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Sample records for international laser radar

  1. Sixteenth International Laser Radar Conference, part 2

    NASA Technical Reports Server (NTRS)

    Mccormick, M. Patrick (Editor)

    1992-01-01

    Given here are extended abstracts of papers presented at the 16th International Laser Radar Conference, held in Cambridge, Massachusetts, July 20-24, 1992. Topics discussed include the Mt. Pinatubo volcanic dust laser observations, global change, ozone measurements, Earth mesospheric measurements, wind measurements, imaging, ranging, water vapor measurements, and laser devices and technology.

  2. Nineteenth International Laser Radar Conference. Part 1

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N. (Editor); Ismail, Syed (Editor); Schwemmer, Geary K. (Editor)

    1998-01-01

    This publication contains extended abstracts of papers presented at the Nineteenth International Laser Radar Conference, held at Annapolis, Maryland, July 6-10, 1998; 260 papers were presented in both oral and poster sessions. The topics of the conference sessions were Aerosol Clouds, Multiple Scattering; Tropospheric Profiling; Stratospheric/Mesospheric Profiling; Wind Profiling; New Lidar Technology and Techniques; Lidar Applications, including Altimetry and Marine; Space and Future Lidar; and Lidar Commercialization/Eye Safety. This conference reflects the breadth of research activities being conducted in the lidar field. These abstracts address subjects from lidar-based atmospheric investigations, development of new lasers and lidar system technology, and current and future space-based lidar systems.

  3. Nineteenth International Laser Radar Conference. Part 2

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N. (Editor); Ismail, Syed (Editor); Schwemmer, Geary K. (Editor)

    1998-01-01

    This publication contains extended abstracts of papers presented at the Nineteenth International Laser Radar Conference, held at Annapolis, Maryland, July 6-10, 1998; 260 papers were presented in both oral and poster sessions. The topics of the conference sessions were Aerosol Clouds, Multiple Scattering; Tropospheric Profiling, Stratospheric/Mesospheric Profiling; Wind Profiling; New Lidar Technology and Techniques; Lidar Applications, Including Altimetry and Marine; Space and Future Lidar; and Lidar Commercialization/Eye Safety. This conference reflects the breadth of research activities being conducted in the lidar field. These abstracts address subjects from lidar-based atmospheric investigations, development of new lasers and lidar system technology, and current and future space-based lidar systems.

  4. Sixteenth International Laser Radar Conference, Part 1

    NASA Technical Reports Server (NTRS)

    Mccormick, M. Patrick (Editor)

    1992-01-01

    This publication contains extended abstracts of papers presented at the 16th International Laser Radar Conference. One-hundred ninety-five papers were presented in both oral and poster sessions. The topics of the conference sessions were: (1) Mt. Pinatubo Volcanic Dust Layer Observations; (2) Global Change/Ozone Measurements; (3) GLOBE/LAWS/LITE; (4) Mesospheric Measurements and Measurement Systems; (5) Middle Atmosphere; (6) Wind Measurements and Measurement Systems; (7) Imaging and Ranging; (8) Water Vapor Measurements; (9) Systems and Facilities; and (10) Laser Devices and Technology. This conference reflects the breadth of research activities being conducted in the lidar field. These abstracts address subjects from lidar-based atmospheric investigations relating to global change to the development of new lidar systems and technology.

  5. Laser radar in robotics

    SciTech Connect

    Carmer, D.C.; Peterson, L.M.

    1996-02-01

    In this paper the authors describe the basic operating principles of laser radar sensors and the typical algorithms used to process laser radar imagery for robotic applications. The authors review 12 laser radar sensors to illustrate the variety of systems that have been applied to robotic applications wherein information extracted from the laser radar data is used to automatically control a mechanism or process. Next, they describe selected robotic applications in seven areas: autonomous vehicle navigation, walking machine foot placement, automated service vehicles, manufacturing and inspection, automotive, military, and agriculture. They conclude with a discussion of the status of laser radar technology and suggest trends seen in the application of laser radar sensors to robotics. Many new applications are expected as the maturity level progresses and system costs are reduced.

  6. Laser Radar Animation

    NASA Image and Video Library

    Laser and radar instruments aboard NASA aircraft provide measurements of the snow and ice surface and down to the bedrock under the ice. Lasers, with a shorter wavelength, measure the surface eleva...

  7. Spaceborne laser radar.

    NASA Technical Reports Server (NTRS)

    Flom, T.

    1972-01-01

    Development of laser systems to acquire and track targets in applications such as the rendezvous and docking of two spacecraft. A scan technique is described whereby a narrow laser beam is simultaneously scanned with an equally narrow receiver field-of-view without the aid of mechanical gimbals. Equations are developed in order to examine the maximum acquisition and tracking rates, and the maximum target range for a scanning laser radar system. A recently built prototype of a small, lightweight, low-power-consuming scanning laser radar is described.

  8. Numerical simulation of imaging laser radar system

    NASA Astrophysics Data System (ADS)

    Han, Shaokun; Lu, Bo; Jiang, Ming; Liu, Xunliang

    2008-03-01

    Rational and effective design of imaging laser radar systems is the key of imaging laser radar system research. Design must fully consider the interrelationship between various parameters. According to the parameters, choose suitable laser, detector and other components. To use of mathematical modeling and computer simulation is an effective imaging laser radar system design methods. This paper based on the distance equation, using the detection statistical methods, from the laser radar range coverage, detection probability, false-alarm rate, SNR to build the laser radar system mathematical models. In the process of setting up the mathematical models to fully consider the laser, atmosphere, detector and other factors on the performance that is to make the models be able to respond accurately the real situation. Based on this using C# and Matlab designed a simulation software.

  9. Underwater probing with laser radar

    NASA Technical Reports Server (NTRS)

    Carswell, A. I.; Sizgoric, S.

    1975-01-01

    Recent advances in laser and electro optics technology have greatly enhanced the feasibility of active optical probing techniques aimed at the remote sensing of water parameters. This paper describes a LIDAR (laser radar) that has been designed and constructed for underwater probing. The influence of the optical properties of water on the general design parameters of a LIDAR system is considered. Discussion of the specific details in the choice of the constructed LIDAR is given. This system utilizes a cavity dumped argon ion laser transmitter capable of 50 watt peak powers, 10 nanosecond pulses and megahertz pulse repetition rates at 10 different wavelengths in the blue green region of the spectrum. The performance of the system, in proving various types of water, is demonstrated by summarizing the results of initial laboratory and field experiments.

  10. Micro pulse laser radar

    NASA Technical Reports Server (NTRS)

    Spinhirne, James D. (Inventor)

    1993-01-01

    An eye safe, compact, solid state lidar for profiling atmospheric cloud and aerosol scattering is disclosed. The transmitter of the micro pulse lidar is a diode pumped micro-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 and a narrow bandwidth temperature controlled interference filter. Dynamic range of the signal is limited to optical geometric signal compression. Signal simulations and initial atmospheric measurements indicate that micropulse lider systems 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.

  11. Range imaging laser radar

    DOEpatents

    Scott, M.W.

    1990-06-19

    A laser source is operated continuously and modulated periodically (typically sinusoidally). A receiver imposes another periodic modulation on the received optical signal, the modulated signal being detected by an array of detectors of the integrating type. Range to the target determined by measuring the phase shift of the intensity modulation on the received optical beam relative to a reference. The receiver comprises a photoemitter for converting the reflected, periodically modulated, return beam to an accordingly modulated electron stream. The electron stream is modulated by a local demodulation signal source and subsequently converted back to a photon stream by a detector. A charge coupled device (CCD) array then averages and samples the photon stream to provide an electrical signal in accordance with the photon stream. 2 figs.

  12. Range imaging laser radar

    DOEpatents

    Scott, Marion W.

    1990-01-01

    A laser source is operated continuously and modulated periodically (typicy sinusoidally). A receiver imposes another periodic modulation on the received optical signal, the modulated signal being detected by an array of detectors of the integrating type. Range to the target determined by measuring the phase shift of the intensity modulation on the received optical beam relative to a reference. The receiver comprises a photoemitter for converting the reflected, periodically modulated, return beam to an accordingly modulated electron stream. The electron stream is modulated by a local demodulation signal source and subsequently converted back to a photon stream by a detector. A charge coupled device (CCD) array then averages and samples the photon stream to provide an electrical signal in accordance with the photon stream.

  13. Progress in coherent laser radar

    NASA Technical Reports Server (NTRS)

    Vaughan, J. M.

    1986-01-01

    Considerable progress with coherent laser radar has been made over the last few years, most notably perhaps in the available range of high performance devices and components and the confidence with which systems may now be taken into the field for prolonged periods of operation. Some of this increasing maturity was evident at the 3rd Topical Meeting on Coherent Laser Radar: Technology and Applications. Topics included in discussions were: mesoscale wind fields, nocturnal valley drainage and clear air down bursts; airborne Doppler lidar studies and comparison of ground and airborne wind measurement; wind measurement over the sea for comparison with satellite borne microwave sensors; transport of wake vortices at airfield; coherent DIAL methods; a newly assembled Nd-YAG coherent lidar system; backscatter profiles in the atmosphere and wavelength dependence over the 9 to 11 micrometer region; beam propagation; rock and soil classification with an airborne 4-laser system; technology of a global wind profiling system; target calibration; ranging and imaging with coherent pulsed and CW system; signal fluctuations and speckle. Some of these activities are briefly reviewed.

  14. Remote sensing with laser spectrum radar

    NASA Astrophysics Data System (ADS)

    Wang, Tianhe; Zhou, Tao; Jia, Xiaodong

    2016-10-01

    The unmanned airborne (UAV) laser spectrum radar has played a leading role in remote sensing because the transmitter and the receiver are together at laser spectrum radar. The advantages of the integrated transceiver laser spectrum radar is that it can be used in the oil and gas pipeline leak detection patrol line which needs the non-contact reflective detection. The UAV laser spectrum radar can patrol the line and specially detect the swept the area are now in no man's land because most of the oil and gas pipelines are in no man's land. It can save labor costs compared to the manned aircraft and ensure the safety of the pilots. The UAV laser spectrum radar can be also applied in the post disaster relief which detects the gas composition before the firefighters entering the scene of the rescue.

  15. Polarimetric laser radar target classification.

    PubMed

    Chun, Cornell S L; Sadjadi, Firooz A

    2005-07-15

    Imaging laser radar (ladar) systems have been developed for automatic target identification in surveillance systems. Ladar uses the range value at the target pixels to estimate the target's 3-D shape and identify the target. For targets in clutter and partially hidden targets, there are ambiguities in determining which pixels are on target that lead to uncertainties in determining the target's 3-D shape. An improvement is to use the polarization components of the reflected light. We describe the operation and preliminary evaluation of a polarization diverse imaging ladar system. Using a combination of intensity, range, and degree of polarization, we are better able to identify and distinguish the target from other objects of the same class.

  16. Remote Minefield Detection Using Infrared Laser Radar

    DTIC Science & Technology

    1988-11-01

    Technology of Coherent Infrared Radar, pp. 60, 1981. 22. R.M. Hardesty , T.R. Lawrence, R.A. Richter, et al., "Ground- Based Coherent Lidar Measurement...vegetation damage related to their deployment. High- resolution imaging RMD lidar systems can use this information as a further aid to minefield...example a CO2 laser- based system can be called a ladar, a lidar , an optical radar, or an infrared radar. The most commonly used expressions are lidar and

  17. Simulation of laser radar imagery

    NASA Astrophysics Data System (ADS)

    Sheffer, Albert D., Jr.; Thompson, Fred L.

    1986-01-01

    Software has been developed for the simulation of laser radar range imagery. Two versions have been developed: the first is an idealized model which is noise-free and with zero dropout rate; the second includes both pointing and range noise effects and provides for calculation of probability of detection for each pixel, with dropout occurring for probabilities below threshold, and also allows for user control over a number of other parameters such as scanning convention (unidirectional vs bidirectional), scan efficiency, and trajectory update rates. Each version allows for motion of a LADAR sensor across a terrain database on which faceted objects (targets and clutter) have been placed. For each pixel the program calculates the laser exit beam direction, based upon the combined effects of the sensor sweep pattern and the motion and attitude of the sensor platform. The exit beam is traced for intersection with the terrain or an object. Program output consists of the x, y, z-coordinates of the intersection point and the (real-number) range to that point for each pixel. This output can then be converted to a displayable range image. The software is currently implemented on a VAX 11/750 computer operating under VMS.

  18. Noise sources in laser radar systems.

    PubMed

    Letalick, D; Renhorn, I; Steinvall, O; Shapiro, J H

    1989-07-01

    To understand the fundamental limit of performance with a given laser radar system, the phase noise of a testbed laser radar has been investigated. Apart from the phase noise in the transmitter laser and the local oscillator laser, additional phase noise was introduced by vibrations caused by fans in power supplies and cooling systems. The stability of the mechanical structure of the platform was also found to be of great importance. Furthermore, a model for the signal variations from diffuse targets has been developed. This model takes into account the stray light, the speckle decorrelation, and Doppler shift due to moving targets.

  19. Laser radar for spacecraft guidance applications

    NASA Technical Reports Server (NTRS)

    Liebe, C. C.; Abramovici, A.; Bartman, R. K.; Bunker, R. L.; Chapsky, J.; Chu, C. C.; Clouse, D.; Dillon, J. W.; Hausmann, B.; Hemmati, H.; hide

    2003-01-01

    A flight qualified laser radar called LAMP (LAser MaPper) is under development at JPL. LAMP is a guidance and control sensor that can form 3 dimensional images of its field of regard. This paper describes the detailed design of the LAMP sensor.

  20. MST radar observation in international programs

    NASA Astrophysics Data System (ADS)

    Kato, Susumu

    1993-08-01

    MST radars played an important role in the observation of middle atmosphere dynamics in MAP. The radars have made it possible, for the first time, to observe the precise behaviour of atmospheric gravity waves which had so far been suspected, without definite observations, to contribute to produce weak winds around the mesopause. The facilities then built in various places as in the U.S.A., Germany and Japan detected some crucial behaviors to prove the existence of gravity waves breaking in these heights, showing a release of the momentum as required for producing the weak wind region. Since MAP through MAC to STEP which is now going, MST radars have been increasingly active, with increase of the facilities over the globe, in the observation of atmospheric dynamics from near the ground up to the mesosphere. Besides winds, gravity waves and turbulence, the facilities are now found to be able to observe precise structures of various meteorological disturbances as weather-fronts, typhoon, etc. Even the gap without echoes so far between the middle stratosphere and the lower mesosphere would disappear with an appearance of very powerful facilities in future. Like MST radars, ST radars are well developed. They are also pulsed-doppler radars working on VHF radio waves as MST radars, but less sensitive as to be able to observe only the lower stratosphere and the troposphere. ST radars are economical and widely used for unattended observation and in setting-up networks in international programs. ST radars work as meteor radars simply by installing a small device, Medac, to the original systems. Medium frequency (MF) radars suit mesosphere and lower thermosphere observation; they operate with fairly low power, suitable for continuous observation.

  1. The laser radar above 30 kilometers

    NASA Technical Reports Server (NTRS)

    Clemesha, B. R.

    1969-01-01

    A short "state of the art' report on laser radar observations of the atmosphere at heights greater than 30 km is presented. Graphs of recent measurements of the Rayleigh backscattering function between 30 and 70 and above 50 kilometers are included.

  2. In-bore chronograph--a laser radar for interior ballistics measurements, part 1: system design

    NASA Astrophysics Data System (ADS)

    Lawson, Greg; Fowler, Stuart R.; Halsey, Howard W.; Whittle, Kerry B.; Kamerman, Gary W.

    1993-10-01

    An internal research and development program at Teledyne Brown Engineering has produced a laser radar device to measure velocities of projectiles as they travel through the barrel of a gun. The technique measures velocities directly via the Doppler shift imposed on a retro- reflected laser beam. The device, called the In-Bore Chronograph (IBC), is believed to be the first coherent laser radar to be offered commercially. The IBC measures in-bore velocities from 5 to 2500 m/sec.

  3. Counter-sniper 3D laser radar

    NASA Astrophysics Data System (ADS)

    Shepherd, Orr; LePage, Andrew J.; Wijntjes, Geert J.; Zehnpfennig, Theodore F.; Sackos, John T.; Nellums, Robert O.

    1999-01-01

    Visidyne, Inc., teaming with Sandia National Laboratories, has developed the preliminary design for an innovative scannerless 3-D laser radar capable of acquiring, tracking, and determining the coordinates of small caliber projectiles in flight with sufficient precision, so their origin can be established by back projecting their tracks to their source. The design takes advantage of the relatively large effective cross-section of a bullet at optical wavelengths. Kay to its implementation is the use of efficient, high- power laser diode arrays for illuminators and an imaging laser receiver using a unique CCD imager design, that acquires the information to establish x, y (angle-angle) and range coordinates for each bullet at very high frame rates. The detection process achieves a high degree of discrimination by using the optical signature of the bullet, solar background mitigation, and track detection. Field measurements and computer simulations have been used to provide the basis for a preliminary design of a robust bullet tracker, the Counter Sniper 3-D Laser Radar. Experimental data showing 3-D test imagery acquired by a lidar with architecture similar to that of the proposed Counter Sniper 3-D Lidar are presented. A proposed Phase II development would yield an innovative, compact, and highly efficient bullet-tracking laser radar. Such a device would meet the needs of not only the military, but also federal, state, and local law enforcement organizations.

  4. Three-dimensional laser radar modeling

    NASA Astrophysics Data System (ADS)

    Steinvall, Ove K.; Carlsson, Tomas

    2001-09-01

    Laser radars have the unique capability to give intensity and full 3-D images of an object. Doppler lidars can give velocity and vibration characteristics of an objects. These systems have many civilian and military applications such as terrain modelling, depth sounding, object detection and classification as well as object positioning. In order to derive the signal waveform from the object one has to account for the laser pulse time characteristics, media effects such as the atmospheric attenuation and turbulence effects or scattering properties, the target shape and reflection (BRDF), speckle noise together with the receiver and background noise. Finally the type of waveform processing (peak detection, leading edge etc.) is needed to model the sensor output to be compared with observations. We have developed a computer model which models performance of a 3-D laser radar. We will give examples of signal waveforms generated from model different targets calculated by integrating the laser beam profile in space and time over the target including reflection characteristics during different speckle and turbulence conditions. The result will be of help when designing and using new laser radar systems. The importance of different type of signal processing of the waveform in order to fulfil performance goals will be shown.

  5. Coherent Laser Radar Remote Sensing

    DTIC Science & Technology

    1983-09-30

    and at a distance L m in front of the radar. The target will either be a spatially unresolved on-axis glint object ot radar cross-section d m2 , or a...17) A-6 and (after some manipulation) (SU 2 dy expi-’,uLy/4) 2 1 Jl(-y)l 2 Chet 2[1 - 2 2l expý~wLy)1] where JI is a Bessel function, ad a 4aL/ D , (19...or L, and UT a UL * I. (Because aT = aL, (46) and (47) yield Chet - chetg/2.) Whereas the spatial resolution was not severely affected by the choice

  6. Integrated laser/radar satellite ranging and tracking system

    NASA Technical Reports Server (NTRS)

    Hoge, F. E.

    1974-01-01

    A laser satellite ranging system that is mounted upon and integrated with a microwave tracking radar is reported. The 1-pulse/sec ruby laser transmitter is attached directly to the radar's elevation axis and radiates through a new opening in the radar's parabolic dish. The laser photomultiplier tube receiver utilizes the radar's existing 20-cm diam f/11 boresight telescope and observes through a similar symmetrically located opening in the dish. The laser system possesses separate ranging system electronics but shares the radar's timing, computer, and data handling/recording systems. The basic concept of the laser/radar is outlined together with a listing of the numerous advantages over present singular laser range-finding systems. The developmental laser hardware is described along with preliminary range-finding results and expectations.

  7. Coherent laser radar: Current European systems

    NASA Technical Reports Server (NTRS)

    Vaughan, J. Michael

    1985-01-01

    Coherent laser radar systems at 10 micrometers have been studied in Europe for well over a decade. In the past few years, the level of activity has increased rapidly and work is now in progress on systems and components at a large number of research institutions and industrial firms. Some of the organizations have had specific involvement with wind and aerosol measuring lidars, while others are largely concerned with components. Some of the particular European strong points are reviewed in device physics and technology. In addition to wind measurement systems, much work has been done on other applications of coherent laser radar including ranging, imaging, and coherent DIAL studies. Some of these other applications are also outlined.

  8. Laser radar monitoring of tropospheric aerosols

    NASA Astrophysics Data System (ADS)

    Devara, P. C. S.; Raj, P. Ernest; Londhe, A. L.

    1989-04-01

    A bistatic laser radar (using a continuous wave argon ion laser) installed at the Indian Institute of Tropical Meteorology (IITM), Pune, for remote sounding of atmospheric aerosol characteristics has been briefly described. The day-to-day and height-time variations in the vertical distribution of aerosol number density (up to 3680 m AGL) have been studied by operating the radar on 6 clear days during nighttime in the month of April 1987. The results of the study indicated the formation and redistribution of aerosol layer structure in the lower altitudes (up to 1800 m). Also, conspicuous differences in the height distribution of aerosol number density were noticed between the post-sunset and pre-sunrise periods. The observed features have been explained on the basis of aerosol transport and diffusion processes occurring in the nocturnal urban atmosphere.

  9. Laser Docking System Radar flight experiment

    NASA Technical Reports Server (NTRS)

    Erwin, Harry O.

    1986-01-01

    Flight experiments to verify the Laser Docking System Radar are discussed. The docking requirements are summarized, and the breadboarded hardware is described, emphasizing the two major scanning concepts being utilized: a mechanical scanning technique employing galvanometer beamsteerers and an electronic scanning technique using an image dissector. The software simulations used to apply hardware solutions to the docking requirements are briefly discussed, the tracking test bed is described, and the objectives of the flight experiment are reviewed.

  10. Solid-state coherent laser radar wind shear measuring systems

    NASA Technical Reports Server (NTRS)

    Huffaker, R. Milton

    1992-01-01

    Coherent Technologies, Inc. (CTI) was established in 1984 to engage in the development of coherent laser radar systems and subsystems with applications in atmospheric remote sensing, and in target tracking, ranging and imaging. CTI focuses its capabilities in three major areas: (1) theoretical performance and design of coherent laser radar system; (2) development of coherent laser radar systems for government agencies such as DoD and NASA; and (3) development of coherent laser radar systems for commercial markets. The topics addressed are: (1) 1.06 micron solid-state coherent laser radar system; (2) wind measurement using 1.06 micron system; and flashlamp-pumped 2.09 micron solid-state coherent laser radar system.

  11. Tenth Biennial Coherent Laser Radar Technology and Applications Conference

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J. (Compiler)

    1999-01-01

    The tenth conference on coherent laser radar technology and applications is the latest in a series beginning in 1980 which provides a forum for exchange of information on recent events current status, and future directions of coherent laser radar (or lidar or lader) technology and applications. This conference emphasizes the latest advancement in the coherent laser radar field, including theory, modeling, components, systems, instrumentation, measurements, calibration, data processing techniques, operational uses, and comparisons with other remote sensing technologies.

  12. Tenth Biennial Coherent Laser Radar Technology and Applications Conference

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J. (Compiler)

    1999-01-01

    The tenth conference on coherent laser radar technology and applications is the latest in a series beginning in 1980 which provides a forum for exchange of information on recent events current status, and future directions of coherent laser radar (or lidar or lader) technology and applications. This conference emphasizes the latest advancement in the coherent laser radar field, including theory, modeling, components, systems, instrumentation, measurements, calibration, data processing techniques, operational uses, and comparisons with other remote sensing technologies.

  13. Thirteenth International Laser Radar Conference

    NASA Technical Reports Server (NTRS)

    1986-01-01

    One hundred fifteen papers were presented in both oral and poster sessions. The topics of the conference sessions were: spaceborne lidar applications; extinction/visibility; differential absorption lidar; winds and tropospheric studies; middle atmosphere; clouds and multiple scattering; pollution studies; and new systems.

  14. Laser radar in a system perspective

    NASA Astrophysics Data System (ADS)

    Molebny, Vasyl; Kamerman, Gary; Steinvall, Ove

    2011-06-01

    As a result of recent achievements in the field of laser radars, new options are available for their operation as system components. In addition to complementing and cross-checking one another, system components can generate new synergetic values. In this article, we address various roles and functions that laser radar may perform in a complete system context. Special attention is paid to range-gated imaging ladars operating in conjunction with infrared 2D sensors providing target recognition/identification at long distances and under adverse conditions of natural illumination. The multi- or hyper-spectral features of passive IR or visible sensors may be complemented by multispectral, broadband, tunable or switchable 3D imaging ladar in order to exploit the differences in target reflectance and absorption. This option opens another possibility for multi-spectral, mid-IR ladar to differentiate targets of various types, or to enhance the visualization potential and to facilitate the scene description with small targets like mines or mine-like objects. The recently discovered specificity of Raman scattering in the perturbed sea water makes the long-standing efforts in submarine wake detection more viable. Furthermore, the combination of microwave radar and laser radar, when amplified with new achievements in the fourth generation dual-mode imaging sensors, creates the possibility of single payload configurations suitable for small platforms. Emphasis is also made of the efficiency of Doppler velocimetry for precise vehicle navigation, such as for advance cruise missile control or autonomous landing. Finally, recent advances in coherent micro-ladars for optical coherence tomography now permit the reconstruction of time resolved 3D (i.e., 4D) dynamics of blood flow in heart vessels.

  15. Laser radar measurements of the aerosol content of the atmosphere

    NASA Technical Reports Server (NTRS)

    Grams, G. W.

    1969-01-01

    A summary of the results of laser radar observations of atmospheric aerosols is presented along with a description of the laser radar system devised during the study and of the data handling techniques utilized for the analysis of the data of the temporal and spatial distribution of atmospheric aerosols. Current research conducted by the group is directed toward the analysis of the frequency spectrum of laser radar echoes to obtain absolute measurements of the dust content of the atmosphere by resolving the molecular and aerosol contributions to the laser radar echoes.

  16. Ground-based laser radar measurements of satellite vibrations.

    PubMed

    Schultz, K I; Fisher, S

    1992-12-20

    Vibration signatures from the low-power atmospheric compensation (LACE) satellite are obtained by using the MIT Lincoln Laboratory Firepond coherent CO(2) laser radar facility located in Westford, Mass. The LACE satellite is equipped with IR germanium retroreflectors on deployable/retractable booms to enhance ground-based IR laser radar measurements of on-orbit boom vibrations. Analysis of pulsed cw laser radar measurements of the satellite during and subsequent to boom retraction indicates the presence of a complex time-varying model structure. The observed vibration spectra include vibration modes not previously predicted. These data represent the first observations of satellite vibration modes from a ground-based laser radar.

  17. CO2 laser oscillators for laser radar applications

    NASA Technical Reports Server (NTRS)

    Freed, C.

    1990-01-01

    This paper reviews the spectral purity, frequency stability, and long-term stabilization of newly developed CO2 isotope lasers. Extremely high spectral purity, and short-term stability of less than 1.5 x 10 to the -13th have been achieved. A brief description on using CO2 isotope lasers as secondary frequency standards and in optical radar is given. The design and output characteristics of a single frequency, TEM00q mode, variable pulse width, hybrid TE CO2 laser system is also described. The frequency chirp in the output has been measured and almost completely eliminated by means of a novel technique.

  18. Coherent laser radar atmospheric turbulence sensor

    NASA Astrophysics Data System (ADS)

    Gatt, Philip; Frehlich, Rod G.; Hannon, Stephen M.

    1998-09-01

    A single-ended, range-resolved, refractive turbulence sensor concept was investigated for ground-based and airborne platforms. This technology is of interest to the Air Force's Airborne Laser (ABL) program, because it will enable the determination of optimal engagement paths for the weapons laser. In this paper we describe the performance of a range- resolved refractive turbulence profiler which is based upon a coherent laser radar array receiver technology. We present Monte-Carlo simulation performance predictions for several sensor configurations, including a one micron ABL sensor and an eye-safe two micron ground-based sensor. In addition to its refractive turbulence sensing function, this innovative sensor will be capable of measuring wind velocity and characterizing wind turbulence.

