SCXIIC:solving out the bearing ambiguity in towed array narrowband

[Stanny]

Hello all captains,

Maybe anyone will give me a hand,and a piece of advice in such situation.Seawolf's TB-29 port towed array is showing nothing in broadband,but narrowband at 50 Hz tonal is picking out Akula class sub at two different bearings.

How could I distinguish which one of those narrowband towed array bearings is an ambiguous bearing?The task is complicated as I cannot have both 50 Hz lines on display at one time,so I cannot see,which one of them is changing it's bearing,getting darker,or getting different elseway while the Seawolf is completing a turn in order to solve out the ambiguity.

How do you usually deal with such weak towed array contacts when solving out the bearing ambiguity?

Best regards,
Stan.

[sonar732]

I would go ahead and mark both of them. Find out which layer the unknown sub is in and go to the opposite. Launch a UUV from the opposite layer and make the depth of the UUV on the same side as your questionable contact. If the UUV can't pick it up yet, do a course change and the drop the wrong one.

[Stanny]

Originally Posted by sonar732

I would go ahead and mark both of them. Find out which layer the unknown sub is in and go to the opposite. Launch a UUV from the opposite layer and make the depth of the UUV on the same side as your questionable contact. If the UUV can't pick it up yet, do a course change and the drop the wrong one.

Thanks,sonar732.I will give it a try.Actually,I have never used an UUV yet.

[Stanny]

You were right,as always,sonar732.

I marked both contacts in narrowband,designated S01 and S02.Classified them as Akulas and launched an UUV towards S02.The UUV detected no contacts at the bearing of S02 and I dropped it off.

Then,I calculated a TMA solution for S01,preset one MK-48 ADCAP for active homing,other for passive and launched both from the range of approximately 7000 yards.I was greatly surprised when one of those torpedoes hit and sank a Victor-III sub!There was a Victor-III,although narrowband identified 50 Hz signature as that of Akula-I.

Here is a screenshot showing that Victor-III was a bit far away from original narrowband S01 contact.



That under ice mission of Seawolf's campaign is unbelievable.There are several different subs,and you get different kills each time you play it.

[sonar732]

You actually didn't do it the way I was intending.

For instance, just because you couldn't get a contact off of the UUV doesn't mean that he wasn't there. As evident by the light 50hz tonal, he was going slow...that's why the UUV didn't pick him up...granted, the distance didn't help the UUV either. Keep the UUV going until it runs out of gas. Shoot...with the Seawolf, I've seen players have 2 UUV's going to get a great TMA reading. In your situation, I would've sent one on the course of each of the mirrored contact bearings. Sooner or later you would've came up with something.

Also, just because you have a 50hz tonal doesn't mean you've got an Akula-I. IIRC, the Akula-I is defaulted as the first selection in classification. All non-American subs have the 50hz tonal. Have the frequency range set for 100hz first, then expand to gain a better understanding of which class it is.

[Stanny]

I agree,that might be more likely a lucky shot,than result of contact analysis.But I have tracked the UUV without cutting the wire almost until the false contact,closed the torpedo tube muzzle door only after I lost UUV both from navigation and target screens.There was no other UUV in weapon stores for this mission,only one was on board.

[sonar732]

Originally Posted by Stanny

I agree,that might be more likely a lucky shot,than result of contact analysis.But I have tracked the UUV without cutting the wire almost until the false contact,closed the torpedo tube muzzle door only after I lost UUV both from navigation and target screens.There was no other UUV in weapon stores for this mission,only one was on board.

With the Seawolf, you have a major decision on your hands from the briefing. Each time that you select a mission, look deep into it. Will I even need TASM's or TLAM's?

Place one UUV in tubes 7 & 8, then add another one in the stores. This will give you 4 total. My Seawolf ASW configuration is 6 tubes dedicated to MK 48 ADCAP's with 28 in the stores, 10 TASM and TLAM each in stores, and 2 UUV in tubes 7 & 8 with 2 more in stores.

You might find something more towards your style of play regarding how many TASM and TLAM's you have in your stores. For me, the TASM is more for play since a. They're no longer in the US Navy inventory and b. It's nice to watch a TASM complete the coup de grace thru the scope.

[Stanny]

Thanks for advice,sonar732.My typical loadout for Seawolf is that one with emphasis on MK-48 ADCAP torpedoes (all tubes are pre-loaded with them).However,this time I have had to unload the tube during mission and reload it with only UUV.TASMs and TLAMs as well as all other gear are in stores.

I never use TASMs against surface ships,actually,as every Tomahawk is usually met with heavy barrage of anti-aircraft fire.So,MK-48 ADCAP is my weapon of choice for antisubmarine or antiship missions.

[sonar732]

Originally Posted by Stanny

Thanks for advice,sonar732.My typical loadout for Seawolf is that one with emphasis on MK-48 ADCAP torpedoes (all tubes are pre-loaded with them).However,this time I have had to unload the tube during mission and reload it with only UUV.TASMs and TLAMs as well as all other gear are in stores.

I never use TASMs against surface ships,actually,as every Tomahawk is usually met with heavy barrage of anti-aircraft fire.So,MK-48 ADCAP is my weapon of choice for antisubmarine or antiship missions.

You don't have to wait until you start the mission to change your tube layout. When you see the 3 torpedo's, x, and arrow before the mission start, click on the torpedo's and change your 7 & 8 tubes to UUV.

