Engineering topics

Thompson, R. T., Jr.

Publications and source records attributed to Thompson, R. T., Jr..

3 records

NASA NTRS1976

Differential absorption and scattering sensitivity predictions

A set of general equations for evaluating the sensitivity of the Differential Absorption and Scattering (DAS) technique based upon a conventional analysis of statistical errors is derived. The equations are put in a proper form for evaluating total column density and range resolved concentration measurements of a variety of atmospheric species. The derived equation are subsequently used to analyze the sensitivity of DAS in three specific applications assuming realistic parameters for the optical and electronic components of proposed DAS systems. The three DAS applications evaluated are: (1) measurement of nitrogen at ground levels over a horizontal path; (2) measurement of atmospheric ozone depletion in the wake of a jet engine at 20 km altitude; and (3) measurements of the ozone distribution in the atmosphere from an orbiting space platform, in a downward viewing mode. The results of this study have shown that with reasonable laser energy and telescope receiver dimensions, DAS is capable of meeting requirements for performing these measurements.

Thompson, R. T., Jr.↗

NASA NTRS1976

Remote sensing of atmospheric SO2 using the differential absorption LIDAR technique

The paper reports an investigation of the capabilities of a UV differential absorption lidar (DIAL) system for remote measurements of sulfur dioxide emissions. Two features of the present DIAL system are an absorption cell permitting the determination of the difference in SO2 absorption coefficients for the two transmitted wavelengths and a calibration cell permitting the linearity and performance of the system to be evaluated. The DIAL technique is described along with the transmitter, receiver, data-adquisition, and data-processing components of the investigated system. Quantitative measurements of the average SO2 concentration in a region surrounding the exhaust stack of a steam-generating plant are discussed which show that the present system has measurement sensitivities of 10 ppb at a range of 0.8 km and 20 ppb at 1.9 km. Based on performance characteristics obtained during a calibration of this system, it is predicted that a measurement sensitivity of less than 4 ppb over a 1-km path will be attained.

Hoell, J. M., Jr.↗

NASA NTRS1975

Measurements of SO2 absorption coefficients using a tunable dye laser

High-resolution measurements of SO2 absorption coefficients in the UV are presented in the wavelength interval between 2962 and 3011 A using a frequency-doubled dye laser as the radiation source. These measurements have application to pollution monitoring of SO2 using the differential absorption scattering (DAS) technique. The spectral resolution of the measurements was 0.2 A (determined by the linewidth of the dye laser) and the generated spectra exhibited considerable rotational structure on the (000) double prime to (060) prime, (070) prime, and (080) prime electronic-vibrational transitions. The latter transitions correspond to center wavelengths of 3001.8, 2981.0, and 2962 A, respectively. The laser measurements were obtained with a signal-processing technique which eliminated calibration procedures associated with conventional optical-absorption measurements. Using this technique, the statistical uncertainty associated with measured absorption coefficients has been reduced to less than plus or minus 2% with a wavelength uncertainty of the laser source of plus or minus 0.1 A.

Thompson, R. T., Jr.↗