Mission Description Objective Relevant Sensor Technology
Precision targeting Concealed Threat Targeting Engage threats hidden behind abutments, on other side of buildings, etc. EO/IR, radar imaging

Note: HSI/MSI, hyperspectral imaging/multispectral imaging.

Obscured targets include objects within buildings, under foliage, or buried under soil. From an SA perspective, identifying all threats close to the squad is the goal. Lower frequency radar—about 1 GHz and below—is the technology of choice for obscured target detection. These lower frequency signals penetrate many building materials and foliage. Signal attenuation is severe and multipath can prove problematic, thereby limiting the system operating range. Laser detection and ranging (or LADAR, sometimes called light detection and ranging or LIDAR) is also a useful technology to map detected threats under foliage; LADAR generally does not detect sense-through-the-wall collections but can be used against targets under foliage when the laser has line of sight to the target.

Millimeter wave (mmw) radar can detect concealed weapons at moderate ranges. Such radars (typically in the range 35-95 GHz) are generally smaller systems of comparable or better resolution than their lower frequency counterparts. New airport surveillance technology uses mmw scanners at security checkpoints. Squad applications would likely be for concealed weapons detection at ranges of a few meters to tens of meters. Magnetometers and metal detectors are not likely to have application, since they operate over shorter distances than mmw radar.

Detection, characterization, and location of enemy emitters is a SIGINT function. Typical emitter threats are in the radiofrequency range, though SIGINT receivers have been developed to intercept laser-modulated signals. SA against all common emitters—typically, cell phones in the GSM bands and other handheld radios down to VHF—is of value to the squad. The common approaches to SIGINT collection include the use of a single, multiaperture receiver with sufficiently long baseline to achieve accuracy goals; multi-sensor intercept topologies (fusion of the intercepts from two or more sensors); or, moving a single intercept receiver through large integration angle and using frequency or time-differencing techniques. This latter approach requires greater time and may have limited applicability to the squad’s SA needs. SIGINT sensors can apply to obscured target detection when an emitter is present, such as a cell phone or a key fob or other exploitable device; lower frequency operation is essential to minimize signal attenuation through the obscuring medium, but SIGINT incurs only one-way loss (as opposed to two-way loss in radar).

Navigation in a GPS-denied environment can employ coded radio frequency signals and multilateration in a local network, using principles similar



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