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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received signal, S, is (1.48x10 14)/(7x106 ) 2 = 3 wm ·2 , more than adequate for an
effective communication system.
With this configuration, the width of the needle-like, narrow HFGW beam at the receive
end is (2.3x 10·4 ) x (7x 106 ) = 1.6 km, and multiple HFGW carrier frequencies can be
used, so the signal is very difficult to intercept, and is therefore useful as a low
probability-of-intercept (LPI) signa l, even with widespread adoption of the technology.
From Equation (2) the amplitude A of the HFGW at 7,000 km with the HFGW frequency
(twice the IR frequency of VGw = 1.2x 10 14 s·1 ) given by: A = 1.28x 10-18 (S/vGw )V2 =
1.8x 10-32 (in dimensionless units or m/m), which would be detectable by the currently
designed Li-Baker HFGW detector. Since the exact frequency and phase of the HFGW
signal is known (unlike the stochastic re lic HFGWs, for which the Li-Baker detector was
designed), a much more sensitive, optimized HFGW detector will likely be developed.
As shown in Figure 8, from Grishchuk (2008), there will be negligible relic HFGW noise
at the IR HFGW generator's frequency of 1.2x 1014 s· 1 and no other cosmic sources at
these frequencies are currently hypothesized. Prior to the proof-of-concept test, one
can assume a noise figure at the Li -Baker detector of 10·8 Wm· 2 .
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Figure 8. Predicted Relic GW Energy Density as a Function of Frequency
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