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Radical New Airborne Radar leaves submarines no place to hde.

Forest Green

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Submarines May Have Nowhere To Hide With U.S. Navy Set To Field Radical New Radar​

The U.S. Navy may gain the ability to locate submarines from the air as a radical new radar finally moves into the deployment phase.

The Raytheon AN/APS-154 Advanced Airborne Sensor (AAS) is a giant radar mounted in a pod under the Boeing P-8A Poseidon maritime patrol aircraft. It’s a solid-state ultra-fast electronically-scanned array: unlike the old rotating-dish radar under a dome, it has no moving parts and moves at the speed of digital.
Navy patrol aircraft



The AAS is the rectangular box on the aircraft's belly. In operation it is lowered beneath the ... [+]

Boeing
When in use, a hydraulic arm lowers the pod clear of the aircraft’s engines, giving it a clear 360-degree view of the sea below in all directions. The project came out of the highly classified "black" world, and details are still shadowy. We do know, however, that it can operate in a variety of different modes, from scanning broad areas to shooting a tight beam of energy to take a high-resolution radar snapshot from long range, or tracking multiple moving objects as small as individuals on foot. It provides monochrome images with photograph-like resolution in all weathers, through clouds and in darkness.

The sensor has been in development since 2009 with flight testing since 2014. Operational testing has been budgeted to continue through the current fiscal year. No updates have been issued although this January the Navy announced it was working on maintenance training systems for the AAS, suggesting that they were expecting deployment soon.


Last week Steve Trimble of Aviation Week noted that a seemingly routine press release about a change of commanders at the U.S. naval base at Point Mugu included one fascinating detail – that the outgoing commander had “shepherded the ACAT-ID AAS Radar program through its Milestone 'C' Decision and Operational Test Readiness Review.”

Completing Milestone C means that the AAS is now ready for deployment.


Many commentators have seized on the AAS’ ability to spot, identify and track targets on land, suggesting that it may be able to do this job better than the Air Force’s E-8 Joint STARS intended for the role. The system can not only find targets, but it can also pass coordinates directly via datalink to another aircraft so it can engage the target instantly with a bomb or missile.


However, the real significance of the AAS may lie in the Poseidon’s strategic raison d’etre: anti-submarine warfare.


Radar does not penetrate water, so finding subs from the air is usually a matter of dropping sonar buoys. These have a limited range and even an aircraft as big as the Poseidon – it is essentially a repurposed Boeing 737 airliner — only carries a limited supply. Hence the Navy has long had a great interest in ‘non-acoustic’ methods of finding submarines.


However slowly it travels, an 18,000-ton, 500-foot-long submarine moves a lot of water as it goes, and that generates a wake. On the surface, the wake is invisible to the human eye, lost in the random pattern of the waves. But that does not mean that more subtle sensors cannot pick it out. The challenge is having a sensor with high enough resolution and sufficient data processing capacity to extract the faint signal from the mass of background noise.


Submarine wake patterns



A moving submarine leaves several types of wake which may be detectable in the surface

US Navy
The Navy's Non-Traditional Airborne Anti-Submarine Warfare (ASW) System seeks to do just that, giving the Poseidon a new methods of tracking submarines without new hardware. Instead, it will use “on-board non-expendable technologies including AN/APY-10, MX-25, AESA Radar, SAR, and others” to scan the sea surface from altitudes of up to 60,000 feet for the tell-tale traces of underwater activity, or what the developers call “target/environment interactions.”


Work on wake-tracking goes back decades. Wakes are easiest to detect underwater, and the Russians have fielded a variety of wake trackers known as SOKS on their submarines over the years, with the UK recently following suit. Spotting wakes on the surface though is a far more challenging prospect, one that is likely to involve Deep Learning processes digesting mountains of radar images to find out what a genuine trace looks like. It may not be possible with current hardware. The Chinese have also been busy in this area lately – but so far lack anything as sophisticated as the AAS to carry it out.


Spotting submarine wakes by radar is an ambitious undertaking. If successful though, it would mean that a P-8A Poseidon could rapidly cover tens of thousands of square miles, locating not just anything above the water but anything underneath it. Coupled with suitable software, AAS might leave submarines nowhere to hide — and that really would be disruptive technology.

Submarines May Have Nowhere To Hide With U.S. Navy Set To Field Radical New Radar

The Advanced Airborne Sensor may have sufficient resolution and processing capacity to detect the faint signs of a submarine wake.
 

TomcatViP

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Two remarks:
- severe weather will certainly impair the possibility for the radar to track wakes.
- near monochromatic SAR image have emerged years ago linked to the F-35 radar and I remember the discussion that followed regarding how to explain the presence of body silhouettes.
 
