Date: Mon, 18 Oct 2010 14:20:48 +0100 (BST)
Subject: Montauk incident an IFO Thread

Dan Wilson wrote:

Brad wrote:
The radar site reported this was a weather balloon launched from Idlewild Airport at about 6:00 p.m., or 79 minutes before the radar-only (no visual) sighting began at 7:19, when it was tracked at 68,000 ft.  Standard meteorological balloons rise at about 1,000 ft per minute so it is almost an exact match, or actually an exact match if the round-number launch time of 6:00 was really say 6:11 (my understanding is that target times to launch met balloons can be off by up to 1/2 hour or even more -- Jan is the expert on met balloons he can tell you). 

During the 10 minutes of the radar tracking the object rose 10,200 ft or almost exactly the balloon rise rate of 1,000 ft/min (it's 1,020 ft/min, near perfect match).  Its horizontal velocity was only 3 miles in 10 minutes or 18 mph, typical wind velocity. 
Somethings just do not fit an IFO evaluation on this case.
No where was there any 18 mph winds.
The winds in this area were given as
5000 feet 29 knots
10,000 feet 33 knots
16,000 feet 47 knots
20,000 feet 43 knots
30,000 feet 61 knots
50,000 feet 59 knots
80,000 feet 28 knots
And was there an IFF signal detected from this object?
The observation was on FPS-20, FPS-6 radars and IFF: UPX-6
The UPX-6 was a function of the radar itself which received and then enhanced IFF codes being picked up by the radar. It had three or four frequencies itself (present day transponders have 7,700 separate codes). The UPX-6 acted pretty much the same way as the raw skin returns work today with the target blip being brighter and identifiable once the radar set queried it. When the radar beam struck an aircraft with IFF the usual signal would (and still does) bloom brighter on the scope. That way it could be identified as a friendly.
See the following:
UPX-6 Radar Recognition Set
The AN/URX-6 is a receiver transmitter designed to operate with other IFF (Identification Friend or Foe) or SIF (Selective Identification Features) equipment as part of an aircraft identification system for an associated radar set. The Primary function of the equipment is to transmit and receive coded signals between radar identification equipment and target aircraft within the range of the IFF/ SIF system. The receiver and transmitter are tuned by changing operating crystals and by manual screwdriver adjustments adjacent to these crystals. The transmitter is factory aligned for 1020 MHz operation,
although its overall tuning range is 990 MHz to 1040 Hz. The receiver is similarly factory aligned (at 1100 MHz), and may be tuned for any frequency between 1080 MHz and 1130 MHz. The AN/UPX-6 is compatible with the following Coder-Decoder Groups: OA-1266, OA-1267, OA-1268, OA-1269, OA-1271, OP-1272, 0A-2397, OA-2605, AN/GPA-78 or AN/SPA-64.
Capability: 6 has one tunable channel each for transmission and reception of coded signals in the IFF/SIF system.
Transmitter - 990-1040 mc
Receiver - 1080-1130 mc
Power Output: 1.5 kW Peak
Operating Voltages and Power Requirements: 105, 117 or 125v ac, 60 or 100 cps, single ph, 250 w
Type of Presentation: PPI and B indicators of associated radar set
Pulse Width: 1 µsecond
Pulse Repetition Rate: 180 to 120 pps (adjusted to conform with pulse repetition rate of associated radar)
Receiver Bandwidth:
Broad - 8 to 11 mc - 60 db
Narrow - 5 mc - 70 db
Receiver Input Impedance: 50 ohms
Receiver Output Impedance: 72 ohms
Frequency (IF): 60 mc
Weight: 77 pounds
Manufacturer: Radio Receptor, Inc. (TM 11-487C-1)


Date: Mon, 18 Oct 2010 16:54:23 +0100
From: Martin Shough <>
Subject: Montauk incident an IFO

Brad's analysis seems on the money to me.
Dan objects to Brad's rough 18mph speed example in comparison with the winds aloft shown in the report. In fact the horizontal target speed, allowing for the 3 mile range increment and a 4 degree azimuth change is closer to about 25 mph or 22 knots during the rise from 68k to 78kft. Wind at 80k was 28 knots. Nothing is known about the winds below that until you get down to 50k, so it's quite possible that it averaged 22 knots through the 10k of the observation.
Bearing in mind that the target coordinates are approximations based on estimating the centroid of a fuzzy arc on the tube phosophor that is itself 1/8" wide and also has some depth on the range axis equal to at least half the pulse length (corresponding to errors in the order of +/- 1000s and 100s of ft respectively), and then measuring this position off the scope by eye, then I don't think the match is bad at all.
The only thing you can say is that the target heading - from 282 deg @ 40mi to 286 deg @ 43mi - would be roughly NNW, whereas winds at all recorded heights (230-240 deg) would have taken a balloon NE. But it's a small hook on which to hang hopes of an exotic unknown. Maybe the wind direction fluctuated between the data points? 
As for the IFF business, although the UPX-6 is included under "observation by" I suggest this is only because it was listed as a standard component of the radar set-up. If there had been an IFF transponder code it would surely have been explicitly mentioned in the sighting description. The report only describes a "pip" from a skin return on the surveillance radar. And I can't imagine that if there was an IFF code mentioned the compiler of the report would have said there was an "excellent possibility" that it was the Idlewild weather balloon.
And remember nobody saw anything visually at all. There isn't much here to get excited about.
Martin Shough