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Active High Frequency sonar installation on Virginia


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#1 Josh

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Posted 04 August 2009 - 1040 AM

I always love to find new little nugets of ASW goodness, since its often very hard to paint any kind of picture of system effectiveness and even the stuff that isn't classified is often burried and obscured, compared to other open sources. I went through Wiki's description of Virginia's sonar suite on a lark (already seen it there before) and found something I'd never noticed or heard of, a reference to a high freq active system mounted in the chin and sail. Further google-foo returns a link describing such an installation on USS Ashville which, I assume, was a test bed for the Virginia system. Of interest is how useful the system seems to be for littoral ops:

http://www.navy.mil/...s_asheville.htm

Emphasis is mine:

"The higher frequency and shorter wave lengths of HF sonar yield greater range and bearing resolution compared to medium frequency systems, and these in turn enable better discrimination between undersea targets and bottom and surface reverberation. In addition to facilitating mine avoidance and active ASW in littoral areas, high range and bearing resolution make possible precise ice canopy and seafloor profiling for under-ice and shallow water navigation and mapping. The increased bandwidth available at higher frequencies and the greater absorption of HF signals in the water allow active operation with reduced counter-detectability, and the large bandwidth available in HF systems can also be used to conduct high data-rate acoustic communications."

[SNIP]

"In the ASW mode, HF active not only detects and tracks actual targets, but also occasionally detects wakes from surface ships and submarines. These wake detections provide not only contact bearing and range, but also an excellent indication of course and speed, all in one ping. Many of the modes use transmissions that are designed to be undetectable to modern acoustic intercept devices, thus maintaining the boat’s inherent stealth while yet improving her sonar capabilities. "ASW is still our meat-and-potatoes mission, and in shallow water against a quiet contact, HFSP has given us the edge," says LT Jack Shriver, Asheville’s Combat Systems Officer. "Passive or active, one whiff on HFSP and he’s a sitting duck."

The profiling mode uses the active reverberation from seafloor features to "paint" a three-dimensional map of the bottom contour ahead of the ship, a feature Asheville first demonstrated during her 1996 WESTPAC deployment. During the 1998 deployment, while operating in poorly charted, extremely shallow waters, Asheville used this real-time data extensively for navigation safety. "Using profile mode is like flying on a clear day, instead of having to use instruments," according to ETC(SS) Larry Wood, Asheville’s Assistant Navigator. "You can see exactly what you’re getting yourself into. Of course, I’ll still hang on to my trusty fathometer, but I can see the wave of the future for littoral navigation." Another rapid turnaround COTS development was a real-time recording system to log profiling data. Developed at the ship’s request just weeks before the 1998 WESTPAC deployment, the recorder electronically tags bottom features with on-board navigation data, so the observations can be used for correcting charts."



While I'm on the subject, Virginia uses some kind of fiber optic sonar system for its flank arrays. I assume they are passive only. They have the term 'wide band' in their name...made me wonder, class of noise or target are flank arrays be used on (as opposed to tail or bow arrays)? There are three installations on each side...does this allow for triangulation of targets detected with this sensor?

http://www.nrl.navy....p?P=04REVIEW177

#2 Archie Pellagio

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Posted 04 August 2009 - 1920 PM

I've seen it mentioned in multiple documentaries on the boats and I'm pretty sure it is in the Dangerous Waters computer game.

Whats the biggie?

#3 Steve Duncan

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Posted 05 August 2009 - 1004 AM

I'm fairly sure that US nuclear subs have had sail mounted HF sonar arrays for quite a while. They are primarily used for mine avoidance and under ice navigation. The chin mounted system may be something new given the littoral emphasis, detecting sea surface obsticals ect.

Flank arrays go back quite a ways too. I think PUFFS (a set of 2 or 3 passive arrays mounted in fins above the submarine hull) was the first American system. France and Germany also had similar flank arrays available in the early 60's. They indeed were used for passive ranging. If I recall correctly the French system operated in the 1-2kHz range with bearing accuracy of 1 to 2 degrees out to around 10,000m (about 5nm). The newer arrays operate over a greater frequency range, and with more sensitive hydrophones and much more computing power. As a wild guess I would think they would offer sub-degree accuracy and ranges out to the first convergance zone (about 30,000m, 15nm).

Edited by Steve Duncan, 05 August 2009 - 1005 AM.


#4 Josh

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Posted 05 August 2009 - 1053 AM

I've seen it mentioned in multiple documentaries on the boats and I'm pretty sure it is in the Dangerous Waters computer game.

Whats the biggie?


Some of us are not as well read as you are, oh wise one :) I've only heard about these boats online and never saw that mentioned before.

I knew about the more typical bow, towed, and flank arrays; just never heard of a high freq set on a sub before. Article read said newer LA's were getting it retrofitted; must have been pretty useful or really cheap.

