[time-nuts] GPS backup for the stationary time and frequencyuser

[Magnus Danielson]

On 10/08/2010 08:07 PM, 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.
>
> I'm sure this must have been considered before deployment, but I can't
> find any references to the countermeasure(s).

I would not be supprised if they had not considered such a threat.

This is a common threat for all bent-pipe birds. They have been jammed 
before and we can expect them to be jammed again. However, I do not 
think the WAAS or any similar is highest up on the target list as for 
most uses it is a support-function rather than main function system.
Birds which has been jammed is typically TV signal relays.

Cheers,
Magnus