Re: FT Stealth

Phillip Pournelle wrote:

>     FCS are a very different beast than a sensor.  A FCS is a pencil
beam
> focussing a LOT of power on a single target.	A Search system is
sending
> that energy out over a very large area.  Physically/Mechanically they
are
> very different.

But as everybody is going for Phased Arrays, with smart power
management, this may well change.

Basically, with a search radar, you want a long dwell time, and a broad
beamwidth, to maximise the chance of getting a return high enough above
background to be significant. So out of 10-20 "paints" or pulses, you
might get 6-7, vs a background of 2-3. Since we're talking about EM
sensors, the speed of light is actually quite a limiting factor: you
want  to put out maybe 10 pulses over 1/100 of a second, which means
your range is limited to 3x10e5/2 metres if you want time enough for
each pulse to go out and come back before the next is sent.
Using pulse compression, and pulse frequency variation can help, but
jitter the PRF (ie change the tinme delay between pulses) and it gets
worse.

With a FC radar, you need a very high power (to burn through jamming at
its stongest point), and more particularly, a high degree of accuracy,
typically on the order of cm. FC radars are typically thin pencil beams,
and get a new measurement 10-100 times a second of the target's
position.

I'm simplifying outrageously, but suffice to say that with a phased
array, it's possible to radiate both types of scan simultaneously, and
adapt the power transmitted as circumstances change.
   
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