  19. Atmospheric effects on eye-safe airborne laser radar

    NASA Astrophysics Data System (ADS)

    Leslie, Daniel H.; Youmans, Douglas G.

    1995-04-01

    Basing laser radar systems aboard aircraft provides capability for accurate tracking of ground, airborne, and ballistic missile targets from long range. The atmospheric effects of long propagation paths impact the performance of laser radar systems in two important ways -- molecular and aerosol extinction and optical turbulence. This paper provides quantitative assessment of the impact of these effects for laser radar wavelengths beyond 1.4 microns. The treatment of round-trip turbulence on direct detection systems is believed to be the first estimate of this effect. A more complete system analysis is underway and will be described in a forthcoming paper.

  20. Optical reflectance tomography using TCSPC laser radar

    NASA Astrophysics Data System (ADS)

    Henriksson, Markus; Olofsson, Tomas; Grönwall, Christina; Brännlund, Carl; Sjöqvist, Lars

    2012-09-01

    Tomographic signal processing is used to transform multiple one-dimensional range profiles of a target from different angles to a two-dimensional image of the object. The range profiles are measured by a time-correlated single-photon counting (TCSPC) laser radar system with approximately 50 ps range resolution and a field of view that is wide compared to the measured objects. Measurements were performed in a lab environment with the targets mounted on a rotation stage. We show successful reconstruction of 2D-projections along the rotation axis of a boat model and removal of artefacts using a mask based on the convex hull. The independence of spatial resolution and the high sensitivity at a first glance makes this an interesting technology for very long range identification of passing objects such as high altitude UAVs and orbiting satellites but also the opposite problem of ship identification from high altitude platforms. To obtain an image with useful information measurements from a large angular sector around the object is needed, which is hard to obtain in practice. Examples of reconstructions using 90 and 150° sectors are given. In addition, the projection of the final image is along the rotation axis for the measurement and if this is not aligned with a major axis of the target the image information is limited. There are also practical problems to solve, for example that the distance from the sensor to the rotation centre needs to be known with an accuracy corresponding to the measurement resolution. The conclusion is that that laser radar tomography is useful only when the sensor is fixed and the target rotates around its own axis.

  1. Modeling and experiments with a subsea laser radar system

    NASA Astrophysics Data System (ADS)

    Bjarnar, Morten L.; Klepsvik, John O.; Nilsen, Jan E.

    1991-12-01

    Subsea laser radar has a potential for accurate 3-D imaging in water. A prototype system has been developed at Seatex A/S in Norway as a prestudy for the design of an underwater laser radar scanning system. Parallel to the experimental studies, a numerical radiometric model has been developed as an aid in the system design. This model simulates a raster scanning laser radar system for in-water use. Thus this parametric model allows for analysis and predictions of the performance of such a sensor system. Experiments have been conducted to test a prototype laser radar system. The experimental system tested uses a Q-switched, frequency doubled, Nd:YAG solid state laser operating at a wavelength of 532 nm, which is close to optimal for use in water due to the small light attenuation around this wavelength in seawater. The laser has an energy output of 6 (mu) J per pulse 1 kHz pulse repetition frequency (PRF) and the receiver aperture is approximately 17 cm2. The laser radar prototype was mounted onto an accurate pan and tilt unit in order to test the 3-D imaging capabilities. The ultimate goal of the development is to provide an optical 3-D imaging tool for distances comparable to high frequency sonars with a range capability of approximately 30 - 50 m. The results from these experiments are presented. The present implementation of the scanning laser radar model is described and some outputs from the simulation are shown.

  2. Coherent Doppler Laser Radar: Technology Development and Applications

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

    2000-01-01

    NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through

  3. Coherent Doppler Laser Radar: Technology Development and Applications

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Arnold, James E. (Technical Monitor)

    2000-01-01

    NASA's Marshall Space Flight Center has been investigating, developing, and applying coherent Doppler laser radar technology for over 30 years. These efforts have included the first wind measurement in 1967, the first airborne flights in 1972, the first airborne wind field mapping in 1981, and the first measurement of hurricane eyewall winds in 1998. A parallel effort at MSFC since 1982 has been the study, modeling and technology development for a space-based global wind measurement system. These endeavors to date have resulted in compact, robust, eyesafe lidars at 2 micron wavelength based on solid-state laser technology; in a factor of 6 volume reduction in near diffraction limited, space-qualifiable telescopes; in sophisticated airborne scanners with full platform motion subtraction; in local oscillator lasers capable of rapid tuning of 25 GHz for removal of relative laser radar to target velocities over a 25 km/s range; in performance prediction theory and simulations that have been validated experimentally; and in extensive field campaign experience. We have also begun efforts to dramatically improve the fundamental photon efficiency of the laser radar, to demonstrate advanced lower mass laser radar telescopes and scanners; to develop laser and laser radar system alignment maintenance technologies; and to greatly improve the electrical efficiency, cooling technique, and robustness of the pulsed laser. This coherent Doppler laser radar technology is suitable for high resolution, high accuracy wind mapping; for aerosol and cloud measurement; for Differential Absorption Lidar (DIAL) measurements of atmospheric and trace gases; for hard target range and velocity measurement; and for hard target vibration spectra measurement. It is also suitable for a number of aircraft operations applications such as clear air turbulence (CAT) detection; dangerous wind shear (microburst) detection; airspeed, angle of attack, and sideslip measurement; and fuel savings through

  4. Integrated laser/radar satellite ranging and tracking system.

    PubMed

    Hoge, F E

    1974-10-01

    A laser satellite ranging system that is mounted upon and integrated with a microwave tracking radar is reported. The 1-pulse sec/ruby laser transmitter is attached directly to the radar's elevation axis and radiates through a new opening in the radar's parabolic dish. The laser photomultiplier tube receiver utilizes the radar's existing 20-cm diam f11 boresight telescope and observes through a similar symmetrically located opening in the dish. The laser system possesses separate ranging system electronics but shares the radar's timing, computer, and data handling[equation]recording systems. The basic concept of the laser[equation]radar is outlined together with a listing of the numerous advantages over present singular laser rangefinding systems. The developmental laser hardware is described along with preliminary rangefinding results and expectations. The prototype system was assembled to investigate the feasibility of such systems and aid in the development of detailed specifications for an operational system. Both the feasibility and desirability of such systems integrations have been adequately demonstrated.

  5. Review of pulsed CO2 laser radar technology

    NASA Astrophysics Data System (ADS)

    Hasson, V.

    The utility of CO2 laser radars is reviewed, and some relevant key transmitter technology issues are discussed. The utility aspect focuses on waveform and architectures and highlights the overall importance of the transmitter, from a weight/size/power consumption standpoint, in a laser radar system. The transmitter review covers major transmitter issues, namely, discharge techniques, frequency fidelity, and associated flow and acoustics control.

  6. The 3D laser radar vision processor system

    NASA Technical Reports Server (NTRS)

    Sebok, T. M.

    1990-01-01

    Loral Defense Systems (LDS) developed a 3D Laser Radar Vision Processor system capable of detecting, classifying, and identifying small mobile targets as well as larger fixed targets using three dimensional laser radar imagery for use with a robotic type system. This processor system is designed to interface with the NASA Johnson Space Center in-house Extra Vehicular Activity (EVA) Retriever robot program and provide to it needed information so it can fetch and grasp targets in a space-type scenario.

  7. Compact multichannel imaging laser radar receiver

    NASA Astrophysics Data System (ADS)

    Burns, Hoyt N.; Yun, Steven T.; Keltos, Michael L.; Kimmet, James S.

    1999-05-01

    Direct detection imaging Laser Radar (LADAR) produces 3-dimensional range imagery that can be processed to provide target acquisition and precision aimpoint definition in real time. This paper describes the current status of the Parallel Multichannel Imaging LADAR Receiver (PMR), developed under an SBIR Phase II program by the Air Force Research Laboratory, Munitions Directorate (AFRL/MN). The heart of the PMR is the Multichannel Optical Receiver Photonic Hybrid (MORPH), a high performance 16-channel LADAR receiver card which includes fiber-coupled detectors, pulse discrimination, and range counting circuitry on a 3 X 5 inch circuit card. The MORPH provides high downrange resolution (3 inches), multiple-hit (8 per channel) range and reflectance data for each detector. Silicon (Si) and indium gallium arsenide (InGaAs) pin diode or avalanche photodiode (APD) detectors are supported. The modular PMR uses an array of MORPH circuit cards to form a compact multichannel imaging LADAR receiver with any multiple of 16 channels. A 32-channel system measures 3 X 5 X 1.4 inches and weighs 1 lb. A prototype PMR system is currently undergoing field-testing. This paper focuses on field test results and applications of the PMR technology.

  8. Coherent laser radar at 2 microns using solid-state lasers

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Suni, Paul J. M.; Hale, Charley P.; Hannon, Stephen M.; Magee, James R.; Bruns, Dale L.; Yuen, Eric H.

    1993-01-01

    Coherent laser radar systems using 2-micron Tm- and Tm, Ho-doped solid-state lasers are useful for the remote range-resolved measurement of atmospheric winds, aerosol backscatter, and DIAL measurements of atmospheric water vapor and CO2 concentrations. Recent measurements made with a 2-micron coherent laser radar system, advances in the laser technology, and atmospheric propagation effects on 2-micron coherent lidar performance are described.

  9. Laser radar technology and applications; Proceedings of the Meeting, Quebec, Canada, June 3-5, 1986

    NASA Astrophysics Data System (ADS)

    Cruickshank, James M.; Harney, Robert C.

    1986-01-01

    Various papers on laser radar technology and applications are presented. The topics considered include: eye-safe solid lasers for lidar applications, practical DF laser for ranging applications, ultrafast surface barrier photodetectors, performance analyses for peak-detecting laser radars, multiple scattering for laser beams propagating in a layered atmosphere, laser radar cross section of objects immersed in the earth's atmosphere, measurements of pulse coherence in mode-locked TEA-CO2 lasers, and single longitudinal mode operation of a continuously tunable high pressure TE-CO2. Also discussed are: amplitude-modulated laser system for distance and displacement measurement, minilaser rangefinder, laser docking system radar flight experiment, improved optical resonator for laser radars, design of frequency-stable TEA-CO2 lasers, HgCdTe photodiodes for heterodyne applications, acoustooptic spectrum analyzer for laser radar applications, laser cloud mapper and its applications, scanning lidar bathymeter for water depth measurement, and fluorescence lidar for land and sea remote sensing.

  10. Laser radar observation of the polar stratospheric aerosol layer

    NASA Technical Reports Server (NTRS)

    Iwasaka, Y.; Hirasawa, T.; Fukunishi, H.; Fujiwara, M.; Fujii, R.; Miyaoka, H.

    1985-01-01

    The polar stratosphere has been speculated to be an active sink region of various stratospheric materials; ozone, water vapor, NOX, aerosol particles and so on, but this process is not theoretically and/or observationally made clear. The observation of the polar stratospheric aerosol layer using laser radar certainly contributes to the study of the global transport of these stratospheric minor constituents. In addition to this, from the viewpoint of aerosol science, there may be many interesting phenomena which cannot be found in the stratosphere at mid and low latitudes; the effect of precipitation of high energy molecules and atoms, of very cold winter stratosphere, of very cold mesopause in summer. Laser radar observation is one of the main activities of the Antarctic Middle Atmosphere (AMA) project at Syowa Station (69.00 deg S, 39.35 deg E), Antarctica since May 1983. Laser radar measurement at Syowa Station is discussed in detail.

  11. Coherent laser radar at 3.6 microm.

    PubMed

    Hanson, Frank; Lasher, Mark

    2002-12-20

    Coherent laser radar systems in the mid-IR wavelength region can have advantages in low-altitude environment because they are less sensitive to scattering, turbulence, and humidity, which can affect shorter- or longer-wavelength system. We describe a coherent laser radar at 3.6 microm based on a single-frequency optical parametric oscillator and demonstrate the system over short ranges outdoors. The system was used to make micro-Doppler measurements from idling trucks that were processed to give surface vibration spectra.

  12. Fiber optic coherent laser radar 3d vision system

    SciTech Connect

    Sebastian, R.L.; Clark, R.B.; Simonson, D.L.

    1994-12-31

    Recent advances in fiber optic component technology and digital processing components have enabled the development of a new 3D vision system based upon a fiber optic FMCW coherent laser radar. The approach includes a compact scanner with no moving parts capable of randomly addressing all pixels. The system maintains the immunity to lighting and surface shading conditions which is characteristic of coherent laser radar. The random pixel addressability allows concentration of scanning and processing on the active areas of a scene, as is done by the human eye-brain system.

  13. Applications of FM-CW laser radar to antenna contour mapping

    NASA Technical Reports Server (NTRS)

    Slotwinski, A. R.

    1989-01-01

    The FM-CW coherent laser radar concept, based on the FM radar principle which makes use of the coherence and lunability of injection laser diodes, is discussed. Laser radar precision/time tradeoffs, block diagrams, system performance, fiber optic system implantation, and receiver improvements are briefly described.

  14. Clutter discrimination algorithm simulation in pulse laser radar imaging

    NASA Astrophysics Data System (ADS)

    Zhang, Yan-mei; Li, Huan; Guo, Hai-chao; Su, Xuan; Zhu, Fule

    2015-10-01

    Pulse laser radar imaging performance is greatly influenced by different kinds of clutter. Various algorithms are developed to mitigate clutter. However, estimating performance of a new algorithm is difficult. Here, a simulation model for estimating clutter discrimination algorithms is presented. This model consists of laser pulse emission, clutter jamming, laser pulse reception and target image producing. Additionally, a hardware platform is set up gathering clutter data reflected by ground and trees. The data logging is as clutter jamming input in the simulation model. The hardware platform includes a laser diode, a laser detector and a high sample rate data logging circuit. The laser diode transmits short laser pulses (40ns FWHM) at 12.5 kilohertz pulse rate and at 905nm wavelength. An analog-to-digital converter chip integrated in the sample circuit works at 250 mega samples per second. The simulation model and the hardware platform contribute to a clutter discrimination algorithm simulation system. Using this system, after analyzing clutter data logging, a new compound pulse detection algorithm is developed. This new algorithm combines matched filter algorithm and constant fraction discrimination (CFD) algorithm. Firstly, laser echo pulse signal is processed by matched filter algorithm. After the first step, CFD algorithm comes next. Finally, clutter jamming from ground and trees is discriminated and target image is produced. Laser radar images are simulated using CFD algorithm, matched filter algorithm and the new algorithm respectively. Simulation result demonstrates that the new algorithm achieves the best target imaging effect of mitigating clutter reflected by ground and trees.

  15. The design of infrared laser radar for vehicle initiative safety

    NASA Astrophysics Data System (ADS)

    Gong, Ping; Xu, Xi-ping; Li, Xiao-yu; Li, Tian-zhi; Liu, Yu-long; Wu, Jia-hui

    2013-09-01

    Laser radar for vehicle is mainly used in advanced vehicle on-board active safety systems, such as forward anti-collision systems, active collision warning systems and adaptive cruise control systems, etc. Laser radar for vehicle plays an important role in the improvement of vehicle active safety and the reduction of traffic accidents. The stability of vehicle active anti-collision system in dynamic environment is still one of the most difficult problems to break through nowadays. According to people's driving habit and the existed detecting technique of sensor, combining the infrared laser range and galvanometer scanning technique , design a 3-D infrared laser radar which can be used to assist navigation, obstacle avoidance and the vehicle's speed control for the vehicle initiative safety. The device is fixed to the head of vehicle. Then if an accident happened, the device could give an alarm to remind the driver timely to decelerate or brake down, by which way can people get the purpose of preventing the collision accidents effectively. To accomplish the design, first of all, select the core components. Then apply Zemax to design the transmitting and receiving optical system. Adopt 1550 nm infrared laser transmitter as emission unit in the device, a galvanometer scanning as laser scanning unit and an InGaAs-APD detector as laser echo signal receiving unit. Perform the construction of experimental system using FPGA and ARM as the core controller. The system designed in this paper can not only detect obstacle in front of the vehicle and make the control subsystem to execute command, but also transfer laser data to PC in real time. Lots of experiments using the infrared laser radar prototype are made, and main performance of it is under tested. The results of these experiments show that the imaging speed of the laser radar can reach up to 25 frames per second, the frame resolution of each image can reach 30×30 pixels, the horizontal angle resolution is about 6. 98

  16. 3-D Imaging of Partly Concealed Targets by Laser Radar

    DTIC Science & Technology

    2005-10-01

    laser in the green wavelength region was used for illumination. 3-D Imaging of Partly Concealed Targets by Laser Radar 11 - 8 RTO-MP-SET-094...acknowledge Marie Carlsson and Ann Charlotte Gustavsson for their assistance in some of the experiments. 7.0 REFERENCES [1] U. Söderman, S. Ahlberg...SPIE Vol. 3707, pp. 432-448, USA, 1999. [14] D. Letalick, H. Larsson, M. Carlsson, and A.-C. Gustavsson , “Laser sensors for urban warfare,” FOI

  17. Monitoring internal organ motion with continuous wave radar in CT

    SciTech Connect

    Pfanner, Florian; Maier, Joscha; Allmendinger, Thomas; Flohr, Thomas; Kachelrieß, Marc

    2013-09-15

    Purpose: To avoid motion artifacts in medical imaging or to minimize the exposure of healthy tissues in radiation therapy, medical devices are often synchronized with the patient's respiratory motion. Today's respiratory motion monitors require additional effort to prepare the patients, e.g., mounting a motion belt or placing an optical reflector on the patient's breast. Furthermore, they are not able to measure internal organ motion without implanting markers. An interesting alternative to assess the patient's organ motion is continuous wave radar. The aim of this work is to design, implement, and evaluate such a radar system focusing on application in CT.Methods: The authors designed a radar system operating in the 860 MHz band to monitor the patient motion. In the intended application of the radar system, the antennas are located close to the patient's body inside the table of a CT system. One receive and four transmitting antennas are used to avoid the requirement of exact patient positioning. The radar waves propagate into the patient's body and are reflected at tissue boundaries, for example at the borderline between muscle and adipose tissue, or at the boundaries of organs. At present, the authors focus on the detection of respiratory motion. The radar system consists of the hardware mentioned above as well as of dedicated signal processing software to extract the desired information from the radar signal. The system was evaluated using simulations and measurements. To simulate the radar system, a simulation model based on radar and wave field equations was designed and 4D respiratory-gated CT data sets were used as input. The simulated radar signals and the measured data were processed in the same way. The radar system hardware and the signal processing algorithms were tested with data from ten volunteers. As a reference, the respiratory motion signal was recorded using a breast belt simultaneously with the radar measurements.Results: Concerning the

  18. Monitoring internal organ motion with continuous wave radar in CT.

    PubMed

    Pfanner, Florian; Maier, Joscha; Allmendinger, Thomas; Flohr, Thomas; Kachelrieß, Marc

    2013-09-01

    To avoid motion artifacts in medical imaging or to minimize the exposure of healthy tissues in radiation therapy, medical devices are often synchronized with the patient's respiratory motion. Today's respiratory motion monitors require additional effort to prepare the patients, e.g., mounting a motion belt or placing an optical reflector on the patient's breast. Furthermore, they are not able to measure internal organ motion without implanting markers. An interesting alternative to assess the patient's organ motion is continuous wave radar. The aim of this work is to design, implement, and evaluate such a radar system focusing on application in CT. The authors designed a radar system operating in the 860 MHz band to monitor the patient motion. In the intended application of the radar system, the antennas are located close to the patient's body inside the table of a CT system. One receive and four transmitting antennas are used to avoid the requirement of exact patient positioning. The radar waves propagate into the patient's body and are reflected at tissue boundaries, for example at the borderline between muscle and adipose tissue, or at the boundaries of organs. At present, the authors focus on the detection of respiratory motion. The radar system consists of the hardware mentioned above as well as of dedicated signal processing software to extract the desired information from the radar signal. The system was evaluated using simulations and measurements. To simulate the radar system, a simulation model based on radar and wave field equations was designed and 4D respiratory-gated CT data sets were used as input. The simulated radar signals and the measured data were processed in the same way. The radar system hardware and the signal processing algorithms were tested with data from ten volunteers. As a reference, the respiratory motion signal was recorded using a breast belt simultaneously with the radar measurements. Concerning the measurements of the test persons

  19. Application of the staring-edge tracking in laser radar

    NASA Astrophysics Data System (ADS)

    He, Lianhe; Wu, Jian

    1997-04-01

    The extended target that the size is larger that the diameter of the light beam can be tracked in the laser tracking radar designed on the basic of the method and the algorithm of the staring edge tracking. A moving aluminium plate is tracked by a coherent CO2 laser tracking radar facility with transmitter power 5W and the divergent angle of the transmitter light beam less than 0.18 mrad at a n approximate range of 1 km. The error signals of the azimuth and the elevation are generated from the quad detector. This successful experiment results indicates that the question that the traditional tracking method of quad detector is vain to the extended target has been overcome and testifies that our theory of the staring edge tracking is correct. This tracking method has many advantages. For example, is we choose the tracking position at the top of the target, then the ground target is not easy to lose. So it can avoid tracking the ground. On the other hand, the range of the laser radar using this method is longer than the range of the radar using the point tracking, because the target using narrow light beam illumination is taken as an extended Lambertian target.

  20. CIE 1991 International Conference on Radar (CICR-91), Beijing, China, Oct. 22-24, 1991, Proceedings

    NASA Astrophysics Data System (ADS)

    Li, Nengjing; Zhou, Siyong

    The present volume on radar discusses a modern perspective on radar signal processing, a historical survey on airborne early warning, array pattern and target parameter estimation for distributed array radar, and a review of surface surveillance radars. Attention is given to new concepts of spaceborne surveillance radar, UHF Doppler wind-profiling radar and performance analyses, a low-angle tracking method for tactical monopulse radars, and a laser radar for the detection of cables and other hazardous obstacles. Topics addressed include real-time multifunction radar simulation, new estimators of probability tails for radar application, an advanced low-altitude search radar, and beam spacing optimization for a surveillance phased array radar. Also discussed are broadband aspects of a triple-patch antenna as an array element, an effective way to analyze broadband radomes, selective devices on magnetostatic surface waves, and the orthogonality algorithm in adaptive arrays.

  1. Development Of CO2 Laser Amplifiers For Radar Applications

    NASA Astrophysics Data System (ADS)

    Yoder, M. J.; Youmans, D. G.; Reilly, J. P.

    1987-01-01

    Laser radar oscillators are necessarily low output power devices since (1) short optical cavities and low pressure operating conditions are required for minimum fluctuations, (2) short laser cavities and low pressures are required for single frequency, single longitudinal mode operation, and (3) small optical beam cross-sections are required for single transverse mode operation. All of these combined restrictions severely limit the attainable output power and stability of oscillators. Amplifiers, on the other hand, have no such restrictions in discharge length, gas pressure or optical cross-section. With regard to frequency stability, amplifiers are more forgiving than oscillators since only the time variation of the electron and gas density gradients affects the frequency stability. TETIi oscillator-amplifier configurations are used whenever moderate to high power (greater than about 50 watts) applications are desired. In this paper the design of amplifiers for CO, laser radar applications will be presented. This discussion will examine the issues of discharge technique selection, gain requirements, frequency stability requirements/achievability, optical folding schemes to obtain high gain-length products, backward wave feed-back minimization/suppression, and flow requirements/achievability for high average power operation. These are some of the issues that must be considered in the design of moderate power CW and pulsed laser radar amplifiers for short and long range applications.

  2. Three-dimensional environment models from airborne laser radar data

    NASA Astrophysics Data System (ADS)

    Soderman, Ulf; Ahlberg, Simon; Elmqvist, Magnus; Persson, Asa

    2004-09-01

    Detailed 3D environment models for visualization and computer based analyses are important in many defence and homeland security applications, e.g. crisis management, mission planning and rehearsal, damage assessment, etc. The high resolution data from airborne laser radar systems for 3D sensing provide an excellent source of data for obtaining the information needed for many of these models. To utilise the 3D data provided by the laser radar systems however, efficient methods for data processing and environment model construction needs to be developed. In this paper we will present some results on the development of laser data processing methods, including methods for data classification, bare earth extraction, 3D-reconstruction of buildings, and identification of single trees and estimation of their position, height, canopy size and species. We will also show how the results can be used for the construction of detailed 3D environment models for military modelling and simulation applications. The methods use data from discrete return airborne laser radar systems and digital cameras.

  3. Compact 625-channel scannerless imaging laser radar receiver

    NASA Astrophysics Data System (ADS)

    Burns, Hoyt N.; Steiner, Todd D.; Hayden, David R.

    1996-06-01

    In 1995, under a USAF SBIR Phase I program, Burns Engineering Corporation investigated the application of new integrated photonics technologies and hybrid manufacturing processes to the miniaturization of an imaging laser radar receiver which has complete receiving and range counting circuitry for each pixel in a 25-by-25 element avalanche photodiode array. The `parallel multichannel' receiver (PMR) is a compact, robust, and modular laser radar subsystem which can produce high resolution 3D range imagery at 1 kHz frame rates without the use of a scanner. The modular PMR is attractive as a common module solution for a wide variety of high performance, low cost, autonomous laser-guided seeker applications. The system described illustrates one approach to integrating and packaging high-density photonic arrays and associated signal processing electronics to yield a high-performance imaging laser radar receiver using existing technology. Burns Engineering has been selected by the USAF to build a benchtop prototype, proof-of-concept demonstrator in a follow-on, SBIR Phase II program.

  4. Laser radar: historical prospective-from the East to the West

    NASA Astrophysics Data System (ADS)

    Molebny, Vasyl; McManamon, Paul; Steinvall, Ove; Kobayashi, Takao; Chen, Weibiao

    2017-03-01

    This article discusses the history of laser radar development in America, Europe, and Asia. Direct detection laser radar is discussed for range finding, designation, and topographic mapping of Earth and of extraterrestrial objects. Coherent laser radar is discussed for environmental applications, such as wind sensing and for synthetic aperture laser radar development. Gated imaging is discussed through scattering layers for military, medical, and security applications. Laser microradars have found applications in intravascular studies and in ophthalmology for vision correction. Ghost laser radar has emerged as a new technology in theoretical and simulation applications. Laser radar is now emerging as an important technology for applications such as self-driving cars and unmanned aerial vehicles. It is also used by police to measure speed, and in gaming, such as the Microsoft Kinect.

  5. Surface emitting distributed feedback laser as a source for laser radar

    NASA Astrophysics Data System (ADS)

    Akkapeddi, P.; Macomber, S. H.

    1991-08-01

    The requirements for a diode source for a laser radar system are presented. It is shown how microcollimation of incoherent diode laser arrays can produce a usable beam divergence. A unique diode source under development and the associated technologies required for a compact, efficient, reliable and low divergence source are described.

  6. Novel Doppler laser radar for diagnostics in fusion reactors

    SciTech Connect

    Menon, Madhavan; Slotwinski, Anthony

    2004-10-01

    We describe the development of a novel Doppler laser radar (DOLAR) for remote measurement of flow velocity (0-10 m/s) and film thickness of liquid metal walls, currently being studied for their superior heat handling and self-healing characteristics. Small fluctuations in flow velocity({approx}mm/s) and flow thickness ({approx}50 {mu}m) that may arise during plasma discharges can also be measured. The DOLAR is also designed for non intrusive mapping of features of plasma-facing solid surfaces with very high precision ({approx}50 {mu}m). It can also measure the motion of structural components of a fusion reactor during plasma discharges and during plasma disruptions. The device utilizes frequency modulation laser radar principles for precision range measurements. Compensation of Doppler frequency shift is used to measure flow velocity. The DOLAR probe head is designed with acousto-optic and piezoelectric devices for operation in the harsh fusion environment.

