A dual CO(2) laser-based differential absorption lidar (DIAL) system has been constructed and demonstrated for range-resolved mapping of chemical vapor plumes. The system acquires high range resolution through the use of plasma-shutter pulse clippers that extinguish the nitrogen tail of the CO(2)-laser output. Aprogrammable servomotor-driven scanner allows full hemispherical coverage of the interrogated field. A high-speed direct-detection receiver subsystem is used to gather, process, and display vapor-concentration data in near real time. Data demonstrating range-resolved detection of low concentrations of chemical plumes from ranges of 1 to 2 km are presented. In the column-content detection mode, trace levels of secondary vapors from various organophosphate liquids were monitored. Detection of an SF(6) vapor plume released 16 km from the DIAL system is also adduced.

A single-ended CO(2) lidar system has been used to measure the average temperature over a path between the lidar and the foothills located 5 km away. The CO(2) lidar was used to measure the ratio of transmission of the P(38) to the P(20) lines in the 10-microm band of CO(2). This ratio of transmission is directly related to temperature. Good correlation was obtained between the lidar-measured temperature and the thermometermeasured values.

Ethylene has been monitored with a single-ended CO(2) lidar using topographical scattering. Foliage on the foothills 5 km away provided the backscattered signal. Interference due to water vapor was found to be equivalent to 7.6 ppb of ethylene, and this correction was applied to the data. The total measurement uncertainty was found to average 1.6 ppb. The lidar-measured concentrations agree with point monitor samples over a wide range of ambient concentrations.