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Sample records for absorption lidar technique

  1. Differential absorption lidar technique for measurement of the atmospheric pressure profile

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Weng, C. Y.

    1983-01-01

    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.

  2. NONLINEAR-APPROXIMATION TECHNIQUE FOR DETERMINING VERTICAL OZONE-CONCENTRATION PROFILES WITH A DIFFERENTIAL-ABSORPTION LIDAR

    EPA Science Inventory

    A new technique is presented for the retrieval of ozone concentration profiles from backscattered signals obtained by a multi-wavelength differential-absorption lidar (DIAL). The technique makes it possible to reduce erroneous local fluctuations induced in the ozone-concentration...

  3. Investigation of potential of differential absorption Lidar techniques for remote sensing of atmospheric pollutants

    NASA Technical Reports Server (NTRS)

    Butler, C. F.; Shipley, S. T.; Allen, R. J.

    1981-01-01

    The NASA multipurpose differential absorption lidar (DIAL) system uses two high conversion efficiency dye lasers which are optically pumped by two frequency-doubled Nd:YAG lasers mounted rigidly on a supporting structure that also contains the transmitter, receiver, and data system. The DIAL system hardware design and data acquisition system are described. Timing diagrams, logic diagrams, and schematics, and the theory of operation of the control electronics are presented. Success in obtaining remote measurements of ozone profiles with an airborne systems is reported and results are analyzed.

  4. COMPENSATIONAL THREE-WAVELENGTH DIFFERENTIAL-ABSORPTION LIDAR TECHNIQUE FOR REDUCING THE INFLUENCE OF DIFFERENTIAL SCATTERING ON OZONE-CONCENTRATION MEASUREMENTS.

    EPA Science Inventory

    A three-wavelength differential-absorption lidar (DIAL) technique for the UV spectral region is presented that reduces the influence of aerosol differential scattering on measured O3-concentration profiles. The principal advantage of this approach is that, to a good first approxi...

  5. Ozone differential absorption lidar algorithm intercomparison.

    PubMed

    Godin, S; Carswell, A I; Donovan, D P; Claude, H; Steinbrecht, W; McDermid, I S; McGee, T J; Gross, M R; Nakane, H; Swart, D P; Bergwerff, H B; Uchino, O; von der Gathen, P; Neuber, R

    1999-10-20

    An intercomparison of ozone differential absorption lidar algorithms was performed in 1996 within the framework of the Network for the Detection of Stratospheric Changes (NDSC) lidar working group. The objective of this research was mainly to test the differentiating techniques used by the various lidar teams involved in the NDSC for the calculation of the ozone number density from the lidar signals. The exercise consisted of processing synthetic lidar signals computed from simple Rayleigh scattering and three initial ozone profiles. Two of these profiles contained perturbations in the low and the high stratosphere to test the vertical resolution of the various algorithms. For the unperturbed profiles the results of the simulations show the correct behavior of the lidar processing methods in the low and the middle stratosphere with biases of less than 1% with respect to the initial profile to as high as 30 km in most cases. In the upper stratosphere, significant biases reaching 10% at 45 km for most of the algorithms are obtained. This bias is due to the decrease in the signal-to-noise ratio with altitude, which makes it necessary to increase the number of points of the derivative low-pass filter used for data processing. As a consequence the response of the various retrieval algorithms to perturbations in the ozone profile is much better in the lower stratosphere than in the higher range. These results show the necessity of limiting the vertical smoothing in the ozone lidar retrieval algorithm and questions the ability of current lidar systems to detect long-term ozone trends above 40 km. Otherwise the simulations show in general a correct estimation of the ozone profile random error and, as shown by the tests involving the perturbed ozone profiles, some inconsistency in the estimation of the vertical resolution among the lidar teams involved in this experiment.

  6. Analysis of diffential absorption lidar technique for measurements of anhydrous hydrogen chloride from solid rocket motors using a deuterium fluoride laser

    NASA Technical Reports Server (NTRS)

    Bair, C. H.; Allario, F.

    1977-01-01

    An active optical technique (differential absorption lidar (DIAL)) for detecting, ranging, and quantifying the concentration of anhydrous HCl contained in the ground cloud emitted by solid rocket motors (SRM) is evaluated. Results are presented of an experiment in which absorption coefficients of HCl were measured for several deuterium fluoride (DF) laser transitions demonstrating for the first time that a close overlap exists between the 2-1 P(3) vibrational transition of the DF laser and the 1-0 P(6) absorption line of HCl, with an absorption coefficient of 5.64 (atm-cm) to the -1 power. These measurements show that the DF laser can be an appropriate radiation source for detecting HCl in a DIAL technique. Development of a mathematical computer model to predict the sensitivity of DIAL for detecting anhydrous HCl in the ground cloud is outlined, and results that assume a commercially available DF laser as the radiation source are presented.

  7. Development of a 2-micron Pulsed Differential Absorption Lidar for Atmospheric CO2 Concentration Measurement by Direct Detection Technique

    NASA Astrophysics Data System (ADS)

    Yu, J.; Singh, U. N.; Petros, M.; Bai, Y.

    2011-12-01

    Researchers at NASA Langley Research Center are developing a 2-micron Pulsed Differential Absorption Lidar instrument for ground and airborne measurements via direct detection method. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capbility by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. A key component of the CO2 DIAL system, transceiver, is an existing, airborne ready, robust hardware which can provide 250mJ at 10Hz with double pulse format specifically designed for DIAL instrument. The exact wavelengths of the transceiver are controlled by well defined CW seed laser source to provide the required injection source for generating on-and-off line wavelength pulses sequentially. The compact, rugged, highly reliable transceiver is based on the unique Ho:Tm:YLF high-energy 2-micron pulsed laser technology. All the optical mounts are custom designed and have space heritage. They are designed to be adjustable and lockable and hardened to withstand vibrations that can occur in airborne operation. For the direct detection lidar application, a large primary mirror size is preferred. A 14 inch diameter telescope will be developed for this program. The CO2 DIAL/IPDA system requires many electronic functions to operate. These include diode, RF, seed laser, and PZT drivers; injection seeding detection and control; detector power supplies; and analog inputs to sample various sensors. Under NASA Laser Risk Reduction Program (LRRP), a control unit Compact Laser Electronics (CLE), is developed for the controlling the coherent wind lidar transceiver. Significant modifications and additions are needed to update it for CO2 lidar controls. The data acquisition system was built for ground CO2 measurement demonstration. The software will be updated for

  8. Lidar techniques for environmental and ecological monitoring

    NASA Astrophysics Data System (ADS)

    Svanberg, Sune

    2015-04-01

    An overview of optical probing of the atmosphere will be given, where mostly active remote- sensing techniques of the laser-radar type will be covered, but also some passive techniques employing ambient radiation. Atmospheric objects of quite varying sizes can be studied. Mercury is the only pollutant in atomic form in the atmosphere, while other pollutants are either molecular or in particle form. Light detection and ranging (Lidar) techniques allow three-dimensional mapping of such constituents, and examples from atmospheric lidar work in Lund and in Guangzhou will be given. Recently, much larger lidar targets have been studied. Monitoring of flying insects and birds is of considerable ecological interest, and several projects have been pursued in collaboration with biologists. Mostly, elastic backscattering and fluorescence techniques are employed. Some references to recent activities by the author and his colleagues are given below. [1] Z.G. Guan, L. Mei, P. Lundin, G. Somesfalean, and S. Svanberg, Vertical Lidar Sounding of Air Pollutants in a Major Chinese City, Appl. Phys. B 101, 465 (2010) [2] L. Mei, G.Y. Zhou and S. Svanberg, Differential Absorption Lidar System Employed for Background Atomic Mercury Vertical Profiling in South China, Lasers Opt. Eng. 55, 128 (2013) [3] Z.G. Guan, M. Brydegaard, P. Lundin, M. Wellenreuther, E. Svensson, and S. Svanberg, Insect Monitoring with Fluorescence LIDAR techniques - Field experiments, Appl. Optics 48, 5668 (2010) [4] A. Runemark, M. Wellereuther, H. Jayaweera, S. Svanberg and M. Brydegaard, Rare Events in Remote Dark Field Spectroscopy: An Ecological Case study of Insects, IEEE JSTQE 18, 1573 (2011) [5] L. Mei, Z.G. Guan, H.J. Zhou, J. Lv, Z.R. Zhu, J.A. Cheng, F.J. Chen, C. Löfstedt, S. Svanberg, and G. Somesfalean, Agricultural Pest Monitoring using Fluorescence Lidar Techniques, Applied Physics B 106, 733 (2011) [6] P. Lundin, P. Samuelsson, S. Svanberg, A. Runemark, S. Åkesson, and M. Brydegaard, Remote

  9. Pulsed airborne lidar measurements of atmospheric CO2 column absorption

    NASA Astrophysics Data System (ADS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Kawa, S. Randoph; Biraud, Sebastien

    2010-11-01

    ABSTRACT We report initial measurements of atmospheric CO2 column density using a pulsed airborne lidar operating at 1572 nm. It uses a lidar measurement technique being developed at NASA Goddard Space Flight Center as a candidate for the CO2 measurement in the Active Sensing of CO2 Emissions over Nights, Days and Seasons (ASCENDS) space mission. The pulsed multiple-wavelength lidar approach offers several new capabilities with respect to passive spectrometer and other lidar techniques for high-precision CO2 column density measurements. We developed an airborne lidar using a fibre laser transmitter and photon counting detector, and conducted initial measurements of the CO2 column absorption during flights over Oklahoma in December 2008. The results show clear CO2 line shape and absorption signals. These follow the expected changes with aircraft altitude from 1.5 to 7.1 km, and are in good agreement with column number density estimates calculated from nearly coincident airborne in-situ measurements.

  10. Pulsed Airborne Lidar Measurements of C02 Column Absorption

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Weaver, Clark J.; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William E.; Rodriquez, Michael; Browell, Edward V.

    2011-01-01

    We report on airborne lidar measurements of atmospheric CO2 column density for an approach being developed as a candidate for NASA's ASCENDS mission. It uses a pulsed dual-wavelength lidar measurement based on the integrated path differential absorption (IPDA) technique. We demonstrated the approach using the CO2 measurement from aircraft in July and August 2009 over four locations. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The 2009 measurements have been analyzed in detail and the results show approx.1 ppm random errors for 8-10 km altitudes and approx.30 sec averaging times. Airborne measurements were also made in 2010 with stronger signals and initial analysis shows approx. 0.3 ppm random errors for 80 sec averaging times for measurements at altitudes> 6 km.

  11. Differential absorption lidar measurements of atmospheric temperature and pressure profiles

    NASA Technical Reports Server (NTRS)

    Korb, C. L.

    1981-01-01

    The theory and methodology of using differential absorption lidar techniques for the remote measurement of atmospheric pressure profiles, surface pressure, and temperature profiles from ground, air, and space-based platforms are presented. Pressure measurements are effected by means of high resolution measurement of absorption at the edges of the oxygen A band lines where absorption is pressure dependent due to collisional line broadening. Temperature is assessed using measurements of the absorption at the center of the oxygen A band line originating from a quantum state with high ground state energy. The population of the state is temperature dependent, allowing determination of the temperature through the Boltzmann term. The results of simulations of the techniques using Voigt profile and variational analysis are reported for ground-based, airborne, and Shuttle-based systems. Accuracies in the 0.5-1.0 K and 0.1-0.3% range are projected.

  12. Towards quantitative atmospheric water vapor profiling with differential absorption lidar.

    PubMed

    Dinovitser, Alex; Gunn, Lachlan J; Abbott, Derek

    2015-08-24

    Differential Absorption Lidar (DIAL) is a powerful laser-based technique for trace gas profiling of the atmosphere. However, this technique is still under active development requiring precise and accurate wavelength stabilization, as well as accurate spectroscopic parameters of the specific resonance line and the effective absorption cross-section of the system. In this paper we describe a novel master laser system that extends our previous work for robust stabilization to virtually any number of multiple side-line laser wavelengths for the future probing to greater altitudes. In this paper, we also highlight the significance of laser spectral purity on DIAL accuracy, and illustrate a simple re-arrangement of a system for measuring effective absorption cross-section. We present a calibration technique where the laser light is guided to an absorption cell with 33 m path length, and a quantitative number density measurement is then used to obtain the effective absorption cross-section. The same absorption cell is then used for on-line laser stabilization, while microwave beat-frequencies are used to stabilize any number of off-line lasers. We present preliminary results using ∼300 nJ, 1 μs pulses at 3 kHz, with the seed laser operating as a nanojoule transmitter at 822.922 nm, and a receiver consisting of a photomultiplier tube (PMT) coupled to a 356 mm mirror. PMID:26368258

  13. Towards quantitative atmospheric water vapor profiling with differential absorption lidar.

    PubMed

    Dinovitser, Alex; Gunn, Lachlan J; Abbott, Derek

    2015-08-24

    Differential Absorption Lidar (DIAL) is a powerful laser-based technique for trace gas profiling of the atmosphere. However, this technique is still under active development requiring precise and accurate wavelength stabilization, as well as accurate spectroscopic parameters of the specific resonance line and the effective absorption cross-section of the system. In this paper we describe a novel master laser system that extends our previous work for robust stabilization to virtually any number of multiple side-line laser wavelengths for the future probing to greater altitudes. In this paper, we also highlight the significance of laser spectral purity on DIAL accuracy, and illustrate a simple re-arrangement of a system for measuring effective absorption cross-section. We present a calibration technique where the laser light is guided to an absorption cell with 33 m path length, and a quantitative number density measurement is then used to obtain the effective absorption cross-section. The same absorption cell is then used for on-line laser stabilization, while microwave beat-frequencies are used to stabilize any number of off-line lasers. We present preliminary results using ∼300 nJ, 1 μs pulses at 3 kHz, with the seed laser operating as a nanojoule transmitter at 822.922 nm, and a receiver consisting of a photomultiplier tube (PMT) coupled to a 356 mm mirror.

  14. A Two Micron Coherent Differential Absorption Lidar Development

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo C.; Koch, Grady J.; Beyon, Jeffrey Y.; VanValkenburg, Randal L.; Kavaya, Michael J.; Singh, Upendra N.

    2010-01-01

    A pulsed, 2-micron coherent Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO2 profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop. Keywords: Differential Absorption Lidar, Near Infrared Laser,

  15. Lidar.

    PubMed

    Collis, R T

    1970-08-01

    Lidar uses laser energy in radar fashion to observe atmospheric backscattering as a function of range. The concomitant attenuation of energy along the intervening path complicates the evaluation of the observations, but even on a qualitative basis the delineation of clouds or of structure in the apparently clear air is of considerable value in operational meteorology and atmospheric research. Under certain conditions the atmosphere's optical parameters may be evaluated and related to meteorologically significant characteristics. Advanced techniques based on resonant absorption and Raman shift back- scattering are briefly noted. The current attainment and future prospects of lidar are reviewed.

  16. Stabilized master laser system for differential absorption lidar.

    PubMed

    Dinovitser, Alex; Hamilton, Murray W; Vincent, Robert A

    2010-06-10

    Wavelength accuracy and stability are key requirements for differential absorption lidar (DIAL). We present a control and timing design for the dual-stabilized cw master lasers in a pulsed master-oscillator power-amplifier configuration, which forms a robust low-cost water-vapor DIAL transmitter system. This design operates at 823 nm for water-vapor spectroscopy using Fabry-Perot-type laser diodes. However, the techniques described could be applied to other laser technologies at other wavelengths. The system can be extended with additional off-line or side-line wavelengths. The on-line master laser is locked to the center of a water absorption line, while the beat frequency between the on-line and the off-line is locked to 16 GHz using only a bandpass microwave filter and low-frequency electronics. Optical frequency stabilities of the order of 1 MHz are achieved.

  17. Surface ozone measurements using differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Jain, Sohan L.; Arya, B. C.; Ghude, Sachin D.; Arora, Arun K.; Sinha, Randhir K.

    2005-01-01

    Human activities have been influencing the global atmosphere since the beginning of the industrial era, causing shifts from its natural state. The measurements have shown that tropospheric ozone is increasing gradually due to anthropogenic activities. Surface ozone is a secondary pollutant, its concentration in lower troposphere depends upon its precursors (CO, CH4, non methane hydrocarbons, NOx) as well as weather and transport phenomenon. The surface ozone exceeding the ambient air quality standard is health hazard to human being, animal and vegetation. The regular information of its concentrations on ground levels is needed for setting ambient air quality objectives and understanding photo chemical air pollution in urban areas. A Differential Absorption Lidar (DIAL) using a tunable CO2 laser has been designed and developed at National Physical Laboratory, New Delhi, to monitor water vapour, surface ozone, ammonia, ethylene etc. Some times ethylene and surface ozone was found to be more than 40 ppb and 140 ppb respectively which is a health hazard. Seasonal variation in ozone concentrations shows maximum in the months of summer and autumn and minimum in monsoon and winter months. In present communication salient features of experimental set up and results obtained will be presented in detail.

  18. Two-frequency lidar inversion technique.

    PubMed

    Potter, J F

    1987-04-01

    An analytical technique for inverting lidar returns is proposed and tested on simulated data. The technique requires simultaneous lidar returns at two frequencies and is based on the assumptions that (1) the ratio of backscatter to extinction is independent of position along the lidar line and (2) the ratio of the extinction coefficients at the two frequencies is independent of position along the lidar line. These assumptions are met if molecular scattering can be neglected and the aerosol is composed of the same kind of particle at all points along the lidar line. The simulated data corresponded to a lidar line of 1.0-km length with a uniform aerosol having a total optical depth of 1.0. The quantities determined by the analysis are the total transmittance T, the ratio between the extinction coefficients at the two frequencies k, and the extinction profiles at the two frequencies. The errors in these quantities are critically dependent on the noise level in the data. When 100 shots were averaged to reduce noise, the rms errors in T and k were 1.93 and 1.54%, respectively, and the maximum error in the extinction profile was 6%. An appendix describes possible extensions to include molecular scattering.

  19. Coherent differential absorption lidar measurements of CO2.

    PubMed

    Koch, Grady J; Barnes, Bruce W; Petros, Mulugeta; Beyon, Jeffrey Y; Amzajerdian, Farzin; Yu, Jirong; Davis, Richard E; Ismail, Syed; Vay, Stephanie; Kavaya, Michael J; Singh, Upendra N

    2004-09-10

    A differential absorption lidar has been built to measure CO2 concentration in the atmosphere. The transmitter is a pulsed single-frequency Ho:Tm:YLF laser at a 2.05-microm wavelength. A coherent heterodyne receiver was used to achieve sensitive detection, with the additional capability for wind profiling by a Doppler technique. Signal processing includes an algorithm for power measurement of a heterodyne signal. Results show a precision of the CO2 concentration measurement of 1%-2% 1sigma standard deviation over column lengths ranging from 1.2 to 2.8 km by an average of 1000 pulse pairs. A preliminary assessment of instrument sensitivity was made with an 8-h-long measurement set, along with correlative measurements with an in situ sensor, to determine that a CO2 trend could be detected.

  20. Calibration Technique for Polarization-Sensitive Lidars

    NASA Technical Reports Server (NTRS)

    Alvarez, J. M.; Vaughan, M. A.; Hostetler, C. A.; Hung, W. H.; Winker, D. M.

    2006-01-01

    Polarization-sensitive lidars have proven to be highly effective in discriminating between spherical and non-spherical particles in the atmosphere. These lidars use a linearly polarized laser and are equipped with a receiver that can separately measure the components of the return signal polarized parallel and perpendicular to the outgoing beam. In this work we describe a technique for calibrating polarization-sensitive lidars that was originally developed at NASA s Langley Research Center (LaRC) and has been used continually over the past fifteen years. The procedure uses a rotatable half-wave plate inserted into the optical path of the lidar receiver to introduce controlled amounts of polarization cross-talk into a sequence of atmospheric backscatter measurements. Solving the resulting system of nonlinear equations generates the system calibration constants (gain ratio, G, and offset angle, theta) required for deriving calibrated measurements of depolarization ratio from the lidar signals. In addition, this procedure also determines the mean depolarization ratio within the region of the atmosphere that is analyzed. Simulations and error propagation studies show the method to be both reliable and well behaved. Operational details of the technique are illustrated using measurements obtained as part of Langley Research Center s participation in the First ISCCP Regional Experiment (FIRE).

  1. Lidar techniques for search and rescue

    SciTech Connect

    Cabral, W.L.

    1985-01-01

    Four techniques for using LIDAR in Search and Rescue Operations will be discussed. The topic will include laser retroreflection, laser-induced fluorescence in the visible, laser-induced fluorescence during daylight hours, and laser-induced fluorescence in the uv. These techniques use high-repetition rate lasers at a variety of frequencies to induce either fluorescence in dye markers or retroreflection from plastic corner cubes on life preservers and other emergency markers.

  2. Atmospheric pressure and temperature profiling using near IR differential absorption lidar

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Weng, C. Y.

    1983-01-01

    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.

  3. Broadband Lidar Technique for Precision CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Heaps, William S.

    2008-01-01

    Presented are preliminary experimental results, sensitivity measurements and discuss our new CO2 lidar system under development. The system is employing an erbium-doped fiber amplifier (EDFA), superluminescent light emitting diode (SLED) as a source and our previously developed Fabry-Perot interferometer subsystem as a detector part. Global measurement of carbon dioxide column with the aim of discovering and quantifying unknown sources and sinks has been a high priority for the last decade. The goal of Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission is to significantly enhance the understanding of the role of CO2 in the global carbon cycle. The National Academy of Sciences recommended in its decadal survey that NASA put in orbit a CO2 lidar to satisfy this long standing need. Existing passive sensors suffer from two shortcomings. Their measurement precision can be compromised by the path length uncertainties arising from scattering within the atmosphere. Also passive sensors using sunlight cannot observe the column at night. Both of these difficulties can be ameliorated by lidar techniques. Lidar systems present their own set of problems however. Temperature changes in the atmosphere alter the cross section for individual CO2 absorption features while the different atmospheric pressures encountered passing through the atmosphere broaden the absorption lines. Currently proposed lidars require multiple lasers operating at multiple wavelengths simultaneously in order to untangle these effects. The current goal is to develop an ultra precise, inexpensive new lidar system for precise column measurements of CO2 changes in the lower atmosphere that uses a Fabry-Perot interferometer based system as the detector portion of the instrument and replaces the narrow band laser commonly used in lidars with the newly available high power SLED as the source. This approach reduces the number of individual lasers used in the system from three or more

  4. Diversity imaging techniques in lidar

    NASA Technical Reports Server (NTRS)

    Schultz, K. I.

    1992-01-01

    Diversity imaging techniques have been successfully employed in conventional microwave range-Doppler imaging radars to obtain high resolution images of both natural and man-made targets. These techniques allow microwave radars to achieve image resolution which would otherwise require excessively large antennas. Recent advances in coherent laser radar techniques and signal processing have led to the development of range-Doppler imaging laser radars. While much of the theory and signal processing techniques used in microwave radars can be brought to bear on laser radars, the significant difference in wavelength results in issues peculiar to laser radar systems. Both the fundamental concepts and specific applications of diversity imaging techniques applied to laser radar imaging systems will be discussed. Angle, frequency, and bistatic angle degrees of freedom can be employed in a coherent laser radar imaging system to achieve image resolution which exceeds the traditional Rayleigh criterion associated with the receive aperture. In diversity imaging, angle and frequency degrees of freedom can be used to synthesize an effective aperture providing range and Doppler target information. The ability to vary the bistatic angle provides an additional means of synthesizing an effective aperture. Both simulated and experimentally obtained laser radar images of spinning and/or tumbling objects utilizing both angular and frequency diversity will be presented. In coherent laser radar systems, image quality can be dominated by laser speckle effects. In particular, the signal-to-noise ratio (SNR) of a coherent laser radar image is at most unity in the presence of fully developed speckle. Diversity techniques can be utilized to improve the image SNR; simple incoherent averaging of images utilizing temporal and polarization degrees of freedom can significantly improve image SNR. Both the SNR and image resolution (as defined by the synthetic aperture) contribute to image quality. The

  5. Transmittance ratio constrained retrieval technique for lidar cirrus measurements.

    PubMed

    Su, Jia; McCormick, M Patrick; Liu, Zhaoyan; Lee, Robert B; Leavor, Kevin R; Lei, Liqiao

    2012-05-01

    This letter describes a lidar retrieval technique that uses the transmittance ratio as a constraint to determine an average lidar ratio as well as extinction and backscatter coefficients of transparent cirrus clouds. The cloud transmittance ratio is directly obtained from two adjacent elastic lidar backscatter signals. The technique can be applied to cirrus measurements where neither the molecular scattering dominant signals above and below the cloud layer are found nor cloudfree reference profiles are available. The technique has been tested with simulated lidar signals and applied to backscatter lidar measurements at Hampton University, Hampton, Virginia.

  6. A High Spectral Resolution Lidar Based on Absorption Filter

    NASA Technical Reports Server (NTRS)

    Piironen, Paivi

    1996-01-01

    A High Spectral Resolution Lidar (HSRL) that uses an iodine absorption filter and a tunable, narrow bandwidth Nd:YAG laser is demonstrated. The iodine absorption filter provides better performance than the Fabry-Perot etalon that it replaces. This study presents an instrument design that can be used a the basis for a design of a simple and robust lidar for the measurement of the optical properties of the atmosphere. The HSRL provides calibrated measurements of the optical properties of the atmospheric aerosols. These observations include measurements of aerosol backscatter cross sections, optical depth, backscatter phase function depolarization, and multiple scattering. The errors in the HSRL data are discussed and the effects of different errors on the measured optical parameters are shown.

  7. Light absorption measurements: new techniques.

    PubMed

    Hänel, G; Busen, R; Hillenbrand, C; Schloss, R

    1982-02-01

    A new radiometer is described which simplifies measurement of the radiation supply of solar wavelengths. Two methods of measuring the radiant energy absorbed by aerosol particles are described: A photometric technique is used for particles collected on filters, and a calorimetric technique is used for in situ measurements. Data collected with the radiometer and the light absorption techniques yield the heating rate of the atmosphere due to light absorption by the particles. Sample measurements show substantial atmospheric temperature increases due to absorption, especially in industrial regions.

  8. Differential Absorption Lidar to Measure Subhourly Variation of Tropospheric Ozone Profiles

    NASA Technical Reports Server (NTRS)

    Kuang, Shi; Burris, John F.; Newchurch, Michael J.; Johnson, Steve; Long, Stephania

    2011-01-01

    A tropospheric ozone Differential Absorption Lidar system, developed jointly by The University of Alabama in Huntsville and the National Aeronautics and Space Administration, is making regular observations of ozone vertical distributions between 1 and 8 km with two receivers under both daytime and nighttime conditions using lasers at 285 and 291 nm. This paper describes the lidar system and analysis technique with some measurement examples. An iterative aerosol correction procedure reduces the retrieval error arising from differential aerosol backscatter in the lower troposphere. Lidar observations with coincident ozonesonde flights demonstrate that the retrieval accuracy ranges from better than 10% below 4 km to better than 20% below 8 km with 750-m vertical resolution and 10-min 17 temporal integration.

  9. Differential Absorption Lidar to Measure Sub-Hourly Variation of Tropospheric Ozone Profiles

    NASA Technical Reports Server (NTRS)

    Kuang, Shi; Burris, John F.; Newchurch, Michael J.; Johnson, Steve; Long, Stephanie

    2009-01-01

    A tropospheric ozone Differential Absorption Lidar (DIAL) system, developed jointly by the University of Alabama at Huntsville and NASA, is making regular observations of ozone vertical distributions between 1 and 8 km with two receivers under both daytime and nighttime conditions using lasers at 285 and 291 nm. This paper describes the lidar system and analysis technique with some measurement examples. An iterative aerosol correction procedure reduces the retrieval error arising from differential aerosol backscatter in the lower troposphere. Lidar observations with coincident ozonesonde flights demonstrate that the retrieval accuracy ranges from better than 10% below 4 km to better than 20% below 8 km with 750-m vertical resolution and 10-min temporal integration

  10. Differential absorption lidars for remote sensing of atmospheric pressure and temperature profiles

    NASA Technical Reports Server (NTRS)

    Korb, C. Laurence; Schwemmer, Geary K.; Famiglietti, Joseph; Walden, Harvey; Prasad, Coorg

    1995-01-01

    A near infrared differential absorption lidar technique is developed using atmospheric oxygen as a tracer for high resolution vertical profiles of pressure and temperature with high accuracy. Solid-state tunable lasers and high-resolution spectrum analyzers are developed to carry out ground-based and airborne measurement demonstrations and results of the measurements presented. Numerical error analysis of high-altitude airborne and spaceborne experiments is carried out, and system concepts developed for their implementation.

  11. Altitude range resolution of differential absorption lidar ozone profiles.

    PubMed

    Beyerle, G; McDermid, I S

    1999-02-20

    A method is described for the empirical determination of altitude range resolutions of ozone profiles obtained by differential absorption lidar (DIAL) analysis. The algorithm is independent of the implementation of the DIAL analysis, in particular of the type and order of the vertical smoothing filter applied. An interpretation of three definitions of altitude range resolution is given on the basis of simulations carried out with the Jet Propulsion Laboratory ozone DIAL analysis program, SO3ANL. These definitions yield altitude range resolutions that differ by as much as a factor of 2. It is shown that the altitude resolution calculated by SO3ANL, and reported with all Jet Propulsion Laboratory lidar ozone profiles, corresponds closely to the full width at half-maximum of a retrieved ozone profile if an impulse function is used as the input ozone profile.

  12. Pressure Measurements Using an Airborne Differential Absorption Lidar. Part 1; Analysis of the Systematic Error Sources

    NASA Technical Reports Server (NTRS)

    Flamant, Cyrille N.; Schwemmer, Geary K.; Korb, C. Laurence; Evans, Keith D.; Palm, Stephen P.

    1999-01-01

    Remote airborne measurements of the vertical and horizontal structure of the atmospheric pressure field in the lower troposphere are made with an oxygen differential absorption lidar (DIAL). A detailed analysis of this measurement technique is provided which includes corrections for imprecise knowledge of the detector background level, the oxygen absorption fine parameters, and variations in the laser output energy. In addition, we analyze other possible sources of systematic errors including spectral effects related to aerosol and molecular scattering interference by rotational Raman scattering and interference by isotopic oxygen fines.

  13. NASA three-laser airborne differential absorption lidar system electronics

    NASA Technical Reports Server (NTRS)

    Allen, R. J.; Copeland, G. D.

    1984-01-01

    The system control and signal conditioning electronics of the NASA three laser airborne differential absorption lidar (DIAL) system are described. The multipurpose DIAL system was developed for the remote measurement of gas and aerosol profiles in the troposphere and lower stratosphere. A brief description and photographs of the majority of electronics units developed under this contract are presented. The precision control system; which includes a master control unit, three combined NASA laser control interface/quantel control units, and three noise pulse discriminator/pockels cell pulser units; is described in detail. The need and design considerations for precision timing and control are discussed. Calibration procedures are included.

  14. New Differential Absorption Lidar for Stratospheric Ozone Monitoring in Argentina

    NASA Astrophysics Data System (ADS)

    Wolfram, Elian A.; Salvador, Jacobo; D'Elia, Raul; Pazmiño, Andrea; Godin-Beeckmann, Sophie; Nakane, Hideki; Quel, Eduardo

    2008-04-01

    As part of environmental studies concerning with measurements of the stratospheric ozone layer, the CEILAP developed a new Differential Absorption Lidar (DIAL) instrument. Since the early construction of the first DIAL instrument, Lidar Division has been made important financial and scientific investments to improve this initial prototype. The new version has a bigger reception system formed by 4 newtonian telescopes of 50 cm diameter each one and a higher number of detection channels: four different wavelengths are detected simultaneously and six digital channels record the Rayleigh and Raman backscattered photons emitted by an ClXe Excimer laser at 308 nm and third harmonic of Nd-YAG laser at 355 nm. A number of different changes have been made to increase the dynamical range of this lidar: a mechanical chopper was installed together with gated photomultiplier in the high energy detection channels to avoid strong signals from lower atmospheric layers. This new version was installed inside a shelter given the possibility to make field campaigns outside CEILAP laboratories as SOLAR Campaign made in Argentine Patagonian region during 2005-2006 springs. In this paper a full description of instrument update is given. Intercomparisons with ozonesonde and satellite platform instrument are presented. The results show agreement better than 10% in 16-38 km range when same airmasses are sampled.

  15. Recent Pulsed Airborne Lidar measurements of Atmospheric CO2 Column Absorption to 13 km altitudes

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Riris, H.; Allan, G. R.; Weaver, C. J.; Mao, J.; Hasselbrack, W.; Sun, X.; Rodriguez, M. R.

    2010-12-01

    We have developed a lidar technique for measuring atmospheric CO2 concentrations as a candidate for NASA’s ASCENDS mission. It uses pulsed laser transmitters to simultaneously measure a CO2 absorption line in the 1570 nm band, O2 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers step in wavelength across the CO2 line and an O2 line pair during the measurement. The receiver uses a telescope and photon counting detectors, and measures the time resolved backscatter of the laser echoes. Signal processing is used to isolate the laser echo signals from the surface, estimate their range, and reject laser photons scattered in the atmosphere. The gas extinction and column densities for the CO2 and O2 gases are estimated via the IPDA technique. We developed a lidar to demonstrate the CO2 measurement from aricraft. The lidar steps the pulsed laser’s wavelength across a selected CO2 line with 20 or 30 steps per scan. The line scan rate is 450 Hz and laser pulse widths are 1 usec. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. During July and August 2009 we made 5 two hour long flights while installed on the NASA Glenn Lear-25 aircraft. We measured the atmospheric CO2 absorption and line shapes using the 1572.33 nm CO2 line. Measurements were made at stepped altitudes from 3-13 km over a variety of surfaces in Nebraska, Illinois, the SGP ARM site, and near and over the Chesapeake Bay. Strong laser signals and clear line shapes were observed at all altitudes, and some measurements were made through thin clouds. The Oklahoma and east coast flights were coordinated with the NASA LaRC/ITT CO2 lidar on their UC-12 aircraft, a LaRC in-situ CO2 sensor, and the Oklahoma flights also included a JPL CO2 lidar on a Twin Otter aircraft. Ed Browell

  16. Differential absorption lidar system for routine monitoring of tropospheric ozone.

    PubMed

    Sunesson, J A; Apituley, A; Swart, D P

    1994-10-20

    A differential absorption lidar system for routine profiling of tropospheric ozone for daytime and nighttime operation is described. The system uses stimulated Raman scattering in hydrogen and deuterium of 266-nm radiation from a quadrupled Nd:YAG laser. Ozone profiles from altitudes of 600 m to approximately 5 km have been obtained with analog detection. Implementing corrections for differential Rayleigh scattering, differential absorption from oxygen, sulphur dioxide, and nitrogen dioxide, and differential aerosol extinction and backscatter can reduce the total system inaccuracy to 5-15% for a clear day and 20-30% for a hazy day, except at the top of the mixed layer. Photon counting must be installed to increase the measurement range from 5 to 15 km. An example of an application of routine measurements of tropospheric ozone profiles is given.

  17. Water vapor differential absorption lidar development and evaluation

    NASA Technical Reports Server (NTRS)

    Browell, E. V.; Wilkerson, T. D.; Mcllrath, T. J.

    1979-01-01

    A ground-based differential absorption lidar (DIAL) system is described which has been developed for vertical range-resolved measurements of water vapor. The laser transmitter consists of a ruby-pumped dye laser, which is operated on a water vapor absorption line at 724.372 nm. Part of the ruby laser output is transmitted simultaneously with the dye laser output to determine atmospheric scattering and attenuation characteristics. The dye and ruby laser backscattered light is collected by a 0.5-m diam telescope, optically separated in the receiver package, and independently detected using photomultiplier tubes. Measurements of vertical water vapor concentration profiles using the DIAL system at night are discussed, and comparisons are made between the water vapor DIAL measurements and data obtained from locally launched rawinsondes. Agreement between these measurements was found to be within the uncertainty of the rawinsonde data to an altitude of 3 km. Theoretical simulations of this measurement were found to give reasonably accurate predictions of the random error of the DIAL measurements. Confidence in these calculations will permit the design of aircraft and Shuttle DIAL systems and experiments using simulation results as the basis for defining lidar system performance requirements

  18. Spaceborne profiling of atmospheric temperature and particle extinction with pure rotational Raman lidar and of relative humidity in combination with differential absorption lidar: performance simulations

    SciTech Connect

    Di Girolamo, Paolo; Behrendt, Andreas; Wulfmeyer, Volker

    2006-04-10

    The performance of a spaceborne temperature lidar based on the pure rotational Raman (RR) technique in the UV has been simulated. Results show that such a system deployed onboard a low-Earth-orbit satellite would provide global-scale clear-sky temperature measurements in the troposphere and lower stratosphere with precisions that satisfy World Meteorological Organization (WMO) threshold observational requirements for numerical weather prediction and climate research applications. Furthermore, nighttime temperature measurements would still be within the WMO threshold observational requirements in the presence of several cloud structures. The performance of aerosol extinction measurements from space, which can be carried out simultaneously with temperature measurements by RR lidar, is also assessed. Furthermore, we discuss simulations of relative humidity measurements from space obtained from RR temperature measurements and water-vapor data measured with the differential absorption lidar (DIAL) technique.

  19. Spaceborne profiling of atmospheric temperature and particle extinction with pure rotational Raman lidar and of relative humidity in combination with differential absorption lidar: performance simulations.

    PubMed

    Di Girolamo, Paolo; Behrendt, Andreas; Wulfmeyer, Volker

    2006-04-10

    The performance of a spaceborne temperature lidar based on the pure rotational Raman (RR) technique in the UV has been simulated. Results show that such a system deployed onboard a low-Earth-orbit satellite would provide global-scale clear-sky temperature measurements in the troposphere and lower stratosphere with precisions that satisfy World Meteorological Organization (WMO) threshold observational requirements for numerical weather prediction and climate research applications. Furthermore, nighttime temperature measurements would still be within the WMO threshold observational requirements in the presence of several cloud structures. The performance of aerosol extinction measurements from space, which can be carried out simultaneously with temperature measurements by RR lidar, is also assessed. Furthermore, we discuss simulations of relative humidity measurements from space obtained from RR temperature measurements and water-vapor data measured with the differential absorption lidar (DIAL) technique.

  20. Scalable lidar technique for fire detection

    NASA Astrophysics Data System (ADS)

    Utkin, Andrei B.; Piedade, Fernando; Beixiga, Vasco; Mota, Pedro; Lousã, Pedro

    2014-08-01

    Lidar (light detection and ranging) presents better sensitivity than fire surveillance based on imaging. However, the price of conventional lidar equipment is often too high as compared to passive fire detection instruments. We describe possibilities to downscale the technology. First, a conventional lidar, capable of smoke-plume detection up to ~10 km, may be replaced by an industrially manufactured solid-state laser rangefinder. This reduces the detection range to about 5 km, but decreases the purchase price by one order of magnitude. Further downscaling is possible by constructing the lidar smoke sensor on the basis of a low-cost laser diode.

  1. Gluing for Raman lidar systems using the lamp mapping technique.

    PubMed

    Walker, Monique; Venable, Demetrius; Whiteman, David N

    2014-12-20

    In the context of combined analog and photon counting (PC) data acquisition in a Lidar system, glue coefficients are defined as constants used for converting an analog signal into a virtual PC signal. The coefficients are typically calculated using Lidar profile data taken under clear, nighttime conditions since, in the presence of clouds or high solar background, it is difficult to obtain accurate glue coefficients from Lidar backscattered data. Here we introduce a new method in which we use the lamp mapping technique (LMT) to determine glue coefficients in a manner that does not require atmospheric profiles to be acquired and permits accurate glue coefficients to be calculated when adequate Lidar profile data are not available. The LMT involves scanning a halogen lamp over the aperture of a Lidar receiver telescope such that the optical efficiency of the entire detection system is characterized. The studies shown here involve two Raman lidar systems; the first from Howard University and the second from NASA/Goddard Space Flight Center. The glue coefficients determined using the LMT and the Lidar backscattered method agreed within 1.2% for the water vapor channel and within 2.5% for the nitrogen channel for both Lidar systems. We believe this to be the first instance of the use of laboratory techniques for determining the glue coefficients for Lidar data analysis. PMID:25608203

  2. Gluing for Raman lidar systems using the lamp mapping technique.

    PubMed

    Walker, Monique; Venable, Demetrius; Whiteman, David N

    2014-12-20

    In the context of combined analog and photon counting (PC) data acquisition in a Lidar system, glue coefficients are defined as constants used for converting an analog signal into a virtual PC signal. The coefficients are typically calculated using Lidar profile data taken under clear, nighttime conditions since, in the presence of clouds or high solar background, it is difficult to obtain accurate glue coefficients from Lidar backscattered data. Here we introduce a new method in which we use the lamp mapping technique (LMT) to determine glue coefficients in a manner that does not require atmospheric profiles to be acquired and permits accurate glue coefficients to be calculated when adequate Lidar profile data are not available. The LMT involves scanning a halogen lamp over the aperture of a Lidar receiver telescope such that the optical efficiency of the entire detection system is characterized. The studies shown here involve two Raman lidar systems; the first from Howard University and the second from NASA/Goddard Space Flight Center. The glue coefficients determined using the LMT and the Lidar backscattered method agreed within 1.2% for the water vapor channel and within 2.5% for the nitrogen channel for both Lidar systems. We believe this to be the first instance of the use of laboratory techniques for determining the glue coefficients for Lidar data analysis.

  3. Lidar: A laser technique for remote sensing

    NASA Technical Reports Server (NTRS)

    Wilkerson, T. D.; Hickman, G. D.

    1978-01-01

    Experimental airborne lidar systems proved to be useful for shallow water bathymetric measurements, and detection and identification of oil slicks and algae. Dye fluorescence applications using organic dyes was studied. The possibility of remotely inducing dye flourescence by means of pulsed lasers opens up several hydrospheric applications for measuring water currents, water temperature, and salinity. Aerosol measurements by lidar are also discussed.

  4. Spatial and temporal filtering technique for processing lidar photocount data.

    PubMed

    Gardner, C S; Shelton, J D

    1981-04-01

    Shot noise places a practical limit on the spatial and temporal resolution of lidar photocount data. A 2-D signal-processing technique that utilizes spatial and temporal filtering to reduce shot noise and increase resolution is described. The technique is applied to sodium lidar data collected during the fall of 1979 over Urbana, Illinois. Temporal filtering is shown to enhance the spatial resolution of the sodium profiles significantly by reducing shot noise by more than 10 dB. The signal-processing technique is applicable to a wide variety of lidar data.

  5. Airborne Measurements of CO2 Column Absorption and Range Using a Pulsed Direct-Detection Integrated Path Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Weaver, Clark J.; Mao, Jianping; Allan, Graham R.; Hasselbrack, William E.; Browell, Edward V.

    2013-01-01

    We report on airborne CO2 column absorption measurements made in 2009 with a pulsed direct-detection lidar operating at 1572.33 nm and utilizing the integrated path differential absorption technique. We demonstrated these at different altitudes from an aircraft in July and August in flights over four locations in the central and eastern United States. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. The lidar measurement statistics were also calculated for each flight as a function of altitude. The optical depth varied nearly linearly with altitude, consistent with calculations based on atmospheric models. The scatter in the optical depth measurements varied with aircraft altitude as expected, and the median measurement precisions for the column varied from 0.9 to 1.2 ppm. The altitude range with the lowest scatter was 810 km, and the majority of measurements for the column within it had precisions between 0.2 and 0.9 ppm.

  6. Lidar signal-to-noise ratio improvements: Considerations and techniques

    NASA Astrophysics Data System (ADS)

    Hassebo, Yasser Y.

    The primary objective of this study is to improve lidar signal-to-noise ratio (SNR) and hence extend attainable lidar ranges through reduction of the sky background noise (BGP), which dominates other sources of noise in daytime operations. This is particularly important for Raman lidar techniques where the Raman backscattered signal of interest is relatively weak compared with the elastic backscatter lidars. Two approaches for reduction of sky background noise are considered: (1) Improvements in lidar SNR by optimization of the design of the lidar receiver were examined by a series of simulations. This part of the research concentrated on biaxial lidar systems, where overlap between laser beam and receiver field of view (FOV) is an important aspect of noise considerations. The first optimized design evolved is a wedge shaped aperture. While this design has the virtue of greatly reducing background light, it is difficult to implement practically, requiring both changes in area and position with lidar range. A second more practical approach, which preserves some of the advantages of the wedge design, was also evolved. This uses a smaller area circular aperture optimally located in the image plane for desired ranges. Simulated numerical results for a biaxial lidar have shown that the best receiver parameters selection is one using a small circular aperture (field stop) with a small telescope focal length f, to ensure the minimum FOV that accepts all return signals over the entire lidar range while at the same time minimizing detected BGP and hence maximizing lidar SNR and attainable lidar ranges. The improvement in lidar SNR was up to 18%. (2) A polarization selection technique was implemented to reduce sky background signal for linearly polarized monostatic elastic backscatter lidar measurements. The technique takes advantage of naturally occurring polarization properties in scattered sky light, and then ensures that both the lidar transmitter and receiver track and

  7. Estimation of background gas concentration from differential absorption lidar measurements

    NASA Astrophysics Data System (ADS)

    Harris, Peter; Smith, Nadia; Livina, Valerie; Gardiner, Tom; Robinson, Rod; Innocenti, Fabrizio

    2016-10-01

    Approaches are considered to estimate the background concentration level of a target species in the atmosphere from an analysis of the measured data provided by the National Physical Laboratory's differential absorption lidar (DIAL) system. The estimation of the background concentration level is necessary for an accurate quantification of the concentration level of the target species within a plume, which is the quantity of interest. The focus of the paper is on methodologies for estimating the background concentration level and, in particular, contrasting the assumptions about the functional and statistical models that underpin those methodologies. An approach is described to characterise the noise in the recorded signals, which is necessary for a reliable estimate of the background concentration level. Results for measured data provided by a field measurement are presented, and ideas for future work are discussed.

  8. Differential Absorption Measurements of Atmospheric Water Vapor with a Coherent Lidar at 2050.532 nm

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Dharamsi, Amin; Davis, Richard E.; Petros, Mulugeta; McCarthy, John C.

    1999-01-01

    Wind and water vapor are two major factors driving the Earth's atmospheric circulation, and direct measurement of these factors is needed for better understanding of basic atmospheric science, weather forecasting, and climate studies. Coherent lidar has proved to be a valuable tool for Doppler profiling of wind fields, and differential absorption lidar (DIAL) has shown its effectiveness in profiling water vapor. These two lidar techniques are generally considered distinctly different, but this paper explores an experimental combination of the Doppler and DIAL techniques for measuring both wind and water vapor with an eye-safe wavelength based on a solid-state laser material. Researchers have analyzed and demonstrated coherent DIAL water vapor measurements at 10 micrometers wavelength based on CO2 lasers. The hope of the research presented here is that the 2 gm wavelength in a holmium or thulium-based laser may offer smaller packaging and more rugged operation that the CO2-based approach. Researchers have extensively modeled 2 um coherent lasers for water vapor profiling, but no published demonstration is known. Studies have also been made, and results published on the Doppler portion, of a Nd:YAG-based coherent DIAL operating at 1.12 micrometers. Eye-safety of the 1.12 micrometer wavelength may be a concern, whereas the longer 2 micrometer and 10 micrometer systems allow a high level of eyesafety.

  9. Preliminary measurements with an automated compact differential absorption lidar for the profiling of water vapor.

    PubMed

    Machol, Janet L; Ayers, Tom; Schwenz, Karl T; Koenig, Keith W; Hardesty, R Michael; Senff, Christoph J; Krainak, Michael A; Abshire, James B; Bravo, Hector E; Sandberg, Scott P

    2004-05-20

    The design and preliminary tests of an automated differential absorption lidar (DIAL) that profiles water vapor in the lower troposphere are presented. The instrument, named CODI (for compact DIAL), has been developed to be eye safe, low cost, weatherproof, and portable. The lidar design and its unattended operation are described. Nighttime intercomparisons with in situ sensors and a radiosonde are shown. Desired improvements to the lidar, including a more powerful laser, are also discussed.

  10. Total fluxes of sulfur dioxide from the Italian volcanoes Etna, Stromboli, and Vulcano measured by differential absorption lidar and passive differential optical absorption spectroscopy

    SciTech Connect

    Edner, H.; Ragnarson, P.; Svanberg, S.; Wallinder, E.; Ferrara, R.; Cioni, R.; Raco, B.; Taddeucci, G.

    1994-09-20

    The authors present measurements of the total flux of sulfur dioxide from three Italian volcanoes Etna, Stromboli, and Vulcano, measured in a three day period in Sept, 1992. The fluxes were measured from shipboard by means of an active differential absorption lidar technique, and a passive differential optical absorption spectroscopy technique. Corrections had to be applied to the passive optical technique because the light source paths were not well defined. The total fluxes were found to be roughly 25, 180, and 1300 tons/day for Vulcano, Stromboli, and Etna, respectively. 43 refs., 10 figs., 6 tabs.

  11. Adaptive Kalman-Bucy filter for differential absorption lidar time series data.

    PubMed

    Warren, R E

    1987-11-15

    An extension of the Kalman-Bucy algorithm for on-line estimation of multimaterial path-integrated concentration from multiwavelength differential absorption lidar time series data is presented in which the system model covariance is adaptively estimated from the input data. Performance of the filter is compared with that of a nonadaptive Kalman-Bucy filter using synthetic and actual lidar data.

  12. Differential absorption lidar measurements of atmospheric water vapor using a pseudonoise code modulated AlGaAs laser. Thesis

    NASA Technical Reports Server (NTRS)

    Rall, Jonathan A. R.

    1994-01-01

    Lidar measurements using pseudonoise code modulated AlGaAs lasers are reported. Horizontal path lidar measurements were made at night to terrestrial targets at ranges of 5 and 13 km with 35 mW of average power and integration times of one second. Cloud and aerosol lidar measurements were made to thin cirrus clouds at 13 km altitude with Rayleigh (molecular) backscatter evident up to 9 km. Average transmitter power was 35 mW and measurement integration time was 20 minutes. An AlGaAs laser was used to characterize spectral properties of water vapor absorption lines at 811.617, 816.024, and 815.769 nm in a multipass absorption cell using derivative spectroscopy techniques. Frequency locking of an AlGaAs laser to a water vapor absorption line was achieved with a laser center frequency stability measured to better than one-fifth of the water vapor Doppler linewidth over several minutes. Differential absorption lidar measurements of atmospheric water vapor were made in both integrated path and range-resolved modes using an externally modulated AlGaAs laser. Mean water vapor number density was estimated from both integrated path and range-resolved DIAL measurements and agreed with measured humidity values to within 6.5 percent and 20 percent, respectively. Error sources were identified and their effects on estimates of water vapor number density calculated.

  13. Technique to separate lidar signal and sunlight.

    PubMed

    Sun, Wenbo; Hu, Yongxiang; MacDonnell, David G; Weimer, Carl; Baize, Rosemary R

    2016-06-13

    Sunlight contamination dominates the backscatter noise in space-based lidar measurements during daytime. The background scattered sunlight is highly variable and dependent upon the surface and atmospheric albedo. The scattered sunlight contribution to noise increases over land and snow surfaces where surface albedos are high and thus overwhelm lidar backscatter from optically thin atmospheric constituents like aerosols and thin clouds. In this work, we developed a novel lidar remote sensing concept that potentially can eliminate sunlight induced noise. The new lidar concept requires: (1) a transmitted laser light that carries orbital angular momentum (OAM); and (2) a photon sieve (PS) diffractive filter that separates scattered sunlight from laser light backscattered from the atmosphere, ocean and solid surfaces. The method is based on numerical modeling of the focusing of Laguerre-Gaussian (LG) laser beam and plane-wave light by a PS. The model results show that after passing through a PS, laser light that carries the OAM is focused on a ring (called "focal ring" here) on the focal plane of the PS filter, very little energy arrives at the center of the focal plane. However, scattered sunlight, as a plane wave without the OAM, focuses at the center of the focal plane and thus can be effectively blocked or ducted out. We also find that the radius of the "focal ring" increases with the increase of azimuthal mode (L) of LG laser light, thus increasing L can more effectively separate the lidar signal away from the sunlight noise.

  14. Technique to separate lidar signal and sunlight.

    PubMed

    Sun, Wenbo; Hu, Yongxiang; MacDonnell, David G; Weimer, Carl; Baize, Rosemary R

    2016-06-13

    Sunlight contamination dominates the backscatter noise in space-based lidar measurements during daytime. The background scattered sunlight is highly variable and dependent upon the surface and atmospheric albedo. The scattered sunlight contribution to noise increases over land and snow surfaces where surface albedos are high and thus overwhelm lidar backscatter from optically thin atmospheric constituents like aerosols and thin clouds. In this work, we developed a novel lidar remote sensing concept that potentially can eliminate sunlight induced noise. The new lidar concept requires: (1) a transmitted laser light that carries orbital angular momentum (OAM); and (2) a photon sieve (PS) diffractive filter that separates scattered sunlight from laser light backscattered from the atmosphere, ocean and solid surfaces. The method is based on numerical modeling of the focusing of Laguerre-Gaussian (LG) laser beam and plane-wave light by a PS. The model results show that after passing through a PS, laser light that carries the OAM is focused on a ring (called "focal ring" here) on the focal plane of the PS filter, very little energy arrives at the center of the focal plane. However, scattered sunlight, as a plane wave without the OAM, focuses at the center of the focal plane and thus can be effectively blocked or ducted out. We also find that the radius of the "focal ring" increases with the increase of azimuthal mode (L) of LG laser light, thus increasing L can more effectively separate the lidar signal away from the sunlight noise. PMID:27410314

  15. High-speed signal sampling technique in lidar application

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Zhao, Yuan; Liu, Feng; Su, Jian-zhong

    2013-09-01

    Common lidar systems sets the standard using only one sample data from the laser echo signal, while information from signal waveform is ignored, constraining further enhancement of range resolution and accuracy. By employing high-speed signal sampling technique, we make full use of the echo signal, and achieved large improvement on range resolution and accuracy. Moreover, the digital signal processing algorithm can be adopted for different targets, which provides better versatility of the lidar system. This paper reviewed high speed signal sampling technique and its application in lidar system. The HT high-speed DAQ developed in our group was used in both FMCW lidar and pulse laser radar. Over fourfold increase in range accuracy, comparing to that of traditional method, is demonstrated.

  16. Error analysis of Raman differential absorption lidar ozone measurements in ice clouds.

    PubMed

    Reichardt, J

    2000-11-20

    A formalism for the error treatment of lidar ozone measurements with the Raman differential absorption lidar technique is presented. In the presence of clouds wavelength-dependent multiple scattering and cloud-particle extinction are the main sources of systematic errors in ozone measurements and necessitate a correction of the measured ozone profiles. Model calculations are performed to describe the influence of cirrus and polar stratospheric clouds on the ozone. It is found that it is sufficient to account for cloud-particle scattering and Rayleigh scattering in and above the cloud; boundary-layer aerosols and the atmospheric column below the cloud can be neglected for the ozone correction. Furthermore, if the extinction coefficient of the cloud is ?0.1 km(-1), the effect in the cloud is proportional to the effective particle extinction and to a particle correction function determined in the limit of negligible molecular scattering. The particle correction function depends on the scattering behavior of the cloud particles, the cloud geometric structure, and the lidar system parameters. Because of the differential extinction of light that has undergone one or more small-angle scattering processes within the cloud, the cloud effect on ozone extends to altitudes above the cloud. The various influencing parameters imply that the particle-related ozone correction has to be calculated for each individual measurement. Examples of ozone measurements in cirrus clouds are discussed.

  17. Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Remus, Ruben G.; Fay, James J.; Reithmaier, Karl

    2014-01-01

    Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  18. An Assessment of a Technique for Modeling Lidar Background Measurements

    NASA Astrophysics Data System (ADS)

    Powell, K. A.; Hunt, W. H.; Vaughan, M. A.; Hair, J. W.; Butler, C. F.; Hostetler, C. A.

    2015-12-01

    A high-fidelity lidar simulation tool has been developed to generate synthetic lidar backscatter data that closely matches the expected performance of various lidars, including the noise characteristics inherent to analog detection and uncertainties related to the measurement environment. This tool supports performance trade studies and scientific investigations for both the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), which flies aboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and the NASA Langley Research Center airborne High Spectral Resolution Lidar (HSRL). The simulation tool models the lidar instrument characteristics, the backscatter signals generated from aerosols, clouds, ocean surface and subsurface, and the solar background signals. The background signals are derived from the simulated aerosol and cloud characteristics, the surface type, and solar zenith angle, using a look-up table of upwelling radiance vs scene type. The upwelling radiances were derived from the CALIOP RMS background noise and were correlated with measurements of the particulate intensive and extensive optical properties, including surface scattering for transparent layers. Tests were conducted by tuning the tool for both HSRL and CALIOP instrument settings and the atmospheres were defined using HSRL measurements from underflights of CALIPSO. For similar scenes, the simulated and measured backgrounds were compared. Overall, comparisons showed good agreement, verifying the accuracy of the tool to support studies involving instrument characterization and advanced data analysis techniques.

  19. Edge technique Doppler lidar wind measurements with high vertical resolution.

    PubMed

    Korb, C L; Gentry, B M; Li, S X

    1997-08-20

    We have developed a Doppler lidar system using the edge technique and have made atmospheric lidar wind measurements. Line-of-sight wind profiles with a vertical resolution of 22 m have a standard deviation of 0.40 m /s for a ten-shot average. Day and night lidar measurements of the vector wind have been made for altitudes from 200 to 2000 m. We validated the lidar measurements by comparing them with independent rawinsonde and pilot balloon measurements of wind speed and direction. Good agreement was obtained. The instrumental noise for these data is 0.11 m /s for a 500-shot average, which is in good agreement with the observed minimum value of the standard deviation for the atmospheric measurements. The average standard deviation over 30 mins varied from 1.16 to 0.25 m /s for day and night, respectively. High spatial and temporal resolution lidar profiles of line-of-sight winds clearly show wind shear and turbulent features at the 1 -2-m /s level with a high signal-to-noise ratio and demonstrate the potential of the edge-technique lidar for studying turbulent processes and atmospheric dynamics.

  20. Micropulse water vapor differential absorption lidar: transmitter design and performance.

    PubMed

    Nehrir, Amin R; Repasky, Kevin S; Carlsten, John L

    2012-10-22

    An all diode-laser-based micropulse differential absorption lidar (DIAL) laser transmitter for tropospheric water vapor and aerosol profiling is presented. The micropulse DIAL (MPD) transmitter utilizes two continuous wave (cw) external cavity diode lasers (ECDL) to seed an actively pulsed, overdriven tapered semiconductor optical amplifier (TSOA). The MPD laser produces up to 7 watts of peak power over a 1 µs pulse duration (7 µJ) and a 10 kHz pulse repetition frequency. Spectral switching between the online and offline seed lasers is achieved on a 1Hz basis using a fiber optic switch to allow for more accurate sampling of the atmospheric volume between the online and offline laser shots. The high laser spectral purity of greater than 0.9996 coupled with the broad tunability of the laser transmitter will allow for accurate measurements of tropospheric water vapor in a wide range of geographic locations under varying atmospheric conditions. This paper describes the design and performance characteristics of a third generation MPD laser transmitter with enhanced laser performance over the previous generation DIAL system.

  1. Micropulse water vapor differential absorption lidar: transmitter design and performance.

    PubMed

    Nehrir, Amin R; Repasky, Kevin S; Carlsten, John L

    2012-10-22

    An all diode-laser-based micropulse differential absorption lidar (DIAL) laser transmitter for tropospheric water vapor and aerosol profiling is presented. The micropulse DIAL (MPD) transmitter utilizes two continuous wave (cw) external cavity diode lasers (ECDL) to seed an actively pulsed, overdriven tapered semiconductor optical amplifier (TSOA). The MPD laser produces up to 7 watts of peak power over a 1 µs pulse duration (7 µJ) and a 10 kHz pulse repetition frequency. Spectral switching between the online and offline seed lasers is achieved on a 1Hz basis using a fiber optic switch to allow for more accurate sampling of the atmospheric volume between the online and offline laser shots. The high laser spectral purity of greater than 0.9996 coupled with the broad tunability of the laser transmitter will allow for accurate measurements of tropospheric water vapor in a wide range of geographic locations under varying atmospheric conditions. This paper describes the design and performance characteristics of a third generation MPD laser transmitter with enhanced laser performance over the previous generation DIAL system. PMID:23187280

  2. Rayleigh-backscattering doppler broadening correction for differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Fan, Lanlan; Zhang, Yinchao; Chen, Siying; Guo, Pan; Chen, He

    2015-11-01

    The spectral broadening by Rayleigh backscattering can cause large changes in water vapor echo signals, causing errors when the water vapor concentration is inversed by differential absorption lidar (DIAL). A correction algorithm is proposed to revise the errors due to the effect of laser spectral broadening. The relative errors of water vapor are calculated in cases of different aerosol distribution and temperature changes before and after correction. The results show that measurement errors due to the Doppler broadening are more than 5% before correction and a 2% measurement error after corrected for the case of a smooth, background aerosol distribution. However, due to the high aerosol gradients and strong temperature inversion, errors can be up to 40% and 10% with no corrections for this effect, respectively. The relative errors can reduce to less than 2% after correction. Hence, the correction algorithm for Rayleigh Doppler broadening can improve detection accuracy in H2O DIAL measurements especially when it is applied to high aerosol concentration or strong temperature inversion.

  3. Progress Report on Frequency - Modulated Differential Absorption Lidar

    SciTech Connect

    Cannon, Bret D.; Harper, Warren W.; Myers, Tanya L.; Taubman, Matthew S.; Williams, Richard M.; Schultz, John F.

    2001-12-15

    Modeling done at Pacific Northwest National Laboratory (PNNL) in FY2000 predicted improved sensitivity for remote chemical detection by differential absorption lidar (DIAL) if frequency-modulated (FM) lasers were used. This improved sensitivity results from faster averaging away of speckle noise and the recently developed quantum cascade (QC) lasers offer the first practical method for implementing this approach in the molecular fingerprint region of the infrared. To validate this model prediction, a simple laboratory bench FM-DIAL system was designed, assembled, tested, and laboratory-scale experiments were carried out during FY2001. Preliminary results of the FM DIAL experiments confirm the speckle averaging advantages predicted by the models. In addition, experiments were performed to explore the use of hybrid QC - CO2 lasers for achieving sufficient frequency-modulated laser power to enable field experiments at longer ranges (up to one kilometer or so). This approach will allow model validation at realistic ranges much sooner than would be possible if one had to first develop master oscillator - power amplifier systems utilizing only QC devices. Amplification of a QC laser with a CO2 laser was observed in the first hybrid laser experiments, but the low gain and narrow linewidth of the CO2 laser available for these experiments prevented production of a high-power FM laser beam.

  4. Orthogonal spectra and cross sections: Application to optimization of multi-spectral absorption and fluorescence lidar

    SciTech Connect

    Shokair, I.R.

    1997-09-01

    This report addresses the problem of selection of lidar parameters, namely wavelengths for absorption lidar and excitation fluorescence pairs for fluorescence lidar, for optimal detection of species. Orthogonal spectra and cross sections are used as mathematical representations which provide a quantitative measure of species distinguishability in mixtures. Using these quantities, a simple expression for the absolute error in calculated species concentration is derived and optimization is accomplished by variation of lidar parameters to minimize this error. It is shown that the optimum number of wavelengths for detection of a species using absorption lidar (excitation fluorescence pairs for fluorescence lidar) is the same as the number of species in the mixture. Each species present in the mixture has its own set of optimum wavelengths. There is usually some overlap in these sets. The optimization method is applied to two examples, one using absorption and the other using fluorescence lidar, for analyzing mixtures of four organic compounds. The effect of atmospheric attenuation is included in the optimization process. Although the number of optimum wavelengths might be small, it is essential to do large numbers of measurements at these wavelengths in order to maximize canceling of statistical errors.

  5. Software system for numerical simulation of minor gas constituents lidar sensing by the differential absorption method

    NASA Astrophysics Data System (ADS)

    Bochkovskii, D. A.; Matvienko, G. G.; Romanovskii, O. A.; Kharchenko, O. V.; Yakovlev, S. V.

    2014-11-01

    This paper reports the development of LIDAS (LIdar Differential Absorption Sensing) program-algorithmic system for laser remote sensing of minor gas constituents (MGCs) of the atmosphere by the differential absorption method (DIAL). The system includes modules for the search of wavelengths informative for laser gas analysis by the differential absorption method, for numerical simulation of lidar sensing of atmospheric MGCs, and for calculation of errors of methodical, atmospheric, spectral, and instrumental origin. Lidar sensing of gas constituents by the differential absorption method as applied to problems of sensing of atmospheric MGCs is simulated numerically. Results of experiments on remote sensing of gas constituents of the atmosphere with the use of RO laser are presented.

  6. Spectral control of an alexandrite laser for an airborne water-vapor differential absorption lidar system

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Grossmann, Benoist E.; Browell, Edward V.

    1994-01-01

    A narrow-linewidth pulsed alexandrite laser has been greatly modified for improved spectral stability in an aircraft environment, and its operation has been evaluated in the laboratory for making water-vapor differential absorption lidar measurements. An alignment technique is described to achieve the optimum free spectral range ratio for the two etalons inserted in the alexandrite laser cavity, and the sensitivity of this ratio is analyzed. This technique drastically decreases the occurrence of mode hopping, which is commonly observed in a tunable, two-intracavity-etalon laser system. High spectral purity (greater than 99.85%) at 730 nm is demonstrated by the use of a water-vapor absorption line as a notch filter. The effective cross sections of 760-nm oxygen and 730-nm water-vapor absorption lines are measured at different pressures by using this laser, which has a finite linewidth of 0.02 cm(exp -1) (FWHM). It is found that for water-vapor absorption linewidths greater than 0.04 cm(exp -1) (HWHM), or for altitudes below 10 km, the laser line can be considered monochromatic because the measured effective absorption cross section is within 1% of the calculated monochromatic cross section. An analysis of the environmental sensitivity of the two intracavity etalons is presented, and a closed-loop computer control for active stabilization of the two intracavity etalons in the alexandrite laser is described. Using a water-vapor absorption line as a wavelength reference, we measure a long-term frequency drift (approximately 1.5 h) of less than 0.7 pm in the laboratory.

  7. Comparative Analysis of Different LIDAR System Calibration Techniques

    NASA Astrophysics Data System (ADS)

    Miller, M.; Habib, A.

    2016-06-01

    With light detection and ranging (LiDAR) now being a crucial tool for engineering products and on the fly spatial analysis, it is necessary for the user community to have standardized calibration methods. The three methods in this study were developed and proven by the Digital Photogrammetry Research Group (DPRG) for airborne LiDAR systems and are as follows; Simplified, Quasi-Rigorous, and Rigorous. In lieu of using expensive control surfaces for calibration, these methods compare overlapping LiDAR strips to estimate the systematic errors. These systematic errors are quantified by these methods and include the lever arm biases, boresight biases, range bias and scan angle scale bias. These three methods comprehensively represent all of the possible flight configurations and data availability and this paper will test the limits of the method with the most assumptions, the simplified calibration, by using data that violates the assumptions it's math model is based on and compares the results to the quasi-rigorous and rigorous techniques. The overarching goal is to provide a LiDAR system calibration that does not require raw measurements which can be carried out with minimal control and flight lines to reduce costs. This testing is unique because the terrain used for calibration does not contain gable roofs, all other LiDAR system calibration testing and development has been done with terrain containing features with high geometric integrity such as gable roofs.

  8. Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption in the ASCENDS 2011 Airborne Campaign

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Riris, Haris; Allan, Graham R.; Ramanathan, Anand; Hasselbrack, William E.; Mao, Jianping; Weaver, Clark; Browell, Edward V.