  7. Eye-safe coherent laser radar system at 2.1 microns using Tm,Ho:YAG lasers

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Hale, Charley P.; Magee, James R.; Kavaya, Michael J.; Huffaker, A. V.

    1991-01-01

    An eye-safe pulsed coherent laser radar has been developed by using single-frequency Tm,Ho:YAG lasers and heterodyne detection. Returns from a mountainside located 145 km from the laser radar system and the measurement of wind velocity to ranges exceeding 20 km have been demonstrated with transmitted pulse energies of 22 mJ.

  8. Precision metrology of NSTX surfaces using coherent laser radar ranging

    SciTech Connect

    H.W. Kugel; D. Loesser; A. L. Roquemore; M. M. Menon; R. E. Barry

    2000-07-13

    A frequency modulated Coherent Laser Radar ranging diagnostic is being used on the National Spherical Torus Experiment (NSTX) for precision metrology. The distance (range) between the 1.5 {micro}m laser source and the target is measured by the shift in frequency of the linearly modulated beam reflected off the target. The range can be measured to a precision of < 100{micro}m at distances of up to 22 meters. A description is given of the geometry and procedure for measuring NSTX interior and exterior surfaces during open vessel conditions, and the results of measurements are elaborated.

  9. Laser radar speckle and glint statistics - Illustrations using AMOR data

    NASA Astrophysics Data System (ADS)

    Youmans, Douglas G.

    1990-05-01

    This paper shows how these signal probability density functions in power and in voltage propagate down the signal processing electronics chain using data from the Army Missile Optical Range (AMOR) facility. The AMOR targets considered here are 'analytical targets' consisting of rotating diffuse disks and rotating diffuse spheres illuminated by a CO2 laser. It is hoped that the analyses presented will clarify and clearly illustrate the origins of these various signal probability density functions with the added benefit that the signal processing calculations are performed on data from a coherent laser radar system.

  10. Holographic frequency modulated continuous wave laser radar

    NASA Astrophysics Data System (ADS)

    Delaye, P.; Roosen, G.

    2007-10-01

    We present the operating principle and a first experimental characterization of a holographic rangefinder, that couples a two wave mixing phase demodulation set-up with a frequency modulated laser source. In its first implementation, the system allows millimetre sensitivity on tens of meters measurement range with the ability to work with scattering surfaces. This paper has been presented at “3e colloque interdisciplinaire en instrumentation (C2I 2004)”, École Normale Supérieure de Cachan, 29 30 janvier 2004.

  11. Study of imaging radar using ultra-wideband microwave-modulated infrared laser

    NASA Astrophysics Data System (ADS)

    Mase, Atsushi; Kogi, Yuichiro; Ikezi, Hiroyuki; Inutake, Masaaki; Wang, Xiaolong

    2016-09-01

    In this paper, we present an ultra-wideband microwave-modulated laser radar which is designed and fabricated for improvement of the spatial resolution both in the range direction and the azimuth direction. The amplitude modulation in a range of 0.01-18 GHz is applied to an infrared laser source of 1550 nm wavelength. The frequency and the bandwidth are assigned by the Administration of Radio under the Ministry of Internal Affairs and Communications in Japan. However, there is no bandwidth limitation in the infrared region. Considering the influence of radiation pattern for microwave antennas case, there is no side lobe in laser beam transmission. Ambiguous signal and interferences which are returned from the ground can be suppressed. A prototype of laser-radar system with a fiber collimator for both transmitting and receiving optics has been fabricated. A vector network analyzer is used to obtain S21 signal between the microwave modulation input and that of received signal. The system is, at first, applied to the measurement of the distance (position) of an object. It is proved that the spatial resolution is less than 1 cm during 5-10 m. As an initial experiment, we have succeeded to obtain 3D image of object by scanning a laser beam in two dimensions.

  12. Three-dimensional imaging laser radar with a photon-counting avalanche photodiode array and microchip laser.

    PubMed

    Albota, Marius A; Heinrichs, Richard M; Kocher, David G; Fouche, Daniel G; Player, Brian E; O'Brien, Michael E; Aull, Brian F; Zayhowski, John J; Mooney, James; Willard, Berton C; Carlson, Robert R

    2002-12-20

    We have developed a threedimensional imaging laser radar featuring 3-cm range resolution and single-photon sensitivity. This prototype direct-detection laser radar employs compact, all-solid-state technology for the laser and detector array. The source is a Nd:YAG microchip laser that is diode pumped, passively Q-switched, and frequency doubled. The detector is a gated, passively quenched, two-dimensional array of silicon avalanche photodiodes operating in Geigermode. After describing the system in detail, we present a three-dimensional image, derive performance characteristics, and discuss our plans for future imaging three-dimensional laser radars.

  13. Theoretical distribution of range data obtained by laser radar and its applications

    NASA Astrophysics Data System (ADS)

    Haijiao, Jiang; Jiancheng, Lai; Wei, Yan; Chunyong, Wang; Zhenhua, Li

    2013-02-01

    This paper addresses the distribution of range data obtained by laser radar. An analytical solution of the range distribution was obtained for direct detection laser radar using constant threshold discriminator based on the time-of-flight principle. The analytical solution was verified by experiments and simulations. The results show that the derived analytical function can describe the probability density distribution of the range data obtained by laser radar with a constant threshold discriminator. The probability density distribution of the range data is proportional to the probability density function of the noise and to the slope of the rising edge of the laser echo pulse. The probability density distributions of the range data obtained by laser radar with different pulse shapes, amplitudes, widths and thresholds are also presented. These factors are important for improvements in the design of laser radar systems.

  14. Coherent laser radar at 1.06 micron using Nd:YAG lasers

    NASA Technical Reports Server (NTRS)

    Kane, Thomas J.; Kozlovsky, W. J.; Byer, Robert L.; Byvik, Charles E.

    1987-01-01

    A coherent laser radar system operating at the 1.06 micron Nd:YAG laser wavelength has been built and operated. A laser-diode-pumped monolithic ring laser served as the master oscillator. A single flash-lamp-pumped zigzag slab amplified the oscillator output to a power of 2.3 kW. Single-mode optical fiber was used to collect and mix the return signal with the local-oscillator output. Signals from clouds at a range of 2.7 km and from atmospheric aerosols at a range of 600 m were detected.

  15. Time and wavelength domain algorithms for chemical analysis by laser radar

    NASA Technical Reports Server (NTRS)

    Rosen, David L.; Gillespie, James B.

    1992-01-01

    Laser-induced fluorescence (LIF) is a promising technique for laser radar applications. Laser radar using LIF has already been applied to algae blooms and oil slicks. Laser radar using LIF has great potential for remote chemical analysis because LIF spectra are extremely sensitive to chemical composition. However, most samples in the real world contain mixtures of fluorescing components, not merely individual components. Multicomponent analysis of laser radar returns from mixtures is often difficult because LIF spectra from solids and liquids are very broad and devoid of line structure. Therefore, algorithms for interpreting LIF spectra from laser radar returns must be able to analyze spectra that overlap in multicomponent systems. This paper analyzes the possibility of using factor analysis-rank annihilation (FARA) to analyze emission-time matrices (ETM) from laser radar returns instead of excitation-emission matrices (EEM). The authors here define ETM as matrices where the rows (or columns) are emission spectra at fixed times and the columns (or rows) are temporal profiles for fixed emission wavelengths. Laser radar usually uses pulsed lasers for ranging purposes, which are suitable for measuring temporal profiles. Laser radar targets are hard instead of diffuse; that is, a definite surface emits the fluorescence instead of an extended volume. A hard target would not broaden the temporal profiles as would a diffuse target. Both fluorescence lifetimes and emission spectra are sensitive to chemical composition. Therefore, temporal profiles can be used instead of excitation spectra in FARA analysis of laser radar returns. The resulting laser radar returns would be ETM instead of EEM.

  16. Terahertz Inverse Synthetic Aperture Radar (ISAR) Imaging With a Quantum Cascade Laser Transmitter

    DTIC Science & Technology

    2010-01-01

    Terahertz inverse synthetic aperture radar ( ISAR ) imaging with a quantum cascade laser transmitter Andriy A. Danylov1,*, Thomas M. Goyette1...COVERED 00-00-2010 to 00-00-2010 4. TITLE AND SUBTITLE Terahertz inverse synthetic aperture radar ( ISAR ) imaging with a quantum cascade laser...Coherence imaging ; (280.6730) Synthetic aperture radar . References and links 1. S. Barbieri, J. Alton, C. Baker, T. Lo, H. Beere, and D

  17. Off the line-of-sight laser radar.

    PubMed

    Krishnaswami, K; Tilleman, M

    1998-01-20

    The results of field and laboratory experiments of a novel laser radar (ladar) are presented. This ladar was designed to detect objects off the line of sight by deploying a fiber-optic relay between the launch and probe sites by monitoring the retroreflected signals. The apparatus incorporates a pulsed diode laser emitting at 1.55 mum, a wavelength that is ideal for eye safety and bears minimum loss in silica fibers. With its immediate application in transportation safety, the system issues a warning within a millisecond of detecting an obstacle in the path of a vehicle. The results of the field experiments yield signal-to-noise ratios high enough to trigger reliably an alarm with a probability of greater than 0.999 for detecting an obstacle and less than 10(-12) probability of false alarms.

  18. Agile beam laser radar using computational imaging for robotic perception

    NASA Astrophysics Data System (ADS)

    Powers, Michael A.; Stann, Barry L.; Giza, Mark M.

    2015-05-01

    This paper introduces a new concept that applies computational imaging techniques to laser radar for robotic perception. We observe that nearly all contemporary laser radars for robotic (i.e., autonomous) applications use pixel basis scanning where there is a one-to-one correspondence between world coordinates and the measurements directly produced by the instrument. In such systems this is accomplished through beam scanning and/or the imaging properties of focal-plane optics. While these pixel-basis measurements yield point clouds suitable for straightforward human interpretation, the purpose of robotic perception is the extraction of meaningful features from a scene, making human interpretability and its attendant constraints mostly unnecessary. The imposing size, weight, power and cost of contemporary systems is problematic, and relief from factors that increase these metrics is important to the practicality of robotic systems. We present a system concept free from pixel basis sampling constraints that promotes efficient and adaptable sensing modes. The cornerstone of our approach is agile and arbitrary beam formation that, when combined with a generalized mathematical framework for imaging, is suited to the particular challenges and opportunities of robotic perception systems. Our hardware concept looks toward future systems with optical device technology closely resembling modern electronically-scanned-array radar that may be years away from practicality. We present the design concept and results from a prototype system constructed and tested in a laboratory environment using a combination of developed hardware and surrogate devices for beam formation. The technological status and prognosis for key components in the system is discussed.

  19. Laser induced x-ray `RADAR' particle physics model

    NASA Astrophysics Data System (ADS)

    Lockley, D.; Deas, R.; Moss, R.; Wilson, L. A.; Rusby, D.; Neely, D.

    2016-05-01

    The technique of high-power laser-induced plasma acceleration can be used to generate a variety of diverse effects including the emission of X-rays, electrons, neutrons, protons and radio-frequency radiation. A compact variable source of this nature could support a wide range of potential applications including single-sided through-barrier imaging, cargo and vehicle screening, infrastructure inspection, oncology and structural failure analysis. This paper presents a verified particle physics simulation which replicates recent results from experiments conducted at the Central Laser Facility at Rutherford Appleton Laboratory (RAL), Didcot, UK. The RAL experiment demonstrated the generation of backscattered X-rays from test objects via the bremsstrahlung of an incident electron beam, the electron beam itself being produced by Laser Wakefield Acceleration. A key initial objective of the computer simulation was to inform the experimental planning phase on the predicted magnitude of the backscattered X-rays likely from the test objects. This objective was achieved and the computer simulation was used to show the viability of the proposed concept (Laser-induced X-ray `RADAR'). At the more advanced stages of the experimental planning phase, the simulation was used to gain critical knowledge of where it would be technically feasible to locate key diagnostic equipment within the experiment. The experiment successfully demonstrated the concept of X-ray `RADAR' imaging, achieved by using the accurate timing information of the backscattered X-rays relative to the ultra-short laser pulse used to generate the electron beam. By using fast response X-ray detectors it was possible to derive range information for the test objects being scanned. An X-ray radar `image' (equivalent to a RADAR B-scan slice) was produced by combining individual X-ray temporal profiles collected at different points along a horizontal distance line scan. The same image formation process was used to generate

  20. End-to-end laser radar range code for coherent cw lasers

    NASA Astrophysics Data System (ADS)

    Yoder, M. John; Seliverstov, Dima

    1996-06-01

    A user friendly modular computer code is described for CW coherent laser radar which includes all relevant physical effects needed to evaluate the probability of detection versus time after launch for ballistic missiles or other targets of interest. The beginning point of the code is the conventional laser radar range equation. Atmospheric attenuation is determined from an integral FASCODE calculation, and the laser radar range equation is solved for a curved-earth geometry including free air turbulence induced beam spreading. Several different atmospheric turbulence models are selectable. Target cross-sections can be input into the code as a function of aspect angle Coherence time and transverse coherence length limits are included in the code. Beam jitter effects are also calculated. The carrier-to-noise ratio is calculated including all of these (complicated) variables and degradations. The code then calculates the probability of detection of the target as a function of time using incoherent integration of coherent sub-pulses. The governing equations and practical results are presented for detection and tracking of long range theater ballistic missiles from airborne surveillance platforms. The use of CW lasers requires increased measurement times compared to pulsed lasers and results in an averaging of the target fading statistics.

  1. Construction and testing of a Scanning Laser Radar (SLR), phase 2

    NASA Technical Reports Server (NTRS)

    Flom, T.; Coombes, H. D.

    1971-01-01

    The scanning laser radar overall system is described. Block diagrams and photographs of the hardware are included with the system description. Detailed descriptions of all the subsystems that make up the scanning laser radar system are included. Block diagrams, photographs, and detailed optical and electronic schematics are used to help describe such subsystem hardware as the laser, beam steerer, receiver optics and detector, control and processing electronics, visual data displays, and the equipment used on the target. Tests were performed on the scanning laser radar to determine its acquisition and tracking performance and to determine its range and angle accuracies while tracking a moving target. The tests and test results are described.

  2. Laser radar V; Proceedings of the Meeting, Los Angeles, CA, Jan. 18, 19, 1990

    NASA Astrophysics Data System (ADS)

    Becherer, Richard J.

    1990-05-01

    Various papers on laser radar are presented. Individual topics addressed include: active-passive detection of multipixel targets, laser radar angular tracking, laser radar speckle and glint statistics using AMOR data, signal isolation capability of rotating-wave-plate type electrooptic modulators, Ti:Al2O3 laser amplifier design, design and performance measurements of an airborne aerosol backscatter lidar, pulsed coherent solid-state 1.06 micron and 2.1 micron laser radar systems for remote velocity measurement, low-cost CW CO2 lidar system for low-level wind shear detection. Also discussed are: design of a high pulse repetition rate CO2 Doppler lidar for atmospheric monitoring, necessity for relativistic correction of Doppler ladar on a polar orbiting platform, mechanical design of a lidar system for space applications LITE, optimization of the alexandrite laser tuning elements for a water vapor lidar, airborne water vapor DIAL system development, lidar system for measuring atmospheric pressure and temperature.

  3. Eye safe single aperture laser radar scanners for 3D acquisition

    NASA Astrophysics Data System (ADS)

    Starodubov, D.; McCormick, K.; Nolan, P.; Volfson, L.; Finegan, T. M.

    2016-05-01

    The single aperture implementation of laser radars in combination with beam scanning solutions enables low cost, compact and efficient laser systems for 3D acquisition. The design benefits include the lack of dead zones, improved stability and compact footprint for the system implementation. In our presentation we focus on the scanning solution development for 3D laser radars that is based on all solid state magneto-optic design. The novel solid-state scanner implementation results are presented.

  4. Lidar-radar velocimetry using a pulse-to-pulse coherent rf-modulated Q-switched laser.

    PubMed

    Vallet, M; Barreaux, J; Romanelli, M; Pillet, G; Thévenin, J; Wang, L; Brunel, M

    2013-08-01

    An rf-modulated pulse train from a passively Q-switched Nd:YAG laser has been generated using an extra-cavity acousto-optic modulator. The rf modulation reproduces the spectral quality of the local oscillator. It leads to a high pulse-to-pulse phase coherence, i.e., phase memory, over thousands of pulses. The potentialities of this transmitter for lidar-radar are demonstrated by performing Doppler velocimetry on indoor moving targets. The experimental results are in good agreement with a model based on elementary signal processing theory. In particular, we show experimentally and theoretically that lidar-radar is a promising technique that allows discrimination between translation and rotation movements. Being independent of the laser internal dynamics, this scheme can be applied to any Q-switched laser.

  5. Total internal reflection laser tools and methods

    DOEpatents

    Zediker, Mark S.; Faircloth, Brian O.; Kolachalam, Sharath K.; Grubb, Daryl L.

    2016-02-02

    There is provided high power laser tools and laser heads that utilize total internal reflection ("TIR") structures to direct the laser beam along a laser beam path within the TIR structure. The TIR structures may be a TIR prism having its hypotenuse as a TIR surface.

  6. Data collection and simulation of high range resolution laser radar for surface mine detection

    NASA Astrophysics Data System (ADS)

    Steinvall, Ove; Chevalier, Tomas; Larsson, Håkan

    2006-05-01

    Rapid and efficient detection of surface mines, IED's (Improvised Explosive Devices) and UXO (Unexploded Ordnance) is of high priority in military conflicts. High range resolution laser radars combined with passive hyper/multispectral sensors offer an interesting concept to help solving this problem. This paper reports on laser radar data collection of various surface mines in different types of terrain. In order to evaluate the capability of 3D imaging for detecting and classifying the objects of interest a scanning laser radar was used to scan mines and surrounding terrain with high angular and range resolution. These data were then fed into a laser radar model capable of generating range waveforms for a variety of system parameters and combinations of different targets and backgrounds. We can thus simulate a potential system by down sampling to relevant pixel sizes and laser/receiver characteristics. Data, simulations and examples will be presented.

  7. Simulation and analysis about noisy range images of laser radar

    NASA Astrophysics Data System (ADS)

    Zhao, Mingbo; He, Jun; Fu, Qiang; Xi, Dan

    2011-06-01

    A measured range image of imaging laser radar (ladar) is usually disturbed by dropouts and outliers. For the difficulty of obtaining measured data and controlling noise level of dropouts and outliers, a new simulation method for range image with noise is proposed. Based on the noise formation mechanism of ladar range image, an accurate ladar range imaging model is formulated, including three major influencing factors: speckle, atmospheric turbulence and receiver noise. The noisy range images under different scenarios are obtained using MATLABTM. Analysis on simulation results reveals that: (1) Despite of detection strategy, the speckle, the atmospheric turbulence and the receiver noise are major factors which cause dropouts and outliers. (2) The receiver noise itself has limited effect on outliers. However, if other factors (speckle, atmospheric turbulence, etc.) also exist, the effect will be sharply enhanced. (3) Both dropouts and outliers exist in background and target regions.

  8. Fiber optic coherent laser radar 3D vision system

    SciTech Connect

    Clark, R.B.; Gallman, P.G.; Slotwinski, A.R.; Wagner, K.; Weaver, S.; Xu, Jieping

    1996-12-31

    This CLVS will provide a substantial advance in high speed computer vision performance to support robotic Environmental Management (EM) operations. This 3D system employs a compact fiber optic based scanner and operator at a 128 x 128 pixel frame at one frame per second with a range resolution of 1 mm over its 1.5 meter working range. Using acousto-optic deflectors, the scanner is completely randomly addressable. This can provide live 3D monitoring for situations where it is necessary to update once per second. This can be used for decontamination and decommissioning operations in which robotic systems are altering the scene such as in waste removal, surface scarafacing, or equipment disassembly and removal. The fiber- optic coherent laser radar based system is immune to variations in lighting, color, or surface shading, which have plagued the reliability of existing 3D vision systems, while providing substantially superior range resolution.

  9. Radar and Laser Sensors for High Frequency Ocean Wave Measurement.

    NASA Astrophysics Data System (ADS)

    Kennedy, C. R.

    2016-02-01

    Experimental measurement of air-sea fluxes invariably take place using shipbourne instrumentation and simultaneous measurement of wave height and direction is desired. A number of researchers have shown that range measuring sensors combined with inertial motion compensation can be successful on board stationary or very slowly moving ships. In order to measure wave characteristics from ships moving at moderate to full speed the sensors are required to operate at higher frequency so as to overcome the Doppler shift caused by ship motion. This work presents results from some preliminary testing of laser, radar and ultrasonic range sensors in the laboratory and on board ship. The characteristics of the individual sensors are discussed and comparison of the wave spectra produced by each is presented.

  10. Probability of acquisition of three-dimensional imaging laser radar

    NASA Astrophysics Data System (ADS)

    Dong, Li-jun; Zhu, Shao-lan; Sun, Chuan-dong; Gao, Cun-xiao; Song, Zhi-yuan

    2011-06-01

    Three-dimensional imaging laser radar (3-D ladar) is widely used in area of modern military, scientific research, agriculture and industry. Because of its many features such as angle-angle-range capturing, high resolution, anti-jamming ability and no multipath effect ,but it has to scan for target searching, acquiring and tracking. This paper presents a novel probability model of target acquiring which provides a theoretical basis for optimizing the scanning mechanism. The model combines space and time, target moving velocity and ladar scanning velocity together. Then the optimum scanning mechanism to obtain the maximum probability of acquisition and associated with different targets can be gained. The result shows that this model provides a method to optimize parameter for designing of the scanner.

  11. Development of Coherent Laser Radar for Space Situational Awareness Applications

    NASA Astrophysics Data System (ADS)

    Prasad, N.; DiMarcantonio, A.

    2013-09-01

    NASA Langley Research Center (LaRC) is working on an innovative and high performance mobile coherent laser radar (ladar) system known as ExoSPEAR for space situational awareness applications in LEO and beyond. Based on continuously agile pulse doublet technology, the 100 W, nanosecond class, near-IR laser based coherent ladar is being developed for short dwell time measurements of resident space objects (RSOs). ExoSPEAR system is designed to provide rapid and precision tracking of RSOs over very long ranges. The goal is to demonstrate mm-class range resolution, mm/s class velocity resolution and microrad angular resolution with significantly reduced error-covariance in track accuracy. Precise orbit determination would help in advancing functionality of early warning systems for tracking uncooperative targets for planetary protection applications. Furthermore, improvements in resolution of micromotion measurements would enhance our understanding of astrodymanical properties of resident space objects. In this paper, salient features of the evolution and current experimental status of ExoSPEAR ladar architecture will be discussed. Performance simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar power aperture product will be presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits will be analyzed.

  12. LASERS IN THE UK, PART I: THE ROYAL RADAR ESTABLISHMENT (RRE), GREAT MALVERN, WORCESTERSHIRE.

    DTIC Science & Technology

    Solid state laser research and development at the Royal Radar Establishment is described. Particular attention is devoted to new crystalline ... materials . Measurement of photon density fluctuation in coherent source is also reported. (Author)

  13. Saturated semiconductor optical amplifier phase modulation for long range laser radar applications.

    PubMed

    Carns, Jennifer L; Duncan, Bradley D; Dierking, Matthew P

    2012-08-20

    We investigate the use of a semiconductor optical amplifier operated in the saturation regime as a phase modulator for long range laser radar applications. The nature of the phase and amplitude modulation resulting from a high peak power Gaussian pulse, and the impact this has on the ideal pulse response of a laser radar system, is explored. We also present results of a proof-of-concept laboratory demonstration using phase-modulated pulses to interrogate a stationary target.

  14. HI-CLASS on AEOS: A Large Aperture Laser Radar for Space Surveillance/ Situational Awareness Investigations

    DTIC Science & Technology

    2010-11-01

    the ALVA (Applications of Lidars for Vehicles with Analysis) program installed in late 2000 a wideband, 12J, 15Hz CO2 laser radar (ladar) on the 3.67...representative data, and current status of pulsed high-power coherent CO2 laser radar systems at MSSS. The paper reviews the first generation kilowatt...Chemical-biological detection, such as Doppler Shift Scanning Differential Absorption Lidar (DSS DIAL) and remote sensing data 6) Field Ladar tactical

  15. Spectral analysis, digital integration, and measurement of low backscatter in coherent laser radar

    NASA Technical Reports Server (NTRS)

    Vaughan, J. M.; Callan, R. D.; Bowdle, D. A.; Rothermel, J.

    1989-01-01

    A method of surface acoustic wave (SAW) spectral analysis and digital integration that has been used previously in coherent CW laser work with CO2 lasers at 10.6 microns is described. Expressions are derived for the signal to noise ratio in the measured voltage spectrum with an approximation for the general case and rigorous treatment for the low signal case. The atmospheric backscatter data accumulated by the airborne LATAS (laser true airspeed) coherent laser radar system are analyzed.

  16. Lasers '92; Proceedings of the International Conference on Lasers and Applications, 15th, Houston, TX, Dec. 7-10, 1992

    NASA Technical Reports Server (NTRS)

    Wang, Charles P. (Editor)

    1993-01-01

    Papers from the conference are presented, and the topics covered include the following: x-ray lasers, excimer lasers, chemical lasers, high power lasers, blue-green lasers, dye lasers, solid state lasers, semiconductor lasers, gas and discharge lasers, carbon dioxide lasers, ultrafast phenomena, nonlinear optics, quantum optics, dynamic gratings and wave mixing, laser radar, lasers in medicine, optical filters and laser communication, optical techniques and instruments, laser material interaction, and industrial and manufacturing applications.

  17. Lasers '92; Proceedings of the International Conference on Lasers and Applications, 15th, Houston, TX, Dec. 7-10, 1992

    NASA Technical Reports Server (NTRS)

    Wang, Charles P. (Editor)

    1993-01-01

    Papers from the conference are presented, and the topics covered include the following: x-ray lasers, excimer lasers, chemical lasers, high power lasers, blue-green lasers, dye lasers, solid state lasers, semiconductor lasers, gas and discharge lasers, carbon dioxide lasers, ultrafast phenomena, nonlinear optics, quantum optics, dynamic gratings and wave mixing, laser radar, lasers in medicine, optical filters and laser communication, optical techniques and instruments, laser material interaction, and industrial and manufacturing applications.

  18. Ultraviolet lasers. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Mauk, S. C.

    1980-01-01

    Reports cited from the international literature describe various aspects of ultraviolet lasers including laser output, far ultraviolet radiation, electron pumping, optical pumping, and laser materials. Gas lasers, pulsed lasers, dye lasers, CO2 lasers, xenon fluoride lasers, and transversely excited atmospheric (TEA) lasers are considered. This updated bibliography contains 283 citations, 66 of which are new additions to the previous edition.

  19. Registration of partially overlapping laser-radar range images

    NASA Astrophysics Data System (ADS)

    Lv, Dan; Sun, Jian-Feng; Li, Qi; Wang, Qi

    2015-10-01

    To register partially overlapping three-dimensional point sets from different viewpoints, it is necessary to remove spurious corresponding point pairs that are not located in overlapping regions. Most variants of the iterative closest point (ICP) algorithm require users to manually select the rejection parameters for discarding spurious point pairs between the registering views. This requirement often results in unreliable and inaccurate registration. To overcome this problem, we present an improved ICP algorithm that can automatically determine the rejection percentage to reliably and accurately align partially overlapping laser-radar (ladar) range images. The similarity of k neighboring features of each nonplanar point is employed to determine reasonable point pairs in nonplanar regions, and the distance measurement method is used to find reasonable point pairs in planar regions. The rejection percentage can be obtained from these two sets of reasonable pairs. The performance of our algorithm is compared with that of five other algorithms using various models with low and high curvatures. The experimental results show that our algorithm is more accurate and robust than the other algorithms.

