Phoenix Tracking Question (notching Missile, vs AWG9)

[OnlyforDCS]

So while I've been waiting to fall asleep at night and thinking about Heatblur's Tomcat a question occured to me that maybe someone lucky enough to develop or test this module might be able to answer.

 

Scenario:

I launch a Phoenix at a co-altitude target closing on us within reasonable launch parameters. (TWS launch) While the missile is closing I drop altitude to get below the target so my RIO (or Jester) can keep illuminating the target without the AWG9 getting notched.

At a certain point the radar commands the missile to go active.

At this point the target gets an active missile RWR warning and commits to a hard right (or left) turn and manages to notch the missile's own radar.

However since we are below the target our own AWG9 keeps illuminating the target and getting a solid track.

 

So my question is what happens next? The missile's radar is notched, however our ownship radar is still illuminating the target. Is it still providing guidance to the missile? Will the missile still recieve guidance from the AWG9 even if it's own radar is notched? Will the missile track, or will it be trashed?

 

Hopefully someone can answer this so I don't have to ponder at it long into the night ;)

Edited February 25, 2019 by OnlyforDCS

[OnlyforDCS]

Ok thinking about it the question can be condensed to this: Can the Phoenix still receive AWG9 guidance even after going active?

[Sealpup]

Ok thinking about it the question can be condensed to this: Can the Phoenix still receive AWG9 guidance even after going active?

 

Yes.

 

If the missile loses lock, it falls back to datalink and/or SARH, depending on which is available. So if you have the target lit up in PD STT and the missile commanded active, if the missile is notched it will still home on the target both from AWG-9 reflection and datalink commands encoded into the radar signal.

So make sure you switch off MLC filtering so the AWG-9 doesn't get notched when you try that little trick.

[OnlyforDCS]

I think I read in the manual that MLC filtering is automatically switched off after one second if the radar dish is in a lookup position.

 

So now for the followup. Does the radar have to be in STT lock for this to work? Or more importantly can the RIO switch from TWS to STT during missile flight if this is not the case?

[Blaze1]

So while I've been waiting to fall asleep at night and thinking about Heatblur's Tomcat a question occured to me that maybe someone lucky enough to develop or test this module might be able to answer.

OnlyforDCS, so we know that Heatblur's F-14 is the last thing you think about before going to sleep, but is the first thing you think of when you wake up and do you dream about it?

[Jabbers_]

Yes.

 

If the missile loses lock, it falls back to datalink and/or SARH, depending on which is available. So if you have the target lit up in PD STT and the missile commanded active, if the missile is notched it will still home on the target both from AWG-9 reflection and datalink commands encoded into the radar signal.

So make sure you switch off MLC filtering so the AWG-9 doesn't get notched when you try that little trick.

 

You are assuming that its implemented that way. I know a lot of how the missiles are implemented rely on ED and not HB. Once the missile goes pitbull im fairly certain HB has no control of it after that, even if it loses track of the target. (I could be wrong but from what I've talked to the devs about, im fairly confident in this assumption)

[OnlyforDCS]

You are assuming that its implemented that way. I know a lot of how the missiles are implemented rely on ED and not HB. Once the missile goes pitbull im fairly certain HB has no control of it after that, even if it loses track of the target. (I could be wrong but from what I've talked to the devs about, im fairly confident in this assumption)

 

Oh man I hope you're wrong about this. Could you possibly try it out and get back to us on that? Pretty please with a cherry on top? ;)

[OnlyforDCS]

OnlyforDCS, so we know that Heatblur's F-14 is the last thing you think about before going to sleep, but is the first thing you think of when you wake up and do you dream about it?

 

Not yet, but Im probably not too far off on that! :megalol:

[Jabbers_]

Oh man I hope you're wrong about this. Could you possibly try it out and get back to us on that? Pretty please with a cherry on top? ;)

 

Its a tough thing to try without a RIO and a real player notching. But let me ask the testers.

[Flamin_Squirrel]

While the missile is closing I drop altitude to get below the target so my RIO (or Jester) can keep illuminating the target without the AWG9 getting notched.

 

While I can't answer your question, I think you may have a bit of a misunderstanding of the shortcoming of the different primary radar modes: Pulse & Pulse Doppler. The following refers to target tracking alone; I'm not sure how mode switching works once a missile is off the rail.