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stealthflanker

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It's an extremely ambitious demand. Reading back on Tom Stefanick's excellent "Strategic anti submarine warfare and naval strategy" One can see what kind of wave height produced by submerged submarine :

This one is for Near-field
Sub Detection-wave.png



This is the Far-Field wave height.
Sub detection-wave-2.png


As one can see the value is extremely small and may not be consistent with typical submarine operation, like. One wont expect for an SSBN in depth of 30 m moving at 20 Knot speed, as this would increase the probability of cavitation, increase of acoustic signature and in area where supertanker could be expected, the submarine could run into risk of collision.
 

Foo Fighter

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I take it they have a limited quantity of AST, they will need to know what the are releasing a weapon on or miss out through a shortage of weapons.
 

zaphd

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I recently read test pilot George Marrett's book "Testing Death", and he described how Hughes tried something similar in the early-mid 70s. The program got canned, but lead to advancements in synthetic aperture radar. Most of it is classified to this day and the book doesn't really go beyond mentioning that they were trying to detect the subs just below the surface. It seems technology has caught up with the vision of the designers of that time.
 

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It could end up being an important tool for detecting submarines very close to the surface - snorkelling or communicating - but it is not going to be a revolutionary capability against slow and deep submarines.
 

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stealthflanker

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Can see people thinking about drones that can be deployed to decoy/disrupt the waves
Or just have the sub to dive deeper.

The wave would practically be nonexistent.
it would be troublesome for country that had a large amount of shallow water on it's coast.

And all they need to do is to go Slower.

If you see the table i provided... you see there is another variable named speed. 5 knots and you have 1 cm height of wave, which i wonder if it's going to be resolvable among the natural sea waves.



It could end up being an important tool for detecting submarines very close to the surface - snorkelling or communicating - but it is not going to be a revolutionary capability against slow and deep submarines.

and one can expect, with advent of new batteries, new AIP. 97-99% of the time the submarine will be underwater. There still have to be many platform needed or need to be very lucky to be near one and able to resolve any internal or kelvin waves they generate.

---------

I'm all in for the non-acoustic submarine detection. But all these methods are basically still hampered by difficulty of separating the real submarine observables to natural phenomenon. Even Magnetic Anomaly Detector is difficult as they need to actually have to be on top of the sub, Considering that MAD "antenna" have no directivity. One cannot do magnetic "monopulse" direction finding yet.


Active Sonar would have better future honestly. Acoustic days might be numbered as advancement in acoustic supression might have arrived at point where the detection range of passive sonar is equivalent to the length of the submarine itself.
 

tinlail

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Can see people thinking about drones that can be deployed to decoy/disrupt the waves
Or just have the sub to dive deeper.

The wave would practically be nonexistent.
it would be troublesome for country that had a large amount of shallow water on it's coast.

And all they need to do is to go Slower.

If you see the table i provided... you see there is another variable named speed. 5 knots and you have 1 cm height of wave, which i wonder if it's going to be resolvable among the natural sea waves.
If subs have to go slower it is an effective system just by existing.
 

stealthflanker

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Can see people thinking about drones that can be deployed to decoy/disrupt the waves
Or just have the sub to dive deeper.

The wave would practically be nonexistent.
it would be troublesome for country that had a large amount of shallow water on it's coast.

And all they need to do is to go Slower.

If you see the table i provided... you see there is another variable named speed. 5 knots and you have 1 cm height of wave, which i wonder if it's going to be resolvable among the natural sea waves.
If subs have to go slower it is an effective system just by existing.
and typical Submarine patrol speed is like 5-10 knots.

are you thinking they will move as fast as typical surface ships ?
 

stealthflanker

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Anyone interested on some of the maths behind these Kelvin and Bernoulli Waves can read this great book by Tom Stefanick.


These are my estimates based on the book, applied on several types of Submarines. As one see in 30 m depth and speed of 20 Knots. The Bernoulli wave are in order of tens of centimeters This wave perhaps detectable by High resolution SAR's. The Kelvin wave however are in smaller order. The biggest offender however is the P-941 Akula or Typhoon class and the Antey (Oscar-II class). Which can have as high as half and near one meter of these waves. It can probably be spotted with the radar. When moving at 20 Knot.

Example-sub-1-20-30.png

Things however started to improve at just 10 meter additional depth

Example-sub-2-40-100.png

The height of the wave is essentially halved. Then in Typical Patrol scenario where diving depth would be 100 m and speed of 10 Knots

Typical Patrol Depth.png

As you see the wave height would be in order of Milimmetre. Even the massive Taifun would only creates 1 cm high Bernoulli Hump. While for kelvin wave..essentially non existent.


