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.
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