 

Pulse Doppler uses doppler filtering to reduce the effect of ground clutter, but leaves it vulnerable to notching. Pulse mode does not, which means it is less vulnerable to notching, but may lose targets in ground clutter.

 

So in your scenario, getting under the target won't do anything to prevent being notched in and of itself. If the target notched you, you could go into Pulse mode to prevent the notch succeeding. If the target then dived as well, you could lose the target in ground clutter - this is the point at which you would dive to prevent that from happening.

 

I hope I've understood your scenario (and the manual describing these modes for that matter!) and if not, hopefully some food for thought at least. It's a little tricky to understand the practicalities of some of this stuff without being able to try it out.

[OnlyforDCS]

 

So in your scenario, getting under the target won't do anything to prevent being notched in and of itself.

 

It is impossible to notch a radar looking up at a target.

[OnlyforDCS]

Its a tough thing to try without a RIO and a real player notching. But let me ask the testers.

 

I think Jester would be up to the task of keeping one target illuminated, but yeah you would most definitely need another tester to do the notching ;)

[Flamin_Squirrel]

It is impossible to notch a radar looking up at a target.

 

Sorry that's just plain wrong.

 

In pulse doppler mode the AN/AWG-9 uses doppler filters to filter out unwanted returns, enhancing target detection and thus increasing detection range. The pros of this mode being that, as said, targets can be detected at greater ranges, ground returns mostly eliminated and missile guidance commands be sent to AIM-7 and AIM-54 missiles. The AIM-54 both in TWS and STT and the AIM-7 in STT only. The biggest con of this mode being that it is susceptible to notching as a target returning zero relative speed will be filtered out.

[OnlyforDCS]

Sorry that's just plain wrong.

 

No it's not. I don't think you understand what entering the notch is. Relative 0 speed. Relative to what? Relative to the ground returns. A pulse doppler radar looking up at the target can be notched in extreme circumstances depending on how the radar is configured but entering the notch usually means entering the same band of frequencies as the ground returns, effectively having the same radar returns as the ground. A radar looking up doesn't have any ground returns to deal with so basically a target would be able to notch it usually only by matching your speed exactly and turning completely in the opposite direction of the radar beam and even then it's very iffy.

[Flamin_Squirrel]

If you're not going to listen I'm not going to bother explaining. Maybe someone else will.

[OnlyforDCS]

Here is a pretty great thread explaining what notching is and why PD radars in look-down mode are susceptible to notching:

 

https://forums.eagle.ru/showthread.php?t=32393

 

Im not saying it is impossible to notch a PD-radar in look up mode, just that it is extremely hard to do so, in fact I doubt that it is even modeled in DCS.

Edited February 26, 2019 by OnlyforDCS

[OnlyforDCS]

If you're not going to listen I'm not going to bother explaining. Maybe someone else will.

 

Really? Okay :thumbup:

 

Let me explain as simply as possible if not for your benefit, maybe for someone else's:

When you go perpendicular to the radar beam looking down at you your closing speed is identical to the closing speed of the ground underneath you. The radar works by working out doppler shift and in this case (since your closing speed is equal to the ground behind you, or 0 as the manual states) it drops all contacts with this doppler shift, which is equal to the grounds own doppler shift. Think of it as "blending" into the ground, though that analogy is a bit flawed.

 

If the radar is looking UP at you, there is no ground return to filter out, the only thing it sees is the target itself. Moving perpendicular to the sky doesn't really affect the radar, the sky does not produce a doppler shifting return in most cases.

Edited February 26, 2019 by OnlyforDCS

[near_blind]

Here is a pretty great thread explaining what notching is and why only PD radars in look-down mode are susceptible to notching:

 

https://forums.eagle.ru/showthread.php?t=32393

 

Im not saying it is impossible to notch a PD-radar in look up mode, just that it is extremely hard to do so, in fact I doubt that it is even modeled in DCS.

 

The AWG-9 Doppler modes have two filters. You are describing the Main Lobe Clutter (MLC) filter, which removes contacts with a closure rate of +/- 133 knots from the aircraft's ground speed in a look down situation. This is the filter we're generally talking about when we discuss notching.

 

There is a second filter, which is a hardware limitation. PD needs target Doppler shift to function. If a contact is moving at the same velocity (+/- 100 knots) in the same direction as the emitter, there will be no change in rate and thus no Doppler shift. The radar will be unable to see this contact in PD mode regardless of relative altitude, and the aircraft needs to maneuver to create a change in relative closure or use Pulse. Notching isn't really the correct term for this situation. It's impractical to attempt as a defensive tactic, but it is something the F-14 crew needs to keep in mind when working a tail chase.

