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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 14. Infrared Energy Spectra for Mach 3 (red line) and Mach 3.5 (blue dashed line).
The peak wavelength changes for hypersonic aircraft with speeds that range from Mach 1 to
Mach 100 are included in Figure 15. Satellite systems currently monitor 2.5- to 5-micron IR
emissions and could detect aircraft with speeds as low as Mach 3. While Figure 15 plots the
peak wavelength, aircraft at Mach 5 or higher have lower temperatures in the turbu lent wake
that would still be detectable. The peak temperatures are shown in Figure 16. Above 550 K,
the perfect gas law cannot be used to accurately predict the peak temperature due to
ionization and disassociation of molecules in the air. Figure 15 and Figure 16 use the "rule of
thumb" described earlier in the t heory of hypersonic vehicle flight to determine peak
temperature and the corresponding wavelength.
Military satellite systems monitor infrared energy emitted by objects on the surface of the
Earth. Kidd and Caldweli 20 reported on the use of IR systems for defense support in 1992
and highlighted the problems in resolving missile launches and wakes from background
"clutter" caused by the infrared emissions from other objects on the surface of the Earth.
Typical satellite IR systems detect energy between 2 and 5 microns. To verify that an object
is an actual missile, the object must be detected in the 2.6- to 3.2-micron band, which
corresponds to the emission from water vapor in the hot exhaust of a rocket . It must
simultaneously be identified in the 4.1- to 4.8-micron range to differentiate the missile from
background clutter. One problem encountered in missile detect ion involves the "glint" that
occurs as aircraft at high altitude passing over land at night reflects sunlight to an overhead
satellite . Computer softwa re to discriminate signals from background heat combined with
detection in the two different infrared bands helps to identify actua l missile launches. FUR
(forward looking infrared) is also now used for atmospheric survei llance to detect objects in
the 3- to 5-micron band and in the 5- to 14-micron band.
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21 Not linked to a story yet.
Official release, from the pursue collection. The PDF is mirrored here; the original link is above. 46 pages are in the text index: search them above, or from the library's search.