    2012-01-01

    We have previously demonstrated an efficient pulsed, wavelength-resolved IPDA lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission. Our team participated in the 2010 ASCENDS airborne campaigns we flew airborne version of the CO2 and O2 lidar on the NASA DC-8. The CO2 lidar measures the atmospheric backscatter profiles and shape of the 1572.33 nm absorption line using 250 mW average laser power, 30 wavelength samples per scan and 300 scans per second. Most flights had 5-6 altitude steps to greater than 12 km, and clear CO2 line shapes were observed at all altitudes. Our post-flight analysis estimated the Iidar range and pulse energies at each wavelength every second. We then solved for the best-fit CO2 absorption line shape, and calculated the Differential Optical Depth (DOD) at the line peak. We compared these to CO2 DODs calculated from spectroscopy based on HITRAN 2008 and the conditions from airborne in-situ readings. Analysis of the 2010 measurements over the Pacific Ocean and Lamont OK shows the expected -linear change of the peak DOD with altitude. For measurements at altitudes greater than 6 km the random errors were approximately 0.3 ppm for 80 sec averaging times. After the 2010 flights we improved the airborne lidar's scan uniformity, calibration and receiver sensitivity. Our team participated in the seven ASCENDS science flights during late July and August 2011. These flights were made over a wide variety of surface and cloud conditions near the US, including over the central valley of California, over several mountain ranges, over both broken and solid stratus cloud deck over the Pacific Ocean, snow patches on mountain tops, over thin and broken clouds above the US Southwest and Iowa, and over forests near the WLEF tower in Wisconsin. Analyses show the retrievals of lidar range and CO2 column absorption, as wen as estimates of CO2 mixing ratio worked well when measuring over topography with rapidly

  9. Analytical differentiation of the differential-absorption-lidar data distorted by noise.

    PubMed

    Kovalev, Vladimir A

    2002-02-20

    A method of analytical differentiation is developed for processing differential absorption lidar (DIAL) data. The method is based on simple analytical transformation of the DIAL on and off signal ratio. The derivatives consequently are found for either individual data points or local zones of the measurement range. The method makes possible the separation of local zones of interest and the separate investigation of these. The smoothing level is established by the selected value of the exponent in a transformation formula rather than by the selection of the resolution range. The method does not require the calculation of local signal increments. This reduces significantly the high-frequency noise in the measured concentration. The method is general and can be used for different experimental data, including inelastic (Raman) lidar data. The processing technique is practical and does not require a determination of the solution for a large set of algebraic equations. It is based on the simple repetition of the same type of calculations with different constants. The method can easily be implemented for practical computations.

  10. Bistatic imaging lidar technique for upper atmospheric studies.

    PubMed

    Welsh, B M; Gardner, C S

    1989-01-01

    The bistatic imaging lidar technique is fundamentally different from traditional monostatic lidar techniques. The vertical density of an atmospheric layer, such as the mesospheric sodium layer, is measured by imaging an illuminated spot within the layer. The spot is illuminated with a laser and imaged with a telescope in a bistatic configuration. Profiles through the image contain information about the vertical structure of the layer as well as the laser beam cross section. These profiles can be interpreted as the output of a linear filter having the density profile of the layer as input and an impulse response which is related to the laser beam cross section and imaging geometry. The theoretical vertical resolution can be quantified in terms of laser beamwidth and separation distance between the laser and telescope. Theoretical analysis of the technique and experimental data verifying the feasibility and basic performance of the technique are presented. PMID:20548430

  11. The Novel Nonlinear Adaptive Doppler Shift Estimation Technique and the Coherent Doppler Lidar System Validation Lidar

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.

    2006-01-01

    The signal processing aspect of a 2-m wavelength coherent Doppler lidar system under development at NASA Langley Research Center in Virginia is investigated in this paper. The lidar system is named VALIDAR (validation lidar) and its signal processing program estimates and displays various wind parameters in real-time as data acquisition occurs. The goal is to improve the quality of the current estimates such as power, Doppler shift, wind speed, and wind direction, especially in low signal-to-noise-ratio (SNR) regime. A novel Nonlinear Adaptive Doppler Shift Estimation Technique (NADSET) is developed on such behalf and its performance is analyzed using the wind data acquired over a long period of time by VALIDAR. The quality of Doppler shift and power estimations by conventional Fourier-transform-based spectrum estimation methods deteriorates rapidly as SNR decreases. NADSET compensates such deterioration in the quality of wind parameter estimates by adaptively utilizing the statistics of Doppler shift estimate in a strong SNR range and identifying sporadic range bins where good Doppler shift estimates are found. The authenticity of NADSET is established by comparing the trend of wind parameters with and without NADSET applied to the long-period lidar return data.

  12. Improved speckle statistics in coherent differential absorption lidar with in-fiber wavelength multiplexing.

    PubMed

    Ridley, K D; Pearson, G N; Harris, M

    2001-04-20

    Remote detection of gaseous pollutants and other atmospheric constituents can be achieved with differential absorption lidar (DIAL) methods. The technique relies on the transmission of two or more laser wavelengths and exploits absorption features in the target gas by measuring the ratio of their detected powers to determine gas concentration. A common mode of operation is when the transmitter and receiver are collocated, and the absorption is measured over a return trip by a randomly scattering topographic target. Hence, in coherent DIAL, speckle fluctuation leads to a large uncertainty in the detected powers unless the signal is averaged over multiple correlation times, i.e., over many independent speckles. We examine a continuous-wave coherent DIAL system in which the laser wavelengths are transmitted and received by the same single-mode optical fibers. This ensures that the two wavelengths share a common spatial mode, which, for certain transmitter and target parameters, enables highly correlated speckle fluctuations to be readily achieved in practice. For a DIAL system, this gives the potential for improved accuracy in a given observation time. A theoretical analysis quantifies this benefit as a function of the degree of correlation between the two time series (which depends on wavelength separation and target depth). The results are compared with both a numerical simulation and a laboratory-based experiment.

  13. Characterization of Cavities Using the GPR, LIDAR and GNSS Techniques

    NASA Astrophysics Data System (ADS)

    Conejo-Martín, Miguel Angel; Herrero-Tejedor, Tomás Ramón; Lapazaran, Javier; Perez-Martin, Enrique; Otero, Jaime; Prieto, Juan F.; Velasco, Jesús

    2015-11-01

    The study of the many types of natural and manmade cavities in different parts of the world is important to the fields of geology, geophysics, engineering, architectures, agriculture, heritages and landscape. Ground-penetrating radar (GPR) is a noninvasive geodetection and geolocation technique suitable for accurately determining buried structures. This technique requires knowing the propagation velocity of electromagnetic waves (EM velocity) in the medium. We propose a method for calibrating the EM velocity using the integration of laser imaging detection and ranging (LIDAR) and GPR techniques using the Global Navigation Satellite System (GNSS) as support for geolocation. Once the EM velocity is known and the GPR profiles have been properly processed and migrated, they will also show the hidden cavities and the old hidden structures from the cellar. In this article, we present a complete study of the joint use of the GPR, LIDAR and GNSS techniques in the characterization of cavities. We apply this methodology to study underground cavities in a group of wine cellars located in Atauta (Soria, Spain). The results serve to identify construction elements that form the cavity and group of cavities or cellars. The described methodology could be applied to other shallow underground structures with surface connection, where LIDAR and GPR profiles could be joined, as, for example, in archaeological cavities, sewerage systems, drainpipes, etc.

  14. [A new retrieval method for ozone concentration at the troposphere based on differential absorption lidar].

    PubMed

    Fan, Guang-Qiang; Liu, Jian-Guo; Liu, Wen-Qing; Lu, Yi-Huai; Zhang, Tian-Shu; Dong, Yun-Sheng; Zhao, Xue-Song

    2012-12-01

    Aerosols interfere with differential absorption lidar ozone concentration measurement and can introduce significant errors. A new retrieval method was introduced, and ozone concentration and aerosol extinction coefficient were gained simultaneously based on the retrieval method. The variables were analyzed by experiment including aerosol lidar ratio, aerosol wavelength exponent, and aerosol-molecular ratio at the reference point. The results show that these parameters introduce error less than 8% below 1 km. The measurement error derives chiefly from signal noise and the parameters introduce error less than 3% above 1 km. Finally the vertical profile of tropospheric ozone concentration and aerosol extinction coefficient were derived by using this algorithm. The retrieval results of the algorithm and traditional dual-wavelength difference algorithm are compared and analyzed. Experimental results indicate that the algorithm is feasible, and the algorithm can reduce differential absorption lidar measurement error introduced by aerosol.

  15. 2-Micron Triple-Pulse Integrated Path Differential Absorption Lidar Development for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong

    2016-01-01

    For more than 15 years, NASA Langley Research Center (LaRC) has contributed in developing several 2-micron carbon dioxide active remote sensors using the DIAL technique. Currently, an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is under development at NASA LaRC. This paper focuses on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of wavelength control, packaging and lidar integration. In addition, receiver development updates will also be presented, including telescope integration, detection systems and data acquisition electronics. Future plan for IPDA lidar system for ground integration, testing and flight validation will be presented.

  16. Adaptive Data Processing Technique for Lidar-Assisted Control to Bridge the Gap between Lidar Systems and Wind Turbines: Preprint

    SciTech Connect

    Schlipf, David; Raach, Steffen; Haizmann, Florian; Cheng, Po Wen; Fleming, Paul; Scholbrock, Andrew, Krishnamurthy, Raghu; Boquet, Mathieu

    2015-12-14

    This paper presents first steps toward an adaptive lidar data processing technique crucial for lidar-assisted control in wind turbines. The prediction time and the quality of the wind preview from lidar measurements depend on several factors and are not constant. If the data processing is not continually adjusted, the benefit of lidar-assisted control cannot be fully exploited, or can even result in harmful control action. An online analysis of the lidar and turbine data are necessary to continually reassess the prediction time and lidar data quality. In this work, a structured process to develop an analysis tool for the prediction time and a new hardware setup for lidar-assisted control are presented. The tool consists of an online estimation of the rotor effective wind speed from lidar and turbine data and the implementation of an online cross correlation to determine the time shift between both signals. Further, initial results from an ongoing campaign in which this system was employed for providing lidar preview for feed-forward pitch control are presented.

  17. The concentration-estimation problem for multiple-wavelength differential absorption lidar

    SciTech Connect

    Payne, A.N.

    1994-07-01

    We are seeking to develop a reliable methodology for multi-chemicai detection and discrimination based upon multi-wavelength differential absorption lidar measurements. In this paper, we summarize some preliminary results of our efforts to devise suitable concentration-estimation algorithms for use in detection and discrimination schemes.

  18. Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption and Range During the ASCENDS 2009-2011 Airborne Campaigns

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.; Weaver, C. J.; Riris, H.; Mao, J.; Sun, X.; Allan, G. R.; Hasselbrack, W. E.; Browell, E. V.

    2012-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission and have demonstrated the CO2 and O2 measurements from aircraft. Our technique uses two pulsed lasers allowing simultaneous measurement of a single CO2 absorption line near 1572 nm, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are stepped in wavelength across the CO2 line and an O2 line doublet during the measurement. The column densities for the CO2 and O2 are estimated from the differential optical depths (DOD) of the scanned absorption lines via the IPDA technique. For the 2009 ASCENDS campaign we flew the CO2 lidar only on a Lear-25 aircraft, and measured the absorption line shapes of the CO2 line using 20 wavelength samples per scan. Measurements were made at stepped altitudes from 3 to 12.6 km over the Lamont OK, central Illinois, North Carolina, and over the Virginia Eastern Shore. Although the received signal energies were weaker than expected for ASCENDS, clear C02 line shapes were observed at all altitudes. Most flights had 5-6 altitude steps with 200-300 seconds of recorded measurements per step. We averaged every 10 seconds of measurements and used a cross-correlation approach to estimate the range to the scattering surface and the echo pulse energy at each wavelength. We then solved for the best-fit CO2 absorption line shape, and calculated the DOD of the fitted CO2 line, and computed its statistics at the various altitude steps. We compared them to CO2 optical depths calculated from spectroscopy based on HITRAN 2008 and the column number densities calculated from the airborne in-situ readings. The 2009 measurements have been analyzed in detail and they were similar on all flights. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. They showed the expected nearly the linear dependence of DOD vs

  19. Operating range of a differential-absorption lidar based on a CO{sub 2} laser

    SciTech Connect

    Ivashchenko, M V; Sherstov, I V

    2000-08-31

    The echolocation range and the remote sensing of ethylene in the atmosphere are simulated for a differential-absorption lidar based on TEA CO{sub 2} lasers. The dependence of the lidar echolocation range on the energy and the peak power of probe pulses is shown to be close to logarithmic. It is demonstrated that the use of narrow-band spectral filters is justified only for low-noise detectors and viewing angles of the receiver exceeding 5 mrad. The relative measurement error of the ethylene concentration in the atmosphere is estimated for various detection modes. (laser applications and other topics in quantum electronics)

  20. Advances in Diode-Laser-Based Water Vapor Differential Absorption Lidar

    NASA Astrophysics Data System (ADS)

    Spuler, Scott; Repasky, Kevin; Morley, Bruce; Moen, Drew; Weckwerth, Tammy; Hayman, Matt; Nehrir, Amin

    2016-06-01

    An advanced diode-laser-based water vapor differential absorption lidar (WV-DIAL) has been developed. The next generation design was built on the success of previous diode-laser-based prototypes and enables accurate measurement of water vapor closer to the ground surface, in rapidly changing atmospheric conditions, and in daytime cloudy conditions up to cloud base. The lidar provides up to 1 min resolution, 150 m range resolved measurements of water vapor in a broad range of atmospheric conditions. A description of the instrument and results from its initial field test in 2014 are discussed.

  1. Feasibility of tropospheric water vapor profiling using infrared heterodyne differential absorption lidar

    SciTech Connect

    Grund, C.J.; Hardesty, R.M.; Rye, B.J.

    1995-04-03

    Continuous, high quality profiles of water vapor, free of systematic bias, and of moderate temporal and spatial resolution, acquired over long periods at low operational and maintenance cost, are fundamental to the success of the ARM CART program. The development and verification of realistic climate model parameterizations for clouds and net radiation balance, and the correction of other CART site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. Application of profiles acquired with current techniques, have, to date, been limited by vertical resolution and uniqueness of solution [e.g. high resolution infrared (IR) Fourier transform radiometry], poor spatial and temporal coverage and high operating cost (e.g. radiosondes), or diminished daytime performance, lack of eye-safety, and high maintenance cost (e.g. Raman lidar). Recent developments in infrared laser and detector technology make possible compact IR differential absorption lidar (DIAL) systems at eye-safe wavelengths. In the study reported here, we develop DIAL system performance models and examine the potential of to solve some of the shortcomings of previous methods using parameterizations representative of current technologies. These models are also applied to diagnose and evaluate other strengths and weaknesses unique to the DIAL method for this application. This work is to continue in the direction of evaluating yet smaller and lower-cost laser diode-based systems for routine monitoring of the lower altitudes using photon counting detection methods. We regard the present report as interim in nature and will update and extend it as a final report at the end of the term of the contract.

  2. Insect monitoring with fluorescence lidar techniques: feasibility study.

    PubMed

    Brydegaard, Mikkel; Guan, Zuguang; Wellenreuther, Maren; Svanberg, Sune

    2009-10-20

    We investigate the possibilities of light detection and ranging (lidar) techniques to study migration of the damselfly species Calopteryx splendens and C. virgo. Laboratory and testing-range measurements at a distance of 60 m were performed using dried, mounted damselfly specimens. Laboratory measurements, including color photography in polarized light and spectroscopy of reflectance and induced fluorescence, reveal that damselflies exhibit reflectance and fluorescence properties that are closely tied to the generation of structural color. Lidar studies on C. splendens of both genders show that gender can be remotely determined, especially for specimens that were marked with Coumarin 102 and Rhodamine 6G dyes. The results obtained in this study will be useful for future field experiments, and provide guidelines for studying damselflies in their natural habitat using lidar to survey the air above the river surface. The findings will be applicable for many other insect species and should, therefore, bring new insights into migration and movement patterns of insects in general. PMID:19844299

  3. Analysis of Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption from 3-13 km Altitudes

    NASA Technical Reports Server (NTRS)

    Abshire, James B.; Weaver, Clark J.; Riris, Haris; Mao, Jianping; Sun, Xiaoli; Allan, Graham R.; Hasselbrack, William; Browell, Edward V.

    2011-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS space mission [1]. It uses two pulsed laser transmitters allowing simultaneous measurement of a CO2 absorption line in the 1575 nm band, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are precisely stepped in wavelength across the CO2 line and an O2 line region during the measurement. The direct detection receiver measures the energies of the laser echoes from the surface along with the range profile of scattering in the path. The column densities for the CO2 and O2 gases are estimated from the ratio of the on- and off-line signals via the integrated path differential absorption (IPDA) technique. The time of flight of the laser pulses is used to estimate the height of the scattering surface and to reject laser photons scattered in the atmosphere. We developed an airborne lidar to demonstrate an early version of the CO2 measurement from the NASA Glenn Lear-25 aircraft. The airborne lidar stepped the pulsed laser's wavelength across the selected CO2 line with 20 wavelength steps per scan. The line scan rate is 450 Hz, the laser pulse widths are 1 usec, and laser pulse energy is 24 uJ. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a NIR photomultiplier and is recorded on every other reading by a photon counting system [2]. During August 2009 we made a series of 2.5 hour long flights and measured the atmospheric CO2 absorption and line shapes using the 1572.33 nm CO2 line. Measurements were made at stepped altitudes from 3-13 km over locations in the US, including the SGP ARM site in Oklahoma, central Illinois, north-eastern North Carolina, and over the Chesapeake Bay and the eastern shore of Virginia. Although the received signal energies were weaker than expected for ASCENDS, clear CO2 line shapes were observed at all altitudes, and some measurements were made

  4. Analysis of Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption During the ASCENDS 2009-2011 Airborne Campaigns

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.; Weaver, C. J.; Riris, H.; Mao, J.; Sun, X; Allan, G. R.; Hasselbrack, W. E.; Browell, E. V.

    2012-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission and have demonstrated the CO2 and O2 measurements from aircraft. Our technique uses two pulsed lasers allowing simultaneous measurement of a single CO2 absorption line near 1572 nm, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are stepped in wavelength across the CO2 line and an O2 line doublet during the measurement. The column densities for the CO2 and O2 are estimated from the differential optical depths (DOD) of the scanned absorption lines via the IPDA technique. For the 2009 ASCENDS campaign we flew the CO2 lidar on a Lear-25 aircraft, and measured the absorption line shapes of the CO2 line using 20 wavelength samples per scan. Measurements were made at stepped altitudes from 3 to 12.6 km over the Lamont OK, central Illinois, North Carolina, and over the Virginia Eastern Shore. Although the received signal energies were weaker than expected for ASCENDS, clear CO2 line shapes were observed at all altitudes. Most flights had 5-6 altitude steps with 200-300 seconds of recorded measurements per step. We averaged every 10 seconds of measurements and used a cross-correlation approach to estimate the range to the scattering surface and the echo pulse energy at each wavelength. We then solved for the best-fit CO2 absorption line shape, and calculated the DOD of the fitted CO2 line, and computed its statistics at the various altitude steps. We compared them to CO2 optical depths calculated from spectroscopy based on HITRAN 2008 and the column number densities calculated from the airborne in-situ readings. The 2009 measurements have been analyzed and they were similar on all flights. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. They showed the expected nearly the linear dependence of DOD vs altitude. The

  5. Analysis of Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption during the ASCENDS 2009-2011 Airborne Campaigns

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Weaver, C. J.; Riris, H.; Mao, J.; Sun, X.; Allan, G.; Hasselbrack, W.; Browell, E. V.

    2011-12-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission and have demonstrated the CO2 and O2 measurements from aircraft. Our technique uses two pulsed lasers allowing simultaneous measurement of a single CO2 absorption line near 1572 nm, O2 extinction in the Oxygen A-band, surface height and backscatter profile. The lasers are stepped in wavelength across the CO2 line and an O2 line doublet during the measurement. The column densities for the CO2 and O2 are estimated from the differential optical depths (DOD) of the scanned absorption lines via the IPDA technique. For the 2009 ASCENDS campaign we flew the CO2 lidar on a Lear-25 aircraft, and measured the absorption line shapes of the CO2 line using 20 wavelength samples per scan. Measurements were made at stepped altitudes from 3 to 12.6 km over the Lamont OK, central Illinois, North Carolina, and over the Virginia Eastern Shore. Although the received signal energies were weaker than expected for ASCENDS, clear CO2 line shapes were observed at all altitudes. Most flights had 5-6 altitude steps with 200-300 seconds of recorded measurements per step. We averaged every 10 seconds of measurements and used a cross-correlation approach to estimate the range to the scattering surface and the echo pulse energy at each wavelength. We then solved for the best-fit CO2 absorption line shape, and calculated the DOD of the fitted CO2 line, and computed its statistics at the various altitude steps. We compared them to CO2 optical depths calculated from spectroscopy based on HITRAN 2008 and the column number densities calculated from the airborne in-situ readings. The 2009 measurements have been analyzed in detail and they were similar on all flights. The results show clear CO2 line shape and absorption signals, which follow the expected changes with aircraft altitude from 3 to 13 km. They showed the expected nearly the linear dependence of DOD vs

  6. Absorption technique for OH measurements and calibration

    NASA Technical Reports Server (NTRS)

    Bakalyar, D. M.; James, J. V.; Wang, C. C.

    1982-01-01

    An absorption technique is described which utilizes a stabilized frequency-doubled tunable dye laser and a long-path White cell with high mirror reflectivities both in the red and UV. In laboratory conditions it has been possible to routinely obtain a detection sensitivity of 3 parts in 1,000,000 over absorption paths less than 1 m in length and a detection sensitivity of approximately 6 parts in 100,000 over an absorption path of the order of 1 km. The latter number corresponds to 3,000,000 OH molecules/cu cm, and therefore the technique should be particularly useful for calibration the fluorescence instrument for OH measurements. However, the presence of atmospheric fluctuations coupled with intensity variation accompanying frequency scanning appears to degrade the detection sensitivity in outdoor ambient conditions, thus making it unlikely that this technique can be employed for direct OH monitoring.

  7. Advanced intensity-modulation continuous-wave lidar techniques for ASCENDS CO2 column measurements

    NASA Astrophysics Data System (ADS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. W.; Obland, Michael D.; Meadows, Byron

    2015-10-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

  8. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for ASCENDS O2 Column Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. Wallace; Obland, Michael D.; Meadows, Byron

    2015-01-01

    Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements.

  9. New remote sensing technique for lidar monitoring of atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Belen'kii, Mikhail S.; Gimmestad, Gary G.

    1993-09-01

    A new remote sensing technique is proposed for determining the turbulent parameters of the atmosphere using a single-ended lidar system. This technique is based on the enhanced backscattering effect and is insensitive to the scattering volume averaging effect on the intensity fluctuations of the reflected wave and the sounding beam. The corresponding measurements are independent of the turbulent scintillation spectrum and that permits the use of high power pulsed lasers with a relatively low repetition rate for determining the refractive index structure characteristic Cn2, its vertical profile Cn2(h) and inner scale of turbulence lo in the atmosphere. A theory of the method is developed, and the conditions are obtained for observing the backscattering amplification effect in the atmosphere with a laser beam scattered by aerosol. The signal-to-noise ratio and the sensitivity of the measured quantities to the inner scale of turbulence lo variations are estimated. A planned demonstration of this technique in the boundary layer of the atmosphere with an eyesafe lidar which has been developed at Georgia Tech is discussed.

  10. Ultra Narrowband Optical Filters for Water Vapor Differential Absorption Lidar (DIAL) Atmospheric Measurements

    NASA Technical Reports Server (NTRS)

    Stenholm, Ingrid; DeYoung, Russell J.

    2001-01-01

    Differential absorption lidar (DIAL) systems are being deployed to make vertical profile measurements of atmospheric water vapor from ground and airborne platforms. One goal of this work is to improve the technology of such DIAL systems that they could be deployed on space-based platforms. Since background radiation reduces system performance, it is important to reduce it. One way to reduce it is to narrow the bandwidth of the optical receiver system. However, since the DIAL technique uses two or more wavelengths, in this case separated by 0.1 nm, a fixed-wavelength narrowband filter that would encompass both wavelengths would be broader than required for each line, approximately 0.02 nm. The approach employed in this project is to use a pair of tunable narrowband reflective fiber Bragg gratings. The Bragg gratings are germanium-doped silica core fiber that is exposed to ultraviolet radiation to produce index-of-refraction changes along the length of the fiber. The gratings can be tuned by stretching. The backscattered laser radiation is transmitted through an optical circulator to the gratings, reflected back to the optical circulator by one of the gratings, and then sent to a photodiode. The filter reflectivities were >90 percent, and the overall system efficiency was 30 percent.

  11. Extended Kalman filter for multiwavelength differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Warren, Russell E.; Vanderbeek, Richard G.

    2001-08-01

    Our earlier study described an approach for estimating the path-integrated concentration, CL, of a set of vapor materials using time series data from topographic backscatter lidar with frequency-agile lasers. That methodology assumed the availability of background data samples collected before the release of the vapors of interest to estimate statistical parameters such as the mean topographic backscatter return and the transmitter energy mean and variance as a function of wavelength. The background data were then used in an extended Kalman filter approach for estimating the CL components as a function of time. That approach worked well for data that showed negligible drift in the mean parameters over the data collection time. In practice, however, the transmitter energy and background return can drift, producing substantial bias in the estimates. In this paper we generalize the approach to a more complete state model that includes the mean transmitter energy and background return in addition to the CL vapor set. This generalization allows the algorithm to track slow drift in those parameters and provides generally improved estimates. Results of the new algorithm are compared with those of a two-wavelength classical DIAL estimator on synthetic and field test data.

  12. A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

    2012-01-01

    A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

  13. Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km Altitudes

    NASA Technical Reports Server (NTRS)

    Abshire, J. B.; Riris, H.; Allan, G. R.; Weaver, C.; Hasselbrack, W.; Sun, X.

    2009-01-01

    We have developed a lidar technique for measuring the tropospheric C02 concentrations as a candidate for NASA's planned ASCENDS mission. Our technique uses two pulsed laser transmitters allowing simultaneous measurement of a C02 absorption line in the 1570 nm band, 02 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are stepped in wavelength across the C02 line and an 02 line region during the measurement. The receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the C02 and 02 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface, and to reject laser photons scattered in the atmosphere. We have developed an airborne lidar to demonstrate the C02 measurement from the NASA Glenn Lear 25 aircraft. The airborne lidar steps the pulsed laser's wavelength across a selected C02 line with 20 steps per scan. The line scan rate is 450 Hz and laser pulse widths are I usec. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. We made initial airborne measurements on flights during October and December 2008. Laser backscatter and absorption measurements were made over a variety of land and water surfaces and through thin and broken clouds. Atmospheric C02 column measurements using the 1571.4, 1572.02 and 1572.33 nm C02 lines. Two flights were made above the DOE SGP ARM site at altitudes from 3-8 km. These nights were coordinated with DOE investigators who Hew an in-situ C02 sensor on a Cessna aircraft under the path. The increasing C02 line absorptions with

  14. Pulsed Airborne Lidar Measurements of Atmospheric CO2 Column Absorption and Line Shapes from 3-13 km Altitudes

    NASA Technical Reports Server (NTRS)

    Abshire, James; Riris, Haris; Allan, Graham; Weaver, Clark; Mao, Jianping; Sun, Xiaoli; Hasselbrack, William

    2010-01-01

    We have developed a pulsed lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's planned ASCENDS space mission. Our technique uses two pulsed laser transmitters allowing simultaneous measurement of a CO2 absorption line in the 1570 nm band, O2 extinction in the Oxygen A-band and surface height and backscatter. The lidar measures the energy and time of flight of the laser echoes reflected from the atmosphere and surface. The lasers are rapidly and precisely stepped in wavelength across the CO2 line and an O2 line region during the measurement. The direct detection receiver uses a telescope and photon counting detectors, and measures the background light and energies of the laser echoes from the surface along with scattering from any aerosols in the path. The gas extinction and column densities for the CO2 and O2 gases are estimated from the ratio of the on- and off- line signals via the DIAL technique. Time gating is used to isolate the laser echo signals from the surface, and to reject laser photons scattered in the atmosphere. The time of flight of the laser pulses are also used to estimate the height of the scattering surface and to identify cases of mixed cloud and ground scattering. We have developed an airborne lidar to demonstrate the CO2 measurement from the NASA Glenn Lear-25 aircraft. The airborne lidar steps the pulsed laser's wavelength across the selected CO2 line with 20 steps per scan. The line scan rate is 450 Hz, the laser pulse widths are 1 usec, and laser pulse energy is 24 uJ. The time resolved laser backscatter is collected by a 20 cm telescope, detected by a photomultiplier and is recorded by a photon counting system. We made initial airborne measurements on flights during fall 2008. Laser backscatter and absorption measurements were made over a variety of land and water surfaces and through thin clouds. The atmospheric CO2 column measurements using the 1572.33 nm CO2 lines. Two flights were made above the

  15. New Examination of the Raman Lidar Technique for Water Vapor and Aerosols. Paper 1; Evaluating the Temperature Dependent Lidar Equations

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.

    2003-01-01

    The intent of this paper and its companion is to compile together the essential information required for the analysis of Raman lidar water vapor and aerosol data acquired using a single laser wavelength. In this first paper several details concerning the evaluation of the lidar equation when measuring Raman scattering are considered. These details include the influence of the temperature dependence of both pure rotational and vibrational-rotational Raman scattering on the lidar profile. These are evaluated for the first time using a new form of the lidar equation. The results indicate that, for the range of temperatures encountered in the troposphere, the magnitude of the temperature dependent effect can reach 10% or more for narrowband Raman water vapor measurements. Also the calculation of atmospheric transmission is examined carefully including the effects of depolarization. Different formulations of Rayleigh cross section determination commonly used in the lidar field are compared revealing differences up to 5% among the formulations. The influence of multiple scattering on the measurement of aerosol extinction using the Raman lidar technique is considered as are several photon pulse-pileup correction techniques.

  16. Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements

    NASA Technical Reports Server (NTRS)

    Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

    2012-01-01

    We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

  17. Error reduction methods for integrated-path differential-absorption lidar measurements.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2012-07-01

    We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

  18. Absorption spectroscopy: technique provides extremely high sensitivity.

    PubMed

    Provencal, R A; Paul, J B; Michael, E; Saykally, R J

    1998-06-01

    Technology associated with cavity ringdown laser absorption spectroscopy is reviewed. The technique is used to study general trace analysis, free radicals in flames and chemical reactors, molecular ions in electrical discharges, biological molecules and water clusters in supersonic jets, and vibrational overtones of stable molecules. Its specific enough to detect about 1-ppm fractional absorption by a gaseous sample in about 10 microseconds. The use of mirrors in ringdown sepctroscopy is explained. Other topics include the generation of pulsed infrared rays and the adaptation of ringdown spectroscopy for use with narrow-bandwidth continuous-wave lasers. PMID:11541906

  19. Double-Edge Molecular Technique for Doppler Lidar Wind Measurement

    NASA Technical Reports Server (NTRS)

    Flesia, Cristina; Korb, C. Laurence

    1998-01-01

    The double-edge lidar technique for measuring the wind using molecular backscatter is described. Two high spectral resolution edge filters are located in the wings of the Rayleigh-Brillouin profile. This doubles the signal change per unit Doppler shift, the sensitivity, and gives nearly a factor of two improvement in measurement accuracy. The use of a crossover region is described where the sensitivity of a molecular and aerosol-based measurement are equal. This desensitizes the molecular measurement to the effects of aerosol scattering over a frequency range of +/- 100 m/s. We give methods for correcting for short-term frequency jitter and drift using a laser reference frequency measurement and methods for long-term frequency correction using a servo control system. The effects of Rayleigh-Brillouin scattering on the measurement are shown to be significant and are included in the analysis. Simulations for a conical scanning satellite-based lidar at 355 nm show an accuracy of 2-3 m/s for altitudes of 2 to 15 km for a 1 km vertical resolution, a satellite altitude of 400 km and a 200 km x 200 km spatial resolution. Results of ground based wind measurements are presented.

  20. New experimental method for lidar overlap factor using a CCD side-scatter technique.

    PubMed

    Wang, Zhenzhu; Tao, Zongming; Liu, Dong; Wu, Decheng; Xie, Chenbo; Wang, Yingjian

    2015-04-15

    In theory, lidar overlap factor can be derived from the difference between the particle backscatter coefficient retrieved from lidar elastic signal without overlap correction and the actual particle backscatter coefficient, which can be obtained by other measured techniques. The side-scatter technique using a CCD camera is testified to be a powerful tool to detect the particle backscatter coefficient in near ground layer during night time. A new experiment approach to determine the overlap factor for vertically pointing lidar is presented in this study, which can be applied to Mie lidars. The effect of overlap factor on Mie lidar is corrected by an iteration algorithm combining the retrieved particle backscatter coefficient using CCD side-scatter method and Fernald method. This method has been successfully applied to Mie lidar measurements during a routine campaign, and the comparison of experimental results in different atmosphere conditions demonstrated that this method is available in practice.

  1. Aerosol analysis techniques and results from micro pulse lidar

    NASA Technical Reports Server (NTRS)

    Hlavka, Dennis L.; Spinhirne, James D.; Campbell, James R.; Reagan, John A.; Powell, Donna

    1998-01-01

    The effect of clouds and aerosol on the atmospheric energy balance is a key global change problem. Full knowledge of aerosol distributions is difficult to obtain by passive sensing alone. Aerosol and cloud retrievals in several important areas can be significantly improved with active remote sensing by lidar. Micro Pulse Lidar (MPL) is an aerosol and cloud profilometer that provides a detailed picture of the vertical structure of boundary layer and elevated dust or smoke plume aerosols. MPL is a compact, fully eyesafe, ground-based, zenith pointing instrument capable of full-time, long-term unattended operation at 523 nm. In October of 1993, MPL began taking full-time measurements for the Atmospheric Radiation Measurement (ARM) program at its Southern Great Plains (SGP) site and has since expanded to ARM sites in the Tropical West Pacific (TWP) and the North Slope of Alaska (NSA). Other MPL's are moving out to some of the 60 world-wide Aerosol Robotic Network (AERONET) sites which are already equipped with automatic sun-sky scanning spectral radiometers providing total column optical depth measurements. Twelve additional MPL's have been purchased by NASA to add to the aerosol and cloud database of the EOS ground validation network. The original MPL vertical resolution was 300 meters but the newer versions have a vertical resolution of 30 meters. These expanding data sets offer a significant new resource for atmospheric radiation analysis. Under the direction of Jim Spinhirne, the MPL analysis team at NASA/GSFC has developed instrument correction and backscatter analysis techniques for ARM to detect cloud boundaries and analyze vertical aerosol structures. A summary of MPL applications is found in Hlavka (1997). With the aid of independent total column optical depth instruments such as the Multifilter Rotating Shadowband Radiometer (MFRSR) at the ARM sites or sun photometers at the AERONET sites, the MPL data can be calibrated, and time-resolved vertical profiles of

  2. Development of a Coherent Differential Absorption Lidar for Range Resolved Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulgueta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo. C.; Koch, Grady J.; Beyon, Jeffery J.; Singh, Upendra N.

    2010-01-01

    A pulsed, 2-m coherent Differential Absorption Lidar (DIAL) / Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument will measure atmospheric CO2 profiles (by DIAL) initially from a ground platform, and then be prepared for aircraft installation to measure the atmospheric CO2 column densities in the atmospheric boundary layer (ABL) and lower troposphere. The airborne prototype CO2 lidar can measure atmospheric CO2 column density in a range bin of 1km with better than 1.5% precision at horizontal resolution of less than 50km. It can provide the image of the pooling of CO2 in lowlying areas and performs nighttime mass balance measurements at landscape scale. This sensor is unique in its capability to study the vertical ABL-free troposphere exchange of CO2 directly. It will allow the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop.

  3. Analysis of Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption in the ASCENDS 2011 and 2013 Airborne Campaigns

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Ramanathan, A.; Mao, J.; Riris, H.; Allan, G. R.; Hasselbrack, W.; Weaver, C. J.; Browell, E. V.

    2013-12-01

    We have developed a pulsed, wavelength-resolved IPDA lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission. The CO2 lidar flies on NASA's DC-8 aircraft and measures the atmospheric backscatter profiles and shape of the 1572.33 nm absorption line using 250 mW average laser power, 30 wavelength samples per scan with 300 scans per second. Our post-flight analysis estimates the lidar range and pulse energies at each wavelength every second. We then solve for the optimum CO2 absorption line shape, and calculated the Differential Optical Depth (DOD) at the line peak and the column average CO2 concentrations. We compared these to radiative transfer calculations based on the HITRAN 2008 database, the atmospheric conditions, and the CO2 concentrations sampled by in-situ sensors on the aircraft. Our team participated in the ASCENDS science flights during July and August 2011. These flights were made over a wide variety of surface and cloud conditions near the US, including over the central valley of California, over several mountain ranges, over both broken and solid stratus cloud deck over the Pacific Ocean, over thin and broken clouds above the US Southwest and Iowa, and over forests near the WLEF tower in Wisconsin. Most flights had 5-6 altitude steps to > 12 km, and clear CO2 absorption line shapes were recorded. Analyses show the retrievals of lidar range and CO2 column absorption, as well as estimates of CO2 mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity, through thin clouds and to stratus cloud tops. For regions where the CO2 concentration was relatively constant, the measured CO2 absorption profile (averaged for 50 sec) matched the predicted profile to better than 1% RMS error for all flight altitudes. For 10 second averaging, the scatter in the retrievals was typically 2-3 ppm and was limited by signal shot noise (i.e. the signal photon count). For flight

  4. New differential absorption lidar for stratospheric ozone monitoring in Patagonia, South Argentina

    NASA Astrophysics Data System (ADS)

    Wolfram, E. A.; Salvador, J.; D'Elia, R.; Casiccia, C.; Paes Leme, N.; Pazmiño, A.; Porteneuve, J.; Godin-Beekman, S.; Nakane, H.; Quel, E. J.

    2008-10-01

    As part of environmental studies concerned with measurements of the stratospheric ozone layer, CEILAP has developed a new differential absorption lidar (DIAL) instrument. Since the initial construction of the first DIAL instrument, the Lidar Division of CEILAP has made important financial and scientific investments to upgrade this initial prototype. The new version has a bigger reception system formed by four Newtonian telescopes, each of 50 cm diameter, and a larger number of detection channels: four different wavelengths are detected simultaneously and six digital channels record the Rayleigh and Raman backscattered photons emitted by a ClXe excimer laser at 308 nm and the third harmonic of a Nd-YAG laser at 355 nm. A number of different changes have been made to increase the dynamic range of this lidar: a mechanical chopper was installed together with a gated photomultiplier in the high-energy detection channels to avoid the detector being overloaded by strong signals from lower atmospheric layers. This new version was installed inside a shelter, giving the possibility to make field campaigns outside CEILAP laboratories, for example the SOLAR campaign made in the Argentine Patagonian region during 2005 and 2006 spring periods. In this paper a full description of the instrument update is given. Intercomparisons with the ozone sonde and satellite platform instrument are presented. The results show agreement better than 10% in 16-38 km altitude range when the same airmasses are sampled. The comparison with five quasi-coincident sondes launched in Punta Arenas during spring 2005 shows good agreement between both types of measurement, with relative differences inside 1σ deviation of the lidar measurement. The comparison of the integral of height integrated lidar profiles with total ozone column measured with a Brewer photometer shows good agreement, with relative differences less than 10%.

  5. Multiple-scattering effect on ozone retrieval from space-based differential absorption lidar measurements.

    PubMed

    Pal, S R; Bissonnette, L R

    1998-09-20

    Single-scattering and multiple-scattering lidar signals are calculated for a spaceborne differential absorption lidar system for global ozone measurements at the on and off wavelength pair at 305 and 315 nm. The effect of multiple scattering is found to be negligible on stratospheric and tropospheric ozone retrieval under background stratospheric aerosol. Under low-visibility conditions in the planetary boundary layer the presence of multiple scattering causes an overestimation in maritime aerosol and an underestimation in urban as well as in rural aerosol. This effect is also examined in three cirrus models. The multiple scattering does not permit accurate ozone retrieval within cirrus; however, below it the solution recovers somewhat with generally an underestimation depending on the type and density of cirrus. The effect of aerosol and Rayleigh extinction on the ozone retrieval is also discussed.

  6. Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for Column CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Campbell, J. F.; Lin, B.; Nehrir, A. R.; Obland, M. D.; Liu, Z.; Browell, E. V.; Chen, S.; Kooi, S. A.; Fan, T. F.

    2015-12-01

    Global and regional atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission and Atmospheric Carbon and Transport (ACT) - America airborne investigation are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity-Modulated Continuous-Wave (IM-CW) lidar techniques are being investigated as a means of facilitating CO2 measurements from space and airborne platforms to meet the mission science measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud returns. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of intervening optically thin clouds, thereby minimizing bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the Earth's surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques and provides very high (at sub-meter level) range resolution. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These techniques are used in a new data processing architecture to support the ASCENDS CarbonHawk Experiment Simulator (ACES) and ACT-America programs.

  7. Challenges and Solutions for Frequency and Energy References for Spaceborne and Airborne Integrated Path Differential Absorption Lidars

    NASA Astrophysics Data System (ADS)

    Fix, Andreas; Quatrevalet, Mathieu; Witschas, Benjamin; Wirth, Martin; Büdenbender, Christian; Amediek, Axel; Ehret, Gerhard

    2016-06-01

    The stringent requirements for both the frequency stability and power reference represent a challenging task for Integrated Path Differential Absorption Lidars (IPDA) to measure greenhouse gas columns from satellite or aircraft. Currently, the German-French methane mission MERLIN (Methan Remote Lidar Mission) is prepared. At the same time CHARM-F, an aircraft installed system has been developed at DLR as an airborne demonstrator for a spaceborne greenhouse gas mission. The concepts and realization of these important sub-systems are discussed.

  8. Effect of differential spectral reflectance on DIAL measurements using topographic targets. [Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Grant, W. B.

    1982-01-01

    Differential absorption lidar (DIAL) measurements of atmospheric gases and temperature made using topographic targets to provide the backscattered signal are subject to errors from the differential spectral reflectance of the target materials. The magnitude of this effect is estimated for a number of DIAL measurements reported in the literature. Calculations are presented for several topographic targets. In general the effect on a DIAL measurement increases directly with increasing wavelength and laser line separation, and inversely with differential absorption coefficient and distance to the target. The effect can be minimized by using tunable or isotope lasers to reduce the laser line separation or by using additional reference wavelengths to determine the surface differential spectral reflectance.

  9. Atmospheric effects on CO{sub 2} differential absorption lidar sensitivity

    SciTech Connect

    Petrin, R.R.; Nelson, D.H.; Schmitt, M.J.

    1996-03-01

    The ambient atmosphere between the laser transmitter and the target can affect CO{sub 2} differential absorption lidar (DIAL) measurement sensitivity through a number of different processes. In this work, we will address two of the sources of atmospheric interference with CO{sub 2} DIAL measurements: effects due to beam propagation through atmospheric turbulence and extinction due to absorption by atmospheric gases. Measurements of atmospheric extinction under different atmospheric conditions are presented and compared to a standard atmospheric transmission model (FASCODE). We have also investigated the effects of atmospheric turbulence on system performance. Measurements of the effective beam size after propagation are compared to model predictions using simultaneous measurements of atmospheric turbulence as input to the model. These results are also discussed in the context of the overall effect of beam propagation through atmospheric turbulence on the sensitivity of DIAL measurements.

  10. Development of a differential absorption lidar for identification of carbon sequestration site leakage

    NASA Astrophysics Data System (ADS)

    Johnson, William Eric

    This thesis describes the development and deployment of a near-infrared scanning micropulse differential absorption lidar (DIAL) system for monitoring carbon dioxide sequestration site integrity. The DIAL utilizes a custom-built lidar (light detection and ranging) transmitter system based on two commercial tunable diode lasers operating at 1.571 microm, an acousto-optic modulator, fiber optic switches, and an Erbium-doped fiber amplifier to generate 65 microJ 200 ns pulses at a 15 kHz repetition rate. Backscattered laser transmitter light is collected with an 11 inch Schmidt-Cassegrain telescope where it is optically filtered to reduce background noise. A fiber-coupled photomultiplier tube operating in the photon counting mode is then used to monitor the collected return signal. Averaging over periods typically of one hour permit range-resolved measurements of carbon dioxide from 1 to 2.5 km with a typical error of 40 ppm. For monitoring a field site, the system scans over a field area by pointing the transmitter and receiver with a computer controlled motorized commercial telescope base. The system has made autonomous field measurements in an agricultural field adjacent to Montana State University and at the Kevin Dome carbon sequestration site in rural northern Montana. Comparisons have been made with an in situ sensor showing agreement between the two measurements to within the 40 error of the DIAL. In addition to the work on the 1.57 micron DIAL, this thesis also presents work done at NASA Langley Research Center on the development and deployment of a 2 micron integrated path differential absorption (IPDA) lidar. The 2 micron system utilizes a low repetition rate 140 mJ double pulsed Ho:Tm:YLF laser developed at NASA Langley.

  11. Rotational vibrational-rotational Raman differential absorption lidar for atmospheric ozone measurements: methodology and experiment.

    PubMed

    Reichardt, J; Bisson, S E; Reichardt, S; Weitkamp, C; Neidhart, B

    2000-11-20

    A single-laser Raman differential absorption lidar (DIAL) for ozone measurements in clouds is proposed. An injection-locked XeCl excimer laser serves as the radiation source. The ozone molecule number density is calculated from the differential absorption of the anti-Stokes rotational Raman return signals from molecular nitrogen and oxygen as the on-resonance wavelength and the vibrational-rotational Raman backscattering from molecular nitrogen or oxygen as the off-resonance wavelength. Model calculations show that the main advantage of the new rotational vibrational-rotational (RVR) Raman DIAL over conventional Raman DIAL is a 70-85% reduction in the wavelength-dependent effects of cloud-particle scattering on the measured ozone concentration; furthermore the complexity of the apparatus is reduced substantially. We describe a RVR Raman DIAL setup that uses a narrow-band interference-filter polychromator as the lidar receiver. Single-laser ozone measurements in the troposphere and lower stratosphere are presented, and it is shown that on further improvement of the receiver performance, ozone measurements in clouds are attainable with the filter-polychromator approach.

  12. Wavelength Locking to CO2 Absorption Line-Center for 2-Micron Pulsed IPDA Lidar Application

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Petros, Mulugeta; Antill, Charles W.; Singh, Upendra N.; Yu, Jirong

    2016-01-01

    An airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar is currently under development at NASA Langley Research Center (LaRC). This IPDA lidar system targets both atmospheric carbon dioxide (CO2) and water vapor (H2O) column measurements. Independent wavelength control of each of the transmitted laser pulses is a key feature for the success of this instrument. The wavelength control unit provides switching, tuning and locking for each pulse in reference to a 2-micron CW (Continuous Wave) laser source locked to CO2 line-center. Targeting the CO2 R30 line center, at 2050.967 nanometers, a wavelength locking unit has been integrated using semiconductor laser diode. The CO2 center-line locking unit includes a laser diode current driver, temperature controller, center-line locking controller and CO2 absorption cell. This paper presents the CO2 center-line locking unit architecture, characterization procedure and results. Assessment of wavelength jitter on the IPDA measurement error will also be addressed by comparison to the system design.

  13. A robust optical parametric oscillator and receiver telescope for differential absorption lidar of greenhouse gases

    NASA Astrophysics Data System (ADS)

    Robinson, Iain; Jack, James W.; Rae, Cameron F.; Moncrieff, John B.

    2015-10-01

    We report the development of a differential absorption lidar instrument (DIAL) designed and built specifically for the measurement of anthropogenic greenhouse gases in the atmosphere. The DIAL is integrated into a commercial astronomical telescope to provide high-quality receiver optics and enable automated scanning for three-dimensional lidar acquisition. The instrument is portable and can be set up within a few hours in the field. The laser source is a pulsed optical parametric oscillator (OPO) which outputs light at a wavelength tunable near 1.6 μm. This wavelength region, which is also used in telecommunications devices, provides access to absorption lines in both carbon dioxide at 1573 nm and methane at 1646 nm. To achieve the critical temperature stability required for a laserbased field instrument the four-mirror OPO cavity is machined from a single aluminium block. A piezoactuator adjusts the cavity length to achieve resonance and this is maintained over temperature changes through the use of a feedback loop. The laser output is continuously monitored with pyroelectric detectors and a custom-built wavemeter. The OPO is injection seeded by a temperature-stabilized distributed feedback laser diode (DFB-LD) with a wavelength locked to the absorption line centre (on-line) using a gas cell containing pure carbon dioxide. A second DFB-LD is tuned to a nearby wavelength (off-line) to provide the reference required for differential absorption measurements. A similar system has been designed and built to provide the injection seeding wavelengths for methane. The system integrates the DFB-LDs, drivers, locking electronics, gas cell and balanced photodetectors. The results of test measurements of carbon dioxide are presented and the development of the system is discussed, including the adaptation required for the measurement of methane.

  14. Self-Calibration and Laser Energy Monitor Validations for a Double-Pulsed 2-Micron CO2 Integrated Path Differential Absorption Lidar Application

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Singh, Upendra N.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong

    2015-01-01

    Double-pulsed 2-micron integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photo-electromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-micron IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

  15. On-Line Wavelength Calibration of Pulsed Laser for CO2 Differential Absorption LIDAR

    NASA Astrophysics Data System (ADS)

    Xiang, Chengzhi; Ma, Xin; Han, Ge; Liang, Ailin; Gong, Wei

    2016-06-01

    Differential absorption lidar (DIAL) remote sensing is a promising technology for atmospheric CO2 detection. However, stringent wavelength accuracy and stability are required in DIAL system. Accurate on-line wavelength calibration is a crucial procedure for retrieving atmospheric CO2 concentration using the DIAL, particularly when pulsed lasers are adopted in the system. Large fluctuations in the intensities of a pulsed laser pose a great challenge for accurate on-line wavelength calibration. In this paper, a wavelength calibration strategy based on multi-wavelength scanning (MWS) was proposed for accurate on-line wavelength calibration of a pulsed laser for CO2 detection. The MWS conducted segmented sampling across the CO2 absorption line with appropriate number of points and range of widths by using a tunable laser. Complete absorption line of CO2 can be obtained through a curve fitting. Then, the on-line wavelength can be easily found at the peak of the absorption line. Furthermore, another algorithm called the energy matching was introduced in the MWS to eliminate the backlash error of tunable lasers during the process of on-line wavelength calibration. Finally, a series of tests was conducted to elevate the calibration precision of MWS. Analysis of tests demonstrated that the MWS proposed in this paper could calibrate the on-line wavelength of pulsed laser accurately and steadily.

  16. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols

    NASA Technical Reports Server (NTRS)

    Carter, Arlen F.; Allen, Robert J.; Mayo, M. Neale; Butler, Carolyn F.; Grossman, Benoist E.; Ismail, Syed; Grant, William B.; Browell, Edward V.; Higdon, Noah S.; Mayor, Shane D.; Ponsardin, Patrick; Hueser, Alene W.

    1994-01-01

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H2O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and greater than 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H2O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H2O absorption-line parameters were performed to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H2O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H2O radiosondes. The H2O distributions measured with the DIAL system differed by less than 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  17. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions.

  18. Airborne differential absorption lidar system for measurements of atmospheric water vapor and aerosols.

    PubMed

    Higdon, N S; Browell, E V; Ponsardin, P; Grossmann, B E; Butler, C F; Chyba, T H; Mayo, M N; Allen, R J; Heuser, A W; Grant, W B; Ismail, S; Mayor, S D; Carter, A F

    1994-09-20

    An airborne differential absorption lidar (DIAL) system has been developed at the NASA Langley Research Center for remote measurements of atmospheric water vapor (H(2)O) and aerosols. A solid-state alexandrite laser with a 1-pm linewidth and > 99.85% spectral purity was used as the on-line transmitter. Solid-state avalanche photodiode detector technology has replaced photomultiplier tubes in the receiver system, providing an average increase by a factor of 1.5-2.5 in the signal-to-noise ratio of the H(2)O measurement. By incorporating advanced diagnostic and data-acquisition instrumentation into other subsystems, we achieved additional improvements in system operational reliability and measurement accuracy. Laboratory spectroscopic measurements of H(2)O absorption-line parameters were perfo med to reduce the uncertainties in our knowledge of the absorption cross sections. Line-center H(2)O absorption cross sections were determined, with errors of 3-6%, for more than 120 lines in the 720-nm region. Flight tests of the system were conducted during 1989-1991 on the NASA Wallops Flight Facility Electra aircraft, and extensive intercomparison measurements were performed with dew-point hygrometers and H(2)O radiosondes. The H(2)O distributions measured with the DIAL system differed by ≤ 10% from the profiles determined with the in situ probes in a variety of atmospheric conditions. PMID:20941181

  19. 3-D water vapor field in the atmospheric boundary layer observed with scanning differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Späth, Florian; Behrendt, Andreas; Muppa, Shravan Kumar; Metzendorf, Simon; Riede, Andrea; Wulfmeyer, Volker

    2016-04-01

    High-resolution three-dimensional (3-D) water vapor data of the atmospheric boundary layer (ABL) are required to improve our understanding of land-atmosphere exchange processes. For this purpose, the scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) was developed as well as new analysis tools and visualization methods. The instrument determines 3-D fields of the atmospheric water vapor number density with a temporal resolution of a few seconds and a spatial resolution of up to a few tens of meters. We present three case studies from two field campaigns. In spring 2013, the UHOH DIAL was operated within the scope of the HD(CP)2 Observational Prototype Experiment (HOPE) in western Germany. HD(CP)2 stands for High Definition of Clouds and Precipitation for advancing Climate Prediction and is a German research initiative. Range-height indicator (RHI) scans of the UHOH DIAL show the water vapor heterogeneity within a range of a few kilometers up to an altitude of 2 km and its impact on the formation of clouds at the top of the ABL. The uncertainty of the measured data was assessed for the first time by extending a technique to scanning data, which was formerly applied to vertical time series. Typically, the accuracy of the DIAL measurements is between 0.5 and 0.8 g m-3 (or < 6 %) within the ABL even during daytime. This allows for performing a RHI scan from the surface to an elevation angle of 90° within 10 min. In summer 2014, the UHOH DIAL participated in the Surface Atmosphere Boundary Layer Exchange (SABLE) campaign in southwestern Germany. Conical volume scans were made which reveal multiple water vapor layers in three dimensions. Differences in their heights in different directions can be attributed to different surface elevation. With low-elevation scans in the surface layer, the humidity profiles and gradients can be related to different land cover such as maize, grassland, and forest as well as different surface layer

  20. Polarization-discrimination technique to maximize the lidar signal-to-noise ratio for daylight operations.

    PubMed

    Hassebo, Yasser Y; Gross, Barry; Oo, Min; Moshary, Fred; Ahmed, Samir

    2006-08-01

    The impact and potential of a polarization-selection technique to reduce the sky background signal for linearly polarized monostatic elastic backscatter lidar measurements are examined. Taking advantage of naturally occurring polarization properties in scattered skylight, we devised a polarization-discrimination technique in which both the lidar transmitter and the receiver track and minimize detected sky background noise while maintaining maximum lidar signal throughput. Lidar elastic backscatter measurements, carried out continuously during daylight hours at 532 nm, show as much as a factor of square root 10 improvement in the signal-to-noise ratio (SNR) over conventional unpolarized schemes. For vertically pointing lidars, the largest improvements are limited to the early morning and late afternoon hours, while for lidars scanning azimuthally and in elevation at angles other than vertical, significant improvements are achievable over more extended time periods with the specific times and improvement factors depending on the specific angle between the lidar and the solar axes. The resulting diurnal variations in SNR improvement sometimes show an asymmetry with the solar angle that analysis indicates can be attributed to changes in observed relative humidity that modifies the underlying aerosol microphysics and observed optical depth.

  1. Polarization-discrimination technique to maximize the lidar signal-to-noise ratio for daylight operations.

    PubMed

    Hassebo, Yasser Y; Gross, Barry; Oo, Min; Moshary, Fred; Ahmed, Samir

    2006-08-01

    The impact and potential of a polarization-selection technique to reduce the sky background signal for linearly polarized monostatic elastic backscatter lidar measurements are examined. Taking advantage of naturally occurring polarization properties in scattered skylight, we devised a polarization-discrimination technique in which both the lidar transmitter and the receiver track and minimize detected sky background noise while maintaining maximum lidar signal throughput. Lidar elastic backscatter measurements, carried out continuously during daylight hours at 532 nm, show as much as a factor of square root 10 improvement in the signal-to-noise ratio (SNR) over conventional unpolarized schemes. For vertically pointing lidars, the largest improvements are limited to the early morning and late afternoon hours, while for lidars scanning azimuthally and in elevation at angles other than vertical, significant improvements are achievable over more extended time periods with the specific times and improvement factors depending on the specific angle between the lidar and the solar axes. The resulting diurnal variations in SNR improvement sometimes show an asymmetry with the solar angle that analysis indicates can be attributed to changes in observed relative humidity that modifies the underlying aerosol microphysics and observed optical depth. PMID:16855650

  2. Advances in Direct Detection Doppler Lidar Technology and Techniques

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce; Einaudi, Franco (Technical Monitor)

    2001-01-01

    In this paper we will describe the ground based Doppler lidar system which is mounted in a modified delivery van to allow field deployment and operations. The system includes an aerosol double edge receiver optimized for aerosol backscatter Doppler measurements at 1064 nm and a molecular double edge receiver which operates at 355 nm. The lidar system will be described including details of the injection seeded diode pumped laser transmitter and the piezoelectrically tunable high spectral resolution Fabry Perot etalon which is used to measure the Doppler shift. Examples of tropospheric wind profiles obtained with the system will also be presented to demonstrate its capabilities.

  3. Development and Testing of a Differential Absorption LIDAR system for Greenhouse Gas Measurements

    NASA Astrophysics Data System (ADS)

    Maxwell, S. E.; Douglass, K.; Plusquellic, D.; Whetstone, J. R.

    2013-12-01

    Our objective is to develop accurate and reliable methods for quantifying distributed carbon sources and sinks to support both mitigation efforts and climate change research. We will describe progress toward a field-deployable, eye-safe differential absorption LIDAR system. The current version of our system utilizes a high repetition rate (>200 kHz), 200 ns pulsed fiber amplifier driven by tunable DFB lasers around 1602 nm. Collection is performed using a small (3' diameter) telescope and an avalanche photodiode. We demonstrate a rapid hard target measurement of ambient levels of CO2 in our 100m test facility using low powers from the fiber laser and a highly-retro-reflecting target. We also discuss progress toward a range resolved measurement in the test facility, planned upgrades to the facility, and the development of a low-backscatter beam dump for range-limited applications.

  4. Error reduction in retrievals of atmospheric species from symmetrically measured lidar sounding absorption spectra.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2014-10-20

    We report new methods for retrieving atmospheric constituents from symmetrically-measured lidar-sounding absorption spectra. The forward model accounts for laser line-center frequency noise and broadened line-shape, and is essentially linearized by linking estimated optical-depths to the mixing ratios. Errors from the spectral distortion and laser frequency drift are substantially reduced by averaging optical-depths at each pair of symmetric wavelength channels. Retrieval errors from measurement noise and model bias are analyzed parametrically and numerically for multiple atmospheric layers, to provide deeper insight. Errors from surface height and reflectance variations are reduced to tolerable levels by "averaging before log" with pulse-by-pulse ranging knowledge incorporated.

  5. Differential absorption lidar for volcanic CO(2) sensing tested in an unstable atmosphere.

    PubMed

    Queisser, Manuel; Burton, Mike; Fiorani, Luca

    2015-03-01

    Motivated by the need for an extremely durable and portable instrument to quantify volcanic CO(2) we have produced a corresponding differential absorption lidar (DIAL). It was tested on a volcano (Vulcano, Italy), sensing a non-uniform volcanic CO(2) signal under turbulent atmospheric conditions. The measured CO(2) mixing ratio trend agrees qualitatively well but quantitatively poorly with a reference CO(2) measurement. The disagreement is not in line with the precision of the DIAL determined under conditions that largely exclude atmospheric effects. We show evidence that the disagreement is mainly due to atmospheric turbulence. We conclude that excluding noise associated with atmospheric turbulence, as commonly done in precision analysis of DIAL instruments, may largely underestimate the error of measured CO(2) concentrations in turbulent atmospheric conditions. Implications for volcanic CO(2) sensing with DIAL are outlined.

  6. Differential absorption lidar for volcanic CO(2) sensing tested in an unstable atmosphere.

    PubMed

    Queisser, Manuel; Burton, Mike; Fiorani, Luca

    2015-03-01

    Motivated by the need for an extremely durable and portable instrument to quantify volcanic CO(2) we have produced a corresponding differential absorption lidar (DIAL). It was tested on a volcano (Vulcano, Italy), sensing a non-uniform volcanic CO(2) signal under turbulent atmospheric conditions. The measured CO(2) mixing ratio trend agrees qualitatively well but quantitatively poorly with a reference CO(2) measurement. The disagreement is not in line with the precision of the DIAL determined under conditions that largely exclude atmospheric effects. We show evidence that the disagreement is mainly due to atmospheric turbulence. We conclude that excluding noise associated with atmospheric turbulence, as commonly done in precision analysis of DIAL instruments, may largely underestimate the error of measured CO(2) concentrations in turbulent atmospheric conditions. Implications for volcanic CO(2) sensing with DIAL are outlined. PMID:25836880

  7. Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

    2013-01-01

    Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

  8. Predictions of silicon avalanche photodiode detector performance in water vapor differential absorption lidar

    NASA Technical Reports Server (NTRS)

    Kenimer, R. L.

    1988-01-01

    Performance analyses are presented which establish that over most of the range of signals expected for a down-looking differential absorption lidar (DIAL) operated at 16 km the silicon avalanche photodiode (APD) is the preferred detector for DIAL measurements of atmospheric water vapor in the 730 nm spectral region. The higher quantum efficiency of the APD's, (0.8-0.9) compared to a photomultiplier's (0.04-0.18) more than offsets the higher noise of an APD receiver. In addition to offering lower noise and hence lower random error the APD's excellent linearity and impulse recovery minimize DIAL systematic errors attributable to the detector. Estimates of the effect of detector system parameters on overall random and systematic DIAL errors are presented, and performance predictions are supported by laboratory characterization data for an APD receiver system.

  9. Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

    NASA Technical Reports Server (NTRS)

    Browell, Edward V.; Ismail, Syed; Grossmann, Benoist E.

    1991-01-01

    Recently measured properties of water vapor (H2O) absorption lines have been used in calculations to evalute the temperature sensitivity of differential absorption lidar (Dial) H2O measurements. This paper estimates the temperature sensitivity of H2O lines in the 717-733-nm region for both H2O mixing ratio and number density measurements, and discusses the influence of the H2O line ground state energies E-double-prime, the H2O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for 67 H2O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E-double-prime values in the 100-300/cm range were found to be optimum for Dial measurements of H2O number densities, while E-double-prime values in the 250-500/cm range were found to be optimum for H2O mixing ratio measurements.

  10. Development and testing of a frequency-agile optical parametric oscillator system for differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Weibring, P.; Smith, J. N.; Edner, H.; Svanberg, S.

    2003-10-01

    An all-solid-state fast-tuning lidar transmitter for range- and temporally resolved atmospheric gas concentration measurements has been developed and thoroughly tested. The instrument is based on a commercial optical parametric oscillator (OPO) laser system, which has been redesigned with piezoelectric transducers mounted on the wavelength-tuning mirror and on the crystal angle tuning element in the OPO. Piezoelectric transducers similarly control a frequency-mixing stage and doubling stage, which have been incorporated to extend system capabilities to the mid-IR and UV regions. The construction allows the system to be tuned to any wavelength, in any order, in the range of the piezoelectric transducers on a shot-to-shot basis. This extends the measurement capabilities far beyond the two-wavelength differential absorption lidar method and enables simultaneous measurements of several gases. The system performance in terms of wavelength, linewidth, and power stability is monitored in real time by an étalon-based wave meter and gas cells. The tests showed that the system was able to produce radiation in the 220-4300-nm-wavelength region, with an average linewidth better than 0.2 cm-1 and a shot-to-shot tunability up to 160 cm-1 within 20 ms. The utility of real-time linewidth and wavelength measurements is demonstrated by the ability to identify occasional poor quality laser shots and disregard these measurements. Also, absorption cell measurements of methane and mercury demonstrate the performance in obtaining stable wavelength and linewidth during rapid scans in the mid-IR and UV regions.

  11. Atmospheric absorption versus deep ultraviolet (pre-)resonance in Raman lidar measurements

    NASA Astrophysics Data System (ADS)

    Hallen, Hans D.; Willitsford, Adam H.; Neely, Ryan R.; Chadwick, C. Todd; Philbrick, C. Russell

    2016-05-01

    The Raman scattering of several liquids and solid materials has been investigated near the deep ultraviolet absorption features corresponding to the electron energy states of the chemical species present. It is found to provide significant enhancement, but is always accompanied by absorption due to that or other species along the path. We investigate this trade-off for water vapor, although the results for liquid water and ice will be quantitatively very similar. An optical parametric oscillator (OPO) was pumped by the third harmonic of a Nd:YAG laser, and the output frequency doubled to generate a tunable excitation beam in the 215-600 nm range. We use the tunable laser excitation beam to investigate pre-resonance and resonance Raman spectroscopy near an absorption band of ice. A significant enhancement in the Raman signal was observed. The A-term of the Raman scattering tensor, which describes the pre-resonant enhancement of the spectra, is also used to find the primary observed intensities as a function of incident beam energy, although a wide resonance structure near the final-state-effect related absorption in ice is also found. The results suggest that use of pre-resonant or resonant Raman LIDAR could increase the sensitivity to improve spatial and temporal resolution of atmospheric water vapor measurements. However, these shorter wavelengths also exhibit higher ozone absorption. These opposing effects are modeled using MODTRAN for several configurations relevant for studies of boundary layer water and in the vicinity of clouds. Such data could be used in studies of the measurement of energy flow at the water-air and cloud-air interface, and may help with understanding some of the major uncertainties in current global climate models.

  12. Novel absorption detection techniques for capillary electrophoresis

    SciTech Connect

    Xue, Y.

    1994-07-27

    Capillary electrophoresis (CE) has emerged as one of the most versatile separation methods. However, efficient separation is not sufficient unless coupled to adequate detection. The narrow inner diameter (I.D.) of the capillary column raises a big challenge to detection methods. For UV-vis absorption detection, the concentration sensitivity is only at the {mu}M level. Most commercial CE instruments are equipped with incoherent UV-vis lamps. Low-brightness, instability and inefficient coupling of the light source with the capillary limit the further improvement of UV-vis absorption detection in CE. The goals of this research have been to show the utility of laser-based absorption detection. The approaches involve: on-column double-beam laser absorption detection and its application to the detection of small ions and proteins, and absorption detection with the bubble-shaped flow cell.

  13. Application of the lamp mapping technique for overlap function for Raman lidar systems.

    PubMed

    Walker, Monique; Venable, Demetrius; Whiteman, David N; Sakai, Tetsu

    2016-04-01

    Traditionally, the lidar water vapor mixing ratio (WVMR) is corrected for overlap using data from another instrument, such as a radiosonde. Here we introduce a new experimental method to determine the overlap function using the lamp mapping technique (LMT), which relies on the lidar optics and detection system. The LMT discussed here involves a standard halogen lamp being scanned over the aperture of a Raman lidar telescope in synchronization with the lidar detection system [Appl. Opt.50, 4622 (2011)APOPAI0003-693510.1364/AO.50.004622, Appl. Opt.53, 8538 (2014)APOPAI0003-693510.1364/AO.53.008535]. In this paper, we show results for a LMT-determined overlap function for individual channels, as well as a WVMR overlap function. We found that the LMT-determined WVMR overlap functions deviate within 5% of the traditional radiosonde-determined overlap. PMID:27139656

  14. Application of the lamp mapping technique for overlap function for Raman lidar systems.

    PubMed

    Walker, Monique; Venable, Demetrius; Whiteman, David N; Sakai, Tetsu

    2016-04-01

    Traditionally, the lidar water vapor mixing ratio (WVMR) is corrected for overlap using data from another instrument, such as a radiosonde. Here we introduce a new experimental method to determine the overlap function using the lamp mapping technique (LMT), which relies on the lidar optics and detection system. The LMT discussed here involves a standard halogen lamp being scanned over the aperture of a Raman lidar telescope in synchronization with the lidar detection system [Appl. Opt.50, 4622 (2011)APOPAI0003-693510.1364/AO.50.004622, Appl. Opt.53, 8538 (2014)APOPAI0003-693510.1364/AO.53.008535]. In this paper, we show results for a LMT-determined overlap function for individual channels, as well as a WVMR overlap function. We found that the LMT-determined WVMR overlap functions deviate within 5% of the traditional radiosonde-determined overlap.