  20. A 16-channel CMOS preamplifier for laser ranging radar receivers

    NASA Astrophysics Data System (ADS)

    Liu, Ru-qing; Zhu, Jing-guo; Jiang, Yan; Li, Meng-lin; Li, Feng

    2015-10-01

    A 16-channal front-end preamplifier array has been design in a 0.18um CMOS process for pulse Laser ranging radar receiver. This front-end preamplifier array incorporates transimpedance amplifiers(TIAs) and differential voltage post-amplifier(PAMP),band gap reference and other interface circuits. In the circuit design, the regulated cascade (RGC) input stage, Cherry-Hooper and active inductor peaking were employed to enhance the bandwidth. And in the layout design, by applying the layout isolation structure combined with P+ guard-ring(PGR), N+ guard-ring(NGR),and deep-n-well(DNW) for amplifier array, the crosstalk and the substrate noise coupling was reduced effectively. The simulations show that a single channel receiver front-end preamplifier achieves 95 dBΩ transimpedance gain and 600MHz bandwidth for 3 PF photodiode capacitance. The total power of 16-channel front-end amplifier array is about 800mW for 1.8V supply.

  1. Applications of Tunable Lasers to Laser Radar and 3D Imaging.

    DTIC Science & Technology

    2007-11-02

    The resulting form for U(z) is elliptical in shape: U(z) = &nf(a) cot2a^a2 sin2a - z2 for |z|<|ösina| . (21) This result is intuitive because...the range-resolved laser radar cross section of a disk is proportional to the length of the straight-line integration path, which varies elliptically ...autocorrelation functions of real quantities are even functions, the replicated U(z) curves on either side of the origin are mirror images of each other. If the

  2. An overview of avalanche photodiodes and pulsed lasers as they are used in 3D laser radar type applications

    NASA Astrophysics Data System (ADS)

    Dion, Bruno; Bertone, Nick

    2004-08-01

    This paper will examine how Avalanche Photodiodes (APD) and Infrared Pulsed lasers (PL) are used and optimized to provide the "intelligence" to smart weapons. The basics of APD's and PL will be covered and the principle "time of flight ranging" which is the underlining principle of 3D laser radar will be illustrated. The time of flight principle is used for range finding, lidar, 3D laser radar and speed measurements - this information can then be used to provide intelligence to the smart weapon. Examples of such systems are discussed and illustrated, for example: Cluster bombs, Proximity fuses, and how laser range finding systems can be incorporated with GPS to produce effective and lethal weapons. The APD's that are discussed include silicon APD's for cost effective weapons, and 1550nm APDs for eye-safe systems. An overview of the different PL's will be outlined, but the focus will be on 905nm laser pulsars for cost effective laser weapons.

  3. Multiple-return laser radar for three-dimensional imaging through obscurations.

    PubMed

    Schilling, Bradley W; Barr, Dallas N; Templeton, Glen C; Mizerka, Lawrence J; Trussell, C Ward

    2002-05-20

    A compact imaging laser radar was constructed and tested to investigate phenomenological issues in targeting, especially cases involving imaging through obscurations such as foliage and camouflage netting. The laser radar employs a Nd:YAG microchip laser that operates at a wavelength of 1.06 microm and produces pulses of 1.2-ns duration at a 3-kHz rate. The detector is a commercial indium gallium arsenide avalanche photodiode. A single computer controls the scanning mirrors and performs the digitization of the returning signal at 2 giga samples/s. A detailed description of the laser radar is presented as well as results from field experiments that examined its range accuracy capability and its ability to image a target through camouflage. Results of data collected from deciduous tree lines are also discussed to characterize the presence and quantity of multiple returns.

  4. Terahertz inverse synthetic aperture radar imaging using self-mixing interferometry with a quantum cascade laser.

    PubMed

    Lui, H S; Taimre, T; Bertling, K; Lim, Y L; Dean, P; Khanna, S P; Lachab, M; Valavanis, A; Indjin, D; Linfield, E H; Davies, A G; Rakić, A D

    2014-05-01

    We propose a terahertz (THz)-frequency synthetic aperture radar imaging technique based on self-mixing (SM) interferometry, using a quantum cascade laser. A signal processing method is employed which extracts and exploits the radar-related information contained in the SM signals, enabling the creation of THz images with improved spatial resolution. We demonstrate this by imaging a standard resolution test target, achieving resolution beyond the diffraction limit.

  5. Use of laser radar imagery in optical pattern recognition: the Optical Processor Enhanced Ladar (OPEL) Program

    NASA Astrophysics Data System (ADS)

    Goldstein, Dennis H.; Mills, Stuart A.; Dydyk, Robert B.

    1998-03-01

    The Optical Processor Enhanced Ladar (OPEL) program is designed to evaluate the capabilities of a seeker obtained by integrating two state-of-the-art technologies, laser radar, or ladar, and optical correlation. The program is a thirty-two month effort to build, optimize, and test a breadboard seeker system (the OPEL System) that incorporates these two promising technologies. Laser radars produce both range and intensity image information. Use of this information in an optical correlator is described. A correlator with binary phase input and ternary amplitude and phase filter capability is assumed. Laser radar imagery was collected on five targets over 360 degrees of azimuth from 3 elevation angles. This imagery was then processed to provide training sets in preparation for filter construction. This paper reviews the ladar and optical correlator technologies used, outlines the OPEL program, and describes the OPEL system.

  6. High-frequency scannerless imaging laser radar for industrial inspection and measurement applications

    SciTech Connect

    Schmitt, R.L.; Williams, R.J.; Matthews, J.D.

    1996-11-01

    This report describes the development and testing of a high-frequency scannerless imaging laser radar system to evaluate its viability as an industrial inspection and measurement sensor. We modified an existing 5.5-Mhz scannerless laser radar to operate at 150 Mhz, and measured its performance including its spatial resolution and range resolution. We also developed new algorithms that allow rapid data reduction with improved range resolution. The resulting 150-Mhz ladar system demonstrated a range resolution of better than 3 mm, which represents nearly a factor-of-100 improvement in range resolution over the existing scannerless laser radar system. Based on this work, we believe that a scannerless range imager with 1- to 2-mm range resolution is feasible. This work was performed as part of a small-business CRADA between Sandia National Laboratories and Perceptron, Inc.

  7. Active laser radar (lidar) for measurement of corresponding height and reflectance images

    NASA Astrophysics Data System (ADS)

    Froehlich, Christoph; Mettenleiter, M.; Haertl, F.

    1997-08-01

    For the survey and inspection of environmental objects, a non-tactile, robust and precise imaging of height and depth is the basis sensor technology. For visual inspection,surface classification, and documentation purposes, however, additional information concerning reflectance of measured objects is necessary. High-speed acquisition of both geometric and visual information is achieved by means of an active laser radar, supporting consistent 3D height and 2D reflectance images. The laser radar is an optical-wavelength system, and is comparable to devices built by ERIM, Odetics, and Perceptron, measuring the range between sensor and target surfaces as well as the reflectance of the target surface, which corresponds to the magnitude of the back scattered laser energy. In contrast to these range sensing devices, the laser radar under consideration is designed for high speed and precise operation in both indoor and outdoor environments, emitting a minimum of near-IR laser energy. It integrates a laser range measurement system and a mechanical deflection system for 3D environmental measurements. This paper reports on design details of the laser radar for surface inspection tasks. It outlines the performance requirements and introduces the measurement principle. The hardware design, including the main modules, such as the laser head, the high frequency unit, the laser beam deflection system, and the digital signal processing unit are discussed.the signal processing unit consists of dedicated signal processors for real-time sensor data preprocessing as well as a sensor computer for high-level image analysis and feature extraction. The paper focuses on performance data of the system, including noise, drift over time, precision, and accuracy with measurements. It discuses the influences of ambient light, surface material of the target, and ambient temperature for range accuracy and range precision. Furthermore, experimental results from inspection of buildings, monuments

  8. Self-contained eye-safe laser radar using an erbium-doped fiber laser

    NASA Astrophysics Data System (ADS)

    Driscoll, Thomas A.; Radecki, Dan J.; Tindal, Nan E.; Corriveau, John P.; Denman, Richard

    2003-07-01

    An Eye-safe Laser Radar has been developed under White Sands Missile Range sponsorship. The SEAL system, the Self-contained Eyesafe Autonomous Laser system, is designed to measure target position within a 0.5 meter box. Targets are augmented with Scotchlite for ranging out to 6 km and augmented with a retroreflector for targets out to 20 km. The data latency is less than 1.5 ms, and the position update rate is 1 kHz. The system is air-cooled, contained in a single 200-lb, 6-cubic-foot box, and uses less than 600 watts of prime power. The angle-angle-range data will be used to measure target dynamics and to control a tracking mount. The optical system is built around a diode-pumped, erbium-doped fiber laser rated at 1.5 watts average power at 10 kHz repetition rate with 25 nsec pulse duration. An 8 inch-diameter, F/2.84 telescope is relayed to a quadrant detector at F/0.85 giving a 5 mrad field of view. Two detectors have been evaluated, a Germanium PIN diode and an Intevac TE-IPD. The receiver electronics uses a DSP network of 6 SHARC processors to implement ranging and angle error algorithms along with an Optical AGC, including beam divergence/FOV control loops.Laboratory measurements of the laser characteristics, and system range and angle accuracies will be compared to simulations. Field measurements against actual targets will be presented.

  9. The Precision Expandable Radar Calibration Sphere (PERCS) With Applications for Laser Imaging and Ranging

    NASA Astrophysics Data System (ADS)

    Bernhardt, P.; Nicholas, A.; Thomas, L.; Davis, M.; Hoberman, C.; Davis, M.

    The Naval Research Laboratory will provide an orbiting calibration sphere to be used with ground-based laser imaging telescopes and HF radio systems. The Precision Expandable Radar Calibration Sphere (PERCS) is a practical, reliable, high-performance HF calibration sphere and laser imaging target to orbit at about 600 km altitude. The sphere will be made of a spherical wire frame with aspect independent radar cross section in the 3 to 35 MHz frequency range. The necessary launch vehicle to place the PERCS in orbit will be provided by the Department of Defense Space Test Program. The expandable calibration target has a stowed diameter of 1 meter and a fully deployed diameter of 10.2 meters. A separate deployment mechanism is provided for the sphere. After deployment, the Precision Expandable Radar Calibration Sphere (PERCS) with 180 vertices will be in a high inclination orbit to scatter radio pulses from a number of ground systems, including (1) over-the-horizon (OTH) radars operated by the United States and Australia; (2) high power HF facilities such as HAARP in Alaska, EISCAT in Norway, and Arecibo in Puerto Rico; (3) the chain of high latitude SuperDARN radars used for auroral region mapping; and (4) HF direction finding for Navy ships. With the PERCS satellite, the accuracy of HF radars can be periodically checked for range, elevation, and azimuth errors. In addition, each of the 360 vertices on the PERCS sphere will support an optical retro-reflector for operations with ground laser facilities used to track satellites. The ground laser systems will be used to measure the precise location of the sphere within one cm accuracy and will provide the spatial orientation of the sphere as well as the rotation rate. The Department of Defense facilities that can use the corner-cube reflectors on the PERCS include (1) the Air Force Maui Optical Site (AMOS), (2) the Starfire Optical Range (SOR), and (3) the NRL Optical Test Facility (OTF).

  10. [The error analysis and experimental verification of laser radar spectrum detection and terahertz time domain spectroscopy].

    PubMed

    Liu, Wen-Tao; Li, Jing-Wen; Sun, Zhi-Hui

    2010-03-01

    Terahertz waves (THz, T-ray) lie between far-infrared and microwave in electromagnetic spectrum with frequency from 0.1 to 10 THz. Many chemical agent explosives show characteristic spectral features in the terahertz. Compared with conventional methods of detecting a variety of threats, such as weapons and chemical agent, THz radiation is low frequency and non-ionizing, and does not give rise to safety concerns. The present paper summarizes the latest progress in the application of terahertz time domain spectroscopy (THz-TDS) to chemical agent explosives. A kind of device on laser radar detecting and real time spectrum measuring was designed which measures the laser spectrum on the bases of Fourier optics and optical signal processing. Wedge interferometer was used as the beam splitter to wipe off the background light and detect the laser and measure the spectrum. The result indicates that 10 ns laser radar pulse can be detected and many factors affecting experiments are also introduced. The combination of laser radar spectrum detecting, THz-TDS, modern pattern recognition and signal processing technology is the developing trend of remote detection for chemical agent explosives.

  11. A fast 3D image simulation algorithm of moving target for scanning laser radar

    NASA Astrophysics Data System (ADS)

    Li, Jicheng; Shi, Zhiguang; Chen, Xiao; Chen, Dong

    2014-10-01

    Scanning Laser Radar has been widely used in many military and civil areas. Usually there are relative movements between the target and the radar, so the moving target image modeling and simulation is an important research content in the field of signal processing and system design of scan-imaging laser radar. In order to improve the simulation speed and hold the accuracy of the image simulation simultaneously, a novel fast simulation algorithm is proposed in this paper. Firstly, for moving target or varying scene, an inequation that can judge the intersection relations between the pixel and target bins is obtained by deriving the projection of target motion trajectories on the image plane. Then, by utilizing the time subdivision and approximate treatments, the potential intersection relations of pixel and target bins are determined. Finally, the goal of reducing the number of intersection operations could be achieved by testing all the potential relations and finding which of them is real intersection. To test the method's performance, we perform computer simulations of both the new proposed algorithm and a literature's algorithm for six targets. The simulation results show that the two algorithm yield the same imaging result, whereas the number of intersection operations of former is equivalent to only 1% of the latter, and the calculation efficiency increases a hundredfold. The novel simulation acceleration idea can be applied extensively in other more complex application environments and provide equally acceleration effect. It is very suitable for the case to produce a great large number of laser radar images.

  12. Frustrated total internal reflection of laser eigenstates

    SciTech Connect

    Balcou, P.; Dutriaux, L.; Bretenaker, F.; Le Floch, A.

    1996-07-01

    The role of frustrated total internal reflection in the dynamics of laser eigenstates is investigated theoretically and experimentally. We first derive the Jones matrix of a frustrating element for a realistic Gaussian beam in a single-pass geometry. We point out the existence of three different angular regimes, namely, a pure frustration regime, an intermediate regime, and a quasi-Fabry{endash}Perot regime. We then explore in each case the nature and the competition between the laser polarization eigenstates. A novel spiraling behavior of the laser parameters is demonstrated when the frustrating gap is varied, along with puzzling polarization-flipping effects, that may modify strongly the conditions that optimize the laser-output power. Experimental results agree with a theoretical model. {copyright} {ital 1996 Optical Society of America.}

  13. Linear FMCW Laser Radar for Precision Range and Vector Velocity Measurements

    NASA Technical Reports Server (NTRS)

    Pierrottet, Diego; Amzajerdian, Farzin; Petway, Larry; Barnes, Bruce; Lockhard, George; Rubio, Manuel

    2008-01-01

    An all fiber linear frequency modulated continuous wave (FMCW) coherent laser radar system is under development with a goal to aide NASA s new Space Exploration initiative for manned and robotic missions to the Moon and Mars. By employing a combination of optical heterodyne and linear frequency modulation techniques and utilizing state-of-the-art fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed. Linear FMCW lidar has the capability of high-resolution range measurements, and when configured into a multi-channel receiver system it has the capability of obtaining high precision horizontal and vertical velocity measurements. Precision range and vector velocity data are beneficial to navigating planetary landing pods to the preselected site and achieving autonomous, safe soft-landing. The all-fiber coherent laser radar has several important advantages over more conventional pulsed laser altimeters or range finders. One of the advantages of the coherent laser radar is its ability to measure directly the platform velocity by extracting the Doppler shift generated from the motion, as opposed to time of flight range finders where terrain features such as hills, cliffs, or slopes add error to the velocity measurement. Doppler measurements are about two orders of magnitude more accurate than the velocity estimates obtained by pulsed laser altimeters. In addition, most of the components of the device are efficient and reliable commercial off-the-shelf fiber optic telecommunication components. This paper discusses the design and performance of a second-generation brassboard system under development at NASA Langley Research Center as part of the Autonomous Landing and Hazard Avoidance (ALHAT) project.

  14. Required energy for a laser radar system incorporating a fiber amplifier or an avalanche photodiode

    NASA Astrophysics Data System (ADS)

    Overbeck, Jay A.; Salisbury, Michael S.; Mark, Martin B.; Watson, Edward A.

    1995-11-01

    The transmitted energy required for an airborne laser radar system to be able to image a target at 20 km is investigated. Because direct detection is being considered, two methods of using an avalanche photodiode (APD) as the detector and (2) using a commercial fiber amplifier as a preamplifier before a photodetector. For this analysis a specified signal-to-noise ratio was used in conjunction with the radar range equation, which includes the effects of atmospheric transmission and turbulence. Theoretical analysis reveals that a system with a fiber amplifier performs nearly the same as a system incorporating an APD.

  15. Investigation of laser radar systems based on mid-infrared semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Rybaltowski, Adam

    This dissertation deals with the possibility of utilizing mid-infrared semiconductor lasers in systems of optical remote sensing with range resolution, called laser radar or lidar. The main subject investigated in this dissertation is two-fold: firstly, an analysis of the signal-to-noise ratio (SNR) and related maximum sensing range calculations in this type of lidar based on available system components, and---secondly---improvements in the Random-Modulation Continuous-Wave (RM-CW) lidar technique to better utilize available mid-infrared semiconductor lasers. As far as the SNR analysis is concerned, an appropriate framework has been constructed to analyze post-demodulation noise in mid-infrared direct-detection RM-CW lidar. It is based on a generalization of the Wiener-Khintchine theorem; noise is assumed to be additive, stationary, and have an arbitrary power spectrum. This is in contrast to the SNR analysis in the literature on this subject, which is inadequate for mid-infrared RM-CW lidar as it only considers Poissonian fluctuations of the number of detected photons. In addition to regular SNR analysis, the framework derived in this dissertation allows treatment of singularities such as demodulation with an unbalanced sequence in 1/f noise. To calculate maximum lidar sensing range, the following detection limits have been considered: signal shot noise, background blackbody radiation shot noise based on the Background-Limited Photodetection (BLIP) detectivity limit, and minimum-size detector noise given by diffraction-limited focusing. The latter is found to be of greatest practical interest. Furthermore, a lidar figure of merit has been introduced, and all quantities related to lidar performance and its detection limits have been presented graphically. Since pseudo-random sequences discussed in the literature have been found highly non-optimal for most applications of RM-CW lidar, a framework for the construction of new pseudo-random sequences of desired

  16. Simultaneous rocket and MST radar observation of an internal gravity wave breaking in the mesosphere

    NASA Technical Reports Server (NTRS)

    Smith, S. A.; Fritts, D. C.; Balsley, B. B.; Philbrick, C. R.

    1986-01-01

    In June, 1983, the Structure and Atmospheric Turbulence Environment (STATE) rocket and Poker Flat Mesophere-Stratosphere-Troposphere radar campaign was conducted to measure the interaction between turbulence, electron density and electron density gradient that has produced unusually strong MST radar echoes from the summer mesosphere over Poker Flat, Alaska. Analysis or radar wind measurements and a concurrent wind and temperature profile obtained from a rocket probe carrying a three-axis accelerometer are given. The two data sets provide a fairly complete (and in some cases, redundant) picture of the breaking (or more correctly, the saturation) of a large-amplitude, low-frequency, long-wavelength internal gravity wave. The data show that small-scale turbulence and small-scale wave intensity is greatest at those altitudes where the large-scale wave-induced temperature lapse rate is most negative or most nearly unstable, but the wind shear due to the large-scale wave is a minimum. A brief review of linear gravity-wave theory is presented as an aid to the identification of the gravity-wave signature in the radar and rocket data. Analysis of the time and height cross sections of wind speed and turbulence intensity observed by the Poker Flat MST radar follows. Then, the vertical profile of temperature and winds measured by a rocket probe examined. Finally, the use of the independent data sets provided by the rocket and the radar are discussed and implications for theories of wave saturation are presented.

  17. Synthetic-aperture imaging laser radar: laboratory demonstration and signal processing

    NASA Astrophysics Data System (ADS)

    Beck, Steven M.; Buck, Joseph R.; Buell, Walter F.; Dickinson, Richard P.; Kozlowski, David A.; Marechal, Nicholas J.; Wright, Timothy J.

    2005-12-01

    The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope's aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system.

  18. Synthetic-aperture imaging laser radar: laboratory demonstration and signal processing.

    PubMed

    Beck, Steven M; Buck, Joseph R; Buell, Walter F; Dickinson, Richard P; Kozlowski, David A; Marechal, Nicholas J; Wright, Timothy J

    2005-12-10

    The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope's aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system.

  19. Eighth International Workshop on Laser Ranging Instrumentation

    NASA Technical Reports Server (NTRS)

    Degnan, John J. (Compiler)

    1993-01-01

    The Eighth International Workshop for Laser Ranging Instrumentation was held in Annapolis, Maryland in May 1992, and was sponsored by the NASA Goddard Space Flight Center in Greenbelt, Maryland. The workshop is held once every 2 to 3 years under differing institutional sponsorship and provides a forum for participants to exchange information on the latest developments in satellite and lunar laser ranging hardware, software, science applications, and data analysis techniques. The satellite laser ranging (SLR) technique provides sub-centimeter precision range measurements to artificial satellites and the Moon. The data has application to a wide range of Earth and lunar science issues including precise orbit determination, terrestrial reference frames, geodesy, geodynamics, oceanography, time transfer, lunar dynamics, gravity and relativity.

  20. A high detection probability method for Gm-APD photon counting laser radar

    NASA Astrophysics Data System (ADS)

    Zhang, Zi-jing; Zhao, Yuan; Zhang, Yong; Wu, Long; Su, Jian-zhong

    2013-08-01

    Since Geiger mode Avalanche Photodiode (GmAPD) device was applied in laser radar system, the performance of system has been enhanced due to the ultra-high sensitivity of GmAPD, even responding a single photon. However, the background noise makes ultra-high sensitive GmAPD produce false alarms, which severely impacts on the detection of laser radar system based on Gm-APD and becomes an urgent problem which needs to be solved. To address this problem, a few times accumulated two-GmAPDs strategy is proposed in this paper. Finally, an experimental measurement is made under the background noise in sunny day. The results show a few times accumulated two- GmAPDs strategy can improve the detection probability and reduce the false alarm probability, and obtain a clear 3D image of target.

  1. Adaptive fused Kalman filter based on imaging laser radar for TAN

    NASA Astrophysics Data System (ADS)

    Gong, Junbin; Xu, Hongbo; Tian, Jinwen; Cheng, Hua; Zhang, Jun

    2007-11-01

    Terrain aided navigation (TAN) is an efficient way to periodically correct the error accumulation of INS. The imaging laser radar is an ideal imaging sensor in TAN for the low-flying aircraft and unmanned air vehicles for the high precision multi-dimensional data acquisition capability and concealable attribute. In this paper, a new framework for applying the laser radar to terrain aided navigation is put forward. Then a new adaptive fused Kalman Filter is proposed to improve the accuracy and robustness. At last, the key factors affected the algorithm are analyzed and the comparative experimentations are presented. The simulating experiments show that the proposed algorithm improves the location accuracy, and has good initial error tolerance and fine robustness. It shows that this approach is a valid solution for the application.

  2. Analysis and Modeling of Radar Surface Signatures of Non-Linear Internal Waves

    DTIC Science & Technology

    2008-09-30

    sections of dihedral corner reflectors of various sizes as a function grazing angle. The red curves are HH/VV polarization ratios in dB. The width of...our shipboard data at HH and VV, HH normalized radar cross sections (NRCSs) were not only modulated more by internal waves than VV but also became...that HH NRCS values exceed VV values near the crest of internal waves. We have therefore chosen the simple dihedral corner reflector of Trizna and Lee

  3. HgCdTe photomixers for CO2 laser radar systems

    NASA Technical Reports Server (NTRS)

    Bratt, Peter R.

    1992-01-01

    The Santa Barbara Research Center has developed a variety of high speed HgCdTe photodetectors for use in CO2 laser radar systems. These detectors have outstanding performance and can be made available in production quantities. Many of them have been employed in a variety of systems applications over the past ten years. In this paper, we briefly describe the detector technology, summarize the state-of-the-art, and indicate some practical applications.

  4. Advanced system model for 1574-nm imaging, scannerless, eye-safe laser radar

    NASA Astrophysics Data System (ADS)

    Schael, Ulrich; Rothe, Hendrik

    2002-10-01

    Laser radar based on gated viewing uses narrow laser pulses to illuminate a whole scene for direct (incoherent) detection. Due to the time of flight principle and a very fast shutter with precisely controlled delay time, only light reflected in the range R (range slice ΔR) is detected by a camera. Scattered light which reaches the shutter outside a given exposure time (gate) is suppressed. Hence, it is possible to "look" along the optical axis through changing atmospheric transmissions (rain, haze, fog, snow). For each laser pulse, the grey value image ES(x,y) of the camera is captured by a framegrabber for subsequent evaluation. Image sequences from these laser radar systems are ideally suited to recognize objects, because of the automatic contrast generation of the technology. Difficult object recognition problems, detection, target tracking, or obstacle avoidance at bad weather conditions are favorite applications. In this paper we discuss improvements in the system modelling and simulation of our laser radar system. Formerly the system performance was calculated for the whole system using the signal-to-noise ratio (SNR), leading to a general estimation of the maximum range of target detection. Changing to a pixel oriented approach, we are now able to study the system response for targets with arbitrary two and even three dimensional form. We take into account different kinds of target reflectivity and the Gaussian nature of the illuminating laser spot. Hence it is possible to simulate gray value images (range slices) and calculate range images. This will lead to a modulation transfer function for the system in future. Finally, the theoretical considerations are compared with experimental results from indoor measurements.

  5. Maximum detection range limitation of pulse laser radar with Geiger-mode avalanche photodiode array

    NASA Astrophysics Data System (ADS)

    Luo, Hanjun; Xu, Benlian; Xu, Huigang; Chen, Jingbo; Fu, Yadan

    2015-05-01

    When designing and evaluating the performance of laser radar system, maximum detection range achievable is an essential parameter. The purpose of this paper is to propose a theoretical model of maximum detection range for simulating the Geiger-mode laser radar's ranging performance. Based on the laser radar equation and the requirement of the minimum acceptable detection probability, and assuming the primary electrons triggered by the echo photons obey Poisson statistics, the maximum range theoretical model is established. By using the system design parameters, the influence of five main factors, namely emitted pulse energy, noise, echo position, atmospheric attenuation coefficient, and target reflectivity on the maximum detection range are investigated. The results show that stronger emitted pulse energy, lower noise level, more front echo position in the range gate, higher atmospheric attenuation coefficient, and higher target reflectivity can result in greater maximum detection range. It is also shown that it's important to select the minimum acceptable detection probability, which is equivalent to the system signal-to-noise ratio for producing greater maximum detection range and lower false-alarm probability.

  6. Non-mechanical beam control for entry, descent and landing laser radar (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Stockley, Jay E.; Kluttz, Kelly; Hosting, Lance; Serati, Steve; Bradley, Cullen P.; McManamon, Paul F.; Amzajerdian, Farzin

    2017-05-01

    Laser radar for entry, descent, and landing (EDL) applications as well as the space docking problem could benefit from a low size, weight, and power (SWaP) beam control system. Moreover, an inertia free approach employing non-mechanical beam control is also attractive for laser radar that is intended to be employed aboard space platforms. We are investigating a non-mechanical beam steering (NMBS) sub-system based on liquid crystal polarization grating (LCPG) technology with emphasis placed on improved throughput and significant weight reduction by combining components and drastically reducing substrate thicknesses. In addition to the advantages of non-mechanical, gimbal free beam control, and greatly improved SWaP, our approach also enables wide area scanning using a scalable architecture. An extraterrestrial application entails additional environmental constraints, consequently an environmental test plan tailored to an EDL mission will also be discussed. In addition, we will present advances in continuous fine steering technology which would complement the coarse steering LCPG technology. A low-SWaP, non-mechanical beam control system could be used in many laser radar remote sensing applications including meteorological studies and agricultural or environmental surveys in addition to the entry, descent, and landing application.