[Stanny]

Originally Posted by sonar732

You don't have to wait until you start the mission to change your tube layout. When you see the 3 torpedo's, x, and arrow before the mission start, click on the torpedo's and change your 7 & 8 tubes to UUV.

Yes,I know that.I am always a bit greedy to those MK-48s,trying to take them as much as possible along.

[Pisces]

To answer the initial question on solving the bearing ambiguity: 'Wag your tail'

Sorry guys, a layer is not going to differentiate between two bearings. If you change depth the sound on both directions are going to disappear simultaneously. Because it is the same sound. It's just that the TA sensor can't tell the difference between left and right. I know, it sounds stupid with all that modern technology. But it is just the physics/math of it. And a uuv solution is way to expensive resource wise.

Turn to a different course (a couple of tens of degrees to show it good) and see the mirror 'not real' contact shift in bearing twice as much as the course change (eventually). Since the angle between your tail (TA) and the true contact changes, the angle to the mirror contact must match (on the other side) after the turn. Which causes the sound to appear from a different direction twice as far.

This link shows a picture why it can't tell left from right (about 80% of the page down):

http://www.fas.org/man/dod-101/navy/...ys/asw_sys.htm

[sonar732]

Originally Posted by Pisces

To answer the initial question on solving the bearing ambiguity: 'Wag your tail'

Sorry guys, a layer is not going to differentiate between two bearings. If you change depth the sound on both directions are going to disappear simultaneously. Because it is the same sound. It's just that the TA sensor can't tell the difference between left and right. I know, it sounds stupid with all that modern technology. But it is just the physics/math of it. And a uuv solution is way to expensive resource wise.

Stanny actually mentions a course change.

My layer change tactic is to hide you launching a UUV from the contact. If he would've launched the UUV in the same layer, he probably would've tipped off the AI depending on the SSP. Stanny's history in sonar questions show that he's learning on the fly and doing a good job at it.

[Pisces]

Allright, I missed that part about his course change then. Also I'm sorry if I sounded a little tough. Bad excuse, but it was getting late. Anyway, I think he is getting confused on what the narrow band suite is showing him.

The top window shows frequency(horizontal) versus time(vertical) of only one bearing out of 360 degrees. This bearing is selected by clicking and moving the cursor in the bottom window. That one shows signal level(vertical) versus bearing(horizontal). As long as the cursor in the bottom windows stay put the top window can't show sound from other directions. The middle window is only showing what the sound ID database thinks it hears. You can ignore that for now if you only have 1 or 2 lines. On the bottom window only loud contact stand out as a peak. You won't notice silent subs in that wobbly noisy graph. But they are there. You do scan a bearing in it, but only look for evidence of a contact by looking for lines in the frequency window. Those are not going to wave left or right, just fade-in or -out. When he found a 50hz signal on one bearing there should also be a 50 hz sound on a bearing that is "2xCourse - target bearing" (maybe need to correct by subtracting/adding 360 deg) So if he's on course 38 and detects a contact on true bearing 178, the other signal is on 2x38-178=76-178=-102=258. Both bearings are equal distances to your course or TA direction. If you confirm there is a contact on 258 you write both down, or assign a tracker to each. I preffer the former, as there are only so many trackers you can assign (4), and paper is cheap. But assigning a tracker is best if you are learning, because you can see it happen on the map. Make sure you turn OFF auto-TMA before doing this, or that crew member will take away the fun.

Now, do the turn (let's say 30 degrees, and atleast some 4 minutes after assigning the trackers because they need to average out or something) and wait until the TA is straigtened and has been towed past the turn end point. (this can take a long while if you are slow, do not extend the TA fully, a 3rd is enough most of the time) Then try those bearings again. Which one stayed put? (within a few degrees, as it may move on it's own if the turn and straightening took a long while) That is the true contact. Which one isn't there any more, that one is likely the mirror/fake contact.

[Stanny]

Actually,there are such situations when both contacts are changing their bearings (shifting) after you complete a turn of the ownship.

I tried out making such resolution turns while looking at TA narrowband waterfall displays.The only difference you can notice between two equal contacts is that one is shifting more degrees than another.For example,one was assigned at 255 and shifted to 259,other was assigned to 166 and shifted to 163.There is a difference 4 Vs. 3 between the change of both contact bearings,and I think that contact that shifts less is a true bearing.

We do not have such a clear picture of what is going on in narrowband,unlike broadband where there are two visible lines on waterfall displays.We can only use tracker review button in order to see what happened to each contact,whether it changed it's bearing or not.

[sonar732]

Originally Posted by Stanny

Actually,there are such situations when both contacts are changing their bearings (shifting) after you complete a turn of the ownship.

I tried out making such resolution turns while looking at TA narrowband waterfall displays.The only difference you can notice between two equal contacts is that one is shifting more degrees than another.For example,one was assigned at 255 and shifted to 259,other was assigned to 166 and shifted to 163.There is a difference 4 Vs. 3 between the change of both contact bearings,and I think that contact that shifts less is a true bearing.

We do not have such a clear picture of what is going on in narrowband,unlike broadband where there are two visible lines on waterfall displays.We can only use tracker review button in order to see what happened to each contact,whether it changed it's bearing or not.

Hence why the use of UUV's is crucial to keep track of the contacts.