  15. New Results from Frequency and Energy Reference Measurements during the first Test Flight with the Airborne Integrated Path Differential Absorption Lidar System CHARM-F

    NASA Astrophysics Data System (ADS)

    Ehret, G.; Fix, A.; Amediek, A.; Quatrevalet, M.

    2015-12-01

    The Integrated Path Differential Absorption Lidar (IPDA) technique is regarded as a suitable means for the measurement of methane and carbon dioxide columns from satellite or aircraft platforms with unprecedented accuracy. Currently, the German-French methane mission MERLIN (Methan Remote Lidar Mission) is prepared. At the same time CHARM-F, an aircraft installed system has been developed at DLR as an airborne demonstrator for a spaceborne greenhouse gas mission. Both use e.g. optical parametric oscillators (OPOs) in a double-pulse mode as the transmitter. Of particular importance for both instruments are the sub-modules required for the frequency stabilization of the transmitter wavelength and, since the IPDA technique, in contrast to DIAL, requires the exact knowledge of the energy ratio of outgoing on-line. The coherence of the lidar transmitter gives rise to speckle effects which have to be considered for the monitoring of the energy ratio of outgoing on- and off-line pulses. For the frequency reference of CHARM-F, a very successful stabilization scheme has been developed which will also serve as the reference for MERLIN. In Spring 2015, CHARM-F was flown aboard the German HALO aircraft for the first time which enables a detailed view on the performance of both the energy calibration and frequency reference subsystems under real flight conditions. As an initial quality check we will compared the airborne results to previous lab measurements which have been performed under stable environmental conditions.

  16. A New Differential Absorption Lidar to Measure Sub-Hourly Fluctuation of Tropospheric Ozone Profiles in the Baltimore - Washington D.C. Region

    NASA Technical Reports Server (NTRS)

    Sullivan, J. T.; McGee, T. J.; Sumnicht, G. K.; Twigg, L. W.; Hoff, R. M.

    2014-01-01

    Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99 N, 76.84 W, 57 meters ASL) from 400 m to 12 km AGL. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19 percent from 0-1.5 km, 10-18 percent from 1.5-3 km, and 11-25 percent from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore

  17. A new differential absorption lidar to measure sub-hourly fluctuation of tropospheric ozone profiles in the Baltimore-Washington DC region

    NASA Astrophysics Data System (ADS)

    Sullivan, J. T.; McGee, T. J.; Sumnicht, G. K.; Twigg, L. W.; Hoff, R. M.

    2014-04-01

    Tropospheric ozone profiles have been retrieved from the new ground based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99° N, 76.84° W, 57 m a.s.l.) from 400 m to 12 km a.g.l. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the Differential Absorption Lidar (DIAL) technique, which currently detects two wavelengths, 289 and 299 nm. Ozone is absorbed more strongly at 289 nm than at 299 nm. The DIAL technique exploits this difference between the returned backscatter signals to obtain the ozone number density as a function of altitude. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high pressure hydrogen and deuterium. Stimulated Raman Scattering (SRS) within the focus generates a significant fraction of the pump energy at the first Stokes shift. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range resolved number density can be derived. An interesting atmospheric case study involving the Stratospheric-Tropospheric Exchange (STE) of ozone is shown to emphasize the regional importance of this instrument as well as assessing the validation and calibration of data. The retrieval yields an uncertainty of 16-19% from 0-1.5 km, 10-18% from 1.5-3 km, and 11-25% from 3 km to 12 km. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington DC area.

  18. Micropulse differential absorption lidar for identification of carbon sequestration site leakage.

    PubMed

    Johnson, William; Repasky, Kevin S; Carlsten, John L

    2013-05-01

    A scanning differential absorption lidar (DIAL) instrument for identification of carbon dioxide leaks at carbon sequestration sites has been developed and initial data has been collected at Montana State University. The laser transmitter uses two tunable discrete mode laser diodes operating in the continuous-wave mode with one locked to the online absorption wavelength and the other operating at the offline wavelength. Two in-line fiber optic switches are used to switch between online and offline operation. After the fiber optic switch, an acousto-optic modulator is used to generate a pulse train used to injection seed an erbium-doped fiber amplifier to produce eye-safe laser pulses with maximum pulse energies of 66 μJ, a pulse repetition frequency of 15 kHz, and an operating wavelength of 1.571 μm. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a photomultiplier tube module operating in the photon counting mode. The DIAL has measured carbon dioxide profiles from 1 to 2.5 km with 60 min temporal averaging. Comparisons of DIAL measurements with a Licor LI-820 gas analyzer point sensor have been made.

  19. High-resolution atmospheric water vapor measurements with a scanning differential absorption lidar

    NASA Astrophysics Data System (ADS)

    Späth, F.; Behrendt, A.; Muppa, S. K.; Metzendorf, S.; Riede, A.; Wulfmeyer, V.

    2014-11-01

    The scanning differential absorption lidar (DIAL) of the University of Hohenheim (UHOH) is presented. The UHOH DIAL is equipped with an injection-seeded frequency-stabilized high-power Ti:sapphire laser operated at 818 nm with a repetition rate of 250 Hz. A scanning transceiver unit with a 80 cm primary mirror receives the atmospheric backscatter signals. The system is capable of water vapor measurements with temporal resolutions of a few seconds and a range resolution between 30 and 300 m at daytime. It allows to investigate surface-vegetation-atmosphere exchange processes with high resolution. In this paper, we present the design of the instrument and illustrate its performance with recent water vapor measurements taken in Stuttgart-Hohenheim and in the frame of the HD(CP)2 Observational Prototype Experiment (HOPE). HOPE was located near research center Jülich, in western Germany, in spring 2013 as part of the project "High Definition of Clouds and Precipitation for advancing Climate Prediction" (HD(CP)2). Scanning measurements reveal the 3-dimensional structures of the water vapor field. The influence of uncertainties within the calculation of the absorption cross-section at wavelengths around 818 nm for the WV retrieval is discussed. Radiosonde intercomparisons show a very small bias between the instruments of only (-0.04 ± 0.11) g m-3 or (-1.0 ± 2.3) % in the height range of 0.5 to 3 km.

  20. Micropulse differential absorption lidar for identification of carbon sequestration site leakage.

    PubMed

    Johnson, William; Repasky, Kevin S; Carlsten, John L

    2013-05-01

    A scanning differential absorption lidar (DIAL) instrument for identification of carbon dioxide leaks at carbon sequestration sites has been developed and initial data has been collected at Montana State University. The laser transmitter uses two tunable discrete mode laser diodes operating in the continuous-wave mode with one locked to the online absorption wavelength and the other operating at the offline wavelength. Two in-line fiber optic switches are used to switch between online and offline operation. After the fiber optic switch, an acousto-optic modulator is used to generate a pulse train used to injection seed an erbium-doped fiber amplifier to produce eye-safe laser pulses with maximum pulse energies of 66 μJ, a pulse repetition frequency of 15 kHz, and an operating wavelength of 1.571 μm. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a photomultiplier tube module operating in the photon counting mode. The DIAL has measured carbon dioxide profiles from 1 to 2.5 km with 60 min temporal averaging. Comparisons of DIAL measurements with a Licor LI-820 gas analyzer point sensor have been made. PMID:23669765

  1. Agricultural pest monitoring using fluorescence lidar techniques. Feasibility study

    NASA Astrophysics Data System (ADS)

    Mei, L.; Guan, Z. G.; Zhou, H. J.; Lv, J.; Zhu, Z. R.; Cheng, J. A.; Chen, F. J.; Löfstedt, C.; Svanberg, S.; Somesfalean, G.

    2012-03-01

    The fluorescence of different types of planthopper ( Hemiptera) and moth ( Lepidoptera), which constitute important Chinese agricultural pests, was investigated both in situ in a laboratory setting and remotely using a fluorescence light detection and ranging (lidar) system operating at a range of about 50 m. The natural autofluorescence of different species, as well as the fluorescence from insects that had been dusted with fluorescent dye powder for identification were studied. Autofluorescence spectra of both moths and planthoppers show a maximum intensity peak around 450 nm. Bleaching upon long-time laser illumination was modest and did not affect the shape of the spectrum. A single dyed rice planthopper, a few mm in size, could be detected at 50 m distance by using the fluorescence lidar system. By employing various marking dyes, different types of agricultural pest could be determined. We suggest that lidar may be used in studies of migration and movement of pest insects, including studies of their behavior in the vicinity of pheromone traps and in pheromone-treated fields.

  2. Modeling and comparative study of various detection techniques for FMCW LIDAR using optisystem

    NASA Astrophysics Data System (ADS)

    Elghandour, Ahmed H.; Ren, Chen D.

    2013-09-01

    In this paper we investigated the different detection techniques especially direct detection, coherent heterodyne detection and coherent homodyne detection on FMCW LIDAR system using Optisystem package. A model for target, propagation channel and various detection techniques were developed using Optisystem package and then a comparative study among various detection techniques for FMCW LIDAR systems is done analytically and simulated using the developed model. Performance of direct detection, heterodyne detection and homodyne detection for FMCW LIDAR system was calculated and simulated using Optisystem package. The output simulated performance was checked using simulated results of MATLAB simulator. The results shows that direct detection is sensitive to the intensity of the received electromagnetic signal and has low complexity system advantage over the others detection architectures at the expense of the thermal noise is the dominant noise source and the sensitivity is relatively poor. In addition to much higher detection sensitivity can be achieved using coherent optical mixing which is performed by heterodyne and homodyne detection.

  3. Semi-empirical inversion technique for retrieval of quantitative attenuation profiles with underwater scanning lidar systems

    NASA Astrophysics Data System (ADS)

    Vuorenkoski, Anni K.; Dalgleish, Fraser R.; Twardowski, Michael S.; Ouyang, Bing; Trees, Charles C.

    2015-05-01

    A fine structure underwater imaging LiDAR (FSUIL) has recently been developed and initial field trials have been conducted. The instrument, which rapidly scans an array of closely spaced, narrow, collimated laser pulses into the water column produces two-dimensional arrays of backscatter profiles, with fine spatial and temporal resolution. In this paper a novel method to derive attenuation profiles is introduced. This approach is particularly attractive in applications where primary on-board processing is required, and other applications where conventional model-based approaches are not feasible due to a limited computational capacity or lack of a priori knowledge of model input parameters. The paper also includes design details regarding the new FSUIL instrument are given, with field results taken in clear to moderately turbid water being presented to illustrate the various effects and considerations in the analysis of the system data. LiDAR waveforms and LiDAR derived attenuation coefficients are analyzed and compared to calibrated beam attenuation, particulate scattering and absorption coefficients. The system was field tested during the NATO Ligurian Sea LIDAR & Optical Measurements Experiment (LLOMEx) cruise in March 2013, during the spring bloom conditions. Throughout a wide range of environmental conditions, the FSUIL was deployed on an in situ profiler obtaining thousands of three-dimensional LiDAR scans from the near surface down to the lower thermocline. Deployed concurrent to the FSUIL was a range of commercially available off-the-shelf instruments providing side-by-side in-situ attenuation measurement.

  4. Diode-laser-based water vapor differential absorption lidar (DIAL) profiler evaluation

    NASA Astrophysics Data System (ADS)

    Spuler, S.; Weckwerth, T.; Repasky, K. S.; Nehrir, A. R.; Carbone, R.

    2012-12-01

    We are in the process of evaluating the performance of an eye-safe, low-cost, diode-laser-based, water vapor differential absorption lidar (DIAL) profiler. This class of instrument may be capable of providing continuous water vapor and aerosol backscatter profiles at high vertical resolution in the atmospheric boundary layer (ABL) for periods of months to years. The technology potentially fills a national long term observing facility gap and could greatly benefit micro- and meso-meteorology, water cycle, carbon cycle and, more generally, biosphere-hydrosphere-atmosphere interaction research at both weather and climate variability time scales. For the evaluation, the Montana State University 3rd generation water vapor DIAL was modified to enable unattended operation for a period of several weeks. The performance of this V3.5 version DIAL was tested at MSU and NCAR in June and July of 2012. Further tests are currently in progress with Howard University at Beltsville, Maryland; and with the National Weather Service and Oklahoma University at Dallas/Fort Worth, Texas. The presentation will include a comparison of DIAL profiles against meteorological "truth" at the aforementioned locations including: radiosondes, Raman lidars, microwave and IR radiometers, AERONET and SUOMINET systems. Instrument reliability, uncertainty, systematic biases, detection height statistics, and environmental complications will be evaluated. Performance will be judged in the context of diverse scientific applications that range from operational weather prediction and seasonal climate variability, to more demanding climate system process studies at the land-canopy-ABL interface. Estimating the extent to which such research and operational applications can be satisfied with a low cost autonomous network of similar instruments is our principal objective.

  5. Evaluation of tropospheric water vapor profiling using eye-safe, infrared differential absorption lidar

    SciTech Connect

    Rye, B.J. |; Machol, J.L.; Grund, C.J.; Hardesty, R.M.

    1996-05-14

    Continuous, high quality profiles of water vapor, free of systematic bias, and of moderate temporal and spatial resolution are fundamental to the success of the ARM CART program. In addition, these should be acquired over long periods at low operational and maintenance cost. The development and verification of realistic climate model parameterizations for clouds and net radiation balance, and the correction of other CART site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. To date, application of profiles have been limited by vertical resolution and uniqueness and high operating cost, or diminished daytime performance, lack of eye-safety, and high maintenance cost. Recent developments in infrared laser and detector technology make possible compact IR differential absorption lidar (DIAL) systems at eye-safe wavelengths. In the studies reported here, we develop DIAL system performance models and examine the potential of solving some of the shortcomings of previous methods using parameters representative of current technologies. These simulations are also applied to determine the strengths and weaknesses unique to the DIAL method for this application.

  6. Profiling tropospheric water vapour with a coherent infrared differential absorption lidar: a sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Baron, Philippe; Ishii, Shoken; Mizutani, Kohei; Itabe, Toshikazu; Yasui, Motoaki

    2012-11-01

    In the last decade the precision of coherent Doppler differential absorption lidar (DIAL) has been greatly improved in near and middle infra-red domains for measuring greenhouse gases such as CO2, CH4 and winds. The National Institute of Information and Communications Technology (NICT, Japan) has developed and is operating a CO2 and wind measuring ground-based coherent DIAL at 2.05 μm (4878 cm-1). The application of this technology from space is now considered. In this analysis we study the use of the NICT DIAL for profiling tropospheric water vapour from space. We present the methodology to select the spectral lines and summarized the results of the selected lines between 4000 and 7000 cm-1. The choice of the frequency offset, the pulse energy and repetition frequency are discussed. Retrieval simulations from the line at 4580 cm-1 (2.18 μm) suitable for the boundary layer and the stronger one at 5621 cm-1 (1.78 μm) for sounding the boundary layer and the middle troposphere, are shown.

  7. Field-deployable diode-laser-based differential absorption lidar (DIAL) for profiling water vapor

    NASA Astrophysics Data System (ADS)

    Spuler, S. M.; Repasky, K. S.; Morley, B.; Moen, D.; Hayman, M.; Nehrir, A. R.

    2015-03-01

    A field-deployable water vapor profiling instrument that builds on the foundation of the preceding generations of diode-laser-based differential absorption lidar (DIAL) laboratory prototypes was constructed and tested. Significant advances are discussed, including a unique shared telescope design that allows expansion of the outgoing beam for eye-safe operation with optomechanical and thermal stability; multistage optical filtering enabling measurement during daytime bright-cloud conditions; rapid spectral switching between the online and offline wavelengths enabling measurements during changing atmospheric conditions; and enhanced performance at lower ranges by the introduction of a new filter design and the addition of a wide field-of-view channel. Performance modeling, testing, and intercomparisons are performed and discussed. In general, the instrument has a 150 m range resolution with a 10 min temporal resolution; 1 min temporal resolution in the lowest 2 km of the atmosphere is demonstrated. The instrument is shown capable of autonomous long-term field operation - 50 days with a > 95% uptime - under a broad set of atmospheric conditions and potentially forms the basis for a ground-based network of eye-safe autonomous instruments needed for the atmospheric sciences research and forecasting communities.

  8. A Water Vapor Differential Absorption LIDAR Design for Unpiloted Aerial Vehicles

    NASA Technical Reports Server (NTRS)

    DeYoung, Russell J.; Mead, Patricia F.

    2004-01-01

    This system study proposes the deployment of a water vapor Differential Absorption LIDAR (DIAL) system on an Altair unmanned aerial vehicle (UAV) platform. The Altair offers improved payload weight and volume performance, and longer total flight time as compared to other commercial UAV's. This study has generated a preliminary design for an Altair based water vapor DIAL system. The design includes a proposed DIAL schematic, a review of mechanical challenges such as temperature and humidity stresses on UAV deployed DIAL systems, an assessment of the available capacity for additional instrumentation (based on the proposed design), and an overview of possible weight and volume improvements associated with the use of customized electronic and computer hardware, and through the integration of advanced fiber-optic and laser products. The results of the study show that less than 17% of the available weight, less than 19% of the volume capacity, and approximately 11% of the electrical capacity is utilized by the proposed water vapor DIAL system on the Altair UAV.

  9. Atmospheric Backscatter Profiles at 1572nm from Pulsed Lidar Measurments of CO2 Column Absorption from the 2011 ASCENDS Flight Campaign

    NASA Astrophysics Data System (ADS)

    Allan, G. R.; Riris, H.; Hasselbrack, W.; Sun, X.; Ramanathan, A.; Mao, J.; Abshire, J. B.

    2012-12-01

    We present height-resolved backscatter profiles from the NASA Goddard Space Flight Center's CO2 sounder lidar, rich in detail, which shows clear evidence of multiple backscatter layers, clouds, and aerosols allowing for the identification of the Planetary Boundary Layer (PBL). This data is recorded as a consequence of our pulsed lidar measurements of the CO2 column absorption. The CO2 Sounder is a pulsed lidar for active remote measurements of CO2 abundance from an airborne platform and is one candidate for the lidar on the NASA ASCENDS mission. The lidar uses a scanning, pulsed laser and fiber amplifier in a Master Oscillator Power Amplifier (MOPA) configuration to measure CO2 absorption at 1572.335 nm, lineshape, range to scattering surface and backscatter profiles. The laser is scanned across the absorption feature measuring at 30 discrete wavelengths/scan and ~300 scans/sec. The time-resolved return signal, with a temporal resolution of 8ns, is detected by a photon-counting PMT fiber coupled to a modified commercial, 2m focal length f10 Schmidt-Cassegrain telescope. The column density for CO2 is estimated from the differential optical depth (DOD) of the scanned absorption line using an integrated-path differential absorption (IPDA) technique and the optical path from the time of flight. A backscatter profile of the measured column is recorded for every pulse of every scan and integrated for 1 second. The backscatter profiles we will show are determined from the receivers photon counting record using a cross-correaltion technique (sliding inner product) with a vertical resolution of better than 300m, set by the 1μs pulse width from the MOPA. The range to the surface can be determined to a few meters. Major benefits of a pulsed technique using time-resolved detection to measure lineshape, is the unambiguous detection of the ground return, intervening clouds, aerosols and information on the vertical distribution of CO2. This technique can uniquely identify the

  10. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  11. Self-calibration and laser energy monitor validations for a double-pulsed 2-μm CO2 integrated path differential absorption lidar application.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Petros, Mulugeta; Remus, Ruben; Yu, Jirong

    2015-08-20

    Double-pulsed 2-μm integrated path differential absorption (IPDA) lidar is well suited for atmospheric CO2 remote sensing. The IPDA lidar technique relies on wavelength differentiation between strong and weak absorbing features of the gas normalized to the transmitted energy. In the double-pulse case, each shot of the transmitter produces two successive laser pulses separated by a short interval. Calibration of the transmitted pulse energies is required for accurate CO2 measurement. Design and calibration of a 2-μm double-pulse laser energy monitor is presented. The design is based on an InGaAs pin quantum detector. A high-speed photoelectromagnetic quantum detector was used for laser-pulse profile verification. Both quantum detectors were calibrated using a reference pyroelectric thermal detector. Calibration included comparing the three detection technologies in the single-pulsed mode, then comparing the quantum detectors in the double-pulsed mode. In addition, a self-calibration feature of the 2-μm IPDA lidar is presented. This feature allows one to monitor the transmitted laser energy, through residual scattering, with a single detection channel. This reduces the CO2 measurement uncertainty. IPDA lidar ground validation for CO2 measurement is presented for both calibrated energy monitor and self-calibration options. The calibrated energy monitor resulted in a lower CO2 measurement bias, while self-calibration resulted in a better CO2 temporal profiling when compared to the in situ sensor.

  12. Optical parametric oscillators in lidar sounding of trace atmospheric gases in the mid infrared region

    NASA Astrophysics Data System (ADS)

    Romanovskii, O. A.; Sadovnikov, S. A.; Kharchenko, O. V.; Shumskii, V. K.; Yakovlev, S. V.

    2015-12-01

    Applicability of a KTA crystal-based laser system with optical parametric generation to lidar sounding of the atmosphere in the spectral range 3-4 μm is studied in this work. A technique developed for lidar sounding of trace atmospheric gases is based on differential absorption (DIAL) technique and differential optical absorption spectroscopy (DOAS). The DIAL-DOAS technique is tested to estimate its efficiency for lidar sounding of atmospheric trace gases.

  13. Technique for Obtaining Vertical Profiles of Backscattering and Extinction Cross Sections Using Slant Path Lidar Measurements

    NASA Technical Reports Server (NTRS)

    Spinhirne, J. D.; Herman, B. M.

    1973-01-01

    A method is presented for solving for vertical profiles of atmospheric particulate extinction and backscattering cross-sections utilizing monostatic lidar slant path measurements. The method is an extension of work by Fernald. It is shown that the number of assumptions necessary for an iterative solution of extinction and backscattering cross sections can be reduced if lidar slant path measurements are used to solve directly for optical depths. The technique is useful only if sufficiently accurate lidar measurements are available. With highly accurate measurements it is also possible to solve directly for extinction cross sections without an iterative solution of a transcendental equation if the proper reduction scheme is used. The required accuracy is discussed and results showing the effect of errors are presented.

  14. Doppler Lidar Measurements of Tropospheric Wind Profiles Using the Aerosol Double Edge Technique

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Li, Steven X.; Mathur, Savyasachee; Korb, C. Laurence; Chen, Huailin

    2000-01-01

    The development of a ground based direct detection Doppler lidar based on the recently described aerosol double edge technique is reported. A pulsed, injection seeded Nd:YAG laser operating at 1064 nm is used to make range resolved measurements of atmospheric winds in the free troposphere. The wind measurements are determined by measuring the Doppler shift of the laser signal backscattered from atmospheric aerosols. The lidar instrument and double edge method are described and initial tropospheric wind profile measurements are presented. Wind profiles are reported for both day and night operation. The measurements extend to altitudes as high as 14 km and are compared to rawinsonde wind profile data from Dulles airport in Virginia. Vertical resolution of the lidar measurements is 330 m and the rms precision of the measurements is a low as 0.6 m/s.

  15. Differential absorption radar techniques: water vapor retrievals

    NASA Astrophysics Data System (ADS)

    Millán, Luis; Lebsock, Matthew; Livesey, Nathaniel; Tanelli, Simone

    2016-06-01

    Two radar pulses sent at different frequencies near the 183 GHz water vapor line can be used to determine total column water vapor and water vapor profiles (within clouds or precipitation) exploiting the differential absorption on and off the line. We assess these water vapor measurements by applying a radar instrument simulator to CloudSat pixels and then running end-to-end retrieval simulations. These end-to-end retrievals enable us to fully characterize not only the expected precision but also their potential biases, allowing us to select radar tones that maximize the water vapor signal minimizing potential errors due to spectral variations in the target extinction properties. A hypothetical CloudSat-like instrument with 500 m by ˜ 1 km vertical and horizontal resolution and a minimum detectable signal and radar precision of -30 and 0.16 dBZ, respectively, can estimate total column water vapor with an expected precision of around 0.03 cm, with potential biases smaller than 0.26 cm most of the time, even under rainy conditions. The expected precision for water vapor profiles was found to be around 89 % on average, with potential biases smaller than 77 % most of the time when the profile is being retrieved close to surface but smaller than 38 % above 3 km. By using either horizontal or vertical averaging, the precision will improve vastly, with the measurements still retaining a considerably high vertical and/or horizontal resolution.

  16. Pulsed Lidar Measurements of Atmospheric CO2 Column Absorption in the ASCENDS 2011 Airborne Campaign: Measurement Analysis

    NASA Astrophysics Data System (ADS)

    Ramanathan, A.; Mao, J.; Allan, G. R.; Weaver, C. J.; Hasselbrack, W.; Riris, H.; Sun, X.; Abshire, J. B.

    2012-12-01

    Trace gas LIDAR has the potential to actively sense greenhouse gas concentrations in the earth's atmosphere continuously without being affected by day or night. This will enable identifying greenhouse gas sources and sinks, which will help better predict future atmospheric trends of these gases. However, in order to ensure reliable and accurate measurements, it is important to establish metrics to quantify performance. As part of the ASCENDS (Active Sensing of Co2 over Nights, Days and Seasons) program, we conducted an airborne campaign of our CO2 pulsed LIDAR system in August 2011, flying over a variety of terrain and conditions, including snow, ocean, clouds, desert and mountains. Our instrument uses an IPDA (Integrated Path Differential Absorption) approach probing 30 wavelengths across a 1572 nm CO2 absorption line. Our multi-wavelength approach provides redundancy for evaluating the stability of the instrument, and also allows us to perform spectroscopic analysis of the atmosphere. Here, we present our detailed analysis and results. Tracking long-term stability of our instrument by using the Allan deviation formalism for wavelengths away from the absorption line-center, we find that the measured pulse energy (normalized to eliminate ground reflectivity) is stable down to 0.2% across varying terrain, surface reflectivity, flight altitude and LIDAR range. Comparing our measured CO2 absorption line-shape (at regions of constant, known CO2 concentrations) with the predicted line-shape based on the LIDAR range, flight altitude and relevant atmosphere parameters (based on in situ measurements by instruments aboard the aircraft), we find the agreement to be better than 1% (RMS error), once we average 50 s to eliminate shot noise. Our multi-wavelength approach also allows us to track the position of the line-center. The altitude dependence of the atmospheric pressure causes a shift in the CO2 absorption as a function of aircraft altitude. Our measured pressure shift

  17. In vivo gallbladder absorption: a new dual-isotope technique

    SciTech Connect

    Conter, R.L.; Porter-Fink, V.; Denbesten, L.; Roslyn, J.J.

    1986-10-01

    Available methods for measuring in vivo gallbladder absorption preclude the use of animals in which hepatic bile enters the gallbladder via accessory or aberrant channels. However, accessory bile ducts are present in many of the animal models currently used in gallstone research. The aim of this study, therefore, was to evaluate a new dual-isotope technique that corrects for accessory bile flow and to compare data on electrolyte and water absorption with those derived from the standard, single-isotope technique. Prairie dogs underwent gallbladder exclusion by cystic duct ligation and common bile duct cannulation. Carbon 14-polyethylene glycol-labeled lactated Ringer's solution was instilled into the gallbladder while tritiated cholic acid was administered intravenously to label the bile acid pool. There is no correlation between water or electrolyte absorption and time, nor between water and electrolyte absorption, when these parameters are calculated by the standard, single-isotope technique. In contrast, use of the dual-isotope technique quantifies accessory bile duct flow and yields a linear increase in water and electrolyte absorption, both of which are time dependent. These data suggest that the dual-isotope technique provides a means to accurately measure in vivo gallbladder absorption in animals with or without accessory bile ducts.

  18. Innovative High-Accuracy Lidar Bathymetric Technique for the Frequent Measurement of River Systems

    NASA Astrophysics Data System (ADS)

    Gisler, A.; Crowley, G.; Thayer, J. P.; Thompson, G. S.; Barton-Grimley, R. A.

    2015-12-01

    Lidar (light detection and ranging) provides absolute depth and topographic mapping capability compared to other remote sensing methods, which is useful for mapping rapidly changing environments such as riverine systems. Effectiveness of current lidar bathymetric systems is limited by the difficulty in unambiguously identifying backscattered lidar signals from the water surface versus the bottom, limiting their depth resolution to 0.3-0.5 m. Additionally these are large, bulky systems that are constrained to expensive aircraft-mounted platforms and use waveform-processing techniques requiring substantial computation time. These restrictions are prohibitive for many potential users. A novel lidar device has been developed that allows for non-contact measurements of water depth down to 1 cm with an accuracy and precision of < 1 cm by exploiting the polarization properties of the light-surface interaction. This system can transition seamlessly from ranging over land to shallow to deep water allowing for shoreline charting, measuring water volume, mapping bottom topology, and identifying submerged objects. The scalability of the technique opens up the ability for handheld or UAS-mounted lidar bathymetric systems, which provides for potential applications currently unavailable to the community. The high laser pulse repetition rate allows for very fine horizontal resolution while the photon-counting technique permits real-time depth measurement and object detection. The enhanced measurement capability, portability, scalability, and relatively low-cost creates the opportunity to perform frequent high-accuracy monitoring and measuring of aquatic environments which is crucial for understanding how rivers evolve over many timescales. Results from recent campaigns measuring water depth in flowing creeks and murky ponds will be presented which demonstrate that the method is not limited by rough water surfaces and can map underwater topology through moderately turbid water.

  19. Application of image classification techniques to multispectral lidar point cloud data

    NASA Astrophysics Data System (ADS)

    Miller, Chad I.; Thomas, Judson J.; Kim, Angela M.; Metcalf, Jeremy P.; Olsen, Richard C.

    2016-05-01

    Data from Optech Titan are analyzed here for purposes of terrain classification, adding the spectral data component to the lidar point cloud analysis. Nearest-neighbor sorting techniques are used to create the merged point cloud from the three channels. The merged point cloud is analyzed using spectral analysis techniques that allow for the exploitation of color, derived spectral products (pseudo-NDVI), as well as lidar features such as height values, and return number. Standard spectral image classification techniques are used to train a classifier, and analysis was done with a Maximum Likelihood supervised classification. Terrain classification results show an overall accuracy improvement of 10% and a kappa coefficient increase of 0.07 over a raster-based approach.

  20. Tone-burst technique measures high-intensity sound absorption

    NASA Technical Reports Server (NTRS)

    Powell, J. G.; Van Houten, J. J.

    1971-01-01

    Tone-burst technique, in which narrow-bandwidth, short-duration sonic pulse is propagated down a standing-wave tube, measures sound absorbing capacity of materials used in jet engine noise abatement. Technique eliminates effects of tube losses and yields normal-incidence absorption coefficient of specimen.

  1. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

    2015-01-01

    The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-micron laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-micron integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

  2. Triple-Pulsed Two-Micron Integrated Path Differential Absorption Lidar: A New Active Remote Sensing Capability with Path to Space

    NASA Astrophysics Data System (ADS)

    Singh, Upendra N.; Refaat, Tamer F.; Petros, Mulugeta; Yu, Jirong

    2016-06-01

    The two-micron wavelength is suitable for monitoring atmospheric water vapor and carbon dioxide, the two most dominant greenhouse gases. Recent advances in 2-μm laser technology paved the way for constructing state-of-the-art lidar transmitters for active remote sensing applications. In this paper, a new triple-pulsed 2-μm integrated path differential absorption lidar is presented. This lidar is capable of measuring either two species or single specie with two different weighting functions, simultaneously and independently. Development of this instrument is conducted at NASA Langley Research Center. Instrument scaling for projected future space missions will be discussed.

  3. Raman-lidar technique for tropospheric and stratospheric sensing of aerosol optical and microphysical properties

    SciTech Connect

    Wandinger, U.

    1995-01-01

    Tropospheric and stratospheric aerosols and clouds are known to influence the earth`s radiation budget as well as chemical processes of the atmosphere. Thus, remote sensing of optical and microphysical properties of atmospheric particles has important applications in weather and climate research, pollution monitoring, and atmospheric chemistry. During the last few years Raman lidars have become very important tools in this field of research. The development of powerful light sources such as Nd:YAG and excimer lasers, of interference filters with narrow bandwidth and high transmission, and of low-noise photomultiplier tubes and counting systems has improved the Raman-lidar technique during the past decade significantly. The technique is based on the detection of two signals resulting from elastic backscattering by air molecules and particles and inelastic (Raman) backscattering by a gas of known number density, i.e., nitrogen or oxygen. The technique has been successfully applied to cirrus-cloud studies. In this presentation, the capability of the Raman-lidar technique for tropospheric and stratospheric profiling of aerosol and cloud properties will be discussed on the basis of measurement examples.

  4. Impact of broadened laser line-shape on retrievals of atmospheric species from lidar sounding absorption spectra.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2015-02-01

    We examine the impact of broadened laser line-shape on retrievals of atmospheric species from lidar-sounding absorption spectra. The laser is assumed to be deterministically modulated into a stable, nearly top-hat frequency comb to suppress the stimulated Brillouin scattering, allowing over 10-fold pulse energy increase without adding measurement noise. Our model remains accurate by incorporating the laser line-shape factor into the effective optical depth. Retrieval errors arising from measurement noise and model bias are analyzed parametrically and numerically to provide deeper insight. The stable laser line-shape broadening minimally degrades the column-averaged retrieval, but can significantly degrade the multiple-layer retrievals.

  5. BELINDA: Broadband Emission Lidar with Narrowband Determination of Absorption. A new concept for measuring water vapor and temperature profiles

    NASA Technical Reports Server (NTRS)

    Theopold, F. A.; Weitkamp, C.; Michaelis, W.

    1992-01-01

    We present a new concept for differential absorption lidar measurements of water vapor and temperature profiles. The idea is to use one broadband emission laser and a narrowband filter system for separation of the 'online' and 'offline' return signals. It is shown that BELINDA offers improvements as to laser emission shape and stability requirements, background suppression, and last and most important a significant reduction of the influence of Rayleigh scattering. A suitably designed system based on this concept is presented, capable of measuring water vapor or temperature profiles throughout the planetary boundary layer.

  6. Acousto-optically tuned isotopic CO{sub 2} lasers for long-range differential absorption LIDAR

    SciTech Connect

    Thompson, D.C.; Busch, G.E.; Hewitt, C.J.; Remelius, D.K.; Shimada, Tsutomu; Strauss, C.E.M.; Wilson, C.W.

    1998-12-01

    The authors are developing 2--100 kHz repetition rate CO{sub 2} lasers with milliJoule pulse energies, rapid acousto-optic tuning and isotopic gas mixes, for Differential Absorption LIDAR (DIAL) applications. The authors explain the tuning method, which uses a pair of acousto-optic modulators and is capable of random access to CO{sub 2} laser lines at rates of 100 kHz or more. The laser system is also described, and they report on performance with both normal and isotopic gas mixes.

  7. Development and operation of a real-time data acquisition system for the NASA-LaRC differential absorption lidar

    NASA Technical Reports Server (NTRS)

    Butler, C.

    1985-01-01

    Computer hardware and software of the NASA multipurpose differential absorption lidar (DIAL) sysatem were improved. The NASA DIAL system is undergoing development and experimental deployment for remote measurement of atmospheric trace gas concentration from ground and aircraft platforms. A viable DIAL system was developed with the capability of remotely measuring O3 and H2O concentrations from an aircraft platform. Test flights were successfully performed on board the NASA/Goddard Flight Center Electra aircraft from 1980 to 1984. Improvements on the DIAL data acquisition system (DAS) are described.

  8. Diode-Laser-Based Differential Absorption Lidar (DIAL) for Long Term Autonomous Field Deployment

    NASA Astrophysics Data System (ADS)

    Moen, D.; Repasky, K. S.; Spuler, S.; Nehrir, A. R.

    2015-12-01

    The rapidly changing spatial and temporal distribution of water vapor in the planetary boundary layer influences dynamical and physical processes that drive weather phenomena, general circulation patterns, radiative transfer, and the global water cycle. The ability to measure the water vapor distribution continuously within the lower troposphere has been identified as a high priority measurement capability needed by both the weather forecasting and climate science communities. This presentation provides an update on an economical and compact diode-laser-based differential absorption lidar (DIAL) which has demonstrated the capability of meeting these high priority measurement needs. The DIAL instrument utilizes two continuous wave distributed feedback diode lasers to injection seed a current modulated tapered semiconductor optical amplifier. An improved switching time between the on-line and off-line wavelength, on the order of 16.7 ms, allows the instrument to retrieve water vapor profiles in rapidly changing atmospheric conditions. A shared telescope design based on a 40.64 cm diameter Dobsonian telescope allows the outgoing beam to be eye-safe at the exit of the telescope. The DIAL receiver utilizes the Dobsonian telescope to collect the scattered light and direct it through an optical narrow bandpass filter (NBF) and a Fabry-Perot etalon with a free spectral range of 0.1 nm which is equal to the wavelength difference between the on-line and off-line DIAL wavelengths. A beam splitter directs 90% of the scattered light through a second NBF, and couples it onto a fiber coupled avalanche photodiode (APD), providing a far field measurement. The remaining 10% of the light passing through the beam splitter is incident on a free space coupled APD, providing a wider field of view for water vapor measurements at lower altitudes. The two channel receiver allows water vapor measurement between 500 m and 4 km/6km during daytime/nighttime operation, respectively. The DIAL

  9. Design of Advanced Atmospheric Water Vapor Differential Absorption Lidar (DIAL) Detection System

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Luck, William S., Jr.; DeYoung, Russell J.

    1999-01-01

    The measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The lidar atmospheric sensing experiment (LASE) is an instrument designed and operated by the Langley Research Center for high precision water vapor measurements. The design details of a new water vapor lidar detection system that improves the measurement sensitivity of the LASE instrument by a factor of 10 are discussed. The new system consists of an advanced, very low noise, avalanche photodiode (APD) and a state-of-the-art signal processing circuit. The new low-power system is also compact and lightweight so that it would be suitable for space flight and unpiloted atmospheric vehicles (UAV) applications. The whole system is contained on one small printed circuit board (9 x 15 sq cm). The detection system is mounted at the focal plane of a lidar receiver telescope, and the digital output is read by a personal computer with a digital data acquisition card.

  10. Development and Testing of a Scanning Differential Absorption Lidar For Carbon Sequestration Site Monitoring

    NASA Astrophysics Data System (ADS)

    Soukup, B.; Johnson, W.; Repasky, K. S.; Carlsten, J. L.

    2013-12-01

    A scanning differential absorption lidar (DIAL) instrument for carbon sequestration site monitoring is under development and testing at Montana State University. The laser transmitter uses two tunable discrete mode laser diodes (DMLD) operating in the continuous wave (cw) mode with one locked to the on-line absorption wavelength at 1571.4067 nm and the second operating at the off-line wavelength at 1571.2585 nm. Two in-line fiber optic switches are used to switch between on-line and off-line operation. After the fiber optic switches, an acousto-optic modulator (AOM) is used to generate a pulse train used to injection seed an erbium doped fiber amplifier (EDFA) to produce eye-safe laser pulses with maximum pulse energies of 66 J and a pulse repetition frequency of 15 kHz. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a fiber coupled photo-multiplier tube (PMT) module operating in the photon counting mode. The PMT has a 3% quantum efficiency, a dark count rate of 90 kHz, and a maximum count rate of 1 MHz. Recently, a fiber coupled avalanche photodiode (APD) operating in the geiger mode has been incorporated into the DIAL receiver. The APD has a quantum efficiency of 10%, a dark count rate of 10 kHz, and a maximum count rate of 1 MHz and provides a much larger dynamic range than the PMT. Both the PMT and APD provide TTL logic pulses that are monitored using a multichannel scaler card used to count the return photons as a function of time of flight and are thus interchangeable. The DIAL instrument was developed at the 1.571 m wavelength to take advantage of commercial-off-the-shelf components. The instrument is operated using a custom Labview program that switches to the DMLD operating at the on-line wavelength, locks this laser to a user defined wavelength setting, and collects return signals for a user defined time. The control program switches to the DMLD operating at the off

  11. Side-line tunable laser transmitter for differential absorption lidar measurements of CO2: design and application to atmospheric measurements

    NASA Astrophysics Data System (ADS)

    Koch, Grady J.; Beyon, Jeffrey Y.; Gibert, Fabien; Barnes, Bruce W.; Ismail, Syed; Petros, Mulugeta; Petzar, Paul J.; Yu, Jirong; Modlin, Edward A.; Davis, Kenneth J.; Singh, Upendra N.

    2008-03-01

    A 2 μm wavelength, 90 mJ, 5 Hz pulsed Ho laser is described with wavelength control to precisely tune and lock the wavelength at a desired offset up to 2.9 GHz from the center of a CO2 absorption line. Once detuned from the line center the laser wavelength is actively locked to keep the wavelength within 1.9 MHz standard deviation about the setpoint. This wavelength control allows optimization of the optical depth for a differential absorption lidar (DIAL) measuring atmospheric CO2 concentrations. The laser transmitter has been coupled with a coherent heterodyne receiver for measurements of CO2 concentration using aerosol backscatter; wind and aerosols are also measured with the same lidar and provide useful additional information on atmospheric structure. Range-resolved CO2 measurements were made with <2.4% standard deviation using 500 m range bins and 6.7 min⁡ (1000 pulse pairs) integration time. Measurement of a horizontal column showed a precision of the CO2 concentration to <0.7% standard deviation using a 30 min⁡ (4500 pulse pairs) integration time, and comparison with a collocated in situ sensor showed the DIAL to measure the same trend of a diurnal variation and to detect shorter time scale CO2 perturbations. For vertical column measurements the lidar was setup at the WLEF tall tower site in Wisconsin to provide meteorological profiles and to compare the DIAL measurements with the in situ sensors distributed on the tower up to 396 m height. Assuming the DIAL column measurement extending from 153 m altitude to 1353 m altitude should agree with the tower in situ sensor at 396 m altitude, there was a 7.9 ppm rms difference between the DIAL and the in situ sensor using a 30 min⁡ rolling average on the DIAL measurement.

  12. A Ground-Based Profiling Differential Absorption LIDAR System for Measuring CO2 in the Planetary Boundary Layer

    NASA Technical Reports Server (NTRS)

    Andrews, Arlyn E.; Burris, John F.; Abshire, James B.; Krainak, Michael A.; Riris, Haris; Sun, Xiao-Li; Collatz, G. James

    2002-01-01

    Ground-based LIDAR observations can potentially provide continuous profiles of CO2 through the planetary boundary layer and into the free troposphere. We will present initial atmospheric measurements from a prototype system that is based on components developed by the telecommunications industry. Preliminary measurements and instrument performance calculations indicate that an optimized differential absorption LIDAR (DIAL) system will be capable of providing continuous hourly averaged profiles with 250m vertical resolution and better than 1 ppm precision at 1 km. Precision increases (decreases) at lower (higher) altitudes and is directly proportional to altitude resolution and acquisition time. Thus, precision can be improved if temporal or vertical resolution is sacrificed. Our approach measures absorption by CO2 of pulsed laser light at 1.6 microns backscattered from atmospheric aerosols. Aerosol concentrations in the planetary boundary layer are relatively high and are expected to provide adequate signal returns for the desired resolution. The long-term goal of the project is to develop a rugged, autonomous system using only commercially available components that can be replicated inexpensively for deployment in a monitoring network.

  13. Liquid Water Cloud Measurements Using the Raman Lidar Technique: Current Understanding and Future Research Needs

    NASA Technical Reports Server (NTRS)

    Tetsu, Sakai; Whiteman, David N.; Russo, Felicita; Turner, David D.; Veselovskii, Igor; Melfi, S. Harvey; Nagai, Tomohiro; Mano, Yuzo

    2013-01-01

    This paper describes recent work in the Raman lidar liquid water cloud measurement technique. The range-resolved spectral measurements at the National Aeronautics and Space Administration Goddard Space Flight Center indicate that the Raman backscattering spectra measured in and below low clouds agree well with theoretical spectra for vapor and liquid water. The calibration coefficients of the liquid water measurement for the Raman lidar at the Atmospheric Radiation Measurement Program Southern Great Plains site of the U.S. Department of Energy were determined by comparison with the liquid water path (LWP) obtained with Atmospheric Emitted Radiance Interferometer (AERI) and the liquid water content (LWC) obtained with the millimeter wavelength cloud radar and water vapor radiometer (MMCR-WVR) together. These comparisons were used to estimate the Raman liquid water cross-sectional value. The results indicate a bias consistent with an effective liquid water Raman cross-sectional value that is 28%-46% lower than published, which may be explained by the fact that the difference in the detectors' sensitivity has not been accounted for. The LWP of a thin altostratus cloud showed good qualitative agreement between lidar retrievals and AERI. However, the overall ensemble of comparisons of LWP showed considerable scatter, possibly because of the different fields of view of the instruments, the 350-m distance between the instruments, and the horizontal inhomogeneity of the clouds. The LWC profiles for a thick stratus cloud showed agreement between lidar retrievals andMMCR-WVR between the cloud base and 150m above that where the optical depth was less than 3. Areas requiring further research in this technique are discussed.

  14. Measuring Tropospheric Winds from Space Using a Coherent Doppler Lidar Technique

    NASA Technical Reports Server (NTRS)

    Miller, Timothy L.; Kavaya, Michael J.; Emmitt, G. David

    1999-01-01

    The global measurement of tropospheric wind profiles has been cited by the operational meteorological community as the most important missing element in the present and planned observing system. The most practical and economical method for obtaining this measurement is from low earth orbit, utilizing a Doppler lidar (laser radar) technique. Specifically, this paper will describe the coherent Doppler wind lidar (CDWL) technique, the design and progress of a current space flight project to fly such a system on the Space Shuttle, and plans for future flights of similar instruments. The SPARCLE (SPAce Readiness Coherent Lidar Experiment) is a Shuttle-based instrument whose flight is targeted for March, 2001. The objectives of SPARCLE are three-fold: Confirm that the coherent Doppler lidar technique can measure line-of-sight winds to within 1-2 m/s accuracy; Collect data to permit validation and improvement of instrument performance models to enable better design of future missions; and Collect wind and backscatter data for future mission optimization and for atmospheric studies. These objectives reflect the nature of the experiment and its program sponsor, NASA's New Millennium Program. The experiment is a technology validation mission whose primary purpose is to provide a space flight validation of this particular technology. (It should be noted that the CDWL technique has successfully been implemented from ground-based and aircraft-based platforms for a number of years.) Since the conduct of the SPARCLE mission is tied to future decisions on the choice of technology for free-flying, operational missions, the collection of data is intrinsically tied to the validation and improvement of instrument performance models that predict the sensitivity and accuracy of any particular present or future instrument system. The challenges unique to space flight for an instrument such as SPARCLE and follow-ons include: Obtaining the required lidar sensitivity from the long distance

  15. A mobile differential absorption lidar to measure sub-hourly fluctuation of tropospheric ozone profiles in the Baltimore-Washington, D.C. region

    NASA Astrophysics Data System (ADS)

    Sullivan, J. T.; McGee, T. J.; Sumnicht, G. K.; Twigg, L. W.; Hoff, R. M.

    2014-10-01

    Tropospheric ozone profiles have been retrieved from the new ground-based National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) in Greenbelt, MD (38.99° N, 76.84° W, 57 m a.s.l.), from 400 m to 12 km a.g.l. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the Tropospheric Ozone Lidar Network (TOLNet) has been developed, which currently consists of five stations across the US. The GSFC TROPOZ DIAL is based on the DIAL technique, which currently detects two wavelengths, 289 and 299 nm, with multiple receivers. The transmitted wavelengths are generated by focusing the output of a quadrupled Nd:YAG laser beam (266 nm) into a pair of Raman cells, filled with high-pressure hydrogen and deuterium, using helium as buffer gas. With the knowledge of the ozone absorption coefficient at these two wavelengths, the range-resolved number density can be derived. An interesting atmospheric case study involving the stratospheric-tropospheric exchange (STE) of ozone is shown, to emphasize the regional importance of this instrument as well as to assess the validation and calibration of data. There was a low amount of aerosol aloft, and an iterative aerosol correction has been performed on the retrieved data, which resulted in less than a 3 ppb correction to the final ozone concentration. The retrieval yields an uncertainty of 16-19% from 0 to 1.5 km, 10-18% from 1.5 to 3 km, and 11-25% from 3 to 12 km according to the relevant aerosol concentration aloft. There are currently surface ozone measurements hourly and ozonesonde launches occasionally, but this system will be the first to make routine tropospheric ozone profile measurements in the Baltimore-Washington, D.C. area.

  16. Lidar reflectance from snow at 2.05  μm wavelength as measured by the JPL Airborne Laser Absorption Spectrometer.

    PubMed

    Spiers, Gary D; Menzies, Robert T; Jacob, Joseph C

    2016-03-10

    We report airborne measurements of lidar directional reflectance (backscatter) from land surfaces at a wavelength in the 2.05 μm CO₂ absorption band, with emphasis on snow-covered surfaces in various natural environments. Lidar backscatter measurements using this instrument provide insight into the capabilities of lidar for both airborne and future global-scale CO₂ measurements from low Earth orbit pertinent to the NASA Active Sensing of CO₂ Emissions over Nights, Days, and Seasons mission. Lidar measurement capability is particularly useful when the use of solar scattering spectroscopy is not feasible for high-accuracy atmospheric CO₂ measurements. Consequently, performance in high-latitude and winter season environments is an emphasis. Snow-covered surfaces are known to be dark in the CO₂ band spectral regions. The quantitative backscatter data from these field measurements help to elucidate the range of backscatter values that can be expected in natural environments.

  17. Improving the Current Understanding of the Evolution and Vertical Processes of Tropospheric Ozone Using a Ground Based Differential Absorption Lidar

    NASA Astrophysics Data System (ADS)

    Sullivan, John T.

    Although characterizing the interactions of ozone throughout the entire troposphere are important for health and climate processes, there is a lack of routine measurements of vertical profiles within the United States. Current atmospheric satellite instruments cannot peer through the optically thick stratospheric ozone layer to remotely sense boundary layer tropospheric ozone. In order to monitor this lower ozone more effectively, the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center TROPospheric OZone DIfferential Absorption Lidar (GSFC TROPOZ DIAL) has been developed and validated within the Tropospheric Ozone Lidar Network (TOLNet). Two scientifically interesting ozone episodes are presented that were observed during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER AQ) campaign at Ft. Collins, Colorado. The GSFC TROPOZ DIAL measurements are analyzed alongside aircraft spirals over the lidar site, co-located ozonesonde launches, aerosol lidar profiles and other TOLNet ozone lidar profiles. In both case studies, back trajectories, meteorological maps, and comparisons to air quality models are presented to better explain the sources and evolution of ozone. The first case study, occurring between 22-23 July 2014, indicates enhanced concentrations of ozone at Ft. Collins during nighttime hours, which was due to the complex recirculation of ozone within the foothills of the Rocky Mountain region. Although quantifying the ozone increase aloft during recirculation episodes has been historically difficult, results indicate that an increase of 20 - 30 ppbv of ozone at the Ft. Collins site has been attributed to this recirculation. The second case, occurring between Aug 4-8th 2014, characterizes a dynamical exchange of ozone between the stratosphere and the troposphere. This case, along with seasonal model parameters from previous years, is used to estimate

  18. Study of absolute detection technique with the rotational Raman lidar for atmospheric temperature

    NASA Astrophysics Data System (ADS)

    Li, Shichun; Wei, Pengpeng; Gong, Xin; Hua, Dengxin

    2015-10-01

    The rotational Raman lidar is a valid tool to profile atmospheric temperature. But the fact that its proper operation generally needs a certain collocated device for calibration seriously restricts application in the meteorology and environment fields. We propose an absolute detection technique of atmospheric temperature with the rotational Raman lidar, which is based on the dependence of rotational Raman spectral envelope on temperature. To retrieve atmospheric temperature without calibration, six rotational Raman spectra of nitrogen molecule are chosen from the anti-Strokes branch. A temperature retrieval algorithm is presented and analyzed based on the least square principle. A two-cascade Raman spectroscopic filter is constructed by one first-order diffraction grating, one convex lens, one linear fiber array and 6 groups of fiber Bragg gratings. This lidar is configured with a 300-mJ pulse energy laser and a 250-mm clear aperture telescope. Simulation results show that it can extract the nitrogen molecules rotational Raman spectral lines, and that atmospheric temperature profile obtained through absolute retrieval algorithm can be up to 3.5 km with less than 0.5-K deviation within 17 minutes interval.

  19. Super-resolution technique for CW lidar using Fourier transform reordering and Richardson-Lucy deconvolution.

    PubMed

    Campbell, Joel F; Lin, Bing; Nehrir, Amin R; Harrison, F Wallace; Obland, Michael D

    2014-12-15

    An interpolation method is described for range measurements of high precision altimetry with repeating intensity modulated continuous wave (IM-CW) lidar waveforms using binary phase shift keying (BPSK), where the range profile is determined by means of a cross-correlation between the digital form of the transmitted signal and the digitized return signal collected by the lidar receiver. This method uses reordering of the array elements in the frequency domain to convert a repeating synthetic pulse signal to single highly interpolated pulse. This is then enhanced further using Richardson-Lucy deconvolution to greatly enhance the resolution of the pulse. We show the sampling resolution and pulse width can be enhanced by about two orders of magnitude using the signal processing algorithms presented, thus breaking the fundamental resolution limit for BPSK modulation of a particular bandwidth and bit rate. We demonstrate the usefulness of this technique for determining cloud and tree canopy thicknesses far beyond this fundamental limit in a lidar not designed for this purpose. PMID:25503046

  20. Analysis of transmission spectra for large ratio of emission-to-absorber linewidths: extension of differential absorption lidar analysis for finite laser linewidths.

    PubMed

    Klett, James D

    2005-07-10

    A simple algorithm is presented for the analysis of transmission spectra provided by a lidar with an emission linewidth that is comparable with or larger than the absorption features of interest. The spreading of line shapes as seen by the lidar precludes use of the classical differential absorption lidar (DIAL) approach. However, it is assumed that, as with the DIAL method, small spectral intervals exist where single absorbers are dominant, and an inversion process for the transmission over such intervals is carried out for the absorber concentration. A second-stage algorithm based on singular-value decomposition is also provided to improve further the concentration estimates. An example situation for use of the algorithms is included wherein the objective is to estimate the concentration of a known trace gas in a composite transmission spectrum in the mid-infrared, where the dominant absorbers are water vapor and methane.

  1. An Ozone Differential Absorption Lidar (DIAL) Receiver System for Use on Unpiloted Atmospheric Vehicles

    NASA Technical Reports Server (NTRS)

    DeYoung, Russell J.; Goldschmidt, Soenke

    1999-01-01

    Measurements of global atmosphere ozone concentrations call for flexible lidar systems that can be operated from an unpiloted atmospheric vehicle (UAV) to reduce the cost of measurement missions. A lidar receiver system consisting of a fiber-optic-coupled telescope has been designed and tested for this purpose. The system weight is 13 kg and its volume of 0.06 m 3 would fit into the payload compartment of a Perseus B UAV. The optical efficiency of the telescope is 37 percent at 288 nm and 64 percent at 300 nm. Atmospheric measurements with a DIAL laser system have been performed, and the measured ozone density has matched the data from ozonesondes to an altitude of 7 km.

  2. Airborne Differential Absorption and High Spectral Resolution Lidar Measurements for Cirrus Cloud Studies

    NASA Astrophysics Data System (ADS)

    Gross, Silke; Schaefler, Andreas; Wirth, Martin; Fix, Andreas

    2016-06-01

    Aerosol and water vapor measurements were performed with the lidar system WALES of the German Aerospace Center (DLR) onboard the German research aircraft G550-HALO during the HALO Techno-Mission in October and November 2010 and during the ML-Cirrus mission in March and April 2014 over Central Europe and the North Atlantic region. Curtains composed of lidar profiles beneath the aircraft show the water vapor mixing ratio and the backscatter ratio. Temperature data from ECMWF model analysis are used to calculate the relative humidity above ice (RHi) in the 2-D field along the flight track to study the RHi distribution inside and outside of cirrus clouds at different stages of cloud evolution.

  3. Atmospheric Backscatter Profiles at 765nm and 1572nm from Pulsed Lidar Measurements of CO2 and O2 Column Absorption from the 2013 ASCENDS Flight Campaign

    NASA Astrophysics Data System (ADS)

    Allan, G. R.; Riris, H.; Hasselbrack, W.; Rodriguez, M.; Ramanathan, A.; Sun, X.; Mao, J.; Abshire, J. B.

    2013-12-01

    We present height-resolved, range corrected, backscatter profiles from NASA GSFC's two-channel (CO2 & O2) sounder, an Integrated Path Differential Absorption (IPDA) lidar, which measures simultaneously both carbon dioxide & oxygen column absorptions. These backscatter profiles show clear evidence of multiple backscattering layers, clouds & aerosols, which allows for the identification of the Planetary Boundary Layer (PBL). The backscatter measurements enable sampling of the vertical distribution of CO2 in the atmosphere when broken & thin clouds are present & may help identify sources & sinks within the PBL as opposed to natural variations in the vertical distribution of CO2. The CO2 Sounder is an airborne pulsed lidar for active remote measurements of CO2 abundance & is a candidate for NASA's ASCENDS mission (Active Sensing of CO2 Emissions over Nights, Days & Seasons). The O2 channel measures atmospheric pressure in the same air column to calculate the dry mixing ratio of CO2. The lidars use a scanning, pulsed laser & fiber amplifier in a Master Oscillator Power Amplifier configuration to measure lineshape, range to scattering surface & backscatter profiles. The CO2 channel operates at 1572.335 nm. The O2 channel uses similar technology but frequency doubles the output from ~1530nm to the O2 A-band absorption around 765nm. Both lasers are scanned across the absorption feature of interest sampling the line at a fixed number of discrete wavelengths per scan around ~300 scans per second. The time-resolved return signal is detected by photon-counting detectors with a temporal resolution of a few nanoseconds. The CO2 channel uses a PMT while the O2 channel uses Single Photon Counting Modules. The detectors are fiber coupled to a 2m f10 Schmidt-Cassegrain telescope. The column density of the gas of interest is estimated from the differential optical depths of the scanned absorption using the IPDA technique & the optical path from the time of flight. A backscatter

  4. Feasibility of tropospheric water vapor profiling using infrared heterodyne differential absorption lidar

    SciTech Connect

    Grund, C.J.; Hardesty, R.M.; Rye, B.J.

    1996-04-01

    The development and verification of realistic climate model parameterizations for clouds and net radiation balance and the correction of other site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. In this study, we develop system performance models and examine the potential of infrared differential absoroption lidar (DIAL) to determine the concentration of water vapor.

  5. Backscattering measurements of atmospheric aerosols at CO2 laser wavelengths: implications of aerosol spectral structure on differential-absorption lidar retrievals of molecular species.

    PubMed

    Ben-David, A

    1999-04-20

    The volume backscattering coefficients of atmospheric aerosol were measured with a tunable CO2 lidar system at various wavelengths in Utah (a desert environment) along a horizontal path a few meters above the ground. In deducing the aerosol backscattering, a deconvolution (to remove the smearing effect of the long CO2 lidar pulse and the lidar limited bandwidth) and a constrained-slope method were employed. The spectral shape beta(lambda) was similar for all the 13 measurements during a 3-day period. A mean aerosol backscattering-wavelength dependence beta(lambda) was computed from the measurements and used to estimate the error Delta(CL) (concentration-path-length product) in differential-absorption lidar measurements for various gases caused by the systematic aerosol differential backscattering and the error that is due to fluctuations in the aerosol backscattering. The water-vapor concentration-path-length product CL and the average concentration C = /L for a path length L computed from the range-resolved lidar measurements is consistently in good agreement with the water-vapor concentration measured by a meteorological station. However, I was unable to deduce, reliably, the range-resolved water-vapor concentration C(r), which is the derivative of the range-dependent product CL, because of the effect of residual noise caused mainly by errors in the deconvolved lidar measurements.

  6. Injection-seeded alexandrite ring laser: performance and application in a water-vapor differential absorption lidar.

    PubMed

    Wulfmeyer, V; Bösenberg, J; Lehmann, S; Senff, C; Schmitz, S

    1995-03-15

    A new laser system for use of differential absorption lidar (DIAL) in measurements of tropospheric water vapor and temperature is introduced. This system operates in the 720-780-nm region and is configured as an alexandrite ring laser injection seeded by a cw Ti:sapphire ring laser. This combination provides for the necessary narrow-bandwidth, high-frequency stability and excellent spectral purity. A bandwidth of <5.0 x 10(-3) cm(-1), a frequency stability of 2.1 x 10(-3) cm(-1) rms, and a spectral purity of 99.995% at 726 nm have been achieved during extended periods of operation. A comparison of a DIAL water-vapor measurement with a radiosonde in the boundary layer between 500 and 2000 m was performed. The maximum deviation between the humidity profiles is 15%, the standard deviation 1.6%, and the difference between the mean values 1%.

  7. Coherent 2 microm differential absorption and wind lidar with conductively cooled laser and two-axis scanning device.

    PubMed

    Ishii, Shoken; Mizutani, Kohei; Fukuoka, Hirotake; Ishikawa, Takayoshi; Philippe, Baron; Iwai, Hironari; Aoki, Tetsuo; Itabe, Toshikazu; Sato, Atsushi; Asai, Kazuhiro

    2010-04-01

    A coherent 2 microm differential absorption and wind lidar (Co2DiaWiL) was developed to measure CO(2) concentration and line-of-sight wind speed. We conductively cooled a pumping laser head to -80 degrees C and diode arrays to approximately 20 degrees C. A Q-switched laser outputs an energy of 80 mJ (pulse width 150 ns (FWHM), pulse repetition frequency up to 30 Hz). CO(2) measurements made over a column range (487-1986 m) for 5 min accumulation time pairs achieved 0.7% precision. Line-of-sight wind speeds for ranges up to approximately 20 km and returns from a mountainside located 24 km away from the Co2DiaWiL were obtained. PMID:20357863

  8. CHARM-F: An airborne integral path differential absorption lidar for simultaneous measurements of carbon dioxide and methane columns

    NASA Astrophysics Data System (ADS)

    Amediek, A.; Büdenbender, H.-C.; Ehret, G.; Fix, A.; Kiemle, C.; Quatrevalet, M.; Wirth, M.; Hoffmann, D.; Löhring, J.; Klein, V.

    2012-04-01

    CHARM-F (CO2 and CH4 Atmospheric Remote Monitoring - Flugzeug) is DLR's airborne Integral Path Differential Absorption (IPDA) lidar for simultaneous measurements of the column-weighted average dry-air mixing ratios of atmospheric carbon dioxide and methane, designed to be flown on DLR's new High-Altitude, LOng-range research aircraft, HALO. It is meant to serve as a demonstrator of the use of spaceborne active optical instruments in inferring atmospheric CO2 and CH4 surface fluxes from total column measurements by inverse modeling. As it will be shown, this is enabled by HALO's high flight altitude and its range of 8000 km, which will make it possible to produce real-world data at truly regional scales with a viewing geometry and vertical weighting function similar to those enabled by a space platform. In addition, CHARM-F has the potential to be used as a validation tool not only for active but also passive spaceborne instruments utilizing scattered solar radiation for remote sensing of greenhouse gases. Building on the expertise from CHARM, a helicopter-borne methane IPDA lidar for pipeline monitoring developed in collaboration with E.ON, and WALES, DLR's water vapour differential absorption lidar, CHARM-F relies on a double-pulse transmitter architecture producing nanosecond pulses which allows for a precise ranging and a clean separation of atmospheric influences from the ground returns leading to an unambiguously defined column. One pulse is tuned to an absorption line of the trace gas under consideration, the other to a nearby wavelength with much less absorption. The close temporal separation of 250 μs within each pulse pair ensures that nearly the same spot on ground is illuminated. The ratio of both return signals is then a direct function of the column-weighted average dry-air mixing ratio. The two laser systems, one for each trace gas, use highly efficient and robust Nd:YAG lasers to pump an optical parametric oscillator (OPO) level which converts the

  9. Note: A sub-sampling technique for frequency locking in Doppler wind lidar.

    PubMed

    Yao, Yuan; Li, Feng; Chen, Lian; Jin, Ge

    2016-05-01

    Double-edge technique is employed in Doppler wind lidar for detecting the Doppler frequency shift. A dedicated locking channel, employing one channel of a triple Fabry-Perot etalon, is designed to compensate for the effects caused by the frequency drift of outgoing laser. Agilent Oscilloscopes, with a sampling rate of 2.5 GSPS, are employed to obtain accurate amplitudes of the narrow pulses in existing experiments. In order to achieve the requirement of real-time ability and integration, a sub-sampling technique based on the theory of statistics is presented. With the technique, the drift can be acquired at a sub-sampling rate, 250 MSPS. A prototype is designed and the test results show that the prototype, providing real-time ability and better integration, has a comparable performance as the oscilloscope for frequency locking. PMID:27250482

  10. Lidar investigations of atmospheric dynamics

    NASA Astrophysics Data System (ADS)

    Philbrick, C. Russell; Hallen, Hans D.

    2015-09-01

    Ground based lidar techniques using Raleigh and Raman scattering, differential absorption (DIAL), and supercontinuum sources are capable of providing unique signatures to study dynamical processes in the lower atmosphere. The most useful profile signatures of dynamics in the lower atmosphere are available in profiles of time sequences of water vapor and aerosol optical extinction obtained with Raman and DIAL lidars. Water vapor profiles are used to study the scales and motions of daytime convection cells, residual layer bursts into the planetary boundary layer (PBL), variations in height of the PBL layer, cloud formation and dissipation, scale sizes of gravity waves, turbulent eddies, as well as to study the seldom observed phenomena of Brunt-Väisälä oscillations and undular bore waves. Aerosol optical extinction profiles from Raman lidar provide another tracer of dynamics and motion using sequential profiles atmospheric aerosol extinction, where the aerosol distribution is controlled by dynamic, thermodynamic, and photochemical processes. Raman lidar profiles of temperature describe the stability of the lower atmosphere and measure structure features. Rayleigh lidar can provide backscatter profiles of aerosols in the troposphere, and temperature profiles in the stratosphere and mesosphere, where large gravity waves, stratospheric clouds, and noctilucent clouds are observed. Examples of several dynamical features are selected to illustrate interesting processes observed with Raman lidar. Lidar experiments add to our understanding of physical processes that modify atmospheric structure, initiate turbulence and waves, and describe the relationships between energy sources, atmospheric stability parameters, and the observed dynamics.

  11. The Polarization Lidar Technique for Cloud Research: A Review and Current Assessment.

    NASA Astrophysics Data System (ADS)

    Sassen, Kenneth

    1991-12-01

    The development of the polarization lidar field over the past two decades is reviewed, and the current cloud-research capabilities and limitations are evaluated. Relying on fundamental scattering principles governing the interaction of polarized laser light with distinctly shaped hydrometers, this remote-sensing technique has contributed to our knowledge of the composition and structure of a variety of cloud types. For example, polarization lidar is a key component of current climate-research programs to characterize the properties of cirrus clouds, and is an integral part of multiple remote-sensor studies of mixed-phase cloud systems, such as winter mountain storms. Although unambiguous cloud-phase discrimination and the identification of some ice particle types and orientations are demonstrated capabilities, recent theoretical approaches involving ice crystal ray-tracing and cloud microphysical model simulations are, promising to increase the utility of the technique. New results simulating the single and multiple scattering properties of precipitating mixed-phase clouds are given for illustration of such methods.

  12. Lidar Technique for Early Forest Fire Detection : Design and Development Aspects

    NASA Astrophysics Data System (ADS)

    Traïche, M.; Bourai, K.; Moussaoui, N.; Beggar, R.; Almabouada, F.; Louhibi, D.

    2008-09-01

    Many countries suffer from forest fires every summer, a phenomenon which wreaks havoc on both local and global environment. As well, it causes enormous damage to public health especially for people living in surrounding areas. For fighting against forest fires, ocular surveillance, in spite of its wide use, is not efficient owing to the costly mobilization of a great number of forest agents and to the fact that most of forest regions are not accessible. Other passive techniques such as infrared camera remote sensing are neither efficient under unfavorable weather conditions. An efficient way to early detect forest fires even under worse environmental conditions and in inaccessible mountainous regions uses the backscattering Lidar technique. This consists of the emission of monowavelength laser pulses spanning azimuthally the entire region subject to surveillance and the detection of the backscattered signal. The detection parameter is the signal to noise ration SNR. In this contribution, we will deal with approach and design aspects inherent to the development task of such a Lidar.

