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  • 1
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    Data Processing and Analysis Approach to Retrieve Carbon Dioxide Weighted-Column Mixing Ratio and 2- $mu$ m Reflectance With an Airborne Laser Absorption Spectrometer (2019)
    Institute of Electrical and Electronics Engineers
    Details
    Publication Date: 2019-02-01
    Print ISSN: 0196-2892
    Electronic ISSN: 1558-0644
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Institute of Electrical and Electronics Engineers
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    PAPER CURRENT
  • 2
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    Airborne Laser Absorption Spectrometer Measurements of Atmospheric CO2 Column Mole Fractions: Source and Sink Detection and Environmental Impacts on Retrievals (2014)
    American Meteorological Society
    Details
    Publication Date: 2014-02-01
    Description: This paper provides atmospheric CO2 column abundance measurement results from a summer 2011 series of flights of a 2.05-μm laser absorption spectrometer on the NASA DC-8 research aircraft. The integrated path differential absorption (IPDA) method is used for the CO2 column mole fraction retrievals. This instrument and the data analysis methodology developed to achieve retrievals over complex terrain and variable atmospheric conditions provide insight into the capabilities of the IPDA method for both airborne measurements and future global-scale CO2 measurements from low-Earth orbit pertinent to the proposed NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. Demonstrated in this paper is the capability to measure CO2 drawdown caused by crop activity during a midday flight over the U.S. upper Midwest area. In addition, an example is provided of high spatial resolution measurements of CO2 plumes from individual stack clusters of the Four Corners Power Plant in northwestern New Mexico. Complex terrain, the spectral properties of the aboveground scatterers, and potential cloud contamination are factors that complicate the column abundance retrieval. The impacts of these factors and various means of minimizing these influences in the retrievals are discussed.
    Print ISSN: 0739-0572
    Electronic ISSN: 1520-0426
    Topics: Geography , Geosciences , Physics
    Published by American Meteorological Society
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    PAPER CURRENT
  • 3
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    Design and Operational Characteristics of the Shuttle Coherent Wind Lidar (1998)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: NOAA has identified the measurement of atmospheric wind velocities as one of the key unmet data sets for its next generation of sensing platforms. The merits of coherent lidars for the measurement of atmospheric winds from space platforms have been widely recognized; however, it is only recently that several key technologies have advanced to a point where a compact, high fidelity system could be created. Advances have been made in the areas of the diode-pumped, eye-safe, solid state lasers and room temperature, wide bandwidth, semiconductor detectors operating in the near-infrared region. These new lasers can be integrated into efficient and compact optical systems creating new possibilities for the development of low-cost, reliable, and compact coherent lidar systems for wind measurements. Over the past five years, the University of Alabama in Huntsville (UAH) has been working toward further advancing the solid state coherent lidar technology for the measurement of atmospheric winds from space. As part of this effort, UAH had established the design characteristics and defined the expected performance for three different proposed space-based instruments: a technology demonstrator, an operational prototype, and a 7-year lifetime operational instrument. SPARCLE is an ambitious project that is intended to evaluate the suitability of coherent lidar for wind measurements, demonstrate the maturity of the technology for space application, and provide a useable data set for model development and validation. This paper describes the SPARCLE instrument's major physical and environmental design constraints, optical and mechanical designs, and its operational characteristics.
    Keywords: Instrumentation and Photography
    Type: Nineteenth International Laser Radar Conference; Part 2; 703-706; NASA/CP-1998-207671/PT2
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Considerations for Designing a Space Based Coherent Doppler Lidar (1999)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: An orbiting coherent Doppler lidar for measuring winds is required to provide two basic pieces of data to the user community. The first is the line of sight wind velocity and the second is knowledge of the position at which the measurement was made. In order to provide this information in regions of interest the instrument is also required to have a certain backscatter sensitivity level. This paper outlines some of the considerations necessary in designing a coherent Doppler lidar for this purpose.
    Keywords: Instrumentation and Photography
    Type: Tenth Biennial Coherent Laser Radar Technology and Applications Conference; 302-305; NASA/CP-1999-209758
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Computer modeling of pulsed CO2 lasers for lidar applications (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The experimental results will enable a comparison of the numerical code output with experimental data. This will ensure verification of the validity of the code. The measurements were made on a modified commercial CO2 laser. Results are listed as following. (1) The pulse shape and energy dependence on gas pressure were measured. (2) The intrapulse frequency chirp due to plasma and laser induced medium perturbation effects were determined. A simple numerical model showed quantitative agreement with these measurements. The pulse to pulse frequency stability was also determined. (3) The dependence was measured of the laser transverse mode stability on cavity length. A simple analysis of this dependence in terms of changes to the equivalent fresnel number and the cavity magnification was performed. (4) An analysis was made of the discharge pulse shape which enabled the low efficiency of the laser to be explained in terms of poor coupling of the electrical energy into the vibrational levels. And (5) the existing laser resonator code was changed to allow it to run on the Cray XMP under the new operating system.