The spreadsheet that I use is available in this post. It contain the theory and the one to estimate single submarine and the other sheet contain the above table. Well feel free to play with it or suggest correction.
 

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tinlail

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I am not sure why so much focus is being made on claiming that the waves too small. If you are using a radar system with sufficient resolution, backed with enough computing power to pull the signal out of the noise, then it will work. It should be noted that in addition to the problem of sub depth and speed, you also have angle and distance from plane to sub as limiting factors to make the system fail.

But as I said before, if it causing the subs to move slower, it has reduced their ability to be where they want to be when they want to be there.
I would presume that if this system us that much better than the preceding system, then it will make the detection of a snorkeling sub that much easier.

It doesn't eliminate the effectiveness of subs but it makes life just a little bit harder. My observation about the shallow water of course only apply if the planes are allowed to fly in that area, if the planes are kept away from the coasts then this technology fails to have such an asymmetrical effect.
 

stealthflanker

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I am not sure why so much focus is being made on claiming that the waves too small. If you are using a radar system with sufficient resolution, backed with enough computing power to pull the signal out of the noise, then it will work. It should be noted that in addition to the problem of sub depth and speed, you also have angle and distance from plane to sub as limiting factors to make the system fail.

But as I said before, if it causing the subs to move slower, it has reduced their ability to be where they want to be when they want to be there.
I would presume that if this system us that much better than the preceding system, then it will make the detection of a snorkeling sub that much easier.

It doesn't eliminate the effectiveness of subs but it makes life just a little bit harder. My observation about the shallow water of course only apply if the planes are allowed to fly in that area, if the planes are kept away from the coasts then this technology fails to have such an asymmetrical effect.

Yeah, the question is can you get the resolution in the first place ? Can one differentiate a Milimeter sized kelvin wave from naturally occuring wave, will the wave last long enough before it got diluted by the background.

If the observables are already small from the first place... there is little to no hope it could be properly used for an advantage.
 

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I am not sure why so much focus is being made on claiming that the waves too small. If you are using a radar system with sufficient resolution, backed with enough computing power to pull the signal out of the noise, then it will work. It should be noted that in addition to the problem of sub depth and speed, you also have angle and distance from plane to sub as limiting factors to make the system fail.

But as I said before, if it causing the subs to move slower, it has reduced their ability to be where they want to be when they want to be there.
I would presume that if this system us that much better than the preceding system, then it will make the detection of a snorkeling sub that much easier.

It doesn't eliminate the effectiveness of subs but it makes life just a little bit harder. My observation about the shallow water of course only apply if the planes are allowed to fly in that area, if the planes are kept away from the coasts then this technology fails to have such an asymmetrical effect.

Yeah, the question is can you get the resolution in the first place ? Can one differentiate a Milimeter sized kelvin wave from naturally occuring wave, will the wave last long enough before it got diluted by the background.

If the observables are already small from the first place... there is little to no hope it could be properly used for an advantage.
Are we sure it's RADAR and not LIDAR? Process seems quite similar to using LIDAR to see under tree canopies and detect archeological remains.
 

stealthflanker

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I am not sure why so much focus is being made on claiming that the waves too small. If you are using a radar system with sufficient resolution, backed with enough computing power to pull the signal out of the noise, then it will work. It should be noted that in addition to the problem of sub depth and speed, you also have angle and distance from plane to sub as limiting factors to make the system fail.

But as I said before, if it causing the subs to move slower, it has reduced their ability to be where they want to be when they want to be there.
I would presume that if this system us that much better than the preceding system, then it will make the detection of a snorkeling sub that much easier.

It doesn't eliminate the effectiveness of subs but it makes life just a little bit harder. My observation about the shallow water of course only apply if the planes are allowed to fly in that area, if the planes are kept away from the coasts then this technology fails to have such an asymmetrical effect.

Yeah, the question is can you get the resolution in the first place ? Can one differentiate a Milimeter sized kelvin wave from naturally occuring wave, will the wave last long enough before it got diluted by the background.

If the observables are already small from the first place... there is little to no hope it could be properly used for an advantage.
Are we sure it's RADAR and not LIDAR? Process seems quite similar to using LIDAR to see under tree canopies and detect archeological remains.

and why LIDAR bears the APS designation ? The P in APS-154 there is radar.

Had it been a LIDAR it would be AAQ, ASQ or AAS or even ASS. As JETDS defines

JETDS.png
 

jeffb

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Excellent point. I commented that it may be LIDAR simply because, with the shorter wavelength and existing academic examples of similar applications, it certainly has the resolution to detect the very small differences in wave height that a deep or slow traveling submarine would produce.

But obviously, that's not actually necessary.
 

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