ATFLIR and range information (RADAR/LASER/Passive range?)

jarlrmai

Senior Member.
In the "Go Fast" video when the object tracking starts 2 figures instantly appear on the MFD video screen these are:

RNG and V/C

1623487573640.png



which are thought to show range in nautical miles and closing velocity in knots.

These figures were claimed by the TTSA to be the range and closing velocity from the jet to the object, this seems to make sense and other information on the display has been confirmed to be accurately identified by TTSA from various sources.

https://thevault.tothestarsacademy.com/2015-go-fast-footage

1623487617351.png


This figure was used along with altitude and angle of deflection of the ATLFIR camera to determine that object was at ~13000 feet, this and analysis done of the speed of the jet and the change in tracking angle was then also used to determine that object was not moving fast. These calculations directly contradicted the claims of TTSA that this object was low and fast as below:

"The unidentified vehicle appears as a white oval shape moving at high speed from top right to lower left of the screen flying very low over the water."

Given the simplicity of this maths this then raised questions about the quality of TTSA's analysis. However even given this no-one has claimed that the figures on screen are wrong before. Now we have claims from Chris Lehto about the accuracy of this figure, so where does the figure actually come from?

Links to to some places where this subject is mentioned

https://www.metabunk.org/attachments/a1-f18ac-746-100-atflir-principles-of-operation-pdf.44937/
https://forums.vrsimulations.com/su...ing_Infrared_(FLIR)#A.2FA_FLIR_Pointing_Modes
https://forums.vrsimulations.com/support/index.php/A/G_Advanced_Targeting_FLIR_(ATFLIR)
https://forums.eagle.ru/topic/272552-atflir-laser-in-aa-mastermode/
https://forums.eagle.ru/topic/266488-atflir-a-a-capability/

Possible options and discussions/information based on the various sources.

1. LASER, the ATFLIR has a ranging laser, the manual says "7. The ATFLIR provides two air-to-air modes: pointed, and autotrack. Air-to-Ground and air-to-air laser range finding is also provided.
  • LTD/R is visible but does not flash Lehto says L flashes but in the ATFLIR sim manual LTD/R is mentioned as flashing when the laser ranges of course it only mentions it in A/G mode..
  • ATFLIR sim manual only talks about the laser in A/G mode this is different to the manual but it might indicate laser not generally used for A/A ranges or not implemented.
  • DCS sim user says "Laser is not used for ranging in AA. The range is either from FLIR passive ranging or the FLIR Autotrack target merely being correlated to a Radar target and thus fused into a single MSI trackfile, and the range data would be from the Radar. With no passive range or another range contributor then the trackfile for the FLIR target would be angle-only without range."
2. RADAR, the RANGE could come from a RADAR track, the RADAR and the ATFLIR can talk to each other via the MSI link
  • The ATFLIR manual says "The radar system provides the functions listed below: a. air target range, range rate"
  • There are mentions on the sim forums that the ATFLIR will correlate RADAR tracks that match the LOS of the ATFLIR, essentially the system knows when the ATFLIR is looking at the track the RADAR has and overlays the RADAR info
  • "FLIR Autotrack target merely being correlated to a Radar target and thus fused into a single MSI trackfile
  • TWS (Track While Scan) mode in the ATFLIR manual shows RNG etc it looks slightly different
  • 1623495860821.png
  • If they had a radar track, why not slave the ATFLIR to it? No heading shown on ATFLIR? Maybe just messing/practising with autotrack hence excited voices when track occurs?
3. Passive Ranging using angles, there a mentions of ATFLIR having passive ranging capabilities
  • Laser is not used for ranging in AA. The range is either from FLIR passive ranging or the FLIR Autotrack target merely being correlated to a Radar target and thus fused into a single MSI trackfile, and the range data would be from the Radar. With no passive range or another range contributor then the trackfile for the FLIR target would be angle-only without range."
  • Mentions of some method of calculating range using angle rate in https://forums.eagle.ru/topic/266488-atflir-a-a-capability/
  • "And angle rate = range" Not sure how this works but it is mentioned here https://www.mathworks.com/help/fusion/ug/passive-ranging-using-a-single-maneuvering-sensor.html
  • This could be CW Lemoines "trigonometry" quote.
  • I can't find any mention that this happens in the sim manual or the ATFLIR manual.
4. Passive ranging using a database of images and pixel size or some sort of "assume a fighter jet" scale
 
