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  1. Mick West

    Mick West Administrator Staff Member

    MUFON 91964 Metabunk Compare.

    This case of a "UFO" submitted to Mufon, is described as:
    https://mufoncms.com/cgi-bin/report...=f1_submitted_datetime+DESC&case_number=91964
    The first impression was correct. However the resultant photo seems at little confusing.
    Metabunk 2018-05-14 10-05-08.

    The problem is that you naturally interpret this as a set of three lights. But what it actually is is a single light, the red collision avoidance strobe. This is a very bight flashing light, and illuminates other parts of the plane, even in daytime.
    767-beacon-animated.

    In this case it's illuminating the engines.
    Metabunk 2018-05-14 10-08-40.

    Another clue are the two faint bright red spots under the main light
    Metabunk 2018-05-14 10-12-03.
    This matches quite well with the wheel wells of a 737
    Metabunk 2018-05-14 10-14-02.

    The time given is 2018-05-08 8:59PM, that's 2018-05-09 (next day) 2:59AM in UTC. The camera exif time gives the same UTC time - maybe that's common for astrophotography? Looking at that location a likely candidate is SWA1988 from Phoenix to Omaha, which was passing just to the South at 39,000 feet.
    Metabunk 2018-05-14 10-21-17.

    Another thing that throws people off here is the thin lines. These are the long exposure traces of navigation lights, but seem odd as you can only see two of them, and they don't seem to line up with the other lights. However if you look carefully, or just boost the levels, then you can see there actually are three lines.
    Metabunk 2018-05-14 10-29-45.
    What's more the one of the left is green and the on on the right is red, which matches standard wingtip lights.

    They don't line up for a somewhat unintuitive reason - planes do not fly in the direction they are facing. The fly in the direction they are facing at their airspeed PLUS the velocity of the wind relative to the ground. So if there's a crosswind the motion of the plane can be 5° or more off from the direction it is facing.
     

    Attached Files:

    Last edited: May 14, 2018
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  2. marrowmonkey

    marrowmonkey Member

    For a minute I wondered why the plane didn't block the stars behind it in the picture (or does it?), but that is of course because it's a long exposure photograph.
     
  3. Robert Sheaffer

    Robert Sheaffer New Member

    Excellent analysis. Looking at that overlay of the plane on the photo, there is no doubt this is what we are seeing.
     
  4. Mick West

    Mick West Administrator Staff Member

    It would be nice to get some video of a 737 doing the same thing. Unfortunately most available video seems to have landing lights on as well, which somewhat obscures the effect. But here's a demonstration of the light illuminating the engines:
    Metabunk-2018-05-14-10-49-49.
     
  5. Mick West

    Mick West Administrator Staff Member

    That's another thing that throws people off, even if they don't really think about it their brains assume it's a small craft because they can see all those stars.
     
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  6. Mick West

    Mick West Administrator Staff Member

    We can tell the direction of the camera because:
    Setting the location, date and time, and searching for NGC4631 gives us:
    Metabunk 2018-05-14 21-12-35.

    Zooming in
    Metabunk 2018-05-14 21-13-39.

    So that's that heading (Az) of 92.5 degrees, and looking up (Alt) at 67°. The plane was at 39,000 feet, so that puts the camera 39000/tan(67 degrees) =16,500 feet to the West of the plane's track
     
  7. Mick West

    Mick West Administrator Staff Member

    But if the camera is looking East, the if we align the photo with the night sky at that time, then it seems to suggests the plane was flying roughly to the West, not the same as the plane I'd identified earlier.
    Metabunk 2018-05-14 22-21-24.
     
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  8. Mick West

    Mick West Administrator Staff Member

  9. jarlrmai

    jarlrmai New Member

    Nice work Mick, I love the detective aspect to this.
     
