Re: Sensors

Derk Groeneveld wrote:

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> Some very nice ideas here, just one bit where I can't help but
> disagree/cpmment.
>
> On Tue, 29 May 2001, Ryan Gill wrote:
>
> > If we use Radar and Sonar as a reference here for
> > principles. Passive Sonar will give you some general
> > information about the vessel and allow you to get some
> > pretty good ideas of what it could be. It'd be hard to get a
> > specific ID on a specific vessels' hull number with passive
> > sonar.
>
> Actually, as far as id-ing a target is concerned, almost the reverse
is
> true for 'passive radar' (ESM). A good ESM suite, supported by a
> well-filled ESM database, will give you a very solid ID of a target
based
> on the target's emissions. So perhaps sonar isn't as good an example?
In
> any case, I wouldn't be surprised if modern day passive sonar has much
the
> same capabilities?

The nature of shipbuilding makes it impossible for two vessels of the
same
class to be identical, and often minor improvements are worked into the
design
as it is built.  The chaotic nature of turbulence also has a hand here,
so two
nominally identical hulls will have similar, but distinctive flownoises.
Distinguishing between two passive contacts is not that difficult (not
that it
is easy), and a tape library of previous encounters enables the listener
to
identify a specific vessel.  Combine this with some other intelligence
(Sonar
profile SN7 just went into port, and simultaneous pic of the Seawolf),
and
passive sonar can tell you exactly which vessel has been encountered.

ESM will give a list of operating active sensors, this list is much like
a DNA
test, in that it does not tell you which vessel, but does allow you to
rule
some out.  Detecting an active SPY-1 informs you that the blip is an
area air
defence vessel, with SM2-MR missiles, aplenty.	Not detecting an SPY-1
radar