Laser Spot Tracking mechanics

[CalvinAz]

Perhaps as many people know, laser guided munitions have a maximum seeker range from which they can see the laser. For Paveway bombs this is for instance 12000ft (3657m). However as may be news to some, this range too is dynamic, just as TV, IR or radar lock are.

I’ve seen posts (on forum, as bug reports, etc) popping up why their laser guided bombs don’t pick up the laser spot, or otherwise too late. Most of them referring to the in-game max lock range of 3657m. So I am here to clarify this mechanic and hopefully to others who didn’t know yet. From my findings, Gaijin seems to have implemented a curve similar to a NATO published paper on this same subject. The graph they used most likely is this one:

Notably the green line is modelled, so for i=45° (geometry based variable). This paper was made in context with the ItAF Tornado with CLDP pod and (likely) Paveway bombs. As can be seen here is the maximum self designation range of 3657m, which is also the range of the Paveway bombs in game. This means that with a Paveway bomb (and other LGBs that share this same seeker range, there are a number), you can only achieve this maximum seeker range when you are designating from 3657m yourself as well. Of course this is usually way too close for comfort in usual battles, so people tend to designate from further away. As can be seen in the graph, as LTD-tgt (Laser Target Designator to target) range increases, the LGB-tgt (Laser Guided Bomb to target) range decreases. This graph matches up in-game values fairly closely, but seems to break down nearing the extreme ranges. It appears that the in-game LGB-tgt range seems to asymptotically approach the 2000ft mark instead, probably to avoid extrapolation. From this can also be concluded that optimal/maximal useable range of laser guided bombs (of the Paveway variant) is only maybe 10km, for an accurate toss, but preferably less.

Here are various in-game examples, pictures are taken right when the bomb acquires the laser (and switches to TRK mode). Also, no, the laser is always usually inside the FOV of the seeker, the FOV of the GBU-24 is 30°, which is very large as is also apparent from some of the pictures shown. Also note that all of them missed the laser except the one very close one (where it racked from 3km+), the GBU-24 seems to be very bad at maneuvering, especially when given anything less than 3km tracking range.

Spoiler

However, I am also here to tell that most likely these LGB-tgt values are likely too low. The NATO paper assumes almost worst case scenario, 10% laser reflectivity and 100% relative humidity (at 30°). In terms of visibiliy, visibility is usually higher than 10km in-game on a clear weather setup, however for simplication purposes this is understandable due to lack of data otherwise and it seems to matter less for to go to higher visibility judging from the data. I made a more in depth bug report here: Community Bug Reporting System

Additionally: I found some footage that includes an example of bomb lasing from 9nm (16km+) away. Granted, this seems to be from a Sniper XR pod, but in terms of power it shouldn’t be much different from something like Litening.

Spoiler

[tripod2008]

@CalvinAz

it shouldn’t be much different from something like Litening.

Some relevant US Laser designator specs (PAVE Spike, Pave Tack, TRAM, LANTRN, etc.) are covered in ADB121740 (Laser Range Evaluation Guide for Bioenvironmental Engineers)

Paveway Series (Raytheon) overview [2006]

-III series [2003] (Note F-14 mentioned as platform for EGBU (GPS enhanced) series, and Lofting / Shaped profile)

We know what the FoV of various Paveway variants (early -I series uses +/-12.5 degrees, see excerpt below), with a gimbal limit of +/-18, and the -II series assemblies having “an I-FoV 30% larger” and increased detector sensitivity in comparison to the early -I series seeker assemblies, though we do know that the improved Four sector type seeker was later replaced with a digital assembly with later revisions this significantly improved range, though the available variants are probably incorrect for the timeframe of most airframes as only the basic variants of each Series of Paveway are available.

Exerpts

There is also the fact that the basic Paveway I & -II series use Bang-Bang type actuators which is not how they are implemented, where the; -III, -IV, E-GBU, -II Plus all use proportional actuators, and is part of why the kits cost so much more.

The implementation of the Control surface unlock delay of the Paveway series is known to be erroneous, but is dependent on the subvariant implemented as to the correct delay as some variants start the gas generator only after Signal acquisition, instead of shortly after release as is implemented in game, but would not benefit unless LOAL was implemented.

