reported Radar look down problem - Low flying, fighter size targets not detected from high altitude

[Harker]

In my tracks Vc was just below 1000 knots when the track was lost.

That can't be right then. There's no way the APG-73 wound lose a target with Vc of nearly 1000 kts at 10k ft...

[GGTharos]

On 8/24/2021 at 12:23 PM, BIGNEWY said:

Ive spent time testing it today and it seems to be working as intended,  ( degrades range based on angle. It only reduces range by 0.035 for everyone 1 degree down )

 

I have tested with Tu160 and Mig-29 and have been able to find and lock targets. 

 

Then the intention is bad.  Not too long ago I forwarded to ED the math for determining SNR based on the clutter area.   If I understand the above thing you've posted here @BIGNEWY, for 10 degrees look-down you lose 35% of your range, and you lose 70% of your range for 20 degrees look-down.

 

The range reduction is a function of SNR which is generally a relationship of the viewed area vs the distance of this area from the radar and the distance of the target from the radar.  I haven't tried doing the math do it but I doubt you can distill it to such a nice linear angle relationship.

 

What ED has done here does not represent any real airborne radar that I'm aware of, in fact, every radar document I've seen so far shows us that look-down range is longer than we believe it to be.

 

Please take this back to the team.  Personally I would like to see a proper justification for this (yes, it absolutely should be explained - there are no secrets here, it's just RF physics and I wouldn't mind learning something new) or otherwise my suggestion is to switch to the SNR computation for a far more realistic treatment, or revert to the way it was done before, it's still more realistic than this range reduction per degree thing.   It's still an easy computation, it won't cause any CPUs to overheat or servers to lag.

Edited August 25, 2021 by GGTharos
Fixed my embarrassing math

[BIGNEWY]

21 minutes ago, GGTharos said:

Not too long ago I forwarded to ED the math for determining SNR based on the clutter area.

 

Can you point me to that or share it with me, I will show the team. 

[GGTharos]

18 minutes ago, BIGNEWY said:

 

Can you point me to that or share it with me, I will show the team. 

 

I definitely will, bear with me since I won't have access to my PC for a few hours.   Thanks for the help!

[BIGNEWY]

9 minutes ago, GGTharos said:

 

I definitely will, bear with me since I won't have access to my PC for a few hours.   Thanks for the help!

 

No rush I am always here

[LastRifleRound]

I have this same issue. Even ACM modes struggle picking up targets lower than me

[Svend_Dellepude]

There is a thread in the bugs section started by @Gripes323 now about this. I uploaded some tracks and found that MPRF wouldn't even detect a headon target in lookdown at any range.

 

 

Edited August 25, 2021 by Svend_Dellepude

[...]

My first interactive cockpit module was the Mirage 2000, and its radar picked up low-level targets from 40,000 feet with ease. With the Hornet I have never made it.

[Beamscanner]

A blanket reduction in detection range for look down should only apply to Low and Medium PRF waveforms.. 

 

 

 

Depending on target closure velocity, HPRF could be completely un-effected by look down. 

 

A high Vc look down scenario wouldn't be hindered by clutter at all, bc the ground clutter (main beam, altitude line and side-lobe clutter) is not on the same frequency as the targets reflection.

 

Look down scenarios only effect HPRF with the targets Vc is close to main beam, altitude line and side-lobe clutter doppler freq. (ie if the targets Vc is roughly between zero and ownship speed)

 

 

EDIT: Watch this video starting at 9:15. Notice that when point the antenna down, the ground clutter pops up, but it only exists on a narrow band of velocity (doppler freq). His target doesn't disappear, and the targets SNR doesn't change. If the targets velocity slowed down, it possible that its return could hide in the clutter. But if it slowed down in a look up condition, the clutter wouldn't be there, and the radar could track it through the zero doppler region. This is true for all HPRF waveforms. 

 

 

 

Edited August 31, 2021 by Beamscanner

[BIGNEWY]

Hi all, 

 

we will be tweaking this some more in a future update. 

 

thanks