Anti-Radar Missile Questions

[MBot]

1. When an ARM is launched against a SAM tracking radar, does the launching platform have to be within the narrow tracking beam for the missile to acquire the target? If so I assume that the ARM could also be launched from within the side lobes of the tracking radar. How much would the lower signal strength of the side lobes reduce acquisition range of the ARM seeker? The questions is basically, how important is directional positioning to engage tracking radars?

 

2. Can ARM* be used effectively against shipborne search radars? Since the main beam can only be picked up intermittently due to antenna rotation and the radar can move several meters between each sweep, would an ARM be able to track it? I assume if the missile uses proportional navigation (not sure if this is the case), it should be able to hit a moving search radar. Still the intermittent tracking raises the question of the necessary precision to hit such a small target. Or could the seeker track a search radar from 360° once close enough (side lobes)? Since most US anti-radar missiles have been developed by the Navy, I guess anti-ship operations were a high priority.

 

 

*Let's assume classic missiles like AGM-45, AGM-78 and AGM-88A/B/C without dual seekers.

[GGTharos]

1. When an ARM is launched against a SAM tracking radar, does the launching platform have to be within the narrow tracking beam for the missile to acquire the target? If so I assume that the ARM could also be launched from within the side lobes of the tracking radar. How much would the lower signal strength of the side lobes reduce acquisition range of the ARM seeker? The questions is basically, how important is directional positioning to engage tracking radars?

 

You can calculate that using radio equation, but the real answer is 'it depends' on the antenna design and where the sidelobes are points. Some designs have very weak sidelobes, others not, and the sidelobes themselves may vary in peak power :)

 

2. Can ARM* be used effectively against shipborne search radars? Since the main beam can only be picked up intermittently due to antenna rotation and the radar can move several meters between each sweep, would an ARM be able to track it? I assume if the missile uses proportional navigation (not sure if this is the case), it should be able to hit a moving search radar. Still the intermittent tracking raises the question of the necessary precision to hit such a small target. Or could the seeker track a search radar from 360° once close enough (side lobes)? Since most US anti-radar missiles have been developed by the Navy, I guess anti-ship operations were a high priority.

 

 

*Let's assume classic missiles like AGM-45, AGM-78 and AGM-88A/B/C without dual seekers.

Moving targets are not a problem. A direct hit is not necessary for at least the 88, and I suspect it isn't necessary for the others, either: If you attack radars operating at certain frequencies, you lose pinpoint accuracy, so these missiles are equipped with a fuze. Also works against rotating radar dishes :)

[MBot]

Thanks for your assessment. I think the question of direction is quite interesting, as in sims we usually fire ARMs from any direction. It seems that being at the right place at the right time (being the one or being close to the one that is shot at) was quite important for Wild Weasels in Vietnam.

 

Another point is the introduction of INS to HARM. You read a lot that this gave the missile the capability to hit radars that went silent. I find this very hard to belief. For one it would mean that the small INS in the missile has meter-precision. If this was possible, why then didn't every guided A-G weapon from the 80s on feature exlusive INS guidance? And more important, it would mean that the tiny seeker of the HARM has the capability to pinpoint the position of a radar with utmost precision from miles out. My take on the HARM INS is that it allows the missile to continue fly in the general direction of a radar that went silent, in order to reacquire if it radiates again, or to impact at least some where on the terrain of a SAM battery. Of course the later a radar is shut off, the closer the missile would hit the ground. Any comments on this assessment?

[SFAL]

No emmission no guidence...

The missile would keep flying toward the last position

Western airforces have lets say.... difficulties penetrating areas where mobile SAM systems are deployed.

The soviets learing from the north viatnamese SA-2 deployments reallised that static SAMs are prone to SEAD/DEAD missions. Even if the radar operator turned the radar off or directed the beam toward the ground ARMs would score hits.

This is one of the main reason that tactical SAMs SA-6 and up went mobile.

 

This was a big problem for quite a bit untill the british came up with the ALARM missile.

This weapon will go into a high climb upon loosing track of the source and upen a parachute in order to reaquire the emmiter.

But as always this is countered to some degree by the SA-15. These point defence sams are designed to intercept enemy ordance in flight. Be it bombs or missiles. Its worth mentioning that the Mk III will carry 16 missiles with 4 fire chanels and the ability to fire on the move.

[MBot]

The soviets learing from the north viatnamese SA-2 deployments reallised that static SAMs are prone to SEAD/DEAD missions. Even if the radar operator turned the radar off or directed the beam toward the ground ARMs would score hits

 

I agree that static SAM sites proved vulnerable to attack. This also shows impressively by the performance of the Syrians in 1982, who operated their SA-6 sites as static sites and suffered heavy losses to well planned attacks. But I do not agree that ARM would hit often against a SAMs utilizing the right counter measures.

