Radars have been achieving significantly higher resolutions than what their gain would suggest since late-WW2. By 1980 the S-300 was capable of differentiating between two aircraft in formation. Scan patterns contribute greatly to resolution.
Naval missile guidance thread - SAM systems
- Thread starter Iron Man
- Start date
You forget the PLAN 054A frigates still use SARH and have even upgraded the illuminators to AESA. The refits of the older destroyers are all using the HHQ-16. Furthermore there is a new variant of the HHQ-16 that has both ARH and SARH guidance with extended range. I expect the 054B to still incorporate these AESA illuminators and upgraded HHQ-16.
You cannot paint a single target with multiple illuminators because each illuminator will have a separate channel and frequency on its own, and a missile will be married to that channel. This means another missile will not home in to this illuminator's emissions and this channel distinction works throughout the whole fleet. This prevents missile A from Ship A to home in on a target already lighted by Ship B. This way this allows you to engage multiple targets without cross interference and confusion. Painting a single target with multiple illuminators are more likely to result in interference, like jamming yourself.
ARH simply preferred for multiple engagement against threat saturation. Another advantage is that you don't need line of sight so you can engage targets below the horizon. The problem of illuminators is their radar horizon are limited by their positional height. So a threat that's flying very low can creep up relatively close to the ship before the curvature of the earth exposes the missile to direct line of sight from the illuminator.
HHQ-9 is definitely command guided by datalink until it's active terminal phase. This allows the main ship radars to track the target and guide the missile until it is close enough to the target to use its own seeker. In the event of a VLO object it should stay on command guidance longer until it gets even closer to the target. It uses C-Band for datalink guidance and that's like 5Ghz Wifi so that's a potentially a very high data transfer rate.
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Indeed. That’s why I made the constraint “Aegis like”.
That’s a good point. Theoretically, if a missile has a multichannel receiver could it work?
Yes. I was wondering why the Spanish navy and the Japanese navy are installing illuminators on their brand new ships. In particular the F110 frigate which will carry only ARH SAMs?
Channels are assigned by the fire control computer before the missile is launched.
I personally believe there are the advantages of SARH as you mentioned in closer ranges so I won't argue on this. I do think the predominant reason for using illuminators is because of the expensive large legacy inventory of missiles you have already amassed, especially with Standards. The active Block IIIC will still take a while to be operational and enter mass production unless someone can update me on its status. Even then it won't be as well tested and debugged as the older missile, possibility of teething issues and it will be likely on a much higher cost, so expect the legacy Standards to carry on for a long while. At the same time there's still plenty of the older ESSM block 1.
For frigates and light destroyers it seems the new standard is to use the ESSM instead of the Standards. Check the Akizuki and Asahi class for example. Maybe they want to have a more distinct difference between the smaller class vs. the larger class. So the choice of using ESSM block 2 over the Standard legacy blocks may not be because of the active seeker but because of this armament positioning between frigates vs. destroyer.
True. But that was achieved through a combination of narrower search beams and improved signal processing.
Modern radars have particularly high resolution in range (fraction of a meter) which is a function of their operating bandwidth or pulse length. Using advanced mono pulse tracking and super resolution techniques they can limit the angular measurement error to less than 1% of their beam width. This allows the main search radar to create a detailed 3D image of the target cluster, discriminate the correct target from decoys and instruct a SARH or IR seeking missile to home to it.
Should change the wording to 'fire control' from 'search'.
Search radars are mainly optimized for range, volume and low observability. Think of radar like paint tools. The search radar is the large paint roller that you do to do vast sweeps of the wall. But if you want to paint a beautiful artwork or graffiti on it, you are going to need brushes of different sizes for finer, higher resolution work. That's the fire control radar. Compared to the SR, the FCR is optimized for fine tracking, angular resolution and target discrimination. The SR works from lower frequencies, which can be VHF, UHF, L-band, but S-band being the most popular. FCR works with higher frequencies, starting with C band, X-band being the most popular, and K-bands for CIWS. The longer the frequency, the greater the range, the shorter the frequency the higher the resolution.
So a modern ship should come with a battery of radars, like a painting artist with an array of tools of different sizes. So if you take a Type 052D, you can breakdown all its radars as follows, along with purpose, starting with the lowest to the highest frequencies.
Type 517A/520 "Knife Rest" or "Fly Swatter" --- VHF radar, broad long range search, VLO detection.
Type 346A "Dragon's Eye" --- S band, long range search, HHQ-9 fire control.
Type 364 "Sea Gull" --- C band, surface search radar, low flying threat detection and tracking. Queues short range defenses.
Type 366 "Mineral" --- X band, surface search and fire control radar, intended for anti-shipping.
Type 344 "Rice Hat" --- X band, gunnery fire control radar.
Type 347G "Rice Bowl" --- K band, CIWS gunnery fire control radar.