  13. Theory of the double-edge molecular technique for Doppler lidar wind measurement.

    PubMed

    Flesia, C; Korb, C L

    1999-01-20

    The theory of the double-edge lidar technique for measuring the wind with molecular backscatter is described. Two high-spectral-resolution edge filters are located in the wings of the Rayleigh-Brillouin profile. This doubles the signal change per unit Doppler shift, the sensitivity, and improves measurement accuracy relative to the single-edge technique by nearly a factor of 2. The use of a crossover region where the sensitivity of a molecular- and an aerosol-based measurement is equal is described. Use of this region desensitizes the molecular measurement to the effects of aerosol scattering over a velocity range of +/-100 m/s. We give methods for correcting short-term, shot-to-shot, frequency jitter and drift with a laser reference frequency measurement and methods for long-term frequency correction with a servo control system. The effects of Rayleigh-Brillouin scattering on the measurement are shown to be significant and are included in the analysis. Simulations for a conical scanning satellite-based lidar at 355 nm show an accuracy of 2-3 m/s for altitudes of 2-15 km for a 1-km vertical resolution, a satellite altitude of 400 km, and a 200 km x 200 km spatial resolution. PMID:18305631

  14. Comprehensive view of high-spectral-resolution lidar technique from the perspective of spectral discrimination

    NASA Astrophysics Data System (ADS)

    Cheng, Zhongtao; Liu, Dong; Yang, Yongying; Luo, Jing; Zhang, Yupeng; Zhou, Yudi; Bai, Jian; Liu, Chong; Shen, Yibing

    2016-05-01

    As already known commonly, high-spectral-resolution lidar technique (HSRL) employs a narrowband spectroscopic filter to separate the elastic backscattered aerosol signal from the thermal Doppler broadened molecular backscattered contribution. This paper presents a new and comprehensive view of HSRL technique from the perspective of spectral discrimination, without concretizing the analysis into a specific spectral discrimination filter. Based on a general HSRL layout with three-channel configuration, a theoretical model of retrieval error evaluation is introduced. In this model, we only take the error sources related to the spectral discrimination parameters into account, and ignore other error sources not associated with these focused parameters. This theoretical model is subsequently verified by Monte Carlo (MC) simulations. Both the model and MC simulations demonstrate that a large molecular transmittance and a large spectral discrimination ratio (SDR, i.e., ratio of the molecular transmittance to the aerosol transmittance) are beneficial to reduce the retrieval error. Moreover, we find that the signal-to-noise ratio (SNR) and SDR of the lidar system are often tradeoffs, and we suggest considering a suitable SDR for higher molecular transmittance (thus higher SNR) instead of using unnecessarily high SDR when designing the spectral discrimination filter. This view interprets the function of the narrowband spectroscopic filter in HSRL system essentially, and will provide some general guidelines for the reasonable design of the spectral discrimination filter for HSRL community.

  15. A Broad Bank Lidar for Precise Atmospheric CO2 Column Absorption Measurement from Space

    NASA Technical Reports Server (NTRS)

    Georgieva, E. M.; Heaps, W. S.; Huang, W.

    2010-01-01

    Accurate global measurement of carbon dioxide column with the aim of discovering and quantifying unknown sources and sinks has been a high priority for the last decade. In order to uncover the "missing sink" that is responsible for the large discrepancies in the budget the critical precision for a measurement from space needs to be on the order of 1 ppm. To better understand the CO2 budget and to evaluate its impact on global warming the National Research Council (NRC) in its recent decadal survey report (NACP) to NASA recommended a laser based total CO2 mapping mission in the near future. That's the goal of Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission - to significantly enhance the understanding of the role of CO2 in the global carbon cycle. Our current goal is to develop an ultra precise, inexpensive new lidar system for column measurements of CO2 changes in the lower atmosphere that uses a Fabry-Perot interferometer based system as the detector portion of the instrument and replaces the narrow band laser commonly used in lidars with a high power broadband source. This approach reduces the number of individual lasers used in the system and considerably reduces the risk of failure. It also tremendously reduces the requirement for wavelength stability in the source putting this responsibility instead on the Fabry- Perot subsystem.

  16. Oxygen detection using the laser diode absorption technique

    NASA Technical Reports Server (NTRS)

    Disimile, P. J.; Fox, C. W.

    1991-01-01

    Accurate measurement of the concentration and flow rate of gaseous oxygen is becoming of greater importance. The detection technique presented is based on the principal of light absorption by the Oxygen A-Band. Oxygen molecules have characteristics which attenuate radiation in the 759-770 nm wavelength range. With an ability to measure changes in the relative light transmission to less than 0.01 percent, a sensitive optical gas detection system was configured. This system is smaller in size and light in weight, has low energy requirements and has a rapid response time. In this research program, the application of temperature tuning laser diodes and their ability to be wavelength shifted to a selected absorption spectral peak has allowed concentrations as low as 1300 ppm to be detected.

  17. Additional development of remote sensing techniques for observing morphology, microphysics, and radiative properties of clouds and tests using a new, robust CO{sub 2} lidar. Final report

    SciTech Connect

    Eberhard, W.L.; Brewer, W.A.; Intrieri, J.M.

    1998-09-28

    A three-year project with a goal of advancing CO{sub 2} lidar technology and measurement techniques for cloud studies was successfully completed. An eyesafe, infrared lidar with good sensitivity and improved Doppler accuracy was designed, constructed, and demonstrated. Dual-wavelength operation was achieved. A major leap forward in robustness was demonstrated. CO{sub 2} lidars were operated as part of two Intensive Operations Periods at the Southern Great Plains CART site. The first used an older lidar and was intended primarily for measurement technique development. The second used the new lidar and was primarily a demonstration and evaluation of its performance. Progress was demonstrated in the development, evaluation, and application of measurement techniques using CO{sub 2} lidar.

  18. Integrated Path Differential Absorption Lidar Optimizations Based on Pre-Analyzed Atmospheric Data for ASCENDS Mission Applications

    NASA Technical Reports Server (NTRS)

    Pliutau, Denis; Prasad, Narasimha S.

    2012-01-01

    In this paper a modeling method based on data reductions is investigated which includes pre analyzed MERRA atmospheric fields for quantitative estimates of uncertainties introduced in the integrated path differential absorption methods for the sensing of various molecules including CO2. This approach represents the extension of our existing lidar modeling framework previously developed and allows effective on- and offline wavelength optimizations and weighting function analysis to minimize the interference effects such as those due to temperature sensitivity and water vapor absorption. The new simulation methodology is different from the previous implementation in that it allows analysis of atmospheric effects over annual spans and the entire Earth coverage which was achieved due to the data reduction methods employed. The effectiveness of the proposed simulation approach is demonstrated with application to the mixing ratio retrievals for the future ASCENDS mission. Independent analysis of multiple accuracy limiting factors including the temperature, water vapor interferences, and selected system parameters is further used to identify favorable spectral regions as well as wavelength combinations facilitating the reduction in total errors in the retrieved XCO2 values.

  19. Detection and monitoring of pollutant sources with Lidar/Dial techniques

    NASA Astrophysics Data System (ADS)

    Gaudio, P.; Gelfusa, M.; Malizia, A.; Parracino, S.; Richetta, M.; De Leo, L.; Perrimezzi, C.; Bellecci, C.

    2015-11-01

    It's well known that air pollution due to anthropogenic sources can have adverse effects on humans and the ecosystem. Therefore, in the last years, surveying large regions of the atmosphere in an automatic way has become a strategic objective of various public health organizations for early detection of pollutant sources in urban and industrial areas. The Lidar and Dial techniques have become well established laser based methods for the remote sensing of the atmosphere. They are often implemented to probe almost any level of the atmosphere and to acquire information to validate theoretical models about different topics of atmospheric physics. They can also be used for environment surveying by monitoring particles, aerosols and molecules. The aim of the present work is to demonstrate the potential of these methods to detect pollutants emitted from local sources (such as particulate and/or chemical compounds) and to evaluate their concentration. This is exemplified with the help of experimental data acquired in an industrial area in the south of Italy by mean of experimental campaign by use of pollutants simulated source. For this purpose, two mobile systems Lidar and Dial have been developed by the authors. In this paper there will be presented the operating principles of the system and the results of the experimental campaign.

  20. 315mJ, 2-micrometers Double-Pulsed Coherent Differential Absorption Lidar Transmitter for Atmospheric CO2 Sensing

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo; Bai, Yingxin; Koch, Grady; Chen, Songsheng; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    The design of a double pulsed, injection seeded, 2-micrometer compact coherent Differential absorption Lidar (DIAL) transmitter for CO2 sensing is presented. This system is hardened for ground and airborne applications. The design architecture includes three continuous wave lasers which provide controlled on and off line seeding, injection seeded power oscillator and a single amplifier operating in double pass configuration. As the derivative a coherent Doppler wind lidar, this instrument has the added benefit of providing wind information. The active laser material used for this application is a Ho: Tm:YLF crystal operates at the eye-safe wavelength. The 3-meter long folded ring resonator produces energy of 130-mJ (90/40) with a temporal pulse length around 220 nanoseconds and 530 nanosecond pulses for on and off lines respectively. The separation between the two pulses is on the order of 200 microseconds. The line width is in the order of 2.5MHz and the beam quality has an M(sup 2) of 1.1 times diffraction limited beam. A final output energy for a pair of both on and off pulses as high as 315 mJ (190/125) at a repetition rate of 10 Hz is achieved. The operating temperature is set around 20 C for the pump diode lasers and 10 C for the rod. Since the laser design has to meet high-energy as well as high beam quality requirements, close attention is paid to the laser head design to avoid thermal distortion in the rod. A side-pumped configuration is used and heat is removed uniformly by passing coolant through a tube slightly larger than the rod to reduce thermal gradient. This paper also discusses the advantage of using a long upper laser level life time laser crystal for DIAL application. In addition issues related to injection seeding with two different frequencies to achieve a transform limited line width will be presented.

  1. New analytical technique for carbon dioxide absorption solvents

    SciTech Connect

    Pouryousefi, F.; Idem, R.O.

    2008-02-15

    The densities and refractive indices of two binary systems (water + MEA and water + MDEA) and three ternary systems (water + MEA + CO{sub 2}, water + MDEA + CO{sub 2}, and water + MEA + MDEA) used for carbon dioxide (CO{sub 2}) capture were measured over the range of compositions of the aqueous alkanolamine(s) used for CO{sub 2} absorption at temperatures from 295 to 338 K. Experimental densities were modeled empirically, while the experimental refractive indices were modeled using well-established models from the known values of their pure-component densities and refractive indices. The density and Gladstone-Dale refractive index models were then used to obtain the compositions of unknown samples of the binary and ternary systems by simultaneous solution of the density and refractive index equations. The results from this technique have been compared with HPLC (high-performance liquid chromatography) results, while a third independent technique (acid-base titration) was used to verify the results. The results show that the systems' compositions obtained from the simple and easy-to-use refractive index/density technique were very comparable to the expensive and laborious HPLC/titration techniques, suggesting that the refractive index/density technique can be used to replace existing methods for analysis of fresh or nondegraded, CO{sub 2}-loaded, single and mixed alkanolamine solutions.

  2. High-power Ti:sapphire laser at 820 nm for scanning ground-based water-vapor differential absorption lidar.

    PubMed

    Wagner, Gerd; Behrendt, Andreas; Wulfmeyer, Volker; Späth, Florian; Schiller, Max

    2013-04-10

    The Ti:sapphire (TISA) laser transmitter of the mobile, three-dimensional-scanning water-vapor differential absorption lidar (DIAL) of the University of Hohenheim is described in detail. The dynamically-stable, unidirectional ring resonator contains a single Brewster-cut TISA crystal, which is pumped from both sides with 250 Hz using a diode-pumped frequency-doubled Nd:YAG laser. The resonator is injection seeded and actively frequency-stabilized using a phase-sensitive technique. The TISA laser is operating near 820 nm, which is optimum for ground-based water-vapor DIAL measurements. An average output power of up to 6.75 W with a beam quality factor of M2<2 is reached. The pointing stability is <13 μrad (rms), the depolarization <1%. The overall optical-optical conversion efficiency is up to 19%. The pulse length is 40 ns with a pulse linewidth of <157 MHz. The short- and long-term frequency stabilities are 10 MHz (rms). A spectral purity of 99.9% was determined by pointing to a stratus cloud in low-elevation scanning mode with a cloud bottom height of ≈2.4 km. PMID:23670775

  3. New technique for retrieval of atmospheric temperature profiles from Rayleigh-scatter lidar measurements using nonlinear inversion.

    PubMed

    Khanna, Jaya; Bandoro, Justin; Sica, R J; McElroy, C Thomas

    2012-11-20

    The conventional method of calculating atmospheric temperature profiles using Rayleigh-scattering lidar measurements has limitations that necessitate abandoning temperatures retrieved at the greatest heights, due to the assumption of a pressure value required to initialize the integration at the highest altitude. An inversion approach is used to develop an alternative way of retrieving nightly atmospheric temperature profiles from the lidar measurements. Measurements obtained by the Purple Crow lidar facility located near The University of Western Ontario are used to develop and test this new technique. Our results show temperatures can be reliably retrieved at all heights where measurements with adequate signal-to-noise ratio exist. A Monte Carlo technique was developed to provide accurate estimates of both the systematic and random uncertainties for the retrieved nightly average temperature profile. An advantage of this new method is the ability to seed the temperature integration from the lowest rather than the greatest height, where the variability of the pressure is smaller than in the mesosphere or lower thermosphere and may in practice be routinely measured by a radiosonde, rather than requiring a rocket or satellite-borne measurement. Thus, this new technique extends the altitude range of existing Rayleigh-scatter lidars 10-15 km, producing the equivalent of four times the power-aperture product.

  4. Wave optics simulation of atmospheric turbulence and reflective speckle effects in CO2 differential absorption lidar (DIAL)

    NASA Astrophysics Data System (ADS)

    Nelson, Douglas H.; Petrin, Roger R.; MacKerrow, Edward P.; Schmitt, Mark J.; Quick, Charles R., Jr.; Zardecki, Andrew; Porch, William M.; Whitehead, Michael C.; Walters, Donald L.

    1998-09-01

    The measurement sensitivity of CO2 differential absorption LIDAR (DIAL) can be affected by a number of different processes. We will address the interaction of two of these processes: effects due to beam propagation through atmospheric turbulence and effects due to reflective speckle. Atmospheric turbulence affects the beam distribution of energy and phase on target. These effects include beam spreading, beam wander and scintillation which can result in increased shot-to-shot signal noise. In addition, reflective speckle alone has a major impact on the sensitivity of CO2 DIAL. The interaction of atmospheric turbulence and reflective speckle is of great importance in the performance of a DIAL system. A Huygens-Fresnel wave optics propagation code has previously been developed at the Naval Postgraduate School that models the effects of atmospheric turbulence as propagation through a series of phase screens with appropriate atmospheric statistical characteristics. This code has been modified to include the effects of reflective speckle. The performance of this modified code with respect to the combined effects of atmospheric turbulence and reflective speckle is examined. Results are compared with a combination of experimental data and analytical models.

  5. Investigation of PBL schemes combining the WRF model simulations with scanning water vapor differential absorption lidar measurements

    NASA Astrophysics Data System (ADS)

    Milovac, Josipa; Warrach-Sagi, Kirsten; Behrendt, Andreas; Späth, Florian; Ingwersen, Joachim; Wulfmeyer, Volker

    2016-01-01

    Six simulations with the Weather Research and Forecasting (WRF) model differing in planetary boundary layer (PBL) schemes and land surface models (LSMs) are investigated in a case study in western Germany during clear-sky weather conditions. The simulations were performed at 2 km resolution with two local and two nonlocal PBL schemes, combined with two LSMs (NOAH and NOAH-MP). Resulting convective boundary layer (CBL) features are investigated in combination with high-resolution water vapor differential absorption lidar measurements at an experimental area. Further, the simulated soil-vegetation-atmosphere feedback processes are quantified applying a mixing diagram approach. The investigation shows that the nonlocal PBL schemes simulate a deeper and drier CBL than the local schemes. Furthermore, the application of different LSMs reveals that the entrainment of dry air depends on the energy partitioning at the land surface. The study demonstrates that the impact of processes occurring at the land surface is not constrained to the lower CBL but extends up to the interfacial layer and the lower troposphere. With respect to the choice of the LSM, the discrepancies in simulating a diurnal change of the humidity profiles are even more significant at the interfacial layer than close to the land surface. This indicates that the representation of land surface processes has a significant impact on the simulation of mixing properties within the CBL.

  6. Ground-based differential absorption lidar for water-vapor profiling: assessment of accuracy, resolution, and meteorological applications.

    PubMed

    Wulfmeyer, V; Bösenberg, J

    1998-06-20

    The accuracy and the resolution of water-vapor measurements by use of the ground-based differential absorption lidar (DIAL) system of the Max-Planck-Institute (MPI) are determined. A theoretical analysis, intercomparisons with radiosondes, and measurements in high-altitude clouds allow the conclusion that, with the MPI DIAL system, water-vapor measurements with a systematic error of <5% in the whole troposphere can be performed. Special emphasis is laid on the outstanding daytime and nighttime performance of the DIAL system in the lower troposphere. With a time resolution of 1 min the statistical error varies between 0.05 g/m(3) in the near range using 75 m and-depending on the meteorological conditions-approximately 0.25 g/m(3) at 2 km using 150-m vertical resolution. When the eddy correlation method is applied, this accuracy and resolution are sufficient to determine water-vapor flux profiles in the convective boundary layer with a statistical error of <10% in each data point to approximately 1700 m. The results have contributed to the fact that the DIAL method has finally won recognition as an excellent tool for tropospheric research, in particular for boundary layer research and as a calibration standard for radiosondes and satellites. PMID:18273352

  7. Ground-based differential absorption lidar for water-vapor profiling: assessment of accuracy, resolution, and meteorological applications.

    PubMed

    Wulfmeyer, V; Bösenberg, J

    1998-06-20

    The accuracy and the resolution of water-vapor measurements by use of the ground-based differential absorption lidar (DIAL) system of the Max-Planck-Institute (MPI) are determined. A theoretical analysis, intercomparisons with radiosondes, and measurements in high-altitude clouds allow the conclusion that, with the MPI DIAL system, water-vapor measurements with a systematic error of <5% in the whole troposphere can be performed. Special emphasis is laid on the outstanding daytime and nighttime performance of the DIAL system in the lower troposphere. With a time resolution of 1 min the statistical error varies between 0.05 g/m(3) in the near range using 75 m and-depending on the meteorological conditions-approximately 0.25 g/m(3) at 2 km using 150-m vertical resolution. When the eddy correlation method is applied, this accuracy and resolution are sufficient to determine water-vapor flux profiles in the convective boundary layer with a statistical error of <10% in each data point to approximately 1700 m. The results have contributed to the fact that the DIAL method has finally won recognition as an excellent tool for tropospheric research, in particular for boundary layer research and as a calibration standard for radiosondes and satellites.

  8. Wave optics simulation of atmospheric turbulence and reflective speckle effects in CO{sub 2} differential absorption LIDAR (DIAL)

    SciTech Connect

    Nelson, D.H.; Petrin, R.R.; MacKerrow, E.P.; Schmitt, M.J.; Quick, C.R.; Zardecki, A.; Porch, W.M.; Whitehead, M.; Walters, D.L.

    1998-09-01

    The measurement sensitivity of CO{sub 2} differential absorption LIDAR (DIAL) can be affected by a number of different processes. The authors address the interaction of two of these processes: effects due to beam propagation through atmospheric turbulence and effects due to reflective speckle. Atmospheric turbulence affects the beam distribution of energy and phase on target. These effects include beam spreading, beam wander and scintillation which can result in increased shot-to-shot signal noise. In addition, reflective speckle alone has a major impact on the sensitivity of CO{sub 2} DIAL. The interaction of atmospheric turbulence and reflective speckle is of great importance in the performance of a DIAL system. A Huygens-Fresnel wave optics propagation code has previously been developed at the Naval Postgraduate School that models the effects of atmospheric turbulence as propagation through a series of phase screens with appropriate atmospheric statistical characteristics. This code has been modified to include the effects of reflective speckle. The performance of this modified code with respect to the combined effects of atmospheric turbulence and reflective speckle is examined. Results are compared with a combination of experimental data and analytical models.

  9. Modeling of Direct Detection Doppler Wind Lidar. II. The Fringe Imaging Technique.

    PubMed

    McKay, J A

    1998-09-20

    A simple analytic model is developed for the shot-noise-limited measurement precision of Doppler wind lidars based on the fringe imaging technique by use of either molecular or aerosol atmospheric backscatter. The model leads to etalon design parameters for an instrument optimized for precision. The ultimate measurement precision possible is two to four times the limit for a perfect, lossless receiver. The corresponding result for the double-edge Doppler analyzer was a ratio of 2.5, showing that the two methods are little different in this respect. For aerosol backscatter instruments, the wind speed dynamic range of the fringe imager is substantially greater than that for the edge detector. The etalon aperture needed to meet system etendue requirements is derived and shown to be approximately half that of each of the two etalons required by the double-edge technique. A comparison with more detailed modeling of fringe imaging Doppler-shift analyzers shows good agreement for the Rayleigh model and fair for the aerosol version, confirming the validity of this simpler technique for analyzer design and performance prediction. PMID:18286156

  10. A lidar technique to quantify surface deposition from atmospheric releases of bulk liquids

    NASA Astrophysics Data System (ADS)

    Post, Madison J.; Glaes, Thomas; Matta, Joseph; Sommerville, Douglas; Einfeld, Wayne

    We show that a scanning, pulsed lidar can be used to quantify the time history and areal concentration of mass deposited on the ground from an elevated release of bulk liquid. Aircraft measurements, witness car depositions and evaporative modelling crudely support results from analysed lidar data.

  11. The use of lidar for stratospheric measurements

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.

    1977-01-01

    Stratospheric measurements possible with ground-based, airborne, and satellite-borne lidar systems are reviewed. The instruments, basic equations, and formats normally used for various scattering and absorption phenomena measurements are presented including a discussion of elastic, resonance, Raman, and fluorescence scattering techniques.

  12. Column CO2 Measurement From an Airborne Solid-State Double-Pulsed 2-Micron Integrated Path Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Singh, U. N.; Yu, J.; Petros, M.; Refaat, T. F.; Remus, R.; Fay, J.; Reithmaier, K.

    2014-01-01

    NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micrometers IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

  13. Research of inverse synthetic aperture imaging lidar based on filtered back-projection tomography technique

    NASA Astrophysics Data System (ADS)

    Liu, Zhi-chao; Yang, Jin-hua

    2014-07-01

    In order to obtain clear two-dimensional image under the conditions without using heterodyne interferometry by inverse synthetic aperture lidar(ISAL), designed imaging algorithms based on filtered back projection tomography technique, and the target "A" was reconstructed with simulation algorithm by the system in the turntable model. Analyzed the working process of ISAL, and the function of the reconstructed image was given. Detail analysis of the physical meaning of the various parameters in the process of echo data, and its parameters affect the reconstructed image. The image in test area was reconstructed by the one-dimensional distance information with filtered back projection tomography technique. When the measured target rotated, the sum of the echo light intensity at the same distance was constituted by the different position of the measured target. When the total amount collected is large enough, multiple equations can be solved change. Filtered back-projection image of the ideal image is obtained through MATLAB simulation, and analyzed that the angle intervals affected the reconstruction of image. The ratio of the intensity of echo light and loss light affected the reconstruction of image was analyzed. Simulation results show that, when the sampling angle is smaller, the resolution of the reconstructed image of measured target is higher. And the ratio of the intensity of echo light and loss light is greater, the resolution of the reconstructed image of measured target is higher. In conclusion after some data processing, the reconstructed image basically meets be effective identification requirements.

  14. Turbulent Humidity Fluctuations in the Convective Boundary Layer: Case Studies Using Water Vapour Differential Absorption Lidar Measurements

    NASA Astrophysics Data System (ADS)

    Muppa, Shravan Kumar; Behrendt, Andreas; Späth, Florian; Wulfmeyer, Volker; Metzendorf, Simon; Riede, Andrea

    2016-01-01

    Turbulent humidity fluctuations in the convective boundary layer (CBL) under clear-sky conditions were investigated by deriving moments up to fourth-order. High-resolution humidity measurements were collected with a water vapour differential absorption lidar system during the HD(CP)}2 Observational Prototype Experiment (HOPE). Two cases, both representing a well-developed CBL around local noon, are discussed. While the first case (from the intensive observation period (IOP) 5 on 20 April 2013) compares well with what is considered typical CBL behaviour, the second case (from IOP 6 on 24 April 2013) shows a number of non-typical characteristics. Both cases show similar capping inversions and wind shear across the CBL top. However, a major difference between both cases is the advection of a humid layer above the CBL top during IOP 6. While the variance profile of IOP 5 shows a maximum at the interfacial layer, two variance peaks are observed near the CBL top for IOP 6. A marked difference can also be seen in the third-order moment and skewness profiles: while both are negative (positive) below (above) the CBL top for IOP 5, the structure is more complex for IOP 6. Kurtosis is about three for IOP 5, whereas for IOP 6, the distribution is slightly platykurtic. We believe that the entrainment of an elevated moist layer into the CBL is responsible for the unusual findings for IOP 6, which suggests that it is important to consider the structure of residual humidity layers entrained into the CBL.

  15. Acousto-optic filtering of lidar signals

    NASA Technical Reports Server (NTRS)

    Kolarov, G.; Deleva, A.; Mitsev, TS.

    1992-01-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  16. Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

    2016-05-20

    Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO2) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO2 strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO2 remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO2 column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO2 differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO2 weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and

  17. Double-pulse 2-μm integrated path differential absorption lidar airborne validation for atmospheric carbon dioxide measurement.

    PubMed

    Refaat, Tamer F; Singh, Upendra N; Yu, Jirong; Petros, Mulugeta; Remus, Ruben; Ismail, Syed

    2016-05-20

    Field experiments were conducted to test and evaluate the initial atmospheric carbon dioxide (CO2) measurement capability of airborne, high-energy, double-pulsed, 2-μm integrated path differential absorption (IPDA) lidar. This IPDA was designed, integrated, and operated at the NASA Langley Research Center on-board the NASA B-200 aircraft. The IPDA was tuned to the CO2 strong absorption line at 2050.9670 nm, which is the optimum for lower tropospheric weighted column measurements. Flights were conducted over land and ocean under different conditions. The first validation experiments of the IPDA for atmospheric CO2 remote sensing, focusing on low surface reflectivity oceanic surface returns during full day background conditions, are presented. In these experiments, the IPDA measurements were validated by comparison to airborne flask air-sampling measurements conducted by the NOAA Earth System Research Laboratory. IPDA performance modeling was conducted to evaluate measurement sensitivity and bias errors. The IPDA signals and their variation with altitude compare well with predicted model results. In addition, off-off-line testing was conducted, with fixed instrument settings, to evaluate the IPDA systematic and random errors. Analysis shows an altitude-independent differential optical depth offset of 0.0769. Optical depth measurement uncertainty of 0.0918 compares well with the predicted value of 0.0761. IPDA CO2 column measurement compares well with model-driven, near-simultaneous air-sampling measurements from the NOAA aircraft at different altitudes. With a 10-s shot average, CO2 differential optical depth measurement of 1.0054±0.0103 was retrieved from a 6-km altitude and a 4-GHz on-line operation. As compared to CO2 weighted-average column dry-air volume mixing ratio of 404.08 ppm, derived from air sampling, IPDA measurement resulted in a value of 405.22±4.15  ppm with 1.02% uncertainty and

  18. Gain control of photomultiplier tubes used in detecting differential absorption lidar returns

    NASA Technical Reports Server (NTRS)

    Allen, Robert J. (Inventor)

    1989-01-01

    A technique for controlling the gain of a photomultiplier tube (PMT) 20. A voltage divider (resistors 45-49 in FIG. 1 and zener diodes 60-65 in FIG. 3) is used to control the potentials on dynodes 5, 7, and 9 of PMT 20. Transistor switches 53 and 58 provide the control of the voltage divider in FIG. 1 and photodiodes 66, 67 and 70 provide the control in FIG. 3. The gain control of PMT 20 is in the range from 100% to less than 0.001% (100,000 to 1).

  19. Pseudorandom Noise Code-Based Technique for Thin Cloud Discrimination with CO2 and O2 Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Prasad, Narasimha S.; Flood, Michael A.

    2011-01-01

    NASA Langley Research Center is working on a continuous wave (CW) laser based remote sensing scheme for the detection of CO2 and O2 from space based platforms suitable for ACTIVE SENSING OF CO2 EMISSIONS OVER NIGHTS, DAYS, AND SEASONS (ASCENDS) mission. ASCENDS is a future space-based mission to determine the global distribution of sources and sinks of atmospheric carbon dioxide (CO2). A unique, multi-frequency, intensity modulated CW (IMCW) laser absorption spectrometer (LAS) operating at 1.57 micron for CO2 sensing has been developed. Effective aerosol and cloud discrimination techniques are being investigated in order to determine concentration values with accuracies less than 0.3%. In this paper, we discuss the demonstration of a pseudo noise (PN) code based technique for cloud and aerosol discrimination applications. The possibility of using maximum length (ML)-sequences for range and absorption measurements is investigated. A simple model for accomplishing this objective is formulated, Proof-of-concept experiments carried out using SONAR based LIDAR simulator that was built using simple audio hardware provided promising results for extension into optical wavelengths.

  20. Application of modified Twomey techniques to invert lidar angular scatter and solar extinction data for determining aerosol size distributions

    NASA Technical Reports Server (NTRS)

    Herman, B. M.

    1977-01-01

    Polarization properties of the angularly scattered laser light from a volume of air are used to determine the size distribution of the aerosol particles within the volume by the use of appropriate inversion techniques. Similar techniques are employed to determine a mean size distribution of the particulates within a vertical column through the atmosphere from determinations of the aerosol optical depth as a function of wavelength. In both of these examples, a modification of an inversion technique originally described by Twomey has been employed. Details of this method are presented as well as results from actual measurements employing bistatic lidar and solar radiometer.

  1. Laser remote sensing techniques

    NASA Technical Reports Server (NTRS)

    Grant, William B.

    1987-01-01

    The properties and advantages of remote sensing lasers are discussed. The theory of nonresonant techniques, which is based on the lidar equation and elastic backscatter, and their applications to aerosol and meteorological parameters are examined. The characteristics and applications of the differential absorption lidar technique, the fluorescence technique, and Raman scattering are described. The use of a laser heterodyne radiometer and fiber optics for remote sensing is studied. Future developments in the field of remote sensing, in particular the improvement of laser sources, the fabrication of compact remote sensing instruments, and space-borne applications for lidar, are considered.

  2. Fine-measuring technique and application for sea surface wind by mobile Doppler wind lidar

    NASA Astrophysics Data System (ADS)

    Liu, Zhishen; Wang, Zhangjun; Wu, Songhua; Liu, Bingyi; Li, Zhigang; Zhang, Xin; Bi, Decang; Chen, Yubao; Li, Rongzhong; Yang, Yuqiang

    2009-06-01

    The Key Laboratory of Ocean Remote Sensing of the Ministry of Education of China, Ocean University of China, has developed the first mobile Doppler wind lidar in China. As an important component of meteorological services for the Good Luck Beijing 2007 Qingdao International Regatta, the mobile Doppler wind lidar was used to measure the sea surface wind (SSW) with 100 m*100 m spatial and 10-min temporal resolution in Qingdao from 15 to 23 August 2007. We present the results from two aspects of this campaign. First, the lidar was operated in the fixed-direction mode and compared to SSW simultaneously measured by a collocated buoy. Second, we present lidar wind measurements throughout the regatta and show good agreement with the match situation of the International Regatta. In addition, we present a case study, accounting for the observation of sailboats stopped by the headwind. With considerable data accumulated, we have shown that the mobile Doppler wind lidar can indeed provide near real-time SSW in support of the sailing games. The lidar has also provided meteorological services for the 2008 Olympic sailing games from 8 to 22 August and Paralympics Sailing Games from 8 to 13 September 2008 in Qingdao.

  3. Development of 1.6 microm continuous-wave modulation hard-target differential absorption lidar system for CO2 sensing.

    PubMed

    Kameyama, Shumpei; Imaki, Masaharu; Hirano, Yoshihito; Ueno, Shinichi; Kawakami, Shuji; Sakaizawa, Daisuke; Nakajima, Masakatsu

    2009-05-15

    We have demonstrated the 1.6 mum cw modulation hard-target differential absorption lidar system for CO(2) sensing. In this system, ON and OFF wavelength laser lights are intensity modulated with cw signals. Received lights of the two wavelengths from the hard target are discriminated by modulation frequencies in the electrical signal domain. The optical circuit is fiber based, and this makes the system compact and reliable. It is shown that a stable CO(2) concentration measurement corresponding to a fluctuation of 4 ppm (rms) (ppm is parts per million) has been achieved in 32 s measurement intervals and the 1 km path.

  4. Near Field Deformation of the Mw 6.0 24 August, 2014 South Napa Earthquake Estimated by Airborne Light Detection and Ranging (LiDAR) Change Detection Techniques

    NASA Astrophysics Data System (ADS)

    Lyda, A. W.; Zhang, X.; Glennie, C. L.; Hudnut, K. W.; Brooks, B. A.

    2015-12-01

    We examine surface deformation caused by the Mw 6.0 24 August, 2014 South Napa Earthquake using high-resolution pre and post event airborne LiDAR (Light Detection and Ranging) observations. Temporally spaced LiDAR surveys taken before and after an earthquake can provide decimeter-level, 3D near-field estimates of deformation. These near-field deformation estimates can help constrain fault slip and rheology of shallow seismogenic zones. We compare and contrast estimates of deformation obtained from pre and post-event LiDAR data sets of the 2014 South Napa Earthquake using two change detection techniques, Iterative Control Point (ICP) and Particle Image Velocimetry (PIV). The ICP algorithm has been and still is the primary technique for acquiring three dimensional deformations from airborne LiDAR data sets. It conducts a rigid registration of pre-event data points to post event data points via iteratively matching data points with the smallest Euclidian distances between data sets. PIV is a technique derived from fluid mechanics that measures the displacement of a particle between two images of known time. LiDAR points act as the particles within the point cloud images so that their movement represents the horizontal deformation of the surface. The results from these change detection techniques are presented and further analyzed for differences between the techniques, the effects of temporal spacing between LiDAR collections, and the use of permanent LiDAR scatterers to constrain deformation estimates. The airborne LiDAR results will also be compared with far field deformations from space based geodetic techniques (InSAR and GNSS) and field observations of surface displacement.

  5. Airborne Lidar measurements of the atmospheric pressure profile with tunable Alexandrite lasers

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Milrod, J.; Walden, H.

    1986-01-01

    The first remote measurements of the atmospheric pressure profile made from an airborne platform are described. The measurements utilize a differential absorption lidar and tunable solid state Alexandrite lasers. The pressure measurement technique uses a high resolution oxygen A band where the absorption is highly pressure sensitive due to collision broadening. Absorption troughs and regions of minimum absorption were used between pairs of stongly absorption lines for these measurements. The trough technique allows the measurement to be greatly desensitized to the effects of laser frequency instabilities. The lidar system was set up to measure pressure with the on-line laser tuned to the absorption trough at 13147.3/cm and with the reference laser tuned to a nonabsorbing frequency near 13170.0/cm. The lidar signal returns were sampled with a 200 range gate (30 vertical resoltion) and averaged over 100 shots.

  6. Huygens-Fresnel Wave-Optics Simulation of Atmosphere Optical Turbulence and Reflective Speckle in CO{sub 2} Differential Absorption Lidar (DIAL)

    SciTech Connect

    Nelson, D.H.; Petrin, R.R.; MacKerrow, E.P.; Schmitt, M.J.; Foy, B.R.; Koskelo, A.C.; McVey, B.D.; Quick, C.R.; Porch, W.M.; Tiee, J.J.; Fite, C.B.; Archuleta, F.A.; Whitehead, M.C.; Walters, D.L.

    1999-03-23

    The measurement sensitivity of CO{sub 2} differential absorption lidar (DIAL) can be affected by a number of different processes. We have previously developed a Huygens-Fresnel wave optics propagation code to simulate the effects of two of these process: effects caused by beam propagation through atmospheric optical turbulence and effects caused by reflective speckle. Atmospheric optical turbulence affects the beam distribution of energy and phase on target. These effects include beam spreading, beam wander and scintillation which can result in increased shot-to-shot signal noise. In addition, reflective speckle alone has been shown to have a major impact on the sensitivity of CO{sub 2} DIAL. However, in real DIAL systems it is a combination of these phenomena, the interaction of atmospheric optical turbulence and reflective speckle, that influences the results. In this work, we briefly review a description of our model including the limitations along with previous simulation s of individual effects. The performance of our modified code with respect to experimental measurements affected by atmospheric optical turbulence and reflective speckle is examined. The results of computer simulations are directly compared with lidar measurements and show good agreement. In addition, advanced studies have been performed to demonstrate the utility of our model in assessing the effects for different lidar geometries on RMS noise and correlation ''size'' in the receiver plane.

  7. Speckle Reduction for LIDAR Using Optical Phase Conjugation

    SciTech Connect

    Bowers, M W; Kecy, C; Little, L; Cooke, J; Benterou, J; Boyd, R; Birks, T

    2001-02-26

    Remote detection of chemicals using LIDAR (Light Detection and Ranging) utilizing DIAL (Differential Absorption LIDAR) is now a standard detection technique for both military and civilian activities. We have developed a novel nonlinear optical phase conjugation system that can reduce the effects of speckle noise and atmospheric turbulence on DIAL remote detection systems. We have shown numerically and experimentally that it is possible to increase the signal-to-noise (S/N) ratio for LIDAR systems under certain conditions using optical phase conjugation. This increase in S/N can result in more accurate detection of chemical effluents while simultaneously reducing the time necessary to acquire this information.

  8. Measurement of the absorption coefficient using the sound-intensity technique

    NASA Technical Reports Server (NTRS)

    Atwal, M.; Bernhard, R.

    1984-01-01

    The possibility of using the sound intensity technique to measure the absorption coefficient of a material is investigated. This technique measures the absorption coefficient by measuring the intensity incident on the sample and the net intensity reflected by the sample. Results obtained by this technique are compared with the standard techniques of measuring the change in the reverberation time and the standing wave ratio in a tube, thereby, calculating the random incident and the normal incident adsorption coefficient.

  9. Standards - An Important Step for the (Public) Use of Lidars

    NASA Astrophysics Data System (ADS)

    Althausen, Dietrich; Emeis, Stefan; Flentje, Harald; Guttenberger, Josef; Jäckel, Simon; Lehmann, Volker; Mattis, Ina; Münkel, Christoph; Peters, Gerhard; Ritter, Christoph; Wiegner, Matthias; Wille, Holger

    2016-06-01

    Lidar standards are needed to ensure quality and lidar product control at the interface between lidar manufacturers and lidar users. Meanwhile three lidar standards have been published by German and international standardization organizations. This paper describes the cooperation between the lidar technique inventors, lidar instrument constructors, and lidar product users to establish useful standards. Presently a backscatter lidar standard is elaborated in Germany. Key points of this standard are presented here. Two German standards were already accepted as international standards by the International Organization for Standardization (ISO). Hence, German and international organizations for the establishment of lidar standards are introduced to encourage a cooperative work on lidar standards by lidar scientists.

  10. Semi-Empirical Validation of the Cross-Band Relative Absorption Technique for the Measurement of Molecular Mixing Ratios

    NASA Technical Reports Server (NTRS)

    Pliutau, Denis; Prasad, Narasimha S

    2013-01-01

    Studies were performed to carry out semi-empirical validation of a new measurement approach we propose for molecular mixing ratios determination. The approach is based on relative measurements in bands of O2 and other molecules and as such may be best described as cross band relative absorption (CoBRA). . The current validation studies rely upon well verified and established theoretical and experimental databases, satellite data assimilations and modeling codes such as HITRAN, line-by-line radiative transfer model (LBLRTM), and the modern-era retrospective analysis for research and applications (MERRA). The approach holds promise for atmospheric mixing ratio measurements of CO2 and a variety of other molecules currently under investigation for several future satellite lidar missions. One of the advantages of the method is a significant reduction of the temperature sensitivity uncertainties which is illustrated with application to the ASCENDS mission for the measurement of CO2 mixing ratios (XCO2). Additional advantages of the method include the possibility to closely match cross-band weighting function combinations which is harder to achieve using conventional differential absorption techniques and the potential for additional corrections for water vapor and other interferences without using the data from numerical weather prediction (NWP) models.

  11. Design and simulation of a biconic multipass absorption cell for the frequency stabilization of the reference seeder laser in IPDA lidar.

    PubMed

    Mu, Yongji; Du, Juan; Yang, Zhongguo; Sun, Yanguang; Liu, Jiqiao; Hou, Xia; Chen, Weibiao

    2016-09-01

    The design process and simulation method of a multipass absorption cell used for the frequency stabilization of the reference seeder laser in integrated path differential absorption (IPDA) lidar are presented. On the basis of the fundamental theory of the Herriott multipass cell comprising two spherical mirrors, the initial parameters of the multipass cell, which has an optical path greater than 10 m and consists of two biconic mirrors, were calculated. More than 30 light spots were distributed on each mirror, and the distance between adjacent spots was mostly optimized to greater than six times the beam waist. After optimization, the simulated transmittance spectrum and associated differential signal were obtained. The interference induced by surface scattering was also simulated, and its influence on the differential signal was analyzed. A correspondence between the simulated results and the testing data was observed. PMID:27607288

  12. Development of 3.0-3.45 μm OPO laser based range resolved and hard-target differential absorption lidar for sensing of atmospheric methane

    NASA Astrophysics Data System (ADS)

    Veerabuthiran, S.; Razdan, A. K.; Jindal, M. K.; Sharma, R. K.; Sagar, Vikas

    2015-10-01

    We have developed a tripod mounted 3.0-3.45 μm OPO laser based differential absorption lidar (DIAL) system for sensing of atmospheric methane. The system operates with Nd: YAG laser pumped OPO laser, a 20 cm aperture telescope and a pan-tilt system to scan the atmosphere. Atmospheric transmission spectra over the entire spectral region are measured and indentified the absorption region of the various molecules in comparison with HITRAN. The backscattered signal for range resolved and hard target configuration up to a range of 400 m are measured with range resolution of 15 m. The stable daytime measurements of methane concentration varied from 1.9 ppm to 2.4 ppm with rms deviation of 0.2 ppm have been achieved. The measured concentration is in good agreement with reported values.

  13. Partial-transfer absorption imaging: a versatile technique for optimal imaging of ultracold gases.

    PubMed

    Ramanathan, Anand; Muniz, Sérgio R; Wright, Kevin C; Anderson, Russell P; Phillips, William D; Helmerson, Kristian; Campbell, Gretchen K

    2012-08-01

    Partial-transfer absorption imaging is a tool that enables optimal imaging of atomic clouds for a wide range of optical depths. In contrast to standard absorption imaging, the technique can be minimally destructive and can be used to obtain multiple successive images of the same sample. The technique involves transferring a small fraction of the sample from an initial internal atomic state to an auxiliary state and subsequently imaging that fraction absorptively on a cycling transition. The atoms remaining in the initial state are essentially unaffected. We demonstrate the technique, discuss its applicability, and compare its performance as a minimally destructive technique to that of phase-contrast imaging.

  14. Raman Lidar Measurements during the International HZO Project. 1; Instrumentation and Analysis Techniques, Popular Summary

    NASA Technical Reports Server (NTRS)

    Whiteman, D. N.; Demoz, B.; DiGirolamo, P.; Comer, J.; Veselovskii, I.; Evans, K.; Wang, Z.; Cadirola, M.; Rush, K.; Schwemmer, G.; Gentry, B.

    2005-01-01

    The amount of water vapor in the atmosphere helps to determine the likelihood that severe storms may develop. The concentration of water vapor, though, is highly variable in space and time. And yet small changes in water vapor concentration over a short period of time or over a short spatial distance can determine whether a storm may or may not develop. Therefore, in order to improve the ability to forecast severe weather such as thunderstorms it is important to measure water vapor in the atmosphere with high spatial and temporal resolution. One of the most attractive research tools for measuring water vapor in the atmosphere with high spatial and temporal resolution is a Raman lidar. A Raman lidar consists of a laser transmitter, a telescope receiver and optics and electronics for processing opticand electronic signals. A laser pulse is emitted into the atmosphere and it interacts with molecules in the atmosphere causing them to become excited and to emit, through the Raman process, photons of different wavelength than emitted by the laser. The molecule that emitted these emitted. This is the way that a Raman lidar identifies water vapor molecules in the atmosphere. can be identified based on the wavelength of the photons One of the great challenges in Raman lidar measurements has been to make useful daytime measurements of the water vapor profile under bright daytime conditions. In this first of two papers, we describe the instrumentation and analysis of the first documented Raman lidar that is able to measure water vapor in the daytime with sufficient quality to permit the study of developing storm systems.

  15. Diode laser absorption tomography using data compression techniques

    NASA Astrophysics Data System (ADS)

    Lindstrom, Chad; Tam, Chung-Jen; Givens, Ryan; Davis, Doug; Williams, Skip

    2008-02-01

    Tunable diode laser absorption spectroscopy (TDLAS) shows promise for in situ monitoring in high-speed flows. However, the dynamic nature of typical flows of supersonic combustors, gas turbine engines and augmenters can also lead to inhomogenities that cannot be captured by a single line-of-sight TDLAS measurement. Instead, multiple measurements varied over several spatial locations need to be made. In the current study, shock train structure in the isolator section of the Research Cell 18 supersonic combustion facility at Wright-Patterson AFB is measured. Although only two view angles are available for measurement, multiple absorption features along with a priori computational fluid dynamics (CFD) simulations enable estimates of two dimensional flow features to be formed. Vector quantization/kmeans data clustering is used to identify key flow features from the temporal history of the raw sinograms. Through the use of multiple absorption features that are measured nearly simultaneously, an approximate two-dimensional image can be formed. This image can be further refined through the use of an optimal set of basis functions that can be derived from a set of CFD simulations that describes the flow shapes.

  16. Intensity-modulated linear-frequency-modulated continuous-wave lidar for distributed media: fundamentals of technique.

    PubMed

    Batet, Oscar; Dios, Federico; Comeron, Adolfo; Agishev, Ravil

    2010-06-10

    We analyze the intensity-modulation frequency-modulated continuous-wave (FMCW) technique for lidar remote sensing in the context of its application to distributed media. The goal of the technique is the reproduction of the sounded-medium profile along the emission path. A conceptual analysis is carried out to show the problems the basic version of the method presents for this application. The principal point is the appearance of a bandpass filtering effect, which seems to hinder its use in this context. A modified version of the technique is proposed to overcome this problem. A number of computer simulations confirm the ability of the modified FMCW technique to sound distributed media. PMID:20539357

  17. Development of an Airborne Triple-Pulse 2-Micron Integrated Path Differential Absorption Lidar (IPDA) for Simultaneous Airborne Column Measurements of Carbon Dioxide and Water Vapor in the Atmosphere

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Petros, Mulugeta; Refaat, Tamer F.; Yu, Jirong; Antill, Charles W.; Remus, Ruben

    2016-01-01

    This presentation will provide status and details of an airborne 2-micron triple-pulse integrated path differential absorption (IPDA) lidar being developed at NASA Langley Research Center with support from NASA ESTO Instrument Incubator Program. The development of this active optical remote sensing IPDA instrument is targeted for measuring both atmospheric carbon dioxide and water vapor in the atmosphere from an airborne platform. This presentation will focus on the advancement of the 2-micron triple-pulse IPDA lidar development. Updates on the state-of-the-art triple-pulse laser transmitter will be presented including the status of seed laser locking, wavelength control, receiver and detector upgrades, laser packaging and lidar integration. Future plan for IPDA lidar system for ground integration, testing and flight validation will also be presented.

  18. Retrieval of Spatio-temporal Distributions of Particle Parameters from Multiwavelength Lidar Measurements Using the Linear Estimation Technique and Comparison with AERONET

    NASA Technical Reports Server (NTRS)

    Veselovskii, I.; Whiteman, D. N.; Korenskiy, M.; Kolgotin, A.; Dubovik, O.; Perez-Ramirez, D.; Suvorina, A.

    2013-01-01

    The results of the application of the linear estimation technique to multiwavelength Raman lidar measurements performed during the summer of 2011 in Greenbelt, MD, USA, are presented. We demonstrate that multiwavelength lidars are capable not only of providing vertical profiles of particle properties but also of revealing the spatio-temporal evolution of aerosol features. The nighttime 3 Beta + 1 alpha lidar measurements on 21 and 22 July were inverted to spatio-temporal distributions of particle microphysical parameters, such as volume, number density, effective radius and the complex refractive index. The particle volume and number density show strong variation during the night, while the effective radius remains approximately constant. The real part of the refractive index demonstrates a slight decreasing tendency in a region of enhanced extinction coefficient. The linear estimation retrievals are stable and provide time series of particle parameters as a function of height at 4 min resolution. AERONET observations are compared with multiwavelength lidar retrievals showing good agreement.

  19. Atmospheric aerosol and gas sensing using Scheimpflug lidar

    NASA Astrophysics Data System (ADS)

    Mei, Liang; Brydegaard, Mikkel

    2015-04-01

    This work presents a new lidar technique for atmospheric remote sensing based on Scheimpflug principle, which describes the relationship between nonparallel image- and object-planes[1]. When a laser beam is transmitted into the atmosphere, the implication is that the backscattering echo of the entire illuminated probe volume can be in focus simultaneously without diminishing the aperture. The range-resolved backscattering echo can be retrieved by using a tilted line scan or two-dimensional CCD/CMOS camera. Rather than employing nanosecond-pulsed lasers, cascade detectors, and MHz signal sampling, all of high cost and complexity, we have developed a robust and inexpensive atmospheric lidar system based on compact laser diodes and array detectors. We present initial applications of the Scheimpflug lidar for atmospheric aerosol monitoring in bright sunlight, with a 3 W, 808 nm CW laser diode. Kilohertz sampling rates are also achieved with applications for wind speed and entomology [2]. Further, a proof-of-principle demonstration of differential absorption lidar (DIAL) based on the Scheimpflug lidar technique is presented [3]. By utilizing a 30 mW narrow band CW laser diode emitting at around 760 nm, the detailed shape of an oxygen absorption line can be resolved remotely with an integration time of 6 s and measurement cycle of 1 minute during night time. The promising results demonstrated in this work show potential for the Scheimpflug lidar technique for remote atmospheric aerosol and gas sensing, and renews hope for robust and realistic instrumentation for atmospheric lidar sensing. [1] F. Blais, "Review of 20 years of range sensor development," Journal of Electronic Imaging, vol. 13, pp. 231-243, Jan 2004. [2] M. Brydegaard, A. Gebru, and S. Svanberg, "Super resolution laser radar with blinking atmospheric particles - application to interacting flying insects " Progress In Electromagnetics Research, vol. 147, pp. 141-151, 2014. [3] L. Mei and M. Brydegaard

  20. A Comparison of IM-CW Lidar Modulation Techniques for ASCENDS CO2 Column Measurements from Space

    NASA Astrophysics Data System (ADS)

    Campbell, Joel; Lin, Bing; Nehrir, Amin; Harrison, Fenton; Obland, Michael; Ismail, Syed

    2014-05-01

    Global atmospheric carbon dioxide (CO2) measurements through the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) Decadal Survey recommended space mission are critical for improving our understanding of CO2 sources and sinks. IM-CW (Intensity Modulated Continuous Wave) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS science requirements. In previous laboratory and flight experiments we have successfully used linear swept frequency modulation to discriminate surface lidar returns from intermediate aerosol and cloud contamination. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate clouds, which is a requirement for the inversion of the CO2 column-mixing ratio from the instrument optical depth measurements, has been demonstrated with the linear swept frequency modulation technique. We are concurrently investigating advanced techniques to help improve the auto-correlation properties of the transmitted waveform implemented through physical hardware to make cloud rejection more robust in special restricted scenarios. Several different carrier based modulation techniques are compared including orthogonal linear swept, orthogonal non-linear swept, and Binary Phase Shift Keying (BPSK). Techniques are investigated that reduce or eliminate sidelobes. These techniques have excellent auto-correlation properties while possessing a finite bandwidth (by way of a new cyclic digital filter), which will reduce bias error in the presence of multiple scatterers. Our analyses show that the studied modulation techniques can increase the accuracy of CO2 column measurements from space. A comparison of various properties such as signal to noise ratio (SNR) and time-bandwidth product are discussed.

  1. A Comparison of Potential IM-CW Lidar Modulation Techniques for ASCENDS CO2 Column Measurements From Space

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.; Harrison, F. Wallace; Obland, Michael D.; Ismail, Syed

    2014-01-01

    Global atmospheric carbon dioxide (CO2) measurements through the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) Decadal Survey recommended space mission are critical for improving our understanding of CO2 sources and sinks. IM-CW (Intensity Modulated Continuous Wave) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS science requirements. In previous laboratory and flight experiments we have successfully used linear swept frequency modulation to discriminate surface lidar returns from intermediate aerosol and cloud contamination. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate clouds, which is a requirement for the inversion of the CO2 column-mixing ratio from the instrument optical depth measurements, has been demonstrated with the linear swept frequency modulation technique. We are concurrently investigating advanced techniques to help improve the auto-correlation properties of the transmitted waveform implemented through physical hardware to make cloud rejection more robust in special restricted scenarios. Several different carrier based modulation techniques are compared including orthogonal linear swept, orthogonal non-linear swept, and Binary Phase Shift Keying (BPSK). Techniques are investigated that reduce or eliminate sidelobes. These techniques have excellent auto-correlation properties while possessing a finite bandwidth (by way of a new cyclic digital filter), which will reduce bias error in the presence of multiple scatterers. Our analyses show that the studied modulation techniques can increase the accuracy of CO2 column measurements from space. A comparison of various properties such as signal to noise ratio (SNR) and time-bandwidth product are discussed.

  2. Land-based lidar mapping: a new surveying technique to shed light on rapid topographic change

    USGS Publications Warehouse

    Collins, Brian D.; Kayen, Robert

    2006-01-01

    The rate of natural change in such dynamic environments as rivers and coastlines can sometimes overwhelm the monitoring capacity of conventional surveying methods. In response to this limitation, U.S. Geological Survey (USGS) scientists are pioneering new applications of light detection and ranging (lidar), a laser-based scanning technology that promises to greatly increase our ability to track rapid topographic changes and manage their impact on affected communities.

  3. Airborne Lidar Measurements of Atmospheric Pressure Made Using the Oxygen A-Band

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Rodriquez, Michael; Allan, Graham R.; Hasselbrack, William E.; Stephen, Mark A.; Abshire, James B.

    2011-01-01

    We report on airborne measurements of atmospheric pressure using a fiber-laser based lidar operating in the oxygen A-band near 765 nm and the integrated path differential absorption measurement technique. Our lidar uses fiber optic technology and non-linear optics to generate tunable laser radiation at 765 nm, which overlaps an absorption line pair in the Oxygen A-band. We use a pulsed time resolved technique, which rapidly steps the laser wavelength across the absorption line pair, a 20 cm telescope and photon counting detector to measure Oxygen concentrations.

  4. Wind observations above an urban river using a new lidar technique, scintillometry and anemometry.

    PubMed

    Wood, C R; Pauscher, L; Ward, H C; Kotthaus, S; Barlow, J F; Gouvea, M; Lane, S E; Grimmond, C S B

    2013-01-01

    Airflow along rivers might provide a key mechanism for ventilation in cities: important for air quality and thermal comfort. Airflow varies in space and time in the vicinity of rivers. Consequently, there is limited utility in point measurements. Ground-based remote sensing offers the opportunity to study 3D airflow in locations which are difficult to observe with conventional approaches. For three months in the winter and spring of 2011, the airflow above the River Thames in central London was observed using a scanning Doppler lidar, a scintillometer and sonic anemometers. First, an inter-comparison showed that lidar-derived mean wind-speed estimates compare almost as well to sonic anemometers (root-mean-square error (rmse) 0.65-0.68 ms(-1)) as comparisons between sonic anemometers (0.35-0.73 ms(-1)). Second, the lidar duo-beam operating strategy provided horizontal transects of wind vectors (comparison with scintillometer rmse 1.12-1.63 ms(-1)) which revealed mean and turbulent airflow across the river and surrounds; in particular, channelled airflow along the river and changes in turbulence quantities consistent with the roughness changes between built and river environments. The results have important consequences for air quality and dispersion around urban rivers, especially given that many cities have high traffic rates on roads located on riverbanks. PMID:23201607

  5. Phototransistors Development and their Applications to Lidar

    NASA Technical Reports Server (NTRS)

    Abedin, M. N.; Refaat, Tamer F.; Ismail, Syed; Singh, Upendra N.

    2007-01-01

    Custom-designed two-micron phototransistors have been developed using Liquid Phase Epitaxy (LPE), Molecular Beam Epitaxy (MBE) and Metal-Organic Chemical Vapor Deposition (MOCVD) techniques under Laser Risk Reduction Program (LRRP). The devices were characterized in the Detector Characterization Laboratory at NASA Langley Research Center. It appears that the performance of LPE- and MBE-grown phototransistors such as responsivity, noise-equivalent-power, and gain, are better than MOCVD-grown devices. Lidar tests have been conducted using LPE and MBE devices under the 2-micrometer CO2 Differential Absorption Lidar (DIAL) Instrument Incubator Program (IIP) at the National Center for Atmospheric Research (NCAR), Boulder, Colorado. The main focus of these tests was to examine the phototransistors performances as compared to commercial InGaAs avalanche photodiode by integrating them into the Raman-shifted Eye-safe Aerosol Lidar (REAL) operating at 1.543 micrometers. A simultaneous measurement of the atmospheric backscatter signals using the LPE phototransistors and the commercial APD demonstrated good agreement between these two devices. On the other hand, simultaneous detection of lidar backscatter signals using MBE-grown phototransistor and InGaAs APD, showed a general agreement between these two devices with a lower performance than LPE devices. These custom-built phototransistors were optimized for detection around 2-micrometer wavelength while the lidar tests were performed at 1.543 micrometers. Phototransistor operation at 2-micron will improve the performance of a lidar system operating at that wavelength. Measurements include detecting hard targets (Rocky Mountains), atmospheric structure consisting of cirrus clouds and boundary layer. These phototransistors may have potential for high sensitivity differential absorption lidar measurements of carbon dioxide and water vapor at 2.05-micrometers and 1.9-micrometers, respectively.

  6. Absorption measurement of thin films by using photothermal techniques: The influence of thermal properties

    SciTech Connect

    Wu, Z.L.; Kuo, P.K.; Thomas, R.L.; Fan, Z.X.

    1995-12-31

    Photothermal techniques are widely used for measuring optical absorption of thin film coatings. In these applications the calibration of photothermal signal is typically based on the assumption that the thermal properties of the thin film make very little contribution. In this paper we take mirage technique as an example and present a detailed analysis of the influence of thin film thermal properties on absorption measurements. The results show that the traditional calibration method is not valid on surprisingly many situations.

  7. Huygens-Fresnel wave-optics simulation of atmospheric optical turbulence and reflective speckle in CO{sub 2} differential absorption lidar (DIAL)

    SciTech Connect

    Nelson, D.; Petrin, R.; MacKerrow, E.; Schmitt, M.; Foy, B.; Koskelo, A.; McVey, B.; Quick, C.; Porch, W.; Fite, C.; Archuleta, F.; Whitehead, M.; Tiee, J.; Walters, D.

    1999-04-01

    The measurement sensitivity of CO{sub 2} differential absorption lidar (DIAL) can be affected by a number of different processes. The authors have previously developed a Huygens-Fresnel wave optics propagation code to simulate the effects of two of these processes: effects caused by beam propagation through atmospheric optical turbulence and effects caused by reflective speckle. Atmospheric optical turbulence affects the beam distribution of energy and phase on target. These effects include beam spreading, beam wander and scintillation which can result in increased shot-to-shot signal noise. In addition, reflective speckle alone has been shown to have a major impact on the sensitivity of CO{sub 2} DIAL. However, in real DIAL systems it is a combination of these phenomena, the interaction of atmospheric optical turbulence and reflective speckle, that influences the results. The performance of the modified code with respect to experimental measurements affected by atmospheric optical turbulence and reflective speckle is examined. The results of computer simulations are directly compared with lidar measurements. The limitations of the model are also discussed. In addition, studies have been performed to determine the importance of key parameters in the simulation. The results of these studies and their impact on the overall results will be presented.

  8. Space-Based Lidar Systems

    NASA Technical Reports Server (NTRS)

    Sun, Xiaoli

    2012-01-01

    An overview of space-based lidar systems is presented. from the first laser altimeter on APOLLO 15 mission in 1971 to the Mercury Laser Altimeter on MESSENGER mission currently in orbit, and those currently under development. Lidar, which stands for Light Detection And Ranging, is a powerful tool in remote sensing from space. Compared to radars, lidars operate at a much shorter wavelength with a much narrower beam and much smaller transmitter and receiver. Compared to passive remote sensing instruments. lidars carry their own light sources and can continue measuring day and night. and over polar regions. There are mainly two types of lidars depending on the types of measurements. lidars that are designed to measure the distance and properties of hard targets are often called laser rangers or laser altimeters. They are used to obtain the surface elevation and global shape of a planet from the laser pulse time-of-night and the spacecraft orbit position. lidars that are designed to measure the backscattering and absorption of a volume scatter, such as clouds and aerosols, are often just called lidars and categorized by their measurements. such as cloud and aerosol lidar, wind lidar, CO2 lidar, and so on. The advantages of space-based lidar systems over ground based lidars are the abilities of global coverage and continuous measurements.

  9. Assesment of dial data collection and analysis techniques

    NASA Technical Reports Server (NTRS)

    Browell, E. V.; Woods, P. T.

    1986-01-01

    The key issues in all areas of Differential Absorption Lidar (DIAL) data collection and analysis techniques were examined. This included consideration of the practical and theoretical limitations of DIAL and the range of possible DIAL measurements.

  10. Theory and operation of the real-time data acquisition system for the NASA-LaRC differential absorption lidar (DIAL)

    NASA Technical Reports Server (NTRS)

    Butler, C.

    1986-01-01

    The improvement of computer hardware and software of the NASA Multipurpose Differential Absorption Lidar (DIAL) system is documented. The NASA DIAL system is undergoing development and experimental deployment at NASA Langley Research Center for the remote measurement of atmospheric trace gas concentrations from ground and aircraft platforms. A viable DIAL system was developed capable of remotely measuring O3 and H2O concentrations from an aircraft platform. Test flights of the DIAL system were successfully performed onboard the NASA Goddard Flight Center Electra aircraft from 1980 to 1985. The DIAL Data Acquisition System has undergone a number of improvements over the past few years. These improvements have now been field tested. The theory behind a real time computer system as it applies to the needs of the DIAL system is discussed. This report is designed to be used as an operational manual for the DIAL DAS.

  11. Theory and operation of the real-time data acquisition system for the NASA-LaRC differential absorption lidar (DIAL)

    NASA Technical Reports Server (NTRS)

    Butler, Carolyn; Spencer, Randall

    1988-01-01

    The improvement of computer hardware and software of the NASA Multipurpose Differential Absorption Lidar (DIAL) system is documented. The NASA DIAL system has undergone development and experimental deployment at NASA/Langley Res. Center for the remote measurement of atmospheric trace gas concentrations from ground and aircraft platforms. A viable DIAL system was developed capable of remotely measuring O3 and H2O concentrations from an aircraft platform. The DIAL Data Acquisition System (DAS) has undergone a number of improvements also. Due to the participation of the DIAL in the Global Tropospheric Experiment, modifications and improvements of the system were tested and used both in the lab and in air. Therefore, this is an operational manual for the DIAL DAS.

  12. Simultaneous and co-located wind measurements in the middle atmosphere by lidar and rocket-borne techniques

    NASA Astrophysics Data System (ADS)

    Lübken, Franz-Josef; Baumgarten, Gerd; Hildebrand, Jens; Schmidlin, Francis J.

    2016-08-01

    We present the first comparison of a new lidar technique to measure winds in the middle atmosphere, called DoRIS (Doppler Rayleigh Iodine Spectrometer), with a rocket-borne in situ method, which relies on measuring the horizontal drift of a target ("starute") by a tracking radar. The launches took place from the Andøya Space Center (ASC), very close to the ALOMAR observatory (Arctic Lidar Observatory for Middle Atmosphere Research) at 69° N. DoRIS is part of a steerable twin lidar system installed at ALOMAR. The observations were made simultaneously and with a horizontal distance between the two lidar beams and the starute trajectories of typically 0-40 km only. DoRIS measured winds from 14 March 2015, 17:00 UTC, to 15 March 2015, 11:30 UTC. A total of eight starute flights were launched successfully from 14 March, 19:00 UTC, to 15 March, 00:19 UTC. In general there is excellent agreement between DoRIS and the in situ measurements, considering the combined range of uncertainties. This concerns not only the general height structures of zonal and meridional winds and their temporal developments, but also some wavy structures. Considering the comparison between all starute flights and all DoRIS observations in a time period of ±20 min around each individual starute flight, we arrive at mean differences of typically ±5-10 m s-1 for both wind components. Part of the remaining differences are most likely due to the detection of different wave fronts of gravity waves. There is no systematic difference between DoRIS and the in situ observations above 30 km. Below ˜ 30 km, winds from DoRIS are systematically too large by up to 10-20 m s-1, which can be explained by the presence of aerosols. This is proven by deriving the backscatter ratios at two different wavelengths. These ratios are larger than unity, which is an indication of the presence of aerosols.

  13. Tree Crown Delineation using Watershed Techniques and Forest Metrics from NEON LiDAR Data

    NASA Astrophysics Data System (ADS)

    Luong, K. Y.

    2014-12-01

    LiDAR is a powerful remote sensing tool allowing for forest metrics to be taken on varying scales, which ultimately provide important forestry variables used to calculate factors such as total biomass or leaf area index. These variables are most useful when calculated for individual trees throughout a stand, but in very dense forests, identifying single trees becomes more difficult by traditional means. Full forests can be quantified uniquely for the best understanding of ecological contributions as opposed to purely in situ tree inventories which are time consuming and extremely localized. Canopy height models (CHM) can be used to understand the forest as a whole. By inverting the CHM, the tree data becomes sinks in the ground, mimicking ponds; by applying watershed-related spatial analyst tools in ArcGIS and GrassGIS, the trees are delineated by makeshift "flooding." Within this algorithm, the crown peaks are also extracted as an intermediate step to delineation, but this is a reliable means to obtain an accurate number of trees, as well as their individual heights with high reliability (R2 = 0.87). Delineated tree polygons can be directly overlaid onto different rasters to get many forest variables. In tightly clustered and very sparse stands, this method of delineation has a high level of accuracy. Following the workflow studies conducted on NEON LiDAR data on the Soaproot Saddle site, a ground-truth comparison was made with the Teakettle Experimental Forest site due to the availability of tree inventory data.

  14. Advances in lidar applications

    NASA Astrophysics Data System (ADS)

    Lewandowski, Piotr Andrzej

    the lidar technique and also opens new capabilities for elastic lidar systems.

  15. Sound absorption by suspensions of nonspherical particles: measurements compared with predictions using various particle sizing techniques.

