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Huffaker, R. M.

Publications and source records attributed to Huffaker, R. M..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Southern Hemisphere tropospheric aerosol backscatter measurements - Implications for a laser wind system

To identify the aerosol size fraction that is responsible for the 10.6-micron backscatter and the morphological composition of these particles, values of backscatter coefficient at 0.532 micron, 0.694 micron, and 10.6 microns were determined both by direct measurement and by Mie computation from measured microphysical properties of aerosols over eastern Australia between 4 deg and 41 deg S. The values of backscatter coefficient determined from direct measurements at 10.6 microns were found to agree well with values obtained indirectly from calculations based on measured aerosol particle size distributions and properties. It was also found that backscatter at 10.6 microns and at visible wavelengths were sensitive to different regions of the aerosol size spectrum, with considerable day-to-day variability observed at all wavelengths.

Gras, J. L.↗
NASA NTRS1986

Coherent lidar technology for global wind profiling

Current lidar systems are proven sensors for atmospheric wind measurement. Ground-based and airborne continuous wave and pulsed CO2 systems were developed and applied to several wind measuring applications. Analytical and hardware feasibility studies indicte the feasibility of measuring the global wind field from a space splatform. A Global Backscater Experiment is planned by NASA to develop a global model of aerosol backscatter using a CO2 laser. Ground-based aerosol backscatter profiles will also be obtained using a ruby and a pulsed CO2 lidar.

Huffaker, R. M.↗
NASA NTRS1986

Wavelength dependence of coherent and incoherent satellite-based lidar measurements of wind velocity and aerosol backscatter

The results are presented of a capability study of Earth orbiting lidar systems, at various wavelengths from 1.06 to 10.6 microns, for the measurement of wind velocity and aerosol backscatter, and for the detection of clouds. Both coherent and incoherent lidar systems were modeled and compared for the aerosol backscatter and cloud detection applications.

Kavaya, M. J.↗
NASA NTRS1976

Focused laser Doppler velocimeter

A system for remotely measuring velocities present in discrete volumes of air is described. A CO2 laser beam is focused by a telescope at such a volume, a focal volume, and within the focusable range, near field, of the telescope. The back scatter, or reflected light, principally from the focal volume, passes back through the telescope and is frequency compared with the original frequency of the laser, and the difference frequency or frequencies represent particle velocities in that focal volume.

Bilbro, J. W.↗
NASA NTRS1976

Wind measurement system

A system for remotely measuring vertical and horizontal winds present in discrete volumes of air at selected locations above the ground is described. A laser beam is optically focused in range by a telescope, and the output beam is conically scanned at an angle about a vertical axis. The backscatter, or reflected light, from the ambient particulates in a volume of air, the focal volume, is detected for shifts in wavelength, and from these, horizontal and vertical wind components are computed.

Cliff, W. C.↗
NASA NTRS1976

Wind velocity measurement

Homodyne laser-Doppler system determines three-component wind velocity at altitudes of several kilometers in clear-air conditions. There is no need for deployment of towers, radiosondes, or for seeding airflows.

Cliff, W. C.↗
NASA NTRS1976

Laser-Doppler measurement of air turbulence

Laser-Doppler system with 10-micron wavelength tracks 1-micron dust particles to measure air turbulence. System is designed for use at airports to measure and track aircraft trailing vortexes.

Huffaker, R. M.↗
NASA NTRS1976

Laser Doppler systems in pollution monitoring

The paper reports on a program undertaken to determine the feasibility of using a laser Doppler velocimeter (LDV) to measure smoke-stack gas exit velocity, particulate concentration, and mass flow. Measurements made with a CO2 laser Doppler radar system at a coal-burning power plant are compared with in-stack measurements made by a pitot tube. The operational principles of a LDV are briefly described along with the system employed in the present study. Data discussed include typical Doppler spectra from smoke-stack effluents at various laser elevation angles, the measured velocity profile across the stack exit, and the LDV-measured exit velocity as a function of the exit velocity measured by the in-stack instrument. The in-stack velocity is found to be about 14% higher than the LDV velocity, but this discrepancy is regarded as a systematic error. In general, linear relationships are observed between the laser data, the exit velocity, and the particulate concentration. It is concluded that an LDV has the capability of determining both the mass concentration and the mass flow from a power-plant smoke stack.