Also since a guided release currently requires Seeker Lock-On Before Launch, range is heavily constrained especially for the -III & -IV / E-GBU series since they should loft at low altitudes and so they do not have their ballistic phase of flight, and the transition to terminal guidance tends to be quite violent due to the increased velocity, and likely large value of angular error at the time of control surfaces unlock wasting significant energy.

The guidance time is also inaccurate at 60 / 90, seconds instead of 70 / 55 for the Paveway -I & -II series respectively, I don’t have a source for the -III or -IV / E-GBU series, but should be similar between themselves, though likely longer as they are intended for increased range from low altitude releases, and so have a lower average velocity and so would take mote time to cover the distance.

[CalvinAz]

@tripod2008

Some relevant US Laser designator specs (PAVE Spike, Pave Tack, TRAM, LANTRN, etc.) are covered in ADB121740 (Laser Range Evaluation Guide for Bioenvironmental Engineers)

Thanks, added that one to my collection.

@tripod2008

and the -II series assemblies having “an I-FoV 30% larger”

Seems to track as from a F-16C manual which states the number to be +/-16°, it also states nominal acquisition ranges, which improved with the same 30%, mentioning a nominal range of 16k feet, so better is expected.

GBU-24 also has an increased overal seeker size, and is said to have improved sensitivity, but I can’t find any details on that. In game it shares the same 12k ft maximum laser acquisition range as other Paveways.

@tripod2008

There is also the fact that the basic Paveway I & -II series use Bang-Bang type actuators which is not how they are implemented

@tripod2008

The implementation of the Control surface unlock delay of the Paveway series is known to be erroneous

Though I would like to see this all fixed, in current laser implementation it would make Paveways completely useless. As I have tested, from 10km designation range, the bomb acquires the laser only at about 1km, which is 3s before impact. If guidance is locked for 3.5s, then the bomb is simply nothing more than a dumb bomb. Even if it would be able to track, bang-bang guidance would not make it hit anywhere close either. So it would need to come hand in hand with improved laser detection ranges.

@tripod2008

Also since a guided release currently requires Seeker Lock-On Before Launch, range is heavily constrained especially for the -III & -IV / E-GBU series

Do you mean in game? GBU-24 currently can guide itself to the SPI (with inertial drift) when you drop the bomb with the laser OFF (or with the auto laser on weapon drop option OFF at least). Though this is also not accurate for the GBU-24 we have, which I think is the GBU-24/B. Since it lacks GPS guidance it should not be able to guide onto the predesignated spot, I guess it is already described in the overview. It decides based on altitude and release angle what sort of preprogrammed path it will take. At low altitudes this can for instance mean it just tries to fly level. In game the seeker also does not perform any scanning. The other mentioned bombs have GPS guidance, as well as improved versions of the GBU-24, I don’t think those would require (laser) seeker lock-on before launch in-game. Technically we already sorta have dual GPS/laser bombs in-game, I think one of the Chinese GB-1000 bomb got its inertial drift lowered to 0 on its IOG recently, acting as GPS guidance.

@tripod2008

The guidance time is also inaccurate at 60 / 90, seconds instead of 70 / 55 for the Paveway -I & -II series respectively

Paveway batterylife is 60s in game, which is not 55 but not that far off. GBU-24 is the one with 90s. I don’t think we have Paveway Is in game.

@tripod2008

I don’t have a source for the -III or -IV / E-GBU series

Perhaps similar to JDAM? JDAM I think in some document was stated to have 200s batterylife or something, though it has 150s in game. GB-1000, which is GPS irl too, gets 105s. No idea where they pulled that number from, perhaps from their magical secret source they won’t share (made up).

[tripod2008]

@CalvinAz

it would make Paveways completely useless.

They really do need a complete overhaul at some point (preferably before they get replaced by L-JDAMs and SDB-I & -II) as systems that are even more complex aren’t that far away.

@CalvinAz

Do you mean in game?
~~
it should not be able to guide onto the predesignated spot

Yes, like the Maverick and some Air to Air missiles the lofting mechanic (shaped trajectory) for the GBU-24/B isn’t quite properly implemented (shaping is accomplished via a G-bias maneuver; some preset defection of Control surfaces for so many seconds to establish precomputed lofting angle, and then controlling Seeker angle of attack / rate of decent until Laser signal is reacquired and then transitioning to terminal homing)

@CalvinAz

I don’t think we have Paveway Is in game.

