# "GO FAST" Footage from Tom DeLonge's To The Stars Academy. Bird? Balloon?

#### Mick West

Staff member

[Note: the above video is a simplified summary of the findings in this thread]

Source: https://www.washingtonpost.com/outl...bf9d112159c_story.html?utm_term=.7ef229f30df7
TTSA:
As the video starts, the sensor is in infrared “black-hot” mode – black elements in the display are warmer than the dark, or lighter color, areas. It is at zoom factor 1.0. The F/A-18 Super Hornet is at 25,000 feet altitude, 259 knots (~300 mph, Mach 0.61), and in level flight. The sensor is aimed 22 degrees below the horizon and 36 degrees to the left of the F/A-18’s direction. The ATFLIR tracking trap box is a square in the center of the screen. The ocean surface is clearly visible in the background.
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[NOTE: 259 knots is incorrect. The number indicated is CAS (Calibrated Air Speed), which is the air speed read by the instruments calibrated for sea level. Adjusting for 25,000 feet altitude the actual True Air Speed is 369 knots. See: https://www.metabunk.org/posts/220136/]

My first thought here is that it's a bird. When it first locks on we have:

-26°, 4.4 RNG, 25,000 feet barometer altitude.

Then later,

-35°, 3.4 RNG, 25,010 alt (essentially the same alt)

I'm assuming RNG is a straight line, not horizontal distance, then that gives us:
4.4*sin(26 degrees) = 1.92 nautical miles below the plane
3.4*sin(35 degrees) = 1.95 nautical miles

So assuming those numbers are more or less accurate then it's an object that's around 13,000 feet ((25000 feet) - (1.95 nautical miles)) in altitude, viewed from a jet at 25,000 feet. Basically it's half way between the jet and the ocean surface.

Hence the perceived motion of the object against the ocean surface, even if it were moving very slowly, would be the same as the speed of the jet itself. This is hugely magnified by the high zoom (NAR, or around 1.5° FOV). Here's an example of a static object that looks like it's moving through some trees:

The strangeness of the footage is largely a function of the ability of the ATFLIR camera to lock on to a white spot and track it. This accents the visual illusion that the object is moving because the parallax effect.

The bird (or other slow moving object, but I suspect a large soaring sea bird [UPDATE: Now I think a balloon is more likely]) hypothesis tallies with the angle. The object starts out at 43° to the left, and continues left to 58°

The white dot, whatever it is, would be invisible to the naked eye. It's in NAR mode, which has a FOV of 1.5°. Hence they were ONLY looking at it on the ATFLIR.

Similar to the GIMBAL footage, but without the glare. See:
https://www.metabunk.org/nyt-gimbal-video-of-u-s-navy-jet-encounter-with-unknown-object.t9333/

[Update 3/15/2018]
Analysis shows the object does not vary altitude much, and the jet is also flying horizontally, so much of the analysis can be done in an overhead view.

This animation shows the effect of varying the turn rate on the calculated speed. The blue line is the simple two point analysis of the target object path with jet (red line) traveling in a straight line. The orange line is the projected target object path with a variety of turn rates from the jet.

With this model, the speed of the object could be anything from 28 knots to over 100 knots. This speed is relative to the atmosphere at the level of the jet, and so is consistent with a balloon + wind differential from 13,000 to 25,000 feet. Or a self powered bird.

Update Dec 2018 - Great new video of a balloon filmed from a Helicopter showing the parallax effect.

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#### Brian Vincent

##### New Member
The first idea that I would want to explore is whether or not the "go fast" object is actually relatively stationary. During the first few seconds of the video, when the camera appears fixed, the angles are changing. This means that it's not actually fixed, but rather, the camera is panning in order to track a single spot on the ocean.

A stationary object, high up, would be expected to appear moving, relative to the ocean.

If it is relatively stationary, like a balloon, that would explain why it appears to have no wings or exhaust plume and isn't very hot.

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#### Mick West

Staff member
The first idea that I would want to explore is whether or not the "go fast" object is actually relatively stationary. During the first few seconds of the video, when the camera appears stationary, the angles are changing. This means that it's not actually stationary, but rather, the camera is panning in order to track a single spot on the ocean.