  10. TEEJ

    TEEJ Senior Member

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  11. Astro

    Astro Active Member

    The reflections off the engines are interesting and not something I've captured before, but I do occasionally capture a jet passing through the field of view. Here's a shot from 2013 while I was tracking comet ISON:
    [​IMG]
     
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  12. marrowmonkey

    marrowmonkey Member

    Assuming the galaxy is 10' long as he says, the distance (in arcmin) between the engines is about 3' or 0.04-0.06 deg.
    Az/Alt = 93/67 deg
    Aztec elevation: 5646 ft
    Airplane altitude: 38000 - 39000 ft

    Using the following formula we can get an estimate of what the distance in feet between engines should be:
    v = 2 arctan(x / (2 h))
    where v is the width in angles (degree)
    h distance to airplane in ft
    x distance between engines in ft

    Taking the altitude of 67 deg into account:
    h = (38500-5650) / sin 67
    Assuming no roll or pitch (and a flat earth :)) the apparent distance between the engines is
    x = X sin 67
    where X is the real distance between engines

    this gives us:
    X = [ 2 (39000-5650) tan(0.06/2) ] / [ (sin 67)^2 ] ~= 41 ft
    X = [ 2 (38000-5650) tan(0.04/2) ] / [ (sin 67)^2 ] ~= 26 ft
    best est:
    X = [ 2 (39000-5650) tan(0.049/2) ] / [ (sin 67)^2 ] ~= 34 ft

    I.e. the engines are about 26-40 ft apart.

    From what i can tell the engines on a Boeing 777-200 is about 72 ft apart, but on a Boeing 737 they are 32 ft apart. (I couldn't find particularly reliable data on distance between engines on a boeing 777 though.)

    So the Boeing 737 and flight SWA1988 seems like the best candidate.
     
    Last edited: Jun 19, 2018
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  13. Astro

    Astro Active Member

    Brilliant, wish I had thought of that. Here's the astrometry of his image:
    http://nova.astrometry.net/user_images/2160988#annotated
    Indeed this does confirm the galaxy ID and the coordinates at the center of the strobe light (12hr 42m 29.4s, 32d 36' 25") correspond to an alt of 67.3 degrees and an azimuth of 92.9 degrees at 2:59 UTC from Aztec, NM.
    sin(altitude) = sin(declination)*sin(latitude)+cos(declination)*cos(latitude)*cos(hour angle)
    cos(azimuth) = (sin(declination)-sin(latitude)*sin(altitude))/(cos(latitude)*cos(altitude))
    We can then use the astrometrically solved image to get a more precise reading of the angular separation of the engine reflections:
    http://h.dropcanvas.com/lbgg4/enginesep.jpg
    Looks like your best estimate of 0.049 degrees was just about right on the mark according to my measurement, which as you show above corresponds to ~34 feet part give or take. Not bad.
     
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  14. marrowmonkey

    marrowmonkey Member

    Someone did something similar in another thread, I just realised you could do the same here.
    In hindsight I think I made a mistake with x = X sin 67. I was thinking the plane was flying from left to right horizontally, but it looks more like it is coming straight at the camera, and in that case x = X. The reflections on the engines are probably a bit off center so 0.049 is a bit smaller than the actual engine separation. But you get about the same range anyway, so the conclusion is the same.

    Is there is a website where you can see historical flight data (for free)?
     
  15. Mick West

    Mick West Administrator Staff Member

    Planefinder has older data for free. I've got pro accounts for free on Flightradar24 and FlightAware because I feed ADS-B to them, so I can get older data from them too.
     
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  16. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    I can get track data for a particular flight back to about 6 months, but I can't replay all flights for a particular date and time, as far as I know. Here is UAL275.
    UAL275.PNG
     

    Attached Files:

    Last edited: Jun 21, 2018
  17. marrowmonkey

    marrowmonkey Member

    I tried looking at planefinder but it looks like planes appear and disappear suddenly. Is it because they get their data from ADS-B and there is not good coverage everywhere?

    It looks like it was only a few km from the camera position so the plane must have flown very close to Aztec.
     
  18. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Isn't the position of the camera a known unknown? The unknown plane, if UAL275, has a known track . This would put him slightly north, and a bit west of the track of UAL27, somewhere in the bush about 20 km. north of Aztec? Capture.PNG
     
  19. marrowmonkey

    marrowmonkey Member

    True, but it looks like UAL275 was also a boeing 777-200. If I'm right about it having about 70 ft between the engines then the angular separation of the engine reflections should be closer to 0.14 degrees.
    2*arctan((70*sin(67)) / (2*(32000-5650))) = 0.14

    I couldn't find any exact dimensions but I got about 70 ft from this picture:

    777exterior200_300_short_range.
     