...
1. LASER, the ATFLIR has a ranging laser, the manual says "7. The ATFLIR provides two air-to-air modes: pointed, and autotrack. Air-to-Ground and air-to-air laser range finding is also provided.
...
2. RADAR, the RANGE could come from a RADAR track, the RADAR and the ATFLIR can talk to each other via the MSI link
  • The ATFLIR manual says "The radar system provides the functions listed below: a. air target range, range rate"
    ...

This does call into question Chris Lehto's expertise on the ATFLIR when he says:
"It's a passive sensor, it cannot create its own range"
"It's a passive sensor, it can only receive information"
in the first 2 minutes of www.youtube.com/watch?v=Tyw4JA00AMc
 
He never flew with ATFLIRs as he wasn't an F-18 Pilot.

I appears some "passive ranging" capability is available in the ATFLIR. It seems it may be very imprecise though.
 
He never flew with ATFLIRs as he wasn't an F-18 Pilot.

I appears some "passive ranging" capability is available in the ATFLIR. It seems it may be very imprecise though.

It's hard to know for sure though, the only mention I can find to support passive ranging is some posts on the sim forums at the moment if it is inaccurate i wonder if it would displayed as matter of factly as it was in go fast.

I lean towards it being the radar given we know it can provide a range and LOS correlation is mentioned. I wonder if Mick could ask the technician he interviewed if he is aware of how this range might be obtained I assume if this figure was a questioned number at the time he would have asked.
 
My 2 cents:
  • They probably didn't use the laser due to lack of indicators. Since it can cause at least eye damage, it's probably not used against unknown targets in the air carelessly, even if that seems to be technically possible in A-A mode.
  • Some have proposed passive ranging would be based on assumption of stationary target, but that would be an odd assumption. There aren't many stationary targets 13,000ft in the air, and the computer should know ground was twice as far.
  • It's also hard to see how database image comparison could work. It saw a small blob. What we see is more or less what that 640x480 pixel sensor could see from that distance. The situation would of course be different if the radar could provide additional details, but then it should be able to provide the range too.
  • It would be similarly odd and potentially dangerously misleading assumption if the computer just assumed everything is fighter sized, or something like that. And if there was some way for the pilots to feed in their own assumption of size, why would they make such assumption for what they saw? (unless such setting was left there previously for other reasons)
  • Passive ranging would work for targets for which the range (and with that the assumed size) was initially/intermittently acquired by the radar or laser. So maybe it doesn't work quite by itself, but may augment other mechanisms.
  • 1 LOS, what ATFLIR only seems to have, limits other options.

I agree with @jarlrmai that the range probably came from the radar. It should be able to pick the target much more easily after the optical lock was taken, and LOS was known, even if it was otherwise a faint signal. And if that's the case, there doesn't seem to any particular reason to suspect inaccuracy, at least based on what the video shows.
 
I think you can turn on the laser for A/A if you want but it's never used in practice as it's not accurate for A/A if it were firing the LTD/R text would flash.

As in I don't think the range displayed in Go Fast is an inaccurate laser range because the laser is not firing. I think the range comes from a RADAR track correlated to the LOS of the ATFLIR when autotrack is acheived.
I thought the range came from the radar, and I haven't heard a good reason why it didn't. Is the target outside the radar's field of regard? It's a little suspicious that the RNG appears immediately after the video tracker locks on. In the FLIR1 video, it takes some time before the RNG appears as 99.9. If the target is just a balloon, the radar might not detect it, unless it has metallic parts.

Would the LTD/R flash just when ranging with the eye-safe training laser rangefinder, not the high-powered tactical laser designator? I'd think the laser rangefinder would be more accurate than the radar.

If it's doing passive ranging, in A/G mode it could simply calculate the range to the ground along the LOS, but then the RNG would show the target being at sea level, not in the air. Or it could assume the target is stationary and triangulate its range, in which case it could mistake a fast-moving surface target for a stationary target thousands of feet above the water. But if the target really is hovering thousands of feet above the water, it would be ranged correctly. In A/A mode, you generally wouldn't assume the target is stationary.
 
