AAWSAP DIRD, High-Frequency Gravitational Wave Communications, April 2010

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of the ground stations, shown in Figure 18 where their latitude and longitude are given
in parentheses.
Figure 18. A Proposed Near-Earth Distribution of Frequency Time Standard
The large transmitter ground stations would provide the signals used as both the
frequency and time standards. All FTS ground stations would be synchronized such that
they emit signals exactly in phase with each other, all tied to a common frequency time
source, such as the US Naval Observatory. Each station would use a different frequency
such that the remote terminal (RT) user set could easily differentiate signals, and any
phase or time difference observed would be due to either the relative position of the
remote terminal with respect to each ground station, or the relative velocity of the
remote terminal with respect to each ground station. Each ground station would
transmit both a carrier wave (CW) signal for a frequency reference and a periodic pulse
signal (PPS) for a time reference. At least 3 ground stations would be needed for self­
triangulation by the remote terminals, at least 4 with redundancy. HFGWs will
propagate through the Earth with little modification, but very slight HFGW phase
modification may be observed in surveillance applications (Baker, 2007.)
The counterpart to the fixed ground infrastructure would be the remote terminal side or
user side of the FTS infrastructure. Each remote terminal would need to be equipped
with a small HFGW receiver, which could pickup all 3 or 4 ground stations
simultaneously. The arrival times of the received PPS signals could be compared via
time difference of arrival, or TDOA, and used to develop a position estimate. The CW
signal phases could be compared to determine the Doppler velocity of the remote
terminal with respect to an Earth Centered Inertial (ECI) coordinate system. Thus, the
HFGW FTS system could be used as a navigational aid, akin to the GPS system. This
end of the infrastructure would be receive only and could therefore be a very low power
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