Side note since I opened this thread up already; why do US boats employ two types of towed arrays? TB-16 and TB-23 IIRC, latter referred to as a 'thin line' array? Are they meant for different environments, frequencies, both?

#5 Gorka L. Martinez-Mezo

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Posted 05 August 2009 - 1736 PM

Flank arrays go back quite a ways too. I think PUFFS (a set of 2 or 3 passive arrays mounted in fins above the submarine hull) was the first American system. France and Germany also had similar flank arrays available in the early 60's. They indeed were used for passive ranging. If I recall correctly the French system operated in the 1-2kHz range with bearing accuracy of 1 to 2 degrees out to around 10,000m (about 5nm). The newer arrays operate over a greater frequency range, and with more sensitive hydrophones and much more computing power. As a wild guess I would think they would offer sub-degree accuracy and ranges out to the first convergance zone (about 30,000m, 15nm).


Flank arrays as mounted in VIRGINIA and other modern subs are far different to these arrays. As you mention, these are passive range finders, using several techiques to try get a range passively. These are still offered as part of integrated sonar suites. Older systems, like PUFFS, DUUX-2 and 5 as well as the German PRS series were unintegrated and had their own console. Modern equivalents are included in newer automated sonar suites like the varios TSM series offered by Thales and the CSU-90/ISUS-90 series offered by Germany.

Modern flank arrays are hidrophone arrays of very large aperture and range. They work like other passive arrays locating and tracking noise sources. In the case of US subs, with three arrays in each side, probably they can also e used as rangefinders.

European systems (Western, no idea about Russians) seems to use a single long array per side. Due to different hidrophone types, German sets are long and thin while French designed systems are planar and looks more like their US brethen.

#6 Special-K

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Posted 05 August 2009 - 2118 PM

Are these the sonar systems the greenies were trying to get banned in US costal waters a few years ago due to their harmful effects on whales or some such?




-K

#7 JOE BRENNAN

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Posted 05 August 2009 - 2157 PM

I knew about the more typical bow, towed, and flank arrays; just never heard of a high freq set on a sub before.

US subs have been fitted with HF mine detecting sonars since 1945. The first operational set was QLA, which allowed subs for the first time to penetrate the Sea of Japan through the minefields in the Strait of Tsushima, rather than through La Perouse Strait which wasn't mined but much narrower and abandoned in 1943 as too dangerous (USS Wahoo was sunk, and recently located, there). There have been several models in between, adding ice detection as a mission as well. They are just referring to the latest ones.

Joe

#8 Gorka L. Martinez-Mezo

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Posted 06 August 2009 - 0124 AM

Are these the sonar systems the greenies were trying to get banned in US costal waters a few years ago due to their harmful effects on whales or some such?
-K


Those problems seems to be related to newer, low frequency, active systems.

#9 Josh

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Posted 06 August 2009 - 0715 AM

Are these the sonar systems the greenies were trying to get banned in US costal waters a few years ago due to their harmful effects on whales or some such?
-K


They generally are against active sonar in any form, but specifically the one that they have made a lot of legal problems for is the low freq active array used in TAGOS-23 and one other ship, I believe. These are SURTASS vessels with very long towed array sleds. I think four are left comissioned; two I believe have a Low Frequency Active hydrophone array that is dipped directly below the vessel and is *loud*. These are the ships the PLAN was recently screwing with ealier this year.

#10 Josh

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Posted 07 August 2009 - 1230 PM

Ok, which one of you went in and redacted the wiki article?:)

It no longer has *any* mention of sonar equipment fitted at all...

<dawns tin foil hat and waits for black helicopters>

#11 Garth

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Posted 07 August 2009 - 2040 PM

The profiling mode uses the active reverberation from seafloor features to "paint" a three-dimensional map of the bottom contour ahead of the ship, a feature Asheville first demonstrated during her 1996 WESTPAC deployment. During the 1998 deployment, while operating in poorly charted, extremely shallow waters, Asheville used this real-time data extensively for navigation safety. "Using profile mode is like flying on a clear day, instead of having to use instruments," according to ETC(SS) Larry Wood, Asheville’s Assistant Navigator. "You can see exactly what you’re getting yourself into. Of course, I’ll still hang on to my trusty fathometer, but I can see the wave of the future for littoral navigation."


I bet the former CO of the USS San Francisco wishes he had one of those ...

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#12 George Newbill

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Posted 07 August 2009 - 2323 PM

The San Fransisco probably does, now.

Funny I just got to play with some civillian HF depth sounders, I really could not make heads or tails out of the return data.

#13 Garth

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Posted 08 August 2009 - 0827 AM

The San Fransisco probably does, now.


You mean the San Honolulu, right?

;)

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#14 Archie Pellagio

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Posted 08 August 2009 - 1814 PM

You mean the San Honolulu, right?

;)

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I've seen mock caps with 'San Franlulu' embroided on them. :)




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