The recent controversy over the possibility that biological warfare agents may have caused the dire illnesses plaguing the men and women who fought in Operation Desert Storm has surely captured everyone's interest. Detecting and tracking these deadly agents presents a considerable problem to those charged with protecting members of the armed services.To deal with this problem, the US Army Chemical and Biological Defense Command developed a system, dubbed the Long Range - Biological Standoff Detection System (LR-BSDS), that can detect, range and track biological aerosol clouds while on the move at distances up to 30 km. The system employs lidar technology and comprises three major components: a Continuum Surelite I-20, which is used as an infrared laser transmitter; a receiving telescope; and a detector with an information processor integrated into the frame. The LR-BSDS was designed to fit inside an unmodified UH-60 helicopter. Both the transmitter and receiver are fixed on a rotating table that is mounted on a cabinet where the information processor, power supply, laser controller and cooling system reside.The Surelite I-20 underwent some modifications for space and environmental considerations: The power supply was vertically mounted in the lidar cabinet and the coolant reservoir was removed and mounted separately. "Because the system needs to work inside a helicopter, there were restrictions on the weight, mass and power consumption. The laser also needed to be air-cooled and have high energy-per-pulse operation," explained Jim Cannaliato, LR-BSDS's team leader. Because of the size constraints, it was also necessary for the laser to have a separate head with an umbilical to the power supply and a single pumping chamber in a compact package. The Surelite met all of these qualifications.The army contracted for three systems, the first of which was delivered in April 1996 for acceptance testing. To date, the testing has provided excellent results, with the lidar system detecting a long-line source aerosol cloud 30 km from the helicopter platform.Future systems will have additional modifications, including moving the laser coolant pump and the reservoir outside of the laser control module for easier maintenance. A microswitch will also be added to the manual shutter so the operator can check the laser prior to takeoff. "The laser head will be sealed against dust and water contamination, and additional thermocouples will be installed so the operator has better control of the laser in hostile environments," Cannaliato said.It may be too much to hope for that this system never has to be put to use, but there is some comfort in knowing that photonics technology is at work protecting those who protect us.