    PubMed

    Richards, Simon D; Leighton, Timothy G; Brown, Niven R

    2003-10-01

    Knowledge of the particle size distribution is required in order to predict ultrasonic absorption in polydisperse particulate suspensions. This paper shows that the method used to measure the particle size distribution can lead to important differences in the predicted absorption. A reverberation technique developed for measuring ultrasonic absorption by suspended particles is used to measure the absorption in suspensions of nonspherical particles. Two types of particulates are studied: (i) kaolin (china clay) particles which are platelike in form; and (ii) calcium carbonate particles which are more granular. Results are compared to theoretical predictions of visco-inertial absorption by suspensions of spherical particles. The particle size distributions, which are required for these predictions, are measured by laser diffraction, gravitational sedimentation and centrifugal sedimentation, all of which assume spherical particles. For a given sample, each sizing technique yields a different size distribution, leading to differences in the predicted absorption. The particle size distributions obtained by gravitational and centrifugal sedimentation are reinterpreted to yield a representative size distribution of oblate spheroids, and predictions for absorption by these spheroids are compared with the measurements. Good agreement between theory and measurement for the flat kaolin particles is obtained, demonstrating that these particles can be adequately represented by oblate spheroids. PMID:14587585

  16. Application of Optical Parametric Generator for Lidar Sensing of Minor Gas Components of the Atmosphere in 3-4 μm Spectral Range

    NASA Astrophysics Data System (ADS)

    Romanovskii, O. A.; Sadovnikov, S. A.; Kharchenko, O. V.; Shumskii, V. K.; Yakovlev, S. V.

    2016-07-01

    Possibility of application of a laser system with parametric light generation based on a nonlinear KTA crystal for lidar sensing of the atmosphere in the 3-4 μm spectral range is investigated. A technique for lidar measurements of gas components in the atmosphere with the use of differential absorption lidar (DIAL) and differential optical absorption spectroscopy (DOAS) method is developed. The DIAL-DOAS technique is tested for estimating the possibility of laser sensing of minor gas components in the atmosphere.

  17. Techniques for inferring terrain parameters related to ground vehicle mobility using UAV born IFSAR and lidar data

    NASA Astrophysics Data System (ADS)

    Durst, Phillip J.; Baylot, Alex; McKinley, Burney

    2011-05-01

    Predicting ground vehicle performance requires in-depth knowledge, captured as numeric parameters, of the terrain on which the vehicles will be operating. For off-road performance, predictions are based on rough terrain ride comfort, which is described using a parameter entitled root-mean-square (RMS) surface roughness. Likewise, on-road vehicle performance depends heavily on the slopes of the individual road segments. Traditional methods of computing RMS and road slope values call for high-resolution (inch-scale) surface elevation data. At this scale, surface elevation data is both difficult and time consuming to collect. Nevertheless, a current need exists to attribute large geographic areas with RMS and road slope values in order to better support vehicle mobility predictions, and high-resolution surface data is neither available nor collectible for many of these regions. On the other hand, meter scale data can be quickly and easily collected for these areas using unmanned aerial vehicle (UAV) based IFSAR and LIDAR sensors. A statistical technique for inferring RMS values for large areas using a combination of fractal dimension and spectral analysis of five-meter elevation data is presented. Validation of the RMS prediction technique was based on 43 vehicle ride courses with 30-centimeter surface elevation data. Also presented is a model for classifying road slopes for long road sections using five-meter elevation data. The road slope model was validated against one-meter LIDAR surface elevation profiles. These inference algorithms have been successfully implemented for regions of northern Afghanistan, and some initial results are presented.

  18. Study of target tracking techniques based on non-scanning imaging lidar

    NASA Astrophysics Data System (ADS)

    Chen, Sui; Wang, Qianqian; Zhang, Shuhao; Shan, Bin; Li, Xiaoyang; Peng, Zhong

    2015-08-01

    Non-scanning imaging lidar, as a sensor, is applied in target tracking system to acquire distance image, intensity image and amplitude image, which makes it possible to achieve information fusion of the target. This system applies ARM as a hardware development platform which makes it easy to carry and achieve the system miniaturization. Target characteristics are extracted by the method combines codebook model and connected domain denoising to improve the accuracy of target characteristics extraction. Qt/Embedded development platform applied in building graphical user interface has a good architecture and programming mode which improves man-machine interaction and control efficiency. The results show the high accuracy of the target tracking, excellent man-machine interaction and perfect interface functions of the designed system.

  19. Improved time-of-flight range acquisition technique in underwater lidar experiments.

    PubMed

    Cheng, Zao; Yang, Kecheng; Han, Jiefei; Zhou, Yiyu; Sun, Liying; Li, Wei; Xia, Min

    2015-06-20

    This paper presents an underwater lidar time-of-flight ranging system that combines the variable forgivable factor recursive least-squares (VFF-RLS) adaptive filter algorithm and the constant fraction discriminator (CFD) timing technology. The effectiveness of suppressing the backscattering and increasing timing accuracy is experimentally verified in the water basin under the different target distances, especially near the detection limit. The classical RLS is creatively transformed by introducing the VFF, which is highly correlated to the target echo at any distance. The improvement of the signal-to-backscatter ratio always exceeds 18.9 dB. The Monte Carlo simulation proves the applicability of the proposed method in the media of different turbidity. The influences of the selective timing methods on the walk error and time jitter are compared, and the optimum zero point of CFD is achieved by the slope analysis of leading (falling) edge in experimental target pulses. PMID:26193020

  20. Orbiting lidar simulations. I - Aerosol and cloud measurements by an independent-wavelength technique

    NASA Technical Reports Server (NTRS)

    Russell, P. B.; Morley, B. M.; Livingston, J. M.; Grams, G. W.; Patterson, E. M.

    1982-01-01

    Aerosol and cloud measurements have been simulated for a Space Shuttle lidar. Expected errors - in signal, transmission, density, and calibration - are calculated algebraically and checked by simulating measurements and retrievals using random-number generators. By day, vertical structure is retrieved for tenuous clouds, Saharan aerosols, and boundary layer aerosols (at 0.53 and 1.06 micron) as well as strong volcanic stratospheric aerosols (at 0.53 micron). By night, all these constituents are retrieved plus upper tropospheric and stratospheric aerosols (at 1.06 micron), mesospheric aerosols (at 0.53 micron), and noctilucent clouds (at 1.06 and 0.53 micron). The vertical resolution was 0.1-0.5 km in the troposphere, 0.5-2.0 km above, except 0.25-1.0 km in the mesospheric cloud and aerosol layers; horizontal resolution was 100-2000 km.

  1. A New Raman Water Vapor Lidar Calibration Technique and Measurements in the Vicinity of Hurricane Bonnie

    NASA Technical Reports Server (NTRS)

    Evans, Keith D.; Demoz, Belay B.; Cadirola, Martin P.; Melfi, S. H.; Whiteman, David N.; Schwemmer, Geary K.; Starr, David OC.; Schmidlin, F. J.; Feltz, Wayne

    2000-01-01

    The NAcA/Goddard Space Flight Center Scanning Raman Lidar has made measurements of water vapor and aerosols for almost ten years. Calibration of the water vapor data has typically been performed by comparison with another water vapor sensor such as radiosondes. We present a new method for water vapor calibration that only requires low clouds, and surface pressure and temperature measurements. A sensitivity study was performed and the cloud base algorithm agrees with the radiosonde calibration to within 10- 15%. Knowledge of the true atmospheric lapse rate is required to obtain more accurate cloud base temperatures. Analysis of water vapor and aerosol measurements made in the vicinity of Hurricane Bonnie are discussed.

  2. A New Raman Water Vapor Lidar Calibration Technique and Measurements in the Vicinity of Hurricane Bonnie

    NASA Technical Reports Server (NTRS)

    Evans, Keith D.; Demoz, Belay B.; Cadirola, Martin P.; Melfi, S. H.; Whiteman, David N.; Schwemmer, Geary K.; Starr, David O'C.; Schmidlin, F. J.; Feltz, Wayne; Tobin, David

    2000-01-01

    The NASA/Goddard Space Flight Center Scanning Raman Lidar has made measurements of water vapor and aerosols for almost ten years. Calibration of the water vapor data has typically been performed by comparison with another water vapor sensor such as radiosondes. We present a new method for water vapor calibration that only requires low clouds, and surface pressure and temperature measurements. A sensitivity study was performed and the cloud base algorithm agrees with the radiosonde calibration to within 10-15%. Knowledge of the true atmospheric lapse rate is required to obtain more accurate cloud base temperatures. Analysis of water vapor and aerosol measurements made in the vicinity of Hurricane Bonnie are discussed.

  3. Signal enhancement of a novel multi-address coding lidar backscatters based on a combined technique of demodulation and wavelet de-noising

    NASA Astrophysics Data System (ADS)

    Xu, Fan; Wang, Yuanqing

    2015-11-01

    Multi-address coding (MAC) lidar is a novel lidar system recently developed by our laboratory. By applying a new combined technique of multi-address encoding, multiplexing and decoding, range resolution is effectively improved. In data processing, a signal enhancement method involving laser signal demodulation and wavelet de-noising in the downlink is proposed to improve the signal to noise ratio (SNR) of raw signal and the capability of remote application. In this paper, the working mechanism of MAC lidar is introduced and the implementation of encoding and decoding is also illustrated. We focus on the signal enhancement method and provide the mathematical model and analysis of an algorithm on the basis of the combined method of demodulation and wavelet de-noising. The experimental results and analysis demonstrate that the signal enhancement approach improves the SNR of raw data. Overall, compared with conventional lidar system, MAC lidar achieves a higher resolution and better de-noising performance in long-range detection.

  4. Inter-comparison of 2 microm Heterodyne Differential Absorption Lidar, Laser Diode Spectrometer, LICOR NDIR analyzer and flasks measurements of near-ground atmospheric CO2 mixing ratio.

    PubMed

    Gibert, Fabien; Joly, Lilian; Xuéref-Rémy, Irène; Schmidt, Martina; Royer, Adrien; Flamant, Pierre H; Ramonet, Michel; Parvitte, Bertrand; Durry, Georges; Zéninari, Virginie

    2009-01-01

    Remote sensing and in situ instruments are presented and compared in the same location for accurate CO(2) mixing ratio measurements in the atmosphere: (1) a 2.064 microm Heterodyne DIfferential Absorption Lidar (HDIAL), (2) a field deployable infrared Laser Diode Spectrometer (LDS) using new commercial diode laser technology at 2.68 microm, (3) LICOR NDIR analyzer and (4) flasks. LDS, LICOR and flasks measurements were made in the same location, LICOR and flasks being taken as reference. Horizontal HDIAL measurements of CO(2) absorption using aerosol backscatter signal are reported. Using new spectroscopic data in the 2 microm band and meteorological sensor measurements, a mean CO(2) mixing ratio is inferred by the HDIAL in a 1 km long path above the 15m height location of the CO(2) in situ sensors. We compare HDIAL and LDS measurements with the LICOR data for 30 min of time averaging. The mean standard deviation of the HDIAL and the LDS CO(2) mixing ratio results are 3.3 ppm and 0.89 ppm, respectively. The bias of the HDIAL and the LDS measurements are -0.54 ppm and -0.99 ppm, respectively. PMID:18718810

  5. Study of Ground Subsidence in North West Houston using GPS, LiDAR and InSAR techniques

    NASA Astrophysics Data System (ADS)

    Karacay, A.; Khan, S. D.

    2012-12-01

    Land subsidence can be caused by natural or human activities, such as carbonate dissolution, extraction of material from mines, soil compaction and fluid withdrawal. This phenomenon affects many cities around the world, such as Nagoya-Japan, Venice-Italy, San Joaquin Valley and Long Beach in California. Recent work by Engelkemeir et al, (2010), suggested that subsidence occurred as high as 5.6 cm/year in northwest Houston. The processes that may contribute to land subsidence in the Houston-Galveston area includes faulting, soil compaction, salt tectonic, water pumping and hydrocarbon extraction. This study aims to assess the possible role of water pumping on subsidence. Northwest Houston has two aquifer systems, the Evangeline and Chicot aquifers that dip in the southeast direction. The effect of water pumping on subsidence from these two aquifers was monitored using InSAR, GPS and LiDAR data. The data from eleven GPS stations were processed using Online Positioning User Service (OPUS) of National Geodetic Survey (NGS). Three of these GPS stations are Continuously Operating Reference Stations (CORS) and eight are Port-A-Measure (PAM) sites. All the GPS data were obtained from Harris-Galveston Subsidence District (HGSD). CORS sites were used as reference stations for processing GPS data from the PAM stations. GPS data show that subsidence rate in northwest Houston decreased to approximately 2 cm/year. In addition, the surface deformation is also estimated using Light Detection and Ranging (LiDAR) technique. For this purpose, raw LiDAR (LAS-Long ASCII Standart) files of 2001 and 2008 were processed. The subsidence rate near the Hockley Fault was calculated by applying zonal statistics method on LiDAR data which shows about 10 cm of subsidence in nine years. This result is supported by processed GPS data from PAM site 48 that show subsidence rate of 1.3 cm/yr. For the InSAR (Interferometric Synthetic Aperture Radar) technique, an image pair of PALSAR (The Phased Array

  6. Correction technique for Raman water vapor lidar signal-dependent bias and suitability for water vapor trend monitoring in the upper troposphere

    NASA Astrophysics Data System (ADS)

    Whiteman, D. N.; Cadirola, M.; Venable, D.; Calhoun, M.; Miloshevich, L.; Vermeesch, K.; Twigg, L.; Dirisu, A.; Hurst, D.; Hall, E.; Jordan, A.; Vömel, H.

    2012-11-01

    The MOHAVE-2009 campaign brought together diverse instrumentation for measuring atmospheric water vapor. We report on the participation of the ALVICE (Atmospheric Laboratory for Validation, Interagency Collaboration and Education) mobile laboratory in the MOHAVE-2009 campaign. In appendices we also report on the performance of the corrected Vaisala RS92 radiosonde measurements during the campaign, on a new radiosonde based calibration algorithm that reduces the influence of atmospheric variability on the derived calibration constant, and on other results of the ALVICE deployment. The MOHAVE-2009 campaign permitted the Raman lidar systems participating to discover and address measurement biases in the upper troposphere and lower stratosphere. The ALVICE lidar system was found to possess a wet bias which was attributed to fluorescence of insect material that was deposited on the telescope early in the mission. Other sources of wet biases are discussed and data from other Raman lidar systems are investigated, revealing that wet biases in upper tropospheric (UT) and lower stratospheric (LS) water vapor measurements appear to be quite common in Raman lidar systems. Lower stratospheric climatology of water vapor is investigated both as a means to check for the existence of these wet biases in Raman lidar data and as a source of correction for the bias. A correction technique is derived and applied to the ALVICE lidar water vapor profiles. Good agreement is found between corrected ALVICE lidar measurments and those of RS92, frost point hygrometer and total column water. The correction is offered as a general method to both quality control Raman water vapor lidar data and to correct those data that have signal-dependent bias. The influence of the correction is shown to be small at regions in the upper troposphere where recent work indicates detection of trends in atmospheric water vapor may be most robust. The correction shown here holds promise for permitting useful upper

  7. Correction Technique for Raman Water Vapor Lidar Signal-Dependent Bias and Suitability for Water Wapor Trend Monitoring in the Upper Troposphere

    NASA Technical Reports Server (NTRS)

    Whiteman, D. N.; Cadirola, M.; Venable, D.; Calhoun, M.; Miloshevich, L; Vermeesch, K.; Twigg, L.; Dirisu, A.; Hurst, D.; Hall, E.; Jordan, A.; Voemel, H.

    2012-01-01

    The MOHAVE-2009 campaign brought together diverse instrumentation for measuring atmospheric water vapor. We report on the participation of the ALVICE (Atmospheric Laboratory for Validation, Interagency Collaboration and Education) mobile laboratory in the MOHAVE-2009 campaign. In appendices we also report on the performance of the corrected Vaisala RS92 radiosonde measurements during the campaign, on a new radiosonde based calibration algorithm that reduces the influence of atmospheric variability on the derived calibration constant, and on other results of the ALVICE deployment. The MOHAVE-2009 campaign permitted the Raman lidar systems participating to discover and address measurement biases in the upper troposphere and lower stratosphere. The ALVICE lidar system was found to possess a wet bias which was attributed to fluorescence of insect material that was deposited on the telescope early in the mission. Other sources of wet biases are discussed and data from other Raman lidar systems are investigated, revealing that wet biases in upper tropospheric (UT) and lower stratospheric (LS) water vapor measurements appear to be quite common in Raman lidar systems. Lower stratospheric climatology of water vapor is investigated both as a means to check for the existence of these wet biases in Raman lidar data and as a source of correction for the bias. A correction technique is derived and applied to the ALVICE lidar water vapor profiles. Good agreement is found between corrected ALVICE lidar measurments and those of RS92, frost point hygrometer and total column water. The correction is offered as a general method to both quality control Raman water vapor lidar data and to correct those data that have signal-dependent bias. The influence of the correction is shown to be small at regions in the upper troposphere where recent work indicates detection of trends in atmospheric water vapor may be most robust. The correction shown here holds promise for permitting useful upper

  8. Ground Based Lidar Characterization of Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Eloranta, Edwin W.

    1996-01-01

    This paper presents cirrus cloud observations made with the High Spectral Resolution Lidar (HSRL) and the Volume Imaging Lidar (VIL). The HSRL was redesigned to use an iodine absorption filter in place of the Fabry-Perot etalon that was used for spectral separation of the aerosol and molecular lidar returns. These modifications, which improve both sensitivity and calibration stability, are described.

  9. Investigation of Overlap Correction Techniques for Application in the Micro-Pulse Lidar Network (MPLNET)

    NASA Technical Reports Server (NTRS)

    Berkoff, Timothy A.; Welton, Ellsworth J.; Campbell, James R.; Scott, Vibart S.; Spinhirne, James D.

    2003-01-01

    The Micro-Pulse Lidar NETwork (MPLNET) is comprised of micro-pulse lidars (MPL) stationed around the globe to provide measurements of aerosol and cloud vertical distribution on a continuous basis. MPLNET sites are co-located with sunphotometers in the AErosol Robotic NETwork (AERONET) to provide joint measurements of aerosol optical depth, size, and other inherent optical properties. The IPCC 2001 report discusses . the importance of obtaining routine measurements of aerosol vertical structure, especially for absorbing aerosols. MPLNET provides exactly this sort of measurement, including calculation of aerosol extinction profiles, in a near real-time basis for all sites in the network. In order to obtain aerosol profiles, near range signal returns (0-6 km) must be accurately measured by the MPL. This measurement is complicated by the instrument s overlap range: Le., the minimum distance at which returning signals are completely in the instrument s field-of-view (FOV). Typical MPL overlap distances are large, between 5 - 6 km, due to the narrow FOV of the MPL receiver. A function describing the MPL overlap must be determined and used to correct signals in this range. Currently, overlap functions for MPLNET are determined using horizontal MPL measurements along a path with 10-1 5 km clear line-of-sight and a homogenous atmosphere. These conditions limit the location and ease in which successful overlaps can be obtained. Furthermore, the current MPLNET process of correcting for overlap increases the uncertainty and bias error for the near range signals and the resulting aerosol extinction profiles. To address these issues, an alternative overlap correction method using a small-diameter, wide FOV receiver is being considered for potential use in MPLNET. The wide FOV receiver has a much shorter overlap distance and will be used to calculate the overlap function of the MPL receiver. This approach has a significant benefit in that overlap corrections could be obtained

  10. Application of lidar techniques to time-of-flight range imaging.

    PubMed

    Whyte, Refael; Streeter, Lee; Cree, Michael J; Dorrington, Adrian A

    2015-11-20

    Amplitude-modulated continuous wave (AMCW) time-of-flight (ToF) range imaging cameras measure distance by illuminating the scene with amplitude-modulated light and measuring the phase difference between the transmitted and reflected modulation envelope. This method of optical range measurement suffers from errors caused by multiple propagation paths, motion, phase wrapping, and nonideal amplitude modulation. In this paper a ToF camera is modified to operate in modes analogous to continuous wave (CW) and stepped frequency continuous wave (SFCW) lidar. In CW operation the velocity of objects can be measured. CW measurement of velocity was linear with true velocity (R2=0.9969). Qualitative analysis of a complex scene confirms that range measured by SFCW is resilient to errors caused by multiple propagation paths, phase wrapping, and nonideal amplitude modulation which plague AMCW operation. In viewing a complicated scene through a translucent sheet, quantitative comparison of AMCW with SFCW demonstrated a reduction in the median error from -1.3  m to -0.06  m with interquartile range of error reduced from 4.0 m to 0.18 m. PMID:26836520

  11. Orbiting lidar simulations. 1: Aerosol and cloud measurements by an independent-wavelength technique.

    PubMed

    Russell, P B; Morley, B M; Livingston, J M; Grams, G W; Patterson, E M

    1982-05-01

    Aerosol and cloud measurements are simulated for a space shuttle lidar. Expected errors (in signal, transmission, density, and calibration) are calculated algebraically and checked by simulating measurements and retrievals using random number generators. Vertical resolution is 0.1-0.5 km in the troposphere, 0.5-2.0 km above, except 0.25-1.0 km in mesospheric cloud and aerosol layers. Horizontal resolution is 100-2000 km. By day vertical structure is retrieved for tenuous clouds, Saharan aerosols, and boundary layer aerosols (at 0.53 and 1.06 microm) as well as strong volcanic stratospheric aerosols (at 0.53 microm). Quantitative backscatter is retrieved provided that particulate optical depth does not exceed approximately 0.3. By night all these constituents are retrieved plus upper tropospheric and stratospheric aerosols (at 1.06 microm), mesospheric aerosols (at 0.53 microm), and noctilucent clouds (at 1.06 and 0.53 microm). Molecular density is a leading source of error in measuring nonvolcanic stratospheric and upper tropospheric aerosols.

  12. Measurement of the absorption coefficient of a glucose solution through transmission of light and polarymetry techniques

    NASA Astrophysics Data System (ADS)

    Yáñez M., J.

    2011-10-01

    Diabetes is a disease with no cure, but can be controlled to improve the quality of life of sufferers. Currently there are means to control, but this means they have the disadvantage that in order to measure the amount of glucose is necessary to take blood samples that are painful. This paper presents a system for measuring glucose using non-invasive optical techniques: using absorption spectroscopy and polarimetry technique. It shows the results obtained from experiments done on samples containing distilled water and different amounts of glucose to study the absorption coefficient of glucose with both techniques. Water is used because it is one of the main elements in the blood and interferes with glucose measurement. This experiment will develop a prototype to measure glucose through a non-invasive technique.

  13. A quality control technique based on UV-VIS absorption spectroscopy for tequila distillery factories

    NASA Astrophysics Data System (ADS)

    Barbosa Garcia, O.; Ramos Ortiz, G.; Maldonado, J. L.; Pichardo Molina, J.; Meneses Nava, M. A.; Landgrave, Enrique; Cervantes, M. J.

    2006-02-01

    A low cost technique based on the UV-VIS absorption spectroscopy is presented for the quality control of the spirit drink known as tequila. It is shown that such spectra offer enough information to discriminate a given spirit drink from a group of bottled commercial tequilas. The technique was applied to white tequilas. Contrary to the reference analytic methods, such as chromatography, for this technique neither special personal training nor sophisticated instrumentations is required. By using hand-held instrumentation this technique can be applied in situ during the production process.

  14. A Compact Ti:Sapphire Laser With its Third Harmonic Generation (THG) for an Airborne Ozone Differential Absorption Lidar (DIAL) Transmitter

    NASA Technical Reports Server (NTRS)

    Chen, Songsheng; Storm, Mark E.; Marsh, Waverly D.; Petway, Larry B.; Edwards, William C.; Barnes, James C.

    2000-01-01

    A compact and high-pulse-energy Ti:Sapphire laser with its Third Harmonic Generation (THG) has been developed for an airborne ozone differential absorption lidar (DIAL) to study the distributions and concentrations of the ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a frequency-doubled Nd:YAG laser and seeded by a single mode diode laser, is operated either at 867 nm or at 900 nm with a pulse repetition frequency of 20 Hz. High energy laser pulses (more than 110 mJ/pulse) at 867 nm or 900 nm with a desired beam quality have been achieved and utilized to generate its third harmonic at 289nm or 300nm, which are on-line and off-line wavelengths of an airborne ozone DIAL. After being experimentally compared with Beta-Barium Borate (beta - BaB2O4 or BBO) nonlinear crystals, two Lithium Triborate (LBO) crystals (5 x 5 x 20 cu mm) are selected for the Third Harmonic Generation (THG). In this paper, we report the Ti:Sapphire laser at 900 nm and its third harmonic at 300 nm. The desired high ultraviolet (UV) output pulse energy is more than 30 mJ at 300 nm and the energy conversion efficiency from 900 nm to 300 nm is 30%.

  15. Analysis of a random modulation single photon counting differential absorption lidar system for space-borne atmospheric CO2 sensing.

    PubMed

    Ai, X; Pérez-Serrano, A; Quatrevalet, M; Nock, R W; Dahnoun, N; Ehret, G; Esquivias, I; Rarity, J G

    2016-09-01

    The ability to observe the Earth's carbon cycles from space provides scientists an important tool to analyze climate change. Current proposed systems are mainly based on pulsed integrated path differential absorption lidar, in which two high energy pulses at different wavelengths interrogate the atmosphere sequentially for its transmission properties and are back-scattered by the ground. In this work an alternative approach based on random modulation single photon counting is proposed and analyzed; this system can take advantage of a less power demanding semiconductor laser in intensity modulated continuous wave operation, benefiting from a better efficiency, reliability and radiation hardness. Our approach is validated via numerical simulations considering current technological readiness, demonstrating its potential to obtain a 1.5 ppm retrieval precision for 50 km averaging with 2.5 W average power in a space-borne scenario. A major limiting factor is the ambient shot noise, if ultra-narrow band filtering technology could be applied, 0.5 ppm retrieval precision would be attainable.

  16. Simulation and Theory of Speckle Noise for an Annular Aperture Frequency-Modulation Differential-Absorption LIDAR (FM-DIAL) System

    SciTech Connect

    Keller, Paul E.; Batdorf, Michael T.; Strasburg, Jana D.; Harper, Warren W.

    2009-05-28

    This paper presents theory of speckle noise for a frequency-modulation differential-absorption LIDAR system along with simulation results. These results show an unexpected relationship between the signal-to-noise ratio (SNR) of the speckle and the distance to the retro-reflector or target. In simulation, the use of an annular aperture in the system results in a higher SNR at midrange distances than at short or long distances. This peak in SNR occurs in the region where the laser’s Gaussian beam profile approximately fills the target. This was unexpected since it does not occur in the theory or simulations of the same system with a circular aperture. By including the autocorrelation of this annular aperture and expanding the complex correlation factor used in speckle models to include conditions not generally covered, a more complete theoretical model is derived for this system. Obscuration of the center of the beam at near distances is also a major factor in this relationship between SNR and distance. We conclude by comparing the resulting SNR as a function of distance from this expanded theoretical model to the simulations of the system over a double-pass horizontal range of 10 meters to 10 km at a wavelength of 1.28 micrometers

  17. Analysis of a random modulation single photon counting differential absorption lidar system for space-borne atmospheric CO2 sensing.

    PubMed

    Ai, X; Pérez-Serrano, A; Quatrevalet, M; Nock, R W; Dahnoun, N; Ehret, G; Esquivias, I; Rarity, J G

    2016-09-01

    The ability to observe the Earth's carbon cycles from space provides scientists an important tool to analyze climate change. Current proposed systems are mainly based on pulsed integrated path differential absorption lidar, in which two high energy pulses at different wavelengths interrogate the atmosphere sequentially for its transmission properties and are back-scattered by the ground. In this work an alternative approach based on random modulation single photon counting is proposed and analyzed; this system can take advantage of a less power demanding semiconductor laser in intensity modulated continuous wave operation, benefiting from a better efficiency, reliability and radiation hardness. Our approach is validated via numerical simulations considering current technological readiness, demonstrating its potential to obtain a 1.5 ppm retrieval precision for 50 km averaging with 2.5 W average power in a space-borne scenario. A major limiting factor is the ambient shot noise, if ultra-narrow band filtering technology could be applied, 0.5 ppm retrieval precision would be attainable. PMID:27607715

  18. A new technique to assess dermal absorption of volatile chemicals in vitro by thermal gravimetric analysis.

    PubMed

    Rauma, Matias; Isaksson, Tina S; Johanson, Gunnar

    2006-10-01

    Potential health hazards of dermal exposure, variability in reported dermal absorption rates and potential losses from the skin by evaporation indicate a need for a simple, inexpensive and standardized procedure to measure dermal absorption and desorption of chemical substances. The aim of this study was to explore the possibility to measure dermal absorption and desorption of volatile chemicals using a new gravimetric technique, namely thermal gravimetric analysis (TGA), and trypsinated stratum corneum from pig. Changes in skin weight were readily detected before, during and after exposure to vapours of water, 2-propanol, methanol and toluene. The shape and height of the weight curves differed between the four chemicals, reflecting differences in diffusivity and partial pressure and skin:air partitioning, respectively. As the skin weight is highly sensitive to the partial pressure of volatile chemicals, including water, this technique requires carefully controlled conditions with respect to air flow, temperature, chemical vapour generation and humidity. This new technique may help in the assessment of dermal uptake of volatile chemicals. Only a small piece of skin is needed and skin integrity is not necessary, facilitating the use of human samples. The high resolution weight-time curves obtained may also help to elucidate the characteristics of absorption, desorption and diffusion of chemicals in skin.

  19. NDSC and JPL stratospheric lidars

    NASA Technical Reports Server (NTRS)

    McDermid, I. Stuart

    1995-01-01

    The Network for the Detection of Stratospheric Change is an international cooperation providing a set of high-quality, remote-sensing instruments at observing stations around the globe. A brief description of the NDSC and its goals is presented. Lidar has been selected as the NDSC instrument for measurements of stratospheric profiles of ozone, temperature, and aerosol. The Jet Propulsion Laboratory has developed and implemented two stratospheric lidar systems for NDSC. These are located at Table Mountain, California, and at Mauna Loa, Hawaii. These systems, which utilize differential absorption lidar, Rayleigh lidar, raman lidar, and backscatter lidar, to measure ozone, temperature, and aerosol profiles in the stratosphere are briefly described. Examples of results obtained for both long-term and individual profiles are presented.

  20. Quantitative chemical identification of four gases in remote infrared (9-11 mum) differential absorption lidar experiments.

    PubMed

    Quagliano, J R; Stoutland, P O; Petrin, R R; Sander, R K; Romero, R J; Whitehead, M C; Quick, C R; Tiee, J J; Jolin, L J

    1997-03-20

    A combined experimental and computational approach utilizing tunable CO(2) lasers and chemometric analysis was employed to detect chemicals and their concentrations in the field under controlled release conditions. We collected absorption spectra for four organic gases in the laboratory by lasing 40 lines of the laser in the 9.3-10.8-mum range. The ability to predict properly the chemicals and their respective concentrations depends on the nature of the target, the atmospheric conditions, and the round-trip distance. In 39 of the 45 field experiments, the identities of the released chemicals were identified correctly without predictions of false positives or false negatives. PMID:18250883

  1. Spectrum sensing of trace C(2)H(2) detection in differential optical absorption spectroscopy technique.

    PubMed

    Chen, Xi; Dong, Xiaopeng

    2014-09-10

    An improved algorithm for trace C(2)H(2) detection is presented in this paper. The trace concentration is accurately calculated by focusing on the absorption spectrum from the frequency domain perspective. The advantage of the absorption spectroscopy frequency domain algorithm is its anti-interference capability. First, the influence of the background noise on the minimum detectable concentration is greatly reduced. Second, the time-consuming preprocess of spectra calibration in the differential optical absorption spectroscopy technique is skipped. Experimental results showed the detection limit of 50 ppm is achieved at a lightpath length of 0.2 m. This algorithm can be used in real-time spectrum analysis with high accuracy.

  2. Absorption-edge transmission technique using Ce- 139 for measurement of stable iodine concentration.

    PubMed

    Sorenson, J A

    1979-12-01

    We have investigated a technique for measuring stable iodine concentrations by absorption-edge transmission measurements using a Ce 139 radiation source. The lanthanum daughter emits characteristic x-rays whose energies just bracket the absorption edge of iodine at 33.2 keV. Relative transmission of these x-rays is sensitive to iodine concentration in the sample, but is relatively insensitive to other elements. By applying energy-selective beam filtration, it is possible to determine the relative transmission of these closely spaced x-ray energies with NaI(Tl) detectors. Optimizations of sample thickness, detector thickness, and Ce-139 source activity are discussed. Using sample volumes of about 10 ml, one can determine iodine concentration to an uncertainty (standard deviation) of +/- 5 microgram/ml with a 5-mCi source in a measurement time of 400 sec. Potential clinical applications of the in vitro technique are discussed, along with comparative aspects of the Ce-139 technique and other absorption and fluorescence techniques for measuring stable iodine. PMID:536797

  3. Absorption-edge transmission technique using Ce- 139 for measurement of stable iodine concentration.

    PubMed

    Sorenson, J A

    1979-12-01

    We have investigated a technique for measuring stable iodine concentrations by absorption-edge transmission measurements using a Ce 139 radiation source. The lanthanum daughter emits characteristic x-rays whose energies just bracket the absorption edge of iodine at 33.2 keV. Relative transmission of these x-rays is sensitive to iodine concentration in the sample, but is relatively insensitive to other elements. By applying energy-selective beam filtration, it is possible to determine the relative transmission of these closely spaced x-ray energies with NaI(Tl) detectors. Optimizations of sample thickness, detector thickness, and Ce-139 source activity are discussed. Using sample volumes of about 10 ml, one can determine iodine concentration to an uncertainty (standard deviation) of +/- 5 microgram/ml with a 5-mCi source in a measurement time of 400 sec. Potential clinical applications of the in vitro technique are discussed, along with comparative aspects of the Ce-139 technique and other absorption and fluorescence techniques for measuring stable iodine.

  4. CHARM-F: An airborne Integrated Path Differential Absorption (IPDA) LIDAR for the simultaneous measurement of CO2 and CH4 Columns

    NASA Astrophysics Data System (ADS)

    Wirth, M.; Amediek, A.; Büdenbender, C.; Ehret, G.; Fix, A.; Kiemle, C.; Quatrevalet, M.; Hoffmann, D.; Löhring, J.; Klein, V.; Schöggl, R.

    2011-12-01

    Currently, Deutsches Zentrum für Luft- und Raumfahrt (DLR) - in collaboration with Fraunhofer-Institut für Lasertechnik (ILT) and Kayser-Threde GmbH (KT) - is developing CHARM-F, an Integrated Path Differential Absorption (IPDA) LIDAR for simultaneous measurement of CO2 and CH4 columns. Design goal is a compact and rugged instrument optimized for airborne use on board of DLR's long range research aircraft HALO. The main scientific goal of the instrument is to provide precise column measurements of CO2 and CH4 to infer fluxes of these important greenhouse gases by means of inverse modeling. For this purpose, very stringent requirements concerning accuracy and precision have to be met since typical surface sources and sinks alter the total column only by a few percent. To achieve this, CHARM-F uses laser sources emitting pulse-pairs with nanosecond duration which allows for a precise ranging and a proper separation of atmospheric influences (i.e. aerosol and clouds) from the ground return leading to an unambiguously defined column (no airmass factors involved). Two laser systems - one for each trace gas - are employed using highly efficient and robust Nd:YAG lasers to pump optical parametric oscillators (OPO) which convert the pump radiation to the desired measurement wavelengths in the near infrared. Each laser system emits a pulse pair having different wavelengths. One is tuned to an absorption line of the trace gas under consideration and the other one to a nearby wavelength with much less absorption. The close temporal pulse separation of 250 μs together with a relatively large spot size of 30 m on ground ensures that nearly the same area is illuminated by both pulses. To achieve single-mode operation, both the pump and the OPO are injection seeded. The seed lasers are locked to a gas cell filled with a mixture of CO2 and CH4 to ensure an absolute wavelength calibration. Furthermore, deviations of the wavelength between outgoing laser pulse and the seed lasers

  5. Water vapor lidar

    NASA Technical Reports Server (NTRS)

    Ellingson, R.; Mcilrath, T.; Schwemmer, G.; Wilkerson, T. D.

    1976-01-01

    The feasibility was studied of measuring atmospheric water vapor by means of a tunable lidar operated from the space shuttle. The specific method evaluated was differential absorption, a two-color method in which the atmospheric path of interest is traversed by two laser pulses. Results are reported.

  6. New Examination of the Traditional Raman Lidar Technique II: Temperature Dependence Aerosol Scattering Ratio and Water Vapor Mixing Ratio Equations

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Abshire, James B. (Technical Monitor)

    2002-01-01

    In a companion paper, the temperature dependence of Raman scattering and its influence on the Raman water vapor signal and the lidar equations was examined. New forms of the lidar equation were developed to account for this temperature sensitivity. Here we use those results to derive the temperature dependent forms of the equations for the aerosol scattering ratio, aerosol backscatter coefficient, extinction to backscatter ratio and water vapor mixing ratio. Pertinent analysis examples are presented to illustrate each calculation.

  7. Atmospheric Pre-Corrected Differential Absorption Techniques to Retrieve Columnar Water Vapor: Theory and Simulations

    NASA Technical Reports Server (NTRS)

    Borel, Christoph C.; Schlaepfer, Daniel

    1996-01-01

    Two different approaches exist to retrieve columnar water vapor from imaging spectrometer data: (1) Differential absorption techniques based on: (a) Narrow-Wide (N/W) ratio between overlapping spectrally wide and narrow channels; (b) Continuum Interpolated Band Ratio (CIBR) between a measurement channel and the weighted sum of two reference channels. (2) Non-linear fitting techniques which are based on spectral radiative transfer calculations. The advantage of the first approach is computational speed and of the second, improved retrieval accuracy. Our goal was to improve the accuracy of the first technique using physics based on radiative transfer. Using a modified version of the Duntley equation, we derived an "Atmospheric Pre-corrected Differential Absorption" (APDA) technique and described an iterative scheme to retrieve water vapor on a pixel-by-pixel basis. Next we compared both, the CIBR and the APDA using the Duntley equation for MODTRAN3 computed irradiances, transmissions and path radiance (using the DISORT option). This simulation showed that the CIBR is very sensitive to reflectance effects and that the APDA performs much better. An extensive data set was created with the radiative transfer code 6S over 379 different ground reflectance spectra. The calculated relative water vapor error was reduced significantly for the APDA. The APDA technique had about 8% (vs. over 35% for the CIBR) of the 379 spectra with a relative water vapor error of greater than +5%. The APDA has been applied to 1991 and 1995 AVIRIS scenes which visually demonstrate the improvement over the CIBR technique.

  8. Oceanic Lidar

    NASA Technical Reports Server (NTRS)

    Carder, K. L. (Editor)

    1981-01-01

    Instrument concepts which measure ocean temperature, chlorophyll, sediment and Gelbstoffe concentrations in three dimensions on a quantitative, quasi-synoptic basis were considered. Coastal zone color scanner chlorophyll imagery, laser stimulated Raman temperaure and fluorescence spectroscopy, existing airborne Lidar and laser fluorosensing instruments, and their accuracies in quantifying concentrations of chlorophyll, suspended sediments and Gelbstoffe are presented. Lidar applications to phytoplankton dynamics and photochemistry, Lidar radiative transfer and signal interpretation, and Lidar technology are discussed.

  9. Sensitivity optimization of the one beam Z-scan technique and a Z-scan technique immune to nonlinear absorption.

    PubMed

    Dávila Pintle, José A; Lara, Edmundo Reynoso; Iturbe Castillo, Marcelo D

    2013-07-01

    It is presented a criteria for selecting the optimum aperture radius for the one beam Z-scan technique (OBZT), based on the analysis of the transmittance of the aperture. It is also presented a modification to the OBZT by directly measuring the beam radius in the far field with a rotating disk, which allows to determine simultaneously the non-linear absorptive coefficient and non-linear refractive index, much less sensitive to wave front distortions caused by inhomogeneities of the sample with a negligible loss of signal to noise ratio. It is demonstrated its equivalence to the OBZT.

  10. Coal thickness gauge using RRAS techniques, part 1. [radiofrequency resonance absorption

    NASA Technical Reports Server (NTRS)

    Rollwitz, W. L.; King, J. D.

    1978-01-01

    A noncontacting sensor having a measurement range of 0 to 6 in or more, and with an accuracy of 0.5 in or better is needed to control the machinery used in modern coal mining so that the thickness of the coal layer remaining over the rock is maintained within selected bounds. The feasibility of using the radiofrequency resonance absorption (RRAS) techniques of electron magnetic resonance (EMR) and nuclear magnetic resonance (NMR) as the basis of a coal thickness gauge is discussed. The EMR technique was found, by analysis and experiments, to be well suited for this application.

  11. Theory of the double-edge technique for Doppler lidar wind measurement.

    PubMed

    Korb, C L; Gentry, B M; Li, S X; Flesia, C

    1998-05-20

    The theory of the double-edge technique is described by a generalized formulation that substantially extends the capabilities of the edge technique. It uses two edges with opposite slopes located about the laser frequency. This doubles the signal change for a given Doppler shift and yields a factor of 1.6 improvement in the measurement accuracy compared with the single-edge technique. Use of two high-resolution edge filters reduces the effects of Rayleigh scattering on the measurement by as much as an order of magnitude and allows the signal-to-noise ratio to be substantially improved in areas of low aerosol backscatter. We describe a method that allows the Rayleigh and aerosol components of the signal to be independently determined. The effects of Rayleigh scattering are then subtracted from the measurement, and we show that the correction process does not significantly increase the measurement noise for Rayleigh-to-aerosol ratios as high as 10. We show that for small Doppler shifts a measurement accuracy of 0.4 m/s can be obtained for 5000 detected photons, 1.2 m/s for 1000 detected photons, and 3.7 m/s for 50 detected photons for a Rayleigh-to-aerosol ratio of 5. Methods for increasing the dynamic range to more than +/-100 m/s are given. PMID:18273256

  12. Lidar instruments proposed for Eos

    NASA Technical Reports Server (NTRS)

    Grant, William B.; Browell, Edward V.

    1990-01-01

    Lidar, an acronym for light detection and ranging, represents a class of instruments that utilize lasers to send probe beams into the atmosphere or onto the surface of the Earth and detect the backscattered return in order to measure properties of the atmosphere or surface. The associated technology has matured to the point where two lidar facilities, Geodynamics Laser Ranging System (GLRS), and Laser Atmospheric Wind Sensor (LAWS) were accepted for Phase 2 studies for Eos. A third lidar facility Laser Atmospheric Sounder and Altimeter (LASA), with the lidar experiment EAGLE (Eos Atmospheric Global Lidar Experiment) was proposed for Eos. The generic lidar system has a number of components. They include controlling electronics, laser transmitters, collimating optics, a receiving telescope, spectral filters, detectors, signal chain electronics, and a data system. Lidar systems that measure atmospheric constituents or meteorological parameters record the signal versus time as the beam propagates through the atmosphere. The backscatter arises from molecular (Rayleigh) and aerosol (Mie) scattering, while attenuation arises from molecular and aerosol scattering and absorption. Lidar systems that measure distance to the Earth's surface or retroreflectors in a ranging mode record signals with high temporal resolution over a short time period. The overall characteristics and measurements objectives of the three lidar systems proposed for Eos are given.

  13. Lidar measurements of stratospheric ozone at Table Mountain, California, since 1988

    NASA Technical Reports Server (NTRS)

    Mcdermid, I. Stuart; Schmoe, Martha; Walsh, T. Daniel

    1994-01-01

    Regular measurements of stratospheric ozone concentration profiles have been made at Table Mountain, California, since January 1988. During the period to December 1991, 435 independent profiles were measured by the differential absorption lidar technique. These long-term results, and an evaluation of their quality, is presented in this paper.

  14. Lidar Report

    SciTech Connect

    Wollpert.

    2009-04-01

    This report provides an overview of the LiDAR acquisition methodology employed by Woolpert on the 2009 USDA - Savannah River LiDAR Site Project. LiDAR system parameters and flight and equipment information is also included. The LiDAR data acquisition was executed in ten sessions from February 21 through final reflights on March 2, 2009; using two Leica ALS50-II 150kHz Multi-pulse enabled LiDAR Systems. Specific details about the ALS50-II systems are included in Section 4 of this report.

  15. Method and apparatus for measuring butterfat and protein content using microwave absorption techniques

    DOEpatents

    Fryer, Michael O.; Hills, Andrea J.; Morrison, John L.

    2000-01-01

    A self calibrating method and apparatus for measuring butterfat and protein content based on measuring the microwave absorption of a sample of milk at several microwave frequencies. A microwave energy source injects microwave energy into the resonant cavity for absorption and reflection by the sample undergoing evaluation. A sample tube is centrally located in the resonant cavity passing therethrough and exposing the sample to the microwave energy. A portion of the energy is absorbed by the sample while another portion of the microwave energy is reflected back to an evaluation device such as a network analyzer. The frequency at which the reflected radiation is at a minimum within the cavity is combined with the scatter coefficient S.sub.11 as well as a phase change to calculate the butterfat content in the sample. The protein located within the sample may also be calculated in a likewise manner using the frequency, S.sub.11 and phase variables. A differential technique using a second resonant cavity containing a reference standard as a sample will normalize the measurements from the unknown sample and thus be self-calibrating. A shuttered mechanism will switch the microwave excitation between the unknown and the reference cavities. An integrated apparatus for measuring the butterfat content in milk using microwave absorption techniques is also presented.

  16. In vivo measurement of human skin absorption of topically applied substances by a photoacoustic technique.

    PubMed

    Gutiérrez-Juárez, G; Vargas-Luna, M; Córdova, T; Varela, J B; Bernal-Alvarado, J J; Sosa, M

    2002-08-01

    A photoacoustic technique is used for studying topically applied substance absorption in human skin. The proposed method utilizes a double-chamber PA cell. The absorption determination was obtained through the measurement of the thermal effusivity of the binary system substance-skin. The theoretical model assumes that the effective thermal effusivity of the binary system corresponds to that of a two-phase system. Experimental applications of the method employed different substances of topical application in different parts of the body of a volunteer. The method is demonstrated to be an easily used non-invasive technique for dermatology research. The relative concentrations as a function of time of substances such as ketoconazol and sunscreen were determined by fitting a sigmoidal function to the data, while an exponential function corresponds to the best fit for the set of data for nitrofurazona, vaseline and vaporub. The time constants associated with the rates of absorption, were found to vary in the range between 10 and 58 min, depending on the substance and the part of the body. PMID:12214760

  17. MERLIN (Methane Remote Sensing Lidar Mission): an Overview

    NASA Astrophysics Data System (ADS)

    Pierangelo, C.; Millet, B.; Esteve, F.; Alpers, M.; Ehret, G.; Flamant, P.; Berthier, S.; Gibert, F.; Chomette, O.; Edouart, D.; Deniel, C.; Bousquet, P.; Chevallier, F.

    2016-06-01

    The Methane Remote Sensing Lidar Mission (MERLIN), currently in phase B, is a joint cooperation between France and Germany on the development, launch and operation of a methane (CH4) monitoring satellite. MERLIN is focused on global measurements of the spatial and temporal gradients of atmospheric CH4, the second most anthropogenic gas, with a precision and accuracy sufficient to constrain Methane fluxes significantly better than with the current observation network. For the first time, measurements of atmospheric composition will be performed from space thanks to an IPDA (Integrated Path Differential Absorption) LIDAR (Light Detecting And Ranging). This payload is under the responsibility of the German space agency (DLR), while the platform (MYRIADE Evolutions product line) is developed by the French space agency (CNES). The IPDA technique relies on DIAL (Differential Absorption LIDAR) measurements using a pulsed laser emitting at two wavelengths, one wavelength accurately locked on a spectral feature of the methane absorption line, and the other wavelength free from absorption to be used as reference. This technique enables measurements in all seasons, at all latitudes. It also guarantees almost no contamination by aerosols or water vapour cross-sensitivity, and thus has the advantage of an extremely low level of systematic error on the dry-air column mixing ratio of CH4.

  18. High-Energy X-ray Absorption Diagnostics as an Experimental Combustion Technique

    NASA Astrophysics Data System (ADS)

    Dunnmon, Jared; Sobhani, Sadaf; Hinshaw, Waldo; Fahrig, Rebecca; Ihme, Matthias

    2015-11-01

    X-ray diagnostics such as X-ray Computed Tomography (XCT) have recently been utilized for measurement of scalar concentration fields in gas-phase flow phenomena. In this study, we apply high-energy X-ray absorption techniques to visualize a laboratory-scale flame via fluoroscopic measurements by using krypton as a radiodense tracer media. Advantages of X-ray absorption diagnostics in a combustion context, including application to optically inaccessible environments and lack of ambient photon interference, are demonstrated. Analysis methods and metrics for extracting physical insights from these data are presented. The accuracy of the diagnostic is assessed via comparison to known results from canonical flame configurations, and the potential for further applications is discussed. Support from the NDSEG fellowship, Bosch, and NASA are gratefully acknolwedged.

  19. Entrainment Heat Flux Computed with Lidar and Wavelet Technique in Buenos Aires During Last Chaitén Volcano Eruption

    NASA Astrophysics Data System (ADS)

    Pawelko, Ezequiel Eduardo; Salvador, Jacobo Omar; Ristori, Pablo Roberto; Pallotta, Juan Vicente; Otero, Lidia Ana; Quel, Eduardo Jaime

    2016-06-01

    At Lidar Division of CEILAP (CITEDEF-CONICET) a multiwavelength Raman-Rayleigh lidar optimized to measure the atmospheric boundary layer is being operated. This instrument is used for monitoring important aerosol intrusion events in Buenos Aires, such as the arrival of volcanic ashes from the Chaitén volcano eruption on May 2008. That was the first monitoring of volcanic ash with lidar in Argentina. In this event several volcanic ash plumes with high aerosol optical thickness were detected in the free atmosphere, affecting the visibility, surface radiation and therefore, the ABL evolution. In this work, the impact of ashes in entrainment flux ratio is studied. This parameter is obtained from the atmospheric boundary layer height and entrainment zone thickness using algorithms based on covariance wavelet transform.

  20. Vertical distribution of aerosol extinction cross section and inference of aerosol imaginary index in the troposphere by lidar technique

    NASA Technical Reports Server (NTRS)

    Spinhirne, J. D.; Reagan, J. A.; Herman, B. M.

    1980-01-01

    The paper reports on vertical profiles of aerosol extinction and backscatter in the troposphere which were obtained from multi zenith angle lidar measurements. It is reported that a direct slant path solution was found to be not possible due to horizontal inhomogeneity of the atmosphere. Attention is given to the use of a regression analysis with respect to zenith angle for a layer integration of the angle dependent lidar equation in order to determine the optical thickness and aerosol extinction-to-backscatter ratio for defined atmospheric layers and the subsequent evaluation of cross-section profiles.

  1. Atmospheric pre-corrected differential absorption techniques to retrieve columnar water vapor: Theory and simulations

    SciTech Connect

    Borel, C.C.; Schlaepfer, D.

    1996-03-01

    Two different approaches exist to retrieve columnar water vapor from imaging spectrometer data: (1) Differential absorption techniques based on: (a) Narrow-Wide (N/W) ratio between overlapping spectrally wide and narrow channels (b) Continuum Interpolated Band Ratio (CIBR) between a measurement channel and the weighted sum of two reference channels; and (2) Non-linear fitting techniques which are based on spectral radiative transfer calculations. The advantage of the first approach is computational speed and of the second, improved retrieval accuracy. Our goal was to improve the accuracy of the first technique using physics based on radiative transfer. Using a modified version of the Duntley equation, we derived an {open_quote}Atmospheric Pre-corrected Differential Absorption{close_quote} (APDA) technique and described an iterative scheme to retrieve water vapor on a pixel-by-pixel basis. Next we compared both, the CIBR and the APDA using the Duntley equation for MODTRAN3 computed irradiances, transmissions and path radiance (using the DISORT option). This simulation showed that the CIBR is very sensitive to reflectance effects and that the APDA performs much better. An extensive data set was created with the radiative transfer code 6S over 379 different ground reflectance spectra. The calculated relative water vapor error was reduced significantly for the APDA. The APDA technique had about 8% (vs. over 35% for the CIBR) of the 379 spectra with a relative water vapor error of greater than {+-}5%. The APDA has been applied to 1991 and 1995 AVIRIS scenes which visually demonstrate the improvement over the CIBR technique.

  2. Intercomparing CO2 amounts from dispersion modeling, 1.6 μm differential absorption lidar and open path FTIR at a natural CO2 release at Caldara di Manziana, Italy

    NASA Astrophysics Data System (ADS)

    Queißer, M.; Granieri, D.; Burton, M.; La Spina, A.; Salerno, G.; Avino, R.; Fiorani, L.

    2015-04-01

    We intercompare results of three independent approaches to quantify a vented CO2 release at a strongly non-uniform CO2 Earth degassing at Caldara di Manziana, central Italy. An integrated path differential absorption lidar prototype and a commercial open path FTIR system were measuring column averaged CO2 concentrations in parallel at two different paths. An Eulerian gas dispersion model simulated 3-D CO2 concentration maps in the same area, using in situ CO2 flux input data acquired at 152 different points. Local processes the model does not account for, such as small-scale and short-lived wind eddies, govern CO2 concentrations in the instrument measurement paths. The model, on the other hand, also considers atmospheric effects that are out of the field of view of the instruments. Despite this we find satisfactory agreement between modeled and measured CO2 concentrations under certain meteorological conditions. Under these conditions the results suggest that an Eulerian dispersion model and optical remote sensing can be used as an integrated, complementary monitoring approach for CO2 hazard or leakage assessment. Furthermore, the modeling may assist in evaluating CO2 sensing surveys in the future. CO2 column amounts from differential absorption lidar are in line with those from FTIR for both paths with a mean residual of the time series of 44 and 34 ppm, respectively. This experiment is a fundamental step forward in the deployment of the differential absorption lidar prototype as a highly portable active remote sensing instrument probing vented CO2 emissions, including volcanoes.

  3. Comparison of Lidar Methods for Remote Measurement of Air Pollutants

    NASA Technical Reports Server (NTRS)

    Wright, M. L.; Proctor, E. K.; Liston, E. M.

    1973-01-01

    This paper presents quantitative comparisons of several single-ended lidar techniques for the remote measurement of gaseous pollutants. These techniques are divided into two groups. The first group is based on the measurement of energy scattered directly by the gas of interest. The gaseous scattering processes considered are ordinary fluorescence, resonance fluorescence (also called resonance scattering), Raman scattering, and resonant (or nearly resonant) Raman scattering. The second group is based on the measurement of a characteristic differential absorption produced by the gas of interest at two discrete wavelengths, using energy scattered back toward the receiver by a remote reflector other than the gas of interest. The remote reflector may be intermixed with the gas of interest, as is the case with aerosols and atmospheric gases (principally nitrogen), or they may be fixed reflectors such as terrestrial objects or retroflectors. The detectability of a given material will depend on the magnitude and characteristics of the optical interaction with that material. The main characteristics of interest are the cross section, the response time, and the spectral response of the material relative to both the transmit and receive functions of the lidar. These characteristics and their implications for remote sensing will be reviewed for the four direct scatter processes and for the differential absorption technique. The characteristic behavior of the direct backscatter technique is different from the differential absorption technique with respect to sensitivity, concentration of material, and the effect of range. For these reasons, the direct backscatter processes cannot be compared directly to the differential absorption technique. The two techniques can be compared for specific material and system configurations, however. This paper describes specific lidar system configurations and gives the calculated performance level for these systems in both the direct

  4. Reconstructing landslide dynamics and characteristics using remote sensing data (photogrammetry, LiDAR and seismic data): comparison between different techniques and complementary data analysis

    NASA Astrophysics Data System (ADS)

    Torné, Marta; Guinau, Marta; Tapia, Mar; Perez, Cristina; Jesús Royan, Manuel; Echeverria, Anna; Roig, Pere; Suriñach, Emma

    2015-04-01

    The purpose of this study is to characterize the rock planar landslide that occurred in the village of La Riba (Catalonia) on May 5th 2013, using different techniques such as photogrammetry, terrestrial LiDAR data, and seismic data. Advantages and disadvantages of these techniques were evaluated. Back-analysis and characterization of landslides allow us to better understand their behaviour. This information could be used to protect areas affected by similar hazards. Remote techniques are an excellent tool to obtain data and to reduce the exposure of technicians in unstable (or inaccessible) areas. After the May 5th natural landslide, a controlled blasting was carried out to stabilize the slope. Using this programmed blasting as a benchmark, two photogrammetric models and two terrestrial LiDAR data models corresponding to the pre and post blast were made to compute the rock volume involved in the blast. The blasting process was recorded with two HD video cameras and by two temporary seismic stations deployed close to the site. Both the seismic and video records enabled us to reconstruct the details of the blasted landslide. The volumes obtained from seismic data were compared with the total volumes computed by LiDAR and photogrammetry. Moreover, information about the natural landslide was obtained from the records of a permanent seismic station 10 km from the site. Data such as the estimated fallen volume, the landslide mechanism and time of occurrence are information that would otherwise not be obtained. Six discontinuity families were detected and characterized in the rock slope using the photogrammetric and LiDAR models with a software developed by the Institut de Recerca de Geomodels of the Universitat de Barcelona. Similar results were obtained from the two models, but the higher point density of the LiDAR data enabled us to detect more discontinuity surfaces and in greater detail. The volume involved in the blast was calculated using two methods: 1) the

  5. Ground-based, integrated path differential absorption LIDAR measurement of CO2, CH4, and H2O near 1.6  μm.

    PubMed

    Wagner, Gerd A; Plusquellic, David F

    2016-08-10

    A ground-based, integrated path, differential absorption light detection and ranging (IPDA LIDAR) system is described and characterized for a series of nighttime studies of CO2, CH4, and H2O. The transmitter is based on an actively stabilized, continuous-wave, single-frequency external-cavity diode laser (ECDL) operating from 1.60 to 1.65 μm. The fixed frequency output of the ECDL is microwave sideband tuned using an electro-optical phase modulator driven by an arbitrary waveform generator and filtered using a confocal cavity to generate a sequence of 123 frequencies separated by 300 MHz. The scan sequence of single sideband frequencies of 600 ns duration covers a 37 GHz region at a spectral scan rate of 10 kHz (100 μs per scan). Simultaneously, an eye-safe backscatter LIDAR system at 1.064 μm is used to monitor the atmospheric boundary layer. IPDA LIDAR measurements of the CO2 and CH4 dry air mixing ratios are presented in comparison with those from a commercial cavity ring-down (CRD) instrument. Differences between the IPDA LIDAR and CRD concentrations in several cases appear to be well correlated with the atmospheric aerosol structure from the backscatter LIDAR measurements. IPDA LIDAR dry air mixing ratios of CO2 and CH4 are determined with fit uncertainties of 2.8 μmol/mol (ppm) for CO2 and 22 nmol/mol (ppb) for CH4 over 30 s measurement periods. For longer averaging times (up to 1200 s), improvements in these detection limits by up to 3-fold are estimated from Allan variance analyses. Two sources of systematic error are identified and methods to remove them are discussed, including speckle interference from wavelength decorrelation and the seed power dependence of amplified spontaneous emission. Accuracies in the dry air retrievals of CO2 and CH4 in a 30 s measurement period are estimated at 4 μmol/mol (1% of ambient levels) and 50

  6. Ground-based, integrated path differential absorption LIDAR measurement of CO2, CH4, and H2O near 1.6  μm.

    PubMed

    Wagner, Gerd A; Plusquellic, David F

    2016-08-10

    A ground-based, integrated path, differential absorption light detection and ranging (IPDA LIDAR) system is described and characterized for a series of nighttime studies of CO2, CH4, and H2O. The transmitter is based on an actively stabilized, continuous-wave, single-frequency external-cavity diode laser (ECDL) operating from 1.60 to 1.65 μm. The fixed frequency output of the ECDL is microwave sideband tuned using an electro-optical phase modulator driven by an arbitrary waveform generator and filtered using a confocal cavity to generate a sequence of 123 frequencies separated by 300 MHz. The scan sequence of single sideband frequencies of 600 ns duration covers a 37 GHz region at a spectral scan rate of 10 kHz (100 μs per scan). Simultaneously, an eye-safe backscatter LIDAR system at 1.064 μm is used to monitor the atmospheric boundary layer. IPDA LIDAR measurements of the CO2 and CH4 dry air mixing ratios are presented in comparison with those from a commercial cavity ring-down (CRD) instrument. Differences between the IPDA LIDAR and CRD concentrations in several cases appear to be well correlated with the atmospheric aerosol structure from the backscatter LIDAR measurements. IPDA LIDAR dry air mixing ratios of CO2 and CH4 are determined with fit uncertainties of 2.8 μmol/mol (ppm) for CO2 and 22 nmol/mol (ppb) for CH4 over 30 s measurement periods. For longer averaging times (up to 1200 s), improvements in these detection limits by up to 3-fold are estimated from Allan variance analyses. Two sources of systematic error are identified and methods to remove them are discussed, including speckle interference from wavelength decorrelation and the seed power dependence of amplified spontaneous emission. Accuracies in the dry air retrievals of CO2 and CH4 in a 30 s measurement period are estimated at 4 μmol/mol (1% of ambient levels) and 50

  7. An experimental/analytical program to assess the utility of lidar for pollution monitoring

    NASA Technical Reports Server (NTRS)

    Mills, F. S.; Allen, R. J.; Butler, C. F.; Kindle, E. C.

    1978-01-01

    The development and demonstration of lidar techniques for the remote measurement of atmospheric constituents and transport processes in the lower troposphere was carried out. Particular emphasis was given to techniques for monitoring SO2 and particulates, the principal pollutants in power plant and industrial plumes. Data from a plume dispersion study conducted in Maryland during September and October 1976 were reduced, and a data base was assembled which is available to the scientific community for plume model verification. A UV Differential Absorption Lidar (DIAL) was built, and preliminary testing was done.

  8. Lidar Remote Sensing for Industry and Environment Monitoring

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N. (Editor); Itabe, Toshikazu (Editor); Sugimoto, Nobuo (Editor)

    2000-01-01

    Contents include the following: 1. Keynote paper: Overview of lidar technology for industrial and environmental monitoring in Japan. 2. lidar technology I: NASA's future active remote sensing mission for earth science. Geometrical detector consideration s in laser sensing application (invited paper). 3. Lidar technology II: High-power femtosecond light strings as novel atmospheric probes (invited paper). Design of a compact high-sensitivity aerosol profiling lidar. 4. Lasers for lidars: High-energy 2 microns laser for multiple lidar applications. New submount requirement of conductively cooled laser diodes for lidar applications. 5. Tropospheric aerosols and clouds I: Lidar monitoring of clouds and aerosols at the facility for atmospheric remote sensing (invited paper). Measurement of asian dust by using multiwavelength lidar. Global monitoring of clouds and aerosols using a network of micropulse lidar systems. 6. Troposphere aerosols and clouds II: Scanning lidar measurements of marine aerosol fields at a coastal site in Hawaii. 7. Tropospheric aerosols and clouds III: Formation of ice cloud from asian dust particles in the upper troposphere. Atmospheric boundary layer observation by ground-based lidar at KMITL, Thailand (13 deg N, 100 deg. E). 8. Boundary layer, urban pollution: Studies of the spatial correlation between urban aerosols and local traffic congestion using a slant angle scanning on the research vessel Mirai. 9. Middle atmosphere: Lidar-observed arctic PSC's over Svalbard (invited paper). Sodium temperature lidar measurements of the mesopause region over Syowa Station. 10. Differential absorption lidar (dIAL) and DOAS: Airborne UV DIAL measurements of ozone and aerosols (invited paper). Measurement of water vapor, surface ozone, and ethylene using differential absorption lidar. 12. Space lidar I: Lightweight lidar telescopes for space applications (invited paper). Coherent lidar development for Doppler wind measurement from the International Space

  9. Progress Toward an Autonomous Field Deployable Diode Laser Based Differential Absorption Lidar (DIAL) for Profiling Water Vapor in the Lower Troposphere

    NASA Astrophysics Data System (ADS)

    Repasky, K. S.; Spuler, S.; Nehrir, A. R.; Moen, D.

    2013-12-01

    Water vapor is the most dominant greenhouse gas in the atmosphere and plays an important role in many key atmospheric processes associated with both weather and climate. Water vapor is highly variable in space and time due to large scale transport and biosphere-atmosphere interactions. Having long-term, high-resolution, vertical profiles of water vapor will help to better understand the water vapor structure and variability and its associated impact on weather and climate. A diode laser based differential absorption lidar (DIAL) for full-time water vapor and aerosol profiling in the lower troposphere has been demonstrated at Montana State University. This prototype instrument has the potential to form the basis of a ground based network of eye-safe autonomous instruments that can provide important information on the spatial and temporal variability of water vapor in the lower troposphere. To achieve this potential, major improvements to the prototype instrument need to be implemented and demonstrated including developing a laser transmitter capable of long term operation and modifying the optical receiver to make measurement below 0.5 km. During the past year, work on incorporating a new laser transmitter based on two distributed Bragg reflector (DBR) diode lasers, one operating at the on-line/side-line wavelength and the second operating at the off-line wavelength to injection seed a tapered semiconductor optical amplifier (TSOA) in a master oscillator power amplifier (MOPA) configuration has been completed. Recent work on the optical receiver is driven by the fact that the majority of the atmospheric water vapor resides below 2 km. The current single channel DIAL receiver has a narrow field of view and does not come in to full overlap until approximately 2 km. A two channel DIAL receiver has been designed that will allow the DIAL to achieve full overlap at ranges of less the 0.5 km providing significant improvement to the instrument performance. A discussion of

  10. Algorithm improvement and validation of National Institute for Environmental Studies ozone differential absorption lidar at the Tsukuba Network for Detection of Stratospheric Change complementary station.

    PubMed

    Park, Chan Bong; Nakane, Hideaki; Sugimoto, Nobuo; Matsui, Ichiro; Sasano, Yasuhiro; Fujinuma, Yasumi; Ikeuchi, Izumi; Kurokawa, Jun-Ichi; Furuhashi, Noritaka

    2006-05-20

    Recently, a data processing and retrieval algorithm (version 2) for ozone, aerosol, and temperature lidar measurements was developed for an ozone lidar system at the National Institute for Environmental Studies (NIES) in Tsukuba (36 degrees N,140 degrees E), Japan. A method for obtaining the aerosol boundary altitude and the aerosol extinction-to-backscatter ratio in the version 2 algorithm enables a more accurate determination of the vertical profiles of aerosols and a more accurate correction of the systematic errors caused by aerosols in the vertical profile of ozone. Improvements in signal processing are incorporated for the correction of systematic errors such as the signal-induced noise and the dead-time effect. The mean vertical ozone profiles of the NIES ozone lidar were compared with those of the Stratospheric Aerosol and Gas Experiment II (SAGE II); they agreed well within a 5% relative difference in the 20-40 km altitude range and within 10% up to 45 km. The long-term variations in the NIES ozone lidar also showed good coincidence with the ozonesonde and SAGE II at 20, 25, 30, and 35 km. The temperatures retrieved from the NIES ozone lidar and those given by the National Center for Environmental Prediction agreed within 7 K in the 35-50 km range.

  11. Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

    PubMed Central

    Carriles, Ramón; Schafer, Dawn N.; Sheetz, Kraig E.; Field, Jeffrey J.; Cisek, Richard; Barzda, Virginijus; Sylvester, Anne W.; Squier, Jeffrey A.

    2009-01-01

    We review the current state of multiphoton microscopy. In particular, the requirements and limitations associated with high-speed multiphoton imaging are considered. A description of the different scanning technologies such as line scan, multifoci approaches, multidepth microscopy, and novel detection techniques is given. The main nonlinear optical contrast mechanisms employed in microscopy are reviewed, namely, multiphoton excitation fluorescence, second harmonic generation, and third harmonic generation. Techniques for optimizing these nonlinear mechanisms through a careful measurement of the spatial and temporal characteristics of the focal volume are discussed, and a brief summary of photobleaching effects is provided. Finally, we consider three new applications of multiphoton microscopy: nonlinear imaging in microfluidics as applied to chemical analysis and the use of two-photon absorption and self-phase modulation as contrast mechanisms applied to imaging problems in the medical sciences. PMID:19725639

  12. Laser Frequency Stabilization for Coherent Lidar Applications using Novel All-Fiber Gas Reference Cell Fabrication Technique

    NASA Technical Reports Server (NTRS)

    Meras, Patrick, Jr.; Poberezhskiy, Ilya Y.; Chang, Daniel H.; Levin, Jason; Spiers, Gary D.