 

It's all described in the manual

http://www.heatblur.se/F-14Manual/general.html#pulse-doppler-mode

[Flamin_Squirrel]

That's all understood.

 

Is the AWG9 capable of detecting a target with zero doppler shift under any circumference?

In STT in particular, why would the AWG9 need to apply any more filtering to a co-altitude target than one above?

 

I don't know.

 

I see what you're getting at. You may be right, I guess it just depends on how much impact these factors have. It might be difficult to get a definitive answer without knowing more about the AWG9's limitations.

 

Edit:: post in response to OnlyforDCS

Edited February 26, 2019 by Flamin_Squirrel

[OnlyforDCS]

From the manual:

 

Because of the way the radar operates the doppler filters it will have two blind ranges. The main lobe clutter (MLC) region which contains most of the ground returns, those returning with zero groundspeed is one of them and is 266 knots wide, centered around own aircraft groundspeed (133 knots slower and 133 knots faster). This is the reason that the radar can be notched as a target with the same relative groundspeed as the ground will also be filtered out. This is however only true for look-down conditions as when the radar antenna looks up into the sky this filter isn’t necessary and can be turned off. If the MLC switch on the DDD panel is in AUTO the radar will automatically turn off the MLC filter if looking more than 3 degrees above the horizon. It can also be turned off manually by the RIO but if the antenna looks down this can make the displays unusable in RWS and TWS as all of the ground returns will be sent to the computer for tracking. In whichever case, with the MLC filter off, the target cannot notch the AN/AWG-9 if it is above the radar.

 

The second blind "spot" of the radar is what near_blind is talking about. In this case the target is moving away directly away from the emitter (us) (+-100knots) but in my scenario the target is attempting to notch the missile coming down on him, if he tried to do a complete 180 degree turn he would exit the "notch" and the missile would pick him up again.

 

In any case it's irrelevant to the scenario I described, but say the target manages to avoid the missile, & manages to turn perfectly away from us, & manages to hit the exact relative 0 (+-100knots) to us speed. (That last part is especially difficult) Since we are now below him, all we have to do is switch the radar to pulse mode and we would pick him up again. :)

Edited February 26, 2019 by OnlyforDCS

[GGTharos]

They can remove the MLC filter but now you lose most chaff discrimination. I'm sure the track can be maintained manually, but there must be some reason why such capabilities are gone now.

As for blind speeds, there are ways to deal with those, too.

[OnlyforDCS]

They can remove the MLC filter but now you lose most chaff discrimination. I'm sure the track can be maintained manually, but there must be some reason why such capabilities are gone now.

As for blind speeds, there are ways to deal with those, too.

 

Ggtharos do you have any idea if the Phoenix will continue to guide to the target in the scenario I described above? I mean im DCS, not in real life. You have more knowledge about DCS missiles and radars than most here. Does it depend on Heatblur's implementation of the radar missile interaction or is that something they have no control over?

[Jabbers_]

Oh man I hope you're wrong about this. Could you possibly try it out and get back to us on that? Pretty please with a cherry on top? ;)

 

Unfortunately I'm not wrong about this, HB simply does not have control of the missile once it leaves the rail. The API does not currently allow HB to do this.

[OnlyforDCS]

Unfortunately I'm not wrong about this, HB simply does not have control of the missile once it leaves the rail. The API does not currently allow HB to do this.

 

Ok thanks for the reply Jabbs. So there we have it. It looks like the Phoenix/Tomcat combo will definitely not be as potent as it could have been in real life. Thanks Eagle Dynamics :(

 

This begs the question of lofting as well I guess. Please don't tell me the missile will loft every single time, regardless of shooting parameters?

[Naquaii]

The missile lofts based on distance to target, ED recently helped us get access to control loft and if the seekerhead is in active or semi-active.

 

In regards to the more advanced seekerhead functions like the one you initially described, we'd very much like to implement those and likely will in the future with help from ED.

 

In regards to the MLC you are indeed correct in that it's very hard to notch the AWG-9 in a look-up situation, the only hard filter is, like mentioned, the zero doppler filter +/- 100 knots from own aircraft speed (heading away from own aircraft) as this makes the relative closure rate around 0.