a change in the performance requirements also changes the importance and priority of the technology challenges.

The system-development requirements need to reflect the operational needs and validated threats and match the technology capabilities against those operational needs and threats.¹ The system-development requirements are to develop a technology that can accomplish the following:

1. Detect the presence, location, and identification of weapons (metallic and ceramic), explosive devices, and other proscribed items concealed underneath a person’s clothing; and

2. Monitor a person for weapons (metallic and ceramic), explosive devices, and other proscribed items quickly and safely, without violating anyone’s privacy.

An imaging system (or systems) is proposed because proscribed items and baggage now vary so broadly in terms of size and materials.

It is generally acknowledged that no single sensor technology has the capability to accomplish the entire mission. A millimeter-wavelength/terahertz imaging device is seen to be a critical subsystem in a layered system of complementary systems that can be dynamically reconfigured, combined, and deployed against an evolving terrorist threat to commercial transport. The most likely fielding of millimeter-wavelength/terahertz imaging systems will be accomplished as a part of an overall systems approach as an element of the passenger-screening checkpoint and baggage checkpoint, or as part of the access control to the secure areas of the facility or aircraft interior.

The principal imaging system components are these:

• A detector array and/or a scanning system,

• Image acquisition hardware and software,

• Image analysis and recognition computation,

• A database of key threat images and spectra,

• Display hardware, and

• A network interface with other elements of the layered system.