The main reasons discussed are

1. If they had a RADAR lock why not slave the ATFLIR to it? Rather than slew on the TDC and use the box to get autotrack, you would almost use SLAVE certainly do this in a real situation, however the nature of the chat could indicate they were playing/testing the box acquisition mode.

2. If they had a RADAR track of the object they'd have altitude and this would be shown on the display but it's not clear that this is the case. It is perhaps configurable? The FLIR tech Mick interviewed mention them "requesting range" perhaps it's a button/toggle on the MFD, we just don't know enough and its not covered in sims/manuals. You would think someone who actually used the pods would be able to clear up this stuff.

3. Similarly the RADAR data that is claimed to exist and implied to have been investigated would also show this object was not low/fast. However this seems counter to TTSAs own words on the website given they explicitly state this figure as being the slant range to the object.

LASER would less likely to get a consistent range reading trying to lase an inflight object at significant range the accuracy would have to be pinpoint to maintain a reflection, this seems unlikely. And yes if it missed you'd expect it would return ground distance, if it can reflect the ocean floor, or no RNG or 99 etc like in the FLIR1 video.

RADAR ranges if you have a good track would be the most accurate ranging method.
 
The main reasons discussed are

1. If they had a RADAR lock why not slave the ATFLIR to it? Rather than slew on the TDC and use the box to get autotrack, you would almost use SLAVE certainly do this in a real situation, however the nature of the chat could indicate they were playing/testing the box acquisition mode.

2. If they had a RADAR track of the object they'd have altitude and this would be shown on the display but it's not clear that this is the case. It is perhaps configurable? The FLIR tech Mick interviewed mention them "requesting range" perhaps it's a button/toggle on the MFD, we just don't know enough and its not covered in sims/manuals. You would think someone who actually used the pods would be able to clear up this stuff.

3. Similarly the RADAR data that is claimed to exist and implied to have been investigated would also show this object was not low/fast. However this seems counter to TTSAs own words on the website given they explicitly state this figure as being the slant range to the object.

LASER would less likely to get a consistent range reading trying to lase an inflight object at significant range the accuracy would have to be pinpoint to maintain a reflection, this seems unlikely. And yes if it missed you'd expect it would return ground distance, if it can reflect the ocean floor, or no RNG or 99 etc like in the FLIR1 video.

RADAR ranges if you have a good track would be the most accurate ranging method.

Kudos to you for digging into this. I believe understanding the FLIR on screen indicators, what they mean, and what they don't mean, is going to play a big part in figuring this out.

I think we're seeing some confusion from the operators (i.e. pilots) themselves. This, along with the failure to do math, is sowing a lot of misunderstanding.
 
The main reasons discussed are

1. If they had a RADAR lock why not slave the ATFLIR to it? Rather than slew on the TDC and use the box to get autotrack, you would almost use SLAVE certainly do this in a real situation, however the nature of the chat could indicate they were playing/testing the box acquisition mode.
Does SLAVE continuously track the target or just slew the camera in the general direction of the target?
2. If they had a RADAR track of the object they'd have altitude and this would be shown on the display but it's not clear that this is the case. It is perhaps configurable? The FLIR tech Mick interviewed mention them "requesting range" perhaps it's a button/toggle on the MFD, we just don't know enough and its not covered in sims/manuals. You would think someone who actually used the pods would be able to clear up this stuff.
Who says it would be shown on the ATFLIR display?
3. Similarly the RADAR data that is claimed to exist and implied to have been investigated would also show this object was not low/fast. However this seems counter to TTSAs own words on the website given they explicitly state this figure as being the slant range to the object.
That's pretty speculative.
LASER would less likely to get a consistent range reading trying to lase an inflight object at significant range the accuracy would have to be pinpoint to maintain a reflection, this seems unlikely. And yes if it missed you'd expect it would return ground distance, if it can reflect the ocean floor, or no RNG or 99 etc like in the FLIR1 video.
But if it can't reflect the ocean floor at significant range, then it would only reflect the target at closer range. Would be funny if it popped the balloon, but it's not that high-power.
RADAR ranges if you have a good track would be the most accurate ranging method.
Why is radar more accurate than a higher frequency laser?
 
