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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ionized wake. This techn ique for detecting hypersonic meteors is not fully developed and
appears to be employed only by hobbyist s.
Since a receiver can be tuned to a specific over-the- horizon t ransm itter, it may be possib le t o
develop a network of rad io receivers to provide information on high-speed object s in t he
atmosp here. Multip le stations would all ow t riangulation of t he object to determine velocity
and position as a function of t ime, i.e ., tracking and pat h pred iction. The sound files also
conta in information that cou ld provide information on the hypersoni c object. Detection of t he
shock provides information on the position of the object while t he transient "whistles"
reflected from the ionized wake may provide information on the St rouhal eddy frequency that
could directly infer the object's velocity . This detection technology should be further
developed.
Hypersonic Aircraft
Radio Receive r The radio receiver is not in
line-of-sight with the
transmitter, yet receives
reflected energy from t he Transmitter
transmitter by the aircraft.
Figure 11. Radio Reflection Detector.
OPTICAL METHODS
Sky Cameras and Photographic Methods
A classic example of a hypersonic object passing t hrough t he Earth's atmosphere is a
met eor. Meteorite hunters and astrophysicists have worked to develop methods to detect
these object s as they fa ll to the Earth. Motion-detection video syst ems provide information
on locati on and direction of meteors passing t hrough t he atmosphere by det ecting their
visible wake. The El Paso All Sky Camera proj ect 14 is one example and even provides live
st reaming video of meteoric events.
Photographs of objects in orbit with diameters rang ing from 0.1 meter to several meters
have been used to determine t heir expected t rajectory as meteors as they entered and fell
through t he Earth's atmosphere. 15 Th is technique was fi rst used to monitor the Pribram
met eorite simultaneously by several observat ories in 1959. This techn ique was even used to
locate a 1. 75-kg enstatite chond rite meteor ite called Neuschwanstein reported in 2003. The
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