  7. Detection probabilities for photon-counting avalanche photodiodes applied to a laser radar system.

    PubMed

    Henriksson, Markus

    2005-08-20

    Arrays of photon-counting avalanche photodiodes with time-resolved readout can improve the performance of three-dimensional laser radars. A comparison of the detection and false-alarm probabilities for detectors in linear mode and in Geiger mode is shown. With low background radiation their performance is comparable. It is shown that in both cases it will be necessary to process several laser shots of the same scene to improve detection and reduce the false-alarm rate. Additional calculations show that the linear mode detector is much better at detecting targets behind semitransparent obscurations such as vegetation and camouflage nets.

  8. Comparing helicopter-borne profiling radar with airborne laser scanner data for forest structure estimation.

    NASA Astrophysics Data System (ADS)

    Piermattei, Livia; Hollaus, Markus; Pfeifer, Norbert; Chen, Yuwei; Karjalainen, Mika; Hakala, Teemu; Hyyppä, Juha; Wagner, Wolfgang

    2017-04-01

    Forests are complex ecosystems that show substantial variation with respect to climate, management regime, stand history, disturbance, and needs of local communities. The dynamic processes of growth and disturbance are reflected in the structural components of forests that include the canopy vertical structure and geometry (e.g. size, height, and form), tree position and species diversity. Current remote-sensing systems to measure forest structural attributes include passive optical sensors and active sensors. The technological capabilities of active remote sensing like the ability to penetrate the vegetation and provide information about its vertical structure has promoted an extensive use of LiDAR (Light Detection And Ranging) and radar (RAdio Detection And Ranging) system over the last 20 years. LiDAR measurements from aircraft (airborne laser scanning, ALS) currently represents the primary data source for three-dimensional information on forest vertical structure. Contrary, despite the potential of radar remote sensing, their use is not yet established in forest monitoring. In order to better understand the interaction of pulsed radar with the forest canopy, and to increase the feasibility of this system, the Finnish Geospatial Research Institute has developed a helicopter-borne profiling radar system, called TomoRadar. TomoRadar is capable of recording a canopy-penetrating profile of forests. To georeference the radar measurements the system was equipped with a global navigation satellite system and an inertial measurement unit with a centimeter level accuracy of the flight trajectory. The TomoRadar operates at Ku-band, (wave lengths λ 1.5cm) with two separated parabolic antennas providing co- and cross-polarization modes. The purpose of this work is to investigate the capability of the TomoRadar system, for estimating the forest vertical profile, terrain topography and tree height. We analysed 600 m TomoRadar crosspolarized (i.e. horizontal - vertical

  9. Lasers '83. Proceedings of the international conference

    SciTech Connect

    Powell, R.C.

    1985-01-01

    Among the topics discussed are the development history of the semiconductor diode laser, laser material processing, nonlinear spectroscopy, recent advancements in diode lasers, laser-driven particle accelerators, laser applications in the atmospheric sciences, laser-assisted collisions, novel (garnet and alexandrite) solid state laser materials, IR molecular lasers, devices and components for fiber-optic communications, free-electron lasers and masers, and picosecond optical phenomena. Also covered are laser-stimulated materials surface processes, color center laser developments, blue-green and metal vapor lasers, laser chemistry, nonlinear effects, high energy lasers, excimer lasers, laser trapping of ions, optical cavities and propagation, laser isotope separation, laser trapping of atoms, laser applications in biochemistry, tunable coherent short wavelength radiation, laser spectroscopy, picosecond studies of condensed phase molecular systems, and combustion and plasma diagnostics.

  10. Compact multichannel receiver using InGaAs APDs for single-pulse eye-safe laser radar imagery

    NASA Astrophysics Data System (ADS)

    Burns, Hoyt N.; Yun, Steven T.; Dinndorf, Kenneth M.; Hayden, David R.

    1997-08-01

    Active imaging laser radars form 3D images which can be processed to provide target identification and precision aimpoint definition in real time. Earlier raster-scanned and pushbroom-scanned 3D imaging laser radar receivers required multiple laser pulses to assemble a complete 3D image frame. Platform/target motion and atmospheric effects caused tearing and jitter in the assembled 3D images, which complicated the subsequent image processing and necessitated the use of stabilized scanning systems. This paper describes the current status of the parallel/multichannel imaging laser radar receiver (PMR) which is being developed under an SBIR Phaser II program by the USAF Wright Laboratories Armament Directorate. The PMR uses an array of multichannel laser radar receivers to form single-pulse, 3D laser radar images, thus eliminating the complex and costly scanning system, and enabling much higher frame rates than were ever before possible. The heart of the PMR is the multichannel optical receiver photonic hybrid (MORPH), a high performance 16-channel laser radar receiver module which uses an array of InGaAs avalanche photodiodes for eyesafe operation. The MORPH provides high downrange resolution, multihit range data for each detector on a compact circuit card. Optical flux is transferred from the receiver focal plane to each MORPH via a fiber optic ribbon cable. An array of MORPHs are plugged into a compact passive backplane, along with a single digital control card (DCC). The DCC, which is the same form factor as the MORPH, synchronizes the MORPHs and transfers the digital range information to the host processor over a standard parallel data interface cable. The system described here illustrates one approach to integrating and packaging high-density photonic arrays and their associated signal processing electronics to yield a compact, low power, scannerless, high performance imaging laser radar receiver, using existing technology.

  11. High-resolution 3D imaging laser radar flight test experiments

    NASA Astrophysics Data System (ADS)

    Marino, Richard M.; Davis, W. R.; Rich, G. C.; McLaughlin, J. L.; Lee, E. I.; Stanley, B. M.; Burnside, J. W.; Rowe, G. S.; Hatch, R. E.; Square, T. E.; Skelly, L. J.; O'Brien, M.; Vasile, A.; Heinrichs, R. M.

    2005-05-01

    Situation awareness and accurate Target Identification (TID) are critical requirements for successful battle management. Ground vehicles can be detected, tracked, and in some cases imaged using airborne or space-borne microwave radar. Obscurants such as camouflage net and/or tree canopy foliage can degrade the performance of such radars. Foliage can be penetrated with long wavelength microwave radar, but generally at the expense of imaging resolution. The goals of the DARPA Jigsaw program include the development and demonstration of high-resolution 3-D imaging laser radar (ladar) ensor technology and systems that can be used from airborne platforms to image and identify military ground vehicles that may be hiding under camouflage or foliage such as tree canopy. With DARPA support, MIT Lincoln Laboratory has developed a rugged and compact 3-D imaging ladar system that has successfully demonstrated the feasibility and utility of this application. The sensor system has been integrated into a UH-1 helicopter for winter and summer flight campaigns. The sensor operates day or night and produces high-resolution 3-D spatial images using short laser pulses and a focal plane array of Geiger-mode avalanche photo-diode (APD) detectors with independent digital time-of-flight counting circuits at each pixel. The sensor technology includes Lincoln Laboratory developments of the microchip laser and novel focal plane arrays. The microchip laser is a passively Q-switched solid-state frequency-doubled Nd:YAG laser transmitting short laser pulses (300 ps FWHM) at 16 kilohertz pulse rate and at 532 nm wavelength. The single photon detection efficiency has been measured to be > 20 % using these 32x32 Silicon Geiger-mode APDs at room temperature. The APD saturates while providing a gain of typically > 106. The pulse out of the detector is used to stop a 500 MHz digital clock register integrated within the focal-plane array at each pixel. Using the detector in this binary response mode

  12. Three-dimensional laser radar for perimeter security

    NASA Astrophysics Data System (ADS)

    Ray, Mark; Evans, Owen; Jamieson, Jim

    2005-10-01

    Goodrich Sensor Systems has developed a Laser Perimeter Awareness System (LPAS) for surveillance that both detects the presence and tracks the motion of intruders, locating them in range, bearing, and elevation with respect to the position of the sensor. The system places graphic symbols representing the intruders onto a map or aerial photo at the appropriate locations. The coordinates of the intruders are available to cue additional sensors, such as thermal imagers, to automatically slew their fields of view toward the intruder for further investigation. Hence, security personnel can assess whether the detected intruder is a person, an animal, or simply a false alarm and take appropriate action. Detection performance as a function of object size is discussed.

  13. An operational theory of laser-radar selenodesy

    USGS Publications Warehouse

    Wildey, R.L.; Schlier, R.E.; Hull, J.A.; Larson, G.

    1967-01-01

    A theory of the utilization of laser techniques for ranging from the Earth to the Moon for the purpose of providing control points on the lunar surface at which the figure of the Moon is measured to an accuracy at least an order of magnitude better than that of the present astrometric measurements is presented. This, in turn, increases the accuracy of the horizontal selenocentric coordinates of topographical features measured by present astrometric methods. The improvement in the vertical and horizontal coordinates of control points in the Apollo landing zone will aid in the analysis of Unmanned Lunar Orbiter photographs for the selection of Apollo landing sites. The present discussion proposes the means of obtaining the ground control upon which the Orbiter photogrammetry is to be fastened. In addition, a technique of combining Goldstone tracking data to show where the resulting lunar figure is positioned relative to the Moon's center of mass is presented. If corner reflectors are placed on the lunar surface, as suggested by many members of the scientific community, or on a lunar orbiting vehicle, one or more Earth-based laser ranging systems are essential. These reflectors will give enough enhancement in return signal to allow for an additional increase in range accuracy of one to two orders of magnitude. In addition to the primary data on the figure of the Moon, a number of other measurements of scientific importance are then readily obtainable. As far as the measurement of control points is concerned, however, the use of corner reflectors is not essential for the success of this project. Questions regarding the influence on the present shape of the Moon of the frozen tide, isostasy, and past impacts of large asteroids appear in large part answerable through the data which are indicated to be obtainable under the present theory. ?? 1967.

  14. Getting to the science quickly and effectively: An international collaboration in community radar software

    NASA Astrophysics Data System (ADS)

    Collis, Scott; Helmus, Jonathan; Heistermann, Maik; Michelson, Daniel

    2015-04-01

    The science of meteorology is full of duplicated effort. Actions such as reading in data, quality control and performing retrievals is repeated across institutions and while the traditional publication process helps in jumpstarting the development process details can be, some times deliberately, vague. Free and open software, specifically community software projects that are open to new contributions can help to alleviate this problem. This presentation will outline a growing international collaboration on the development of software for the reading, processing, retrieval from and output of weather radar data. Developers of the Python ARM Radar Toolkit, the Wradlib software package and the BALTRAD have been collaborating in order to improve the intercompatibility of the contributed code. This effort, coupled with running courses in open source software and sustainable programming practices is aimed at helping users cut through work that has been done before and get to using weather radar data to improve our understanding of the atmosphere and help decision makers make the best use of radar data. This will be an example driven presentation, code will be shown and examples worked through to give the audience a flavor of how work can be done with the various projects.

  15. A New GaAs Laser Radar for Atmospheric Measurements

    NASA Technical Reports Server (NTRS)

    Brown, R. T.; Stoliar, A. P.

    1973-01-01

    A special GaAs lidar using fiber coupled diode lasers was constructed for the purpose of measuring the extinction coefficient distribution within a large atmospheric volume at a rate compatible with atmospheric kinematics. The technique is based on taking backscatter signature ratios over spatial increments after the returns are normalized by pulse integration. Essential aspects of the lidar design are beam pulse power, repetition rate, detection system dynamic range and decay linearity. It was necessary to preclude the possibility of eye hazard under any operating conditions, including directly viewing the emitting aperture at close distance with a night-adapted eye. The electronic signal processing and control circuits were built to allow versatile operations. Extinction coefficient measurements were made in fog and clouds using a low-power laboratory version of the lidar, demonstrating feasibility. Data are presented showing range squared corrected backscatter profiles converted to extinction coefficient profiles, temporal signal fluctuations, and solar induced background noise. These results aided in the design of the lidar which is described. Functional tests of this lidar and the implications relevant to the design of a prototype model are discussed. This work was jointly sponsored by Sperry Rand Corporation under its Independent Research and Development program; the Air Force Avionics Laboratory, Wright Field, Dayton, Ohio; and the Naval Ammunition Depot, Crane, Indiana.

  16. Multihit mode direct-detection laser radar system using a Geiger-mode avalanche photodiode.

    PubMed

    Oh, Min Seok; Kong, Hong Jin; Kim, Tae Hoon; Hong, Keun Ho; Kim, Byung Wook; Park, Dong Jo

    2010-03-01

    In this paper, a direct-detection laser radar system that uses a Geiger-mode avalanche photodiode (GAPD) of relatively short dead time (45 ns) is described. A passively Q-switched microchip laser is used as a laser source and a compact peripheral component interconnect system, which includes a time-to-digital converter (TDC), is set up for fast signal processing. With both the GAPD and the TDC functioning multistop acquisition, the system operates in a multihit mode. The software for the three-dimensional visualization and an algorithm for the removal of noise are developed. It is shown that the single-shot precision of the system is approximately 10 cm (sigma) and the precision is improved by increasing the number of laser pulses to be averaged so that the precision of approximately 1 cm (sigma) was acquired with more than 150 laser pulses scattered from the target. The accuracy of the system is measured to be 12 cm when the energy of the emitted laser pulse varies with a factor of 7.

  17. Intelligent multisensor concept for image-guided 3D object measurement with scanning laser radar

    NASA Astrophysics Data System (ADS)

    Weber, Juergen

    1995-08-01

    This paper presents an intelligent multisensor concept for measuring 3D objects using an image guided laser radar scanner. The field of application are all kinds of industrial inspection and surveillance tasks where it is necessary to detect, measure and recognize 3D objects in distances up to 10 m with high flexibility. Such applications might be the surveillance of security areas or container storages as well as navigation and collision avoidance of autonomous guided vehicles. The multisensor system consists of a standard CCD matrix camera and a 1D laser radar ranger which is mounted to a 2D mirror scanner. With this sensor combination it is possible to acquire gray scale intensity data as well as absolute 3D information. To improve the system performance and flexibility, the intensity data of the scene captured by the camera can be used to focus the measurement of the 3D sensor to relevant areas. The camera guidance of the laser scanner is useful because the acquisition of spatial information is relatively slow compared to the image sensor's ability to snap an image frame in 40 ms. Relevant areas in a scene are located by detecting edges of objects utilizing various image processing algorithms. The complete sensor system is controlled by three microprocessors carrying out the 3D data acquisition, the image processing tasks and the multisensor integration. The paper deals with the details of the multisensor concept. It describes the process of sensor guidance and 3D measurement and presents some practical results of our research.

  18. Multiple target tracking and target attitude determination with a scanning laser radar

    NASA Technical Reports Server (NTRS)

    Flom, T.; Coombes, D.

    1974-01-01

    A scanning laser radar that can acquire and track single or multiple targets has recently been developed. Scan patterns have been designed for acquisition and tracking of one or more targets using a narrow laser beam. A synchronously scanned transmitter-receiver is used to acquire and track targets anywhere in a 376 x 376 element raster covering a 30 x 30 deg field. All scan patterns are electronically programmed, and the system automatically acquires and tracks the target or targets without the aid of an operator. The maximum tracking rate is 1.0 deg/sec (10.0 deg/sec) when used with a 1 kHz (10 kHz) scan rate. The estimated free space range against passive cooperative targets (corner cube reflectors) is 30 nautical miles. The laser radar has an accuracy of 10 cm (range) and 0.05 deg (angle). The developmental system is relatively small (1.5 cu ft), lightweight (60 lbs) and low-power-consuming (60 W).

  19. Comparison of Retracking Algorithms Using Airborne Radar and Laser Altimeter Measurements of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Ferraro, Ellen J.; Swift, Calvin T.

    1995-01-01

    This paper compares four continental ice sheet radar altimeter retracking algorithms using airborne radar and laser altimeter data taken over the Greenland ice sheet in 1991. The refurbished Advanced Application Flight Experiment (AAFE) airborne radar altimeter has a large range window and stores the entire return waveform during flight. Once the return waveforms are retracked, or post-processed to obtain the most accurate altitude measurement possible, they are compared with the high-precision Airborne Oceanographic Lidar (AOL) altimeter measurements. The AAFE waveforms show evidence of varying degrees of both surface and volume scattering from different regions of the Greenland ice sheet. The AOL laser altimeter, however, obtains a return only from the surface of the ice sheet. Retracking altimeter waveforms with a surface scattering model results in a good correlation with the laser measurements in the wet and dry-snow zones, but in the percolation region of the ice sheet, the deviation between the two data sets is large due to the effects of subsurface and volume scattering. The Martin et al model results in a lower bias than the surface scattering model, but still shows an increase in the noise level in the percolation zone. Using an Offset Center of Gravity algorithm to retrack altimeter waveforms results in measurements that are only slightly affected by subsurface and volume scattering and, despite a higher bias, this algorithm works well in all regions of the ice sheet. A cubic spline provides retracked altitudes that agree with AOL measurements over all regions of Greenland. This method is not sensitive to changes in the scattering mechanisms of the ice sheet and it has the lowest noise level and bias of all the retracking methods presented.

  20. Hardware-in-the-loop testing for the LOCAAS laser radar antimateriel munition

    NASA Astrophysics Data System (ADS)

    Byrd, Lawrence Y., III; Thompson, Rhoe A.

    1996-05-01

    The KHILS facility in the Wright Laboratory Armament Directorate at Eglin AFB has developed a hardware-in-the- loop (HWIL) simulation for the Low Cost Autonomous Attack System. Unique techniques have been developed for real-time closed-loop signal injection testing of this Laser Radar (LADAR) guided munition concept. The overall HWIL layout will be described including discussion of interfaces, real- time 3D LADAR scene generation, flight motion simulation, and real-time graphical visualization. In addition, the practical application of a new simulation Verification, Validation and Accreditation procedure will be described in relation to this HWIL simulation.

  1. Active laser radar systems with stochastic electromagnetic beams in turbulent atmosphere.

    PubMed

    Cai, Yangjian; Korotkova, Olga; Eyyuboğlu, Halil T; Baykal, Yahya

    2008-09-29

    Propagation of stochastic electromagnetic beams through paraxial ABCD optical systems operating through turbulent atmosphere is investigated with the help of the ABCD matrices and the generalized Huygens-Fresnel integral. In particular, the analytic formula is derived for the cross-spectral density matrix of an electromagnetic Gaussian Schell-model (EGSM) beam. We applied our analysis for the ABCD system with a single lens located on the propagation path, representing, in a particular case, the unfolded double-pass propagation scenario of active laser radar. Through a number of numerical examples we investigated the effect of local turbulence strength and lens' parameters on spectral, coherence and polarization properties of the EGSM beam.

  2. Radiation effects on optical components of a laser radar sensor designed for remote metrology in ITER

    SciTech Connect

    Menon, M.M.; Grann, E.B.; Slotwinski, A.

    1997-09-01

    A frequency modulated laser radar is being developed for in-vessel metrology and viewing of plasma-facing surfaces. Some optical components of this sensor must withstand intense gamma radiation (3 {times} 10{sup 6} rad/h) during operation. The authors have tested the effect of radiation on a silica core polarization maintaining optical fiber and on TeO{sub 2} crystals at doses up to {approximately} 10{sup 9} rad. Additional tests are planned for evaluating the performance of a complete acousto-optic (AO) scanning device. The progress made in these tests is also described.

  3. OWL: an eyesafe 1.5-μm laser radar system for military applications

    NASA Astrophysics Data System (ADS)

    Eibert, Max; Scherbarth, Stefan

    1998-10-01

    The paper reports on current advances in the development of the Dornier Obstacle Warning System (OWS) for helicopters, with particular emphasis on the Obstacle Warning Ladar (OWL). Here both segments, development and application of the 1.5 micrometer imaging laser radar (LADAR) will be represented. It will be shown how advances in the eyesafe LADAR technology resulted in Obstacle Warning Ladar optimized for wire detection leading to a system family platform covering the range from the commercial needs up to the military requirements.

  4. Signal-to-noise ratio in squeezed-light laser radar.

    PubMed

    Rubin, Mark A; Kaushik, Sumanth

    2009-08-10

    The formalism for computing the signal-to-noise ratio (SNR) for laser radar is reviewed and applied to the tasks of target detection, direction finding, and phase-change estimation with squeezed light. The SNR for heterodyne detection of coherent light using a squeezed local oscillator is lower than that obtained using a coherent local oscillator. This is true for target detection, for phase estimation, and for direction finding with a split detector. Squeezing the local oscillator also lowers SNR in balanced homodyne and heterodyne detection of coherent light. Loss places an upper bound on the improvement that squeezing can bring to direct-detection SNR.

  5. Single-frequency mid-infrared optical parametric oscillator source for coherent laser radar.

    PubMed

    Hanson, F; Poirier, P; Arbore, M A

    2001-11-15

    We report on the design and characterization of a highly coherent mid-IR source at 3.57mum based on a single-frequency optical parametric oscillator. Detailed frequency and amplitude noise spectra have been measured. The rms intensity noise from 1.2 to 1000 Hz was 0.03%, and a rms frequency drift of 8 kHz in 1 ms was observed. We have also demonstrated the utility of this source for coherent laser radar applications by measuring micro-Doppler spectra from vibrating targets.

  6. US Integrated Ocean Observing System HF Radar Network: National Applications and International Implementation

    NASA Astrophysics Data System (ADS)

    Harlan, J.

    2016-12-01

    The US Integrated Ocean Observing System (IOOS), a partnership of academic institutions and Federal agencies, within NOAA National Ocean Service (NOS), operates the nation's only high-frequency (HF) radar network providing near-real-time 2-D maps of ocean of surface currents speed and direction. This system supports US Coast Guard search and rescue operations, NOAA response to oil spills, port navigation and tracking of harmful algal bloom. In the research realm, the data are helping to understand oceanographic processes such as the warm water mass off of the west coast of the US and are routinely ingested into oceanographic models and are used for research into tsunami detection. A key component of the network is the data management system that ingests and distributes hourly data from radars throughout US coastal areas as well as Canada and Mexico, comprising nearly 150 radars. HF radar operators outside the US have adopted the data file formats that were developed by the US IOOS and these data are displayed publicly in near-real-time. To enhance the utility of HF radar data to end-users in all parts of the globe, operational products are needed. Recently in the US, quasi-operational products have been developed, or are under development, including: 2-D maps in AWIPS-II, tidal analysis and prediction from NOS Center for Operational Oceanographic Products & Services (CO-OPS), tsunami detection algorithms led by National Tsunami Warning Center, and significant wave height pilot project. These products will be highlighted and potential for international use discussed.

  7. Middle Atmosphere Program. Handbook for MAP. Volume 30: International School on Atmospheric Radar

    NASA Technical Reports Server (NTRS)

    Fukao, Shoichiro (Editor)

    1989-01-01

    Broad, tutorial coverage is given to the technical and scientific aspects of mesosphere stratosphere troposphere (MST) meteorological radar systems. Control issues, signal processing, atmospheric waves, the historical aspects of radar atmospheric dynamics, incoherent scatter radars, radar echoes, radar targets, and gravity waves are among the topics covered.

  8. Heterodyne efficiency for a coherent laser radar with diffuse or aerosol targets

    NASA Technical Reports Server (NTRS)

    Frehlich, R. G.

    1993-01-01

    The performance of a Coherent Laser Radar is determined by the statistics of the coherent Doppler signal. The heterodyne efficiency is an excellent indication of performance because it is an absolute measure of beam alignment and is independent of the transmitter power, the target backscatter coefficient, the atmospheric attenuation, and the detector quantum efficiency and gain. The theoretical calculation of heterodyne efficiency for an optimal monostatic lidar with a circular aperture and Gaussian transmit laser is presented including beam misalignment in the far-field and near-field regimes. The statistical behavior of estimates of the heterodyne efficiency using a calibration hard target are considered. For space based applications, a biased estimate of heterodyne efficiency is proposed that removes the variability due to the random surface return but retains the sensitivity to misalignment. Physical insight is provided by simulation of the fields on the detector surface. The required detector calibration is also discussed.

  9. Integrated multi-channel receiver for a pulsed time-of-flight laser radar

    NASA Astrophysics Data System (ADS)

    Jiang, Yan; Liu, Ruqing; Zhu, Jingguo

    2015-04-01

    An integrated multi-channel receiver for a pulsed time-of-flight (TOF) laser rangefinder has been designed in this paper. The receiver chip as an important component of the laser radar device has been implemented in a 0.18um CMOS process. It consists of sixteen channels and every channel includes preamplifier, amplifier stages, high-pass filter and a timing discriminator which contains a timing comparator and a noise comparator. Each signal paths is independent of other channels. Based on the simulations, the bandwidth and transimpedance of the amplifier channel are 652MHz, 99dBΩ. Under the simulation condition of TT corner and 27°C, the propagation delay of the discriminator is 2.15ns and the propagation delay dispersion is 223ps. The power consumption during continuous measurement is 810mW, and the operating temperature range of the device is -10~60°C.

  10. Cloud-base water content measurement using single wavelength laser-radar data.

    PubMed

    Cohen, A

    1975-12-01

    Monochromatic backscattering laser-radar data are used for the determination on the number density of cloud droplets within a cumulus cloud base. The method is based upon general properties of a cloud base as derived from in situ measurements in a large variety of continental cumulus clouds. The backscatter laser profile from the cloud base is analyzed, and points with equal optical-depth values are detected in each profile. The method of detection requires no knowledge of the multiple scattering contribution, even though its effect is not neglected and is allowed to vary as a function of the optical depth. Corrections for general clouds are suggested based upon lidar measurements and analysis of the backscattering profile characteristics.

  11. Laser radar range and detection performance for MEMS corner cube retroreflector arrays

    NASA Astrophysics Data System (ADS)

    Grasso, Robert J.; Odhner, Jefferson E.; Stewart, Hamilton; McDaniel, Robert V.

    2004-12-01

    BAE SYSTEMS reports on a program to characterize the performance of MEMS corner cube retroreflector arrays under laser illumination. These arrays have significant military and commercial application in the areas of: 1) target identification; 2) target tracking; 3) target location; 4) identification friend-or-foe (IFF); 5) parcel tracking, and; 6) search and rescue assistance. BAE SYSTEMS has theoretically determined the feasibility of these devices to learn if sufficient signal-to-noise performance exists to permit a cooperative laser radar sensor to be considered for device location and interrogation. Results indicate that modest power-apertures are required to achieve SNR performance consistent with high probability of detection and low false alarm rates.

  12. Laser radar range and detection performance for MEMS corner cube retroreflector arrays

    NASA Astrophysics Data System (ADS)

    Grasso, Robert J.; Jost, Steven R.; Smith, M. J.; McDaniel, Robert V.

    2004-01-01

    BAE SYSTEMS reports on a program to characterize the performance of MEMS corner cube retroreflector arrays under laser illumination. These arrays have significant military and commercial application in the areas of: (1) target identification; (2) target tracking; (3) target location; (4) identification friend-or-foe (IFF); (5) parcel tracking, and; (6) search and rescue assistance. BAE SYSTEMS has theoretically determined the feasibility of these devices to learn if sufficient signal-to-noise performance exists to permit a cooperative laser radar sensor to be considered for device location and interrogation. Results indicate that modest power-apertures are required to achieve SNR performance consistent with high probability of detection and low false alarm rates.

  13. Analysis of influential factors on a space target's laser radar cross-section

    NASA Astrophysics Data System (ADS)

    Han, Yi; Sun, Huayan; Guo, Huichao

    2014-03-01

    This paper utilises the idea of theoretical analysis to introduce a fast and visual laser radar cross-section (LRCS) calculation method for space targets that is implemented with OpenGL. We chose the cube, cylinder and cone as targets based on the general characteristics of satellite shapes. The four-parameter mono-station BRDF is used, and we assume the surface materials are either purely diffuse, purely specular or mixed. The degree of influence on a target's total LRCS of the target's shape and size and the surface materials' BRDF are described. We describe the general laws governing influential factors by comparing simulated results. These conclusions can provide a reference for new research directions and methods to determine a target's laser scattering characteristics.

  14. Practical internal combustion engine laser spark plug development

    NASA Astrophysics Data System (ADS)

    Myers, Michael J.; Myers, John D.; Guo, Baoping; Yang, Chengxin; Hardy, Christopher R.

