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  • 1
    Publication Date: 2011-08-24
    Description: The edge technique, a new method for measuring small frequency shifts, is described. The technique allows high-accuracy measurement of atmospheric winds (0.2-1 m/s) with a high vertical resolution (10 m) using currently available technology. With the edge technique, a lidar system can be used to obtain range resolved measurements of the wind in the atmosphere from the ground, aircraft, or spaceborne platforms. The edge technique can be used with different lasers over a broad range of wavelengths.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: In: Image understanding for aerospace applications; Proceedings of the Meeting, Munich, Germany, June 13, 14, 1991 (A93-33082 12-35); p. 144-157.
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  • 2
    Publication Date: 2011-08-24
    Description: The paper describes the theory of the edge technique, a powerful method for the detection and measurement of small frequency shifts. It can be employed with a lidar to obtain range-resolved measurements of wind with high accuracy and high vertical resolution. The technique can be applied to measure wind with a lidar by using either the aerosol or molecular backscattered signal. Simulations for a ground-based lidar at 1.06 micron using reasonable instrumental parameters show an accuracy of the vector components of the wind which is better than 0.5 m/s from the ground to an altitude of 20 km for a 100-m vertical resolution and a 100-shot average.
    Keywords: LASERS AND MASERS
    Type: Applied Optics (ISSN 0003-6935); 31; 21, J
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  • 3
    Publication Date: 2006-10-26
    Description: Thin copper shell and wire-wound conical radiation detectors for measuring radiant flux
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 4
    Publication Date: 2011-08-16
    Description: Multispectral scanner and data system with 24 channels for NASA C-130 earth resources survey aircraft
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ; 121- 147. (
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  • 5
    Publication Date: 2011-08-18
    Description: A new two-wavelength lidar technique for remotely measuring the pressure profile using the trough absorption region between two strong lines in the oxygen A band is described. The theory of integrated vertical path, differential ranging, and horizontal-path pressure measurements is given, with methods to desensitize and correct for temperature effects. The properties of absorption troughs are described and shown to reduce errors due to laser frequency jitter by up to two orders of magnitude. A general analysis, including laser bandwidth effects, demonstrates that pressure measurements with an integrated-vertical-path technique are typically fifty times more accurate than with a differential ranging technique. Simulations show 0.1-0.3 percent accuracy for ground and Shuttle-based pressure-profile and surface-pressure experiments.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 22; 3759-377
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  • 6
    Publication Date: 2011-08-18
    Description: The spectrum of weather and climate needs for lidar observations from space is discussed. This paper focuses mainly on the requirements for winds, temperature, moisture, and pressure. Special emphasis is given to the need for wind observations, and it is shown that winds are required to depict realistically all atmospheric scales in the tropics and the smaller scales at higher latitudes, where both temperature and wind profiles are necessary. The need for means to estimate air-sea exchanges of sensible and latent heat also is noted. Lidar can aid here by measurement of the slope of the boundary layer. Recent theoretical feasibility studies concerning the profiling of temperature, pressure, and humidity by differential absorption lidar (DIAL) from space and expected accuracies are reviewed. Initial ground-based trials provide support for these approaches and also indicate their direct applicability to path-average temperature measurements near the surface. An alternative approach to Doppler lidar wind measurements also is presented. The concept involves the measurement of the displacement of the aerosol backscatter pattern, at constant height, between two successive scans of the same area, one ahead of the spacecraft and the other behind it, a few minutes later. Finally, an integrated space lidar system capable of measuring temperature, pressure, humidity, and winds which combines the DIAL methods with the aerosol pattern displacement concept is described briefly.
    Keywords: METEOROLOGY AND CLIMATOLOGY
    Type: American Meteorological Society; vol. 62
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  • 7
    Publication Date: 2011-08-18
    Description: A dual-frequency system is used to demonstrate the measurement of atmospheric temperature, through laser energy absorption monitoring at the center of an O2 resonant absorption line near 770 nm. It is shown that the average temperature of a 1 km path can be determined within 1.0 C, with a noise level of 0.3 C. An iterative algebraic expression for this method was developed, and is shown to be applicable in the troposphere; the effects of pressure and humidity on temperature determination were made clear by the algorithm and found to be small near the earth's surface.
    Keywords: GEOPHYSICS
    Type: Applied Optics; 20; June 1
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  • 8
    Publication Date: 2011-08-18
    Description: The present investigation is concerned with differential absorption lidar techniques for remotely measuring the atmospheric temperature and pressure profile, surface pressure, and cloud top pressure-height. The procedure used in determining the pressure is based on the conduction of high-resolution measurements of absorption in the wings of lines in the oxygen A band. Absorption with respect to these areas is highly pressure sensitive in connection with the mechanism of collisional line broadening. The method of temperature measurement utilizes a determination of the absorption at the center of a selected line in the oxygen A band which originates from a quantum state with high ground state energy.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 9
    Publication Date: 2011-08-18
    Description: A lidar instrument based on pulsed frequency-doubled carbon-dioxide lasers has been used at 4.88 microns for remote sensing of atmospheric carbon dioxide. A tunable-diode laser spectrometer provided the high-resolution spectroscopic data on carbon-dioxide line strength and line broadening needed for an accurate differential absorption measurement. Initial field measurements are presented, and instrument improvements necessary for accurate carbon dioxide measurement are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 22; Sept. 1
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  • 10
    Publication Date: 2016-06-07
    Description: Real-time measurements of atmospheric absorption spectra are displayed and used to precisely calibrate and fix the frequency of an Alexandrite laser to specific oxygen absorption features for airborne Differential Absorption Lidar (DIAL) measurements of atmospheric pressure and temperature. The DIAL system used contains two narrowband tunable Alexandrite lasers: one is electronically scanned to tune to oxygen absorption features for on-line signals while the second is used to obtain off-line (nonabsorbed) atmospheric return signals. The lidar operator may select the number of shots to be averaged, the altitude, and altitude interval over which the signals are averaged using single key stroke commands. The operator also determines exactly which oxygen absorption lines are scanned by comparing the line spacings and relative strengths with known line parameters, thus calibrating the laser wavelength readout. The system was used successfully to measure the atmospheric pressure profile on the first flights of this lidar, November 20, and December 9, 1985, aboard the NASA Wallops Electra aircraft.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Langley Research Center 13th International Laser Radar Conference; 1 p
    Format: application/pdf
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