    2008-01-01

    Compact hollow-core photonic crystal fiber (HC-PCF)gas frequency reference cell was constructed using a novel packaging technique that relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers. The use of this gas cell for laser frequency stabilization was demonstrated by locking a tunable diode laser to the center of the P9 line from the (nu)1+(nu)3 band of acetylene with RMS frequency error of 2.06 MHz over 2 hours. This effort was performed in support of a task to miniaturize the laser frequency stabilization subsystem of JPL/LMCT Laser Absorption Spectrometer (LAS) instrument.

  13. Lidar system for remote environmental studies.

    PubMed

    Gondal, M A; Mastromarino, J

    2000-10-01

    Light detection and ranging (lidar) system has been developed for remote monitoring of the environment. The system has been tested for measuring the size of clouds and by measurement of differential absorption due to pollutant gases like NO(2) and SO(2) in a cell. The lidar measurements revealed strong scattered signals from clouds situated around 11 km above the earth surface. The lidar data indicates that cloud thickness varied from 0.8 to 3.6 km at various times.

  14. Autonomous Ozone and Aerosol Lidar Platform: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Strawbridge, K. B.

    2014-12-01

    Environment Canada is developing an autonomous tropospheric ozone and aerosol lidar system for deployment in support of short-term field studies. Tropospheric ozone and aerosols (PM10 and PM2.5) are important atmospheric constituents in low altitude pollution affecting human health and vegetation. Ozone is photo-chemically active with nitrogen oxides and can have a distinct diurnal variability. Aerosols contribute to the radiative budget, are a tracer for pollution transport, undergo complex mixing, and contribute to visibility and cloud formation. This particular instrument will employ two separate lidar transmitter and receiver assemblies. The tropospheric ozone lidar, based on the differential absorption lidar (DIAL) technique, uses the fourth harmonics of a Nd:YAG laser directed into a CO2 Raman cell to produce 276 nm, 287nm and 299 nm (first to third Stokes lines) output wavelengths. The aerosol lidar is based on the 3+2 design using a tripled Nd:YAG to output 355 nm, 532 nm and 1064nm wavelengths. Both lidars will be housed in a modified cargo trailer allowing for easy deployment to remote areas. The unit can be operated and monitored 24 hours a day via an internet link and requires an external power source. Simultaneous ozone and aerosol lidar measurements will provide the vertical context necessary to understand the complex mixing and transformation of pollutants - particularly when deployed near other ground-based in-situ sensors. Preliminary results will be shown from a summer field study at the Centre For Atmospheric Research Experiments (CARE).

  15. Lidar detection of carbon dioxide in volcanic plumes

    NASA Astrophysics Data System (ADS)

    Fiorani, Luca; Santoro, Simone; Parracino, Stefano; Maio, Giovanni; Del Franco, Mario; Aiuppa, Alessandro

    2015-06-01

    Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidar has been undertaken at the Diagnostics and Metrology Laboratory (UTAPRAD-DIM) of the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high spatial and temporal resolution. Two differential absorption lidar instruments will be presented in this paper: BILLI (BrIdge voLcanic LIdar), based on injection seeded Nd:YAG laser, double grating dye laser, difference frequency mixing (DFM) and optical parametric amplifier (OPA), and VULLI (VULcamed Lidar), based on injection seeded Nd:YAG laser and optical parametric oscillator (OPO). The first one is funded by the ERC (European Research Council) project BRIDGE and the second one by the ERDF (European Regional Development Fund) project VULCAMED. While VULLI has not yet been tested in a volcanic site, BILLI scanned the gas emitted by Pozzuoli Solfatara (Campi Flegrei volcanic area, Naples, Italy) during a field campaign carried out from 13 to 17 October 2014. Carbon dioxide concentration maps were retrieved remotely in few minutes in the crater area. Lidar measurements were in good agreement with well-established techniques, based on different operating principles. To our knowledge, it is the first time that carbon dioxide in a volcanic plume is retrieved by lidar, representing the first direct measurement of this kind ever performed on an active volcano and showing the high potential of laser remote sensing in geophysical research.

  16. Performance verification of a LIF-LIDAR technique for stand-off detection and classification of biological agents

    NASA Astrophysics Data System (ADS)

    Wojtanowski, Jacek; Zygmunt, Marek; Muzal, Michał; Knysak, Piotr; Młodzianko, Andrzej; Gawlikowski, Andrzej; Drozd, Tadeusz; Kopczyński, Krzysztof; Mierczyk, Zygmunt; Kaszczuk, Mirosława; Traczyk, Maciej; Gietka, Andrzej; Piotrowski, Wiesław; Jakubaszek, Marcin; Ostrowski, Roman

    2015-04-01

    LIF (laser-induced fluorescence) LIDAR (light detection and ranging) is one of the very few promising methods in terms of long-range stand-off detection of air-borne biological particles. A limited classification of the detected material also appears as a feasible asset. We present the design details and hardware setup of the developed range-resolved multichannel LIF-LIDAR system. The device is based on two pulsed UV laser sources operating at 355 nm and 266 nm wavelength (3rd and 4th harmonic of Nd:YAG, Q-switched solid-state laser, respectively). Range-resolved fluorescence signals are collected in 28 channels of compound PMT sensor coupled with Czerny-Turner spectrograph. The calculated theoretical sensitivities are confronted with the results obtained during measurement field campaign. Classification efforts based on 28-digit fluorescence spectral signatures linear processing are also presented.

  17. New Examination of the Traditional Raman Lidar Technique II: Evaluating the Ratios for Water Vapor and Aerosols

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.

    2003-01-01

    In a companion paper, the temperature dependence of Raman scattering and its influence on the Raman and Rayleigh-Mie lidar equations was examined. New forms of the lidar equation were developed to account for this temperature sensitivity. Here those results are used to derive the temperature dependent forms of the equations for the water vapor mixing ratio, aerosol scattering ratio, aerosol backscatter coefficient, and extinction to backscatter ratio (Sa). The error equations are developed, the influence of differential transmission is studied and different laser sources are considered in the analysis. The results indicate that the temperature functions become significant when using narrowband detection. Errors of 5% and more can be introduced in the water vapor mixing ratio calculation at high altitudes and errors larger than 10% are possible for calculations of aerosol scattering ratio and thus aerosol backscatter coefficient and extinction to backscatter ratio.

  18. The 21-SPONGE HI Absorption Survey I: Techniques and Initial Results

    NASA Astrophysics Data System (ADS)

    Murray, Claire E.; Stanimirović, Snežana; Goss, W. M.; Dickey, John M.; Heiles, Carl; Lindner, Robert R.; Babler, Brian; Pingel, Nickolas M.; Lawrence, Allen; Jencson, Jacob; Hennebelle, Patrick

    2015-05-01

    We present methods and results from “21 cm Spectral Line Observations of Neutral Gas with the EVLA” (21-SPONGE), a large survey for Galactic neutral hydrogen (H i) absorption with the Karl G. Jansky Very Large Array (VLA). With the upgraded capabilities of the VLA, we reach median rms noise in optical depth of {{σ }τ }=9× {{10}-4} per 0.42 km {{s}-1} channel for the 31 sources presented here. Upon completion, 21-SPONGE will be the largest H i absorption survey with this high sensitivity. We discuss the observations and data reduction strategies, as well as line fitting techniques. We prove that the VLA bandpass (BP) is stable enough to detect broad, shallow lines associated with warm H i, and we show that BP observations can be combined in time to reduce spectral noise. In combination with matching H i emission profiles from the Arecibo Observatory (∼ 3.‧5 angular resolution), we estimate excitation (or spin) temperatures (Ts) and column densities for Gaussian components fitted to sightlines along which we detect H i absorption (30/31). We measure temperatures up to {{T}s}∼ 1500 K for individual lines, showing that we can probe the thermally unstable interstellar medium (ISM) directly. However, we detect fewer of these thermally unstable components than expected from previous observational studies. We probe a wide range in column density between ∼ {{10}16} and \\gt {{10}21} c{{m}-2} for individual H i clouds. In addition, we reproduce the trend between cold gas fraction and average Ts found by the Kim et al. synthetic observations of a hydrodynamic ISM simulation. Finally, we compare methods for estimating Ts using H i observations.

  19. Evaluation of iron-containing carbon nanotubes by near edge X-ray absorption technique

    NASA Astrophysics Data System (ADS)

    Osorio, A. G.; Bergmann, C. P.

    2015-10-01

    The synthesis of carbon nanotubes (CNTs) via Chemical Vapor Deposition method with ferrocene results in CNTs filled with Fe-containing nanoparticles. The present work proposes a novel route to characterize the Fe phases in CNTs inherent to the synthesis process. CNTs were synthesized and, afterwards, the CNTs were heat treated at 1000 °C for 20 min in an inert atmosphere during a thermogravimetric experiment. X-Ray Absorption Spectroscopy (XAS) experiments were performed on the CNTs before and after the heat treatment and, also, during the heat treatment, e.g., in situ tests were performed while several Near-Edge X-Ray Absorption (XANES) spectra were collected during the heating of the samples. The XAS technique was successfully applied to evaluate the phases encapsulated by CNTs. Phase transformations of the Fe-based nanoparticles were also observed from iron carbide to metallic iron when the in situ experiments were performed. Results also indicated that the applied synthesis method guarantees that Fe phases are not oxidize. In addition, the results show that heat treatment under inert atmosphere can control which phase remains encapsulated by the CNTs.

  20. Fast-response, high-precision carbon monoxide sensor using a tunable diode laser absorption technique

    NASA Technical Reports Server (NTRS)

    Sachse, Glen W.; Hill, Gerald F.; Wade, Larry O.; Perry, Murray G.

    1987-01-01

    A tunable diode laser instrument, denoted as DACOM (Differential Absorption CO Measurement), has been developed to meet the fast-response, high-precision CO measurement needs of the GTE (Global Tropospheric Experiment) program. Under the GTE program, DACOM participated in the three field missions of CITE 1 (Chemical Instrumentation Test and Evaluation 1), a project involving the intercomparison of trace gas measurement techniques. DACOM performance, including analyses of measurement error sources, is discussed for the ground-based mission at Wallops Island, VA (summer 1983), and two missions on the NASA CV-990 (fall 1983 and spring 1984). Examples of fast-response (about 1 s), high-precision (+ or - 1 part per billion by volume, + or - 1.5 percent of reading) airborne data are included to illustrate the capability of this instrument.

  1. Spectral fluorescence signature techniques and absorption measurements for continuous monitoring of biofuel-producing microalgae cultures

    NASA Astrophysics Data System (ADS)

    Martín de la Cruz, M. C.; Gonzalez Vilas, L.; Yarovenko, N.; Spyrakos, E.; Torres Palenzuela, J. M.

    2013-08-01

    Biofuel production from microalgae can be both sustainable and economically viable. Particularly in the case of algal growth in wastewater an extra benefit is the removal or biotransformation of pollutants from these types of waters. A continuous monitoring system of the microalgae status and the concentration of different wastewater contaminants could be of great help in the biomass production and the water characterisation. In this study we present a system where spectral fluorescence signature (SFS) techniques are used along with absorption measurements to monitor microalgae cultures in wastewater and other mediums. This system aims to optimise the microalgae production for biofuel applications or other uses and was developed and tested in prototype indoor photo-bioreactors at the University of Vigo. SFS techniques were applied using the fluorescence analyser INSTAND-SCREENER developed by Laser Diagnostic Instruments AS. INSTAND-SCREENER permits wavelength scanning in two modes, one in UV and another in VIS. In parallel, it permits the on-line monitoring and rapid analysis of both water quality and phytoplankton status without prior treatment of the sample. Considering that different contaminants and microalgae features (density, status etc.) have different spectral signatures of fluorescence and absorption properties, it is possible to characterise them developing classification libraries. Several algorithms were used for the classification. The implementation of this system in an outdoor raceway reactor in a Spanish wastewater treatment plant is also discussed. This study was part of the Project EnerBioAlgae (http://www.enerbioalgae.com/), which was funded by the Interreg SUDOE and led by the University of Vigo.

  2. Remote sensing measurements of the CO2 mixing ratio in the planetary boundary layer using cloud slicing with airborne lidar

    NASA Astrophysics Data System (ADS)

    Ramanathan, Anand K.; Mao, Jianping; Abshire, James B.; Allan, Graham R.

    2015-03-01

    We have measured the CO2 volume mixing ratio (VMR) within the planetary boundary layer (PBL) using cloud slicing with an airborne pulsed integrated path differential absorption (IPDA) lidar from flight altitudes of up to 13 km. During a flight over Iowa in summer 2011, simultaneous measurement of the optical range and CO2 absorption to clouds and the ground were made using time-resolved detection of pulse echoes from each scattering surface. We determined the CO2 absorption in the PBL by differencing the two lidar-measured absorption line shapes, one to a broken shallow cumulus cloud layer located at the top of the PBL and the other to the ground. Solving for the CO2 VMR in the PBL and that of the free troposphere, we measured a ≈15 ppm (4%) drawdown in the PBL. Both CO2 VMRs were within ≈3 ppm of in situ CO2 profile measurements. We have also demonstrated cloud slicing using scatter from thin, diffuse cirrus clouds and cumulus clouds, which allowed solving for the CO2 VMR for three vertical layers. The technique and retrieval algorithm are applicable to a space-based lidar instrument as well as to lidar IPDA measurements of other trace gases. Thus, lidar cloud slicing also offers promise toward space-based remote sensing of vertical trace gas profiles in the atmosphere using a variety of clouds.

  3. Element-selective trace detection of toxic species in environmental samples using chromatographic techniques and derivative diode laser absorption spectrometry

    NASA Astrophysics Data System (ADS)

    Koch, J.; Zybin, A.; Niemax, K.

    1998-10-01

    Very sensitive laser absorption techniques based on a double-beam scheme with logarithmic processing of the detector signals and wavelength modulation of laser diodes are presented. Detection limits equivalent to 10-7 absorption per square root of detection bandwidth are obtained if sufficient laser power is available and if the absorption is also subject to additional modulation. The analytical versatility of these techniques is demonstrated by quantitative analysis of very low concentrations of (i) Cr(VI) species in tap water and (ii) chlorinated poly-aromatics (chlorophenols) in plant extracts, both after chromatographic separation. The atomic absorption measurements were performed in an air-acetylene flame (Cr) and in a low-pressure microwave-induced plasma (chlorophenols).

  4. Aerosol Properties From Combined Oxygen A Band Radiances and Lidar

    NASA Technical Reports Server (NTRS)

    Winker, Dave; Zhai, Peng-Wang; Hu, Yongxiang

    2015-01-01

    We have developed a new aerosol retrieval technique based on combing high-resolution A band spectra with lidar profiles. Our goal is the development of a technique to retrieve aerosol absorption, one of the critical parameters affecting the global radiation budget and one which is currently poorly constrained by satellite measurements. Our approach relies on two key factors: 1) the use of high spectral resolution (17,000:1) measurements which resolve the A-band line structure, and 2) the use of co-located lidar profile measurements to constrain the vertical distribution of scatterers in the forward model. The algorithm has been developed to be applied to observations from the CALIPSO and OCO-2 satellites, flying in formation as part of the A-train constellation. We describe the approach and present simulated retrievals to illustrate performance potential.

  5. Can CO2 Turbulent Flux Be Measured by Lidar? A Preliminary Study

    NASA Technical Reports Server (NTRS)

    Gilbert, Fabien; Koch, Grady; Beyon, Jeffrey Y.; Hilton, Timothy W.; Davis, Kenneth J.; Andrews, Arlyn; Flamant, Pierre H.; Singh, Upendra N.

    2011-01-01

    The vertical profiling ofCO2 turbulent fluxes in the atmospheric boundary layer (ABL) is investigated using a coherent differential absorption lidar (CDIAL) operated nearby a tall tower in Wisconsin during June 2007. A CDIAL can perform simultaneous range-resolved CO2 DIAL and velocity measurements. The lidar eddy covariance technique is presented. The aims of the study are (i) an assessment of performance and current limitation of available CDIAL for CO2 turbulent fluxes and (ii) the derivation of instrument specifications to build a future CDIAL to perform accurate range-resolved CO2 fluxes. Experimental lidar CO2 mixing ratio and vertical velocity profiles are successfully compared with in situ sensors measurements. Time and space integral scales of turbulence in the ABL are addressed that result in limitation for time averaging and range accumulation. A first attempt to infer CO2 fluxes using an eddy covariance technique with currently available 2-mm CDIAL dataset is reported.

  6. Retrieving seawater-backscattering profiles from coupling Raman and elastic lidar data.

    PubMed

    Malinka, Aleksey V; Zege, Eleonora P

    2004-07-01

    We propose a technique for retrieving seawater-backscattering profiles that is based on the joint use of elastic and Raman lidar returns. We suggest using two lidar channels: the Raman channel and the elastic channel with a light frequency equal to a half-sum of initial and Raman-shifted frequencies of the Raman channel. These specific wavelengths provide the same attenuation laws for elastic and Raman signals if absorption and scattering spectra can be approximated by a power law. In particular, seawater supplies such a possibility in the region of 400-500 nm if extremely bioproductive waters are not considered and the chlorophyll absorption peak at 440 nm does not come out of the background of dissolved organic matter absorption. With these specific initial wavelengths, the elastic and Raman lidar returns differ only in the backscattering coefficients. Because the Raman-backscattering coefficient is constant along the profile, the (elastic-to-Raman) ratio of these lidar returns directly produces the profile of the elastic-backscattering coefficient. This technique stays valid even under multiple-scattering conditions, which is of great importance for seawater sounding.

  7. Comparison of 2 micron Ho and 10 micron CO2 lidar for atmospheric backscatter and Doppler windshear detection

    NASA Technical Reports Server (NTRS)

    Killinger, Dennis

    1991-01-01

    The development of eye-safe, solid-state Lidar systems is discussed, with an emphasis on Coherent Doppler Lidar for Atmospheric Wind Measurements. The following subject areas are covered: tunable Ho DIAL (Differential Absorption Lidar)/lidar atmospheric measurements; atmospheric turbulence measurements and detector arrays; diurnal measurements of C(sub n)(sup 2) for KSC lidar measurements; and development of single-frequency Ho laser/lidar.

  8. Lidar sounding of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone

    2013-10-01

    Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

  9. Quantitative filter technique measurements of spectral light absorption by aquatic particles using a portable integrating cavity absorption meter (QFT-ICAM).

    PubMed

    Röttgers, Rüdiger; Doxaran, David; Dupouy, Cecile

    2016-01-25

    The accurate determination of light absorption coefficients of particles in water, especially in very oligotrophic oceanic areas, is still a challenging task. Concentrating aquatic particles on a glass fiber filter and using the Quantitative Filter Technique (QFT) is a common practice. Its routine application is limited by the necessary use of high performance spectrophotometers, distinct problems induced by the strong scattering of the filters and artifacts induced by freezing and storing samples. Measurements of the sample inside a large integrating sphere reduce scattering effects and direct field measurements avoid artifacts due to sample preservation. A small, portable, Integrating Cavity Absorption Meter setup (QFT-ICAM) is presented, that allows rapid measurements of a sample filter. The measurement technique takes into account artifacts due to chlorophyll-a fluorescence. The QFT-ICAM is shown to be highly comparable to similar measurements in laboratory spectrophotometers, in terms of accuracy, precision, and path length amplification effects. No spectral artifacts were observed when compared to measurement of samples in suspension, whereas freezing and storing of sample filters induced small losses of water-soluble pigments (probably phycoerythrins). Remaining problems in determining the particulate absorption coefficient with the QFT-ICAM are strong sample-to-sample variations of the path length amplification, as well as fluorescence by pigments that is emitted in a different spectral region than that of chlorophyll-a.

  10. Lidar remote sensing of tropospheric pollutants and trace gases - Programs of NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Browell, E. V.

    1978-01-01

    NASA Langley Research Center is engaged in a number of in-house and contracted programs to develop, evaluate, and apply lidar techniques to remote measurements of pollutant gases, trace molecules, and aerosols. The differential absorption lidar (DIAL) research programs include the development and evaluation of a UV DIAL system for remote measurements of SO2 and O3 concentrations and aerosol dispersion in urban and power-plant stack plumes, a near-IR DIAL system for vertical measurements of water vapor concentrations, and a high-power tunable IR DIAL system which will measure the concentration of gas species that have absorption features in the 1.4- to 4.4-micron wavelength range. The lidar programs which deal with aerosol measurements include the evaluation of a mobile ruby lidar system for use in plume dispersion model verification and the development of a high-spectral-resolution lidar system for measurement of aerosol extinction and backscattering coefficients. System characteristics and measurement sensitivities are discussed, and comparisons are made between simulations and experimental results.

  11. An adaptive computer vision technique for estimating the biomass and density of loblolly pine plantations using digital orthophotography and LiDAR imagery

    NASA Astrophysics Data System (ADS)

    Bortolot, Zachary J.

    Forests have been proposed as a means of reducing atmospheric carbon dioxide levels due to their ability to store carbon as biomass. To quantify the amount of atmospheric carbon sequestered by forests, biomass and density estimates are oven needed. This study develops, implements, and tests an individual tree-based algorithm for obtaining forest density and biomass using orthophotographs and small footprint LiDAR imagery. It was designed to work with a range of forests and image types without modification, which is accomplished by using generic properties of trees found in many types of images. Multiple parameters are employed to determine how these generic properties are used. To set these parameters, training data is used in conjunction with an optimization algorithm (a modified Nelder-Mead simplex algorithm or a genetic algorithm). The training data consist of small images in which density and biomass are known. A first test of this technique was performed using 25 circular plots (radius = 15 m) placed in young pine plantations in central Virginia, together with false color orthophotograph (spatial resolution = 0.5 m) or small footprint LiDAR (interpolated to 0.5 m) imagery. The highest density prediction accuracies (r2 up to 0.88, RMSE as low as 83 trees/ha) were found for runs where photointerpreted densities were used for training and testing. For tests run using density measurements made on the ground, accuracies were consistency higher for orthophotograph-based results than for LiDAR-based results, and were higher for trees with DBH ≥10cm than for trees with DBH ≥7 cm. Biomass estimates obtained by the algorithm using LiDAR imagery had a lower RMSE (as low as 15.6 t/ha) than most comparable studies. The correlations between the actual and predicted values (r2 up to 0.64) were lower than comparable studies, but were generally highly significant (p ≤ 0.05 or 0.01). In all runs there was no obvious sensitive to which training and testing data were

  12. Lidar applications to pollution studies.

    NASA Technical Reports Server (NTRS)

    Mccormick, M. P.; Fuller, W. H., Jr.

    1971-01-01

    This paper discusses the application of lidar (laser radar) to the measurement of air pollution. Lidar techniques and instrumentation utilizing elastic, Raman, and fluorescence scattering are discussed. Data showing measurements of the mixing of particulate pollutants in the atmosphere are presented. These data include: simultaneous two-wavelength results, isopleths showing the temporal dynamics of particulate mixing, measurements of the top of the earth's mixing layer, and measurements in a valley with restricted circulation and mixing. All measurements are compared with simultaneous radiosonde and/or aircraft-mounted temperature probe support. In addition, a second generation lidar system presently under development is described.

  13. Effect of nonlinear absorption on electric field applied lead chloride by Z-scan technique

    SciTech Connect

    Rejeena, I.; Lillibai,; Nampoori, V. P. N.; Radhakrishnan, P.; Rahimkutty, M. H.

    2014-10-15

    The preparation, spectral response and optical nonlinearity of gel grown lead chloride single crystals subjected to electric field of 20V using parallel plate arrangements have been investigated. Optical band gap of the samples were determined using linear absorption spectra. Open aperture z-scan was employed for the determination of nonlinear absorption coefficient of PbCl{sub 2} solution. The normalized transmittance curve exhibits a valley shows reverse saturable absorption. The non linear absorption at different input fluences were recorded using a single Gaussian laser beam in tight focus geometry. The RSA nature of the sample makes it suitable for optical limiting applications.

  14. Effect of nonlinear absorption on electric field applied lead chloride by Z-scan technique

    NASA Astrophysics Data System (ADS)

    Rejeena, I.; Lillibai, Rahimkutty, M. H.; Nampoori, V. P. N.; Radhakrishnan, P.

    2014-10-01

    The preparation, spectral response and optical nonlinearity of gel grown lead chloride single crystals subjected to electric field of 20V using parallel plate arrangements have been investigated. Optical band gap of the samples were determined using linear absorption spectra. Open aperture z-scan was employed for the determination of nonlinear absorption coefficient of PbCl2 solution. The normalized transmittance curve exhibits a valley shows reverse saturable absorption. The non linear absorption at different input fluences were recorded using a single Gaussian laser beam in tight focus geometry. The RSA nature of the sample makes it suitable for optical limiting applications.

  15. Photoacoustic technique for simultaneous measurements of thermal effusivity and absorptivity of pigments in liquid solution.

    PubMed

    Balderas-López, J A; Díaz-Reyes, J; Zelaya-Angel, O

    2011-12-01

    A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature.

  16. Improving LiDAR Data Post-Processing Techniques for Archaeological Site Management and Analysis: A Case Study from Canaveral National Seashore Park

    NASA Astrophysics Data System (ADS)

    Griesbach, Christopher

    Methods used to process raw Light Detection and Ranging (LiDAR) data can sometimes obscure the digital signatures indicative of an archaeological site. This thesis explains the negative effects that certain LiDAR data processing procedures can have on the preservation of an archaeological site. This thesis also presents methods for effectively integrating LiDAR with other forms of mapping data in a Geographic Information Systems (GIS) environment in order to improve LiDAR archaeological signatures by examining several pre-Columbian Native American shell middens located in Canaveral National Seashore Park (CANA).

  17. New Broadband LIDAR for Greenhouse Carbon Dioxide Gas Sensing in the Earth's Atmosphere

    NASA Technical Reports Server (NTRS)

    Georgieva, Elena; Heaps, William S.; Huang,Wen

    2011-01-01

    We present demonstration of a novel broadband lidar technique capable of dealing with the atmospherically induced variations in CO2 absorption using a Fabry-Perot based detector and a broadband laser. The Fabry-Perot solid etalon in the receiver part is tuned to match the wavelength of several CO2 absorption lines simultaneously. The broadband technique tremendously reduces the requirement for source wavelength stability, instead putting this responsibility on the Fabry- Perot based receiver. The instrument technology we are developing has a clear pathway to space and realistic potential to become a robust, low risk space measurement system.

  18. Lidar Measurements of the Stratosphere and Mesosphere at the Biejing Observatory

    NASA Astrophysics Data System (ADS)

    Du, Lifang; Yang, Guotao; Cheng, Xuewu; Wang, Jihong

    With the high precision and high spatial and temporal resolution, the lidar has become a powerful weapon of near space environment monitoring. This paper describes the development of the solid-state 532nm and 589nm laser radar, which were used to detect the wind field of Beijing stratosphere and mesopause field. The injection seeding technique and atomic absorption saturation bubble frequency stabilization method was used to obtain narrow linewidth of 532nm lidar, Wherein the laser pulse energy of 800mJ, repetition rate of 30Hz. The 589nm yellow laser achieved by extra-cavity sum-frequency mixing 1064nm and 1319nm pulse laser with KTP crystal. The base frequency of 1064nm and 1319nm laser adopted injection seeding technique and YAG laser amplification for high energy pulse laser. Ultimately, the laser pulse of 150mJ and the linewidth of 130MHz of 589nm laser was obtain. And after AOM crystal frequency shift, Doppler frequency discriminator free methods,achieved of the measuring of high-altitude wind. Both of 532nm and 589nm lidar system for engineering design of solid-state lidar provides a basis, and also provide a solid foundation for the development of all-solid-state wind lidar.

  19. Use of a Slope-Based Surface Matching Technique to Detect Landslide Movement in LiDAR Data

    NASA Astrophysics Data System (ADS)

    Streutker, D. R.; Glenn, N. F.; Thackray, G. D.

    2006-12-01

    A canyon-rim landslide near Salmon Falls Creek in southern Idaho was first reported in 1999. Due to the creation of a natural dam by the slide, a monitoring campaign was initiated to assess the potential for a possible catastrophic breech and downstream flooding. This monitoring campaign included two collections of high-resolution LiDAR (light detection and ranging) data. The collections were spaced three years apart, in 2002 and 2005, in order to detect morphological changes and determine movement within the landslide complex during that interval. The two data sets are compared using an iterative, slope-based surface matching algorithm. By comparing the spatial offset with the local slope and aspect, the three-dimensional shift correction can be predicted statistically. This method can be extended to incorporate higher order polynomial warping for an improved fit between the two surfaces. Areas of known change are masked out to prevent biasing the match, and least absolute deviation methods are incorporated. Change detection is accomplished by differencing the two matched surfaces. Examination of the difference product reveals that the upper body of the slide has dropped nearly 1 m during the three-year interval, while the toe has risen approximately 50 cm. Analysis of individual features on the main body indicates horizontal movement on the order of several dozen centimeters.

  20. Eye-Safe Lidar

    NASA Technical Reports Server (NTRS)

    Byer, Robert L.

    1989-01-01

    Laser infrared radar (lidar) undergoing development harmless to human eyes, consists almost entirely of solid-state components, and offers high range resolution. Operates at wavelength of about 2 micrometers. If radiation from such device strikes eye, almost completely absorbed by cornea without causing damage, even if aimed directly at eye. Continuous-wave light from laser oscillator amplified and modulated for transmission from telescope. Small portion of output of oscillator fed to single-mode fiber coupler, where mixed with return pulses. Intended for remote Doppler measurements of winds and differential-absorption measurements of concentrations of gases in atmosphere.

  1. Development and Deployment of a Compact Eye-Safe Scanning Differential absorption Lidar (DIAL) for Spatial Mapping of Carbon Dioxide for Monitoring/Verification/Accounting at Geologic Sequestration Sites

    SciTech Connect

    Repasky, Kevin

    2014-03-31

    A scanning differential absorption lidar (DIAL) instrument for monitoring carbon dioxide has been developed. The laser transmitter uses two tunable discrete mode laser diodes (DMLD) operating in the continuous wave (cw) mode with one locked to the online absorption wavelength and the other operating at the offline wavelength. Two in-line fiber optic switches are used to switch between online and offline operation. After the fiber optic switch, an acousto- optic modulator (AOM) is used to generate a pulse train used to injection seed an erbium doped fiber amplifier (EDFA) to produce eye-safe laser pulses with maximum pulse energies of 66 {micro}J, a pulse repetition frequency of 15 kHz, and an operating wavelength of 1.571 {micro}m. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a photo-multiplier tube (PMT) module operating in the photon counting mode. The DIAL instrument has been operated from a laboratory environment on the campus of Montana State University, at the Zero Emission Research Technology (ZERT) field site located in the agricultural research area on the western end of the Montana State University campus, and at the Big Sky Carbon Sequestration Partnership site located in north-central Montana. DIAL data has been collected and profiles have been validated using a co-located Licor LI-820 Gas Analyzer point sensor.

  2. Improving lidar turbulence estimates for wind energy

    NASA Astrophysics Data System (ADS)

    Newman, J. F.; Clifton, A.; Churchfield, M. J.; Klein, P.

    2016-09-01

    Remote sensing devices (e.g., lidars) are quickly becoming a cost-effective and reliable alternative to meteorological towers for wind energy applications. Although lidars can measure mean wind speeds accurately, these devices measure different values of turbulence intensity (TI) than an instrument on a tower. In response to these issues, a lidar TI error reduction model was recently developed for commercially available lidars. The TI error model first applies physics-based corrections to the lidar measurements, then uses machine-learning techniques to further reduce errors in lidar TI estimates. The model was tested at two sites in the Southern Plains where vertically profiling lidars were collocated with meteorological towers. Results indicate that the model works well under stable conditions but cannot fully mitigate the effects of variance contamination under unstable conditions. To understand how variance contamination affects lidar TI estimates, a new set of equations was derived in previous work to characterize the actual variance measured by a lidar. Terms in these equations were quantified using a lidar simulator and modeled wind field, and the new equations were then implemented into the TI error model.

  3. Lidar Observations of Atmospheric CO2 Column During 2014 Summer Flight Campaigns

    NASA Technical Reports Server (NTRS)

    Lin, Bing; Harrison, F. Wallace; Fan, Tai-Fang

    2015-01-01

    Advanced knowledge in atmospheric CO2 is critical in reducing large uncertainties in predictions of the Earth' future climate. Thus, Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) from space was recommended by the U.S. National Research Council to NASA. As part of the preparation for the ASCENDS mission, NASA Langley Research Center (LaRC) and Exelis, Inc. have been collaborating in development and demonstration of the Intensity-Modulated Continuous-Wave (IM-CW) lidar approach for measuring atmospheric CO2 column from space. Airborne laser absorption lidars such as the Multi-Functional Fiber Laser Lidar (MFLL) and ASCENDS CarbonHawk Experiment Simulator (ACES) operating in the 1.57 micron CO2 absorption band have been developed and tested to obtain precise atmospheric CO2 column measurements using integrated path differential absorption technique and to evaluate the potential of the space ASCENDS mission. This presentation reports the results of our lidar atmospheric CO2 column measurements from 2014 summer flight campaign. Analysis shows that for the 27 Aug OCO-2 under flight over northern California forest regions, significant variations of CO2 column approximately 2 ppm) in the lower troposphere have been observed, which may be a challenge for space measurements owing to complicated topographic condition, heterogeneity of surface reflection and difference in vegetation evapotranspiration. Compared to the observed 2011 summer CO2 drawdown (about 8 ppm) over mid-west, 2014 summer drawdown in the same region measured was much weak (approximately 3 ppm). The observed drawdown difference could be the results of the changes in both meteorological states and the phases of growing seasons. Individual lidar CO2 column measurements of 0.1-s integration were within 1-2 ppm of the CO2 estimates obtained from on-board in-situ sensors. For weak surface reflection conditions such as ocean surfaces, the 1- s integrated signal-to-noise ratio (SNR) of

  4. Techniques for estimating the percutaneous absorption of chemicals due to occupational and environmental exposure

    SciTech Connect

    Leung, Hon-Wing; Paustenbach, D.J.

    1994-03-01

    This article reviews the scientific principles involved in determining the percutaneous absorption of chemicals. To assist industrial hygienists in assessing the risks of dermal uptake of chemicals in workplaces, lists of absorption rates and example calculations including the use of wipe sampling to estimate skin exposure are presented. Recent advances in the use of mathematical models to examine the various factors influencing the percutaneous absorption of chemicals from matrices are discussed. Results from various models suggest that the skin uptake of nonvolatile, highly lipophilic chemicals in soil will range from about 30 percent to 50 percent, while the uptake of volatile chemicals will usually be less than 5 percent. The available published information suggests the following rules of thumb: (1) the bioavailability of chemicals in media vary widely; consequently, it is important to account for matrix effects; (2) proper wipe sampling should be conducted to estimate the degree of skin contact with contaminated surfaces; (3) the hazards posed by dermal contact with certain chemicals in the workplace, particularly those with a high n-octanol:water partition coefficient, can produce an appreciable degree of the daily absorbed dose, and the dose from percutaneous absorption can often be as much as one-half that due to inhalation; and (4) the contribution to overall uptake from percutaneous absorption of chemical vapors can be significant if the atmospheric concentration of the chemicals is tenfold to one thousandfold higher than the threshold limit value, even when the worker wears protective clothing and adequate respiratory protection. 92 refs., 5 tabs.

  5. High Spectral Resolution Lidar: System Calibration

    NASA Astrophysics Data System (ADS)

    Vivek Vivekanandan, J.; Morley, Bruce; Spuler, Scott; Eloranta, Edwin

    2015-04-01

    One of the unique features of the high spectral resolution lidar (HSRL) is simultaneous measurements of backscatter and extinction of atmosphere. It separates molecular scattering from aerosol and cloud particle backscatter based on their Doppler spectrum width. Scattering from aerosol and cloud particle are referred as Mie scattering. Molecular or Rayleigh scattering is used as a reference for estimating aerosol extinction and backscatter cross-section. Absolute accuracy of the backscattered signals and their separation into Rayleigh and Mie scattering depends on spectral purity of the transmitted signals, accurate measurement of transmit power, and precise performance of filters. Internal calibration is used to characterize optical subsystems Descriptions of high spectral resolution lidar system and its measurement technique can be found in Eloronta (2005) and Hair et al.(2001). Four photon counting detectors are used to measure the backscatter from the combined Rayleigh and molecular scattering (high and low gain), molecular scattering and cross-polarized signal. All of the detectors are sensitive to crosstalk or leakage through the optical filters used to separate the received signals and special data files are used to remove these effects as much as possible. Received signals are normalized with respect to the combined channel response to Mie and Rayleigh scattering. The laser transmit frequency is continually monitored and tuned to the 1109 Iodine absorption line. Aerosol backscatter cross-section is measured by referencing the aerosol return signal to the molecular return signal. Extinction measurements are calculated based on the differences between the expected (theoretical) and actual change in the molecular return. In this paper an overview of calibration of the HSRL is presented. References: Eloranta, E. W., High Spectral Resolution Lidar in Lidar: Range-Resolved Optical Remote Sensing of the Atmosphere, Klaus Weitkamp editor, Springer Series in Optical

  6. Boundary Layer CO2 mixing ratio measurements by an airborne pulsed IPDA lidar

    NASA Astrophysics Data System (ADS)

    Ramanathan, A. K.; Mao, J.; Abshire, J. B.; Allan, G. R.

    2014-12-01

    Since the primary signature of CO2 fluxes at the surface occurs in the planetary boundary layer (PBL), remote sensing measurements of CO2 that can resolve the CO2 absorption in the PBL separate from the total column are more sensitive to fluxes than those that can only measure a total column. The NASA Goddard CO2 sounder is a pulsed, range-resolved lidar that samples multiple (presently 30) wavelengths across the 1572.335 nm CO2 absorption line. The range resolution and line shape measurement enable CO2 mixing ratio measurements to be made in two or more altitude layers including the PBL via lidar cloud-slicing and multi-layer retrievals techniques. The pulsed lidar approach allows range-resolved backscatter of scattering from ground and cloud tops. Post flight data analysis can be used split the vertical CO2 column into layers (lidar cloud-slicing) and solve for the CO2 mixing ratio in each layer. We have demonstrated lidar cloud slicing with lidar measurements from a flight over Iowa, USA in August 2011 during the corn-growing season, remotely measuring a ≈15 ppm drawdown in the PBL CO2. We will present results using an improved lidar cloud slicing retrieval algorithm as well as preliminary measurements from the upcoming ASCENDS 2014 flight campaign. The CO2 absorption line is also more pressure broadened at lower altitudes. Analyzing the line shape also allows solving for some vertical resolution in the CO2 distribution. By allowing the retrieval process to independently vary the column concentrations in two or more altitude layers, one can perform a best-fit retrieval to obtain the CO2 mixing ratios in each of the layers. Analysis of airborne lidar measurements (in 2011) over Iowa, USA and Four Corners, New Mexico, USA show that for altitudes above 8 km, the CO2 sounder can detect and measure enhanced or diminished CO2 mixing ratios in the PBL even in the absence of clouds. We will present these results as well as preliminary measurements from the upcoming

  7. Atmospheric Pre-Corrected Differential Absorption Techniques to Retrieve Columnar Water Vapor: Application to AVIRIS 91/95 Data

    NASA Technical Reports Server (NTRS)

    Schlaepfer, Daniel; Borel, Christoph C.; Keller, Johannes; Itten, Klaus I.

    1996-01-01

    Water vapor is one of the main forces for weather development as well as for mesoscale air transport processes. The monitoring of water vapor is therefore an important aim in remote sensing of the atmosphere. Current operational systems for water vapor detection use primarily the emission in the thermal infrared (AVHRR, GOES, ATSR, Meteosat) or in the microwave radiation bands (DMSP). The disadvantage of current satellite systems is either a coarse spatial (horizontal) resolution ranging from one to tens of kilometers or a limited insight into the lower atmosphere. Imaging spectrometry on the other hand measures total column water vapor contents at a high spatial horizontal resolution and has therefore the potential of filling these gaps. The sensors of the AVIRIS instrument are capable of acquiring hyperspectral data in 224 bands located in the visible and near infrared at 10 nm resolution. This data includes the information on constituents of the earth's surface as well as of the atmosphere. The optical measurement of water vapor can be performed using sensor channels located in bands or lines of the absorption spectrum. The AVIRIS sensor has been used to retrieve water vapor and with less accuracy carbon dioxide, oxygen and ozone. To retrieve the water vapor amount, the so called differential absorption technique has been applied. The goal of this technique is to eliminate background factors by taking a ratio between channels within the absorption band and others besides the band. Various ratioing methods on the basis of different channels and calculation techniques were developed. The influence of a trace gas of interest on the radiance at the sensor level is usually simulated by using radiative transfer codes. In this study, the spectral transmittance and radiance are calculated by MODTRAN3 simulations with the new DISORT option. The objective of this work is to test the best performing differential absorption techniques for imaging spectrometry of

  8. Atmospheric pre-corrected differential absorption techniques to retrieve columnar water vapor: Application to AVIRIS 91/95 data

    SciTech Connect

    Schlaepfer, D.; Borel, C.C.; Keller, J.

    1996-03-01

    Water vapor is one of the main forces for weather development as well as for mesoscale air transport processes. The monitoring of water vapor is therefore an important aim in remote sensing of the atmosphere. Current operational systems for water vapor detection use primarily the emission in the thermal infrared (AVHRR, GOES, ATSR, Meteosat) or in the microwave radiation bands (DMSP). The disadvantage of current satellite systems is either a coarse spatial (horizontal) resolution ranging from one to tens of kilometers or a limited insight into the lower atmosphere. Imaging spectrometry on the other hand measures total column water vapor contents at a high spatial horizontal resolution and has therefore the potential of filling these gaps. The sensors of the AVIRIS instrument are capable of acquiring hyperspectral data in 224 bands located in the visible and near infrared at 10 run resolution. This data includes information on constituents of the earth`s surface as well as of the atmosphere. The optical measurement of water vapor can be performed using sensor channels located in bands or lines of the absorption spectrum. The AVIRIS sensor has been used to retrieve water vapor and with less accuracy carbon dioxide, oxygen and ozone. To retrieve the water vapor amount, the so called differential absorption technique has been applied. The goal of this technique is to eliminate background factors by taking a ratio between channels within the absorption band and others besides the band. Various rationing methods on the basis of different channels and calculation techniques were developed. The influence of a trace gas of interest on the radiance at the sensor level is usually simulated by using radiative transfer codes. In this study, spectral transmittance and radiance are calculated by MODTRAN3 simulations with the new DISORT option. This work testS the best performing differential absorption techniques for imaging spectrometry of tropospheric water vapor.

  9. Performance Simulations for a Spaceborne Methane Lidar Mission

    NASA Technical Reports Server (NTRS)

    Kiemle, C.; Kawa, Stephan Randolph; Quatrevalet, Mathieu; Browell, Edward V.

    2014-01-01

    Future spaceborne lidar measurements of key anthropogenic greenhouse gases are expected to close current observational gaps particularly over remote, polar, and aerosol-contaminated regions, where actual in situ and passive remote sensing observation techniques have difficulties. For methane, a "Methane Remote Lidar Mission" was proposed by Deutsches Zentrum fuer Luft- und Raumfahrt and Centre National d'Etudes Spatiales in the frame of a German-French climate monitoring initiative. Simulations assess the performance of this mission with the help of Moderate Resolution Imaging Spectroradiometer and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations of the earth's surface albedo and atmospheric optical depth. These are key environmental parameters for integrated path differential absorption lidar which uses the surface backscatter to measure the total atmospheric methane column. Results showthat a lidar with an average optical power of 0.45W at 1.6 µm wavelength and a telescope diameter of 0.55 m, installed on a low Earth orbit platform(506 km), will measure methane columns at precisions of 1.2%, 1.7%, and 2.1% over land, water, and snow or ice surfaces, respectively, for monthly aggregated measurement samples within areas of 50 × 50 km2. Globally, the mean precision for the simulated year 2007 is 1.6%, with a standard deviation of 0.7%. At high latitudes, a lower reflectance due to snow and ice is compensated by denser measurements, owing to the orbital pattern. Over key methane source regions such as densely populated areas, boreal and tropical wetlands, or permafrost, our simulations show that the measurement precision will be between 1 and 2%.

  10. Sensitive photothermal deflection technique for measuring absorption in optically thin media

    SciTech Connect

    Boccara, A. C.; Jackson, Warren; Amer, Nabil M.; Fournier, D.

    1980-01-01

    We present a highly sensitive and simple photothermal scheme for determining optical absorptions in condensed matter samples. {alpha}l values as low as 10{sup -7} and 10{sup -8} were measured for thin films and coatings and for liquids, respectively. A comparison with thermal lens effect is given, and the experimental factors limiting our sensitivity are discussed.

  11. Airborne IPDA Lidar Measurements of Atmospheric Methane in Support of MERLIN

    NASA Astrophysics Data System (ADS)

    Kiemle, C.; Amediek, A.; Wirth, M.; Ehret, G.

    2015-12-01

    Space-based lidar missions targeting greenhouse gases are expected to close observational gaps, e.g., over subarctic permafrost and tropical wetlands, where in-situ and passive remote sensing techniques have difficulties. Consequently, a "Methane Remote Lidar Mission" (MERLIN) was proposed by the German and French space agencies DLR and CNES. MERLIN is now in Phase B, in which all mission components are planned in detail; launch is foreseen in 2020. An integrated path differential absorption (IPDA) lidar will measure weighted columns of atmospheric methane (XCH4) along the satellite track. Primary objective is to provide accurate global observations of methane concentration gradients for inverse numerical models in order to better quantify regional fluxes. DLR has developed an airborne demonstrator, CHARM-F, for technology demonstration and validation purposes. First successful flights on-board the German HALO research aircraft have been performed in May 2015 over Central Europe. The measurements are expected to help solve general retrieval issues for future space-borne IPDA lidars. For example, the CHARM-F flights over ocean and lakes help assess the strength and variability of backscatter from water surfaces. The IPDA weighting function, or measurement sensitivity, is dependent on atmospheric pressure and temperature, in particular close to the surface. We use ECMWF analyses interpolated in space and time to the aircraft track that provide these auxiliary data at 14 km horizontal resolution. Due to the coarse representation of orography the model's pressure and temperature profiles have to be extrapolated down to the true lidar's scattering surface elevation, which generates uncertainties that we assess. We also assess biases by spectroscopic uncertainties in the methane absorption lines' parameters. Overall, the airborne results will support the development of advanced processing algorithms for future space lidar missions such as MERLIN.

  12. Alexandrite lidar for the atmospheric water vapor detection and development of powerful tunable sources in IR

    NASA Technical Reports Server (NTRS)

    Uchiumi, M.; Maeda, M.; Muraoka, K.; Uchino, O.

    1992-01-01

    New tunable solid-state lasers, such as alexandrite and Ti-sapphire lasers, provide a powerful technique to detect various molecules in the atmosphere whose absorption bands are in the infrared region. The differential absorption lidar (DIAL) system to measure the tropospheric water vapor has been investigated by many authors, in an early stage, by dye and ruby lasers. Using the alpha band of water vapor, the longest detection range can be obtained with high accuracy, and the alexandrite laser is the most suitable laser for this purpose. In this paper, we describe the detection of water vapor in the atmosphere by an alexandrite lidar, and the development of powerful tunable sources based on Raman lasers in the infrared region.

  13. Development of a Coherent Lidar for Aiding Precision Soft Landing on Planetary Bodies

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Pierrottet, Diego; Tolson, Robert H.; Powell, Richard W.; Davidson, John B.; Peri, Frank

    2005-01-01

    Coherent lidar can play a critical role in future planetary exploration missions by providing key guidance, navigation, and control (GNC) data necessary for navigating planetary landers to the pre-selected site and achieving autonomous safe soft-landing. Although the landing accuracy has steadily improved over time to approximately 35 km for the recent Mars Exploration Rovers due to better approach navigation, a drastically different guidance, navigation and control concept is required to meet future mission requirements. For example, future rovers will require better than 6 km landing accuracy for Mars and better than 1 km for the Moon plus maneuvering capability to avoid hazardous terrain features. For this purpose, an all-fiber coherent lidar is being developed to address the call for advancement of entry, descent, and landing technologies. This lidar will be capable of providing precision range to the ground and approach velocity data, and in the case of landing on Mars, it will also measure the atmospheric wind and density. The lidar obtains high resolution range information from a frequency modulated-continuous wave (FM-CW) laser beam whose instantaneous frequency varies linearly with time, and the ground vector velocity is directly extracted from the Doppler frequency shift. Utilizing the high concentration of aerosols in the Mars atmosphere (approx. two order of magnitude higher than the Earth), the lidar can measure wind velocity with a few watts of optical power. Operating in 1.57 micron wavelength regime, the lidar can use the differential absorption (DIAL) technique to measure the average CO2 concentration along the laser beam using, that is directly proportional to the Martian atmospheric density. Employing fiber optics components allows for the lidar multi-functional operation while facilitating a highly efficient, compact and reliable design suitable for integration into a spacecraft with limited mass, size, and power resources.

  14. Lidar Measurements of Methane and Applications for Aircraft and Spacecraft

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Numata, Kenji; Abshire, James; Li, Steve; Wu, Stewart; Krainak, Michael; Sun, Xiaoli

    2010-01-01

    Atmospheric methane levels have remained relatively constant over the last decade around 1.78 parts per million (ppm) but observations since 2007 show that levels may be increasing. This trend may be caused by increased fossil fuel production, rice farming, livestock and landfills, but the underlying causes are quite uncertain. One hypothesis is that reservoirs of carbon trapped in the permafrost regions of northern Canada, Europe, and Siberia thaw as global temperatures rise and are releasing increasing amounts of methane. Another hypothesis points to increased production of methane by microbes as the permafrost warms. Currently most observations of greenhouse gases are limited to in-situ (surface and tower sites) and limited airborne in-situ measurements. Space column density measurements are starting to become available from the GOSAT mission. Although methane survives for a shorter time in the atmosphere than CO2, its impact on climate change per molecule is about 23 times than that of CO2. Accurate global observations of several greenhouse gases, including methane, are urgently needed in order to better understand climate change processes and to reduce the uncertainty in the carbon budget. Differential absorption lidar is a well-established technique to measure atmospheric gases, and methane has optical absorption bands near 1.65,2.2,3.4 and 7.8 micron. The near infrared overtones lines of CH4 near 1650 nm are relatively free of interference from other species. There are absorption lines near 1651 nm which are both temperature insensitive and have line strengths well suited for lidar measurements. We have developed a laser and demonstrated lidar measurements of CH4 using lines in this band. Our laser uses a narrow linewidth 1064 nm laser pulse passing through a nonlinear crystal. We generate the tunable laser signals near 1651 nm by using the optical parametric amplification (OPA) process. Inside the crystal the 1064 nm beam overlaps with an injection seed

  15. Determination of third-order optical absorptive nonlinearity of ZnO nanoparticles by Z-scan technique

    NASA Astrophysics Data System (ADS)

    Sreeja, R.; Reshmi, R.; Manu, George; Jayaraj, M. K.

    2008-09-01

    A sensitive single-beam technique for measuring the nonlinear absorption coefficient of ZnO nanoparticles is reported here. The transmittance T(z) of the sample is measured by open aperture Z-scan technique as the sample is moved along the propagation path(z) of a focused Gaussian laser beam. The ZnO nanoparticles synthesized by wet chemical method, by mixing zinc acetate dehydrate and NaOH in ethanol is a clear transparent colloidal solution. The average size of ZnO nanoparticles is 6nm as confirmed by TEM analysis. Two-photon absorption of colloidal solutions of ZnO nanoparticles in ethanol is investigated by the Z-scan method using the nanosecond pulses from the second harmonics of Nd:YAG laser (532nm). The value of β for ZnO dispersed in ethanol extracted from the Z-scan data are 2.1cm/GW. ZnO nanoparticles of various sizes were embedded in PVA matrix on glass substrate and size dependence on β value was analyzed. The high value of two photon absorption coefficient (β) demonstrate that ZnO nanoparticle is a potential material for optical limiting applications.

  16. Evaluation of laser absorption spectroscopic techniques for eddy covariance flux measurements of ammonia.

    PubMed

    Whitehead, James D; Twigg, Marsailidh; Famulari, Daniela; Nemitz, Eiko; Sutton, Mark A; Gallagher, Martin W; Fowler, David

    2008-03-15

    An intercomparison was made between eddy covariance flux measurements of ammonia by a quantum cascade laser absorption spectrometer (QCLAS) and a lead-salt tunable diode laser absorption spectrometer (TDLAS). The measurements took place in September 2004 and again in April 2005 over a managed grassland site in Southern Scotland, U.K. These were also compared with a flux estimate derived from an "Ammonia Measurement by ANnular Denuder with online Analysis" (AMANDA), using the aerodynamic gradient method (AGM). The concentration and flux measurements from the QCLAS correlated well with those of the TDLAS and the AGM systems when emissions were high, following slurry application to the field. Both the QCLAS and TDLAS, however, underestimated the flux when compared with the AMANDA system, by 64%. A flux loss of 41% due to chemical reaction of ammonia in the QCLAS (and 37% in the TDLAS) sample tube walls was identified and characterized using laboratory tests but did not fully accountforthis difference. Recognizing these uncertainties, the agreement between the systems was nevertheless very close (R2 = 0.95 between the QCLAS and the TDLAS; R2 = 0.84 between the QCLAS and the AMANDA) demonstrating the suitability of the laser absorption methods for quantifying the temporal dynamics of ammonia fluxes.

  17. Improvement of differential optical absorption spectroscopy with a multichannel scanning technique.

    PubMed

    Brauers, T; Hausmann, M; Brandenburger, U; Dorn, H P

    1995-07-20

    Differential optical absorption spectroscopy (DOAS) of atmospheric trace gases requires the detection of optical densities below 0.1%. Photodiode arrays are used more and more as detectors for DOAS because they allow one to record larger spectral intervals simultaneously. This type of optical multichannel analyzer (OMA), however, shows sensitivity differences among the individual photodiodes (pixels), which are of the order of 1%. To correct for this a sensitivity reference spectrum is usually recorded separately from the trace-gas measurements. Because of atmospheric turbulence the illumination of the detector while an atmospheric absorption spectrum is being recorded is different from the conditions during the reference measurement. As a result the sensitivity patterns do not exactly match, and the corrected spectra still show a residual structure that is due to the sensitivity difference. This effect usually limits the detection of optical densities to approximately 3 × 10(-4). A new method for the removal of the sensitivity pattern is presented in this paper: Scanning the spectrometer by small wavelength increments after each readout of the OMA allows one to separate the OMA-fixed pattern and the wavelength-fixed structures (absorption lines). The properties of the new method and its applicability are demonstrated with simulated spectra. Finally, first atmospheric measurements with a laser long-path instrument demonstrate a detection limit of 3 × 10(-5) of a DOAS experiment. PMID:21052280

  18. Pulsed Lidar Measurements of Atmospheric CO2 Column Concentration in the ASCENDS 2014 Airborne Campaign

    NASA Astrophysics Data System (ADS)

    Abshire, J. B.; Ramanathan, A. K.; Mao, J.; Riris, H.; Allan, G. R.; Hasselbrack, W. E.; Chen, J. R.

    2015-12-01

    We report progress in demonstrating a pulsed, wavelength-resolved IPDA lidar technique for measuring the tropospheric CO2 concentrations as a candidate for NASA's ASCENDS mission. The CO2 lidar flies on NASA's DC-8 aircraft and measures the atmospheric backscatter profiles and shape of the 1572.33 nm absorption line by using 30 wavelength samples distributed across the lube. Our post-flight analysis estimates the lidar range and pulse energies at each wavelength 10 times per second. The retrievals solve for the optimum CO2 absorption line shape and the column average CO2 concentrations using radiative transfer calculations based on HITRAN, the aircraft altitude, range to the scattering surface, and the atmospheric conditions. We compare these to CO2 concentrations sampled by in-situ sensors on the aircraft. The number of wavelength samples can be reduced in the retrievals. During the ASCENDS airborne campaign in 2013 two flights were made in February over snow in the Rocky Mountains and the Central Plains allowing measurement of snow-covered surface reflectivity. Several improvements were made to the lidar for the 2014 campaign. These included using a new step-locked laser diode source, and incorporating a new HgCdTe APD detector and analog digitizer into the lidar receiver. Testing showed this detector had higher sensitivity, analog response, and a more linear dynamic range than the PMT detector used previously. In 2014 flights were made in late August and early September over the California Central Valley, the redwood forests along the California coast, two desert areas in Nevada and California, and two flights above growing agriculture in Iowa. Two flights were also made under OCO-2 satellite ground tracks. Analyses show the retrievals of lidar range and CO2 column absorption, and mixing ratio worked well when measuring over topography with rapidly changing height and reflectivity, and through thin clouds and aerosol scattering. The lidar measurements clearly

  19. X-ray absorption spectroscopy of Mn doped ZnO thin films prepared by rf sputtering technique

    SciTech Connect

    Yadav, Ashok Kumar; Jha, S. N.; Bhattacharyya, D.; Haque, Sk Maidul; Shukla, Dinesh; Choudhary, Ram Janay

    2015-11-15

    A set of r.f. sputter deposited ZnO thin films prepared with different Mn doping concentrations have been characterised by Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Spectroscopy (XANES) measurements at Zn, Mn and O K edges and at Mn L{sub 2,3} edges apart from long range structural characterisation by Grazing Incident X-ray Diffraction (GIXRD) technique. Magnetic measurements show room temperature ferromagnetism in samples with lower Mn doping which is however, gets destroyed at higher Mn doping concentration. The results of the magnetic measurements have been explained using the local structure information obtained from EXAFS and XANES measurements.

  20. Differential Absorption Lidar (DIAL) in Alberta: A New Remote Sensing Tool for Wide Area Measurement of Particulates, CO2, and CH4 Emissions from Energy Extraction and Production Sites

    NASA Astrophysics Data System (ADS)

    Wojcik, M.; Lemon, R.; Crowther, B. G.; Valupadas, P.; Fu, L.; Yang, Z.; Huda, Q.; Leung, B.; Chambers, A.

    2014-12-01

    Alberta Environmental Monitoring, Evaluation and Reporting Agency (AEMERA) in cooperation with the Space Dynamics Laboratory (SDL) of Utah State University, have developed a mobile DIAL sensor designed specifically for particle, CO2 and CH4 emissions measurement. Rapid expansion of the oil and gas industry in Alberta, including the oil sands, has challenged the Alberta Government to keep pace in its efforts to monitor and mitigate the environmental impacts of development. The limitations of current monitoring systems has pushed the provincial government to seek out advanced sensing technologies such as differential absorption lidar (DIAL) to help assess the impact of energy development and industrial operations. This instrument is housed inside a 36' trailer and can be quickly staged and used to characterize source emissions and to locate fugitive leaks. DIAL is capable of measuring concentrations for carbon dioxide (CO2) and methane (CH4) at ranges of up to 3 km with a spatial resolution of 1.5 m. DIAL can map both CO2 and CH4, as well as particulate matter (PM) in a linear fashion; by scanning the laser beam in both azimuth and elevation, DIAL can create images of emissions concentrations and ultimately can be used to determine emission factors, locate fugitive leaks, assess plume dispersion and confirm air dispersion modeling. The DIAL system has been deployed at a landfill, a coal-fired power plant, and an oil sands production area. A system overview of the DIAL instrument and recent results will be discussed.

  1. Analytical estimation of the parameters of autodyne lidar.

    PubMed

    Koganov, Gennady A; Shuker, Reuben; Gordov, Evgueni P

    2002-11-20

    An analytical approach for a calculation of the parameters of autodyne lidar is presented. Approximate expressions connecting the absorption coefficient and the distance to the remote target with both the lidar parameters and the measured quantities are obtained. These expressions allow one to retrieve easily the information about the atmosphere from the experimental data. PMID:12463256

  2. Analysis for nonlinear inversion technique developed to estimate depth-distribution of absorption by spatially resolved backscattering measurement

    NASA Astrophysics Data System (ADS)

    Nishida, Kazuhiro; Namita, Takeshi; Kato, Yuji; Shimizu, Koichi

    2015-03-01

    We have proposed a new nonlinear inversion technique to estimate the spatial distribution of the absorption coefficient (μa) in the depth direction of a turbid medium by spatially resolved backscattering measurement. With this technique, we can obtain cross-sectional image of μa as deep as the backscattered light traveled even when the transmitted light through the medium cannot be detected. In this technique, the depth distribution of absorption coefficient is determined by iterative calculation using the spatial path-length distribution (SPD) of traveled photons as a function of source-detector distance. In this calculation, the variance of path-length of many photons in each layer is also required. The SPD and the variance of path-length are obtained by Monte Carlo simulation using a known reduced scattering coefficient (μs'). Therefore, we need to know the μs' of the turbid medium beforehand. We have shown in computer simulation that this technique works well when the μs' is the typical values of mammalian body tissue, or 1.0 /mm. In this study, the accuracy of the μa estimation was analyzed and its dependence on the μs' was clarified quantitatively in various situations expected in practice. 10% deviations in μs' resulted in about 30% error in μa estimation, in average. This suggested that the measurement or the appropriate estimation of μs' is required to utilize the proposed technique effectively. Through this analysis, the effectiveness and the limitation of the newly proposed technique were clarified, and the problems to be solved were identified.

  3. Stratospheric temperature measurement with scanning Fabry-Perot interferometer for wind retrieval from mobile Rayleigh Doppler lidar.

    PubMed

    Xia, Haiyun; Dou, Xiankang; Shangguan, Mingjia; Zhao, Ruocan; Sun, Dongsong; Wang, Chong; Qiu, Jiawei; Shu, Zhifeng; Xue, Xianghui; Han, Yuli; Han, Yan

    2014-09-01

    Temperature detection remains challenging in the low stratosphere, where the Rayleigh integration lidar is perturbed by aerosol contamination and ozone absorption while the rotational Raman lidar is suffered from its low scattering cross section. To correct the impacts of temperature on the Rayleigh Doppler lidar, a high spectral resolution lidar (HSRL) based on cavity scanning Fabry-Perot Interferometer (FPI) is developed. By considering the effect of the laser spectral width, Doppler broadening of the molecular backscatter, divergence of the light beam and mirror defects of the FPI, a well-behaved transmission function is proved to show the principle of HSRL in detail. Analysis of the statistical error of the HSRL is carried out in the data processing. A temperature lidar using both HSRL and Rayleigh integration techniques is incorporated into the Rayleigh Doppler wind lidar. Simultaneous wind and temperature detection is carried out based on the combined system at Delhi (37.371°N, 97.374°E; 2850 m above the sea level) in Qinghai province, China. Lower Stratosphere temperature has been measured using HSRL between 18 and 50 km with temporal resolution of 2000 seconds. The statistical error of the derived temperatures is between 0.2 and 9.2 K. The temperature profile retrieved from the HSRL and wind profile from the Rayleigh Doppler lidar show good agreement with the radiosonde data. Specifically, the max temperature deviation between the HSRL and radiosonde is 4.7 K from 18 km to 36 km, and it is 2.7 K between the HSRL and Rayleigh integration lidar from 27 km to 34 km. PMID:25321553

  4. Stratospheric temperature measurement with scanning Fabry-Perot interferometer for wind retrieval from mobile Rayleigh Doppler lidar.

    PubMed

    Xia, Haiyun; Dou, Xiankang; Shangguan, Mingjia; Zhao, Ruocan; Sun, Dongsong; Wang, Chong; Qiu, Jiawei; Shu, Zhifeng; Xue, Xianghui; Han, Yuli; Han, Yan

    2014-09-01

    Temperature detection remains challenging in the low stratosphere, where the Rayleigh integration lidar is perturbed by aerosol contamination and ozone absorption while the rotational Raman lidar is suffered from its low scattering cross section. To correct the impacts of temperature on the Rayleigh Doppler lidar, a high spectral resolution lidar (HSRL) based on cavity scanning Fabry-Perot Interferometer (FPI) is developed. By considering the effect of the laser spectral width, Doppler broadening of the molecular backscatter, divergence of the light beam and mirror defects of the FPI, a well-behaved transmission function is proved to show the principle of HSRL in detail. Analysis of the statistical error of the HSRL is carried out in the data processing. A temperature lidar using both HSRL and Rayleigh integration techniques is incorporated into the Rayleigh Doppler wind lidar. Simultaneous wind and temperature detection is carried out based on the combined system at Delhi (37.371°N, 97.374°E; 2850 m above the sea level) in Qinghai province, China. Lower Stratosphere temperature has been measured using HSRL between 18 and 50 km with temporal resolution of 2000 seconds. The statistical error of the derived temperatures is between 0.2 and 9.2 K. The temperature profile retrieved from the HSRL and wind profile from the Rayleigh Doppler lidar show good agreement with the radiosonde data. Specifically, the max temperature deviation between the HSRL and radiosonde is 4.7 K from 18 km to 36 km, and it is 2.7 K between the HSRL and Rayleigh integration lidar from 27 km to 34 km.

  5. Light absorption by airborne aerosols: comparison of integrating plate and spectrophone techniques.

    PubMed

    Szkarlat, A C; Japar, S M

    1981-04-01

    An excellent correlation between the integrating plate (IP) and the photoacoustic methods for measuring aerosol light absorption has been found for airborne graphitic carbon in diesel vehicle exhaust. However, the regression coefficient depends on the orientation of the Teflon membrane filter during the IP analysis. With the collected particulates between the filter and the integrating plate, the IP response is 1.85 times that for the filter reversed. In either case the response ratio of the IP method to the photoacoustic method is >1.0, i.e., 2.43 vs 1.30. The IP calibration is also probably dependent on the nature of the filter medium. PMID:20309278

  6. Measurement of Hydrogen Absorption in Ternary Alloys with Volumetric (Sieverts Loop) Techniques

    SciTech Connect

    Aceves, S.

    2015-10-26

    The Sieverts loop is an inexpensive, robust and reliable methodology for calculating hydrogen absorption in materials [1]. In this approach, we start by storing a sample of the material being tested in the volume Vcell (Figure 1) and initiate the process by producing a high vacuum in the system while the material sample is heated to eliminate (most of) the hydrogen and other impurities previously absorbed. The system typically operates isothermally, with the volume Vref at ambient temperature and the sample at a temperature of interest – high enough to liquefy the alloy for the current application to nuclear fusion.

