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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.
“Pacific Ocean”4 pages
UNCLASSIFIED/ ,'1"1!11'- l!ll"l"ll!lllit lal!i! i;n1t~r RADAR systems are widely used for aircraft surveillance and can detect the distance to objects and the position of an object (through triangulation); with Doppler RADAR, the velocity can be directly measured. RADAR does have limitations. While low-frequency RADAR systems are capable of following the curvature of the earth, the long wavelength of this energy makes it difficult to resolve small objects. Higher frequency RADAR tends to be more "line of sight." Since it depends upon reflected energy, several problems are highlighted by the RADAR Equation: (15) In this equation, Ptransmrtted represents the transmitted power, Prec:eived the received power, G the transmitting antenna gain, A the aperture area of the receiving antenna, a the RADAR cross section, F the pattern propagation factor, and Rt and Rr are the distance from the transmitter to the target and the target to the receiver, respectively. If the RADAR transmitter and receiver are in the same unit, the power returned as a reflection from a target decreases as R4 . This means that energy received in reflected energy decreases by 94% every time the distance to the target is doubled. RADAR depends upon the reflection of electromagnetic waves off of a target's surface, thereby making objects with a small RADAR cross section difficult to detect (e.g., stealth aircraft). Atmospheric phenomenon, including inversions and turbulence, can lead to interference with RADAR reflections. Even with these limitations, RADAR is widely used to monitor high-speed aircraft, meteors, and man-made objects reentering the atmosphere from Earth orbit. Velocity Vector Radar Dish Hypersonic Vehicle '+-----'--I1--t-H--t--tt-~~=n;3)Radial direction / Rotat Pedei Reflected Energy Transmitted Energy R = radial distance Figure 10. Schematic of a RADAR System. Doppler RADAR Doppler RADAR systems yield velocity data for a target. Pulsed RADAR systems send out a short burst of high-frequency radiation that is reflected from a target. The RADAR unit processes the delay time between the transmitted pulse and the received echo to determine the range or distance to the target. The energy reflected from the target is, however, 14 UNCLASSIFIED/) I OK 01 r1e1111t ~:!I! 8HLY
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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.