A stationary object, high up, would be expected to appear moving, relative to the ocean.

If it is relatively stationary, like a balloon, that would explain why it appears to have no wings or exhaust plume and isn't very hot.

Yes, that's essentially the gist of my post, above. A slow moving bird, and parallax.

#### Brian Vincent

##### New Member
I thought that a balloon would be more likely than a bird because 12,000 ft seemed rather high for birds to be flying. I was rather surprised to learn that 12,000 ft isn't very high and well within the range of many migratory birds and birds of prey.

https://en.wikipedia.org/wiki/List_of_birds_by_flight_heights

#### Mick West

Staff member
Here's the motion of the ocean and of the UFO from 1seconds 22 frames to 3seconds 2 frames.

The camera here is not fixed, it is panning to the left, going from 36L to 37L over the course of this segment. This complicates matters. It's also tilting down from 22° to 23°

i suspect the initial camera motion might be some kind of default ground tracking. After it locks onto the UFO/Bird this changes.

But I think the fact that the motions are parallel indicates they are both derived from the motion of the plane.

In fact with a FOV of 1.5° the camera MUST be attempting to track the ground in normal use. If the camera were not continually compensating for the motion of the plane then you would constantly be seeing the background just whizz past.

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#### Peter B

##### New Member
One problem common to all these TTAS videos is that they're just clips. No context. We don't know what happened before or after. If this one's a bird or a balloon (and why not, so far) how do we know one of the crewmen we hear didn't open the exchange by saying "Hey, is that a [gull/albatross/migrating dove down there? Betcha can't catch that on your FLIR!" —and so the guy does, with much whoo-hoo-ha from his mates. With all that kit to play with, and no war on, does anyone really expect these guys not to play games with it? (Infantrymen do the same with rifles after all. O, the stories one should not tell!)

#### Mick West

Staff member
Size estimates. The video frame is 950 pixels across in the Washington Post version. When the object is closest (3.3 nautical miles), the object appears around 12 pixels across. Hard to say exactly. But from these numbers we can calculate the angle subtended by the object as as 12/950*1.5 degrees)

tan(12/950*1.5 degrees)*3.3 nautical miles in feet =6.6 feet

Arguably you could say it's larger, but I think if anything it's smaller, as it's very blurry.

So what birds have a 6 foot wingspan, and can fly at 13,000 feet?

(or what other object, like weather balloons).

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#### Mick West

Staff member
One possibly significant point is that the object appears colder than the water. BLK means black=hot, but it's white.

It is (probably) at 13,000 feet. Where the air would probably be colder than the water. Would a well insulated bird still show up as cold (on average). Or does this lean towards a balloon?

#### Mick West

Staff member
It would be great o find some video of birds taken from planes. Here's one of a hawk taken from a helicopter. It's probably still moving at a similar speed to the chopper though - still looks weird.
Source: https://youtu.be/h_f7ElR3oVs?t=28s

#### JFDee

##### Senior Member.
The black/white thing is not helping much, unfortunately.

A bird against the open sky will most certainly show up 'warm'.

https://www.sciencedirect.com/science/article/pii/S1574954115001478
When a warm object, such as an animal, is in the thermal camera's FOV, it appears as a bright blob in the image.
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However, a water surface reflects sky conditions (with a grade that also depends on the viewing angle of the observer). So it can vary.

https://ubcsailbot.org/2014/12/28/using-ir-imaging-to-detect-floating-obstacles/
In one series of images taken the day before the actual day of the experiment, the water exhibits an opposite gradient. The reason for this is apparent from the corresponding optical photograph: we are facing the edge of a cloud front, so the water further away is reflecting the clouds, whereas the water closer to the camera is reflecting open sky. Since the clouds appear warmer than the sky, the result is what seems to be an inverse gradient.
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Bird feathers are good insulators. When adding the cooling effect of the air flowing around a bird in flight, it's not clear if it will appear 'warm' against a background with possibly variable heat reflection.

http://www.dailymail.co.uk/news/art...pictures-reveal-animals-hot-cold-secrets.html
The pelican has just been sitting on its feet - which is why they are so warm. Its feathers, however, provide excellent insulation and stop heat escaping.
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#### JFDee

##### Senior Member.
A very short FLIR video of a flying bird against sky and ground, from a freely available dataset provided by Oklahoma State University.

