Edward R. Murray

Atmospheric water vapor measurements with an infrared (10‐μm) differential‐absorption lidar system

We report the recent design, construction, and operation of the first infrared differential‐absorption lidar system for remote range‐resolved sensing of gaseous species. The target gas in the present case was water vapor, which was measured using several CO2 laser lines near 10.3 μm. Profiling of the concentration of many air pollutants to a horizontal range of at least 12 km appears feasible with commercially available components.

Remote measurement of ethylene using a CO 2 differential-absorption lidar

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.

Remote measurement of HCl, CH 4 , and N 2 O using a single-ended chemical-laser lidar system

The applicability of the high energy discretely tuned DF laser for remote measurement of HCl, CH(4), and N(2)O has been investigated. A single-ended or monostatic lidar system using radiation backscattered from topographical targets was tested. Selective absorption of the backscattered signal was used to infer concentration of gaseous species. Good agreement was obtained between the lidar measurements and the concentrations determined by in situ measurements in the remotely positioned sample chamber. The lowest measurable material concentration for each gas was inferred from random fluctuations in the measured concentration. Sensitivity of the existing system to HCl, CH(4), and N(2)O was found to be 0.05 ppm-km, 6.0 ppm-km, and 0.24 ppm-km, respectively. An N(2)O plume was also measured in the open atmosphere between the lidar system and a foliage target to demonstrate system capabilities under typical field conditions. Performance predictions indicate that total burden and range-resolved species concentration measurements are feasible to a range of 10 km or more with commercially available components.

Measurement of average atmospheric temperature using a CO 2 laser radar

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.

Remote Measurement of Gases Using Discretely Tunable Infrared Lasers

Single-ended laser radars using discretely tunable infrared gas lasers have been demonstrated to be capable of high-sensitivity remote measurement of gases. Two systems have been investigated: (1) a deuterium fluoride laser was used for remote measurement of the integrated concentration of HC1, CH4, and N20 between the lidar system and a topographic target; and (2) a CO2 laser was used for range-resolved measurement of water vapor using radiation backscattered from naturally occurring aerosols in the atmosphere. Calculations indicate that range-resolved concentration profiles can be obtained for many gases at a range of 10 km using commercially available components.

Carbon dioxide laser backscatter signatures from laboratory-generated dust

A dual CO2 laser system was used to measure aerosol backscatter spectral signatures from dust minerals (kaolin, illite, montmorillonite, colemanite, and limestone) as well as from a soil sample from Dugway Proving Ground, UT. Complex refractive indices measured from bulk samples of the materials and particle size distributions measured with a cascade impactor were used to compute theoretical backscatter spectra using Mie theory. The measured signatures agreed well with calculated signatures for most minerals and the soil sample. The experiment demonstrated the feasibility of detecting the compositional elements of dust using a CO2 laser-based system.

Single-ended measurement of infrared extinction using lidar

The goal of this study was to investigate the feasibility of single-ended measurement of the total extinction coefficient using an ir lidar system. Extinction was measured using a CO(2) laser radar system at four wavelengths near 10.3 microm. The measured results agree with theoretical estimates of extinction over a wide range. Single-ended measurements of extinction appear feasible to a horizontal range of 10 km using commercially available components. The system could potentially generate extinction data in a 3-D grid, enabling one to determine ir transmission between any two points in the field.

Remote Measurement Of Gases Using Discretely Tunable Infrared Lasers

Single-ended laser radars using discretely tunable infrared gas lasers have been demonstrated to be capable of high-sensitivity remote measurement of gases. Two systems have been investigated: (1) A deuterium fluoride laser was used for remote measurement of the integrated concentration of HCI, CH4, and N20 between the lidar system and a topographic target; and (2) a CO2 laser was used for range-resolved measurement of water vapor using radiation backscattered from naturally occurring aerosols in the atmosphere. Calculations indicate that range-resolved concentration profiles can be obtained for many gases at a range of 10 km using commercially available components.