Tips for using Passive Sonar

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Primarchx
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Joined: Sun Jan 20, 2013 9:29 pm

Tips for using Passive Sonar

Post by Primarchx »

Here are a few tips for using passive sonar in Command. These are my observations as I recall them, so take that with a grain of salt...

Passive sonar is similar in many ways to ESM but the ocean medium through which it travels complicates the issue significantly. Detecting contacts with passive sonar depends on the sensitivity of the unit, the amount of radiated noise by the target, the amount of noise radiated by the sensing unit (usually by fast speed), crew skill and a variety of acoustic and hydrographic factors. Add to this the convergence zone phenomenon where sound form annular rings at increasing distance (sonar set dependent) and it gets even more challenging.

An initial passive sonar detection is often a sharp bearing spike with indeterminate range. The main way you can tell if the contact is 'local', or within the first CZ ring, is when the uncertainty box for the contact originates within that ring. If it begins at the edge of the first CZ ring and radiates outward from there, you are seeing a CZ contact.

Once a contact is made you need to prosecute it. Your goal is to close with the contact and allow your staff to classify and determine its' heading/speed/depth while denying detection of your platform. While your sensors are detecting the contact you'll see it frequently change in size, bearing and range while it's being localized. Once a contact is lost the box begins to grow from its' last location and a timer of last-contact begins.

Generally you only lose a passive contact you are closing with for the following reasons...
- it leaves your passive sonar range (or if tracking a CZ contact it leaves the annular zone of the CZ)
- its' sound signature changes due to a speed, course or depth adjustment on its' behalf
- your receiving conditions change (increase in platform speed, local water conditions, depth, etc)

Example 1: My LA SSN gets a SKUNK contact to the North, inside the CZ ring of the Swiftsure's sonar set. I'm confident the target is close and turn to carefully close at 5kts. As time passes I determine it's a Merchant contact heading West at 15kts. Not long after that I lose contact, because the ship has left my sonar range. I can either elect to speed up to reestablish contact, wait to see if the contact appears in the first CZ or abandon the chase.

Example 2: My LA SSN gets a SKUNK contact to the North, radiating from the first CZ and outward. This is a CZ contact but could be in any of them. My staff are never able to give me much classification info but based on intel I guess that it's heading my way. Not long afterward the contact fades as it leaves the CZ but then shows up later as it comes into primary passive sonar range.

You don't have to just let Command do Target Motion Analysis, either. You can use Reference Points labeled with Time Hacks to get a feel for the contact's heading and speed. Doing this frequently can be a hassle, especially with lots of contacts out there. But it's better than nothing. Doing this with a distant contact will allow you to predict its' position in the future and perform a high-speed interception dash if you judge it worth the risk.
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