[time-nuts] Speaking of Costas loops (WAAS)

[David I. Emery]

On Wed, Jul 10, 2013 at 07:40:50PM -0400, David I. Emery wrote:
> 
> 	But if the satellite radiates what a local GPS package would and
> transmits ephmerides defining  its position and motion it could be
> included in a GPS solution and could be used for timing and frequency
> purposes the same as any other GPS satellite subject to whatever degree
> of relative accuracy the bent pipe clock obtains and the degree to which
> the ephemerides in the format transmitted allow an accurate position to
> be determined.
> 
> 	And from what I have read it seems very likely the WAAS birds 
> meet these criteria..

	Thinking some more about the bent pipe repeater aspect of
WAAS, aside from allowing any kind of WAAS like signal someone might
invent in the future to be retrofitted to existing satellites without
a long replacement cycle and expensive launches being involved - there
are some interesting properties of the design.

	One is that one COULD bury in the WAAS uplink cryptographic
(eg essentially random to users not in possession of the key) spreading
sequence transmissions that would be radiated globally and could be
received with "unique" GPS hardware... such a covert channel in civilian
GPS could have various purposes... and would look rather noise like
to the rest of the world.


-- 
  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."