Principles of Modern Radar - Volume 2 1891121537

environment that may mask the generally weaker return from a person. Since people aretypically slow-moving targets, humans also often fall below the minimum detectable velocity(MDV) of ground moving target indication (GMTI) radars. Moreover, these groundsurveillance radars also offer no information beyond that of a target being detected at acertain range, azimuth angle, and radial velocity. These radars are usually used in tandemwith video cameras that can zoom in on the detected object and thereby determine whatit is, what it is doing, and whether it poses a threat. Thus, in addition to the developmentof more sophisticated, higher performance human detection algorithms, which functionin even the most adverse conditions, the associated automatic identification, activity classification,and tracking algorithms remain equally important research topics.With these goals in mind, there are several promising programs under way to developaerial dismount detection radar. The upgrade to the Lynx Advanced Multi-Channel Radar(AMR) [24], currently under development by General Atomics Aeronautical Systemsin cooperation with Sandia National Laboratories, was successfully tested for dismountdetection during flights conducted in May 2010 and achieved operational availability bythe end of 2010 [25]. The Lynx system is a synthetic aperture radar (SAR) with GMTIcapability that exploits space-time adaptive processing (STAP) for dismount detection.Lynx, which is designed for the Predator and Predator B type unmanned aerial systems(UASs), is being evaluated as a possible upgrade to the Army’s MQ-1C Sky Warrior/GrayEagle unmanned aircraft system, which is equipped with an Northrop-Grumman AN/ZPY-1 STARlite small tactical radar [26, 27].Another promising program is the Vehicle and Dismount Exploitation Radar (VADER)[28, 29] being designed by Northrop Grumman, which completed its first round of testingin 2009 [30]. VADER has three operating modes: SAR, GMTI, and dismount movingtarget indication. The specific goal of VADER is to “track moving dismounted individualsand characterize suspicious actions” from an altitude of about 25,000 ft (7.62 km), suchas people planting improvised explosive devices (IEDs) [31]. Additional features envisionedfor VADER include long-duration vehicle tracking, SAR coherent change detection(CCD), and motion pattern analysis. The VADER system, which is physically encasedin a pod about 1.5 meters long, was designed to fit beneath the wing of a Gray Eaglemedium-altitude UAS but is also being considered for mounting on YMQ-18A A160THummingbird UASs.Two other programs worth attention are the Affordable Adaptive Conformal ESARadar (AACER) program and the Foliage Penetration, Reconnaissance, Surveillance,Tracking and Engagement Radar (FORESTER) program. AACER was awarded toRaytheon’s Space and Aerospace Systems (SAS) for the development of a multifunctional,multifrequency system capable of ground moving target detection and tracking. Inaddition to dismount detection, the radar also includes SAR imaging, and high data-rateKa band communications [32]. The FORESTER program was awarded to Syracuse ResearchCorporation to accomplish dismount and vehicle detection even in heavily coveredareas, such as forests [33]. The FORESTER program has been tested on the EH-60 BlackHawk, and the A160T Hummingbird UAS in Fort Stewart, GA in 2009 and over Belizein 2010 [34].Thus, human–dismount detection is an integral capability of many of the radar systemscurrently under development. This chapter is intended to examine in detail the modelingand signal processing techniques that have made these recent advances possible. In Section16.2, the salient characteristics of human motion, kinematic models based on gait analysis,and expected radar return will be discussed. With this foundation, spectrogram-based16.1 Introduction 707