  20. Mick West

    Mick West Administrator Staff Member

    [​IMG]

    It's a pretty short flash, so I the image itself shows the relative size and spacing of the engines. If it's just the fairing being lit then it seems to fit the 737 better. But here's the 777 overlaid. Still plausible.
    Metabunk 2018-06-23 06-20-59.
     
  21. marrowmonkey

    marrowmonkey Member

    A 777-200 would have an angular separation of 0.14 degrees at that altitude though, but Astro measured it to be closer to 0.049.
     
  22. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    I just looked at the original photo, and noticed a second strobe flash, and a passing satellite? They should provide a bit more information to fix the location etc. IMG20032mod.
     
    Last edited: Jun 23, 2018
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  23. Mick West

    Mick West Administrator Staff Member

    Remarkable right angle there. I’d assumed it was another plane. But maybe not with the single light.
     
  24. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    The flash periods are probably quite accurate, although this is not a requirement, as I understand things.
    . Capture.PNG
    https://aviation.stackexchange.com/questions/24151/airplane-strobe-light-pattern
    From the speed of the plane and flash period you can get a distance scale and distinguish Airbus and Boeing by comparing to wing span.
    You should be able to get camera Latitude by adjusting the viewer position in Stellarium until the satellite track and stars line up where they are supposed to be. The exposure time span must include the satellite position/time. Because of a long exposure and speed of a satellite the longitude would not be very precise. I am on a backup PC so I don't have it available now.
    I wonder if these are wing tip and tail strobes:
    Capture.PNG
     
    Last edited: Jun 24, 2018
  25. marrowmonkey

    marrowmonkey Member

    I don't know how to figure out what satellite it could have been. (Could it also have been a meteorite?)

    If they are stars they are incredibly uniform; same coloured lines are the same length and parallel:

    upload_2018-6-25_3-7-15.

    If that's the strobes, then the yellow lines provides a measure of the wingspan which is much easier to find data on for different aircraft type (than the engine separation).

    We can also measure the distance between flashes, but we don't know the frequency. I assumed the red beacon flashes 1 time per second just to see what figures one would get, and they look sensible in that case.

    If choosing between a 737 and a 777, the numbers fit a 737 the best (wingspan of about 100 ft). The 777s wingspan of 200 ft would put it at an altitude above 60'000 ft.

    Measured from picture
    If 56.5 px = 0.0491636 deg (derived from astro's measurment) then:

    Red flash
    1480,2 px = 1,288 deg
    Distance:
    813 ft @39'000 ft altitude
    788 ft @38'000 ft
    642 ft @32'000 ft​
    Speed (assuming 1 flash/sec)
    892 km/h
    865 km/h
    705 km/h​

    Wing flash
    226,0 px = 0,197 deg
    124 ft @39'000 ft
    120 ft @38'000 ft
    98 ft @32'000 ft​
    This corresponds to about 0.15 duration relative to the red flash​

    Wingspan
    212,75 px = 0,185 deg
    117 ft @39'000 ft
    113 ft @38'000 ft
    92 ft @32'000 ft​

    Specs from Wikipedia articles
    Boeing 737
    Cruise speed: 796 km/h
    Wingspan:
    93 ft [ 737-100/200 ]
    95 ft [ 737-300/400/500 ]​
    Cruise speed: 838 km/h
    Wingspan:
    113-117 ft [ 737-600/700/800/900 ]
    118 ft [ 737 MAX-7/8/9/10 ]​

    Boeing 777
    Cruise speed: 892 km/h
    Wingspan:
    200 ft [ 777-200/200ER/300 ]
    213 ft [ 777-F/200LR/300ER ]​
     
    Last edited: Jun 24, 2018
  26. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Last edited: Jun 25, 2018
  27. marrowmonkey

    marrowmonkey Member

    Yes, it looks like it matches the flash pattern.
    The A3xx wingspan also fits:
    Airbus A3xx
    Cruise speed: 829 km/h
    Wingspan:
    A318: 112 ft
    A319 A320 A321: 117 ft​
     
  28. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    Attached Files:

    Last edited: Jun 25, 2018
  29. Clouds Givemethewillies

    Clouds Givemethewillies Active Member

    A bit early, but good track: Capture.PNG Capture.PNG