The appearance of the bird is ambiguous at least. Even against the sky it's not a significantly warm object.

http://vcipl-okstate.org/pbvs/bench/

#### Attachments

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#### igoddard

##### Active Member
Here are the opening two segments where the camera appears to move very slowly and the waves look pretty sharp. Each segment is run at half speed 3x then the other 3x, ...

It looks to me unremarkably like the cool feathers of a bird flying close over the sea. I also think we can make out a wing-flapping pattern (it sort of 'leaps' forward in steps, a differential rhythmic propulsion indicative of wing-flap-induced propulsion) that reminds me of the flying-insect UFOs called "rods."

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#### Whitebeard

##### Senior Member.
So what birds have a 6 foot wingspan, and can fly at 13,000 feet?
There are quite a few, but to be more accurate we are going to need to know where the incident happened, obviously its over water, so it rules out certain species such as vultures and buzzards, which are mainly found over land. But birds such as boobies and pelicans tend to be found in more temperate climes, where as others such as certain swans and geese tend to be more northern.

#### Kaen

##### Member
The ATFLIR also displays the closure speed (Vc), probably in knots.

If the object was stationary, the closure speed at the start of the lock would be approximately 253 x cos(44) x cos(26) = 163 knots, 253 being the speed of the jet and the object being at a horizontal angle of 44 degrees and a vertical angle of 26 degrees.

The measured closure speed is a bit higher, approx. 200 knots, which means that the object is travelling towards the jet. If we assume that the object is travelling in the same general direction but at different altitude, the additional 40 knots in closure speed (200 instead of 160) would mean that the object itself has a speed of 40/(cos(44) x cos(26)) = 60 knots (60 nm/hr). This corresponds to 70 mph which is the speed achieved by an albatross. An albatross has a length of about 5 feet and a wingspan of about 7 feet.

#### igoddard

##### Active Member
It seems to me the pilots are more engaged in the fun and excitement of target-acquisition training or challenge than freaking out about a UFO. While a couple times I seem to hear, "What is that thing?" in the mix of voices, there's no overall impression that these guys see the object itself as a serious issue. The issue seems to be 'can you get a lock on that target?' Wah hoo, you did it! If there is a "What is that thing?" stated in there, it's an aside at best. Seconds after the clip cuts a pilot might have answered that question, "It's a bird."

And once again we get a 30-second snippet. What else can they do to look like they're trying to trick us?! Ah yes, also fail once again to release chain-of-custody documentation after promising to do so.

#### JFDee

##### Senior Member.
Again, the TTSA release has made the main-stream news. Here is an opinion by Christopher Mellon, published in the Washington Post, ignoring all research that has been done since December:

https://www.washingtonpost.com/outl...2c125c-22ee-11e8-94da-ebf9d112159c_story.html

Excerpt:
A third declassified video, released by 'To the Stars Academy of Arts and Science', a privately owned media and scientific research company to which I’m an adviser, reveals a previously undisclosed Navy encounter that occurred off the East Coast in 2015.

Is it possible that America has been technologically leap-frogged by Russia or China? Or, as many people wondered after the videos were first published by the New York Times in December, might they be evidence of some alien civilization?

Unfortunately, we have no idea, because we aren’t even seeking answers.
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#### Mick West

Staff member
Again, the TTSA release has made the main-stream news. Here is an opinion by Christopher Mellon, published in the Washington Post, ignoring all research that has been done since December:
Christopher Mellon, as he notes, is part of TTSA. This isn't really news, it's just an opinion piece by a UFO enthusiast.

#### Agent K

##### Senior Member
Christopher Mellon, as he notes, is part of TTSA. This isn't really news, it's just an opinion piece by a UFO enthusiast.

Not just some UFO enthusiast, but one with a stake in TTSA. So instead of having experts debunk this and the previous TTSA videos, WaPo publishes an opinion by one of TTSA's people.