Its more so that if earlier systems (e.g. B-57G), or mechanics are implemented (e.g. Buddy Laseing), or some airframes limited to a specific timeframe the performance is accurate, though there is a narrow window of ~'68-'80 where they could be seen or exported before being replaced wholesale with the optimized Paveway II series kits, this would only really impact the F-100, A-4, F-5, F-4D & -4E, A-6 & -7 Early, A-10A, etc.

@CalvinAz

JDAM I think in some document was stated to have 200s batterylife or something, though it has 150s in game.

That’s entirely separate, the issue there is which variant of an optional airburst nose fuse was installed since the earlier variants couldn’t reach the ~195 second battery life of a JDAM, this was fixed with a later revision to the fuse I don’t know if @Gunjob has submitted the report since I had errors making it, though the portal at the time.

Report contents

As per the supplied screenshot the in game limit of 150 seconds is incorrect.\

The actual value should be a minimum of about 190-200 seconds.

Though in some configurations that for example, had earlier variants of the DSU-33 (proximity airburst) nose fuse fitted reduced the functional life time of a JDAM to only 60 or 90 seconds for the DSU-33A/A & -33B/A equipt store as can be seen in the first source

"Real time targeting for GPS guided weapons using the on-board systems of the F-14D Super Tomcat " [2000]
https://trace.tennessee.edu/cgi/viewcontent.cgi?article=11072&context=utk_gradthes#page=104

“A single thermal battery, with a specified minimum life of 194 seconds, provides
all electrical power for guidance and control functions after release This battery life
limit defines the maximum time of flight (TOP) of the weapon after release.”

Though, the issue was fixed with the development of the DSU-33C/B which can be referenced in the second source, and aligns with referenced ~190 second battery life.

“The Evolution of the DSU-33 C/B Proximity Sensor, A Success in Customer-Contractor Partnership” [2006]
https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2006/fuze/balk.pdf#page=4

[Gunjob]

Thank you for the reminder, can you try submitting again so I can be less shit at remembering haha.

[tripod2008]

Still giving me an error.

Failed to save issue data: Bad request. [EID: 77f630ecb93f657385c96e96094dfa6b]

[CalvinAz]

@tripod2008

They really do need a complete overhaul at some point (preferably before they get replaced by L-JDAMs and SDB-I & -II) as systems that are even more complex aren’t that far away.

That’s kinda what I fear though, that they just add new toys to the new vehicles which are actually useable and then forget altogether about the old stuff. I have a feeling the issues of the Paveway (and similar seekers found on the Skipper, Lizard, Mk13/18 Paveways, etc), and even to extend the Russian laser bombs (they get 4km max seeker range) will just not get fixed. But at the same time I feel the devs are using it as balancing tool anyway, hence we haven’t gotten any of the more advanced LGBs other than China I suppose (at 6km max laser range, which is at least more useable at range).

@tripod2008

or mechanics are implemented (e.g. Buddy Laseing)

I would like a buddy lasing mechanic, but it has a similar problem as before. Since this would allow the designator to be much closer, the problems in the current laser range implementations wouldn’t be as apparent, making devs just ignore the problem.

[Gunjob]

You tried in another browser? Might be a plugin messing it up.

[tripod2008]

@Gunjob

You tried in another browser?

It’s running in Chrome the same as my prior reports that have gone though.

Similar issue with both Firefox & Brave, its also probably not an issue with uploading .jpeg / .png as I’ve tried both permutations for each of the three files

[EID: 8cb7758d3fe409c2c2ae10e3d4576252]

[EID: 7bc865b59d77f25d3ffe65b235d4e52e]

[Gunjob]

Ohh PNG isn’t supported, try taking all your sources and throw them into a zip file.

[tripod2008]

Is that even mentioned anywhere; it lets me upload them fine, is there a list of which formats are supported?

I’ll try .jpg, not .jpeg this time.

Ok so .jpg files work, I guess I’ll know for the future.

https://community.gaijin.net/issues/p/warthunder/i/eiJ7Wg5ff5uq

[Gunjob]

Forwarded, cheers for persisting in this and for the nudges.

[ex3333]

The battery life of GBU-49/50(EGBU-12/10) is about 180s

[tripod2008]

So that sorts the Raython production variants(e.g. GBU-49/B, EGBU-12), what about the DMLGB series produced by Lockheed (e.g. GBU-12F/B)? They are somewhat similar by not quite the same upgrade kits though an argument could be made that since they both meet the spec for a dual source contract it should be the same.