    Keywords: LASERS AND MASERS
    Type: NASA(MSFC FY91 Global Scale Atmospheric Processes Research Program Review; p 61-62
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Computer modeling of pulsed CO2 lasers for lidar applications (1993)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The object of this effort is to develop code to enable the accurate prediction of the performance of pulsed transversely excited (TE) CO2 lasers prior to their construction. This is of particular benefit to the NASA Laser Atmospheric Wind Sounder (LAWS) project. A benefit of the completed code is that although developed specifically for the pulsed CO2 laser much of the code can be modified to model other laser systems of interest to the lidar community. A Boltzmann equation solver has been developed which enables the electron excitation rates for the vibrational levels of CO2 and N2, together with the electron ionization and attachment coefficients to be determined for any CO2 laser gas mixture consisting of a combination of CO2, N2, CO, He and CO. The validity of the model has been verified by comparison with published material. The results from the Boltzmann equation solver have been used as input to the laser kinetics code which is currently under development. A numerical code to model the laser induced medium perturbation (LIMP) arising from the relaxation of the lower laser level has been developed and used to determine the effect of LIMP on the frequency spectrum of the LAWS laser output pulse. The enclosed figures show representative results for a laser operating at 0.5 atm. with a discharge cross-section of 4.5 cm to produce a 20 J pulse with aFWHM of 3.1 microns. The first four plots show the temporal evolution of the laser pulse power, energy evolution, LIMP frequency chirp and electric field magnitude. The electric field magnitude is taken by beating the calculated complex electric field and beating it with a local oscillator signal. The remaining two figures show the power spectrum and energy distribution in the pulse as a function of the varying pulse frequency. The LIMP theory has been compared with experimental data from the NOAA Windvan Lidar and has been found to be in good agreement.
    Keywords: LASERS AND MASERS
    Type: NASA. Marshall Space Flight Center, NASA(MSFC FY92 Earth Science and Applications Program Research Review; p 121-124
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Space based lidar shot pattern targeting strategies for small targets such as streams (2001)
    In:  Other Sources
    Details
    Publication Date: 2018-06-11
    Description: An analysis of the effectiveness of four different types of lidar shot distribution is conducted to determine which is best for concentrating shots in a given location. A simple preemptive targeting strategy is found to work as adequately as a more involved dynamic strategy for most target sizes considered.
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Direct Global Measurements of Tropspheric Winds Employing a Simplified Coherent Laser Radar using Fully Scalable Technology and Technique (1996)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Innovative designs of a space-based laser remote sensing 'wind machine' are presented. These designs seek compatibility with the traditionally conflicting constraints of high scientific value and low total mission cost. Mission cost is reduced by moving to smaller, lighter, more off-the-shelf instrument designs which can be accommodated on smaller launch vehicles.
    Keywords: Meteorology and Climatology
    Type: NASA-CR-202582 , NAS 1.26:202582 , Faster, Cheaper, Smaller Space Science Instruments; United States
    Format: application/pdf
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  • 9
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    Laser/lidar analysis and testing (1994)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Section 1 of this report details development of a model of the output pulse frequency spectrum of a pulsed transversely excited (TE) CO2 laser. In order to limit the computation time required, the model was designed around a generic laser pulse shape model. The use of such a procedure allows many possible laser configurations to be examined. The output pulse shape is combined with the calculated frequency chirp to produce the electric field of the output pulse which is then computationally mixed with a local oscillator field to produce the heterodyne beat signal that would fall on a detector. The power spectral density of this heterodyne signal is then calculated. Section 2 reports on a visit to the LAWS laser contractors to measure the performance of the laser breadboards. The intention was to acquire data using a digital oscilloscope so that it could be analyzed. Section 3 reports on a model developed to assess the power requirements of a 5J LAWS instrument on a Spot MKII platform in a polar orbit. The performance was assessed for three different latitude dependent sampling strategies.
    Keywords: LASERS AND MASERS
    Type: NASA-CR-193954 , NAS 1.26:193954
    Format: application/pdf
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  • 10
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    Potential Pitfalls Related to Space-Based Lidar Remote Sensing of the Earth with an Emphasis on Wind Measurement (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A collection of issues is discussed that are potential pitfalls, if handled incorrectly, for earth-orbiting lidar remote sensing instruments. These issues arise due to the long target ranges, high lidar-to-target relative velocities, low signal levels, use of laser scanners, and other unique aspects of using lasers in earth orbit. Consequences of misunderstanding these topics range from minor inconvenience to improper calibration to total failure. We will focus on wind measurement using coherent detection Doppler lidar, but many of the potential pitfalls apply also to noncoherent lidar wind measurement, and to measurement of parameters other than wind. Each area will be identified as to its applicability.
    Keywords: Earth Resources and Remote Sensing
    Type: Remote Sensing of the Atmosphere, Environment, and Space; Oct 09, 2000 - Oct 12, 2000; Sendai; Japan
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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