#### jamesrav

##### Member
"The strangeness of the footage". To me it doesn't even qualify as strange. How is this any different than early-era video games whereby the object stayed motionless and the background moved, creating the illusion of motion? Yes, the object looks like it's zipping across the ocean at super speed, but don't we all - by the age of 5 - have an experience whereby we think we're moving but actually something else is moving? "Everything is relative", didn't somebody famous say that?

#### Tom Mellett

##### New Member
Christopher Mellon, as he notes, is part of TTSA. This isn't really news, it's just an opinion piece by a UFO enthusiast.
It does seem very odd that for the long-awaited release of the “Third Video” by TTSA, there was only this OpEd by Mellon in WaPo. Most TSA fans were expecting another mainstream media article like the original NY Times story of last December 16, which was co-authored by Leslie Kean.

But it turns out that Leslie Kean and Christopher Mellon are 2 of the 5 Board Members for the UFODATA Project, which seeks “to break through the UFO taboo and do some real science on the problem.”
http://www.ufodata.net/team.html

With Tom DeLonge acting like the “Donald Trump of Disclosure,” I suppose it is comforting to know that there are responsible intelligent adults like Kean and Mellon in the “Disclosure Room” behind the garish storefront of TTSA. (On the other hand, “pay no attention to the man behind the curtain” who is Bob Bigelow, but I digress.)

#### Tom Mellett

##### New Member
Hello Mick,

I was reading a Facebook page discussing the video and debunking Metabunk when someone quoted this passage from the AATIP FB page which I could not access, but I’m sure it’s accurate.

Gary Nolan is a professor of genetics at Stanford and he is part of the “Dream Team” at TTSA. He reports:

“I am getting some of the other background information that 'debunks' West's silly reply. First bit of information... the speed of the object was 300-400 knots (about 350 to 460 miles per hour). As measured by radar.. So goddess help that "bird" should it ever hit the water at such a speed! The wind drag alone would rip off it's feathers! LOL."
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#### Mick West

Staff member
Hello Mick,

I was reading a Facebook page discussing the video and debunking Metabunk when someone quoted this passage from the AATIP FB page which I could not access, but I’m sure it’s accurate.

Gary Nolan is a professor of genetics at Stanford and he is part of the “Dream Team” at TTSA. He reports:

“I am getting some of the other background information that 'debunks' West's silly reply. First bit of information... the speed of the object was 300-400 knots (about 350 to 460 miles per hour). As measured by radar.. So goddess help that "bird" should it ever hit the water at such a speed! The wind drag alone would rip off it's feathers! LOL."

Can you post links if you are posting quotes.

I suspect that this "background information" is just a back-of-a-envelope calculation. But either way I'd be happy to take a look at it.

#### Robert Sheaffer

##### Member
Bruce Maccabee posted his preliminary analysis on the Facebook group UFO Pragmatism. His conclusion is that the object is about 10-15 feet in diameter, and moving at 100 knots:

"TENTATIVE CALCULATIONS
B. Maccabee
Mar. 9, 2018
(((Plane at 25000 ft = 4.1 nm Object altitude calculated as: (4.1 nm [height of plane] – (4.1 slant range [plane to object]) x sin 22 = 4.1 – 1.54 = 2.46 below airplane altitude; Height of object = (height of plane – distance below plane ) = 4.1 – 2.5 = 1.6 nm (not close to surface) The sensor is aimed 35 deg left of plane axis and this angle increases to 57 or 58 so at the end so the object was traveling with a velocity component parallel to the track of the airplane. Estimated size of object based on apparent size of black-hot image is approx. (1.5 deg angular width of screen based on narrow FOV) x ([1.5 mm to 2mm diameter of black dot image size on 92 mm wide screen]/[92mm screen width]) x 0.0174 rad/deg x 4.1 nm[slant range] x 6077 ft/nm = 10 to 15 ft!....At 4.1 nm range to the object, the distance across the 1.5 deg FOV is (4.1nm) x [1.5 deg x 0.0174 rad/deg]= 0.1 nm. It crosses the FOV at about a 45 deg angle so the actual approximate distance across the FOV is 0.1 nm/0.707 = 0.14 nm; it crosses in 4 to 3 sec implying a differential speed of the plane and object of 0.14 nm/ ( 4 to 3 sec)/(one hour/ 3600) = 126 to 170 kt)…Since the plane is going at about 250 kt the object was going at the speed approx. (250 – 150) = 100 kt in the same direction as the airplane but clearly slower)"
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#### Tom Mellett