[ex3333]

Found nothing about it.
Raython got a lot of foreign contracts,so we can get more information from documents of them.

[CalvinAz]

You got anything regarding the MAU-169 CCG, mainly pertaining to the seeker part and laser acquisition ranges/sensitivity? Seems that at least earlier EGBUs used the same CCG as normal Paveway IIs, but I found that more recently they use the MAU-210, though idk if the seeker changed. Gaijin seems to not care anyways though, they gave Elbit’s Lizard LGB the same values as the Paveways in game simply because it looks the same I’m pretty sure.

[ex3333]

according to that document.GBU-49/50 use MAU-210E/B,
and

“The field of
view and field of regard are the same value for the EP2. The (FOV) is 36° (with a +10, -4 degree tolerance)
relative to the velocity vector”

“In-Range guidance restricts the usage of laser guidance until the weapon is within the expected laser acquisition
range (16,000 feet slant-range) of the GPS target coordinate.”

Actually, the only diagram I ever seen about relationship between designator distance and laser acquisition range is in AV-8B tactical manual about AGM-65E and MULE

[CalvinAz]

Hm the 16k feet figure is the same as I’ve seen for the regular Paveway II (in F-16C manual), so likely the seeker hasn’t been changed (much). 16k ft (4876m) is also actually impossible in game, so at least that confirms it as well. What document is this, is it public?

Also the brochure from Raytheon (I think from 2008 or something, also linked above by tripod) mentions MAU-169 for EGBU, but maybe MAU-210 is the actual correct name since MAU-169 doesn’t contain a GPS module unless that for some reason had the same name too).

I supppose a lot of this information is purposely obfuscated due to classification. But if we can just assume 16k ft nominal acquisition range, which is enough for the 8-10s recommended guiding time + the 2-3s control activation delay assuming ~300 m/s or even mach 1 speed for the bomb and a LTD-tgt slant range of usual 7-10km judged from real life footage (probably higher in actual SPAA/SAM contested areas) means that in-game performance is about underperforming by a factor of 2-3x, which can be explained by lower than normal reflection values, higher than average humidity and some other minor factors assumed by the example used by the NATO paper, and thus the devs.

@Gunjob would it be possible to pass this report (listed in main post) to the devs as suggestion for consideration/rework perhaps?

[ex3333]

From EPII manual leaked from Saudi Arabian Airforce, Can’t be use to create any issue apparently.

Its useless insisting on probing this issue, laser designation is a very complex problem, related to laser energy, angle, visibility, reflectivity and a host of other factors, gaijin has no incentive or ability to solve this problem.

The AGM-65E is capable of acquiring laser at 7nm while designator is 8nm away in certain condition,and in game the maximum range is 5nm.

The Paveway IIs got wrong FOV and the the maxium laser acquisition range is 4000ft less than nominal laser acquisition range in manual

Just like manpad thing,they have their own theory,they nerf PAVEWAYIIs to shit,and they don’t care what we think.

[CalvinAz]

@ex3333

laser designation is a very complex problem, related to laser energy, angle, visibility, reflectivity and a host of other factors, gaijin has no incentive or ability to solve this problem.

Well my report doesn’t necessarily want that, since WT seems to already just copy the NATO graph I found, or it’s at least eerily similar, likely not a coincidence. It’s already a huge simplification in that as a host of variables are kept constant this way, but given that was their choice I at least suggest increasing detection ranges by argueing that reflectivity values are too low. Don’t care really as long as the numbers in general go up, since they make up the numbers mostly anyway. Paveway IIs in the past had 7km seeker range, likely being more correct to real life performance than now, not sure if back then they also had the laser range drop-off mechanic in place, or if that happened only after the nerf. Right now Paveways are essentially just useless when used from 10-12km away or more, they don’t have enough time to maneuver unless the drop was already perfect.

@ex3333

Just like manpad thing,they have their own theory,they nerf PAVEWAYIIs to shit,and they don’t care what we think.

I sure hope that isn’t the case, but you’re probably right. Hence why I would really like if it was possible to request reasoning/sources from the developers why things are as they are. Manpads issues got so blown up that they did show us why current implementation is what it is, though I don’t think we will ever get such a post for laser mechanics.