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

This Defense Intelligence Reference Document, DIA-08-1004-005, is dated 6 April 2010. The Defense Intelligence Agency's Defense Warning Office prepared it under the Advanced Aerospace Weapon System Applications program. It reviews proposed laboratory generators and detectors for high-frequency gravitational waves. It favors a piezoelectric approach for proof-of-concept tests, IR-excited molecules for an operational transmitter and the Li-Baker detector as the receiver. It estimates about 1.9 million bits per second over 7,000 km through the Earth and discusses timing standards and interplanetary navigation uses.

From the source:Release of 2026-09-18 Incident: 4/6/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD examines whether high-frequency gravitational waves could serve as a communications medium while avoiding the attenuation that limits radio-frequency systems. The report surveys proposed transmitter and detector concepts, argues that gravitational-wave communications could support secure point-to-point links, timing standards, and interplanetary navigation, and gives particular attention to laboratory generator concepts and the Li-Baker detector as possible building blocks for such a system. The document makes clear, however, that the entire concept depends on capabilities that had not been demonstrated in practice, including laboratory-scale generation and reliable detection of usable high-frequency gravitational-wave signals. It is an exploratory systems-oriented review built around a future communications concept.

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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, bu t 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 navigationa l 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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