##### New Member
Can you post links if you are posting quotes.

I suspect that this "background information" is just a back-of-a-envelope calculation. But either way I'd be happy to take a look at it.
Hi Mick,

The problem is that I was on a UFO FB group which needs subscribing to and someone was quoting Gary Nolan from a FB group called AATIP which I cannot find. I’m sure the links will show up somewhere soon. Also not sure if Gary was making a “back of the envelope” calculation or else has access to actual radar tracking data that wasn’t released.

#### Tom Mellett

##### New Member
Meanwhile I posted Gary Nolan’s quote on Paracast and got this reply from someone who questions how Gary would have access to radar data.

https://www.theparacast.com/forum/t...udy-media-monitoring.19069/page-2#post-270340

So he is claiming they have radar data? That is apparently in conflict with the data that is shown by the instruments of the jet on video. And if they had such radar data, why didn't they track it with the radar then?

Since they claim all the background information was removed in the release approval process, why would a consulting geneticist of a private company know something like radar data that is not in the clip? Elizondo isn't supposed to reveal any classified/secret data to anybody, right?

I'm calling bs on his claims, for all those reasons.

(Luckily it wasn't anywhere close hitting the water, since it was flying at around 4 kilometers = 13100 feet.)
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#### Agent K

##### Senior Member
Hello Mick,

I was reading a Facebook page discussing the video and debunking Metabunk when someone quoted this passage from the AATIP FB page which I could not access, but I’m sure it’s accurate.

Gary Nolan is a professor of genetics at Stanford and he is part of the “Dream Team” at TTSA. He reports:

“I am getting some of the other background information that 'debunks' West's silly reply. First bit of information... the speed of the object was 300-400 knots (about 350 to 460 miles per hour). As measured by radar.. So goddess help that "bird" should it ever hit the water at such a speed! The wind drag alone would rip off it's feathers! LOL."
Content from External Source

It's moving about 1 degree per second, which at a range of 4 nmi is about 290 mph relative to the sensor, which happens to be moving at about that speed.

