RTO-TR-SET-098 - FTP Directory Listing - Nato

Laser Based Stand-Off Detection
of Biological Agents
(RTO-TR-SET-098)
Executive Summary
Biological weapons have become an increasingly important potential threat in today’s military and civilian
arenas. They are relatively inexpensive to produce and can yield a significant impact as a terrorist weapon.
Early warning of a biological attack is essential to establish a timely defence and to sustain operational
tempo and freedom of action. In addition, the mapping of a biological attack is needed to obtain intelligence
on affected areas. For these reasons the need to develop methods to remotely detect and discriminate
biological aerosols from background aerosols and ultimately to discriminate biological warfare agents from
naturally occurring aerosols, is paramount.
Discriminating clouds that contain biological warfare agents from background aerosols with stand-off
detection is extremely challenging because the distinction between innocuous, ambient bacteria and other
biota and virulent microbes amounts to subtle differences in the molecular make-up. Since these subtle
changes involve such a small percentage of the molecules, only a slight effect on their optical signatures is
observed, making a high confidence detection and discrimination difficult. In addition, variations in growth
media and contaminants associated with the processing of bio-warfare agents can affect their optical
signatures, further exacerbating the task of analyzing and successfully discriminating the agent.
In order to address these fundamental challenges several stand-off technologies covering a broad region of
the electromagnetic spectrum are being investigated under RTG-055. These technologies include spectrally
resolved Ultraviolet Laser Induced Fluorescence (UV-LIF) at several different excitation wavelengths,
Infrared Depolarization, and Long-Wave Infrared (LWIR) Differential Scattering (DISC). Each of these
technologies offers its own strengths and challenges and all of them have demonstrated the ability to detect
and discriminate biological aerosol clouds to varying degrees.
In order to compare the relative merits of each technology several trials have been conducted. In addition
to the combined field trials we have conducted regular meetings to allow us to share information regarding
ongoing biological stand-off detection research. A workshop was held in Quebec, Canada (9 November
2006) to review current national programs and Industry and University research applicable to laser based
stand-off detection of BW agents.
Based upon the results of these activities the Task Group recommends that the best option for the nearterm
(2008 – 2010) application is UV-LIF. The choice of 266 nm or 355 nm excitation wavelength
depends upon the range requirement, discrimination potential and day-time performance considerations.
Spectrally resolved fluorescence improves the discrimination potential. Near infrared depolarization may
be added to enhance the discrimination potential and improve day-time discrimination. Long-term options
include infrared depolarization and LWIR DISC. These technologies have better day-time performance
and LWIR DISC has the potential for combined CB detection. Finally, advanced algorithms such as
Support Vector Machines can improve discrimination performance.
RTO-TR-SET-098 ES - 1