 

Here is a very interesting text I got from the SimHQ SAM Sim forum, apparently from a Soviet adviser in Vietnam:

 

During this period, from Moscow came absolutely absurd recommendation to Fight "Shrike", by launching our missiles. I remember how some of the experienced gunners very accurately said that the order to shoot at the "Shrike" missile is like forcing gunners to shoot the bombs, not the aircraft.

One time, I still tried to track the "Shrike" after the start, but I saw on the screen only the initial time of his separation from the aircraft. A moment later, "Shrike" disappeared because it's reflecting surface is very small and, continuing his search, we have created the ideal conditions for its homing against our SNR. There we, as always, applying the correct, tested method: turn the antenna on azimuth plane and turn off the high voltage. After 10-15 seconds heard a sharp "clap" - overseas "guest" exploded a mile from us, flopping down into the jungle. So we did every time when the aircraft maneuvered in a particular manner, we see splash that marks the launch on the screen or on the report of the commander of the starting battery (who has been equipped with optical device, determined start "Shrike". Twice we were under fire from 2 "Shrike"-s, but they tried in vain - we are not easy prey.

Our experience in defeating the "Shrike" we tried to transfer to the Vietnamese comrades, but unfortunately, after our departure, they do not always strictly follow our, battle-tested recommendations. As a result, in November 1967, our 41st Division received the "Shrike" in the antenna cab "P". Operators (two men) were seriously injured. But our crews, observing elementary but effective measures to combat the anti-radar missiles had virtually no losses from them.

The strange thing is that those absurd recommendation (tracking and shooting the "Shrike" I met at the HQ anti-aircraft missile battalions after returning from Vietnam. You can only imagine what would have led to their execution in a combat situation.

Soon received a new order of command - during the combat readiness our specialist must leave the position. This meant that the Vietnamese payment received full "good" for independent combat work. We also had to come in August in Hanoi for traveling home.

[schroedi]

 

2. Can ARM* be used effectively against shipborne search radars?

 

 

*Let's assume classic missiles like AGM-45, AGM-78 and AGM-88A/B/C without dual seekers.

 

 

Aren't the passive Radar versions of As-4 Kitchen, As-6 Kingfish and others specificly designed to hit and sink a ship just with the passive radar allocator as guidence?

[MBot]

Aren't the passive Radar versions of As-4 Kitchen, As-6 Kingfish and others specificly designed to hit and sink a ship just with the passive radar allocator as guidence?

 

I am not sure if the passive radar variants of these missiles were intended for use with conventional warheads or just with nuclear warheads.

[GGTharos]

Thanks for your assessment. I think the question of direction is quite interesting, as in sims we usually fire ARMs from any direction. It seems that being at the right place at the right time (being the one or being close to the one that is shot at) was quite important for Wild Weasels in Vietnam.

 

It depends on what you're attacking and what with. Wild Weasels have a specific job - SEAD, literally. If they can destroy the SAM, even better, but generally their goal is to silence the air defense long enough to get strike packages through. Dedicated SAM hunting/destroying missions are a bit of a different deal.

 

Which gets us to ...

 

Another point is the introduction of INS to HARM. You read a lot that this gave the missile the capability to hit radars that went silent. I find this very hard to belief. For one it would mean that the small INS in the missile has meter-precision. If this was possible, why then didn't every guided A-G weapon from the 80s on feature exlusive INS guidance? And more important, it would mean that the tiny seeker of the HARM has the capability to pinpoint the position of a radar with utmost precision from miles out. My take on the HARM INS is that it allows the missile to continue fly in the general direction of a radar that went silent, in order to reacquire if it radiates again, or to impact at least some where on the terrain of a SAM battery. Of course the later a radar is shut off, the closer the missile would hit the ground. Any comments on this assessment?

 

I have seen a graph that basically shows if HARM gets within 7km by the time you shut down the radar, it'll come close enough to fuze on your radar and damage it. Beyond that the CEP increases significantly.

The wavelength of the target radar probably also contributes to the accuracy - the shorter the wavelength, the better the pinpointing. As for INS - yep, drift is based on time and a few other factors. That missile isn't in the air very long, so accuracy of a few meters is probably not out of the question. But you also have to add seeker and other errors to this.

 

The capability of the weapon dictates tactics, too. The AGM-88 can be launched from 80nm away. Older weapons may be more restricted in various ways, but generally you can launch (and keep launching) a volley of missiles towards known location of SAMs - if they 'light up' they are at risk of taking a missile that's looking for them (and that they can't pick up on radar usually, and perhaps they didn't even see the separation from the carrier). For the 88, this is called the 'Pre-briefed' mode. Here INS can do some pretty scary things, even if it isn't accurate enough to hit a target by itself.