#### Justin Shaw

##### New Member
Nice analysis @Mick West. I've followed your lead and extracted the az/el/rng data from the video which allows you to compute the relative position of the object based on 30 frames per second.
Code:
``````### seconds, deg
az_data = array([
[12 + 10./30, -43],
[13 + 10./30, -44],
[13 + 20./30, -45],
[14 + 19./30, -46],
[15 + 13./30, -47],
[16 + 13./30, -48],
[18 +  0./30, -49],
[21 +  6./30, -50],
[23 +  6./30, -51],
[24 + 18./30, -52],
[26 +  6./30, -53],
[27 + 18./30, -54],
[29 +  6./30, -55],
[30 + 13./30, -56],
[31 + 19./30, -57],
[32 + 25./30, -58],
[33 +  0./30, -58]
])

## seconds, DEG
el_data = array([
[12 + 10./30, -26],
[13 + 19./30, -27],
[16 +  6./30, -28],
[18 + 25./30, -29],
[21 +  7./30, -30],
[23 + 13./30, -31],
[25 + 25./30, -32],
[28 +  1./30, -33],
[30 +  1./30, -34],
[32 +  7./30, -35],
[33 +  0./30, -35]
])

## seconds, NMI
rng_data = array([
[12 + 10./30, 4.4],
[13 + 10./30, 4.3],
[15 +  3./30, 4.2],
[17 +  4./30, 4.1],
[19 +  1./30, 4.0],
[20 + 29./30, 3.9],
[22 + 28./30, 3.8],
[24 + 28./30, 3.7],
[27 +  1./30, 3.6],
[29 + 13./30, 3.5],
[31 + 22./30, 3.4],
[33 +  0./30, 3.4],
])``````
This data indicates that the object is traveling toward the camera with a closing speed of about 180 KTS.
Here is a link to the raw data: https://photos.app.goo.gl/h172DtyuNcAiGbuS2

Subtracting out the camera's forward velocity I get this 3D plot of the position. Red dot indicates initial position.
https://photos.app.goo.gl/WgmGltNaYHFe3oBX2

I'm open to suggestions, but this object does not appear to be moving at a great speed.

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#### igoddard

##### Active Member
I plotted with red dots each location the flying entity appears in the two opening segments with minimal camera motion. These segments are run at half speed. To me, the paths look consistent with the slightly erratic path of a bird. There's also two points I note where the object seems to slow down, but it's all so blurred and grainy I can't be sure.

Notable is that its brightness often dims down to almost invisible. That would seem to be consistent with wing flaps, changing the surface area exposed to the lens. However, when the camera locks onto it later it does not seem to fade out. So there are some notable differences with the before- and after-locked object.

When that camera locks on in the rest of the footage you can’t detect any erratic motions or fading of its brightness. When the camera gets locked on, it looks more like a sphere-shaped object. But then IR only shows temperature, not necessarily mass shape. But really?! Putting any extraordinary belief into just another grainy pin-head sized UFO seems foolish. #3 underwhelms!

Last year WaPo said this (bold added):
"intelligence officer Luis Elizondo quietly arranged to secure the release of three of the most unusual videos in the Pentagon’s secret vaults."
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So the three TTSA videos we've examined are the best of the best. Just wow!

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#### Agent K

##### Senior Member
I thought that a balloon would be more likely than a bird because 12,000 ft seemed rather high for birds to be flying. I was rather surprised to learn that 12,000 ft isn't very high and well within the range of many migratory birds and birds of prey.

https://en.wikipedia.org/wiki/List_of_birds_by_flight_heights

I thought a balloon is more likely because a bird would appear warmer than the background.
Also, I wonder how the WSO detected it in the first place. Did it show up on radar or on FLIR in wide field of view?

#### Mick West

Staff member
Subtracting out the camera's forward velocity
What value did you use for this?

#### Agent K

##### Senior Member
Last year WaPo said this (bold added):
"intelligence officer Luis Elizondo quietly arranged to secure the release of three of the most unusual videos in the Pentagon’s secret vaults."
Content from External Source
So the three TTSA videos we've examined are the best of the best. Just wow!

The WaPo article also said something that at least Leslie Kean and maybe Elizondo disputed:
Elizondo, in an internal Pentagon memo requesting that the videos be cleared for public viewing, argued that the images could help educate pilots and improve aviation safety. But in interviews, he said his ultimate intention was to shed light on a little-known program Elizondo himself ran for seven years: a low-key Defense Department operation to collect and analyze reported UFO sightings.
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It suggested that Elizondo tricked the Pentagon into releasing the videos, but Leslie Kean told Open Minds UFO Radio that the memo she read didn't have any false pretense, though it may have been a different memo. Elizondo may have said this as well, but I don't remember. The point is to take the WaPo reporting with a grain of salt.
That said, it makes sense that Elizondo would want to release the most unusual videos, and it's almost funny how disappointing they were, like literally "It's a bird, it's a plane."

Edit: Elizondo did deny any false pretense in a recent interview. But he also said, "We got very clever at dual-using" like putting out requirements that could apply to studying ballistic missiles or "other objects."

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#### Justin Shaw

##### New Member
@Agent K I agree that if these are three of the best videos, it is not very convincing. Nice work @igoddard The apparent change in can also be attributed to camera trajectory. Can you extract the raw data from thos plots? Also, if anyone can extract aircraft attitude from the artificial horizon, I can add that to the simulation above and solve for x, y, z and v of the object.

I added the camera position and found an error in the previous plot. Here is the new plot in absolute position from the initial range solution.

@Mick West , I used 258 knots level flight. Could do better with attitude assuming coordinated turns.

https://photos.app.goo.gl/A0niEc6ZAG84VKMn2

Code:
``````from numpy import *
from pylab import *
from scipy.interpolate import *