    2007-09-01

    Fundamental studies on laser ignition have been performed by the US Department of Energy under ARES (Advanced Reciprocating Engines Systems) and by the California Energy Commission under ARICE (Advanced Reciprocating Internal Combustion Engine). These and other works have reported considerable increases in fuel efficiencies along with substantial reductions in green-house gas emissions when employing laser spark ignition. Practical commercial applications of this technology require low cost high peak power lasers. The lasers must be small, rugged and able to provide stable laser beam output operation under adverse mechanical and environmental conditions. New DPSS (Diode Pumped Solid State) lasers appear to meet these requirements. In this work we provide an evaluation of HESP (High Efficiency Side Pumped) DPSS laser design and performance with regard to its application as a practical laser spark plug for use in internal combustion engines.

  15. The internal structure of the Brunt Ice Shelf, Antarctica from ice-penetrating radar

    NASA Astrophysics Data System (ADS)

    King, Edward; De Rydt, Jan; Gudmundsson, Hilmar

    2016-04-01

    The Brunt Ice Shelf is a small feature on the Coats Land Coast of the Weddell Sea, Antarctica. It is unusual among Antarctic ice shelves because the ice crossing the grounding line from the ice sheet retains no structural integrity, so the ice shelf comprises icebergs of continental ice cemented together by sea ice, with the whole blanketed by in-situ snowfall. The size and distribution of the icebergs is governed by the thickness profile along the grounding line. Where bedrock troughs discharge thick ice to the ice shelf, the icebergs are large and remain close together with little intervening sea ice. Where bedrock ridges mean the ice crossing the grounding line is thin, the icebergs are small and widely-scattered with large areas of sea ice between them. To better understand the internal structure of the Brunt Ice Shelf and how this might affect the flow dynamics we conducted ice-penetrating radar surveys during December 2015 and January 2016. Three different ground-based radar systems were used, operating at centre frequencies of 400, 50 and 10 MHz respectively. The 400 MHz system gave detailed firn structure and accumulation profiles as well as time-lapse profiles of the active propagation of a crevasse. The 50 MHz system provided intermediate-level detail of iceberg distribution and thickness as well as information on the degree of salt water infiltration into the accumulating snow pack. The 10 MHz system used a high-power transmitter in an attempt to measure ice thickness beneath salt-impregnated ice. In this poster we will present example data from each of the three radar systems which will demonstrate the variability of the internal structure of the ice shelf. We will also present preliminary correlations between the internal structure and the surface topography from satellite data.

  16. Airborne laser radar: systems and methods for reconnaissance and terrain modeling

    NASA Astrophysics Data System (ADS)

    Steinvall, Ove K.; Soederman, Ulf; Ahlberg, Simon; Sandberg, Martin; Letalick, Dietmar; Jungert, Erland

    1999-05-01

    Recently a number of airborne nadir scanning laser radars have been developed for both military and civilian applications. These have range resolutions on the order of 10 cm but relatively moderate area coverage rates, in the range 1000 - 10,000 m2/s (3.6 - 36 km2/h) when operating in a high resolution mode with 0.25 m spot distance. Technology development in laser sources, scanning techniques and signal processing will probably improve the area coverage substantially and lead to compact systems suitable for new applications, including the use in UAV:s. Present nadir capability could be combined with a forward looking capability for guidance and obstacle avoidance in autonomous or semi-autonomous systems. The paper will investigate the potential performance of such combined systems using state-of-the-art lasers and receiver technology. Among the applications for both military and civilian users we note the collection of 3-D data for terrain modeling and object recognition. For these functions signal processing using multiple echo and intensity information is of great value as well as adding passive senor information. Full wave form processing will further improve the information for example to characterize trees. The use of high resolution 3-D data in synthetic environments is obvious and will be discussed. Experimental data collected with a commercial laser system, TopEye, developed by Saab Dynamics, will be shown and some image examples will be discussed in relation to different applications.

  17. Comparison of Surface Elevation Changes of the Greenland and Antarctic Ice Sheets from Radar and Laser Altimetry

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Brenner, Anita C.; Barbieri, Kristine; DiMarzio, John P.; Li, Jun; Robbins, John; Saba, Jack L.; Yi, Donghui

    2012-01-01

    A primary purpose of satellite altimeter measurements is determination of the mass balances of the Greenland and Antarctic ice sheets and changes with time by measurement of changes in the surface elevations. Since the early 1990's, important measurements for this purpose have been made by radar altimeters on ERS-l and 2, Envisat, and CryoSat and a laser altimeter on ICESat. One principal factor limiting direct comparisons between radar and laser measurements is the variable penetration depth of the radar signal and the corresponding location of the effective depth of the radar-measured elevation beneath the surface, in contrast to the laser-measured surface elevation. Although the radar penetration depth varies significantly both spatially and temporally, empirical corrections have been developed to account for this effect. Another limiting factor in direct comparisons is caused by differences in the size of the laser and radar footprints and their respective horizontal locations on the surface. Nevertheless, derived changes in elevation, dHldt, and time-series of elevation, H(t), have been shown to be comparable. For comparisons at different times, corrections for elevation changes caused by variations in the rate offrrn compaction have also been developed. Comparisons between the H(t) and the average dH/dt at some specific locations, such as the Vostok region of East Antarctic, show good agreement among results from ERS-l and 2, Envisat, and ICESat. However, Greenland maps of dHidt from Envisat and ICESat for the same time periods (2003-2008) show some areas of significant differences as well as areas of good agreement. Possible causes of residual differences are investigated and described.

  18. GLACIER MONITORING SYSTEM IN COLOMBIA - complementing glaciological measurements with laser-scanning and ground-penetrating radar surveys

    NASA Astrophysics Data System (ADS)

    Ceballos, Jorge; Micheletti, Natan; Rabatel, Antoine; Mölg, Nico; Zemp, Michael

    2015-04-01

    Colombia (South America) has six small glaciers (total glacierized area of 45 Km2); their geographical location, close to zero latitude, makes them very sensitive to climate changes. An extensive monitoring program is being performed since 2006 on two glaciers, with international cooperation supports. This presentation summarizes the results of glacier changes in Colombia and includes the latest results obtained within the CATCOS Project - Phase 1 (Capacity Building and Twinning for Climate Observing Systems) signed between Colombia and Switzerland, and within the Joint Mixte Laboratory GREAT-ICE (IRD - France), with the application of LiDAR technology and GPR-based ice thickness measurements at Conejeras Glacier. Conejeras Glacier (Lat. N. 4° 48' 56"; Long. W. 75° 22' 22"; Alt. Max. 4915m.; Alt. Min. 4730m. Area 0.2 Km2) is located on the north-western side of Santa Isabel Volcano. This glacier belongs to global glacier monitoring network of the World Glacier Monitoring Service (WGMS-ID: 2721). The surface mass balance is calculated monthly using the direct glaciological method. Between April 2006 and May 2014, Conejeras Glacier showed a cumulative loss of -21 m w.e. The CATCOS Project allowed to improve the glacier monitoring system in Colombia with two main actions: (1) a terrestrial laser scanner survey (RIEGL VZ-6000 terrestrial laser scanner, property of Universities of Lausanne and Fribourg); and (2) ice thickness measurements (Blue System Integration Ltd. Ice Penetrating Radar of property of IRD). The terrestrial laser-scanning survey allowed to realize an accurate digital terrain model of the glacier surface with 13 million points and a decimetric resolution. Ice thickness measurements showed an average glacier thickness of 22 meters and a maximum of 52 meters.

  19. Laser- and Radar-based Mission Concepts for Suborbital and Spaceborne Monitoring of Seismic Surface Waves

    SciTech Connect

    Foxall, W; Schultz, C A; Tralli, D M

    2004-09-21

    The development of a suborbital or spaceborne system to monitor seismic waves poses an intriguing prospect for advancing the state of seismology. This capability would enable an unprecedented global mapping of the velocity structure of the earth's crust, understanding of earthquake rupture dynamics and wave propagation effects, and event source location, characterization and discrimination that are critical for both fundamental earthquake research and nuclear non-proliferation applications. As part of an ongoing collaboration between LLNL and JPL, an advanced mission concept study assessed architectural considerations and operational and data delivery requirements, extending two prior studies by each organization--a radar-based satellite system (JPL) for earthquake hazard assessment and a feasibility study of space- or UAV-based laser seismometer systems (LLNL) for seismic event monitoring. Seismic wave measurement requirements include lower bounds on detectability of specific seismic sources of interest and wave amplitude accuracy for different levels of analysis, such as source characterization, discrimination and tomography, with a 100 {micro}m wave amplitude resolution for waves nominally traveling 5 km/s, an upper frequency bound based on explosion and earthquake surface displacement spectra, and minimum horizontal resolution (1-5 km) and areal coverage, in general and for targeted observations. For a radar system, corresponding engineering and operational factors include: Radar frequency (dictated by required wave amplitude measurement accuracy and maximizing ranging, Doppler or interferometric sensitivity), time sampling (maximum seismic wave frequency and velocity), and overall system considerations such as mass, power and data rate. Technical challenges include characterization of, and compensation for, phase distortion resulting from atmospheric and ionospheric perturbations and turbulence, and effects of ground scattering characteristics and seismic

  20. A Miniature, High-Resolution Laser Radar Operating at Video Rates

    SciTech Connect

    SMITHPETER,COLIN L.; NELLUMS,ROBERT O.; LEBIEN,STEVEN M.; STUDOR,GEORGE

    2000-06-26

    The authors are developing a laser radar to meet the needs of NASA for a 5-lb, 150 in{sup 3} image sensor with a pixel range accuracy of 0.1-inch. NASA applications include structural dynamics measurements, navigation guidance in rendezvous and proximity operations, and space vehicle inspection. The sensor is based on the scannerless range imager architecture developed at Sandia. This architecture modulates laser floodlight illumination and a focal plane receiver to phase encode the laser time of flight (TOF) for each pixel. They believe this approach has significant advantages over architectures directly measuring TOF including high data rate, reduced detector bandwidth, and conventional FPA detection. A limitation of the phase detection technique is its periodic nature, which provides relative range information over a finite ambiguity interval. To extend the operating interval while maintaining a given range resolution, a LADAR sensor using dual modulation frequencies has been developed. This sensor also extends the relative range information to absolute range by calibrating a gating function on the receiver to the TOF. The modulation frequency values can be scaled to meet the resolution and range interval requirements of different applications. Results from the miniature NASA sensor illustrate the advantages of the dual-frequency operation and the ability to provide the range images of 640 by 480 pixels at 30 frames per second.

  1. High-power pulsed diode laser for automotive scanning radar sensor

    NASA Astrophysics Data System (ADS)

    Kimura, Yuji; Matsushita, Noriyuki; Kato, Hisaya; Abe, Katsunori; Atsumi, Kinya

    2000-02-01

    High performance pulsed AlGaAs/GaAs wide stripe diode laser has been developed for the automotive distance-measuring scanning radar sensor. The laser diode is required high output power of 15 W and a long time reliability in spite of being used in a harsh environment such as wide temperature range, mechanical vibrations at the front bumper and so on. The device is designed by employing a multiple quantum well structure as an active layer for high output power with low drive current and high temperature operations. Moreover we reduce catastrophic optical damage power level and control the beam divergence angle by introducing optimized optical waveguide layers. In the chips bonding part, we developed a new thin film Au-Sn-Ni solder system. The bonding temperature can be lowered by using this system, whereby the thermal damage to the laser diode can be reduced. Furthermore, highly stable bonding is carried out by improving wetting ability in this system. We have achieved more than 22 W light output power at 20A pulse current under room temperature and more than 16 W light output power under 90 degrees Celsius. High reliability over 10,000 hours is performed for automotive use under pulsed operation at 90 degrees Celsius, 50 ns pulse width, 8 kHz frequency and 15 W light output power.

  2. International Laser Ranging Service (ILRS): Terms of Reference

    NASA Technical Reports Server (NTRS)

    Husson, Van; Noll, Carey

    2000-01-01

    The International Laser Ranging Service (ILRS) is an established Service within Section II , Advanced Space Technology, of the International Association of Geodesy (IAG). The primary objective of the ILRS is to provide a service to support, through Satellite and Lunar Laser Ranging data and related products, geodetic and geophysical research activities as well as International Earth Rotation Service (IERS) products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). The service also develops the necessary standards/specifications and encourages international adherence to its conventions.

  3. Doppler laser radar for range and speed measurement of road targets

    NASA Astrophysics Data System (ADS)

    Lin, Yanfang; Mao, Xuesong; Fang, Jianchao; Zhang, Tao

    2016-11-01

    A pulsed coherent vehicle laser radar system basing on the measurement of light flight time and Doppler frequency shift is demonstrated for the first time, which features a simple design that uses one photodiode (PD) as its optical detector. Pseudo random noise (PN) code is used for modulating the amplitude of transmitting light. Correlation function of the received echoes and the local modulating codes is calculated for measuring the light flight time. Due to PN code modulation, beat signal output from PD is piecewise continuous, which causes equidistant sampling of Doppler sine wave not feasible. In order that Doppler frequency be correctly measured by using fast Fourier transform (FFT), a simple signal amplitude modification method is derived from the definition of Fourier transform.

  4. Occluded target viewing and identification high-resolution 2D imaging laser radar

    NASA Astrophysics Data System (ADS)

    Grasso, Robert J.; Dippel, George F.; Cecchetti, Kristen D.; Wikman, John C.; Drouin, David P.; Egbert, Paul I.

    2007-09-01

    BAE SYSTEMS has developed a high-resolution 2D imaging laser radar (LADAR) system that has proven its ability to detect and identify hard targets in occluded environments, through battlefield obscurants, and through naturally occurring image-degrading atmospheres. Limitations of passive infrared imaging for target identification using medium wavelength infrared (MWIR) and long wavelength infrared (LWIR) atmospheric windows are well known. Of particular concern is that as wavelength is increased the aperture must be increased to maintain resolution, hence, driving apertures to be very larger for long-range identification; impractical because of size, weight, and optics cost. Conversely, at smaller apertures and with large f-numbers images may become photon starved with long integration times. Here, images are most susceptible to distortion from atmospheric turbulence, platform vibration, or both. Additionally, long-range identification using passive thermal imaging is clutter limited arising from objects in close proximity to the target object.

  5. A high sensitive 66 dB linear dynamic range receiver for 3-D laser radar

    NASA Astrophysics Data System (ADS)

    Ma, Rui; Zheng, Hao; Zhu, Zhangming

    2017-08-01

    This study presents a CMOS receiver chip realized in 0.18 μm standard CMOS technology and intended for high precision 3-D laser radar. The chip includes an adjustable gain transimpedance pre-amplifier, a post-amplifier and two timing comparators. An additional feedback is employed in the regulated cascode transimpedance amplifier to decrease the input impedance, and a variable gain transimpedance amplifier controlled by digital switches and analog multiplexer is utilized to realize four gain modes, extending the input dynamic range. The measurement shows that the highest transimpedance of the channel is 50 k {{Ω }}, the uncompensated walk error is 1.44 ns in a wide linear dynamic range of 66 dB (1:2000), and the input referred noise current is 2.3 pA/\\sqrt{{Hz}} (rms), resulting in a very low detectable input current of 1 μA with SNR = 5.

  6. Small Objects in Low-Earth Intersecting Ground-Based Laser Radar Operational Envelopes

    NASA Technical Reports Server (NTRS)

    Boccio, Dona V.

    2002-01-01

    NASA/Marshall Space Flight Center, in collaboration with the Air Force Research Laboratory/Directed Energy Directorate, is considering a series of experiments to demonstrate small object tracking capability. One such experiment involves a microsatellite, about 25 cm in diameter, which will be deployed from a Space Shuttle Hitchhiker canister or from an Air Force vehicle. The High Performance CO2 Ladar Surveillance Sensor (HI-CLASS) and the Advanced Electro-Optics System (AEOS) will be used to detect the micro-satellite. The goal of this paper is to determine the number of times per day that a micro-satellite orbiting at a known altitude and inclination will be visible to the laser radar, and the length of time that the micro-satellite will be visible on each pass.

  7. Interpreting Segmented Laser Radar Images Using a Knowledge-Based System

    NASA Astrophysics Data System (ADS)

    Chu, Chen-Chau; Nandhakumar, Nagaraj; Aggarwal, Jake K.

    1990-03-01

    This paper presents a knowledge-based system (KBS) for man-made object recognition and image interpretation using laser radar (ladar) images. The objective is to recognize military vehicles in rural scenes. The knowledge-based system is constructed using KEE rules and Lisp functions, and uses results from pre-processing modules for image segmentation and integration of segmentation maps. Low-level attributes of segments are computed and converted to KEE format as part of the data bases. The interpretation modules detect man-made objects from the background using low-level attributes. Segments are grouped into objects and then man-made objects and background segments are classified into pre-defined categories (tanks, ground, etc.) A concurrent server program is used to enhance the performance of the KBS by serving numerical and graphics-oriented tasks for the interpretation modules. Experimental results using real ladar data are presented.

  8. Feasibility study of synthetic aperture infrared laser radar techniques for imaging of static and moving objects.

    PubMed

    Yoshikado, S; Aruga, T

    1998-08-20

    Techniques for two types of 10-mum band synthetic aperture infrared laser radar using a hypothetical reference point target (RPT) are presented. One is for imaging static objects with a single two-dimensional scanning aperture. Through the simple manipulation of a reference wave phase, a desired image can be obtained merely by the two-dimensional Fourier transformation of the correlator output between the intermediate frequency signals of the reference and object waves. The other, with a one-dimensional aperture array, is for moving objects that pass across the array direction without attitude change. We performed imaging by using a two-dimensional RPT correlation method. We demonstrate the capability of these methods for imaging and evaluate the necessary conditions for signal-to-noise ratio and random phase errors in signal reception through numerical simulations in terms of feasibility.

  9. The design of laser radar data acquisition system based on LabVIEW

    NASA Astrophysics Data System (ADS)

    Han, Dalong; Han, Shaokun; Cao, Jingya; Xia, Wenze; Wang, Liang

    2015-08-01

    Lidar has been widely used in areas of ranging and imaging. To be able to perform real-time control of the entire system, this article designed a lidar data acquisition system based on LabVIEW and the PC system allows real-time display for data acquired by lidar system. Through the serial port, the PC system can adjust part of the laser radar system parameters, such as frequency, APD (Avalanche Photo Diode) bias, the echo threshold, etc in real-time. In this way, we achieve the instruction communication between the PC system and the lidar. In addition, the PC system can also acquire data from the lidar through the Ethernet. Through the practical test, the PC system can successfully acquire and display the echo signal measured by lidar system in real-time, and function of parameter adjustment is also very sensitive.

  10. Internal waves in the Gulf of California - Observations from a spaceborne radar

    NASA Technical Reports Server (NTRS)

    Fu, L.-L.; Holt, B.

    1984-01-01

    Pronounced signatures of internal waves were detected repeatedly in the Gulf of California by the Seasat synthetic aperture radar (SAR). A series of nine images with exactly repeating ground coverage was used to study the temporal variability of the internal wave field in the area. It was found that the number of observed wave groups was highly correlated with the strength of the local tides: the maximum number occurred during spring tides and the minimum number occurred during neap tides, indicating that the internal waves were tidally forced. Most of the wave activity was found to the north of 28 deg N where the tides were the strongest in the Gulf. The application of a simple, nonlinear internal wave model to the observations indicated that the peak-to-peak amplitude of the observed waves was about 50 m with an uncertainty of a factor of 2. The estimated upper bound for the rate of the loss of tidal energy to internal waves was about 5 x 10 to the 15th erg/s, representing only 10 percent of the rate of the dissipation of the dominant M2 tide in the Gulf.

  11. Internal waves in the Gulf of California - Observations from a spaceborne radar

    NASA Technical Reports Server (NTRS)

    Fu, L.-L.; Holt, B.

    1984-01-01

    Pronounced signatures of internal waves were detected repeatedly in the Gulf of California by the Seasat synthetic aperture radar (SAR). A series of nine images with exactly repeating ground coverage was used to study the temporal variability of the internal wave field in the area. It was found that the number of observed wave groups was highly correlated with the strength of the local tides: the maximum number occurred during spring tides and the minimum number occurred during neap tides, indicating that the internal waves were tidally forced. Most of the wave activity was found to the north of 28 deg N where the tides were the strongest in the Gulf. The application of a simple, nonlinear internal wave model to the observations indicated that the peak-to-peak amplitude of the observed waves was about 50 m with an uncertainty of a factor of 2. The estimated upper bound for the rate of the loss of tidal energy to internal waves was about 5 x 10 to the 15th erg/s, representing only 10 percent of the rate of the dissipation of the dominant M2 tide in the Gulf.

  12. A note on radar altimeter signatures of internal solitary waves in the ocean

    NASA Astrophysics Data System (ADS)

    da Silva, J. C. B.; Cerqueira, A. L. F.

    2016-10-01

    It is well known that Internal Waves of tidal frequency (i.e. Internal Tides) are successfully detected in seasurface height (SSH) by satellite altimetry [1]. Shorter period Internal Solitary Waves (ISWs), whose periods are an order of magnitude smaller than tidal internal waves, are however generally assumed too small to be detected with standard altimeters (at low sampling rates, i.e. 1 Hz). This is because the Radar Altimeter (RA) footprint is somewhat larger, or of similar size at best, than the ISWs typical wavelengths. Here it will be demonstrated that new generation high sampling rate satellite altimetry data (i.e. 20 Hz) hold a variety of short-period signatures that are consistent with surface manifestations of ISWs in the ocean. Our observational method is based on satellite synergy with imaging sensors such as Synthetic Aperture Radar (SAR) and other high-resolution optical sensors (e.g. 250m resolution MODIS images) with which ISWs are unambiguously recognized. A first order commonly accepted ISW radar imaging mechanism is based on hydrodynamic modulation models [2] [3] in which the straining of surface waves due to ISW orbital currents is known to cause modulation of decimeter-scale surface waves, which have group velocities close to the IW phase velocity. This effect can be readily demonstrated by measurements of wind wave slope variances associated with short-period ISWs, as accomplished in the pioneer work of Hughes and Grant [4]. Mean square slope can be estimated from nadir looking RAs using a geometric optics (specular) scattering model [5][6][7], and directly obtained from normalized backscatter (sigma0) along-track records. We use differential scattering from the dual-band (Ku- and C-bands) microwave pulses of the Jason- 2 high-rate RA to isolate the contribution of small-scale surface waves to mean square slope. The differenced altimeter mean square slope estimate, derived for the nominal wave number range 40-100 rad/m, is then used to detect

  13. Error Ellipsoid Analysis for the Diameter Measurement of Cylindroid Components Using a Laser Radar Measurement System

    PubMed Central

    Du, Zhengchun; Wu, Zhaoyong; Yang, Jianguo

    2016-01-01

    The use of three-dimensional (3D) data in the industrial measurement field is becoming increasingly popular because of the rapid development of laser scanning techniques based on the time-of-flight principle. However, the accuracy and uncertainty of these types of measurement methods are seldom investigated. In this study, a mathematical uncertainty evaluation model for the diameter measurement of standard cylindroid components has been proposed and applied to a 3D laser radar measurement system (LRMS). First, a single-point error ellipsoid analysis for the LRMS was established. An error ellipsoid model and algorithm for diameter measurement of cylindroid components was then proposed based on the single-point error ellipsoid. Finally, four experiments were conducted using the LRMS to measure the diameter of a standard cylinder in the laboratory. The experimental results of the uncertainty evaluation consistently matched well with the predictions. The proposed uncertainty evaluation model for cylindrical diameters can provide a reliable method for actual measurements and support further accuracy improvement of the LRMS. PMID:27213385

  14. Error Ellipsoid Analysis for the Diameter Measurement of Cylindroid Components Using a Laser Radar Measurement System.

    PubMed

    Du, Zhengchun; Wu, Zhaoyong; Yang, Jianguo

    2016-05-19

    The use of three-dimensional (3D) data in the industrial measurement field is becoming increasingly popular because of the rapid development of laser scanning techniques based on the time-of-flight principle. However, the accuracy and uncertainty of these types of measurement methods are seldom investigated. In this study, a mathematical uncertainty evaluation model for the diameter measurement of standard cylindroid components has been proposed and applied to a 3D laser radar measurement system (LRMS). First, a single-point error ellipsoid analysis for the LRMS was established. An error ellipsoid model and algorithm for diameter measurement of cylindroid components was then proposed based on the single-point error ellipsoid. Finally, four experiments were conducted using the LRMS to measure the diameter of a standard cylinder in the laboratory. The experimental results of the uncertainty evaluation consistently matched well with the predictions. The proposed uncertainty evaluation model for cylindrical diameters can provide a reliable method for actual measurements and support further accuracy improvement of the LRMS.

  15. Development of a high-resolution laser radar for 3D imaging in artwork cataloging

    NASA Astrophysics Data System (ADS)

    Bordone, Andrea; Ferri De Collibus, Mario; Fantoni, Roberta; Fornetti, Giorgio G.; Guarneri, Marianna; Poggi, Claudio; Ricci, Roberto

    2003-04-01

    A high resolution Amplitude Modulation Laser Radar (AM-LR) sensor has recently been developed, aimed at accurately reconstructing 3D digital models of real targets -- either single objects or complex scenes. The sensor sounding beam can be swept linearly across the object or circularly around it, by placing the object on a controlled rotation platform. Both intensity and phase shift of the back-scattered light are then collected and processed, providing respectively a shade-free photographic-like picture and accurate range data in the form of a range or depth image, with resolution depending mainly on the laser modulation frequency. Starting from the sample points, with an uncertainty that can be made as small as 100 μm, the complete object surface can be reconstructed by using specifically developed software tools. The system has been successfully applied to scan different types of real surfaces (stone, wood, bones) and is expected to have significant applications in industrial machining, artwork cataloguing and medical diagnostics. Examples of 3D reconstructions are presented and the relevance of this technology for reverse engineering applied to artwork restoration and conservation is briefly discussed.

  16. Simulation of a laser radar to improve visiblity measurements in dense fog

    NASA Astrophysics Data System (ADS)

    Streicher, Juergen

    1992-12-01

    Lidar is the short form of light detection and ranging. The first application of a lidar system was, as in the radar technique, the determination of the distance to large-sized particles (target recognition). Nowadays, it is of more interest to measure the structure of the atmosphere in far distances (remote sensing) to get, for example, information about the mass concentration of the industrial pollution or the visibility conditions in dense fog. In this case the action and reaction of the laser light with the particles is made by very small and different scatterers (molecules, atoms, or aerosols) and, therefore, extremely complex. A simulation program that helps to determine the visibility with a lidar has been developed to present the effects of the components of the system (laser, transmitter, receiver) as well as the parameters of the atmosphere (inhomogeneities, fog, clouds) in a convenient way. A change in any parameter is taken into account instantaneously, so this program can be called an almost real time simulator. A computer with a graphic user interface was chosen to realize this as simply as possible: The Commodore Amiga. The simulation is written in `C' to get the best performance for the calculations.

  17. Transmitter and receiver antenna gain analysis for laser radar and communication systems

    NASA Technical Reports Server (NTRS)

    Klein, B. J.; Degnan, J. J.

    1973-01-01

    A comprehensive and fairly self-contained study of centrally obscured optical transmitting and receiving antennas is presented and is intended for use by the laser radar and communication systems designer. The material is presented in a format which allows the rapid and accurate evaluation of antenna gain. The Fresnel approximation to scalar wave theory is reviewed and the antenna analysis proceeds in terms of the power gain. Conventional range equations may then be used to calculate the power budget. The transmitter calculations, resulting in near and far field antenna gain patterns, assumes the antenna is illuminated by a laser operating in the fundamental cavity mode. A simple equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn which display the losses in antenna gain due to pointing errors and the cone angle of the outgoing beam as a function of antenna size and central obscuration. The use of telescope defocusing as an approach to spreading the beam for target acquisition is compared to some alternate methods.

