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This Defense Intelligence Reference Document from the Defense Intelligence Agency, dated 20 November 2010, was one of a series of advanced technology reports produced in FY 2010 under the Advanced Aerospace Weapon System Applications (AAWSA) Program. It reviews the theory of subsonic, supersonic and hypersonic flow. It then compares electromagnetic, optical, and acoustic and seismic methods for detecting and tracking hypersonic objects, and it makes four recommendations for progress over the next 30 years.
“Anderson”2 pages
UNCLASSIFIED//F8R 8FPll!ltllt "32 OIGLI LI DAR. By attaching a rotating mirror to vary the direction of the laser beam, it is possible to traverse the laser across surfaces to develop 3-D maps of objects using "imaging LIDAR." As an example, during the DARPA challenge held in the Nevada desert in 2005, autonomous automobiles used LIDAR to build a map of all objects in front of the vehicle and used it for collision avoidance and navigation. LIDAR systems have also been used to obtain accurate maps of the surface of mars from the Mars Orbiting Global Surveyer. LIDAR systems for meteorological studies are often mounted in aircraft and fired from the side of the fuselage to obtain a two-dimensional horizontal map of the atmospheric conditions. A measurement technique known as Laser Doppler Velocimetry (LDV) uses the Doppler shift in the transmitted and reflected laser light to measure the velocity of the target and the properties of the air along the axis of the laser beam. LIDAR systems using pulsed YAG lasers are capable of measuring many properties of air along the path of the laser beam. As shown in Figure 17, if a laser pulse is fired toward a distant target, light is reflected from particles in the atmosphere and this light is collected through a beamsplitter and directed to a photodetector. By knowing the time interval between generation of the laser pulse and the time that each reflected signal is received, the distance along the beam can be accurately determined for each data set. By recording this optical information as a function of time, using Raman spectroscopy, particle light scattering, and absorption theory, multiple properties of the air and particles in the air along the path of the laser can be measured as a function of distance from the transmitter. Particle density, velocity, and chemical species can be measured using pulsed LIDAR systems. Concentration of airborne gas species (oxygen, nitrogen), air temperature, and air velocity can also be measured in this fashion. v(x,y) 24 v(x. YI v(x.vl .... "v(x. y) '' - .., v(x,y) 1X, y ''\ Laser Beam "iupe=nic Vehicle aOO Turbulent Wake Beamsplitter Pulsed YAG Laser Figure 17. Schematic of a Pulsed LIDAR System. UNCLASSIFIED/ ii OR Oi"l"l@lit.ls l!lliiii liUii,H
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Report, from the dia 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.