Matthew Kaufman wrote:
On 10/8/2010 10:44 AM, J. Forster wrote:
KISS. This seems like a lot of work for not particularily good results.
I think the point is that the results are amazingly better than the
alternative if the medium-orbit GPS sats are all destroyed and/or
there's jamming coming from all over the sky.
What bothers me is that I haven't figured out yet how the WAAS satellite
configuration itself isn't usable as a wide-area GPS jammer. It is just
a bent-pipe transponder down from 6 GHz or so to L1, so if you can
overpower the uplink with spoofed data that interferes with reception of
the other satellites *and* jam the C&C channels that would be used to
shut the transponder off, you're able to jam a whole continent at once.
Most spacecraft have a "command loss timer" that would shut off the
transmitter in the event that a valid command isn't received every so
often, in case the transmitter is malfunctioning and jamming the uplink.
I'm sure this must have been considered before deployment, but I can't
find any references to the countermeasure(s).
Maybe because WAAS is basically a civilian use system to do precision
approaches?
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