  18. Performance of the multifunctional CW CO2-laser radar at the TNO-FEL laboratory and during the BEST TWO field test

    NASA Astrophysics Data System (ADS)

    Hebers, H.

    1991-06-01

    Measurements performed with the multifunctional CW CO2 (Continuous Wave carbon dioxide) laser radar system are reported. The BEST TWO (Battle field Emmissive Sources Test under European Theatre Weather and Obscurants) trial was held in France, at Camp de Mourmelon, Jul. 26 to Aug. 10 1990, to test battlefield effects on long range target acquisition by electrooptical systems. The results and experience gained from these experiments are described and recommendations for further improvement of the multifunctional laser radar setup are given.

  19. Realization of compatible stealth material for infrared, laser and radar based on one-dimensional doping-structure photonic crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Ji-Kui; Shi, Jia-Ming; Zhao, Da-Peng; Wang, Qi-Chao; Wang, Cheng-Ming

    2017-09-01

    To inhibit the radiant infrared energy between 8 and 14 μm, which is the infrared atmospheric window, and decrease the echo power of detecting laser and radar, to achieve compatible stealth, a doping structural one-dimensional photonic crystal (1-D PC) with Ge, ZnSe and Si was fabricated; and then combine it with radar absorbing material (RAM) to make a compound. After that, the reflection spectra of this compound was tested, and the result shows a high average reflectance (89.5%) in 8-14 μm waveband, and a reflective valley (39.8%) in the wavelength of 10.6 μm, which is the wavelength of CO2 laser; and the reflectance in radar band shows that at high frequency, especially between 7.8 and 18 GHz, the radar power is strongly absorbed by this material and the reflected energy attenuate over 10 dB within the range from 11.1 GHz to 18.3 GHz, even 24.5 dB to the most in the frequency of 14.6 GHz.

  20. Picturing internal fractures of historical statues using ground penetrating radar method

    NASA Astrophysics Data System (ADS)

    Kadioglu, S.; Kadioglu, Y. K.

    2010-03-01

    The aim of the study is to formulate an approach to the monitoring of internal micro discontiniuties in a hybrid 2-D/3-D image of ground penetrating radar (GPR) data gathered on historical monument groups, and to indicate methodologically rearranging amplitude-color scale and its opacity functions to activate micro fractures in monument groups including three colossal women, three men, and 24 lion statues in Mustafa Kemal ATATÜRK's mausoleum (ANITKABIR) in Ankara, Turkey. Additionally, this paper illustrates the use of petrographic research to describe the monument and its groups. To achieve the aim, data measurements were carried out on the monument groups with spaced 10 cm profiles and 1.6 GHz antenna. The 3-D image was transparent 3-D volumes of the GPR data set that highlighted internal micro fractures and cavities in the statues. Rearranging appropriate amplitude-color scale and formulating the opaque of the data sets were the keys to the transparent 3-D data visualizations. As a result, the internal fractures and cavities were successfully visualized in the three women, three men and twenty-four lion statues. Micro fractures were observed particularly at the rim of the vesicular of the rocks under a polarizing microscope.

  1. A digital elevation model of the Greenland Ice Sheet derived from combined laser and radar altimetry data

    NASA Astrophysics Data System (ADS)

    Fredenslund Levinsen, Joanna; Smith, Ben; Sørensen, Louise S.; Forsberg, René

    2014-05-01

    When estimating elevation changes of ice-covered surfaces from radar altimetry, it is important to correct for slope-induced errors. They cause the reflecting point of the pulse to move up-slope and thus return estimates in the wrong coordinates. Slope-induced errors can be corrected for by introducing a Digital Elevation Model (DEM). In this work, such a DEM is developed for the Greenland Ice Sheet using a combination of Envisat radar and ICESat laser altimetry. If time permits, CryoSat radar altimetry will be included as well. The reference year is 2010 and the spatial resolution 2.5 x 2.5 km. This is in accordance with the results obtained in the ESA Ice Sheets CCI project showing that a 5 x 5 km grid spacing is reasonable for ice sheet-wide change detection (Levinsen et al., 2013). Separate DEMs will be created for the given data sets, and the geostatistical spatial interpolation method collocation will be used to merge them, thus adjusting for potential inter-satellite biases. The final DEM is validated with temporally and spatially agreeing airborne lidar data acquired in the NASA IceBridge and ESA CryoVex campaigns. The motivation for developing a new DEM is based on 1) large surface changes presently being observed, and mainly in margin regions, hence necessitating updated topography maps for accurately deriving and correcting surface elevation changes, and 2) although radar altimetry is subject to surface penetration of the signal into the snowpack, data is acquired continuously in time. This is not the case with e.g. ICESat, where laser altimetry data were obtained in periods of active lasers, i.e. three times a year with a 35-day repeat track. Previous DEMs e.g. have 2007 as the nominal reference year, or they are built merely from ICESat data. These have elevation errors as small as 10 cm, which is lower than for Envisat and CryoSat. The advantage of an updated DEM consisting of combined radar and laser altimetry therefore is the possibility of

  2. Multi-channel photon counting three-dimensional imaging laser radar system using fiber array coupled Geiger-mode avalanche photodiode

    NASA Astrophysics Data System (ADS)

    Shu, Rong; Huang, Genghua; Hou, Libing; He, Zhiping; Hu, Yihua

    2012-09-01

    Photon counting laser radar is the most sensitive and efficiency detection method of direct-detection laser radar. With the use of Geiger-mode avalanche photodiode (APD) or other single photon detectors, every laser photon could be sufficiently used for ranging and three-dimensional imaging. The average energy of received laser signal could be as low as a single photon, or even less than one. This feature of photon counting laser radar enables ranging under conditions of long range, low laser pulse energy, and multi-pixel detection, while receiver size, mass, power, and complexity of laser radar are reduced. In this paper, a latest multi-channel photon counting 3D imaging laser radar system using fiber array coupled Geiger-mode avalanche photodiode (APD) is introduced. Detection model based on Poisson statistics of a photon counting laser radar is discussed. A laser radar system, working under daylight condition with ultra-low signal level (less than single photon per pulse), has been designed and analyzed with the detection model and photon counting three-dimensional imaging theory. A passively Q-switched microchip laser is used to transmit short sub-nanosecond laser pulses at 532nm. The output laser is divided into 1×8 laser spots, which correspond to 8 Geiger-mode avalanche photodiodes coupled by a 1×8-pixel fiber array. A FPGA based time-to-digital converter (TDC), which is designed by delay line interpolation technology, is used for multi-hit signal acquisition. The algorithm of photon counting three-dimensional imaging is developed for signal photon events extraction and noise filter. Three-dimensional images under daylight conditions were acquired and analyzed. The results show that system could operate at strong solar background. The ranging accuracy of the system is 6.3cm (σ) while received laser pulse signal level is only 0.04 photoelectrons on average. The advantages and feasibility of photon counting laser radar working at daylight have been

  3. International Laser Ranging Service (ILRS) 2003-2004 Annual Report

    NASA Technical Reports Server (NTRS)

    Pearlman, Michael (Editor); Noll, Carey (Editor)

    2005-01-01

    The International Laser Ranging Service (ILRS) organizes and coordinates Satellite Laser Ranging (SLR) and Lunar Laser Ranging (LLR) to support programs in geodetic, geophysical, and lunar research activities and provides the International Earth Rotation and Reference Systems Service (IERS) with products important to the maintenance of an accurate International Terrestrial Reference Frame (ITRF). This reference frame provides the stability through which systematic measurements of the Earth can be made over thousands of kilometers, decades of time, and evolution of measurement technology. This 2003-2004 ILRS annual report is comprised of individual contributions from ILRS components within the international geodetic community for the years 2003-2004. The report documents changes and progress of the ILRS and is also available on the ILRS Web site at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrsar_2003.html.

  4. Laser ignition in internal-combustion engines: Sparkless initiation

    NASA Astrophysics Data System (ADS)

    Andronov, A. A.; Gurin, V. A.; Marugin, A. V.; Savikin, A. P.; Svyatoshenko, D. E.; Tukhomirov, A. N.; Utkin, Yu. S.; Khimich, V. L.

    2014-08-01

    Laser ignition has been implemented in a single-cylinder internal combustion engine fueled by gasoline. Indicator diagrams (cylinder pressure versus crank angle) were obtained for laser ignition with nano- and microsecond pulses of an Nd:YAG laser. The maximum power of microsecond pulses was below critical for spark initiation, while the radiation wavelength was outside the spectral range of optical absorption by hydrocarbon fuels. Apparently, the ignition starts due to radiation absorption by the oil residues or carbon deposit in the combustion chamber, so that the ability of engine to operate is retained. This initiation of spark-free ignition shows the possibility of using compact semiconductor quantum-cascade lasers operating at wavelengths of about 3.4 μm (for which the optical absorption by fuel mixtures is high) in ignition systems of internal combustion engines.

  5. High-resolution laser radar for 3D imaging in artwork cataloging, reproduction, and restoration

    NASA Astrophysics Data System (ADS)

    Ricci, Roberto; Fantoni, Roberta; Ferri de Collibus, Mario; Fornetti, Giorgio G.; Guarneri, Massimiliano; Poggi, Claudio

    2003-10-01

    A high resolution Amplitude Modulated Laser Radar (AM-LR) sensor has recently been developed, aimed at accurately reconstructing 3D digital models of real targets, either single objects or complex scenes. The sensor sounding beam can be swept linearly across the object or circularly around it, by placing the object on a controlled rotating platform, enabling to obtain respectively linear and cylindrical range maps. Both amplitude and phase shift of the modulating wave of back-scattered light are collected and processed, providing respectively a shade-free, high resolution, photographic-like picture and accurate range data in the form of a range image. The resolution of range measurements depends mainly on the laser modulation frequency, provided that the power of the backscattered light reaching the detector is at least a few nW (current best performances are ~100 μm). The complete object surface can be reconstructed from the sampled points by using specifically developed software tools. The system has been successfully applied to scan different types of real surfaces (stone, wood, alloys, bones), with relevant applications in different fields, ranging from industrial machining to medical diagnostics, to vision in hostile environments. Examples of artwork reconstructed models (pottery, marble statues) are presented and the relevance of this technology for reverse engineering applied to cultural heritage conservation and restoration are discussed. Final 3D models can be passed to numeric control machines for rapid-prototyping, exported in standard formats for CAD/CAM purposes and made available on the Internet by adopting a virtual museum paradigm, thus possibly enabling specialists to perform remote inspections on high resolution digital reproductions of hardly accessible masterpieces.

  6. Novel eye-safe line scanning 3D laser-radar

    NASA Astrophysics Data System (ADS)

    Eberle, B.; Kern, Tobias; Hammer, Marcus; Schwanke, Ullrich; Nowak, Heinrich

    2014-10-01

    Today, the civil market provides quite a number of different 3D-Sensors covering ranges up to 1 km. Typically these sensors are based on single element detectors which suffer from the drawback of spatial resolution at larger distances. Tasks demanding reliable object classification at long ranges can be fulfilled only by sensors consisting of detector arrays. They ensure sufficient frame rates and high spatial resolution. Worldwide there are many efforts in developing 3D-detectors, based on two-dimensional arrays. This paper presents first results on the performance of a recently developed 3D imaging laser radar sensor, working in the short wave infrared (SWIR) at 1.5 μm. It consists of a novel Cadmium Mercury Telluride (CMT) linear array APD detector with 384x1 elements at a pitch of 25 μm, developed by AIM Infrarot Module GmbH. The APD elements are designed to work in the linear (non-Geiger) mode. Each pixel will provide the time of flight measurement, and, due to the linear detection mode, allowing the detection of three successive echoes. The resolution in depth is 15 cm, the maximum repetition rate is 4 kHz. We discuss various sensor concepts regarding possible applications and their dependence on system parameters like field of view, frame rate, spatial resolution and range of operation.

  7. Scintillation index measurement using time-correlated single-photon counting laser radar

    NASA Astrophysics Data System (ADS)

    Henriksson, Markus; Sjöqvist, Lars

    2014-08-01

    The scintillation index is a common measure of the effects of atmospheric turbulence. Using a photon-counting sensor, the integration time for each sample needs to be short enough to ensure that the intensity is constant during this time. Simultaneously, hardware limitations, including detector dead-time, restrict the count rate so that the number of counts in a single time segment is extremely low. The dead-time also introduces nonlinear effects. The variance calculation in the scintillation index formula is then dominated by quantization error, and the scintillation index is severely overestimated. We investigate two methods of correcting the scintillation index based on data from a time-correlated single-photon counting laser radar system. The first approach is based on the covariance calculation of the data and can be used for very low count rates and high temporal resolution. This method may also be useful in other cases where the variance of noisy, time-resolved data needs to be calculated. The second method is based on fitting the theoretical probability density function for the intensity fluctuation caused by propagation through turbulence to the experimental data. This method can take dead-time effects into account and be used for higher count rates.

  8. Verification measurements of the Karoo Array timing system: a laser radar based time transfer system

    NASA Astrophysics Data System (ADS)

    Siebrits, R.; Bauermeister, E.; Gamatham, R.; Adams, G.; Malan, J. A.; Burger, J. P.; Kapp, F.; Gibbon, T.; Kriel, H.; Abbott, T.

    2016-02-01

    An optical fiber based laser radar time transfer system has been developed for the 64-dish MeerKAT radiointerferometer telescope project to provide accurate atomic time to the receivers of the telescope system. This time transfer system is called the Karoo Array Timing System (KATS). Calibration of the time transfer system is essential to ensure that time is accurately transferred to the digitisers that form part of the receivers. Frequency domain reflectometry via vector network analysers is also used to verify measurements taken using time interval counters. This paper details the progress that is made in the verification measurements of the system in order to ensure that time, accurate to within a few nanoseconds of the Universal Coordinated Time (UTC, is available at the point where radio signals from astronomical sources are received. This capability enables world class transient and timing studies with a compact radio interferometer, which has inherent advantages over large single dish radio-telescopes, in observing the transient sky.

  9. Multi-sensor image interpretation using laser radar and thermal images

    NASA Astrophysics Data System (ADS)

    Chu, Chen-Chau; Aggarwal, J. K.

    1991-03-01

    A knowledge based system is presented which interprets registered laser radar and thermal images. The object is to detect and recognize man-made objects at kilometer range in outdoor scenes. The multisensor fusion approach is applied to various sensing modalities (range, intensity, velocity, and thermal) to improve both image segmentation and interpretation. The ability to use multiple sensors greatly helps an intelligent platform to understand and interact with its environment. The knowledge-based interpretation system, AIMS, is constructed using KEE and Lisp. Low-level attributes of image segments (regions) are computed by the segmentation modules and then converted into the KEE format. The interpretation system applies forward chaining in a bottom-up fashion to derive object-level interpretations from data bases generated by low-level processing modules. Segments are grouped into objects and then objects are classified into predefined categories. AIMS employs a two tiered software structure. The efficiency of AIMS is enhanced by transferring nonsymbolic processing tasks to a concurrent service manager (program). Therefore, tasks with different characteristics are executed using different software tools and methodologies.

  10. Using a neural networks algorithm for high-resolution imaging in pulsed laser radar

    NASA Astrophysics Data System (ADS)

    Joodaki, Mojtaba; Kompa, Guenter; Golam Arshad, Seyed M.; Ahmadi, Vahid; Moravvej-Farshi, Mohammed K.

    2001-11-01

    A new imaging method which can obtain the gray levels directly from the output waveform of Pulsed Laser Radar (PLR) is developed. A simple digital signal processing technique and multi layer perceptrons (MLP) type neural network (NN) have been used to obtain the gray level information from the pulse shapes. The method has been implemented in a real PLR to improve contrast and speed of 2D imaging in PLR. To compare the method with the standard method, a picture consists of 16 gray levels (from 0 for black to 1 for white) with both method has been scanned. Because of the ability of NNs in extracting the information from nonlinear and noisy data and preprocessing of the noisy input pulse shapes to the NN, the average and maximum of errors in the gray levels in comparison with standard method more than 88.5% and 72.6% improved, respectively. Because in this method the effect of the noise is decreased, it is possible to make the imaging with the same resolution as in standard method but with a lower averaging in sampling unit and this dramatically increases speed of the measurements.

  11. Digital Elevation Models of Greenland based on combined radar and laser altimetry as well as high-resolution stereoscopic imagery

    NASA Astrophysics Data System (ADS)

    Levinsen, J. F.; Smith, B. E.; Sandberg Sorensen, L.; Khvorostovsky, K.; Simonsen, S. B.; Forsberg, R.

    2015-12-01

    A number of Digital Elevation Models (DEMs) of Greenland exist, each of which are applicable for different purposes. This study presents two such DEMs: One developed by merging contemporary radar and laser altimeter data, and one derived from high-resolution stereoscopic imagery. All products are made freely available. The former DEM covers the entire Greenland. It is specific to the year 2010, providing it with an advantage over previous models suffering from either a reduced spatial/ temporal data coverage or errors from surface elevation changes (SEC) occurring during data acquisition. Radar data are acquired with Envisat and CryoSat-2, and laser data with the Ice, Cloud, and land Elevation Satellite, the Land, Vegetation, and Ice Sensor, and the Airborne Topographic Mapper. Correcting radar data for errors from slope effects and surface penetration of the echoes, and merging these with laser data, yields a DEM capable of resolving both surface depressions as well as topographic features at higher altitudes. The spatial resolution is 2 x 2 km, making the DEM ideal for application in surface mass balance studies, SEC detection from radar altimetry, or for correcting such data for slope-induced errors. The other DEM is developed in a pilot study building the expertise to map all ice-free parts of Greenland. The work combines WorldView-2 and -3 as well as GeoEye1 imagery from 2014 and 2015 over the Disko, Narsaq, Tassilaq, and Zackenberg regions. The novelty of the work is the determination of the product specifications after elaborate discussions with interested parties from government institutions, the tourist industry, etc. Thus, a 10 m DEM, 1.5 m orthophotos, and vector maps are produced. This opens to the possibility of using orthophotos with up-to-date contour lines or for deriving updated coastlines to aid, e.g., emergency management. This allows for a product development directly in line with the needs of parties with specific interests in Greenland.

  12. Characterization of microwave MESFET circuits under laser illumination. Applications to phased array radar, microwave communications, and digital clock control

    NASA Astrophysics Data System (ADS)

    Genco, Sheryl M.

    1994-10-01

    Optical injection of MESFET's directly affects the operating characteristics of the devices. The MESFET properties, induced by optical injection, can stabilize oscillator operating frequency, control amplifier gain, and open the door for feasible integrated microwave-optical devices. The optical injection of DC MESFET's, oscillators, and amplifiers is explored. Systems applications, including phased array radar, wave division multiplexing (WDM), and computer clock control, are provided. The main contributions of this research are analyzing the modulation properties of the locked laser subsystem, using the locked laser system to inject MESFET devices and characterizing the photo-effects in MESFET circuits, reducing the phase noise in a microwave oscillator via optical injection, and developing a theoretical description of the injection properties of oscillators that can be used to describe an injection locked laser and a microwave oscillator with a change of constants.

  13. Characterization of Microwave Mesfet Circuits Under Laser Illumination: Applications to Phased Array Radar, Microwave Communications and Digital Clock Control.

    NASA Astrophysics Data System (ADS)

    Genco, Sheryl Marie

    Optical injection of MESFETs directly affects the operating characteristics of the devices. The MESFET properties, induced by optical injection, can stabilize oscillator operating frequency, control amplifier gain and open the door for feasible integrated microwave-optical devices. The optical injection of DC MESFETs, oscillators, and amplifiers, is explored. Systems applications, including phased array radar, wave division multiplexing (WDM) and computer clock control, are provided. The main contributions of this research are analyzing the modulation properties of the locked laser subsystem, using the locked laser system to inject MESFET devices and characterizing the photo-effects in MESFET circuits, reducing the phase noise in a microwave oscillator via optical injection and developing a theoretical description of the injection properties of oscillators that can be used to describe an injection locked laser and a microwave oscillator with a change of constants.

  14. International Laser Ranging Services (ILRS) 2001 Annual Report

    NASA Technical Reports Server (NTRS)

    Pearlman, Michael (Editor); Torrence, Mark (Editor); Noll, Carey (Editor)

    2002-01-01

    This 2001 Annual Report of the International Laser Ranging Services (ILRS) is comprised of individual contributions from ILRS components within the international geodetic community. This report documents the work of the ILRS components for the year 2001. The report documents changes and progress of the ILRS. This document is also available on the ILRS Web site at http://ilrs.gsfc.nasa.gov/reports/ilrs_reports/ilrsar_2001.html.

  15. International Laser Ranging Service (ILRS) 1999 Annual Report

    NASA Technical Reports Server (NTRS)

    Pearlman, Michael (Editor); Taggert, Linda (Editor)

    2000-01-01

    This 1999 Annual Report of the International Laser Ranging Service (ILRS) is comprised of individual contributions from ILRS components within the international geodetic community. This report documents the work of the ILRS components from the inception of the Service through December 31,1999. Since the service has only recently been established, the ILRS associates decided to publish this Annual report as a reference to our organization and its components.

  16. Frequency-modulated continuous-wave laser radar using dual vertical-cavity surface-emitting laser diodes for real-time measurements of distance and radial velocity

    NASA Astrophysics Data System (ADS)

    Kakuma, Seiichi

    2017-02-01

    A frequency-modulated continuous-wave (FMCW) laser radar capable of real-time displaying the distance to a target object and its radial velocity as their corresponding frequency spectra is developed. The system employs a pair of oppositely frequency-swept vertical-cavity surface-emitting laser diodes (VCSELs). This makes possible simultaneous detection of beat signals induced by the increment (up-ramp) and decrement (down-ramp) in laser frequencies. By mixing these two beat signals, their sum and difference frequencies are directly obtained without arithmetic processing such as averaging and subtraction. Results of the test experiments adopting axially moving block gauges as target objects show that both the distance and given velocities are accurately determined from the spectrum of the frequency mixer.

  17. The irradiating field of view of imaging laser radar under fog conditions in a controlled laboratory environment

    NASA Astrophysics Data System (ADS)

    Song, Wen-Hua; Ghassemlooy, Zabih; Lai, Jian-Cheng; Yan, Wei; Wang, Chun-Yong; Li, Zhen-Hua

    2017-04-01

    This paper theoretically and experimentally investigates the performance of the imaging laser radar (ILR) system under the fog condition. Fog is generated and controlled homogeneously within a dedicated indoor atmospheric chamber. A physical model of the reflected laser pulses due to fog and a standard Lambertian target are developed to determine the width of each echo pulse for different fog concentrations. We show that there is a good agreement between the predicted and measured results for the width of backscattered return pulses. Based on experimental results an empirical model of the horizontal and vertical irradiating field of views (FOVs) of ILR under different visibilities is also developed. Consequently, a new model is proposed to predict the horizontal and vertical irradiating FOVs of ILR by using the width of the backscattered return pulse under different fog conditions. The reported results can be used to dynamically adjust the scanning interval based on the variation of the irradiating FOVs of laser radar and improve the precision of target ranging and imaging.

  18. PREFACE AND CONFERENCE INFORMATION: Eighth International Conference on Laser Ablation

    NASA Astrophysics Data System (ADS)

    Hess, Wayne P.; Herman, Peter R.; Bäuerle, Dieter; Koinuma, Hideomi

    2007-04-01

    Laser ablation encompasses a wide range of delicate to extreme light interactions with matter that present considerably challenging problems for scientists to study and understand. At the same time, laser ablation also represents a basic process of significant commercial importance in laser material processing—defining a multi-billion dollar industry today. These topics were widely addressed at the 8th International Conference on Laser Ablation (COLA), held in Banff, Canada on 11-16 September 2005. The meeting took place amongst the majestic and natural beauty of the Canadian Rocky Mountains at The Banff Centre, where delegates enjoyed many inspiring presentations and discussions in a unique campus learning environment. The conference brought together world leading scientists, students and industry representatives to examine the basic science of laser ablation and improve our understanding of the many physical, chemical and/or biological processes driven by the laser. The multi-disciplinary research presented at the meeting underlies some of our most important trends at the forefront of science and technology today that are represented in the papers collected in this volume. Here you will find new processes that are producing novel types of nanostructures and nano-materials with unusual and promising properties. Laser processes are described for delicately manipulating living cells or modifying their internal structure with unprecedented degrees of control and precision. Learn about short-pulse lasers that are driving extreme physical processes on record-fast time scales and opening new directions from material processing applications. The conference papers further highlight forefront application areas in pulsed laser deposition, nanoscience, analytical methods, materials, and microprocessing applications. Laser ablation continues to grow and evolve, touching forefront areas in science and driving new technological trends in laser processing applications. Please

  19. Internal defect localization in 980 nm ridge waveguide lasers

    NASA Astrophysics Data System (ADS)

    Díaz, L.; Eichler, H. J.; Weich, K.; Klehr, A.; Zeimer, U.

    2006-04-01

    High power lasers emitting at 980 nm are essential for pumping sources of erbium-doped fiber amplifiers (EDFAs). These are used in longer distance telecommunications. Stability and reliability of the modules are two key characteristics. The present paper investigates 'sudden random failures' of double quantum-well 980 nm high power ridge waveguide lasers implemented in EDFAs. For the inspection of the external and internal status of the device we used optical spectrum modulation experiments, electroluminescence measurements, scanning electron microscopy and cathodoluminescence investigations. The localization of internal defects is the main point of this work. Two different 'sudden random failures' were found: catastrophical optical mirror damage (COMD) and internal dark line defect (DLD) formation.

  20. Breakthrough in multichannel laser-radar technology providing thousands of high-sensitive lidar receivers on a chip

    NASA Astrophysics Data System (ADS)

    Schwarte, Rudolf M.

    2004-11-01

    The purpose of this paper is to describe a new proved multi-channel laser-radar technology which enables several thousands of high-sensitive laser-radar or lidar receivers to be integrated on a fingernail-sized CMOS-chip for fast 3D-perception and, furthermore, to explain the huge number of resulting applications and to estimate the desirable scientific, economic and society impacts. These extraordinary capabilities rely on the revolutionary improvements introduced by a smart inherently-mixing photodiode with two controllable photo-current outputs [1]. We call it PMD (Photonic Mixer Device) because the opto-electronic mixing process is accomplished directly in the photonic state, followed by an integration process to get OE-correlation and the delay of the optical echo and the modulation signal. The PMD-principle provides an unbelievable simplification, size-reduction and improvement in Multi-Channel Light Detecting and Ranging as a MC-PMD-Lidar or 3D-PMD-camera without scanner. Thanks to the competence and merit of the PMDTechnologies GmbH in cooperation with the INV of the University of Siegen finally brought the PMD in big steps to reliability and to large pixel numbers and to products with today about 20.000 lidar receivers in a 120x160 PMD-matrix, which exhibits homogenous and exquisite specifications like very constant mean value and low standard deviation compared with conventional radar receivers. This innovation may be seen as a breakthrough in the history of camera development. The "3D-camera" of today comprises more 3D-pixels in a PMD-array than, about 1970, the first CCD-cameras contained 2D-pixel in a CCD-array. Both are of similar size aside from the modulated sender with integrated LED's or laser diodes required for a homogenous illumination of the field-of-view.