  7. Demonstration of differential backscatter absorption gas imaging.

    PubMed

    Powers, P E; Kulp, T J; Kennedy, R

    2000-03-20

    Backscatter absorption gas imaging (BAGI) is a technique that uses infrared active imaging to generate real-time video imagery of gas plumes. We describe a method that employs imaging at two wavelengths (absorbed and not absorbed by the gas to be detected) to allow wavelength-differential BAGI. From the frames collected at each wavelength, an absorbance image is created that displays the differential absorbance of the atmosphere between the imager and the backscatter surface. This is analogous to a two-dimensional topographic differential absorption lidar or differential optical absorption spectroscopy measurement. Gas plumes are displayed, but the topographic scene image is removed. This allows a more effective display of the plume image, thus ensuring detection under a wide variety of conditions. The instrument used to generate differential BAGI is described. Data generated by the instrument are presented and analyzed to estimate sensitivity. PMID:18338030

  8. Advances in High Energy Solid-State Pulsed 2-Micron Lidar Development for Ground and Airborne Wind, Water Vapor and CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Kavaya, Michael J.; Remus, Ruben

    2015-01-01

    NASA Langley Research Center has a long history of developing 2-micron lasers. From fundamental spectroscopy research, theoretical prediction of new materials, laser demonstration and engineering of lidar systems, it has been a very successful program spanning around two decades. Successful development of 2-micron lasers has led to development of a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement with an unprecedented laser pulse energy of 250 millijoules in a rugged package. This high pulse energy is produced by a Ho:Tm:LuLiF laser with an optical amplifier. While the lidar is meant for use as an airborne instrument, ground-based tests were carried out to characterize performance of the lidar. Atmospheric measurements will be presented, showing the lidar's capability for wind measurement in the atmospheric boundary layer and free troposphere. Lidar wind measurements are compared to a balloon sonde, showing good agreement between the two sensors. Similar architecture has been used to develop a high energy, Ho:Tm:YLF double-pulsed 2-micron Integrated Differential Absorption Lidar (IPDA) instrument based on direct detection technique that provides atmospheric column CO2 measurements. This instrument has been successfully used to measure atmospheric CO2 column density initially from a ground mobile lidar trailer, and then it was integrated on B-200 plane and 20 hours of flight measurement were made from an altitude ranging 1500 meters to 8000 meters. These measurements were compared to in-situ measurements and National Oceanic and Atmospheric Administration (NOAA) airborne flask measurement to derive the dry mixing ratio of the column CO2 by reflecting the signal by various reflecting surfaces such as land, vegetation, ocean surface, snow and sand. The lidar measurements when compared showed a very agreement with in-situ and airborne flask measurement. NASA Langley Research Center is currently developing a

  9. Advances in High Energy Solid-State Pulsed 2-micron Lidar Development for Ground and Airborne Wind, Water Vapor and CO2 Measurements

    NASA Astrophysics Data System (ADS)

    Singh, Upendra; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Kavaya, Michael; Remus, Ruben

    2015-04-01

    NASA Langley Research Center has a long history of developing 2 µm lasers. From fundamental spectroscopy research, theoretical prediction of new materials, laser demonstration and engineering of lidar systems, it has been a very successful program spanning around two decades. Successful development of 2 µm lasers has led to development of a state-of-the-art compact lidar transceiver for a pulsed coherent Doppler lidar system for wind measurement with an unprecedented laser pulse energy of 250-mJ in a rugged package. This high pulse energy is produced by a Ho:Tm:LuLiF laser with an optical amplifier. While the lidar is meant for use as an airborne instrument, ground-based tests were carried out to characterize performance of the lidar. Atmospheric measurements will be presented, showing the lidar's capability for wind measurement in the atmospheric boundary layer and free troposphere. Lidar wind measurements are compared to a balloon sonde, showing good agreement between the two sensors. Similar architecture has been used to develop a high energy, Ho:Tm:YLF double-pulsed 2 μm Integrated Differential Absorption Lidar (IPDA) instrument based on direct detection technique that provides atmospheric column CO2 measurements. This instrument has been successfully used to measure atmospheric CO2 column density initially from a ground mobile lidar trailer, and then it was integrated on B-200 plane and 20 hrs of flight measurement were made from an altitude ranging 1500 meter to 8000 meter. These measurements were compared to in-situ measurements and NOAA airborne flask measurement to derive the dry mixing ratio of the column CO2 by reflecting the signal by various reflecting surfaces such as land, vegetation, ocean surface, snow and sand. The lidar measurements when compared showed a very agreement with in-situ and airborne flask measurement. NASA Langley Research Center is currently developing a triple-pulsed 2 μm Integrated Differential Absorption Lidar (IPDA

  10. Lidar postcards

    USGS Publications Warehouse

    Schreppel, Heather A.; Cimitile, Matthew J.

    2011-01-01

    The U.S. Geological Survey (USGS) Coastal and Marine Geology Program develops and uses specialized technology to build high-resolution topographic and habitat maps. High-resolution maps of topography, bathymetry, and habitat describe important features affected by coastal-management decisions. The mapped information serves as a baseline for evaluating resources and tracking the effectiveness of resource- and conservation-management decisions. These data products are critical to researchers, decision makers, resource managers, planners, and the public. To learn more about Lidar (light detection and ranging) technology visit: http://ngom.usgs.gov/dsp/.

  11. Quantum cascade laser absorption spectroscopy with the amplitude-to-time conversion technique for atmospheric-pressure plasmas

    SciTech Connect

    Yumii, Takayoshi; Kimura, Noriaki; Hamaguchi, Satoshi

    2013-06-07

    The NO{sub 2} concentration, i.e., density, in a small plasma of a nitrogen oxide (NOx) treatment reactor has been measured by highly sensitive laser absorption spectroscopy. The absorption spectroscopy uses a single path of a quantum cascade laser beam passing through a plasma whose dimension is about 1 cm. The high sensitivity of spectroscopy is achieved by the amplitude-to-time conversion technique. Although the plasma reactor is designed to convert NO in the input gas to NO{sub 2}, it has been demonstrated by this highly sensitive absorption spectroscopy that NO{sub 2} in a simulated exhaust gas that enters the reactor is decomposed by the plasma first and then NO{sub 2} is formed again, possibly more than it was decomposed, through a series of gas-phase reactions by the time the gas exits the reactor. The observation is consistent with that of an earlier study on NO decomposition by the same type of a plasma reactor [T. Yumii et al., J. Phys. D 46, 135202 (2013)], in which a high concentration of NO{sub 2} was observed at the exit of the reactor.

  12. A portable lidar using a diode-pumped YAG laser

    NASA Technical Reports Server (NTRS)

    Takeuchi, N.; Okumura, H.; Sugita, T.; Matsumoto, H.; Yamaguchi, S.

    1992-01-01

    A Mie lidar system is technically established and is used for monitoring air pollution, stratospheric and boundary layer aerosol distribution, plume dispersion, visibility, and the study of atmospheric structure and cloud physics. However, a lidar system is not widely used because of its cumbersome handling and unwieldy portability. Although the author developed a laser diode lidar system based on RM-CW technique, it has a limit of measurement distance. Here we report the development of an all solid Mie lidar system using a diode-pumped Nd:YAG laser and a Si-APD detector. This was constructed as a prototype of a handy lidar system.

  13. Finnish Meteorological Institute Doppler Lidar

    SciTech Connect

    Ewan OConnor

    2015-03-27

    This doppler lidar system provides co-polar and cross polar attenuated backscatter coefficients,signal strength, and doppler velocities in the cloud and in the boundary level, including uncertainties for all parameters. Using the doppler beam swinging DBS technique, and Vertical Azimuthal Display (VAD) this system also provides vertical profiles of horizontal winds.

  14. Analysis of zinc in biological samples by flame atomic absorption spectrometry: use of addition calibration technique.

    PubMed

    Dutra, Rosilene L; Cantos, Geny A; Carasek, Eduardo

    2006-01-01

    The quantification of target analytes in complex matrices requires special calibration approaches to compensate for additional capacity or activity in the matrix samples. The standard addition is one of the most important calibration procedures for quantification of analytes in such matrices. However, this technique requires a great number of reagents and material, and it consumes a considerable amount of time throughout the analysis. In this work, a new calibration procedure to analyze biological samples is proposed. The proposed calibration, called the addition calibration technique, was used for the determination of zinc (Zn) in blood serum and erythrocyte samples. The results obtained were compared with those obtained using conventional calibration techniques (standard addition and standard calibration). The proposed addition calibration was validated by recovery tests using blood samples spiked with Zn. The range of recovery for blood serum and erythrocyte samples were 90-132% and 76-112%, respectively. Statistical studies among results obtained by the addition technique and conventional techniques, using a paired two-tailed Student's t-test and linear regression, demonstrated good agreement among them. PMID:16943611

  15. Lidar Analyses

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.

    1995-01-01

    A brief description of enhancements made to the NASA MSFC coherent lidar model is provided. Notable improvements are the addition of routines to automatically determine the 3 dB misalignment loss angle and the backscatter value at which the probability of a good estimate (for a maximum likelihood estimator) falls to 50%. The ability to automatically generate energy/aperture parametrization (EAP) plots which include the effects of angular misalignment has been added. These EAP plots make it very easy to see that for any practical system where there is some degree of misalignment then there is an optimum telescope diameter for which the laser pulse energy required to achieve a particular sensitivity is minimized. Increasing the telescope diameter above this will result in a reduction of sensitivity. These parameterizations also clearly show that the alignment tolerances at shorter wavelengths are much stricter than those at longer wavelengths. A brief outline of the NASA MSFC AEOLUS program is given and a summary of the lidar designs considered during the program is presented. A discussion of some of the design trades is performed both in the text and in a conference publication attached as an appendix.

  16. Fabrication of controllable form submicrometer structures on positive photoresist by one-photon absorption direct laser writing technique

    NASA Astrophysics Data System (ADS)

    Tong, Quang Cong; Do, Minh Thanh; Journet, Bernard; Ledoux-Rak, Isabelle; Lai, Ngoc Diep

    2016-04-01

    We demonstrate a very simple and low-cost method based on one-photon absorption direct laser writing technique to fabricate arbitrary two-dimensional (2D) polymeric submicrometer structures with controllable form. In this technique, a continuous-wave green laser beam (532 nm) with very weak power is tightly focused into a positive photoresist (S1805) by a high numerical aperture (NA) objective lens (OL), depolymerizing the polymer in a local submicrometer region. The focusing spot is then moved in a controllable trajectory by a 3D piezo translation stage, resulting in desired structures. The low absorption effect of the photoresist at the excitation wavelength allows obtaining structures with submicrometer size and great depth. In particular, by controlling the exposure dose, e.g. the scanning speed, and the scanning configuration, the structures have been created in positive (cylindrical material in air) or negative (air holes) form. The 2D square structures with periods in between 0.6 μm and 1 μm and with a feature size of about 150 nm have been demonstrated with an OL of NA = 0.9 (air-immersion). The fabricated results are well consistent with those obtained numerically by using a vectorial diffraction theory for high NA OLs. This investigation should be very useful for fabrication of photonic and plasmonic templates.

  17. One-step fabrication of submicrostructures by low one-photon absorption direct laser writing technique with local thermal effect

    NASA Astrophysics Data System (ADS)

    Nguyen, Dam Thuy Trang; Tong, Quang Cong; Ledoux-Rak, Isabelle; Lai, Ngoc Diep

    2016-01-01

    In this work, local thermal effect induced by a continuous-wave laser has been investigated and exploited to optimize the low one-photon absorption (LOPA) direct laser writing (DLW) technique for fabrication of polymer-based microstructures. It was demonstrated that the temperature of excited SU8 photoresist at the focusing area increases to above 100 °C due to high excitation intensity and becomes stable at that temperature thanks to the use of a continuous-wave laser at 532 nm-wavelength. This optically induced thermal effect immediately completes the crosslinking process at the photopolymerized region, allowing obtain desired structures without using the conventional post-exposure bake (PEB) step, which is usually realized after the exposure. Theoretical calculation of the temperature distribution induced by local optical excitation using finite element method confirmed the experimental results. LOPA-based DLW technique combined with optically induced thermal effect (local PEB) shows great advantages over the traditional PEB, such as simple, short fabrication time, high resolution. In particular, it allowed the overcoming of the accumulation effect inherently existed in optical lithography by one-photon absorption process, resulting in small and uniform structures with very short lattice constant.

  18. Scanning tropospheric ozone and aerosol lidar with double-gated photomultipliers.

    PubMed

    Machol, Janet L; Marchbanks, Richard D; Senff, Christoph J; McCarty, Brandi J; Eberhard, Wynn L; Brewer, William A; Richter, Ronald A; Alvarez, Raul J; Law, Daniel C; Weickmann, Ann M; Sandberg, Scott P

    2009-01-20

    The Ozone Profiling Atmospheric Lidar is a scanning four-wavelength ultraviolet differential absorption lidar that measures tropospheric ozone and aerosols. Derived profiles from the lidar data include ozone concentration, aerosol extinction, and calibrated aerosol backscatter. Aerosol calibrations assume a clear air region aloft. Other products include cloud base heights, aerosol layer heights, and scans of particulate plumes from aircraft. The aerosol data range from 280 m to 12 km with 5 m range resolution, while the ozone data ranges from 280 m to about 1.2 km with 100 m resolution. In horizontally homogeneous atmospheres, data from multiple-elevation angles is combined to reduce the minimum altitude of the aerosol and ozone profiles to about 20 m. The lidar design, the characterization of the photomultiplier tubes, ozone and aerosol analysis techniques, and sample data are described. Also discussed is a double-gating technique to shorten the gated turn-on time of the photomultiplier tubes, and thereby reduce the detection of background light and the outgoing laser pulse.

  19. Scanning tropospheric ozone and aerosol lidar with double-gated photomultipliers.

    PubMed

    Machol, Janet L; Marchbanks, Richard D; Senff, Christoph J; McCarty, Brandi J; Eberhard, Wynn L; Brewer, William A; Richter, Ronald A; Alvarez, Raul J; Law, Daniel C; Weickmann, Ann M; Sandberg, Scott P

    2009-01-20

    The Ozone Profiling Atmospheric Lidar is a scanning four-wavelength ultraviolet differential absorption lidar that measures tropospheric ozone and aerosols. Derived profiles from the lidar data include ozone concentration, aerosol extinction, and calibrated aerosol backscatter. Aerosol calibrations assume a clear air region aloft. Other products include cloud base heights, aerosol layer heights, and scans of particulate plumes from aircraft. The aerosol data range from 280 m to 12 km with 5 m range resolution, while the ozone data ranges from 280 m to about 1.2 km with 100 m resolution. In horizontally homogeneous atmospheres, data from multiple-elevation angles is combined to reduce the minimum altitude of the aerosol and ozone profiles to about 20 m. The lidar design, the characterization of the photomultiplier tubes, ozone and aerosol analysis techniques, and sample data are described. Also discussed is a double-gating technique to shorten the gated turn-on time of the photomultiplier tubes, and thereby reduce the detection of background light and the outgoing laser pulse. PMID:19151820

  20. A Geosynchronous Lidar System for Atmospheric Winds, Temperature, and Moisture Measurements

    NASA Technical Reports Server (NTRS)

    Emmitt, Dave; Komar, George (Technical Monitor)

    2001-01-01

    A geosynchronous Lidar would enable synoptic measurement of atmospheric winds; temperature; and moisture, which are key first-order variables of the Earth's weather equation. Simultaneous measurement of these parameters at fast revisit rates promises large advancements in our weather predictive skills. Such capabilities would: a) yield greatly improved initial conditions for models, b) make obsolete existing (discrete) measurement approaches which are both costly and cumbersome, and c) obviate the use of numerical techniques needed to correct data obtained using present methods. Additionally, simultaneous synoptic Lidar observations would lead to improvements in model parameters, and in our knowledge of small-scale weather processes. A Dial Lidar system could simultaneously measure winds, temperatures, and humidity through a combination of Doppler and Differential Absorption techniques. Also, such a system would provide basic aerosol (dry dust) measurement capabilities that could have an impact on Earth radiation budget measurements. On the technical side, a geosynchronous Lidar DAR system would require transmit optics of a few meters in diameter, a hundred meter diameter receive telescope, fineness of both optical systems scaled to the wavelength, and scanning for the transmit system. Potential technology issues include optical quality of large transmit and receive telescope optics, the large detector area needed, the transmit scanning system, signal detection (S/N ratio of detector system) for the extremely weak return signal at GEO, and power demands in the KW range.

  1. Screening Technique for Lead and Cadmium in Toys and Other Materials Using Atomic Absorption Spectroscopy

    ERIC Educational Resources Information Center

    Brouwer, Henry

    2005-01-01

    A simple procedure to quickly screen different consumer products for the presence of lead, cadmium, and other metals is described. This screening technique avoids expending a lot of preparation time on samples known to contain low levels of hazardous metals where only samples testing positive for the desired elements need to be analyzed…

  2. Mid-infrared carbon monoxide detection system using differential absorption spectroscopy technique

    NASA Astrophysics Data System (ADS)

    Dong, Ming; Sui, Yue; Li, Guo-lin; Zheng, Chuan-tao; Chen, Mei-mei; Wang, Yi-ding

    2015-11-01

    A differential carbon monoxide (CO) concentration sensing device using a self-fabricated spherical mirror (e.g. light-collector) and a multi-pass gas-chamber is presented in this paper. Single-source dual-channel detection method is adopted to suppress the interferences from light source, optical path and environmental changes. Detection principle of the device is described, and both the optical part and the electrical part are developed. Experiments are carried out to evaluate the sensing performance on CO concentration. The results indicate that at 1.013×105 Pa and 298 K, the limit of detection (LoD) is about 11.5 mg/m3 with an absorption length of 40 cm. As the gas concentration gets larger than 115 mg/m3 (1.013×105 Pa, 298 K), the relative detection error falls into the range of -1.7%—+1.9%. Based on 12 h long-term measurement on the 115 mg/m3 and 1 150 mg/m3 CO samples, the maximum detection errors are about 0.9% and 5.5%, respectively. Due to the low cost and competitive characteristics, the proposed device shows potential applications in CO detection in the circumstances of coal-mine production and environmental protection.

  3. Multilayer Thin Film Polarizer Design for Far Ultraviolet using Induced Transmission and Absorption Technique

    NASA Technical Reports Server (NTRS)

    Kim, Jongmin; Zukic, Muamer; Wilson, Michele M.; Park, Jung Ho; Torr, Douglas G.

    1994-01-01

    Good theoretical designs of far ultraviolet polarizers have been reported using a MgF2/Al/MgF2 three layer structure on a thick Al layer as a substrate. The thicknesses were determined to induce transmission and absorption of p-polarized light. In these designs Al optical constants were used from films produced in ultrahigh vacuum (UHV: 10(exp -10) torr). Reflectance values for polarizers fabricated in a conventional high vacuum (p approx. 10(exp -6 torr)) using the UHV design parameters differed dramatically from the design predictions. Al is a highly reactive material and is oxidized even in a high vacuum chamber. In order to solve the problem other metals have been studied. It is found that a larger reflectance difference is closely related to higher amplitude and larger phase difference of Fresnel reflection coefficients between two polarizations at the boundary of MgF2/metal. It is also found that for one material a larger angle of incidence from the surface normal brings larger amplitude and phase difference. Be and Mo are found good materials to replace Al. Polarizers designed for 121.6 nm with Be at 60 deg and with Mo at 70 deg are shown as examples.

  4. Solid-State 2-Micron Laser Transmitter Advancement for Wind and Carbon Dioxide Measurements From Ground, Airborne, and Space-Based Lidar Systems

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Kavaya, Michael J.; Koch, Grady; Yu, Jirong; Ismail, Syed

    2008-01-01

    NASA Langley Research Center has been developing 2-micron lidar technologies over a decade for wind measurements, utilizing coherent Doppler wind lidar technique and carbon dioxide measurements, utilizing Differential Absorption Lidar (DIAL) technique. Significant advancements have been made towards developing state-of-the-art technologies towards laser transmitters, detectors, and receiver systems. These efforts have led to the development of solid-state lasers with high pulse energy, tunablility, wavelength-stability, and double-pulsed operation. This paper will present a review of these technological developments along with examples of high resolution wind and high precision CO2 DIAL measurements in the atmosphere. Plans for the development of compact high power lasers for applications in airborne and future space platforms for wind and regional to global scale measurement of atmospheric CO2 will also be discussed.

  5. Performance Modeling of an Airborne Raman Water Vapor Lidar

    NASA Technical Reports Server (NTRS)

    Whiteman, D. N.; Schwemmer, G.; Berkoff, T.; Plotkin, H.; Ramos-Izquierdo, L.; Pappalardo, G.

    2000-01-01

    A sophisticated Raman lidar numerical model had been developed. The model has been used to simulate the performance of two ground-based Raman water vapor lidar systems. After tuning the model using these ground-based measurements, the model is used to simulate the water vapor measurement capability of an airborne Raman lidar under both day-and night-time conditions for a wide range of water vapor conditions. The results indicate that, under many circumstances, the daytime measurements possess comparable resolution to an existing airborne differential absorption water vapor lidar while the nighttime measurement have higher resolution. In addition, a Raman lidar is capable of measurements not possible using a differential absorption system.

  6. Folic acid absorption determined by a single stool sample test--a double-isotope technique. The folic acid absorption capacity in children

    SciTech Connect

    Hjelt, K. )

    1989-10-01

    The fractional folic acid absorption (FAFol) was determined in 66 patients with various gastrointestinal diseases by a double-isotope technique, employing a single stool sample test (SSST) as well as a complete stool collection. The age of the patients ranged from 2.5 months to 16.8 years (mean 6.3 years). The test dose was administered orally and consisted of 50 micrograms of (3H)folic acid (monoglutamate) (approximately 20 muCi), carmine powder, and 2 mg 51CrCl3 (approximately 1.25 muCi) as the unabsorbable tracer. The whole-body radiation given to a 1-year-old child averaged 4.8 mrad only. The stool and napkin contents were collected and homogenized by the addition of 300 ml chromium sulfuric acid. A 300-ml sample of the homogenized stool and napkin contents, as well as 300 ml chromium sulfuric acid (75% vol/vol) containing the standards, were counted for the content of 51Cr in a broad-based well counter. The quantity of (3H)folic acid was determined by liquid scintillation, after duplicate distillation. Estimated by SSST, the FAFol, which employs the stool with the highest content of 51Cr corresponding to the most carmine-colored stool, correlated closely with the FAFol based on complete stool collection (r = 0.96, n = 39, p less than 0.0001). The reproducibility of FAFol determined by SSST was assessed from repeated tests in 18 patients. For a mean of 81%, the SD was 4.6%, which corresponded to a coefficient of variation of 5.7%.

  7. Lidar Measurements for Desert Dust Characterization: An Overview

    NASA Technical Reports Server (NTRS)

    Mona, L.; Liu, Z.; Mueller, D.; Omar, A.; Papayannis, A.; Pappalardo, G.; Sugimoto, N.; Vaughan, M.

    2012-01-01

    We provide an overview of light detection and ranging (lidar) capability for describing and characterizing desert dust. This paper summarizes lidar techniques, observations, and fallouts of desert dust lidar measurements. The main objective is to provide the scientific community, including non-practitioners of lidar observations with a reference paper on dust lidar measurements. In particular, it will fill the current gap of communication between research-oriented lidar community and potential desert dust data users, such as air quality monitoring agencies and aviation advisory centers. The current capability of the different lidar techniques for the characterization of aerosol in general and desert dust in particular is presented. Technical aspects and required assumptions of these techniques are discussed, providing readers with the pros and cons of each technique. Information about desert dust collected up to date using lidar techniques is reviewed. Lidar techniques for aerosol characterization have a maturity level appropriate for addressing air quality and transportation issues, as demonstrated by some first results reported in this paper

  8. Lidar base specification

    USGS Publications Warehouse

    Heidemann, Hans Karl.

    2012-01-01

    Lidar is a fast evolving technology, and much has changed in the industry since the final draft of the “Lidar Base Specification Version 1.0” was written. Lidar data have improved in accuracy and spatial resolution, geospatial accuracy standards have been revised by the American Society for Photogrammetry and Remote Sensing (ASPRS), industry standard file formats have been expanded, additional applications for lidar have become accepted, and the need for interoperable data across collections has been realized. This revision to the “Lidar Base Specification Version 1.0” publication addresses those changes and provides continued guidance towards a nationally consistent lidar dataset.

  9. Estimation of the efficiency of the hybrid LIDAR-DOAS system of lidar sensing of the polluted atmosphere using pulsed excilamps

    NASA Astrophysics Data System (ADS)

    Krekov, G. M.; Krekova, M. M.; Lisenko, A. A.; Sukhanov, A. Ya.; Erofeev, M. V.; Lomaev, M. I.; Tarasenko, V. F.

    2010-12-01

    Results of a closed numerical experiment on laser sensing of minor gas impurity concentrations in the tropospheric layer of the atmosphere based on new hybrid LIDAR-DOAS technique with a XeCl* excilamp used for a pulsed wideband radiation source are discussed. Quantitative estimates obtained using a new stochastic genetic search algorithm confirm that the suggested approach, expanding the possibilities of the classical Differential Optical Absorption Spectroscopy (DOAS) system to remote monitoring and localization of dangerous anthropogenic emissions of toxic gases up to the tropopause height, is promising. The necessity of estimating backscattered signals with high spectral resolution by solving the nonstationary radiative transfer equation calls for a significant modification of the statistical simulation algorithms. A combination of the Monte Carlo method with a genetic algorithm of solving inverse problems of reconstructing profiles of gaseous components in the troposphere enables exact quantitative prediction of the efficiency of new promising lidar systems of environmental monitoring to be provided.

  10. InGaAsSb Detectors Characterization for 2-Micron CO2 Lidar/DIAL Applications

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Abedin, M. Nurul; Koch, Grady J.; Singh, Upendra N.

    2003-01-01

    Recent interest in monitoring atmospheric CO2 focuses attention on infrared remote sensing using the 2-micron lidar/differential absorption lidar (DIAL) technique. Quantum detectors are critical components in this technique, and many research efforts concentrate on developing such devices for the 2-micron wavelength. Characterization results of InGaAsSb quantum detectors for the 2-micron wavelength range are presented, including experimental setup and procedure. Detectors are prototype devices manufactured by using separate absorption and multiplication (SAM) structures. Characterization experiments include V-I measurements, spectral response and its variation with bias voltage and temperature, noise measurements, noise-equivalent-power (NEP) and detectivity calculations, and signal-to-noise ratio (SNR) estimation. A slight increase in the output signal occurred with increased bias voltage and was associated with a noise level increase. Cooling down the detectors reduces noise and shifts the cutoff wavelength to shorter values. Further improvement in the design and manufacturing process, by increasing the device gain and lowering its noise level, is necessary to meet the required CO2 lidar/DIAL specifications.

  11. InGaAsSb Detectors' Characterization for 2-Micron CO2 Lidar/DIAL Applications

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Abedin, M. Nurul; Koch, Grady J.; Singh, Upendra N.

    2003-01-01

    Recent interest in monitoring atmospheric CO2 focuses attention on infrared remote sensing using the 2-micron lidar/differential absorption lidar (DIAL) technique. Quantum detectors are critical components in this technique, and many research efforts concentrate on developing such devices for the 2-micron wavelength. Characterization results of InGaAsSb quantum detectors for the 2-micron wavelength range are presented, including experimental setup and procedure. Detectors are prototype devices manufactured by using separate absorption and multiplication (SAM) structures. Characterization experiments include V-I measurements, spectral response and its variation with bias voltage and temperature, noise measurements, noise-equivalent-power (NEP) and detectivity calculations, and signal-to-noise ratio (SNR) estimation. A slight increase in the output signal occurred with increased bias voltage and was associated with a noise level increase. Cooling down the detectors reduces noise and shifts the cutoff wavelength to shorter values. Further improvement in the design and manufacturing process, by increasing the device gain and lowering its noise level, is necessary to meet the required CO2 lidar/DIAL specifications.

  12. High-resolution measurements of humidity and temperature with lidar

    NASA Astrophysics Data System (ADS)

    Behrendt, Andreas; Wulfmeyer, Volker; Spaeth, Florian; Hammann, Eva; Muppa, Shravan Kumar; Metzendorf, Simon; Riede, Andrea

    2015-04-01

    3-dimensional thermodynamic fields of temperature and moisture including their turbulent fluctuations have been observed with the two scanning lidar systems of University of Hohenheim in three field campaigns in 2013 and 2014. In this contribution, we will introduce these two self-developed instruments and illustrate their performance with measurement examples. Finally, an outlook to envisioned future research activities with the new data sets of the instruments is given. Our temperature lidar is based on the rotational Raman technique. The scanning rotational Raman lidar (RRL) uses a seeded frequency-doubled Nd:YAG laser at a wavelength of 355 nm. A two-mirror scanner with a 40-cm telescope collects the atmospheric backscatter signals. Humidity measurements are made with a scanning water vapor differential absorption lidar (DIAL) which uses a titanium sapphire laser at 820 nm as transmitter. This laser is pumped with a frequency-doubled Nd:YAG laser and injection-seeded for switching between the online and offline wavelengths. The DIAL receiver consists of a scanning 80-cm telescope. The measured temperature and humidity profiles of both instruments have typical resolutions of only a few seconds and 100 m in the atmospheric boundary layer both in day- and night-time. Recent field experiments with the RRL and the DIAL of University of Hohenheim were (1) the HD(CP)2 Prototype Experiment (HOPE) in spring 2013 in western Germany - this activity is embedded in the project HD(CP)2 (High-definition clouds and precipitation for advancing climate prediction); (2) a measurement campaign in Hohenheim in autumn 2013; (3) the campaign SABLE (Surface Atmospheric Boundary Layer Exchange) in south-western Germany in summer 2014. The collected moisture and temperature data will serve as initial thermodynamic fields for forecast experiments related to the formation of clouds and precipitation. Due to their high resolution and high precision, the systems are capable of resolving

  13. Microbial growth on pall rings: a problem when upgrading biogas with the water-wash absorption technique.

    PubMed

    Tynell, Asa; Börjesson, Gunnar; Persson, Margareta

    2007-01-01

    Biogas is upgraded using an absorption with water-wash technique by 11 of a total of 14 upgrading plants in Sweden. However, problems with microbial growth on the pall rings in the absorption column, and in one case in the desorption column, have a negative impact on the upgrading of raw gas to vehicle gas. Five of the nine biogas plants studied here have experienced problems with microbial growth. The objectives of this study were to identify such microbial growth and to determine possible factors for its control, in order to provide recommendations for process management. A questionnaire was sent out and visits were made to the upgrading plants to collect information about the upgrading process. Phospholipid fatty acid (PLFA) analysis was performed to determine microbial biomass and community structure in samples from four upgrading plants. In samples from two of the plants, methane-oxidizing bacteria (type I methanotrophs) were indicated, while samples from one of the other plants showed biomarkers indicating actinomycetes. Factors affecting development of microbial growth were found to be water quality and the pH and temperature of the process water. Plants that used wastewater in the upgrading process experienced far more problems than those using clean water of drinking quality.

  14. Absolute OH concentration profiles measurements in high pressure counterflow flames by coupling LIF, PLIF, and absorption techniques

    NASA Astrophysics Data System (ADS)

    Matynia, A.; Idir, M.; Molet, J.; Roche, C.; de Persis, S.; Pillier, L.

    2012-08-01

    A high-pressure combustion chamber enclosing counterflow burners was set-up at ICARE-CNRS laboratory. It allows the stabilization of flat twin premixed flames at atmospheric and high pressure. In this study, lean and stoichiometric methane/air counterflow premixed flames were studied at various pressures (0.1 MPa to 0.7 MPa). Relative OH concentration profiles were measured by Laser Induced Fluorescence. Great care was attached to the determination of the fluorescence signal by taking into account the line broadening and deexcitation by quenching which both arise at high pressure. Subsequently, OH profiles were calibrated in concentration by laser absorption technique associated with planar laser induced fluorescence. Results are successfully compared with literature. The good quality of the results attests of the experimental set-up ability to allow the study of flame structure at high pressure.

  15. Airborne Light Detection and Ranging (lidar) Derived Deformation from the MW 6.0 24 August, 2014 South Napa Earthquake Estimated by Two and Three Dimensional Point Cloud Change Detection Techniques

    NASA Astrophysics Data System (ADS)

    Lyda, A. W.; Zhang, X.; Glennie, C. L.; Hudnut, K.; Brooks, B. A.

    2016-06-01

    Remote sensing via LiDAR (Light Detection And Ranging) has proven extremely useful in both Earth science and hazard related studies. Surveys taken before and after an earthquake for example, can provide decimeter-level, 3D near-field estimates of land deformation that offer better spatial coverage of the near field rupture zone than other geodetic methods (e.g., InSAR, GNSS, or alignment array). In this study, we compare and contrast estimates of deformation obtained from different pre and post-event airborne laser scanning (ALS) data sets of the 2014 South Napa Earthquake using two change detection algorithms, Iterative Control Point (ICP) and Particle Image Velocimetry (PIV). The ICP algorithm is a closest point based registration algorithm that can iteratively acquire three dimensional deformations from airborne LiDAR data sets. By employing a newly proposed partition scheme, "moving window," to handle the large spatial scale point cloud over the earthquake rupture area, the ICP process applies a rigid registration of data sets within an overlapped window to enhance the change detection results of the local, spatially varying surface deformation near-fault. The other algorithm, PIV, is a well-established, two dimensional image co-registration and correlation technique developed in fluid mechanics research and later applied to geotechnical studies. Adapted here for an earthquake with little vertical movement, the 3D point cloud is interpolated into a 2D DTM image and horizontal deformation is determined by assessing the cross-correlation of interrogation areas within the images to find the most likely deformation between two areas. Both the PIV process and the ICP algorithm are further benefited by a presented, novel use of urban geodetic markers. Analogous to the persistent scatterer technique employed with differential radar observations, this new LiDAR application exploits a classified point cloud dataset to assist the change detection algorithms. Ground

  16. Lidar Measurements of Ozone in the Upper Troposphere - Lower Stratosphere at Siberian Lidar Station in Tomsk

    NASA Astrophysics Data System (ADS)

    Romanovskii, O. A.; Dolgii, S. I.; Burlakov, V. D.; Nevzorov, A. A.; Nevzorov, A. V.

    2016-06-01

    The paper presents the results of DIAL measurements of the vertical ozone distribution at the Siberian lidar station. Sensing is performed according to the method of differential absorption and scattering at wavelength pair of 299/341 nm, which are, respectively, the first and second Stokes components of SRS conversion of 4th harmonic of Nd:YAG laser (266 nm) in hydrogen. Lidar with receiving mirror 0.5 m in diameter is used to implement sensing of vertical ozone distribution in altitude range of 6-16 km. The temperature correction of zone absorption coefficients is introduced in the software to reduce the retrieval errors.

  17. A technique for measurement of material damping in metals. [absorption of structural vibration

    NASA Technical Reports Server (NTRS)

    Heine, J. C.

    1976-01-01

    The paper outlines the theory, design, and application of an apparatus based on the single beam resonant dwell technique to determine the damping capacity of metallic materials by measuring the response of a structural element to excitation at a modal frequency. In this apparatus, a cantilever beam specimen of a test material is clamped to a bar which is connected at one end to an electromagnetic shaker and at the other to a heavy base. The thickness of the bar at the base end is reduced by two saw cuts to provide a pivot around which the remainder of the bar can rotate when excited by the shaker which is connected to the bar by a rod passing through a hole in the base. The response of the supporting system to shaker excitation is measured with an accelerometer mounted on the bar at the root of the specimen. Specimen response is measured optically with a low-power microscope with a reticle. Specimen loss factor is determined in terms of acceleration at the beam root, beam tip displacement, and the beam natural frequency.

  18. Lidar evaluation of smoke and dust clouds.

    PubMed

    Uthe, E E

    1981-05-01

    Lidar provides the means to evaluate quantitatively the spatial and temporal variability of smoke and dust clouds as they are transported downwind from particulate sources. Quantitative evaluation of cloud optical and physical densities from cloud backscatter is complicated by effects from particle size, shape, and composition and by attenuation and multiple scattering for dense clouds. Examples are presented that review use of the lidar technique to provide useful evaluations of smoke and dust clouds.

  19. Continuous wave lidar measurement of atmospheric visibility

    NASA Technical Reports Server (NTRS)

    Bufton, J. L.; Iyer, R. S.

    1978-01-01

    The technique of measurement of phase shift with a modulated CW lidar system for the purpose of atmospheric visibility assessment was evaluated both theoretically and experimentally. A closed form solution for prediction of phase shift as a function of visibility and modulation frequency was developed. Data obtained with a bistatic CW lidar configuration were compared with predictions. Results indicate the expected trends with equipment parameters and call for more extensive experiments.

  20. Photochemistry of acetylenic ketones in micellar solutions as studied by product-yield-detected ESR and transient absorption techniques.

    PubMed

    Polyakov, N E; Okazaki, M; Fukaya, H; Fujiwara, Y; Tanimoto, Y

    1995-06-01

    The electron spin resonance (ESR) spectra of the transient radical pairs in the photoreduction of 1,5-diphenyl-1,4-pentadiyn-3-one(I) and 1,3-diphenyl-2-propyn-1-one(II) in sodium dodecyl sulfate (SDS) micellar solutions have been obtained by using the product-yield-detected ESR (PYESR) technique. The PYESR spectra, detected by tracing the microwave effect on the spin-adduct yield as functions of the magnetic field, show the ESR spectra of the ketyl radical of the ketone and SDS radical as the components of the radical pairs. In addition, the growth and the decay processes of the radical pair were observed through detecting the effect of microwave pulse as functions of the delay period between a laser pulse and the off and on time, respectively, of a microwave pulse. The absorption spectra of transient species have also been obtained by using the laser flash photolysis technique. Through the analysis of these data and molecular orbital calculations, the role of acetylenic groups in the photoreactivity of acetylenic ketones is discussed.

  1. Lidar vegetation mapping in national parks: Gulf Coast Network

    USGS Publications Warehouse

    Brock, John C.; Palaseanu-Lovejoy, Monica; Segura, Martha

    2011-01-01

    Airborne lidar (Light Detection and Ranging) is an active remote sensing technique used to collect accurate elevation data over large areas. Lidar provides an extremely high level of regional topographic detail, which makes this technology an essential component of U.S. Geological Survey (USGS) science strategy. The USGS Coastal and Marine Geology Program (CMGP) has collaborated with the National Aeronautics and Space Administration (NASA) and the National Park Service (NPS) to acquire dense topographic lidar data in a variety of coastal environments.

  2. Improved oral absorption and chemical stability of everolimus via preparation of solid dispersion using solvent wetting technique.

    PubMed

    Jang, Sun Woo; Kang, Myung Joo

    2014-10-01

    The aim of this study was to improve the physicochemical properties and oral absorption of poorly water-soluble everolimus via preparation of a solid dispersion (SD) system using a solvent wetting (SW) technique. The physicochemical properties, drug release profile, and bioavailability of SD prepared by SW process were also compared to SD prepared by the conventional co-precipitation method. Solid state characterizations using scanning electron microscopy, particle size analysis and X-ray powder diffraction indicated that drug homogeneously dispersed and existed in an amorphous state within the intact polymeric carrier. Whereas, a film-like mass was obtained by a co-precipitation method and further pulverization step was needed for tabletization. The drug release from the SD tablet prepared by SW process at a ratio of drug to hydroxypropyl methylcellulose of 1:15 was markedly higher than the drug alone and equivalent to the marketed product (Afinitor(®), Novartis Pharmaceuticals), a SD tablet prepared by co-precipitation method, archiving over 75% the drug release after 30 min. At the accelerated (40°C/75% R.H.) and stress (80°C) stability tests, the novel formula was more stable than drug powder and provided comparable drug stability with the commercially available product, which contains a potentially risky antioxidant, butylated hydroxyl toluene. The pharmacokinetic parameters after single oral administration in beagles showed no significant difference (P>0.01) between the novel SD-based tablet and the marketed product. The results of this study, therefore, suggest that the novel SD system prepared by the solvent wetting process may be a promising approach for improving the physicochemical stability and oral absorption of the sirolimus derivatives. PMID:25003829

  3. Mobile lidar system for measurement of water vapor mixing ratio and ozone number density

    NASA Technical Reports Server (NTRS)

    Whiteman, D.

    1988-01-01

    The Water Vapor Lidar was modified and extended to make differential absorption measurements of ozone. Water vapor measurements make use of a weak molecular scattering process known as Raman scattering. It is characterized by a shift in wavelength of the scattered beam of light relative to the incident one. Some of the energy of the incident photon is converted to vibrational or rotational energy within the molecule leaving the scattered photon shifted to a slightly longer wavelength. When performing water vapor measurements, profiles are acquired of water vapor mixing ratio from near the ground to beyond 7 km every 2 minutes. By forming a color composite image of the individual profiles, the spatial and temporal evolution of water vapor is visible with vertical resolution of 75 to 150m and temporal resolution of 2 minutes. The ozone lidar is intended for use as a cross calibration facility for other stationary ozone lidar systems. The ozone measurement employs the technique known as differential absorption. The backscattered laser radiation from two different wavelengths is measured. Successful measurements of 308 nm returns were made from 80 km with an averaging period of 6 hours. Using these data and a standard atmosphere density curve, an ozone number density profile was made which agrees very well with the standard ozone curve between 20 and 40 km.

  4. A combined Raman lidar for low tropospheric studies

    NASA Technical Reports Server (NTRS)

    Arshinov, Y. F.; Bobrovnikov, S. M.; Zuev, V. E.; Nadeev, A. I.; Shelevoy, K. D.

    1986-01-01

    One of the main goals of laser sensing of the atmosphere was the development of techniques and facilities for remote determination of atmospheric meteorological and optical parameters. Of lidar techniques known at present the Raman-lidar technique occupies a specific place. On the one hand Raman lidar returns due to scattering on different molecular species are very simple for interpretation and for extracting the information on the atmospheric parameters sought, but, on the other hand, the performance of these techniques in a lidar facility is overburdened with some serious technical difficulties due to extremely low cross sections of Raman effect. Some results of investigations into this problem is presented which enables the construction of a combined Raman lidar capable of acquiring simultaneously the profiles of atmospheric temperature, humidity, and some optical characteristics in the ground atmospheric layer up to 1 km height. The operation of this system is briefly discussed.

  5. A preliminary study of air-pollution measurement by active remote-sensing techniques

    NASA Technical Reports Server (NTRS)

    Wright, M. L.; Proctor, E. K.; Gasiorek, L. S.; Liston, E. M.

    1975-01-01

    Air pollutants are identified, and the needs for their measurement from satellites and aircraft are discussed. An assessment is made of the properties of these pollutants and of the normal atmosphere, including interactions with light of various wavelengths and the resulting effects on transmission and scattering of optical signals. The possible methods for active remote measurement are described; the relative performance capabilities of double-ended and single-ended systems are compared qualitatively; and the capabilities of the several single-ended or backscattering techniques are compared quantitatively. The differential-absorption lidar (DIAL) technique is shown to be superior to the other backscattering techniques. The lidar system parameters and their relationships to the environmental factors and the properties of pollutants are examined in detail. A computer program that models both the atmosphere (including pollutants) and the lidar system is described. The performance capabilities of present and future lidar components are assessed, and projections are made of prospective measurement capabilities for future lidar systems. Following a discussion of some important operational factors that affect both the design and measurement capabilities of airborne and satellite-based lidar systems, the extensive analytical results obtained through more than 1000 individual cases analyzed with the aid of the computer program are summarized and discussed. The conclusions are presented. Recommendations are also made for additional studies to investigate cases that could not be explored adequately during this study.

  6. A New Raman DIAL Technique for Measuring Stratospheric Ozone in the Presence of Volcanic Aerosols

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Mcgee, Thomas J.; Gross, Michael; Heaps, William S.; Ferrare, Richard

    1992-01-01

    This paper describes a new lidar scheme to measure stratospheric ozone in the presence of heavy volcanic aerosol loading. The eruptions of the Philippine volcano Pinatubo during June 1991 ejected large amounts of sulfur dioxide into the atmosphere to altitudes of at least 30 km. The resulting aerosols have severely affected the measurements of stratospheric ozone when using traditional Rayleigh differential absorption lidar (DIAL) technique, in which the scattering mechanism is almost entirely Rayleigh and which assumes a small amount or no aerosols. In order to extract an ozone profile in the regions below about 30 km where the Rayleigh lidar returns are contaminated by aerosol scattering from Mt. Pinatubo cloud, we have used a Raman lidar technique, where the scattering mechanism depends solely on molecular nitrogen. In this scheme there is no aerosol scattering component to the backscattered lidar return. Using this technique in conjunction with the Rayleigh DIAL measurement, the GSFC stratospheric ozone lidar has measured ozone profiles between 15 and 50 km during the recently held UARS correlative measurement campaign (February-March 1992) at JPL's Table Mountain Facility in California.

  7. Lidar beams in opposite directions for quality assessment of Cloud-Aerosol Lidar with Orthogonal Polarization spaceborne measurements.

    PubMed

    Cuesta, Juan; Flamant, Pierre H

    2010-04-20

    We present the "lidar beams in opposite directions" (LIBOD) technique and applications for quality assessment of spaceborne observations made by Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) onboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite. LIBOD is applicable to standard total backscatter lidar because it does not require a priori knowledge of the particle extinction-to-backscatter ratio. In this paper, we present (i) an objective assessment of the lidar signal quality and representativity of correlative ground-based lidar and CALIOP measurements only using normalized range-corrected lidar signals and (ii) a numerical filtering and optimization technique for reducing the spurious oscillations induced by noisy signal differentiation as needed for retrieval of particle extinction coefficients and extinction-to-backscatter ratio profiles. Numerical simulations and Monte Carlo tests are conducted for assessing the performance of the LIBOD technique. The applications are illustrated with examples of actual correlative 532 nm lidar profiles from CALIOP and a ground-based lidar deployed in Tamanrasset in the heart of Sahara in 2006 and near Strasbourg, France, in 2007.

  8. GLOW: The Goddard Lidar Observatory for Winds

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Chen, Huailin; Li, Steven X.; Einaudi, Franco (Technical Monitor)

    2000-01-01

    GLOW (Goddard Lidar Observatory for Winds) is a mobile Doppler lidar system which uses direct detection Doppler lidar techniques to measure wind profiles from the surface into the lower stratosphere. The system is contained in a modified van to allow deployment in field operations. The lidar system uses a Nd:YAG laser transmitter to measure winds using either aerosol backscatter at 1064 nm or molecular backscatter at 355 nm. The receiver telescope is a 45 cm Dall-Kirkham which is fiber coupled to separate Doppler receivers, one optimized for the aerosol backscatter wind measurement and another optimized for the molecular backscatter wind measurement. The receivers are implementations of the 'double edge' technique and use high spectral resolution Fabry-Perot etalons to measure the Doppler shift. A 45 cm aperture azimuth-over-elevation scanner is mounted on the roof of the van to allow full sky access and a variety of scanning options. GLOW is intended to be used as a deployable field system for studying atmospheric dynamics and transport and can also serve as a testbed to evaluate candidate technologies developed for use in future spaceborne systems. In addition, it can be used for calibration/validation activities following launch of spaceborne wind lidar systems. A description of the mobile system is presented along with the examples of lidar wind profiles obtained with the system.

  9. GLOW- The Goddard Lidar Observatory for Winds

    NASA Technical Reports Server (NTRS)

    Gentry, Bruce M.; Chen, Huailin; Li, Steven X.

    2000-01-01

    GLOW (Goddard Lidar Observatory for Winds) is a mobile Doppler lidar system which uses direct detection Doppler lidar techniques to measure wind profiles from the surface into the lower stratosphere. The system is contained in a modified van to allow deployment in field operations. The lidar system uses a Nd:YAG laser transmitter to measure winds using either aerosol backscatter at 1064 nm or molecular backscatter at 355 nm. The receiver telescope is a 45 cm Dall-Kirkham which is fiber coupled to separate Doppler receivers, one optimized for the aerosol backscatter wind measurement and another optimized for the molecular backscatter wind measurement. The receivers are implementations of the 'double edge' technique and use high spectral resolution Fabry-Perot etalons to measure the Doppler shift. A 45 cm aperture azimuth-over-elevation scanner is mounted on the roof of the van to allow full sky access and a variety of scanning options. GLOW is intended to be used as a deployable field system for studying atmospheric dynamics and transport and can also serve as a testbed to evaluate candidate technologies developed for use in future spaceborne systems. In addition, it can be used for calibration/validation activities following launch of spaceborne wind lidar systems. A description of the mobile system is presented along with the examples of lidar wind profiles obtained with the system.

  10. Tomographic multiaxis-differential optical absorption spectroscopy observations of Sun-illuminated targets: a technique providing well-defined absorption paths in the boundary layer.

    PubMed

    Frins, Erna; Bobrowski, Nicole; Platt, Ulrich; Wagner, Thomas

    2006-08-20

    A novel experimental procedure to measure the near-surface distribution of atmospheric trace gases by using passive multiaxis differential absorption optical spectroscopy (MAX-DOAS) is proposed. The procedure consists of pointing the receiving telescope of the spectrometer to nonreflecting surfaces or to bright targets placed at known distances from the measuring device, which are illuminated by sunlight. We show that the partial trace gas absorptions between the top of the atmosphere and the target can be easily removed from the measured total absorption. Thus it is possible to derive the average concentration of trace gases such as NO(2), HCHO, SO(2), H(2)O, Glyoxal, BrO, and others along the line of sight between the instrument and the target similar to the well-known long-path DOAS observations (but with much less expense). If tomographic arrangements are used, even two- or three-dimensional trace gas distributions can be retrieved. The basic assumptions of the proposed method are confirmed by test measurements taken across the city of Heidelberg. PMID:16892129

  11. A compact high repetition rate CO2 coherent Doppler lidar

    NASA Technical Reports Server (NTRS)

    Alejandro, S.; Frelin, R.; Dix, B.; Mcnicholl, P.

    1992-01-01

    As part of its program to develop coherent heterodyne detection lidar technology for space, airborne, and ground based applications, the Optical Environment Division of the USAF's Phillips Laboratory developed a compact coherent CO2 TEA lidar system. Although originally conceived as a high altitude balloon borne system, the lidar is presently integrated into a trailer for ground based field measurements of aerosols and wind fields. In this role, it will also serve as a testbed for signal acquisition and processing development for planned future airborne and space based solid state lidar systems. The system has also found significance in new areas of interest to the Air Force such as cloud studies and coherent Differential Absorption Lidar (DIAL) systems.

  12. Remote sensing of chemical warfare agent by CO2 -lidar

    NASA Astrophysics Data System (ADS)

    Geiko, Pavel P.; Smirnov, Sergey S.

    2014-11-01

    The possibilities of remote sensing of chemical warfare agent by differential absorption method were analyzed. The CO2 - laser emission lines suitable for sounding of chemical warfare agent with provision for disturbing absorptions by water vapor were choose. The detection range of chemical warfare agents was estimated for a lidar based on CO2 - laser The other factors influencing upon echolocation range were analyzed.

  13. Gas correlation lidar for methane detection

    NASA Technical Reports Server (NTRS)

    Galletti, E.; Zanzottera, E.; Draghi, S.; Garbi, M.; Petroni, R.

    1986-01-01

    A new type of DIAL system for the detection of methane in the atmosphere is being developed. The main feature of this lidar is the use of a gas correlation technique to obtain the reference signal by means of a single laser pulse, instead of two shots at different wavelengths. This fact is useful to make measurements on fast moving platforms. To meet the infrared absorption band of methane an optical parametric oscillator (OPO) was used with a LiNbO3 crystal as active element, and a tuning range between 1.5 divided by 4 microns. As known, the major problem to overcome in parametric oscillators are the pump beam quality and the difficulty in reducing the linewidth. The first requirement is met by using, as a pump, a Nd-YAG laser based on a new type of resonator cavity, named SFUR (Self Filtering Unstable Resonator). The laser emits, with high efficiency, near diffraction limited pulsed beams of about 250 mJ of energy, 20 ns of duration at 10 pps of frequency repetition rate. On the other hand, the gas correlation technique allows the operation with a bandwidth as large as 1/cm, which is obtainable using only a diffraction grating as a dispersive element in the OPO cavity.

  14. Zinc absorption in adult men from a chicken sandwich made with white or wholemeal bread, measured by a double-label stable-isotope technique.

    PubMed

    Fairweather-Tait, S J; Fox, T E; Wharf, S G; Eagles, J; Kennedy, H

    1992-05-01

    Eleven fasted adult men consumed a chicken meat sandwich made with white or wholemeal bread, extrinsically labelled with 2 mg 67Zn, on two different occasions. Immediately after eating the sandwich they were given an intravenous injection of 1.5 mg 70Zn. True Zn absorption (which was approximately 7% higher than apparent absorption) was determined by the faecal balance technique by making an allowance for endogenous excretion from measurements of faecal excretion of 70Zn. There was no significant difference in mean true Zn absorption from the white or wholemeal bread sandwich, 33.6 and 25.4% respectively. It was concluded that the substitution of wholemeal for white bread does not reduce Zn absorption from meat-based sandwiches.

  15. Multipulse gate-delayed range gating imaging lidar.

    PubMed

    Wu, Long; Zhao, Yuan; Zhang, Yong; Jin, Chenfei; Wu, Jie

    2011-04-15

    We present a technique to reconstruct a higher resolution of depth map of range gating imaging lidar by applying the delays of the gates to a typical range gating lidar system during the detection of each returned laser pulse with the encoding of the returned signal. With the consequent delays of the gate, the depth of the scene is extended accordingly. A multipulse gate-delayed range gating lidar system is designed to prove the resolution improvement from 6 to 1.5 m. The unchanged peak power of the laser, the widths of the laser pulse and the sampling period result in a simple structure of the lidar system. PMID:21499358

  16. Applications of the direct photon absorption technique for measuring bone mineral content in vivo. Determination of body composition in vivo

    NASA Technical Reports Server (NTRS)

    Cameron, J. R.

    1972-01-01

    The bone mineral content, BMC, determined by monoenergetic photon absorption technique, of 29 different locations on the long bones and vertebral columns of 24 skeletons was measured. Compressive tests were made on bone from these locations in which the maximum load and maximum stress were measured. Also the ultimate strain, modulus of elasticity and energy absorbed to failure were determined for compact bone from the femoral diaphysis and cancellous bone from the eighth through eleventh thoracic vertebrae. Correlations and predictive relationships between these parameters were examined to investigate the applicability of using the BMC at sites normally measured in vivo, i.e. radius and ulna in estimating the BMC and/or strength of the spine or femoral neck. It was found that the BMC at sites on the same bone were highly correlated r = 0.95 or better; the BMC at sites on different bones were also highly interrelated, r = 0.85. The BMC at various sites on the long bones could be estimated to between 10 and 15 per cent from the BMC of sites on the radius or ulna.

  17. Standardization and validation of a new atomic absorption spectroscopy technique for determination and quantitation of aluminium adjuvant in immunobiologicals.

    PubMed

    Mishra, Arti; Bhalla, Sumir Rai; Rawat, Sameera; Bansal, Vivek; Sehgal, Rakesh; Kumar, Sunil

    2007-10-01

    In the present study, Aluminium quantification in immunobiologicals has been described using atomic absorption spectroscopy (AAS) technique. The assay was found to be linear in 25-125 microg/ml Aluminium range. The procedure was found to be accurate for different vaccines with recoveries of external additions ranging between 93.26 and 103.41%. The mean Limit of Variation (L.V.) for both intra- and inter-assay precision was calculated to be 1.62 and 2.22%, respectively. Further the procedure was found to be robust in relation to digestion temperature, alteration in acid (HNO(3) and H(2)SO(4)) ratio used for sample digestion and storage of digested vaccine samples up to a period of 15 days. After validation, AAS method was compared for its equivalency with routinely used complexometric titration method. On simultaneously applying on seven different groups of both bacterial and viral vaccines, viz., DPT, DT, TT, Hepatitis-A and B, Antirabies vaccine (cell culture) and tetravalent DPT-Hib, a high degree of positive correlation (+0.85-0.998) among AAS and titration methods was observed. Further AAS method was found to have an edge over complexometric titration method that a group of vaccines, viz., ARV (cell culture, adsorbed) and Hepatitis-A, in which Aluminium estimation is not feasible by pharmacopoeial approved complexometric titration method (possibly due to some interference in the sample matrix), this newly described and validated AAS assay procedure delivered accurate and reproducible results.

  18. An efficient and accurate technique to compute the absorption, emission, and transmission of radiation by the Martian atmosphere

    NASA Technical Reports Server (NTRS)

    Lindner, Bernhard Lee; Ackerman, Thomas P.; Pollack, James B.

    1990-01-01

    CO2 comprises 95 pct. of the composition of the Martian atmosphere. However, the Martian atmosphere also has a high aerosol content. Dust particles vary from less than 0.2 to greater than 3.0. CO2 is an active absorber and emitter in near IR and IR wavelengths; the near IR absorption bands of CO2 provide significant heating of the atmosphere, and the 15 micron band provides rapid cooling. Including both CO2 and aerosol radiative transfer simultaneously in a model is difficult. Aerosol radiative transfer requires a multiple scattering code, while CO2 radiative transfer must deal with complex wavelength structure. As an alternative to the pure atmosphere treatment in most models which causes inaccuracies, a treatment was developed called the exponential sum or k distribution approximation. The chief advantage of the exponential sum approach is that the integration over k space of f(k) can be computed more quickly than the integration of k sub upsilon over frequency. The exponential sum approach is superior to the photon path distribution and emissivity techniques for dusty conditions. This study was the first application of the exponential sum approach to Martian conditions.

  19. Structural Analysis of Freshwater-Cultured Pearls with Different Lusters Using the Extended X-Ray Absorption Fine Structure Technique

    NASA Astrophysics Data System (ADS)

    Monarumit, N.; Noirawee, N.; Phlayrahan, A.; Promdee, K.; Won-in, K.; Satitkune, S.

    2016-05-01

    The quality of freshwater-cultured pearls (Chamberlainia hainesiana) is determined by their luster, which is related to the content of the two CaCO3 mineral phases: aragonite and vaterite. The atomic structures of pearl samples were analyzed by the extended X-ray absorption fine structure (EXAFS) technique using synchrotron radiation to compare the atomic environment and atomic bonding around Ca atoms of high- and low-luster pearls. The Ca K-edge EXAFS spectra of the pearl samples were determined and interpreted in terms of the photoelectron wave number and the distance between Ca atoms and neighboring atoms. From the results, the wave oscillation of high-luster pearls is less than that of low-luster pearls. This indicates the presence of the aragonite phase in high-luster pearls and a combination of aragonite and vaterite phases in low-luster pearls, especially in the fi rst and second shells of Ca atoms. It can be concluded that the different lusters of freshwater-cultured pearls are related to the different CaCO3 phases in their structures.

  20. Role of Lidar Technology in Future NASA Space Missions

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin

    2008-01-01

    The past success of lidar instruments in space combined with potentials of laser remote sensing techniques in improving measurements traditionally performed by other instrument technologies and in enabling new measurements have expanded the role of lidar technology in future NASA missions. Compared with passive optical and active radar/microwave instruments, lidar systems produce substantially more accurate and precise data without reliance on natural light sources and with much greater spatial resolution. NASA pursues lidar technology not only as science instruments, providing atmospherics and surface topography data of Earth and other solar system bodies, but also as viable guidance and navigation sensors for space vehicles. This paper summarizes the current NASA lidar missions and describes the lidar systems being considered for deployment in space in the near future.

  1. Doppler Lidar (DL) Handbook

    SciTech Connect

    Newsom, RK

    2012-02-13

    The Doppler lidar (DL) is an active remote sensing instrument that provides range- and time-resolved measurements of radial velocity and attenuated backscatter. The principle of operation is similar to radar in that pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is inferred. The radial or line-of-sight velocity of the scatterers is determined from the Doppler frequency shift of the backscattered radiation. The DL uses a heterodyne detection technique in which the return signal is mixed with a reference laser beam (i.e., local oscillator) of known frequency. An onboard signal processing computer then determines the Doppler frequency shift from the spectra of the heterodyne signal. The energy content of the Doppler spectra can also be used to determine attenuated backscatter.

  2. Airborne Measurements of Atmospheric Pressure made Using an IPDA Lidar Operating in the Oxygen A-Band

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Abshire, James B.; Stephen, Mark; Rodriquez, Michael; Allan, Graham; Hasselbrack, William; Mao, Jianping

    2012-01-01

    We report airborne measurements of atmospheric pressure made using an integrated path differential absorption (IPDA) lidar that operates in the oxygen A-band near 765 nm. Remote measurements of atmospheric temperature and pressure are needed for NASA s Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission to measure atmospheric CO2. Accurate measurements of tropospheric CO2 on a global scale are very important in order to better understand its sources and sinks and to improve our predictions of climate change. The goal of ASCENDS is to determine the CO2 dry mixing ratio with lidar measurements from space at a level of 1 ppm. Analysis to date shows that with current weather models, measurements of both the CO2 column density and the column density of dry air are needed. Since O2 is a stable molecule that uniformly mixed in the atmosphere, measuring O2 absorption in the atmosphere can be used to infer the dry air density. We have developed an airborne (IPDA) lidar for Oxygen, with support from the NASA ESTO IIP program. Our lidar uses DFB-based seed laser diodes, a pulsed modulator, a fiber laser amplifier, and a non-linear crystal to generate wavelength tunable 765 nm laser pulses with a few uJ/pulse energy. The laser pulse rate is 10 KHz, and average transmitted laser power is 20 mW. Our lidar steps laser pulses across a selected line O2 doublet near 764.7 nm in the Oxygen A-band. The direct detection lidar receiver uses a 20 cm diameter telescope, a Si APD detector in Geiger mode, and a multi-channel scalar to detect and record the time resolved laser backscatter in 40 separate wavelength channels. Subsequent analysis is used to estimate the transmission line shape of the doublet for the laser pulses reflected from the ground. Ground based data analysis allows averaging from 1 to 60 seconds to increase SNR in the transmission line shape of the doublet. Our retrieval algorithm fits the expected O2 lineshapes against the measurements and

  3. Standard methods for analysis and interpretation of Lidar data for environmental monitoring

    NASA Technical Reports Server (NTRS)

    Melfi, S. H.

    1973-01-01

    Lidar is similar in principle to microwave radar but uses a pulsed laser as the source and an optical telescope as the receiver. Lidar observations of elastic scattering from aerosols and more recently Raman scattering from molecules have been performed in the atmosphere with favorable results. A description of the Lidar technique is provided. Lidar measurements of remote visibility are discussed together with the measurement of remote visibility and the determination of molecular concentrations.

  4. Retrieval of Temperature and Water Vapour from Multiple Channel Lidar Systems Using an Optimal Estimation Method

    NASA Astrophysics Data System (ADS)

    Sica, Robert; Haefele, Alexander

    2016-04-01

    While the application of optimal estimation methods (OEMs) is well-known for the retrieval of atmospheric parameters from passive instruments, active instruments have typically not employed the OEM. For instance, the measurement of temperature in the middle atmosphere with Rayleigh-scatter lidars is an important technique for assessing atmospheric change. Current retrieval schemes for these temperatures have several shortcomings which can be overcome using an OEM. Forward models have been constructed that fully characterize the measurement and allow the simultaneous retrieval of temperature, dead time and background. The OEM allows a full uncertainty budget to be obtained on a per profile basis that includes, in addition to the statistical uncertainties, the smoothing error and uncertainties due to Rayleigh extinction, ozone absorption, the lidar constant, nonlinearity in the counting system, variation of the Rayleigh-scatter cross section with altitude, pressure, acceleration due to gravity and the variation of mean molecular mass with altitude. The vertical resolution of the temperature profile is found at each height, and a quantitative determination is made of the maximum height to which the retrieval is valid. A single temperature profile can be retrieved from measurements with multiple channels that cover different height ranges, vertical resolutions and even different detection methods. The OEM employed is shown to give robust estimates of temperature consistent with previous methods, while requiring minimal computational time. Retrieval of water vapour mixing ratio from vibrational Raman scattering lidar measurements is another example where an OEM offers a considerable advantage over the standard analysis technique, with the same advantages as discussed above for Rayleigh-scatter temperatures but with an additional benefit. The conversion of the lidar measurement into mixing ratio requires a calibration constant to be employed. Using OEM the calibration

  5. Mercury in Environmental and Biological Samples Using Online Combustion with Sequential Atomic Absorption and Fluorescence Measurements: A Direct Comparison of Two Fundamental Techniques in Spectrometry

    ERIC Educational Resources Information Center

    Cizdziel, James V.

    2011-01-01

    In this laboratory experiment, students quantitatively determine the concentration of an element (mercury) in an environmental or biological sample while comparing and contrasting the fundamental techniques of atomic absorption spectrometry (AAS) and atomic fluorescence spectrometry (AFS). A mercury analyzer based on sample combustion,…

  6. A pulsed CO2 Doppler lidar for boundary layer monitoring

    NASA Technical Reports Server (NTRS)

    Pearson, Guy N.

    1992-01-01

    A monostatic, master oscillator power amplifier (MOPA), CO2 pulsed Doppler lidar was constructed and tested. The system is compact (120 x 60 cm), operates at high pulse repetition rates (greater than 1 kHz) and is intended for simultaneous Doppler/Differential Absorption Lidar (DIAL) monitoring of the planetary boundary layer. Details of the system design, hard target calibrations, and aerosol returns are presented.

  7. Gating characteristics of photomultiplier tubes for Lidar applications

    NASA Technical Reports Server (NTRS)

    Barrick, J. D. W.

    1986-01-01

    A detector test facility was developed and applied in the evaluation and characterization of lidar detectors in support of the multipurpose airborne differential absorption lidar (DIAL) system based at the Langley Research Center (LaRC). A performance data base of various detector configurations available to the DIAL system was obtained for optimum lidar detector selection. Photomultiplier tubes (PMT's) with multialkaline and bialkaline photocathodes were evaluated in voltage-divider networks (bases) by using either the focusing electrode or dynodes as a gating mechanism. Characteristics used for detector evaluation included gain stability, signal rise time, and the ability to block unwanted high light levels.

  8. Quantitative analysis of deconvolved X-ray absorption near-edge structure spectra: a tool to push the limits of the X-ray absorption spectroscopy technique.

    PubMed

    D'Angelo, Paola; Migliorati, Valentina; Persson, Ingmar; Mancini, Giordano; Della Longa, Stefano

    2014-09-15

    A deconvolution procedure has been applied to K-edge X-ray absorption near-edge structure (XANES) spectra of lanthanoid-containing solid systems, namely, hexakis(dmpu)praseodymium(III) and -gadolinium(III) iodide. The K-edges of lanthanoids cover the energy range 38 (La)-65 (Lu) keV, and the large widths of the core-hole states lead to broadening of spectral features, reducing the content of structural information that can be extracted from the raw X-ray absorption spectra. Here, we demonstrate that deconvolution procedures allow one to remove most of the instrumental and core-hole lifetime broadening in the K-edge XANES spectra of lanthanoid compounds, highlighting structural features that are lost in the raw data. We show that quantitative analysis of the deconvolved K-edge XANES spectra can be profitably used to gain a complete local structural characterization of lanthanoid-containing systems not only for the nearest neighbor atoms but also for higher-distance coordination shells. PMID:25171598

  9. Modelling the performance of a LIDAR system for the measurement of atmospheric carbon dioxide

    NASA Astrophysics Data System (ADS)

    Lawrence, J. P.; Leigh, R. J.; Bösch, H.; Monks, P. S.; Remedios, J. J.

    2009-04-01

    With atmospheric carbon dioxide concentrations rising steadily, investigations into locations and magnitudes of the sources, sinks and net surface fluxes are of increasing importance. Active space-borne measurement systems such as LIDAR offer one potential technique to derive global, near-surface concentrations. However, significant instrumental challenges need to be overcome for such measurements to achieve a useful degree of accuracy and precision. This poster presents the work being carried out at the University of Leicester to accurately model a spaceborne LiDAR system. The model aims at providing an insight into the performance of a differential absorption LiDAR system (DIAL) based on current and future technology in a realistic environment. This is achieved by accurately modelling the surface footprint of a laser system based on expected orbital parameters, and using atmospheric profiles, topographic information and BRDF's to simulate the laser lights interaction with the environment. The model readily simulates LiDAR systems operating at 1.57 and 2.05µm wavelengths using Voigt convolved HITRAN line centres to obtain accurate vertical sensitivity to the atmosphere as a result of spectral line broadening. This method allows any spectral line to be selected and any offset from the line centre to be applied to optimize the systems performance. It also offers the potential for investigating multi-spectral LiDAR systems and the benefits that this method has versus the standard duel wavelength DIAL systems. In order to retrieve near-surface CO2 concentrations of a few ppm the resulting instrument requirements are unquestionably demanding, but provide a benchmark for new technology development initiatives such as A-SCOPE and ASCENDS.

  10. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements.

    PubMed

    Pal, Sandip

    2016-06-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features.

  11. On the factors governing water vapor turbulence mixing in the convective boundary layer over land: Concept and data analysis technique using ground-based lidar measurements.

    PubMed

    Pal, Sandip

    2016-06-01

    The convective boundary layer (CBL) turbulence is the key process for exchanging heat, momentum, moisture and trace gases between the earth's surface and the lower part of the troposphere. The turbulence parameterization of the CBL is a challenging but important component in numerical models. In particular, correct estimation of CBL turbulence features, parameterization, and the determination of the contribution of eddy diffusivity are important for simulating convection initiation, and the dispersion of health hazardous air pollutants and Greenhouse gases. In general, measurements of higher-order moments of water vapor mixing ratio (q) variability yield unique estimates of turbulence in the CBL. Using the high-resolution lidar-derived profiles of q variance, third-order moment, and skewness and analyzing concurrent profiles of vertical velocity, potential temperature, horizontal wind and time series of near-surface measurements of surface flux and meteorological parameters, a conceptual framework based on bottom up approach is proposed here for the first time for a robust characterization of the turbulent structure of CBL over land so that our understanding on the processes governing CBL q turbulence could be improved. Finally, principal component analyses will be applied on the lidar-derived long-term data sets of q turbulence statistics to identify the meteorological factors and the dominant physical mechanisms governing the CBL turbulence features. PMID:26950615

  12. Lidar/DIAL detection of bomb factories

    NASA Astrophysics Data System (ADS)

    Fiorani, Luca; Puiu, Adriana; Rosa, Olga; Palucci, Antonio

    2013-10-01

    One of the aims of the project BONAS (BOmb factory detection by Networks of Advanced Sensors) is to develop a lidar/DIAL (differential absorption lidar) to detect precursors employed in the manufacturing of improvised explosive devices (IEDs). At first, a spectroscopic study has been carried out: the infrared (IR) gas phase spectrum of acetone, one of the more important IED precursors, has been procured from available databases and checked with cell measurements. Then, the feasibility of a lidar/DIAL for the detection of acetone vapors has been shown in laboratory, simulating the experimental conditions of a field campaign. Eventually, having in mind measurements in a real scenario, an interferent study has been performed, looking for all known compounds that share with acetone IR absorption in the spectral band selected for its detection. Possible interfering species were investigated, simulating both urban and industrial atmospheres and limits of acetone detection in both environments were identified. This study confirmed that a lidar/DIAL can detect low concentration of acetone at considerable distances.