#		 t sec	az deg
az_data = array([
[12 + 10./30, -43],
[13 + 10./30, -44],
[13 + 20./30, -45],
[14 + 19./30, -46],
[15 + 13./30, -47],
[16 + 13./30, -48],
[18 +  0./30, -49],
[21 +  6./30, -50],
[23 +  6./30, -51],
[24 + 18./30, -52],
[26 +  6./30, -53],
[27 + 18./30, -54],
[29 +  6./30, -55],
[30 + 13./30, -56],
[31 + 19./30, -57],
[32 + 25./30, -58],
[33 +  0./30, -58]
])
el_data = array([
[12 + 10./30, -26],
[13 + 19./30, -27],
[16 +  6./30, -28],
[18 + 25./30, -29],
[21 +  7./30, -30],
[23 + 13./30, -31],
[25 + 25./30, -32],
[28 +  1./30, -33],
[30 +  1./30, -34],
[32 +  7./30, -35],
[33 +  0./30, -35]
])
rng_data = array([
[12 + 10./30, 4.4],
[13 + 10./30, 4.3],
[15 +  3./30, 4.2],
[17 +  4./30, 4.1],
[19 +  1./30, 4.0],
[20 + 29./30, 3.9],
[22 + 28./30, 3.8],
[24 + 28./30, 3.7],
[27 +  1./30, 3.6],
[29 + 13./30, 3.5],
[31 + 22./30, 3.4],
[33 +  0./30, 3.4],
])
ts = data[:,0]
ephem = interp1d(ts, data.T)
azs = data[:,1]
els = data[:,2]
rngs = data[:,3]
vs = data[:,4]
az = interp1d(az_data[:,0], az_data[:,1])
el = interp1d(el_data[:,0], el_data[:,1])
rng = interp1d(rng_data[:,0], rng_data[:,1])

def pos(t):
vel = array([258 * KTS, 0, 0])
return array([0, 0, 0])[newaxis] + vel[newaxis,:] * (t[:,newaxis] - az_data[0, 0])

NMI = 1852.
HOUR = 3600.
DEG = pi / 180.
KTS = NMI / HOUR
FEET = FOOT = .3048

rel_speed = (diff(rng_data[:,1] * NMI) / diff(rng_data[:,0])) / KTS

t = arange(15, 30, .1)
azs = az(t)
els = el(t)
rngs = rng(t)

x = rngs * NMI * cos(azs * DEG) * cos(els * DEG)
y = -rngs * NMI * sin(azs * DEG) * cos(els * DEG)
z = rngs * NMI * sin(els * DEG)

xyz = vstack([x, y, z]).T
p = pos(t)

ax = subplot(4, 1, 1)
plot(az_data[:,0], az(az_data[:,0]))
plot(t, -arctan2(y, x) / DEG)
ylabel('Az [deg]')

subplot(4, 1, 2, sharex=ax)
ylabel('El [deg]')
plot(el_data[:,0], el(el_data[:,0]))
plot(t, arcsin(z / linalg.norm(xyz, axis=1)) / DEG)

subplot(4, 1, 3, sharex=ax)
ylabel('Range [nmi]')
plot(rng_data[:,0], rng(rng_data[:,0]))
plot(t, linalg.norm(xyz, axis=1) / NMI)

subplot(4, 1, 4, sharex=ax)
ylabel('Rel vel [kts]')
xlabel('t [sec]')
plot(rng_data[2:-1,0], rel_speed[1:-1])

import matplotlib as mpl
from mpl_toolkits.mplot3d import Axes3D
fig = plt.figure()
ax = fig.gca(projection='3d')

ax.plot([0], [0], [0], 'bo')

ax.plot(x / NMI, y / NMI, z / FEET, 'r-')
ax.plot(x[:1]/NMI, y[:1] / NMI, z[:1] / FEET, 'ro')

xlabel('x [nmi]')
ylabel('y [nmi]')
ax.set_zlabel('z [feet]')

fig = plt.figure()
ax = fig.gca(projection='3d')

ax.plot((p[:,0])/NMI, (p[:,1]) / NMI, (p[:,2]) / FEET, 'b-')
ax.plot((p[:1,0])/NMI, (p[:1,1]) / NMI, (p[:1,2]) / FEET, 'bo')

ax.plot((x + p[:,0])/NMI, (y + p[:,1]) / NMI, (z + p[:,2]) / FEET, 'r-')
ax.plot((x[:1] + p[:1,0])/NMI, (y[:1] + p[:1,1]) / NMI, (z[:1] + p[:1,2]) / FEET, 'ro')

xlabel('x [nmi]')
ylabel('y [nmi]')
ax.set_zlabel('z [feet]')
show()``````

Last edited by a moderator:

#### Mick West

Staff member
@Mick West , I used 258 knots level flight. Could do better with attitude assuming coordinated turns.

