of echo on just one altitude cut of one radar
during a many-minute sighting. The multiple long range cover of
overlapping radars will tend to become more useful for targets
at higher altitudes.

I didn't have those neat 3D visualisations - that's a great tool
Fries is using. I don't know if it's a NEXRAD product or if he's
importing the data into something like Radarbox? But i'd like
one!

It might be worth quoting (below) my conclusion on the NEXRAD
data from the Chicago case to illustrate how I hoped to use it
and what the uncertainties were. No doubt Fries & co would be
able to make a better job of it.


Martin Shough

---
The NEXRAD weather radar data (Section 4) are not inconsistent
with the presence of a radar-reflective target close to the 1900
ft cloud base within several minutes of the time of the visual
report2, but this is not probative evidence given the spatial
size of the resolution cell, the slow update rate, and the
distribution of stochastic echo evident in the several
screenshots shown in Fig. 8.

Some comments on these factors are appropriate.

The radar was operating in mode VCP-32, which is one of two
Clear Air modes usually used for routine monitoring in periods
of quiet weather. The scan pattern (see Fig.9) takes over 10
minutes beginning with the low 0.5 deg cut. Two types of data
are collected, the base reflectivity data (or simple echo
intensity) and the doppler velocity data (measuring radial
precipitation droplet velocity relative the the radar). The
antenna then proceeds to scan several slices at higher
elevations to build up the whole coverage volume. The data of
interest here are for the 0.5 deg base reflectivity, obtained
during the first 1-minute rotation of the scan pattern. (Neither
the 0.5 deg doppler velocity product nor the higher cuts showed
any data in the relevant area.)

The NEXRAD software generates automatic labels on the screen
image. Referring to Fig.12, we can see that the elevation angle
of the nominal 0.5 degree cut is actually 0.53 deg, and that the
calculated height AGL of the beam at the relevant range z =
0.518 km, or about 1700 ft. This represents the boresight
elevation, so the vertical coverage of the ~1 deg cross-range
pencil beam will be from about 450 ft to 2950 ft. This will be
calculated for a standard atmosphere, however, and given
moderate superrefractivity (Section 4) these figures probably
tend to overestimate the true heights. In any case, the reported
object height clearly not only lies within the coverage zone but
is quite close to the main gain. Note also that the WSR-88D
employs horizontal linear polarisation to optimise reflectivity
from the flattened lenticular profiles of falling water
droplets. This would also tend to maximise echo from an object
having the type of horizontal ellipsoidal symmetry reported.

In this Clear Air mode the radar is extremely "alert" to faint
echo (it automatically switches to a less sensitive
Precipitation Mode when significant weather is detected). The
reflectivity shown is an average over the whole resolution cell
(Fig.10) and could be echo either from very weak sources
dispersed over a large area, or from a localised region of much
higher reflectivity somewhere inside that footprint. Surface
weather reports state "no precipitation", and the 1635 echo is
probably too faint for an area of precipitation anyway. However
there is the possibility of transient surface clutter echoes.
The splash of colour we see around the antenna in the small-
scale area image is clearly ground clutter in this case. The
echo we are interested in is not constant, i.e. doesn't appear
on successive scans, so this might normally suggest it isn't
ground echo. But it may be that AP conditions (for which there
is evidence, see Section 4) fluctuate over time, allowing the
radar to pick out faint ground echoes intermittently.

The radar can also image flocks of birds, or even insects and
small airborne particulates, in addition to the summed
reflectivity of one or more aircraft on approach or take-off
that may be passing through that elevation slice at that time.
The data block concerned (Fig. 10) seems to cover mostly apron
and taxiways, but conceivably aircraft airborne at a few hundred
feet near the SE and W ends respectively of runways 32L/14R or
9R/27L could be detected. Another conceivable source of
intermittent faint echo in AP conditions might be airport
buildings themselves, in particular the tall traffic control
tower buildings. The ground-control tower appears to be within
the radar cell footprint, although the new 250 ft AGL tower
building falls just outside it.

In summary, the NEXRAD VCP-32 radar mode is very sensitive and
there are several possible sources of faint echo. Echo is found
in the relevant cell timed at 1635 CST. However each of the four
scans investigated, sampling roughly 10% of the total coverage
period between 1616 and 1645, shows a certain amount of
intermittent echo of this type in the general area. In fact
there is echo more than twice (~ 4dB) as strong in the same cell
in the 1616 CST scan at a time when, apparently, no UFO was
being seen. It can reasonably be argued that finding some echo
within about a square km of the site within a few minutes of the
sighting time is not too improbable. So whilst the height and
location of the echo is not inconsistent with the presence of an
object as reported, caution is recommended in drawing any
conclusions.



From Report on Radar Coverage and Propagation Conditions in the
area of Chicago O'Hare International Airport, Nov 7, 2006,
Section 6, Report of an Unidentified Aerial Phenomenon and its
Safety Implications at O'Hare International Airport on November
7, 2006Case 18

http://www.narcap.org/reports/010/TR10_Case_18a.pdf



Listen to 'Strange Days... Indeed' - The PodCast

At:

http://www.virtuallystrange.net/ufo/sdi/program/

These contents above are copyright of the author and
UFO UpDates - Toronto. They may not be reproduced
without the express permission of both parties and
are intended for educational use only.

[ Next Message | Previous Message | This Day's Messages ]
This Month's Index |

UFO UpDates Main Index

UFO UpDates - Toronto - Operated by Errol Bruce-Knapp


Archive programming by Glenn Campbell at Glenn-Campbell.com