Agree with Jarlrmai that it is strange how the target was acquired.

They seem to get the target by manually slewing the pod and then using autotrack. This is unusual. If they had a clear radar track they would just press one button and ATFLIR would point towards it.

This might push us toward the "there wasn't a good radar return on the object". And therefore that's why the optical tracking and passive ranging was used.

I think it would make sense for passive ranging to work by assuming a fighter size (that's what most of the A/A targets will look like). However, I think we conclusively know the object was pretty small though so in that case ATFLIR would range the object further away. So it can't be what we are seeing here.

We might not have enough info to conclusively close this unless we get testimony by one of the pilots maybe.
 
It's displayed in A/A mode, if it's enabled it's 'boxed' ie surrounded by a rectangle indicating enabled, it's enabled by pressing a button that is next to the word on the outside of the display.

Note L+S is boxed if the SLAVE is to the launch and steer target, slave is boxed if it's slaved to another track I'd imagine most of the time they slave to L+S
 
Maybe it's possible the radar was set to automatically acquire targets in the ATFLIR's FOV, and just did it when the object settled in the middle.

Speculation, but that's what seems to be happening. The RNG value pops up about four frames after the target is acquired (box turns to bars)
 
Maybe it's possible the radar was set to automatically acquire targets in the ATFLIR's FOV, and just did it when the object settled in the middle.

Speculation, but that's what seems to be happening. The RNG value pops up about four frames after the target is acquired (box turns to bars)
Wouldn't it be more surprising if it didn't try to acquire a target that is already optically locked, and so clearly of interest?

The video doesn't show any other potential targets in that direction all the way to the ground. So if the radar would find even the faintest single target it would normally disregard along that line, wouldn't it make sense for it to consider that to be the same what is tracked optically and provide the range?
 
Maybe it's possible the radar was set to automatically acquire targets in the ATFLIR's FOV, and just did it when the object settled in the middle.

Speculation, but that's what seems to be happening. The RNG value pops up about four frames after the target is acquired (box turns to bars)

This is mentioned a little on the DCS forums

https://forums.eagle.ru/topic/272552-atflir-laser-in-aa-mastermode/

On 5/28/2021 at 12:36 PM, dorianR666 said:
Does this mean ATFLIR auto track should generate its own MSI trackfile? Would it be then selectable on ATTK RDR page? I wondered how to slave radar to ATFLIR target, seems its not possible in DCS currently.
Yep, so to slave the Radar to FLIR, you'd just acquire it like any other trackfile on the Az/El or Attack. You could also make it the L&S and so on. The reason there is no dedicate "Radar-FLIR slave mode" is because of this. There's no need for it with MSI.
 
The A1-F18AC-742-100 radar system document contains details on how FLIR autotrack target can be priorized and designated as the L & S target, including this:

"When RSET pushbutton is
selected, the DT2 target designation is removed and
the radar STT target is designated as the MSI
L & S target. If the radar is not in STT, the FLIR
autotrack target is designated as the L & S target.
When the RSET pushbutton is pressed and neither
radar or FLIR are in track then the L & S target
designation is removed"

And various versions of this for different computer models:

"The digital data computer
determines the rank and priority of the MSI
targets. MSI target rank is based on target identity,
time-to-go (range/range rate) for normal targets, or
angle to boresight for angle only track targets. The
highest ranked target is initially designated as the
MSI L & S target and the next seven targets are
identified with the rank of 2 through 8 inside their
HAFU symbols. One of these seven targets or a low
priority target may be designated as the DT2 target.
MSI targets are prioritized as described below:
a. MSI L & S target
b. targets under missile attack in decreasing
time-to-go order
c. MSI DT2 target
d. radar STT target or FLIR autotrack target
e. other MSI targets based on their rank."

The way I read those, they seem to support the idea that the initially optically locked target would automatically become the selected radar target and that would lead to the radar based range being displayed.

Edit:
There's also some references to passive ranging in SIM mode:

"The digital data computer ignores range and
velocity inputs from the radar and starts passive
ranging functions on the MSI L and S target using
angle inputs only. This option provides practice
with angle only track targets and passive ranging."
 
Last edited:
Back
Top