  13. Lidar Calibration Centre

    NASA Astrophysics Data System (ADS)

    Pappalardo, Gelsomina; Freudenthaler, Volker; Nicolae, Doina; Mona, Lucia; Belegante, Livio; D'Amico, Giuseppe

    2016-06-01

    This paper presents the newly established Lidar Calibration Centre, a distributed infrastructure in Europe, whose goal is to offer services for complete characterization and calibration of lidars and ceilometers. Mobile reference lidars, laboratories for testing and characterization of optics and electronics, facilities for inspection and debugging of instruments, as well as for training in good practices are open to users from the scientific community, operational services and private sector. The Lidar Calibration Centre offers support for trans-national access through the EC HORIZON2020 project ACTRIS-2.

  14. Linear LIDAR versus Geiger-mode LIDAR: impact on data properties and data quality

    NASA Astrophysics Data System (ADS)

    Ullrich, A.; Pfennigbauer, M.

    2016-05-01

    LIDAR has become the inevitable technology to provide accurate 3D data fast and reliably even in adverse measurement situations and harsh environments. It provides highly accurate point clouds with a significant number of additional valuable attributes per point. LIDAR systems based on Geiger-mode avalanche photo diode arrays, also called single photon avalanche photo diode arrays, earlier employed for military applications, now seek to enter the commercial market of 3D data acquisition, advertising higher point acquisition speeds from longer ranges compared to conventional techniques. Publications pointing out the advantages of these new systems refer to the other category of LIDAR as "linear LIDAR", as the prime receiver element for detecting the laser echo pulses - avalanche photo diodes - are used in a linear mode of operation. We analyze the differences between the two LIDAR technologies and the fundamental differences in the data they provide. The limitations imposed by physics on both approaches to LIDAR are also addressed and advantages of linear LIDAR over the photon counting approach are discussed.

  15. Analysis of algebraic reconstruction technique for accurate imaging of gas temperature and concentration based on tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hui-Hui, Xia; Rui-Feng, Kan; Jian-Guo, Liu; Zhen-Yu, Xu; Ya-Bai, He

    2016-06-01

    An improved algebraic reconstruction technique (ART) combined with tunable diode laser absorption spectroscopy(TDLAS) is presented in this paper for determining two-dimensional (2D) distribution of H2O concentration and temperature in a simulated combustion flame. This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy. It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid, and after that point, the number of projection rays has little influence on reconstruction accuracy. It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method. In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed, and the capability of this new method is evaluated by using appropriate assessment parameters. By using this new approach, not only the concentration reconstruction accuracy is greatly improved, but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation. Finally, a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method. Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles. This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205151), the National Key Scientific Instrument and Equipment Development Project of China (Grant

  16. Analysis of algebraic reconstruction technique for accurate imaging of gas temperature and concentration based on tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Hui-Hui, Xia; Rui-Feng, Kan; Jian-Guo, Liu; Zhen-Yu, Xu; Ya-Bai, He

    2016-06-01

    An improved algebraic reconstruction technique (ART) combined with tunable diode laser absorption spectroscopy(TDLAS) is presented in this paper for determining two-dimensional (2D) distribution of H2O concentration and temperature in a simulated combustion flame. This work aims to simulate the reconstruction of spectroscopic measurements by a multi-view parallel-beam scanning geometry and analyze the effects of projection rays on reconstruction accuracy. It finally proves that reconstruction quality dramatically increases with the number of projection rays increasing until more than 180 for 20 × 20 grid, and after that point, the number of projection rays has little influence on reconstruction accuracy. It is clear that the temperature reconstruction results are more accurate than the water vapor concentration obtained by the traditional concentration calculation method. In the present study an innovative way to reduce the error of concentration reconstruction and improve the reconstruction quality greatly is also proposed, and the capability of this new method is evaluated by using appropriate assessment parameters. By using this new approach, not only the concentration reconstruction accuracy is greatly improved, but also a suitable parallel-beam arrangement is put forward for high reconstruction accuracy and simplicity of experimental validation. Finally, a bimodal structure of the combustion region is assumed to demonstrate the robustness and universality of the proposed method. Numerical investigation indicates that the proposed TDLAS tomographic algorithm is capable of detecting accurate temperature and concentration profiles. This feasible formula for reconstruction research is expected to resolve several key issues in practical combustion devices. Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No. 61205151), the National Key Scientific Instrument and Equipment Development Project of China (Grant

  17. Correcting for underlying absorption interferences in Fourier transform infrared trans analysis of edible oils using two-dimensional correlation techniques.

    PubMed

    van de Voort, F R; Sedman, J; Sherazi, S T H

    2008-03-12

    Substantive improvement in the sensitivity of the AOAC/AOCS spectral ratioing method for the determination of isolated trans isomers in edible oils was recently achieved by the application of a new spectral reconstitution (SR) technique that facilitates the FTIR analysis of edible oils in the transmission mode. However, the general applicability of the spectral ratioing method is still severely limited by the requirement to know the provenance of the oil to be analyzed and have on hand its trans-free counterpart so that the underlying triacylglycerol absorptions in the trans measurement region (990-945 cm(-1)), henceforth referred to as UAt , may be ratioed out. To eliminate the need for a trans-free reference oil, we have employed two-dimensional (2D) correlation spectroscopy to search for other spectral features that might correlate with and serve to estimate the UAt . The three-dimensional contour maps obtained by 2D correlation analysis of the spectra of 10 trans-free oils of different oil types, recorded using the SR procedure, revealed such correlations in two spectral regions, 1700-1600 and 4500-4300 cm(-1), exhibiting one maximum and two maxima, respectively, with wavenumber coordinates of (968, 4407), (968, 4299), and (968, 1650). The latter two correlations, when optimized, produced excellent linear regression relationships (r>0.95) with the UAt . The spectra of five sets of trielaidin-spiked oils were corrected for the UA t using these relationships, and their trans contents were predicted from the calibration equation generated for the spectral ratioing procedure. Linear regression of predicted versus added trans over the range of 0-1.6% trans, which is below the limit of quantitation of the AOAC/AOCS spectral ratioing method, yielded r=0.88-0.90 with an SD of approximately 0.2% trans. These results indicate that the combination of the SR technique with the UA t correction approach may provide a simple and accurate FTIR method for the analysis of the

  18. LIDAR, Point Clouds, and their Archaeological Applications

    SciTech Connect

    White, Devin A

    2013-01-01

    It is common in contemporary archaeological literature, in papers at archaeological conferences, and in grant proposals to see heritage professionals use the term LIDAR to refer to high spatial resolution digital elevation models and the technology used to produce them. The goal of this chapter is to break that association and introduce archaeologists to the world of point clouds, in which LIDAR is only one member of a larger family of techniques to obtain, visualize, and analyze three-dimensional measurements of archaeological features. After describing how point clouds are constructed, there is a brief discussion on the currently available software and analytical techniques designed to make sense of them.

  19. A tomographic technique for the simultaneous imaging of temperature, chemical species, and pressure in reactive flows using absorption spectroscopy with frequency-agile lasers

    SciTech Connect

    Cai, Weiwei; Kaminski, Clemens F.

    2014-01-20

    This paper proposes a technique that can simultaneously retrieve distributions of temperature, concentration of chemical species, and pressure based on broad bandwidth, frequency-agile tomographic absorption spectroscopy. The technique holds particular promise for the study of dynamic combusting flows. A proof-of-concept numerical demonstration is presented, using representative phantoms to model conditions typically prevailing in near-atmospheric or high pressure flames. The simulations reveal both the feasibility of the proposed technique and its robustness. Our calculations indicate precisions of ∼70 K at flame temperatures and ∼0.05 bars at high pressure from reconstructions featuring as much as 5% Gaussian noise in the projections.

  20. Lidar point density analysis: implications for identifying water bodies

    USGS Publications Warehouse

    Worstell, Bruce B.; Poppenga, Sandra; Evans, Gayla A.; Prince, Sandra

    2014-01-01

    Most airborne topographic light detection and ranging (lidar) systems operate within the near-infrared spectrum. Laser pulses from these systems frequently are absorbed by water and therefore do not generate reflected returns on water bodies in the resulting void regions within the lidar point cloud. Thus, an analysis of lidar voids has implications for identifying water bodies. Data analysis techniques to detect reduced lidar return densities were evaluated for test sites in Blackhawk County, Iowa, and Beltrami County, Minnesota, to delineate contiguous areas that have few or no lidar returns. Results from this study indicated a 5-meter radius moving window with fewer than 23 returns (28 percent of the moving window) was sufficient for delineating void regions. Techniques to provide elevation values for void regions to flatten water features and to force channel flow in the downstream direction also are presented.

  1. Excitonic emission and absorption resonances in V0.25W0.75Se2 single crystals grown by direct vapour transport technique

    NASA Astrophysics Data System (ADS)

    Solanki, G. K.; Pataniya, Pratik; Sumesh, C. K.; Patel, K. D.; Pathak, V. M.

    2016-05-01

    A systematic study on emission and absorption spectra of vanadium mixed tungsten diselenide single crystals grown by direct vapour transport (DVT) technique is reported. The grown crystals were characterized by energy dispersive analysis of X-ray (EDAX), which gives the confirmation about the stoichiometry. The structural characterizations were accomplished by X-ray diffraction (XRD), surface morphology and transmission electron microscopy (TEM). These characterizations were indicating the growth of V0.25W0.75Se2 single crystal from vapour phase. The optical response of this material has been observed by combination of UV-vis-NIR spectroscopy and photo luminescence (PL) spectroscopy. A detailed study of excitonic emission and absorption resonances was carried out on grown crystals. The energy band gap was calculated for indirect allowed transition with absorbed and emitted phonon. Additionally, absorption tail for grown crystal is found to obey the Urbach's rule.

  2. Atmospheric aerosol characterization combining multi-wavelength Raman lidar and MAX-DOAS measurements in Gwanjgu

    NASA Astrophysics Data System (ADS)

    Chong, Jihyo; Shin, Dong Ho; Kim, Kwang Chul; Lee, Kwon-Ho; Shin, Sungkyun; Noh, Young M.; Müller, Detlef; Kim, Young J.

    2011-11-01

    Integrated approach has been adopted at the ADvanced Environmental Research Center (ADEMRC), Gwangju Institute of Science and Technology (GIST), Korea for effective monitoring of atmospheric aerosol. Various active and passive optical remote sensing techniques such as multi-wavelength (3β+2α+1δ) Raman LIDAR, sun-photometry, MAX-DOAS, and satellite retrieval have been utilized. This integrated monitoring system approach combined with in-situ surface measurement is to allow better characterization of physical and optical properties of atmospheric aerosol. Information on the vertical distribution and microphysical properties of atmospheric aerosol is important for understanding its transport characteristics as well as radiative effect. The GIST multi-wavelength (3β + 2α+1δ) Raman lidar system can measure vertical profiles of optical properties of atmospheric aerosols such as extinction coefficients at 355 and 532nm, particle backscatter coefficients at 355, 532 and 1064 nm, and depolarization ratio at 532nm. The incomplete overlap between the telescope field-of-view and beam divergence of the transmitting laser significantly affects lidar measurement, resulting in higher uncertainty near the surface where atmospheric aerosols of interest are concentrated. Differential Optical Absorption Spectroscopy (DOAS) technique is applied as a complementary tool for the detection of atmospheric aerosols near the surface. The passive Multi-Axis DOAS (MAX-DOAS) technique uses scattered sunlight as a light source from several viewing directions. Recently developed aerosol retrieval algorithm based on O4 slant column densities (SCDs) measured at UV and visible wavelengths has been utilized to derive aerosol information (e.g., aerosol optical depth (AOD) and aerosol extinction coefficients (AECs)) in the lower troposphere. The aerosol extinction coefficient at 356 nm was retrieved for the 0-1 and 1-2 km layers based on the MAX-DOAS measurements using the retrieval algorithm

  3. Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer F.; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2015-01-01

    An airborne 2-micron double-pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. This new 2-miron pulsed IPDA lidar has been flown in spring of 2014 for total ten flights with 27 flight hours. It provides high precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the IPDA measurement.

  4. Airborne 2-Micron Double Pulsed Direct Detection IPDA Lidar for Atmospheric CO2 Measurement

    NASA Astrophysics Data System (ADS)

    Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Reithmaier, Karl; Remus, Ruben; Singh, Upendra; Johnson, Will; Boyer, Charlie; Fay, James; Johnston, Susan; Murchison, Luke

    2016-06-01

    An airborne 2-micron double-pulsed Integrated Path Differential Absorption (IPDA) lidar has been developed for atmospheric CO2 measurements. This new instrument has been flown in spring of 2014 for a total of ten flights with 27 flight hours. This IPDA lidar provides high precision measurement capability by unambiguously eliminating contamination from aerosols and clouds that can bias the results.

  5. Studying the local structures of novel materials using the Extended X-ray Absorption Fine Structure technique

    NASA Astrophysics Data System (ADS)

    Jiang, Yu

    2009-12-01

    In this dissertation, investigations on the local lattice structures for a variety of novel materials using Extended X-ray Absorption Fine Structure (EXAFS) technique are presented. Different experiment schemes were applied to obtain EXAFS data with high quality, and some interesting results were obtained by careful analysis. The power of the EXAFS technique was once again proved. In Chapter 1, I first briefly introduce the EXAFS theory and experiments, then give readers who are not familiar with this technique a short introduction on data reduction and analysis, and finally discuss some problems that are easily ignored in the interpretation of the experiment results. In Chapter 2, a temperature-dependent EXAFS investigation of La 1-xCaxMnO 3 is presented for the concentration range that spans the ferromagnetic-insulator (FMI) to ferromagnetic-metal (FMM) transition region, x = 0.16, 0.18, 0.20, and 0.22; the titrated hole concentrations are slightly higher y = 0.2, 0.22, 0.24, and 0.25 respectively. In Chapter 3, I report EXAFS studies of n- and p-type Ba8Ga 16Ge30 samples (type I clathrate) at the Ga, Ge, and Ba K-edges, to probe the local structure, particularly around the Ba atoms located inside 20- and 24-atom cages (Ba1 and Ba2 sites respectively) formed of Ga/Ge atoms. In agreement with diffraction analysis we find Ba2 is off-center, with a component in the bc plane (0.15 A) comparable to that found in diffraction; however, under the assumption of a stiff cage we also require a significant a component. This suggests a coupling or attraction between the Ba2 atoms and the hexagonal rings at the top or bottom of the cage that encloses the Ba2 site. In Chapter 4, I report detailed degradation and rejuvenation studies for AC electro-luminescence (EL) devices made using the phosphor ZnS:Cu,CI. We find that the AC EL emission spectra vary considerably with AC driving frequency but all spectra can be fit to a sum of four Gaussians. The combined experiments place

  6. Airborne and Ground-Based Measurements Using a High-Performance Raman Lidar

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Rush, Kurt; Rabenhorst, Scott; Welch, Wayne; Cadirola, Martin; McIntire, Gerry; Russo, Felicita; Adam, Mariana; Venable, Demetrius; Connell, Rasheen; Veselovskii, Igor; Forno, Ricardo; Mielke, Bernd; Stein, Bernhard; Leblanc, Thierry; McDermid, Stuart; Voemel, Holger

    2010-01-01

    -II measurements, along with numerical simulation, were used to determine that the likely reason for the suboptimal airborne aerosol extinction performance during theWAVES_2007 campaign was amisaligned interference filter. With full laser power and a properly tuned interference filter,RASL is shown to be capable ofmeasuring themain water vapor and aerosol parameters with temporal resolutions of between 2 and 45 s and spatial resolutions ranging from 30 to 330 m from a flight altitude of 8 km with precision of generally less than 10%, providing performance that is competitive with some airborne Differential Absorption Lidar (DIAL) water vapor and High Spectral Resolution Lidar (HSRL) aerosol instruments. The use of diode-pumped laser technology would improve the performance of an airborne Raman lidar and permit additional instrumentation to be carried on board a small research aircraft. The combined airborne and ground-based measurements presented here demonstrate a level of versatility in Raman lidar that may be impossible to duplicate with any other single lidar technique.

  7. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

    PubMed Central

    Limaye, Mukta V.; Chen, S. C.; Lee, C. Y.; Chen, L. Y.; Singh, Shashi B.; Shao, Y. C.; Wang, Y. F.; Hsieh, S. H.; Hsueh, H. C.; Chiou, J. W.; Chen, C. H.; Jang, L. Y.; Cheng, C. L.; Pong, W. F.; Hu, Y. F.

    2015-01-01

    The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2− (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2− species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2−, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples. PMID:26098075

  8. Optimizing Lidar Scanning Strategies for Wind Energy Measurements (Invited)

    NASA Astrophysics Data System (ADS)

    Newman, J. F.; Bonin, T. A.; Klein, P.; Wharton, S.; Chilson, P. B.

    2013-12-01

    Environmental concerns and rising fossil fuel prices have prompted rapid development in the renewable energy sector. Wind energy, in particular, has become increasingly popular in the United States. However, the intermittency of available wind energy makes it difficult to integrate wind energy into the power grid. Thus, the expansion and successful implementation of wind energy requires accurate wind resource assessments and wind power forecasts. The actual power produced by a turbine is affected by the wind speeds and turbulence levels experienced across the turbine rotor disk. Because of the range of measurement heights required for wind power estimation, remote sensing devices (e.g., lidar) are ideally suited for these purposes. However, the volume averaging inherent in remote sensing technology produces turbulence estimates that are different from those estimated by a sonic anemometer mounted on a standard meteorological tower. In addition, most lidars intended for wind energy purposes utilize a standard Doppler beam-swinging or Velocity-Azimuth Display technique to estimate the three-dimensional wind vector. These scanning strategies are ideal for measuring mean wind speeds but are likely inadequate for measuring turbulence. In order to examine the impact of different lidar scanning strategies on turbulence measurements, a WindCube lidar, a scanning Halo lidar, and a scanning Galion lidar were deployed at the Southern Great Plains Atmospheric Radiation Measurement (ARM) site in Summer 2013. Existing instrumentation at the ARM site, including a 60-m meteorological tower and an additional scanning Halo lidar, were used in conjunction with the deployed lidars to evaluate several user-defined scanning strategies. For part of the experiment, all three scanning lidars were pointed at approximately the same point in space and a tri-Doppler analysis was completed to calculate the three-dimensional wind vector every 1 second. In another part of the experiment, one of

  9. The Antarctic ozone lidar system

    NASA Astrophysics Data System (ADS)

    Stefanutti, L.; Castagnoli, F.; del Guasta, M.; Morandi, M.; Sacco, V. M.; Zuccagnoli, L.; Godin, S.; Megie, G.; Porteneuve, J.

    1992-07-01

    A new complex lidar system, designated POLE, for measuring tropospheric and stratospheric ozone, stratospheric aerosols, and polar stratospheric and tropospheric clouds is described. The lidar system is comprised of a Rayleigh lidar, an upper stratospheric ozone lidar, a low-altitude or tropospheric ozone lidar, and an aerosol backscattering depolarization lidar. The paper describes the characteristics of these lidars and the measurements obtained by each of them, together with the features of various subsystems of POLE, and presents results of measurements performed during the 1991 antarctic winter.

  10. A lidar system for measuring atmospheric pressure and temperature profiles

    NASA Technical Reports Server (NTRS)

    Schwemmer, Geary K.; Dombrowski, Mark; Korb, C. Laurence; Milrod, Jeffry; Walden, Harvey

    1987-01-01

    The design and operation of a differential absorption lidar system capable of remotely measuring the vertical structure of tropospheric pressure and temperature are described. The measurements are based on the absorption by atmospheric oxygen of the spectrally narrowband output of two pulsed alexandrite lasers. Detailed laser output spectral characteristics, which are critical to successful lidar measurements, are presented. Spectral linewidths of 0.026 and 0.018 per cm for the lasers were measured with over 99.99 percent of the energy contained in three longitudinal modes.

  11. Comparison of IPDA lidar receiver sensitivity for coherent detection and for direct detection using sine-wave and pulsed modulation.

    PubMed

    Sun, Xiaoli; Abshire, James B

    2012-09-10

    We use theoretical models to compare the receiver signal to noise ratio (SNR) vs. average rate of detected signal photons for an integrated path differential absorption (IPDA) lidar using coherent detection with continuous wave (CW) lasers and direct detection with sine-wave and pulse modulations. The results show the coherent IPDA lidar has high receiver gain and narrow bandwidth to overcome the effects of detector circuit noise and background light, but the actual receiver performance can be limited by the coherent mixing efficiency, speckle and other factors. For direct detection, using sine-wave modulation allows the use of a low peak power laser transmitter and synchronous detection. The pulse modulation technique requires higher laser peak powers but is more efficient than sine-wave modulation in terms of average detected signal photon rate required to achieve a given receiver SNR. We also conducted experiments for the direct detection cases and the results agreed well with theory.

  12. Aerosol characterization with lidar methods

    NASA Astrophysics Data System (ADS)

    Sugimoto, Nobuo; Nishizawa, Tomoaki; Shimizu, Atsushi; Matsui, Ichiro

    2014-08-01

    Aerosol component analysis methods for characterizing aerosols were developed for various types of lidars including polarization-sensitive Mie scattering lidars, multi-wavelength Raman scattering lidars, and multi-wavelength highspectral- resolution lidars. From the multi-parameter lidar data, the extinction coefficients for four aerosol components can be derived. The microphysical parameters such as single scattering albedo and effective radius can be also estimated from the derived aerosol component distributions.

  13. Double-Pulsed 2-Micrometer Lidar Validation for Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.; Refaat, Tamer F.; Yu, Jirong; Petros, Mulugeta; Remus, Ruben

    2015-01-01

    A double-pulsed, 2-micron Integrated Path Differential Absorption (IPDA) lidar instrument for atmospheric carbon dioxide (CO2) measurements is successfully developed at NASA Langley Research Center (LaRC). Based on direct detection technique, the instrument can be operated on ground or onboard a small aircraft. Key features of this compact, rugged and reliable IPDA lidar includes high transmitted laser energy, wavelength tuning, switching and locking, and sensitive detection. As a proof of concept, the IPDA ground and airborne CO2 measurement and validation will be presented. IPDA lidar CO2 measurements ground validation were conducted at NASA LaRC using hard targets and a calibrated in-situ sensor. Airborne validation, conducted onboard the NASA B-200 aircraft, included CO2 plum detection from power stations incinerators, comparison to in-flight CO2 in-situ sensor and comparison to air sampling at different altitude conducted by NOAA at the same site. Airborne measurements, spanning for 20 hours, were obtained from different target conditions. Ground targets included soil, vegetation, sand, snow and ocean. In addition, cloud slicing was examined over the ocean. These flight validations were conducted at different altitudes, up to 7 km, with different wavelength controlled weighing functions. CO2 measurement results agree with modeling conducted through the different sensors, as will be discussed.

  14. An adaptive lidar

    NASA Astrophysics Data System (ADS)

    Oshlakov, V. G.; Andreev, M. I.; Malykh, D. D.

    2009-09-01

    Using the polarization characteristics of a target and its underlying surface one can change the target contrast range. As the target one can use the compact and discrete structures with different characteristics to reflect electromagnetic waves. An important problem, solved by the adaptive polarization lidar, is to determine the availability and identification of different targets based on their polarization characteristics against the background of underlying surface, which polarization characteristics are unknown. Another important problem of the adaptive polarization lidar is a search for the objects, which polarization characteristics are unknown, against the background of underlying surface, which polarization characteristics are known. The adaptive polarization lidar makes it possible to determine the presence of impurities in sea water. The characteristics of the adaptive polarization lidar undergo variations, i.e., polarization characteristics of a sensing signal and polarization characteristics of the receiver are varied depending on the problem to be solved. One of the versions of construction of the adaptive polarization lidar is considered. The increase of the contrast in the adaptive lidar has been demonstrated by the numerical experiment when sensing hydrosols on the background of the Rayleigh scattering, caused by clear water. The numerical experiment has also demonstrated the increase of the contrast in the adaptive lidar when sensing at two wavelengths of dry haze and dense haze on the background of the Rayleigh scattering, caused by the clear atmosphere. The most effective wavelength was chosen.

  15. Recording of absorption spectra by a three-beam integral technique with a tunable laser and external cavity

    SciTech Connect

    Korolenko, P V; Nikolaev, I V; Ochkin, V N; Tskhai, S N

    2014-04-28

    An integral method is considered for recording absorption using three laser beams transmitted through and reflected from an external cavity with the absorbing medium (R-ICOS). The method is the elaboration of a known single-beam ICOS method and allows suppression of the influence of radiation phase fluctuations in the resonator on recording weak absorption spectra. First of all, this reduces high-frequency instabilities and gives a possibility to record spectra during short time intervals. In this method, mirrors of the resonator may have moderate reflection coefficients. Capabilities of the method have been demonstrated by the examples of weak absorption spectra of atmospheric methane and natural gas in a spectral range around 1650 nm. With the mirrors having the reflection coefficients of 0.8–0.99, a spectrum can be recorded for 320 μs with the accuracy sufficient for detecting a background concentration of methane in atmosphere. For the acquisition time of 20 s, the absorption coefficients of ∼2×10{sup -8} cm{sup -1} can be measured, which corresponds to a 40 times less molecule concentration than the background value. (laser spectroscopy)

  16. Masked-backlighter technique used to simultaneously image x-ray absorption and x-ray emission from an inertial confinement fusion plasma

    SciTech Connect

    Marshall, F. J. Radha, P. B.

    2014-11-15

    A method to simultaneously image both the absorption and the self-emission of an imploding inertial confinement fusion plasma has been demonstrated on the OMEGA Laser System. The technique involves the use of a high-Z backlighter, half of which is covered with a low-Z material, and a high-speed x-ray framing camera aligned to capture images backlit by this masked backlighter. Two strips of the four-strip framing camera record images backlit by the high-Z portion of the backlighter, while the other two strips record images aligned with the low-Z portion of the backlighter. The emission from the low-Z material is effectively eliminated by a high-Z filter positioned in front of the framing camera, limiting the detected backlighter emission to that of the principal emission line of the high-Z material. As a result, half of the images are of self-emission from the plasma and the other half are of self-emission plus the backlighter. The advantage of this technique is that the self-emission simultaneous with backlighter absorption is independently measured from a nearby direction. The absorption occurs only in the high-Z backlit frames and is either spatially separated from the emission or the self-emission is suppressed by filtering, or by using a backlighter much brighter than the self-emission, or by subtraction. The masked-backlighter technique has been used on the OMEGA Laser System to simultaneously measure the emission profiles and the absorption profiles of polar-driven implosions.

  17. Raman lidar/AERI PBL Height Product

    DOE Data Explorer

    Ferrare, Richard

    2012-12-14

    Planetary Boundary Layer (PBL) heights have been computed using potential temperature profiles derived from Raman lidar and AERI measurements. Raman lidar measurements of the rotational Raman scattering from nitrogen and oxygen are used to derive vertical profiles of potential temperature. AERI measurements of downwelling radiance are used in a physical retrieval approach (Smith et al. 1999, Feltz et al. 1998) to derive profiles of temperature and water vapor. The Raman lidar and AERI potential temperature profiles are merged to create a single potential temperature profile for computing PBL heights. PBL heights were derived from these merged potential temperature profiles using a modified Heffter (1980) technique that was tailored to the SGP site (Della Monache et al., 2004). PBL heights were computed on an hourly basis for the period January 1, 2009 through December 31, 2011. These heights are provided as meters above ground level.

  18. Langley Mobile Ozone Lidar (LMOL) results from the Denver, CO DISCOVER-AQ campaign

    NASA Astrophysics Data System (ADS)

    De Young, Russell; Carrion, William; Pliutau, Denis; Ganoe, Rene

    2015-10-01

    The Langley Mobile Ozone Lidar (LMOL) is a compact mobile differential absorption lidar (DIAL) system that was developed at NASA Langley Research Center, Hampton, VA, USA to provide ozone, aerosol and cloud atmospheric measurements in a mobile trailer for ground-based atmospheric air quality campaigns. This lidar is part of the Tropospheric Ozone Lidar Network (TOLNet) currently made up of six other ozone lidars across the U.S and Canada. This lidar has been deployed to Denver, CO July 15-August 15, 2014 for the DISCOVER-AQ air quality campaign. Ozone and aerosol profiles were taken showing the influence of emissions from the Denver region. Results of ozone concentration, aerosol scattering ratio, boundary layer height and clouds will be presented with emphasis on regional air quality.

  19. Phoenix Lidar Operation Animation

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] Click on image for animation

    This is an animation of the Canadian-built meteorological station's lidar, which was successfully activated on Sol 2. The animation shows how the lidar is activated by first opening its dust cover, then emitting rapid pulses of light (resembling a brilliant green laser) into the Martian atmosphere. Some of the light then bounces off particles in the atmosphere, and is reflected back down to the lidar's telescope. This allows the lidar to detect dust, clouds and fog.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  20. Aerosol lidar ``M4``

    SciTech Connect

    Shelevoy, C.D.; Andreev, Y.M. |

    1994-12-31

    Small carrying aerosol lidar in which is used small copper vapor laser ``Malachite`` as source of sounding optical pulses is described. The advantages of metal vapor laser and photon counting mode in acquisition system of lidar gave ability to get record results: when lidar has dimensions (1 x .6 x .3 m) and weight (65 kg), it provides the sounding of air industrial pollutions at up to 20 km range in scanning sector 90{degree}. Power feed is less than 800 Wt. Lidar can be disposed as stationary so on the car, helicopter, light plane. Results of location of smoke tails and city smog in situ experiments are cited. Showed advantages of work of acquisition system in photon counting mode when dynamic range of a signal is up to six orders.

  1. Software system for simulation IPDA lidar sensing from space platform

    NASA Astrophysics Data System (ADS)

    Matvienko, G. G.; Sukhanov, A. Ya.

    2014-11-01

    High measurement sensitivity of troposphere CO2 and CH4 is expected from using of integrated path differential absorption (IPDA) lidar, where the strong lidar echoes on two wavelengths from cloud tops or the Earth's take place. We consider a software system for the radiation transport simulation in the atmosphere by Monte-Carlo method that applied in the greenhouse gas (CH4 and CO2) sensing space-based IPDA-lidar. This software is used to evaluate the accuracy of measurement of the green house gas concentration. The paper investigates the impact of multiple scattering in presence of clouds. So multiple scattering can influence on signal power, but differential absorption method eliminates this drawback.

  2. Application of the Z-scan technique to determine the optical Kerr coefficient and two-photon absorption coefficient of magnetite nanoparticles colloidal suspension

    NASA Astrophysics Data System (ADS)

    Vivacqua, Marco; Espinosa, Daniel; Martins Figueiredo Neto, Antônio

    2012-06-01

    We investigate the occurrence of the optical Kerr effect and two-photon absorption when an oil-based magnetic Fe3O4 nanoparticles colloidal suspension is illuminated with high intensity femtosecond laser pulses. The frequency of the pulses is controlled and the Z-scan technique is employed in our measurements of the nonlinear optical Kerr coefficient (n2) and two-photon absorption coefficient (β). From these values it was possible to calculate the real and imaginary parts of the third-order susceptibility. We observed that increasing the pulse frequency, additional physical processes take place, increasing artificially the absolute values of n2 and β. The experimental conditions are discussed to assure the obtention of reliable values of these nonlinear optical parameters, which may be useful in all-optical switching and optical power limiting applications.

  3. Characterization of the Spatial Distributions and Optical Properties of Smoke Using Lidar Observations during SEAC4RS

    NASA Astrophysics Data System (ADS)

    Hair, J. W.; Ferrare, R. A.; Butler, C. F.; Fenn, M. A.; Burton, S. P.; Scarino, A. J.; Notari, A.; Collins, J. E., Jr.; Nehrir, A. R.; Ismail, S.; Hu, Y.; Hostetler, C. A.

    2014-12-01

    The NASA Langley Research Center airborne combined Differential Absorption Lidar - High Spectral Resolution Lidar (DIAL/HSRL) characterized ozone and aerosol distributions while deployed on the NASA DC-8 during the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) airborne field campaign. In addition to measuring ozone concentrations throughout the troposphere and lower stratosphere, this advanced lidar system simultaneously measures aerosol extinction and aerosol optical thickness (AOT) at 532 nm via the HSRL technique, as well as aerosol backscatter and depolarization at 355, 532, and 1064 nm in both nadir and zenith directions. The DIAL/HSRL measurements of lidar ratio (i.e., the ratio of extinction and backscatter), aerosol depolarization ratio, backscatter color ratio, and spectral depolarization ratio (i.e., the ratio of aerosol depolarization at the two wavelengths) provide information about the aerosol physical properties and so are combined to infer aerosol type. Aerosol extinction and optical thickness are apportioned to these aerosol types. Smoke from biomass burning is identified by the lidar data and the optical parameters along with the vertical and horizontal distributions are presented from the SEAC4RS campaigns. Mixed Layer (ML) heights, which are often good proxies for daytime Planetary Boundary Layer (PBL) heights, are derived along the aircraft track by locating strong gradients in the aerosol backscatter profiles. The DIAL/HSRL measurements are used to determine the fraction of AOT due to smoke within and above the ML. In addition, the DIAL/HSRL measurements from the research flight on August 6, 2013 are used to quantify and characterize smoke above uniform stratus clouds.

  4. The Durban atmospheric LIDAR

    NASA Astrophysics Data System (ADS)

    Moorgawa, A.; Bencherif, H.; Michaelis, M. M.; Porteneuve, J.; Malinga, S.

    2007-03-01

    A brief description of the Durban atmospheric LIDAR (acronym for light detection and ranging) system for the measurement of vertical temperature profiles is presented. In its original configuration, a 10 Hz-laser was used as the transmitter for the LIDAR. The 10 Hz-laser has now been replaced by a 30 Hz-laser delivering five times more power. Both lasers have been used separately to sample the atmosphere above Durban. A comparative analysis of the backscattered signals obtained separately from each laser shows that the 30 Hz-laser has a much greater stratospheric range. The wavelength emitted for both lasers is 532 nm. A comparison of the average monthly LIDAR temperature profiles has been computed between 20 and 60 km. The LIDAR temperature profiles have been compared with the South African Weather Service (SAWS) radiosonde temperature measurement for the lower stratosphere, between 20 and 27 km. The agreement between the two measurements is good in the lower stratosphere where SAWS radiosondes overlap with LIDAR. A comparison of the LIDAR and SAGE II (stratospheric aerosol and gas experiment) aerosol measurements has also been carried out.

  5. Lidar Technology at the Goddard Laser and Electro-Optics Branch

    NASA Technical Reports Server (NTRS)

    Heaps, William S.; Obenschain, Arthur F. (Technical Monitor)

    2000-01-01

    Discovery-class orbiters now in the NASA planetary program. The purpose of the lidar is to continuously profile the water vapor and dust in the Mars atmosphere from orbit in order to quantify its dynamics, their relationship in the diurnal cycles, and to infer water vapor exchange with the Mars surface. To remotely measure the water-vapor height profiles, we will use the differential absorption lidar (DIAL) technique. We are also developing a laser sensor for measuring the total column content of CO2 in the atmosphere of the earth. CO2 is the principal greenhouse gas and has increased by roughly 80 ppm in the last century and a half. We will report our efforts in the development of the laser transmitter and photon counting detector components for a Mars Orbiting DIAL system and for the CO2 sounder.

  6. Optical systems modeling and experimental realization of pump and probe technique: investigation of nonlinear absorption in colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Smirnov, A.; Golinskaya, A.; Ezhova, K.; Kozlova, M.; Dneprovskii, V.

    2016-04-01

    Two optical systems modeling of laser and broadband radiation focusing, that is necessary for realization of the pump and probe method, was carried out in this work. Modeling was utilized to construct experimental setup for transmission spectra measuring of studied sample by probe nanosecond broadband radiation (coumarin photoluminescence) depending on the intensity of the nanosecond laser pump pulses. The saturation effect of absorption and the induced charge Stark-effect coexistence and predominate issue of these effects are determined by power of optical excitation. In dependence of tuning of excitation radiation frequency from basic exciton transition frequency nonlinear effects in colloidal CdSe/ZnS quantum dots has been investigated.

  7. Characterization of a 16-Bit Digitizer for Lidar Data Acquisition

    NASA Technical Reports Server (NTRS)

    Williamson, Cynthia K.; DeYoung, Russell J.

    2000-01-01

    A 6-MHz 16-bit waveform digitizer was evaluated for use in atmospheric differential absorption lidar (DIAL) measurements of ozone. The digitizer noise characteristics were evaluated, and actual ozone DIAL atmospheric returns were digitized. This digitizer could replace computer-automated measurement and control (CAMAC)-based commercial digitizers and improve voltage accuracy.

  8. Gas in scattering media absorption spectroscopy - GASMAS

    NASA Astrophysics Data System (ADS)

    Svanberg, Sune

    2008-09-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS).

  9. The Zugspitze Raman Lidar: System Testing

    NASA Astrophysics Data System (ADS)

    Höveler, Katharina; Klanner, Lisa; Trickl, Thomas; Vogelmann, Hannes

    2016-06-01

    A high-power Raman lidar system has been installed at the high-altitude research station Schneefernerhaus (Garmisch-Partenkirchen, Germany) at 2675 m a.s.l., at the side of the existing wide-range differrential-absorption lidar. An industrial XeCl laser was modified for polarized single-line operation at an average power of about 175 W. This high power and a 1.5-m-diameter receiver are expected to allow us to extend the operating range for water-vapour sounding to more than 25 km, at an accuracy level of the order of 10 %. In addition, temperature measurements in the free troposphere and to altitudes beyond 80 km are planned. The system is currently thoroughly tested and exhibits an excellent performance up to the lowermost stratosphere. We expect that results for higher altitudes can be presented at the meeting.

  10. Alexandrite laser source for atmospheric lidar measurements

    NASA Technical Reports Server (NTRS)

    Pelon, J.; Loth, C.; Flamant, P.; Megie, G.

    1986-01-01

    During the past years, there has been a marked increase in interest in the applications of vibronic solid state lasers to meteorology and atmospheric physics. Two airborne lidar programs are now under development in France. The differential absorption lidar (DIAL) method with vibronic solid state lasers is very attractive for water vapor, temperature and pressure measurements. Alexandrite laser and titanium-sapphire are both suitable for these applications. However, only alexandrite rods are commercially available. The requirements on the laser source for airborne dial applications are two fold: (1) a restriction on laser linewidth and a requirement on stability and tunability with a good spectral purity; and (2) a requirement on the time separation between the two pulses. These constraints are summarized.

  11. Pulsed Lidar for Measurement of C02 Concentrations for the ASCENDS Mission - Update

    NASA Technical Reports Server (NTRS)

    Abshire, James; Riris, Haris; Allan, Graham; Sun, Xiaoli; Mao, Jianping; Weaver, Clark; Yu, Anthony; Chen, Jeffrey; Rodriquez, Michael; Kawa, S. Randy

    2011-01-01

    We have been developing a laser-based sounding technique for the remote measurement of the tropospheric CO2 concentrations from orbit for NASA is ASCENDS mission. The mission's goals are to provide measurements of tropospheric CO2 abundance with global-coverage, a few hundred km spatial and monthly temporal resolution. These are needed to better understand CO2 fluxes and the processes that regulate CO2 storage by the land and oceans. For the lIP, we are developing and demonstrating the lidar techniques and key lidar technology that will permit measurements of the CO2 column abundance in the lower troposphere from aircraft. Our final goal is to demonstrate the key capabilities needed for a space lidar and mission approach for the ASCENDS mission. We use a pulsed lidar technique, which is much less sensitive to errors from cloud and atmospheric scattering and to noise from solar background. It allows continuous measurements of CO2 mixing ratio in the lower troposphere during day and night. Our approach uses the 1570nm CO2 band and a two-wavelength laser absorption spectrometer, which continuously measures at nadir from a circular polar orbit. It directs the narrow co-aligned laser beams from the instrument's lasers toward nadir, and measures the energy of the laser echoes reflected from land and water surfaces. It uses a pair of tunable laser transmitters, which allowing measurement of the extinction from a single selected CO2 absorption line in the 1570 nm band and from a line pair in the Oxygen A-band near 765 nm. These regions have temperature insensitive absorption lines are free from interference from other gases. The lasers pulse at 10KHz, use tunable diode seed lasers followed by laser amplifiers, and have MHz spectral widths. During the measurement the lasers are stepped across the selected lines at a kHz rate. The receiver uses a 1-m class telescope and photon sensitive detectors and measures the background light and energies of the laser echoes from the

  12. Propylation technique for the simultaneous determination of tetraalkyllead and ionic alkyllead species by gas chromatography/atomic absorption spectrometry

    SciTech Connect

    Radojevic, M.; Allen, A.; Rapsomanikis, S.; Harrison, R.M.

    1986-03-01

    The only technique capable of simultaneous determination of R/sub 4/Pb and ionic alkyllead compounds involves extraction into an organic solvent in the presence of sodium diethyldithiocarbamate (NaDDTC) and derivatizations of ionic species to R/sub 4/Pb forms using a butylating Grignard reagent (n-butylmagnesium chloride) followed by GC/AAS analysis. This technique has been applied to many environmental samples with some degree of success, although for many less polluted samples even greater sensitivity is required. In this communication the authors present an improved and novel derivatization technique of the simultaneous determination R/sub 4/Pb and ionic alkyllead species involving extraction into n-hexane and propylation to the tetraalkyllead form using propylmagnesium chloride with GC/electrothermal AAS analysis. The technique is compared to the previously reported butylation method, and procedures of extract concentration are investigated. 11 references, 2 figures, 1 table.

  13. Laser Energy Monitor for Double-Pulsed 2-Micrometer IPDA Lidar Application

    NASA Technical Reports Server (NTRS)

    Refaat, Tamer F.; Petros, Mulugeta; Remus, Ruben; Yu, Jirong; Singh, Upendra N.

    2014-01-01

    Integrated path differential absorption (IPDA) lidar is a remote sensing technique for monitoring different atmospheric species. The technique relies on wavelength differentiation between strong and weak absorbing features normalized to the transmitted energy. 2-micron double-pulsed IPDA lidar is best suited for atmospheric carbon dioxide measurements. In such case, the transmitter produces two successive laser pulses separated by short interval (200 microseconds), with low repetition rate (10Hz). Conventional laser energy monitors, based on thermal detectors, are suitable for low repetition rate single pulse lasers. Due to the short pulse interval in double-pulsed lasers, thermal energy monitors underestimate the total transmitted energy. This leads to measurement biases and errors in double-pulsed IPDA technique. The design and calibration of a 2-micron double-pulse laser energy monitor is presented. The design is based on a high-speed, extended range InGaAs pin quantum detectors suitable for separating the two pulse events. Pulse integration is applied for converting the detected pulse power into energy. Results are compared to a photo-electro-magnetic (PEM) detector for impulse response verification. Calibration included comparing the three detection technologies in single-pulsed mode, then comparing the pin and PEM detectors in double-pulsed mode. Energy monitor linearity will be addressed.

  14. Energy Measurement Studies for CO2 Measurement with a Coherent Doppler Lidar System

    NASA Technical Reports Server (NTRS)

    Beyon, Jeffrey Y.; Koch, Grady J.; Vanvalkenburg, Randal L.; Yu, Jirong; Singh, Upendra N.; Kavaya, Michael J.

    2010-01-01

    The accurate measurement of energy in the application of lidar system for CO2 measurement is critical. Different techniques of energy estimation in the online and offline pulses are investigated for post processing of lidar returns. The cornerstone of the techniques is the accurate estimation of the spectrum of lidar signal and background noise. Since the background noise is not the ideal white Gaussian noise, simple average level estimation of noise level is not well fit in the energy estimation of lidar signal and noise. A brief review of the methods is presented in this paper.

  15. Application of a diode-laser absorption technique with the d(2) transition of atomic rb for hypersonic flow-field measurements.

    PubMed

    Trinks, O; Beck, W H

    1998-10-20

    With a first application of semiconductor lasers to absorption measurements of seeded atomic Rb in high-enthalpy flow fields, a diagnostic technique for time-resolved determination of flow velocity and gas temperature with a line-shape analysis was developed. In our measurements a GaAlAs diode laser was used to scan repetitively at 15 kHz over 1.3 cm(-1) across the D(2) resonance transition (5S(1/2) ? 5P(3/2), 780.2 nm) of seeded atomic Rb to obtain multiple absorption line shapes. The time-dependent signal contains highly resolved spectral line-shape information, which we interpret by fitting the spectrally resolved line shapes to Voigt profiles. Kinetic temperatures in the range 900-1400 K and gas velocities in the range 3900-6200 ms(-1) were obtained from the Doppler-broadened component of the line shape and from the Doppler shift, respectively, of the absorption frequency.

  16. Effect of speckle on lidar pulse-pair ratio statistics.

    PubMed

    Mackerrow, E P; Schmitt, M J; Thompson, D C

    1997-11-20

    The ratio of temporally adjacent lidar pulse returns is commonly used in differential absorption lidar (DIAL) to reduce correlated noise. These pulses typically are generated at different wavelengths with the assumption that the dominant noise is common to both. This is not the case when the mean number of laser speckle integrated per pulse by the lidar receiver is small (namely, less than 10 speckles at each wavelength). In this case a large increase in the standard deviation of the ratio data results. We demonstrate this effect both theoretically and experimentally. The theoretical value for the expected standard deviation of the pulse-pair ratio data compares well with the measured values that used a dual CO(2) laser-based lidar with a hard target. Pulse averaging statistics of the pulse-pair data obey the expected varsigma(1)/ radicalN reduction in the standard deviation, varsigma(N), for N-pulse averages. We consider the ratio before average, average before ratio, and log of the ratio before average methods for noise reduction in the lidar equation. The implications of our results are discussed in the context of dual-laser versus single-laser lidar configurations.

  17. Standoff Stack Emissions Monitoring Using Short Range Lidar

    NASA Astrophysics Data System (ADS)

    Gravel, Jean-Francois Y.; Babin, Francois; Allard, Martin

    2016-06-01

    There are well documented methods for stack emissions monitoring. These are all based on stack sampling through sampling ports in well defined conditions. Once sampled, the molecules are quantified in instruments that often use optical techniques. Unfortunately sampling ports are not found on all stacks/ducts or the use of the sampling ports cannot be planned efficiently because of operational constraints or the emissions monitoring equipment cannot be driven to a remote stack/duct. Emissions monitoring using many of the same optical techniques, but at a standoff distance, through the atmosphere, using short range high spatial resolution lidar techniques was thus attempted. Standoff absorption and Raman will be discussed and results from a field campaign will be presented along with short descriptions of the apparatus. In the first phase of these tests, the molecules that were targeted were NO and O2. Spatially resolved optical measurements allow for standoff identification and quantification of molecules, much like the standardized methods, except for the fact that it is not done in the stack, but in the plume formed by the emissions from the stack. The pros and cons will also be discussed, and in particular the problem of mass emission estimates that require the knowledge of the flow rate and the distribution of molecular concentration in the plane of measurement.

  18. Development of a Scheimpflug Lidar System for Atmospheric Aerosol Monitoring

    NASA Astrophysics Data System (ADS)

    Mei, Liang; Brydegaard, Mikkel

    2016-06-01

    This work presents a Scheimpflug lidar system which was employed for atmospheric aerosol monitoring in southern Sweden. Atmospheric aerosol fluctuation was observed around rush-hour. The extinction coefficient over 6 km was retrieved, i.e., 0.15 km-1, by employing the slop-method during the time when the atmosphere was relatively homogenous. The measurements successfully demonstrate the potential of using a Scheimpflug lidar technique for atmospheric aerosol monitoring applications.

  19. Raman lidar for the remote measurement of subsurface ocean parameters

    NASA Technical Reports Server (NTRS)

    Leonard, D. A.; Caputo, B.

    1984-01-01

    The Raman lidar technique was developed for the remote measurement of temperature and salinity profiles. A temperature accuracy of 0.5 degrees Centigrade is attainable in a practical field system for depths of up to 3 diffuse attentuation lengths, which can be 100 meters or more in the open ocean. In this paper field test results are reviewed and performance specifications for typical Raman lidar systems are presented.

  20. Lidar Tracking of Multiple Fluorescent Tracers: Method and Field Test

    NASA Technical Reports Server (NTRS)

    Eberhard, Wynn L.; Willis, Ron J.

    1992-01-01

    Past research and applications have demonstrated the advantages and usefulness of lidar detection of a single fluorescent tracer to track air motions. Earlier researchers performed an analytical study that showed good potential for lidar discrimination and tracking of two or three different fluorescent tracers at the same time. The present paper summarizes the multiple fluorescent tracer method, discusses its expected advantages and problems, and describes our field test of this new technique.

  1. Lidar Altitude Data Read Routine

    Atmospheric Science Data Center

    2013-03-19

      Lidar Altitude Data Read Routine This routine demonstrates reading the lidar altitude data stored in CALIPSO Lidar Level 1B Profile, Level 2 Aerosol ... Data Language (IDL) and uses HDF routine calls to read the altitude data which are stored in an HDF vdata (table) structure, as described ...

  2. NASA Airborne Lidar July 1991

    Atmospheric Science Data Center

    2016-05-26

    NASA Airborne Lidar July 1991 Data from the 1991 NASA Langley Airborne Lidar flights following the eruption of Pinatubo in July ... and Osborn [1992a, 1992b]. Project Title:  NASA Airborne Lidar Discipline:  Field Campaigns ...

  3. NASA Airborne Lidar May 1992

    Atmospheric Science Data Center

    2016-05-26

    NASA Airborne Lidar May 1992 An airborne Nd:YAG (532 nm) lidar was operated by the NASA Langley Research Center about a year following the June 1991 eruption of ... Osborn [1992a, 1992b].  Project Title:  NASA Airborne Lidar Discipline:  Field Campaigns ...

  4. Lidar Observation of Ozone Profiles in the Equatorial Tropopause Region

    NASA Astrophysics Data System (ADS)

    Abo, M.; Shibata, Y.; Nagasawa, C.

    2014-12-01

    Tropospheric ozone in the tropics zone is significant in terms of the oxidizing efficiency and greenhouse effect. However, in the upper troposphere, the ozone budget in the tropics has not been fully understood yet because of the sparsity of the range-resolved observations of vertical ozone concentration profiles. We have constructed the lidar facility for survey of atmospheric structure over troposphere, stratosphere, mesosphere and low thermosphere over Kototabang (100.3E, 0.2S), Indonesia in the equatorial region. The lidar system consists of the Mie and Raman lidars for tropospheric aerosol, water vapor and cirrus cloud measurements, the Rayleigh lidar for stratospheric and mesospheric temperature measurements and the Resonance lidar for metallic species such as Na, Fe, Ca ion measurements and temperature measurements in the mesopause region. The lidar observations started from 2004, and routine observations of clouds and aerosol in the troposphere and stratosphere are continued now. We have installed DIAL (differential absorption lidar) system for high-resolution measurements of vertical ozone profiles in the equatorial tropopause region over Kototabang. There were many ozone DIAL systems in the world, but their systems are almost optimized for stratospheric ozone layer measurement or tropospheric ozone measurement. Because of deep ozone absorption in the UV region, the wavelength selection is important. Over the equatorial region, the tropopause height is almost 17km. So we use 305nm for on-line and 355nm for off-line using second harmonics of dye laser and third harmonics of Nd:YAG laser. We have observed large ozone enhancement in the upper troposphere, altitude of 13-17km in June 2014, concurring with a zonal wind oscillation associated with the equatorial Kelvin wave around the tropopause[1] at equatorial region. References Fujiwara, M. et al., JGR, 103, D15, 19,173-19,182, 1998.

  5. Continuously-tunable, narrow-linewidth, Q-switched Cr:LiSAF laser for lidar applications

    SciTech Connect

    Early, J.W.; Lester, C.S.; Quick, C.R.; Tiee, J.J.; Shimada, T.; Cockroft, N.J.

    1995-02-01

    A continuously-tunable, narrow-linewidth, flashlamp-pumped, Q-switched Cr:LiSAF laser has been developed (energy: 30 mJ, pulsewidth: 40 ns, linewidth:<2 GHz) and was used successfully for the DIAL(differential absorption lidar) measurements of atmospheric water vapor and LIF lidar for the remote detection of metal oxide fluorescence.

  6. A lidar system for remote sensing of aerosols and water vapor from NSTS and Space Station Freedom

    NASA Technical Reports Server (NTRS)

    Delorme, Joseph F.

    1989-01-01

    The Tropical Atmospheric Lidar Observing System (TALOS) is proposed to be developed as a Differential Absorption Lidar (DIAL) system for flight aboard the earth orbiting Space Station Freedom. TALOS will be capable of making high resolution vertical profile measurements of tropospheric water and tropospheric and stratospheric aerosols, clouds and temperature.

  7. Lidar performance analysis

    NASA Technical Reports Server (NTRS)

    Spiers, Gary D.

    1994-01-01

    Section 1 details the theory used to build the lidar model, provides results of using the model to evaluate AEOLUS design instrument designs, and provides snapshots of the visual appearance of the coded model. Appendix A contains a Fortran program to calculate various forms of the refractive index structure function. This program was used to determine the refractive index structure function used in the main lidar simulation code. Appendix B contains a memo on the optimization of the lidar telescope geometry for a line-scan geometry. Appendix C contains the code for the main lidar simulation and brief instruction on running the code. Appendix D contains a Fortran code to calculate the maximum permissible exposure for the eye from the ANSI Z136.1-1992 eye safety standards. Appendix E contains a paper on the eye safety analysis of a space-based coherent lidar presented at the 7th Coherent Laser Radar Applications and Technology Conference, Paris, France, 19-23 July 1993.

  8. Description and evaluation of a tropospheric ozone lidar implemented on an existing lidar in the southern subtropics.

    PubMed

    Baray, J L; Leveau, J; Porteneuve, J; Ancellet, G; Keckhut, P; Posny, F; Baldy, S

    1999-11-20

    Rayleigh-Mie lidar measurements of stratospheric temperature and aerosol profiles have been carried out at Reunion Island (southern tropics) since 1993. Since June 1998, an operational extension of the system is permitting additional measurements of tropospheric ozone to be made by differential absorption lidar. The emission wavelengths (289 and 316 nm) are obtained by stimulated Raman shifting of the fourth harmonic of a Nd:YAG laser in a high-pressure deuterium cell. A mosaic of four parabolic mirrors collects the backscattered signal, and the transmission is processed by the multiple fiber collector method. The altitude range of ozone profiles obtained with this system is 3¿17 km. Technical details of this lidar system working in the southern tropics, comparisons of ozone lidar profiles with radiosondes, and scientific perspectives are presented. The significant lack of tropospheric ozone measurements in the tropical and equatorial regions, the particular scientific interest in these regions, and the altitude range of the ozone measurements to 16¿17 km make this lidar supplement useful and its adaptation technically conceivable at many Rayleigh-Mie lidar stations.

  9. An Improved Computational Technique for Calculating Electromagnetic Forces and Power Absorptions Generated in Spherical and Deformed Body in Levitation Melting Devices

    NASA Technical Reports Server (NTRS)

    Zong, Jin-Ho; Szekely, Julian; Schwartz, Elliot

    1992-01-01

    An improved computational technique for calculating the electromagnetic force field, the power absorption and the deformation of an electromagnetically levitated metal sample is described. The technique is based on the volume integral method, but represents a substantial refinement; the coordinate transformation employed allows the efficient treatment of a broad class of rotationally symmetrical bodies. Computed results are presented to represent the behavior of levitation melted metal samples in a multi-coil, multi-frequency levitation unit to be used in microgravity experiments. The theoretical predictions are compared with both analytical solutions and with the results or previous computational efforts for the spherical samples and the agreement has been very good. The treatment of problems involving deformed surfaces and actually predicting the deformed shape of the specimens breaks new ground and should be the major usefulness of the proposed method.

  10. An improved computational technique for calculating electromagnetic forces and power absorptions generated in spherical and deformed body in levitation melting devices

    NASA Technical Reports Server (NTRS)

    Zong, Jin-Ho; Szekely, Julian; Schwartz, Elliot

    1992-01-01

    An improved computational technique for calculating the electromagnetic force field, the power absorption and the deformation of an electromagnetically levitated metal sample is described. The technique is based on the volume integral method, but represents a substantial refinement; the coordinate transformation employed allows the efficient treatment of a broad class of rotationally symmetrical bodies. Computed results are presented to represent the behavior of levitation melted metal samples in a multi-coil, multi-frequency levitation unit to be used in microgravity experiments. The theoretical predictions are compared with both analytical solutions and with the results of previous computational efforts for the spherical samples and the agreement has been very good. The treatment of problems involving deformed surfaces and actually predicting the deformed shape of the specimens breaks new ground and should be the major usefulness of the proposed method.

  11. Noise estimation technique to reduce the effects of 1/f noise in Open Path Tunable Diode Laser Absorption Spectrometry (OP-TDLAS)

    NASA Astrophysics Data System (ADS)

    Mohammad, Israa L.; Anderson, Gary T.; Chen, Youhua

    2014-06-01

    Many techniques using high frequency modulation have been proposed to reduce the effects of 1/f noise in tunable diode-laser absorption spectroscopy (TDLAS). The instruments and devices used by these techniques are not suitable for space applications that require small, low mass and low power instrumentation. A new noise estimation technique has already been proposed and validated for two lasers to reduce the effect of 1/f noise at lower frequencies. This paper extends the noise estimation technique and applies it using one distribution feedback (DFB) laser diode. In this method a DFB laser diode is excited at two slightly different frequencies, giving two different harmonics that can be used to estimate the total noise in the measurement. Simulations and experimental results on ammonia gas validate that the 1/f noise is effectively reduced by the noise estimation technique using one laser. Outdoor experimental results indicate that the effect of 1/f noise is reduced to more than 1/4 its normal value.

  12. Derivation of Sky-View Factors from LIDAR Data

    NASA Technical Reports Server (NTRS)

    Kidd, Christopher; Chapman, Lee

    2013-01-01

    The use of Lidar (Light Detection and Ranging), an active light-emitting instrument, is becoming increasingly common for a range of potential applications. Its ability to provide fine resolution spatial and vertical resolution elevation data makes it ideal for a wide range of studies. This paper demonstrates the capability of Lidar data to measure sky view factors (SVF). The Lidar data is used to generate a spatial map of SVFs which are then compared against photographically-derived SVF at selected point locations. At each location three near-surface elevations measurements were taken and compared with collocated Lidar-derived estimated. It was found that there was generally good agreement between the two methodologies, although with decreasing SVF the Lidar-derived technique tended to overestimate the SVF: this can be attributed in part to the spatial resolution of the Lidar sampling. Nevertheless, airborne Lidar systems can map sky view factors over a large area easily, improving the utility of such data in atmospheric and meteorological models.

  13. Potential of the isolated lung technique for the examination of sildenafil absorption from lung-delivered poly(lactide-co-glycolide) microparticles.

    PubMed

    Beck-Broichsitter, Moritz; Stoisiek, Katharina; Bohr, Adam; Aragão-Santiago, Leticia; Gessler, Tobias; Seeger, Werner; Kissel, Thomas

    2016-03-28

    Herein, we challenged the isolated lung (IL) technique to discriminate the performance of lung-delivered polymeric microparticles (MPs) having distinct drug release rates. For this purpose, sildenafil-loaded poly(lactide-co-glycolide) MPs were administered to the airspace of an IL model and the drug absorption profile was monitored. MPs (particle size of ~5μm) composed of PLGA of lower molecular weight (and glass transition temperature) manifested in the most rapid in vitro drug release (half-times ranging from <15 to ~200min). Moreover, microencapsulation resulted in a delayed sildenafil transfer over the air/perfusate barrier (half-times ranging from <5 to ~230min), where the actual ex vivo absorption profile depended on the release behavior of the utilized formulation. Finally, the obtained in vitro and ex vivo results were tested for level C, B and A correlations. The plotted data showed good agreement (R(2)>0.96) and the slopes of the resulting lines of regression (i.e., 0.80-0.85) indicated a slightly elevated in vitro drug release behavior. Overall, the IL model was able to differentiate between distinct microparticulate formulations and is, therefore, a valuable technique for early testing of potential inhalable controlled release medications.

  14. Speciation of water soluble iron in size segregated airborne particulate matter using LED based liquid waveguide with a novel dispersive absorption spectroscopic measurement technique.

    PubMed

    Chan, K L; Jiang, S Y N; Ning, Z

    2016-03-31

    In this study, we present the development and evaluation of a dispersive absorption spectroscopic technique for trace level soluble ferrous detection. The technique makes use of the broadband absorption spectra of the ferrous-ferrozine complex with a novel spectral fitting algorithm to determine soluble ferrous concentrations in samples and achieves much improved measurement precision compared to conventional methods. The developed method was evaluated by both model simulations and experimental investigations. The results demonstrated the robustness of the method against the spectral fluctuation, wavelength drift and electronic noise, while achieving excellent linearity (R(2) > 0.999) and low detection limit (0.06 μg L(-1)) for soluble ferrous detection. The developed method was also used for the speciation of soluble iron in size segregated atmospheric aerosols. The measurement was carried out during Spring and Summer in typical urban environment in Hong Kong. The measured total iron concentrations are in good agreement compared to conventional Inductively Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) measurements. Investigation on ambient particulate matter samples shows the size dependent characteristic of iron speciation in the atmosphere with a more active role of fine particles in transforming between ferrous and ferric. The method demonstrated in this study provides a cost and time effective approach for the speciation of iron in ambient aerosols. PMID:26965332

  15. Determination of Two-Photon Absorption Cross-Section of Noble Gases for Calibration of Laser Spectroscopic Techniques

    SciTech Connect

    Rosa, M. I. de la; Perez, C.; Gruetzmacher, K.; Fuentes, L. M.

    2008-10-22

    The objective of our work is to apply two-photon polarization spectroscopy as a new calibration method for the determination of two-photon excitation cross-sections of noble gases, like Xe and Kr, which are commonly used for calibrations of MP-LIF techniques in other laboratories.

  16. Micro pulse lidar

    SciTech Connect

    Spinhirne, J.D. )

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering has been demonstrated. The transmitter of the micro pulse lidar is a diode pumped [mu]J pulse energy, high repetition rate Nd:YLF laser. Eye safety is obtained through beam expansion. The receiver employs a photon counting solid state Geiger mode avalanche photodiode detector. Data acquisition is by a single card multichannel scaler. Daytime background induced quantum noise is controlled by a narrow receiver field-of-view (FOV) and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited by optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that systems built on the micro pulse lidar concept are capable of detecting and profiling all significant cloud and aerosol scattering through the troposphere and into the stratosphere. The intended applications are scientific studies and environmental monitoring which require full time, unattended measurements of the cloud and aerosol height structure.

  17. Airborne cw Doppler lidar (ADOLAR)

    NASA Astrophysics Data System (ADS)

    Rahm, Stefan; Werner, Christian; Nagel, E.; Herrmann, H.; Klier, M.; Knott, H. P.; Haering, R.; Wildgruber, J.

    1994-12-01

    During the last 10 years the DLR container LDA (Laser Doppler Anemometer) was used for many wind related measurements in the atmospheric boundary layer. The experience out of this were used to construct an airborne Doppler lidar ADOLAR. Based on the available Doppler lidars it is now proposed to perform a campaign to demonstrate the concept of the spaceborne sensor ALADIN, and to answer some questions concerning the signal quality from clouds, water and land. For the continuous wave CO2 laser, the energy is focused by the telescope into the region of investigation. Some of the radiation is back scattered by small aerosol particles drifting with the wind speed through the sensing volume. The back scattered radiation is collected by the telescope and detected by coherent technique. With the laser Doppler method one gets the radial wind component. To determine the magnitude and direction of the horizontal wind, some form of scanning in azimuth and elevation is required. To keep the airborne system compact, the transceiver optics is directly coupled to a wedge scanner which provides the conical scan with the axis in Nadir direction from the aircraft. The system ADOLAR was tested in 1994. Results of the flight over the lake Ammersee are presented and are compared with the data of the inertial reference system of the aircraft.

  18. Selection of an averaging technique by simulation study of a DIAL system for toxic agents monitoring

    NASA Astrophysics Data System (ADS)

    Dudeja, Jai Paul; Jindal, Mukesh Kumar; Veerabuthiran, S.

    2007-10-01

    Differential Absorption Lidar (DIAL) is a very effective technique for standoff detection of various toxic agents in the atmosphere. The Lidar backscattered signal received usually has poor signal to noise (SNR) ratio. In order to improve the SNR, statistical averaging over a number of laser pulses is employed. The aim of the present work is to select a particular statistical averaging technique, which is most suitable in removing the noise in Lidar return signals. The DIAL system considered here uses laser transmitters based on OPO based (2-5 μm) and TEA CO2 (9-11μm) lasers. Eight commonly used chemical warfare agents including five nerve agents and three blister agents have been considered here as examples of toxic agents. A Graphical User Interface (GUI) software has been developed in LabVIEW to simulate return signals mixed with the expected noise levels. A toxic agent cloud with a given thickness and concentration has been assumed to be detected in the ambient atmospheric conditions at various ranges up to 5 Km. Data for 200 pulses per agent was stored in the computer memory. Various known statistical averaging techniques were used and number concentrations of particular agent have been computed and compared with ideal Lidar return signal values. This exercise was repeated for all the eight agents and based on the results obtained; the most suitable averaging technique has been selected.

  19. A two-laser beam technique for improving the sensitivity of low frequency open path tunable diode laser absorption spectrometer (OP-TDLAS) measurements

    NASA Astrophysics Data System (ADS)

    Mohammad, Israa L.; Anderson, Gary T.; Chen, Youhua

    2013-09-01

    Open path tunable diode-laser absorption spectroscopy (OP-TDLAS) is a promising technique to detect low concentrations of possible biogenic gases on Mars. This technique finds the concentration of a gas by measuring the amount of laser light absorbed by gaseous molecules at a specific wavelength. One of the major factors limiting sensitivity in the TDLAS systems operating at low modulation frequencies is 1/f noise. 1/f noise is minimized in many spectroscopy systems by the use of high frequency modulation techniques. However, these techniques require complex instruments that include reference cells and other devices for calibration, making them relatively large and bulky. We are developing a spectroscopy system for space applications that requires small, low mass and low power instrumentation, making the high frequency techniques unsuitable. This paper explores a new technique using two-laser beam to reduce the affect of 1/f noise and increase the signal strength for measurements made at lower frequencies. The two lasers are excited at slightly different frequencies. An algorithm is used to estimate the noise in the second harmonic from the combined spectra of both lasers. This noise is subtracted from the signal to give a more accurate measurement of gas concentration. The error in estimation of 1/f noise is negligible as it corresponds to noise level made at much higher frequencies. Simulation results using ammonia gas and two lasers operating at 500 and 510 Hz respectively shows that this technique is able to decrease the error in estimation of gas concentration to 1/6 its normal value.

  20. Diode laser based water vapor DIAL using modulated pulse technique

    NASA Astrophysics Data System (ADS)

    Pham, Phong Le Hoai; Abo, Makoto

    2014-11-01

    In this paper, we propose a diode laser based differential absorption lidar (DIAL) for measuring lower-tropospheric water vapor profile using the modulated pulse technique. The transmitter is based on single-mode diode laser and tapered semiconductor optical amplifier with a peak power of 10W around 800nm absorption band, and the receiver telescope diameter is 35cm. The selected wavelengths are compared to referenced wavelengths in terms of random error and systematic errors. The key component of modulated pulse technique, a macropulse, is generated with a repetition rate of 10 kHz, and the modulation within the macropulse is coded according to a pseudorandom sequence with 100ns chip width. As a result, we evaluate both single pulse modulation and pseudorandom coded pulse modulation technique. The water vapor profiles conducted from these modulation techniques are compared to the real observation data in summer in Japan.