Miller, C. R.↗
NASA NTRS1975

CO2 laser doppler systems for the measurement of atmospheric winds and turbulence

Two CO2 laser doppler systems developed by NASA and some results obtained with them are discussed. A continuous wave, monostatic system for short-range wind measurement is described, and direct comparisons between the data obtained with it and with a cup-anemometer/wind vane system and a hot-wire anemometer show excellent agreement between the systems. Improvements being made in three CW, CO2 laser doppler systems, including a filter bank for optimized signal processing and a versatile scanning system, are noted. A pulsed CO2 system for measuring clear air turbulence is described, and results of test performance on board a Convair 990 are presented. It is noted that while the system was able to measure air speed and turbulence, the range of its transmitter-atmosphere-receiver was lower than predicted, and a difference of about 20 to 30 dB existed between the actual and theoretical turbulence measurements. Factors that may account for this loss are listed.

Huffaker, R. M.↗
NASA NTRS1975

A laser Doppler system for the remote sensing of boundary layer winds in clear air conditions

The system discussed uses a laser Doppler radar in combination with a velocity azimuth display mode of scanning to determine the three-dimensional wind field in the atmospheric boundary layer. An attractive feature of this CW monostatic system is that the ambient aerosol provides a 'sufficient' scattering target to permit operation under clear air conditions. Spatial resolution is achieved by focusing.

Lawrence, T. R.↗
NASA NTRS1974

Clear air turbulence detector

A system to be employed by an aircraft for the detection of clear air turbulence is described. The system employs a laser light beam which is directed ahead of the aircraft along the flight path. The portion of the light reflected back to the aircraft by atmospheric aerosol is detected and analyzed for Doppler shift. The velocity and intensity of the turbulence is determined by the type and amount of the light reflected.

Dahm, W. K.↗
NASA NTRS1974

Application of a single laser Doppler system to the measurement of atmospheric winds

The feasibility of employing a single laser Doppler velocimeter (LDV) system to remotely measure one-, two-, and three-dimensional velocity components in atmospheric flow fields is presented. A focused continuous wave CO2 laser emitting at the 10.6 mu wavelength is used as the laser source. Scan configurations employed by the LDV system were single-point, two-point, conical, and spiral conical. Test results are presented, which include favorable comparisons of velocity components measured by conventional anemometry and the LDV system. The feasibility using a single-beam LDV employing a conical scan technique for measuring two- and three-dimensional mean winds. Measurements to 300 m in dense fogs showed the ability of the LDV system to operate in dense fogs.

Cliff, W. C.↗
NASA NTRS1974

The measurement of the size distribution of artificial fogs

The size-distribution of the fog droplets at various fog particle concentrations in fog chamber was determined by two methods: (1) the Stokes' velocity photographic method and (2) using the active scattering particle spectrometer. It is shown that the two techniques are accurate in two different ranges of particle size - the former in the radii range (0.1 micrometers to 10.0 micrometers), and the latter for radii greater than 10.0 micrometers. This was particularly true for high particle concentration, low visibility fogs.

Deepak, A.↗
NASA NTRS1973

Three dimensional laser Doppler velocimeter turbulence measurements in a pipe flow

The mean and turbulent u, v, and w components of a gaseous fully developed turbulent pipe flow were measured with a laser Doppler velocimeter system. Measurements of important system parameters are presented and discussed in relation to the measurement accuracy. Simultaneous comparisons of the laser Doppler and hot wire anemometer measurements in the turbulent flow provided evidence that the two systems were responding to the same flow phenomena.

Fuller, C. E., III↗
NASA NTRS1972

A laser velocimeter for remote wind sensing.

A CW carbon dioxide laser Doppler radar has been developed and applied to remote measurement of atmospheric wind velocity and turbulence. The carbon dioxide laser illuminates residual particulate matter in the atmosphere. Radiation scattered by these particles is homodyned with a local oscillator to provide the Doppler signal. The performance of the instrument is verified by comparison of wind velocity data recorded simultaneously by the laser Doppler system and a cup-anemometer wind-vane system. All data comparisons indicate very close agreement of the two systems. Data inconsistencies are within the accuracy limitations of the conventional anemometer system. The range of the laser Doppler system during these tests was confined to approximately 30 m. Laser Doppler wind velocity data were observed at ranges exceeding 300 m; however, no conventional anemometer was set up at these ranges for data comparisons.

Lawrence, T. R.↗
NASA NTRS1972

Application of a laser velocimeter for remote wind velocity and turbulence measurements.

Demonstration of the utility of a laser Doppler-type instrument for studying the velocity structure of atmospheric flow. Its value lies in the fact that regions of interest can be sensed remotely without introducing a perturbation at that location. The absence of moving mechanical parts results in a sensor with high frequency response capability. Regions of the atmosphere to be monitored can be selected simply by deflecting a mirror and adjusting the position of the focusing lens.

Lawrence, T. R.↗