interfere with the signals produced by all of these detection methods, the systems could still serve as a useful first indicator of a wide spectrum of potential threats. In the near term, improvements in neutron interrogation sources (i.e., neutron generators) and detectors for HEU would be a very useful step toward increasing our detection capabilities. (See Chapter 2 for more on sensors of nuclear materials.)

In addition to detection of chemical, biological, and nuclear agents or weapons, sensor systems can also be used to produce images. In particular, remote sensing technologies, such as light detection and ranging (LIDAR), synthetic aperture radar (SAR), and high-resolution satellite imagery, can be used for surveillence or during emergency response and cleanup efforts.6

Whatever type of attack the sensors are designed to prevent or respond to, the roles that sensor systems play can be described in terms of four specific categories—threat warning; incident response; treatment; and recovery and attribution—each with its own set of requirements:

  • Threat warning covers point-of-entry monitoring for preattack detection, as well as area monitoring of presumed target areas. Simply because the number of sensors required for area monitoring is great, it is necessary that they be low-cost, small, fixed in place, and highly sensitive (as opposed to selective). Also, maximum utility from area monitoring will require networking the sensors, thereby allowing for higher-level evaluation of a potential threat.

  • Incident response scenarios, by contrast, require handheld portable sensors and minimal training for operators. Both point sensors (for site characterization) and short-range standoff sensors (for site evaluation prior to entry) will be of value. Incident response will occur at a critical time for evaluating and controlling the severity of the attack, but this will also be the time of weakest coordination as personnel from federal, state, and local governments come onto the scene. A mechanism for networking data from sensors carried by these people would allow a single picture of the threat to evolve more quickly.

  • For treatment, the sensors’ greatest contribution will be made in the aftermath of a biological attack. They should be able to provide quick and accurate diagnoses, without the hours or days of time lag associated with standard culture-growth techniques.

  • For recovery and attribution, the speed at which information is available is usually less important than the accuracy of the data. For recovery, sensors would be useful for monitoring the level of contamination at a site during and after cleanup activities. For attribution, the goal would be the use of sensors in


After 9/11, LIDAR technologies allowed engineers to start evaluating the dimensions of debris piles and the zones of heat and fire at the World Trade Center even when smoke still surrounded the site.

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