AAWSAP DIRD, Detection and High-Resolution Tracking of Vehicles at Hypersonic Velocities, November 2010

This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency's Defense Warning Office in fiscal year 2010 as part of the Advanced Aerospace Weapons System Applications program. It reviews how air flows around objects at subsonic, supersonic and hypersonic speeds, covering shock waves, wakes and ionization. It then compares ways to detect and track hypersonic vehicles, including radar, optical, infrared, LIDAR, infrasound and seismic methods. The report makes four recommendations, among them building a database of aircraft wake signatures and developing novel detectors.

From the source:Release of 2026-09-18 Incident: 11/20/10, 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 surveys how hypersonic vehicles may be detected and tracked by exploiting the physical effects they create in flight, especially shock waves, ionized gas, hot surfaces, and turbulent atmospheric wakes. The report reviews a broad set of detection methods, including radar, infrared sensing, optical imaging, LIDAR, passive radio reflection, infrasound, and seismic techniques, and argues that the most effective systems will likely combine multiple sensor types, because each captures different features of a high-speed vehicle’s passage through the atmosphere. It presents radar and infrared sensing as the strongest existing tools for operational detection, while giving particular attention to wake-based methods such as LIDAR and passive radio techniques for improving tracking, identification, and discrimination of future hypersonic aircraft. The paper identifies hypersonic vehicles as an evolving surveillance problem in which future progress will depend on better multi-sensor integration, improved wake characterization, and novel signature-exploitation techniques.

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Figure 18. Mach Cone Generated by a Supersonic Object.
The Los Alamos National Laboratory still operates four of these stations that were installed in
1983 at various locations in the United States. 25 These infrasound detector stations are
relatively inexpensive and are easy to maintain. While they have not yet been used to sense
nuclear detonations, they do detect sonic booms, and they were responsible for identifying
and tracking two large bolides, or brilliant meteors, that entered the Earth's atmosphere in
2000 and 2001. While capable of sensing meteors as small as a baseball, in 2001, a large
bolide entered the Earth's atmosphere over the Pacific Ocean and exploded near Baja
Ca lifornia. The bolide was estimated to have a 3.6-meter diameter and exploded with the
energy of 6,000 tons of TNT.
Even a single infrasound station can track a meteor. On 4 October 1996, a station in
Colorado observed a meteor near Bakersfield, California. 26
Another infrasound station network includes the I nternational Monitoring System, a network
of 321 stations around the world designed to monitor explosions that would represent
violations of the Comprehensive Nu clear Test Ban Treaty. Although this network may be a
useful worldwide resource for the detection of meteors, reentry vehicles, and hypersonic
flights, its use in the detection of nuclear explosions is dubious given the circumstances of
November 1999. During this event, a sonic boom was monitored in the skies above northern
Germany. The information provided by the network could not differentiate between a meteor
and a nuclear explosion.
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