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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.
“Anderson”2 pages
UNCLASSIFIED/fFOR. QFFIEIA.L: Ulii Qt!! X LIDAR can be used to detect and monitor hypersonic objects in several ways. By using a micropulse laser, a LIDAR system could be used to scan the sky for supersonic airborne objects. LIDAR can also detect the presence of a hypersonic vehicle by measuring the air velocities in the long turbulent wakes that they leave in the atmosphere. Electro Optic Systems in Sydney, Australia, 23 has announced a laser tracking system that can track objects in low-Earth orbit that are as small as 100 mm (4 inches). These objects pose a risk to satellites and manned space vehicles due to their high velocities (~ 8 km/s). There are an estimated 200,000 such objects greater than 10 mm in size currently orbiting the Earth. In the testing of hypersonic aircraft, a dedicated LIDAR system trained on the turbulent wake could measure the temperature and velocity distribution within the wake. This information can be used to design aircraft that would minimize detectability and increase vehicle rel iability. The U.S. Army, for example, reported on the use of a LIDAR system to monitor atmospheric particulates from the erosion of nose-cones on Athena-H reentry missions at the White Sands Missile Range in New Mexico in 1973. 24 The LIDAR system monitored the path of the reentry vehicles at altitudes of 9.3 km and 14.3 km and determined the concentration of erosion products and ice particles along the laser beam path. ACOUSTIC AND SEISMIC METHODS Infrasound Microphones can be used as a chronograph to measure the velocity of airborne objects. A supersonic aircraft generates a three-dimensional bow shock referred to as a "Mach cone ." If the aircraft's Mach cone, which is actually a pressure pulse, sweeps over two microphones separated by a distance, the velocity of the aircraft can be measured. In Figure 18, two microphones can sense the dramatic pressure increase that occurs behind a shock wave and determine the velocity by dividing the microphone separation distance by the delay time. Sound waves generated by the aircraft and the shock do not reach a terrestrial microphone until the Mach cone reaches the detector. The Mach cone has a half angle given by f3 = arcsin (1/M), and this yields a method of detecting the aircraft altitude, H: (20) "Infrasound" refers to subaudible (< 100 Hz) sound waves that are generated by explosions, sonic booms, and rocket exhaust. I nfrasound can be sensed by pressure transducers t hat detect the very small changes in atmospheric pressure that are induced by these events. The U.S. Air Force installed a network of infrasound stations around the country in the 1960s to detect the detonation of nuclear devices. Each station was composed of multiple pressure transducers so that the direction of the sound waves could be detected at the location of each station. UNCLASSIFIED//EQA: QlililEl.t.L: W&&: O,.L'l 25
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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.