That number there varies between 252 and 259.
The M number varies from 0.61 to 0.62, flipping at 254/255

Those numbers are a bit confusing, as 254 is not 0.61 of the speed of sound. However:
http://www.hochwarth.com/misc/AviationCalculator.html

Hence, the 254 number is CAS, Calibrated airspeed. It's not groundspeed, and it's not True Airspeed (TAS) which is actually 369 knots (which matches 0.61285*602, where 602 is the speed of sound in knots at 25,000 feet pressure altitude)

The groundspeed depends on the windspeed at 25,000 feet. An additional complication would be how this differers from the airspeed at 13,000 feet.

But how does your chart look with an aircraft ground speed of 369 knots?

Last edited:

#### Mick West

Staff member
This data indicates that the object is traveling toward the camera with a closing speed of about 180 KTS.
Assuming a simple difference there of 369-258, or 111, that presumably reduces your calculated closing speed to ~69 knots?

#### Kaen

##### Member
During the entire period when the ATFLIR is locked on the object, the object’s speed can be estimated on a moment by moment basis.

At every moment during the locked-on period, the speed vector of the F18 can be projected onto the slant vector (the vector pointing towards the object). This gives the F18’s contribution to the closure speed:

Vc,F18 = V x cos(left) x cos(down)

Where V is the airspeed of the F18 in the ATFLIR display, ‘left’ is the angle to the left in the ATFLIR display, and ‘down’ is the vertical angle in the ATFLIR display.

The object’s contribution to the closure speed is:

Vc,obj = Vc – Vc,F18

Where Vc is the closure speed in the ATFLIR display.

If we assume that the object travels approximately along the same line as the F18 (plus or minus 20 degrees), but on a different altitude, the object’s real velocity can be estimated as:

Vobj = Vc,obj / (cos(left) x cos(down))

In this way I estimated the object’s speed at every second during two periods in the official GO FAST video, one period where the F18 is flying level (1:35-1:39) and one period where the F18 is in a stable banking position to the left (1:43-1:55).

The results are below.
(I also played a bit with the angle between the object’s line-of-motion and the F18’s line-of-motion, but until a deviation of plus or minus 20 degrees the results are basically the same.)

Conclusion: The average estimated speed of the object is 80 knots, and it seems to be traveling at a constant speed with a standard deviation over the entire lock-on period of only 7 knots (which could be caused by measuring errors of the sensors involved).

Note: If the real ground speed of the F18 is higher, the object’s speed is even lower…

T left down RNG Vc V ALT Vc,F18 Vc,obj V,obj

1:35 43 26 4,4 220 253 25000 166 54 82

1:36 45 27 4,3 210 254 25000 160 50 79

1:37 46 27 4,3 210 254 25000 157 53 85

1:38 47 27 4,2 200 254 25000 154 46 75

1:39 48 28 4,2 200 254 25000 150 50 85

T left down RNG Vc V ALT Vc,F18 Vc,obj V,obj

1:43 50 30 3,9 180 254 25010 141 39 69

1:44 50 30 3,9 180 254 25010 141 39 69

1:45 50 30 3,8 180 254 25000 141 39 69

1:46 51 31 3,8 180 255 25010 138 42 79

1:47 52 31 3,7 170 254 25000 134 36 68

1:48 52 32 3,7 170 255 25010 133 37 71

1:49 53 32 3,7 170 255 25000 130 40 78

1:50 54 33 3,6 170 255 25010 126 44 90

1:51 54 33 3,6 160 256 25010 126 34 69

1:52 55 34 3,5 160 256 25010 122 38 80

#### Mick West

Staff member
Note: If the real ground speed of the F18 is higher, the object’s speed is even lower…

See above. The true air speed is 369 knots, you might want to redo your post.

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