All these are placed into a network and there is a central computer managing all of them. So if the search radar finds something, it would pass the coordinates to the fire control radar which would do the fine tracking, and the search radar will continue searching for new threats. With all these radars, the ship is multitasking and managing across a vast swarm of targets. If one breaks the others will still function providing redundancy.
For a Type 054A, the layout is like this:
Type 382 "Sea Eagle" --- S-band main search radar.
Type 364 "Sea Gull" --- C-band surface search radar.
Type 345? "Front Dome" --- X-band target tracker and missile target illuminator.
Type 366 "Mineral" --- X-band fire control radar for antishipping.
Type 347G "Rice Bowl" -- K band radar for CIWS and 76mm gun.
Both ships of course, have non combat navigation radars which are set to X-band. High frequency is used for navigation radars so you can discern tiny boats on the surface. In addition they might have a weather radar and a helicopter approach radar set on the hanger. The Type 055 certainly has one.
The 054A differs from the 052C and 052D is that it uses the 347G instead of the 344 for its gunnery. But this version is one that stands alone, while other copies are placed on top of the CIWS body mount. Likewise, the 056 series frigates also use the 347G for its gunnery control. The use of a CIWS radar guarantees the 76mm gun is also used for anti-air. Ironically the original 054 uses the larger 344 radar which has better range and is more suited for the 100mm main gun it uses. Other ships that use the 90mm or 100mm gun also use the 344, but everything that uses the 76mm gun to below, uses the 347G.
For the 054A, how it works, is that whatever threat is picked up by the 382 and 364 is handed to the defenses, starting with the Front Domes which will track the target for firing with the HQ-16, and then illuminate it for missile guidance. It also passes to the 347G when the target is in engagement range of the guns.
Other ships from different navies have variations of the same theme. For example, the antiship targeting function for antiship missiles, the gunnery function for ships and air, and the missile target illumination, are consolidated into a single radar like the Thales STIR, which has its numerous licensed derivants. It saves a lot of cost and weight, but it does limit your multitasking and multi-target ability and battle redundancy. In other ships, a dedicated surface search radar is omitted, with this function integrated into the main search radar. So that only leaves you with two radars, a main search radar and a main fire control radar. In small ships we can reduce this further since we don't have the luxury of space. In such things like the Tarantul corvettes, you have one Mineral radar that acts as both the search radar, surface search, and antiship radar, plus a smaller radar, like MR321 Bass Tilt to handle the AA tasks. In other ships, EO devices replace the gunnery fire control radar, although in the case of both 054A and 052C/D, EO is still added to augment the gunnery fire control radar.
Indeed, track radar. Thanks.
I had in mind the SPY-6, which is a multi-function radar that combines search and track functionality. Likewise for Type 346.
Radars of that class can command guide a missile almost all the way to target and place it in optimal position for endgame when their SARH or ARH seekers kick in. If the radar has high resolution discrimination capability it can generate a 3D target map to a 2D IIR seeker on a missile, helping the missile avoid decoys or go after the intended target.
I learned that usefulness of a dual SARH/ARH seeker is to preposition the antenna before it switches to ARH. This removes the need for the missile to perform a potentially time consuming scan before it can lock-on target.
Let's not forget the SPY-1.
The problem of a dual SARH-ARH operation with SARH at midphase and ARH at terminal, is that the target aircraft will be alerted early well before the missile reaches the terminal stage. The aircraft RWR will be easily alerted by the guidance illumination, and this is easy to distinguish, namely a continuous wave or high PRF at X-band with high power. The plane will be dumping it's decoys or activating it's jammers or running away. For ARH to succeed it needs to be unnoticed till the final moment it activates it's seeker. Only then will the aircraft's RWR go off but with minimum reaction time left or maybe even too late. The ARH missile must hold off using it's seeker till the last possible moment, and the launcher's radar must guide the missile into this location.
If an aircraft is tracked by a search radar, the RWR will notify the pilot that a search radar is scanning them, by detecting an S-band emission. However an S-band emission does not necessarily mean a missile has been fired, and the aircraft may proceed with its attack, taking a gamble that a missile is fired or not. If a missile is fired it would have to be an ARH as a SARH missile launch would already have alerted the pilot via RWR through an X-band CWI or high PRF beam. The search radar can control the ARH missile while a search and track mode is applied on the target, usually referred to as TWS or Track While Scan. The pilot only knows of the threat when the seeker goes off alerting the RWR.
If the target is a missile, the preposition of the scanner via a SARH to ARH transitions is of benefit unless the missile happens to have a RWR and does evasive maneuvers.
One problem I would add about mechanical illuminators is that they may not gyrate fast enough against an evasive supersonic target due to the mechanical steering. An illuminator using electronic beam steering is far faster and agile. This is why I think radars that target illuminate with electronic beam steering is better way to go than a mechanically steered one. Furthermore, an AESA has the ability to illuminate multiple targets using multiple beams from the same face, a better way to deal with missile saturation.