AWG-9 PD surface search feasibility

[Golo]

@NaquaiiI started this topic as a continuation of a discussion we had about PD surface search. I didnt want to go so OT in that thread, but I at least think it should be looked at more.

 

I did some further testing of a AWG-9 PD surface search feasibility. I acknowledge that AWG-9 wasnt designed in with such capacity and wasnt used as such, but I only care about what it actually can do not what it was designed to do. I also note that my understanding of radar function is just basic, I dont want to go into technical stuff, just look at it from logical and critical thinking standpoint.

 

So, you said: "The difference is that in pulse doppler all surface/ground returns show up in the same rate location meaning that it should be much harder to see the ships. Currently there likely is too little clutter from water modelled but even if we increase it it would make much less difference in pulse than in PD, again becase it would all show up at the same rate. PD just shouldn't be good at looking at ground/surface targets and locking them in PD-STT should be nearly impossible due to the fact that the STT would not know what returns to focus on.

My current thinking is to disable the ability for STT in PD against ground/surface targets as that shouldn't be a thing but in the end we might have a look at changing how the clutter looks at sea"     

 

Lets look at that. Im not going to argue about intensity of sea clutter since I have no experience with it, in my opinion it should be distinctly lower than returns from actual target, but for a sake of argument lets say its the same (as shown in my test futher).

 

Im more interested in what you said here "all surface/ground returns show up in the same rate location". That is only true for sea clutter/stationary targets/or targets at speed but perpendicular to the radar. Then yes they would fall into the clutter band and would be indistinguishable from it. But any surface target at speed with its velocity vector pointing to/from the radar to certain offset would in fact fall out of the clutter band and could be easily identifiable (as shown in fig. 2).

 

Speeds at which I was able to pick up targets from clutter is somewhere above 20knots difference to ownship (but, it is the fact that I knew what I was looking for). Anything around 30 knots difference is easily distinguishable, and anything above that (speedboats) Is just screaming Im here.

 

Furthermore, I was able to easily lock the speedboats at 57knots even in heavy clutter I simulated by stationary ships (as shown in fig. 1). Confirmation if its actual target is made by referencing the target speed on TID which showed 57. Now I dont think it should be impossible to get PD STT lock on surface targets. When in DDD RDR mode, locking such fast moving surface contact, my range (velocity) gates were outside clutter band, so I dont see how it would present any problems to lock.

 

Now, I didnt think about it and test it to turn F-14 into anti-ship platform. It really is of a questionable use, as it only works in perfect conditions that you cant expect to find during majority of times you would try to use it, but I think it is an interesting capability of a AWG-9 system. The surface clutter modeling should definitely be there, making your modelling of DCS AWG-9 even better, but if there isnt any technical radar stuff that would prevent it to operate like this, Im categorically against disabiling this capability just because it wasnt used like this.   

 

 

Fig. 1 - Ship without waypoints are stationary to simulate surface clutter, Ships with waypoints are moving at 27knots, 2 speedboats in the middle are moving at 57knots

  Fig. 2 - DDD image in PD search, As you can see you can clearly identify targets outside the clutter band in PD with MLC fitler off.

Fig. 3 - Here I locked the speedboat moving toward me (north one at F10 map) at 57knots.

Edit: Not sure why I posted it in bug section, but I guess no surface clutter could be considered a bug, so there.

Edited July 18, 2021 by Golo

[Naquaii]

The issue is that we don't really model sea-clutter at all currently. IRL this shouldn't be possible, it's as simple as that. Disabling PD-STT against ships would be a stopgap until we have clutter modelled.

 

The problem with clutter in pulse doppler is that, like I mentioned, it groups it in regards to rate, not range like in pulse search. And additionally it's also more sensitive to clutter than pulse, there's a reason for pulse-doppler being the best mode for early detection of targets, not pulse, it's simply more sensitive. You're attempt at simulation of clutter simply isn't a very good approximation of it, you need to imagine what you get in your mission but as a wider and fuzzier arc across the whole of the DDD. There's a reason for the MLC being +/-133 knots.

 

This imagine from the manual shows the MLC trace but is just representative, on a real display it would be wider, covering much more of the MLC region.

 

So no, unfortunately my answer will still be the same, IRL the radar would not be able to discern these targets in a way that would allow for detection in anything approachin a reliable way. The reason we didn't catch this until now is just that it didn't really cross our minds to be honest. Use pulse search and p-stt instead, those will continue to work and is also realistic.

[Golo]

1 hour ago, Naquaii said:

This imagine from the manual shows the MLC trace but is just representative, on a real display it would be wider, covering much more of the MLC region.

Ok, this is what I dont understand. What is the reason behind surface clutter being so wide as to cover such a wide area? Is it from a wave speed? I think not. I will assume sea state with strong wind at about 25 knots, wave height about 4 m, with peak wave period of 5 seconds. That should give a wave velocity of about 4 knots (phase velocity around 8 knots). If radar is seeing that it should still fit in a narrow clutter band.

 

Why exactly would PD radar mode with MLC off have such a hard time to group it in its rate band, and would spread it across the MLC range? If I turn MLC off to track airborne targets (even a beaming once with very low/no closure) it has no trouble whatsoever to rate group it. 

 

Also same thing about PD search with MLC off over land. There is again just a narrow clutter band, its given that land does not move at all, but if surface clutter should be spread out in rate, shouldnt ground clutter also behave same?

 

Consider this discussion just academic, I dont really have any wish to engage surface targets in PD, im just interested in that radar function. Sorry to be such bother : ). And if it makes radar behave better (more correctly), then all the better.  

Edited July 18, 2021 by Golo

[Naquaii]

8 minutes ago, Golo said:

Ok, this is what I dont understand. What is the reason behind surface clutter being so wide as to cover such a wide area? Is it from a wave speed? I think not. I will assume sea state with strong wind at about 25 knots, wave height about 4 m, with peak wave period of 5 seconds. That should give a wave velocity of about 4 knots (phase velocity around 8 knots). If radar is seeing that it should still fit in a narrow clutter band.

 

Why exactly would PD radar mode with MLC off have such a hard time to group it in its rate band, and would spread it across the MLC range? If I turn MLC off to track airborne targets (even a beaming once with very low/no closure) it has no trouble whatsoever to rate group it. 

 

Also same thing about PD search with MLC off over land. There is again just a narrow clutter band, its given that land does not move at all, but if surface clutter should be spread out in rate, shouldnt ground clutter also behave same?

 

Consider this discussion just academic, I dont really have any wish to engage surface targets in PD, im just interested in that radar function. Sorry to be such bother : ). And if it makes radar behave better (more correctly), then all the better.  

 

 

The problem is that the clutter returns you get from the ground or surface won't be that exact. If you think about it, why would they then make the MLC filter 266 knots wide? Like you say, the clutter returns will originate from objects at those speeds but they will not be read that exactly by the AWG-9. The MLC filter width was set for a reason, they could've made the filter itself smaller if they wanted to.