[GGTharos]

Western airforces have lets say.... difficulties penetrating areas where mobile SAM systems are deployed.

 

No, they don't.

 

This was a big problem for quite a bit untill the british came up with the ALARM missile.

 

It was a 'big problem' until someone realized they actually need to perform SEAD. It has almost always been the case that initially new SAM systems had good gains, but then are quickly defeated. A given air force needs to be able to generate enough sorties (ie. have enough aircraft) to figure out and overcome a particular defensive system.

 

Certainly losses increase, and effectiveness decreases - that's the role of an IADS. But it has to decrease effectiveness enough to cause defeat, something no IADS has ever accomplished against a determined air force.

 

But as always this is countered to some degree by the SA-15. These point defence sams are designed to intercept enemy ordance in flight. Be it bombs or missiles. Its worth mentioning that the Mk III will carry 16 missiles with 4 fire chanels and the ability to fire on the move.

 

... and then you realize that none of this is actually easy, and requires you to do exactly the things that make you more vulnerable to ARMs.

[MBot]

The figure of 7 km for the HARM is very interesting. It fits in the ballpark I was expecting.

 

I would be interested in a further discussion of the question of attack direction against narrow beam tracking radars. The ALARM with its top-down attack mode, and the HARM in PB mode that will probably also position it at high elevation in a ballistic trajectory, suggest that these missiles can track well outside the main lobe of fire control radars. Or alternatively, these modes are only effective against omnidirectional search radars (which I do not expect). Do we have access to any studies or data to enlighten this question?

[GGTharos]

On that, I can only speculate, so here goes:

 

You're probably familiar with the incident where a PATRIOT radar got stuck with a HARM from an F-16. The F-16 probably used Self-Defense launch mode, operational parameters for PATRIOT are unknown.

 

While PATRIOT CAN engage tactical missiles (an we know this because it is in the testimony regarding the friendly fire incidents), it did not in this case. For this reason, there are many possibilities:

1) After certain friendly fire incidents, crew may not have wanted to engage a 'tactical missile' track.

2) Maybe HARM RCS is flat out too low to track and engage.

 

Getting to your question:

 

We have some differences between PATRIOT and S300 type SAMS. Rather, SA-11 is more comparable to PATRIOT in operation (Single antenna mount for all functions).

 

In this respect, this antenna is tasked with doing TBM or ABM search, so it might be radiating a lot. You can combine it with other radars so that each covers a 'slice of time', thus no radar operates continuously.

 

With S300, you have several radars operating and you probably want to choose which one you're going to attack.

 

Back to sidelobes: Even though these sport a narrow main beam, sidelobes never go away. They are definitely reduced in amplitude in those modern radars, but they're probably very detectable at closer ranges, and PB mode supposedly gets you there.

 

Also: These radars often operate in an SWT mode, so they're still radiating where they can be detected.

 

Finally, 'narrow beam' is an engineering/mathematical term :) There's still plenty of power available for detection around this narrow beam :)

 

Regarding studies - not so much, just historical effectiveness.

[MBot]

To get a perspective in the numbers involved, a while ago I actually counted the number of SAM firing batteries deployed in East Germany ca. 1989.

 

Number of Firing Batteries/Battalions of the East German Air Defence, East German Army Air Defence and Group of Soviet Forces in Germany:

 

SA-2: 34

SA-3: 31

SA-4: 36

SA-5: 6

SA-6: 78

SA-8: 75 (4 independent vehicles each)

SA-10: 2

SA-11: 20

SA-12: 12

 

These forces do not include units of the Polish Army, Czechoslovak Army, Hungarian Army and Soviet 2nd/3rd/4th strategic echelons which might advance through Germany.

 

 

These forces were opposed by the following NATO HARM shooters:

 

52nd Tactical Fighter Wing, Spangdahlem: Mix of 72 F-4G and F-16C without HTS

 

At that time point no ALARM for RAF and no German Tornado ECR. Other F-16 units did not employ HARM to the best of my knowledge. Not included are French SEAD assets and 2 additional USAF F-4G squadrons at George AFB for worldwide deployment. The most significant SEAD force of NATO, the US Navy, is missing here, as it was not intended to be involved at the Central Front in most war plans.

 

If we assume 10 HARM shot for every destroyed SAM battery (which is probably a conservative number considering Desert Storm and Allied Force history), this means each aircraft of the 52nd TFW would need to expend 40 missiles. Those are some pretty hairy numbers :)

[GGTharos]

SEAD relies on ARMs as one part of the action, by no means all of it. Not is it necessary to hard kill everything.

 

And if you were to look at how many of these have been launched in the past, these numbers are not all that surrounding our hairy :-)

[MBot]

SEAD relies on ARMs as one part of the action, by no means all of it. Not is it necessary to hard kill everything.

