On 12/15/11 2:06 PM, Jim Palfreyman wrote:
Fascinating.
I can picture setting up a bunch of transmitters in the hills to send out
strong GPS-like signals to mimic the real thing. I suppose you could
control those signals to fool the device it is somewhere else. That bit is
very clever - you'd have to adjust the signals taking into account current
positions of all current satellites. Smart bit of work there.
But it would also need incredible timing. Even a few ns out and it wouldn't
work. So how do you set up fantastic timing at different locations of
transmitters throughout a country. Well you've blocked the GPS - so that's
no good.
It would require local atomic clocks (good ones) at each location.
Do they have access to such things? Maybe I'm being naive.
Jim
This would be insanely difficult to do. and hmm.. do you think that the
antenna on the drone is pointing UP (towards the GPS constellation) or
down (towards jammers?). The only people pointing antennas down are
ones experimenting with precision landing systems and pseudolites or
people doing bistatic radar using GPS as illuminators.
As Jim points out you have to time the signals very carefully, and think
about what the jamming signals needs to look like... you have to (very
accurately) know where the victim is (so that you can broadcast your
spoofing signals with the correct timing so that they arrive at the
victim within a fraction of chip.. Let's see now, that UAV is covered
with radar absorbing material, and the shape is such that it probably
has a radar cross section of a few square centimeters. How will you
know where it is accurately enough to generate that spoofing signal
(say, within a meter).
And, of course and it has to start synced with the real GPS signal so it
can pull it off gradually)
Oh, and you need to be able to encrypt the fake GPS signal (assuming
that the UAV is using a P/Y capable receiver).
AND, your "spoof trajectory" has to be carefully designed so that it's
not too different from what the UAVs internal IMU is telling it. After
all, a failure of GPS or IMU is something they design for, so they're
always cross checking (just like human pilots do.. Hey, GPS is
reading 500kts and I'm in a Piper Cherokee... I think the GPS on the blink)
Nope.. UAV engine quits, it goes into "glide to the ground doing the
least damage" mode... UAV ditches in a gravel and sand covered field
(with which much of eastern Iran is covered).
Even LightSquared, idiotic and pernicious as it may be, would have a
hard time bringing down a UAV.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
