[time-nuts] "The GPS navigation is the weakest point,"
Paul.Reeves at uk.thalesgroup.com
Fri Dec 16 03:50:36 EST 2011
I believe one of our research establishments was experimenting with a
multistatic radar system based on cellphone tower transmissions and did a
very good job of tracking one of the first (if not the first...) 'stealth'
aircraft that the US sent over this way. Certain persons were rather annoyed
when they promptly reported the track of the 'untrackable' aircraft on the
internet. I have played with multistatic systems on auroras and it's
remarkable how much data you can get.
Paul Reeves G8GJA
From: Jim Lux [mailto:jimlux at earthlink.net]
Sent: 16 December 2011 01:30
To: time-nuts at febo.com
Subject: Re: [time-nuts] "The GPS navigation is the weakest point,"
On 12/15/11 4:53 PM, Bob Camp wrote:
> Radar bounces off the flat sides very nicely ....
You are right, it does, but it doesn't bounce BACK towards the observer,
which is what you care about. Consider a flat plate at a 45 degree angle
from you. All the radar energy bounces to the side. Turns out that it's
diffraction from the edges of those sides that's the limiting aspect.
The first stealth planes (e.g. F-117) were all flat surfaces because you
could actually calculate the reflections and make sure you didn't
inadvertently create a corner reflector.
This is one reason that bistatic radar (transmitter and receiver in
different places) is interesting. You can detect things that have very low
monostatic radar cross section (RCS). (also, radar transmitters are easy to
shoot at, because they're like a big beacon saying "here I am"... so put out
a bunch of transmitters and one receiver and have the expensive signal
processing and operators at the receiver, which is entirely passive).
Even better, you can use something benign as an illuminator... Many of us
have used a TV station as a passive illuminator for a bistatic radar, using
your analog TV set as the detector.
Later, as computational horsepower increased, they could make nice swoopy
surfaces with low RCS, and what's more to the point, low bistatic RCS.
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