Detection of Explosives for Commercial Aviation Security (1993)

Bulk Detection

Sensing some physical or chemical property of an object under investigation. Usually used to differentiate from vapor detection which collects and analyzes volatized molecules.

Certification Test

A pass/fail test conducted by the FAA to determine if an EDS meets the EDS Performance Standard. The EDS must be a production version. If an EDS passes the certification test, it is qualified from an operational point of view to be deployed. It does not necessarily mean it is certified for deployment.

EDD

Explosive detection device. This is an instrument which incorporates a single detection method to exploit one or more common physical property of explosive materials for detection purposes.

EDS

Explosive detection system. This is a self-contained unit composed of one or more devices (EDDs) integrated into a system. It includes automatic detection, all necessary computer hardware and software, and baggage movement, positioning equipment, calibration methods, and maintenance procedures.

False alarm

An indication that explosive material is present when in fact there is no explosive material; also known as a false positive.

FFRDC

Federally Funded Research and Development Corporation. A not-for-profit private corporation which is chartered to only perform specialized work for federal agencies; prohibited from competing with private industry.

Full Level Threat

The full level (100 percent) threat is the minimum amount and configuration of a specific explosive material which would reasonably be expected to cause catastrophic damage to commercial aircraft in service.

Reference

Refers to an accepted or validated instrument that can be used to Instrument establish another instrument to give the correct reading.

Interferent

A substance that causes a response in a particular detection instrument that is similar enough to a real explosive that its response cannot be discriminated from a real explosive.

p(d)

An estimate of P_D derived from analysis of test data.. The formula is given by: p(d) = (# of detections)/(total number of possible detections)

p(fa)

An estimate of P_FA derived from analysis of test data.. The formula is given by: p(fa) = (# of false alarms)/((total # of possible false alarms)

Parametric Testing

Testing conducted to quantitatively measure critical performance parameters as a function of key variables.

P_D

True probability of detection. It is a measure of Sensitivity.

P_FA

False alarm rate; i.e. probability of sounding an alarm when no threat is present. Also known as false positives.

Qualification Test

An test conducted on an EDD or EDS to verify the performance claims of the manufacturer. Results can be in the form of parametric performance data.

R

Average time (in seconds) required to process a bag by an EDD or an EDS. This is affected by the instrumental method, the time required for the processing of the detection algorithms, and the bag transport system.

r

An estimate of R derived from analysis of test data. The formula is given by: r = (time required to process all bags)/(# of bags processed)

Sensitivity

Probability of detection of a threat, if a threat is present; i.e. a true positive. Same as P_D.

Specificity

Probability of not triggering an alarm if no threat is present; i.e. true negative. Calculated as (1-P_FA).

T&E

Test and Evaluation. This is the structured gathering of test data in accordance with a pre-planned strategy in response to specific items of interest. The test phase is followed by an analysis phase, which makes extensive use of statistical approaches to determine the values of measured parameters and the significance of the data.

Terrorism

Premeditated, politically motivated violence perpetrated against noncombatant targets by subnational groups or clandestine state agents, usually intended to influence an audience.

Verification Test

Same as Qualification Test.

Voxel

Volume element. Usually used to describe the element which a detection method samples and reports results. The number of voxels is a measure of resolution.

Z

Atomic Number. Which is equal to the number of protons in the nucleus. Isotopes of atoms have the same Z value, but different number of neutrons.

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