 

And if you were to look at how many of these have been launched in the past, these numbers are not all that surrounding our hairy :-)

 

Desert Storm is not directly comparable regarding number of missiles expended, because it had the USN actually contributing the majority of HARMs fired. The USN was well prepared for the SEAD mission with all of its strike aircraft having anti-radar capability. But the USN could not be counted upon to be involved in central Europe, it was not its mission. Allied Force is not directly comparable either, because those 750 missiles were expended over 2 months.

 

What I am getting at is that the USAF and European NATO members were not equipped to counter the large number of SAM systems concentrated in such little space. Remember that there is also an important time component. NATO did not have time for a dragged out SEAD campaign, results would have to be achieved in days or be overrun. I do not see that those precious 70 SEAD assets would be able suppress the majority of WP SAMs in Germany within the first few days and survive it. The NATO air forces apparently came to the same conclusion evident by the strike tactics being trained in that time frame.

 

 

Or to word it differently, you should not expect your aircraft to expend 40 missiles average in WWIII :)

Edited March 21, 2015 by MBot

[MBot]

If anyone actually has period Cold War 52nd TFW tactics documentation, I would love to see it. I have been looking for it for quite a while. Other than some superficial F-4G/F-4E and F-4G/F-16C hunter-killer descriptions, I haven't found much.

 

My best guess is that 52nd TFW would have been supporting mostly high priority F-111 and F-16 deep strikes, by penetrating into the rear area together with the strike package at extreme low level, temporary suppressing the batteries covering the strike target and egressing again at low level. No SEAD support for lowly CAS missions :)

Edited March 21, 2015 by MBot

[whiteladder]

1. When an ARM is launched against a SAM tracking radar, does the launching platform have to be within the narrow tracking beam for the missile to acquire the target? If so I assume that the ARM could also be launched from within the side lobes of the tracking radar. How much would the lower signal strength of the side lobes reduce acquisition range of the ARM seeker? The questions is basically, how important is directional positioning to engage tracking radars?

 

2. Can ARM* be used effectively against shipborne search radars? Since the main beam can only be picked up intermittently due to antenna rotation and the radar can move several meters between each sweep, would an ARM be able to track it? I assume if the missile uses proportional navigation (not sure if this is the case), it should be able to hit a moving search radar. Still the intermittent tracking raises the question of the necessary precision to hit such a small target. Or could the seeker track a search radar from 360° once close enough (side lobes)? Since most US anti-radar missiles have been developed by the Navy, I guess anti-ship operations were a high priority.

 

 

*Let's assume classic missiles like AGM-45, AGM-78 and AGM-88A/B/C without dual seekers.

 

Someone has already mentioned the British Alarm, missile and its loiter capability. What I think most people don`t realise it that Alarm was designed to only use the side lobes for guidance. Even in its direct attack mode the missile would fly a high profile to a point above the emitter and then dive straight down vertically, it could not use the main beam for terminal guidance.

 

 

 

 

There were a number of reasons for this, firstly the British wanted the weapon to used by strike aircraft as part of their normal war load, much the same way as they carried Sidewinder for self defence (it wasn`t eventually used in this manner) .

 

This meant the weapon had to be light enough to be carried on a modified Sidewinder launch rail. The main constraint on the weight of the weapon was the size of the warhead, to keep this small the average miss distance of the weapon had to be reduced.

 

They achieved this by homing on the side lobes, this ensure that the Blinking effect caused by the rotation/scanning of the target aerial was eliminated meaning the weapon was able to guide closer to the target. Also the rate of angle change as it approached closer is reduced.

 

It also made the fusing much simpler, Alarm used a database of emitters and what the height of the aerial was above ground level. The fuse was then activated when this height was reached.

 

The other advantage was that naturally most radar systems are design to reject sidelobe returns, so once the missile was above the target there would be no further indication that it was being attacked.

 

Regarding the sidelobe strength it should be remembered that normally a radar signal needs to travel twice the distance of the detected Aircraft. So for example to detect an aircraft at 40 miles the signal has to travel 40 mile to the target and then bouncy back another 40 miles. This means that an aircraft at 80 miles listening passively is getting the same signal strength as the emmiter. In much the same way, although the side lobe strength is usually(although not always) lower than the main beam it only has to be detected on its outward journey and therefore the lower signal strength it not so much of a constraint.

 

Edit: I should point that the main beam was used to triangulate the position of the emitter, Alarm then flew via Inertial Guidance to the attack position. it could be pre programmed with the emitter location before take off and used directly in Loiter mode. It could also be programme to fly through a number of preset way points, effectively visiting know emitters in turn looking for active ones.

 

As an interesting aside the Argentine navy home on British Sidelobe emissions very successfully during the Falklands war, none of their Neptune aircraft were ever detected because of this.

Edited March 23, 2015 by whiteladder