HPRF is completely incapable of detecting a closing contact that is heading away from you.

[MARLAN_]

DCS seems to base the capabilities of HPRF (and I would guess the entire radar implementation) on target aspect, not closure.

To reproduce: Select HPRF, try to detect a contact that is flying away from you, it will be impossible (0% Pd) to detect at any range, any Vc, or any dragging heading.

The direction an object is facing is irrelevant to radar, it doesn't care what side is the "front".

HPRFAspect.trk

Edited April 18, 2024 by MARLAN_
add track

[Solo_Turk]

bignewy may about to come to ask public evidence  issue reported many times with different topics. they said the team  would look after christmas. so, we are waiting for the next patch.

[NineLine]

I am looking for clarification on this. Will update here when I find out.  

[ChaosRifle]

can confirm, is an issue
PDI mode on the hornet does indeed use aspect of bandit instead of closure/separation rate to see if you should get hits, and thus if fox1 guidance should work.

best way to see this: have bandit fly mach 0.5 away from you, have you fly mach 1.0+ towards them. closure of over mach 0.5 but you will never get hits.



as a consequence of this issue, afaik, the doppler radar should also be able to see separation rate, on top of closure rate as well, which is currently impossible due to the implementation of it using aspect instead of closure/separation rate.

[Маэстро]

It's not a bug. In HPRF Pd does not depend on closure rate, but it does depend on target radial velocity (projection of target vlocity on LOS). 

Yes, that may look like it based just on target aspect, but it's not in fact. And yes you cannot detect any cold target in HPRF RWS because it's not designed for this. 

In this mode Doppler filter bank is always placed in clear spectra region, to the right of side lobe clutter + some margin(see speed gate option), so radar can see only closing targets.

[MARLAN_]

6 hours ago, Маэстро said:

It's not a bug. In HPRF Pd does not depend on closure rate, but it does depend on target radial velocity (projection of target vlocity on LOS). 

Yes, that may look like it based just on target aspect, but it's not in fact. And yes you cannot detect any cold target in HPRF RWS because it's not designed for this. 

In this mode Doppler filter bank is always placed in clear spectra region, to the right of side lobe clutter + some margin(see speed gate option), so radar can see only closing targets.

Various different public radar handbooks clearly say that HPRF has worse (not zero) detection against cold targets due to competing with side & main lobe clutter. In addition, and most importantly, Range Gated HPRF (RGHPRF) does not have this problem. RGHPRF has all-aspect capability (comparable to MPRF) but not used at low altitude (<5K) due to high false alarms and shorter detection range than HPRF. The F-18 uses both HPRF and RGHPRF.

[Маэстро]

15 hours ago, MARLAN_ said:

Various different public radar handbooks clearly say that HPRF has worse (not zero) detection against cold targets due to competing with side & main lobe clutter. In addition, and most importantly, Range Gated HPRF (RGHPRF) does not have this problem. RGHPRF has all-aspect capability (comparable to MPRF) but not used at low altitude (<5K) due to high false alarms and shorter detection range than HPRF. The F-18 uses both HPRF and RGHPRF.

1. There is no contradiction with these books. I already told that it is zero because there are no doppler filters placed to part of spectra which contain sidelobe clutter and opening targets. That's how it usually made IRL. There is no rational reason to place filters in sidelobe clutter area if radar has MPRF and INTL mode.

2. RGHPRF does have this problem, it's just less severe. MPRF still better for detection of opening targets.

3. The only practical usage of HPRF against opening targets is MC STT(PDI illumination for Sparrow). But that's different mode and has nothing to do with RWS or VS.

 

[Harlikwin]

On 2/16/2024 at 4:29 PM, ChaosRifle said:

can confirm, is an issue
PDI mode on the hornet does indeed use aspect of bandit instead of closure/separation rate to see if you should get hits, and thus if fox1 guidance should work.

best way to see this: have bandit fly mach 0.5 away from you, have you fly mach 1.0+ towards them. closure of over mach 0.5 but you will never get hits.



as a consequence of this issue, afaik, the doppler radar should also be able to see separation rate, on top of closure rate as well, which is currently impossible due to the implementation of it using aspect instead of closure/separation rate.

I have STT break lock on TU-22's at like 5 miles while I'm trying to guide sparrows on them once they turn/go cold. And I'm under them... That ain't right.

 

[Маэстро]

9 minutes ago, Harlikwin said:

I have STT break lock on TU-22's at like 5 miles while I'm trying to guide sparrows on them once they turn/go cold. And I'm under them... That ain't right.

 

Could you please attach a track?

[Harlikwin]

2 hours ago, Маэстро said:

Could you please attach a track?

It was on an online server so no. But I'm sure you can setup a flight of 4 TU-22's and go shoot at them. 

[NineLine]

If you can supply a track that would be appreciated. it is better to get exactly what you are looking at or seeing from your perspective rather than guess at what you saw. Thanks. 

[opps]

Here it is.

IL-76 flying away at M 0.3, 20000ft. F/A-18 chasing at over M 1.0 at 17000ft.

Commnaded STT, radar tried to go HPRF STT and couldn't hold STT so it changed to MPRF STT automaticaly.

AIM-7 launched, radar switched to HPRF PDI but again couldn't hold track, radar went MPRF PDI (?) and continued to guide missile. Target destroyed.

F-18 radar.trk

[Маэстро]

Thanks, we will see what we can do