  1. Thermal Distortion Measurements of a Dual Gridded Antenna Reflector with Laser Radar System Integrated to a Thermal Vacuum Test Facility

    NASA Astrophysics Data System (ADS)

    Hein, Peter Jens; Doring, Daniel; Ihle, Alexander; Reichmann, Olaf; Maeyaert, Michiel

    2014-06-01

    A dual gridded reflector for Ku-Band applications (KuDGR) with two actually gridded shells made of single and individually shaped CFRP-rods (single carbon fibre reinforced plastic) has been developed by HPS. Due to the fact that these shells are made of CFRP-rods conventional methods for coordinate and thermal-distortion (TD) measuring could not be used. Therefore, the Laser Radar system (LR) was identified as best suitable measurement method for this application.The LR was chosen during the KaDGR study performed by HPS due to its capability to measure points contactless without targets and with high precision and a great number of measurement points in a short time. Furthermore, due to the gridded structure measurement systems using interferometric patterns (ESPI, Shearography) or structured light projection could not be applied.The performance of the Laser Radar system was tested during preliminary measurements on the KuDGR bread- board model. For the first environmental tests on the engineering model, the test methods at IABG were specifically adapted and qualified in order to verify that the Laser Radar system can handle the constrains set by a thermal-vacuum (TV) test facility. During the verification test run the objectives were to verify the compatibility of the LR with the positioning with respect to the chamber, the visibility, the test facilities viewport and setup inside the chamber as well as the achievable measurement accuracy. The general compatibility could be shown and optimisations regarding test setup and better accuracy were identified. Since the active surfaces of the reflector contains a multitude of single rods all with different shapes and lengths the vibration influences of the individual facility systems onto the reflector were investigated.The LR system is widely used in industrial applications but references regarding measuring thermo-elastic distortions in a TV test facility using this method are still rare. IABG has developed and

  2. Experimental evidence of signal-optical noise interferencelike effect in underwater amplitude-modulated laser optical radar systems.

    PubMed

    Bartolini, L; De Dominicis, L; Ferri de Collibus, M; Fornetti, G; Francucci, M; Guarneri, M; Nuvoli, M; Paglia, E; Ricci, R

    2008-11-15

    We report experimental evidence that in an amplitude-modulated laser optical radar system for underwater 3D imaging the observed contrast oscillations as a function of the modulation frequency originate from an interference-like effect between target signal VT and water backscattered radiation VW. The demonstration relies on the ability to perform a direct measurement of VW in a 25 m long test tank. The proposed data processing method enables one to remove the contribution of water backscattering from the detected signal and drastically reduce signal fluctuations due to the medium. Experiments also confirm the possibility to improve the signal to optical noise ratio and contrast by increasing the modulation frequency.

  3. CHRONICLE: International forum on advanced high-power lasers and applications (AHPLA '99)

    NASA Astrophysics Data System (ADS)

    Afanas'ev, Yurii V.; Zavestovskaya, I. N.; Zvorykin, V. D.; Ionin, Andrei A.; Senatsky, Yu V.; Starodub, Aleksandr N.

    2000-05-01

    A review of reports made on the International Forum on Advanced High-Power Lasers and Applications, which was held at the beginning of November 1999 in Osaka (Japan), is presented. Five conferences were held during the forum on High-Power Laser Ablation, High-Power Lasers in Energy Engineering, High-Power Lasers in Civil Engineering and Architecture, High-Power Lasers in Manufacturing, and Advanced High-Power Lasers. The following trends in the field of high-power lasers and their applications were presented: laser fusion, laser applications in space, laser-triggered lightning, laser ablation of materials by short and ultrashort pulses, application of high-power lasers in manufacturing, application of high-power lasers in mining, laser decommissioning and decontamination of nuclear reactors, high-power solid-state and gas lasers, x-ray and free-electron lasers. One can find complete information on the forum in SPIE, vols. 3885-3889.

  4. Airborne laser scan data: a valuable tool with which to infer weather radar partial beam blockage in urban environments

    NASA Astrophysics Data System (ADS)

    Cremonini, Roberto; Moisseev, Dmitri; Chandrasekar, Venkatachalam

    2016-10-01

    High-spatial-resolution weather radar observations are of primary relevance for hydrological applications in urban areas. However, when weather radars are located within metropolitan areas, partial beam blockages and clutter by buildings can seriously affect the observations. Standard simulations with simple beam propagation models and digital elevation models (DEMs) are usually not able to evaluate buildings' contribution to partial beam blockages. In recent years airborne laser scanners (ALSs) have evolved to the state-of-the-art technique for topographic data acquisition. Providing small footprint diameters (10-30 cm), ALS data allow accurate reconstruction of buildings and forest canopy heights. Analyzing the three weather C-band radars located in the metropolitan area of Helsinki, Finland, the present study investigates the benefits of using ALS data for quantitative estimations of partial beam blockages. The results obtained applying beam standard propagation models are compared with stratiform 24 h rainfall accumulation to evaluate the effects of partial beam blockages due to constructions and trees. To provide a physical interpretation of the results, the detailed analysis of beam occultations is achieved by open spatial data sets and open-source geographic information systems.

  5. The Precision Expandable Radar Calibration Sphere (PERCS) With Applications for Laser Imaging and Ranging

    DTIC Science & Technology

    2008-09-01

    HAARP ) Facility in Alaska and the newly renovated Arecibo heater in Puerto Rico. The antenna pattern gain for ionospheric modification facilities and...HF facilities such as HAARP in Alaska, EISCAT in Norway, and Arecibo in Puerto Rico; (3) the chain of high latitude SuperDARN radars used for auroral...earth orbit and, finally, validate the PERCS concept using ground over-the-horizon (OTH) and space weather radars. The second objective is to

  6. A system for high resolution 3D mapping using laser radar and requiring no beam scanning mechanisms

    NASA Astrophysics Data System (ADS)

    Rademacher, Paul

    1988-06-01

    The inherently high angular and range resolution capabilities associated with radar systems operating at optical frequencies are at once a blessing and a curse. Standard implementations consist of very narrow field of view optical receivers operating in conjunction with laser transmitters or even narrower illumination beamwidth. While high angular resolution is thus achieved, mechanical scanning is required to gather data over extended fields of view. The many laser pulse transmissions necessary to cover the entire field of view increase the detectability of the system by enemy sensors. A system concept is proposed which, through the use of a single laser transmitter and multiple optical receivers, largely eliminate these deficiencies. Complete 3D data over a broad angular field of view and depth of field can be gathered based upon the reflections from a single transmitted laser pulse. Covert operation is enhanced as a result of the sparse laser transmissions required. The eye safety characteristics of the system are also enhanced. Proprietary coding of optical shutters in each of the multiple optical receivers permits the number of such receivers to be reduced to a very practical few. An alternative configuration of the system reduces the number of receivers required to one, at the expense of increased data acquisition time. The multiple receiver configuration is simply a parallel processing implementation of the single receiver approach. While data rate is reduced by the single receiver configuration, it still greatly exceeds that of scanning systems, and hardware complexity is also reduced significantly.

  7. Photographing Internal Fractures of the Archaeological Statues with 3D Visualization of Ground Penetrating Radar Data

    NASA Astrophysics Data System (ADS)

    Kadioglu, S.; Kadioglu, Y. K.

    2009-04-01

    PHOTOGRAPHING INTERNAL FRACTURES OF THE ARCHAEOLOGICAL STATUES WITH 3D VISUALIZATION OF GROUND PENETRATING RADAR DATA Selma KADIOGLU1 and Yusuf K. KADIOGLU2 1Ankara University, Faculty of Engineering, Department of Geophysical Engineering, 06100 Tandogan/ANKARA-TURKEY kadioglu@eng.ankara.edu.tr 2Ankara University, Faculty of Engineering, Department of Geological Engineering, 06100 Tandogan/ANKARA-TURKEY kadi@eng.ankara.edu.tr The aim of the study is to illustrate a new approach to image the discontinuities in the archaeological statues before restoration studies using ground penetrating radar (GPR) method. The method was successfully applied to detect and map the fractures and cavities of the two monument groups and lion statues in Mustafa Kemal ATATURK's tumb (ANITKABIR) in Ankara-Turkey. The tumb, which has been started to build in 1944 and completed in 1953, represents Turkish people and Ataturk, who is founder of the Republic of Turkey. Therefore this monument is very important for Turkish people. The monument groups and lion statues have been built from travertine rocks. These travertine have vesicular textures with the percent of 12. They have been mainly composed of calcite, aragonite with rare amount of plant relict and clay minerals. The concentrations of Fe, Mg, Cl and Mn may lead to verify their colours changing from white through pale green to beige. The atmospheric contamination of Ankara has been caused to cover some parts of the surface of these travertine with a thin film of Pb as blackish in colour. The micro fractures have been observed specially at the rim of the vesicular of the rocks by the polarizing microscope. Parallel two dimensional (2D) GPR profile data with 10cm profile space were acquired by RAMAC CU II system with 1600 MHz shielded antenna on the monument groups (three women, three men and 24 lion statues) and then a three dimensional (3D) data volume were built using parallel 2D GPR data. Air-filled fractures and cavities in the

  8. International laser-safety regulations: a status update

    NASA Astrophysics Data System (ADS)

    Weiner, Robert M.

    1990-07-01

    There is an increase in international laser safety requirements as part of the emphasis on world-wide standardization of products and regulations. In particular the documents which will evolve from the 1992 consolidation efforts of the European Community (EC) will impact both laser manufacturers and users. This paper provides a discussion of the current status of the various laser radiation standards. NORTH AMERICAN REQUIREMENTS United States Requirements on manufacturers from the Food and Drug Administration (FDA) have been in effect since 1975. The Center for Devices and Radiological Health (CDRH) within that agency ensures that these mandatory requirements [1] are satisfied. The CDRH regulations include the division of products into classes depending on their potential for hazard criteria for power measurement and requirements for product features labels and manuals and records and reports. Manufacturers must test products and certify that they comply with the CDRH requirements. User requirements are found in a standard published by the American National Standards Institute (ANSI) and in requirements from several individual states. Specific ANSI standards have also been published for fiber communications systems [34] and for lasers in medical applications [35]. Please note that the Appendix includes additional information on the standards discussed in this paper including sources for obtaining the documents. Canada In the past Canada has had requirements for two specified product categories (bar code scanners and educational lasers) [26 These will be replaced

  9. Laser radar studies: A study of the feasibility of remote measurement of atmospheric density and turbidity by means of rotational Raman scattering of laser light

    NASA Technical Reports Server (NTRS)

    Reiss, N.; Schotland, R. M.

    1973-01-01

    A remote sensing technique is described which utilizes elastic scattering and rotational Raman scattering of laser light in the atmosphere to obtain soundings of turbidity, transmissivity and density. A scheme is devised whereby, through selective weighting of the rotational Raman lines, the effect of atmospheric temperature structure may be eliminated. The close spectral proximity of the elastic and Raman-scattered signals, combined with the fact that the Raman scattering is quite weak, produces special requirements for the spectroscopic and light-gathering components of a rotational Raman laser radar system. These requirements are investigated. A computation of typical signal-to-noise ratios is made. It is shown that daytime signal-to-noise ratios greater than 10 db are to be expected for observation heights of 5 km and below. For nighttime work, 10 db signal-to-noise ratios are achievable to altitudes as high as 15 km.

  10. PREFACE: Second International Conference on Optical and Laser Diagnostics

    NASA Astrophysics Data System (ADS)

    Arcoumanis, C.; Grattan, K. T. V.

    2006-08-01

    The area of optical and laser diagnostics continues to expand and develop, and is now an essential part of many fields in engineering. Indeed it is one of the most interdisciplinary of the topics of today's research, impacting upon areas from fundamental physics to IT and encompassing a wide number of specific fields in engineering today. The proceedings of this, the second International Conference on Optical and Laser Diagnostics (ICOLAD 2005), follows upon the very successful first conference held in 2002, and reflects in its content many of the developments in this area since that time. The aim of a Conference which is an international forum for new ideas and developments in this exciting branch of optical engineering continues, building upon the foundation of research in optical diagnostics and optical sensing for a number of industrial and biomedical application areas at the City University, London. The Conference was structured into a number of sessions, held over three days in London, with the contributed talks led by invited papers from many internationally known and respected experts in their field from the UK, mainland Europe, the United States and Japan. The material covered includes such major themes as laser diagnostics, reciprocating engine-related applications and flow velocity measurement, extending to encompass, for example, biomedical and structural monitoring using advanced optical techniques. The papers draw their authority from the reputations of the authors and the groups and companies internationally that they represent and this volume brings together a valuable cross-section of such world-leading research. The local Organizing Committee would like to acknowledge and thank the industrial sponsors of the Conference and the members of the local and the International Steering Committee for their contribution to the success of this Conference. In particular thanks are due to Ms Claire Pantlin and the Institute of Physics for their work to make

  11. Imaging internal flows in a drying sessile polymer dispersion drop using Spectral Radar Optical Coherence Tomography (SR-OCT).

    PubMed

    Manukyan, Selin; Sauer, Hans M; Roisman, Ilia V; Baldwin, Kyle A; Fairhurst, David J; Liang, Haida; Venzmer, Joachim; Tropea, Cameron

    2013-04-01

    In this work, we present the visualization of the internal flows in a drying sessile polymer dispersion drop on hydrophilic and hydrophobic surfaces with Spectral Radar Optical Coherence Tomography (SR-OCT). We have found that surface features such as the initial contact angle and pinning of the contact line, play a crucial role on the flow direction and final shape of the dried drop. Moreover, imaging through selection of vertical slices using optical coherence tomography offers a feasible alternative compared to imaging through selection of narrow horizontal slices using confocal microscopy for turbid, barely transparent fluids.

  12. Characterization of Deep Internal Layers and Basal Conditions Around the WAIS Divide Drill Site by Surface-Based Radar

    NASA Astrophysics Data System (ADS)

    Laird, C. M.; Blake, W. A.; Gogineni, P. S.; Allen, C. T.; Leuschen, C. J.; Braaten, D. A.

    2008-12-01

    We used an ultra-wideband, very high frequency (120 to 300 MHz) surface-based radar to simultaneously map ice thickness, deep internal layers and the ice-bed interface around the West Antarctic Ice Sheet (WAIS) Divide deep drill site at a fine resolution. The radar was built by the Center for Remote Sensing of Ice Sheets (CReSIS) as part of the Polar Radar for Ice Sheet Measurements (PRISM) project with the main goal of developing and testing surface-operated radars to characterize ice thickness and bedrock conditions in Antarctica and Greenland. The system was fine-tuned in the field to a center frequency of 150 MHz with a bandwidth of 20 MHz to produce greater sensitivity. The survey covered a 30 km by 8 km area with 1-km line spacing along a polar stereographic grid that overlapped both the drill site and the WAIS Divide. The data have been processed for general use and are available on the CReSIS website (www.cresis.ku.edu). Echograms and digital ice thickness, bed elevation and bed reflectivity maps have been produced while analysis continues. Our major findings to date include: 1) internal layers are observed nearly continuously to 2800 m depth, as much as 500 m below the deepest previously mapped layers in this region, 2) internal layers have been detected to within 350 m of the bed, covering about 90% of the ice thickness, 3) ice thickness varies between approximately 3100 m and 3550 m over the grid and is about 3500 m at the drill site, 4) basal returns were mapped nearly continuously along grid lines and vary by more than 30 dB, indicating a wet bed at the drill site and frozen conditions elsewhere. The data will aid rigorous interpretations of the WAIS ice cores (including impurity records and the depth/age scale) and the morphology and evolution of the WAIS (mean annual accumulation rates, spatial extent, divide migration and volcanism). Fine-resolution information on deep internal layers, basal conditions and ice thickness/bed elevation will help

  13. Measurements of Internal Waves in the Strait of Gibraltar Using a Shore-Based Radar.

    DTIC Science & Technology

    1986-01-01

    Gregorio Parrilla, Instituto Espanol de Oceanografia , for the tide gauge data from Algeciras and Tarifa. T. H. Kinder was funded by the Office of Naval...the In- measurements made at the Windmill Hill Radar Station stituto Espanol de Oceanografia for Algeciras and Tarifa 410 during the period 22-24

  14. PREFACE: Third International Conference on Optical and Laser Diagnostics

    NASA Astrophysics Data System (ADS)

    Arcoumanis, C.; Grattan, K. T. V.

    2007-09-01

    The International Conference on Optical and Laser Diagnostics (ICOLAD 2007), held at City University in May 2007, was the third meeting in this well established series, following upon the first in 2002 and the second in 2005. During that time the area of optical and laser diagnostics has continued to develop and to expand with both the changes seen in the technology and the availability of new optical components and laser systems. The field remains one of the most interdisciplinary of the topics of today's research, impacting upon areas from fundamental physics to IT and encompassing a number of different areas in engineering today. These proceedings are a record of current practice in this area from a Conference which remains an international forum for new ideas and developments in this exciting branch of optical engineering. It builds upon the foundation of research in the broad field of optical diagnostics in a number of industrial and biomedical application areas at the City University, London. The Conference was structured into a number of sessions reflecting topical developments in engine research, optical sensing and measurement and biomedical engineering held over three days in London, with the contributed talks led by invited papers from many internationally known and respected experts in their field from mainland Europe, the United States and Japan and the UK. The material covered encompasses such major themes as laser diagnostics, reciprocating engine-related applications and flow velocity measurement, extending to include biomedical and structural monitoring using advanced optical techniques. The papers at this Conference continue to draw their authority from the reputations of the authors and the groups and companies internationally that they represent. This volume brings together a valuable cross-section of world-leading research at the time. The local Organizing Committee would like to acknowledge and thank the industrial sponsors of the Conference

  15. Hydrogen fluoride and deuterium fluoride lasers. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Mauk, S. C.

    1980-01-01

    Research cited from the international literature adresses various aspects of hydrogen fluoride and deuterium fluoride lasers. Topics covered include flows, laser outputs, molecular relaxation, molecular rotation, energy conversion efficiency, reaction kinetics, and laser materials. Continous wave and pulsed laser are considered. This updated bibliography contains 283 citations, 53 of which are new additions to the previous edition.

  16. Hydrogen fluoride and deuterium fluoride lasers. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Mauk, S. C.

    1980-01-01

    Research cited from the international literature adresses various aspects of hydrogen fluoride and deuterium fluoride lasers. Topics covered include flows, laser outputs, molecular relaxation, molecular rotation, energy conversion efficiency, reaction kinetics, and laser materials. Continous wave and pulsed laser are considered. This updated bibliography contains 283 citations, 53 of which are new additions to the previous edition.

  17. CHRONICLE: Fifth International Conference on Laser Spectroscopy (Jasper Park Lodge, Canada, June 29-July 3, 1981)

    NASA Astrophysics Data System (ADS)

    Grasyuk, Arkadii Z.; Kryukov, P. G.

    1983-01-01

    A review is given of papers presented at the Fifth International Conference on Laser Spectroscopy. The main topics at the Conference were: fundamental applications of laser spectroscopy; applications of lasers in spectroscopy; double resonance; collisional phenomena; nonlinear processes; Rydberg states; methods for investigating unstable states; cooling, trapping, and control of motion of atoms and molecules; surfaces and solids; vacuum ultraviolet; development of new lasers.

  18. A lightweight, rugged, solid state laser radar system enabled by non-mechanical electro-optic beam steerers

    NASA Astrophysics Data System (ADS)

    Davis, Scott R.; Rommel, Scott D.; Gann, Derek; Luey, Ben; Gamble, Joseph D.; Ziemkiewicz, Michael; Anderson, Mike

    2016-05-01

    There is currently a good deal of interest in developing laser radar (ladar) for autonomous navigation and collision avoidance in a wide variety of vehicles. In many of these applications, minimizing size, weight and power (SWaP) is of critical importance, particularly onboard aircraft and spacecraft where advanced imaging systems are also needed for location, alignment, and docking. In this paper, we describe the miniaturization of a powerful ladar system based on an electro-optic (EO) beamsteering device in which liquid crystal birefringence is exploited to achieve a 20° x 5° field of view (FOV) with no moving parts. This FOV will be significantly increased in future versions. In addition to scanning, the device is capable of operating in a "point and hold" mode where it locks onto a single moving object. The nonmechanical design leads to exceptionally favorable size and weight values: 1 L and < 1 kg respectively. Furthermore, these EO scanners operate without mechanical resonances or inertial effects. A demonstration was performed with a 50 kHz, 1 microjoule laser with a 2 mm beam diameter to image at a range of 100 m yielding a 2 fps frame rate limited by the pulse laser repetition rate. The fine control provided by the EO steerer results in an angle precision of 6x10-4 degrees. This FOV can be increased with discreet, non-mechanical polarization grating beamsteerers. In this paper, we will present the design, preliminary results, and planned next generation improvements.

  19. Nonlinear automatic landing control of unmanned aerial vehicles on moving platforms via a 3D laser radar

    SciTech Connect

    Hervas, Jaime Rubio; Tang, Hui; Reyhanoglu, Mahmut

    2014-12-10

    This paper presents a motion tracking and control system for automatically landing Unmanned Aerial Vehicles (UAVs) on an oscillating platform using Laser Radar (LADAR) observations. The system itself is assumed to be mounted on a ship deck. A full nonlinear mathematical model is first introduced for the UAV. The ship motion is characterized by a Fourier transform based method which includes a realistic characterization of the sea waves. LADAR observation models are introduced and an algorithm to process those observations for yielding the relative state between the vessel and the UAV is presented, from which the UAV's state relative to an inertial frame can be obtained and used for feedback purposes. A sliding mode control algorithm is derived for tracking a landing trajectory defined by a set of desired waypoints. An extended Kalman filter (EKF) is proposed to account for process and observation noises in the design of a state estimator. The effectiveness of the control algorithm is illustrated through a simulation example.

  20. Nonlinear automatic landing control of unmanned aerial vehicles on moving platforms via a 3D laser radar

    NASA Astrophysics Data System (ADS)

    Hervas, Jaime Rubio; Reyhanoglu, Mahmut; Tang, Hui

    2014-12-01

    This paper presents a motion tracking and control system for automatically landing Unmanned Aerial Vehicles (UAVs) on an oscillating platform using Laser Radar (LADAR) observations. The system itself is assumed to be mounted on a ship deck. A full nonlinear mathematical model is first introduced for the UAV. The ship motion is characterized by a Fourier transform based method which includes a realistic characterization of the sea waves. LADAR observation models are introduced and an algorithm to process those observations for yielding the relative state between the vessel and the UAV is presented, from which the UAV's state relative to an inertial frame can be obtained and used for feedback purposes. A sliding mode control algorithm is derived for tracking a landing trajectory defined by a set of desired waypoints. An extended Kalman filter (EKF) is proposed to account for process and observation noises in the design of a state estimator. The effectiveness of the control algorithm is illustrated through a simulation example.

  1. First international comparison of femtosecond laser combs at the International Bureau of Weights and Measures.

    PubMed

    Ma, Long-Sheng; Robertsson, Lennart; Picard, Susanne; Zucco, Massimo; Bi, Zhiyi; Wu, Shenghai; Windeler, Robert S

    2004-03-15

    The first international comparison of femtosecond laser combs has been carried out at the International Bureau of Weights and Measures (BIPM). Three comb systems were involved: BIPM-C1 and BIPM-C2 from the BIPM and ECNU-C1 from the East China Normal University (ECNU). The agreement among the three combs was found to be on the subhertz level in the vicinity of 563 THz. A frequency difference measurement scheme was demonstrated that is suitable for general comb comparisons.

  2. Exploratory laser experiments. [measurement of atmospheric water vapor via optical radar

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Experiments are described which were undertaken to explore the application of various dye laser methods for generating laser pulses which could be tuned over H2O absorption lines in the visible and near infrared. Specific topics discussed include: operation of a long pulse dye laser with a tunable, narrow band output at high energies near the 5915 A water vapor absorption bands; assembly and operation of a short duration dye laser near the 5915 A water vapor absorption bands; construction of a dye laser to be pumped to operate in the red and near infrared; and preliminary studies of the beam divergence of the output of the a laser-pumped system. Results are summarized.

  3. Modeling laser beam propagation through components with internal multiple reflections

    NASA Astrophysics Data System (ADS)

    Wang, Zongzhao; Zhang, Site; Wyrowski, Frank

    2015-02-01

    Component, e.g. Fabry-Perot interferometer, with internal multiple reflections plays an important role in laser technology. Its optical functionality is based on multiple reflections inside the component and the interference effect. In this paper, two electromagnetic concepts that allow the modeling of such components for general incident light are proposed. The first one is based on an iterative field tracing approach. With this approach multiple reflections through and inside the component are handled respectively. One typical example is the simulation of Newton's rings effect or the modeling of an Etalon with thickness variation because of fabrication tolerances. The other one is based on the matrix method for stratified media, which is usually used to handle optical layer systems Fabry-Perot interferometer. We present the details, demonstrate various examples and also discuss sampling issues due to the internal multiple reflections.

  4. Improved elevation change records for Antarctic ice shelves from satellite radar and laser altimetry, 1992-2012

    NASA Astrophysics Data System (ADS)

    Fricker, H.; Paolo, F. S.; Moholdt, G.; Padman, L.

    2013-12-01

    We have been working to increase accuracy, resolution and record length of satellite radar and laser altimetry over ice shelves to provide an improved data set of elevation change for studies linking ice-shelf change to oceanic- and atmospheric-forcing variability. Here, we report our recent findings, focusing on the large Filchner-Ronne (FRIS) and Ross (RIS) ice shelves. In our satellite radar altimetry (RA) analysis we use improved procedures to integrate data from multiple satellite RA missions (ERS-1, ERS-2, and Envisat) to derive long-term (~20 years) continuous records of surface elevation changes for most of Antarctica's ice shelf area. There is considerable variability in the elevation change signal on the ice shelves both in space and time, with large interannual signals that mask the long-term trend when data from only a few years are considered. In our laser altimetry analysis, we have developed a new method that uses InSAR-based velocity fields to account for ice advection between overpasses of the ICESat laser altimeter. This allows us to monitor elevation changes in a 'Lagrangian' reference frame, i.e., following specific locations on the ice shelf as they advect downstream. The Lagrangian approach reduces the noise level of the derived elevation changes and reveals clearer spatial patterns that can be transferred into basal melt/accretion rates after accounting for ice shelf strain, surface accumulation, firn air content and hydrostatic compensation. For the RIS and FRIS, we find that basal melt rates are highest around the grounding lines and near the ice shelf fronts, in agreement with oceanographic models. The maps show significant basal accretion over the central parts of FRIS, and much less basal accretion on RIS, consistent with previous studies. Although both these ice shelves are relatively stable at present, the differences in their spatial structure of basal mass balance and temporal response of dh/dt (from RA) implies that they may respond

  5. PREFACE: 22nd International Laser Physics Workshop (LPHYS'13)

    NASA Astrophysics Data System (ADS)

    Steering, LPHYS'13; Advisory; Committees, Program

    2014-03-01

    Dear Readers, The 22nd annual International Laser Physics Workshop, LPHYS'13, took place in the City of Prague, the Czech Republic. The conference gathered 387 participants from 34 countries. It was hosted by the Institute of Physics at the Academy of Sciences of the Czech Republic and the Czech Technical University in Prague. At this occasion, the LPHYS'13 Steering and the Advisory & Program Committees of the conference would like extend its sincere gratitude to Professor Miroslav Jelínek, Co-Chair and Head of the Local Organizing Committee and his team for the outstanding job performed on organizing, arranging, managing and putting in order the conference that lead to its successful resulting conclusion. As a result of scientific seminars at the Workshop, we would like to present to you the following conference proceedings published in this volume of the IOP Journal of Physics: Conference Series. Please be advised that the 23rd annual International Laser Physics Workshop (LPHYS'14) will take place from 14-18 July, 2014 in Sofia, Bulgaria, hosted by Institute of Electronics at the Bulgarian Academy of Sciences. LPHYS'13 Steering and Advisory & Program Committees

  6. EDITORIAL: 23rd International Laser Physics Workshop (LPHYS'14)

    NASA Astrophysics Data System (ADS)

    2015-03-01

    Dear Readers, The 23rd annual International Laser Physics Workshop, LPHYS'14, took place in the City of Sofia, Bulgaria. 361 participants from 35 countries attended the conference. It was hosted by the Institute of Electronics at the Bulgarian Academy of Sciences. This year's Workshop was dedicated to paying tribute to two major events: • 50th anniversary of 1964 Nobel Prize in physics, • 145th anniversary of the establishment of the Bulgarian Academy of Sciences. LPHYS'14 has been taken under the High Patronage of Rosen Plevneliev, President of the Republic of Bulgaria. The LPHYS'14 Steering Committee and the Advisory & Program Committee would like to extend their sincere gratitude to Professor Sanka Gateva (Co-Chair) and Professor Ekaterina Borisova (Head of the Local Organizing Committee) and to their team for the outstanding job performed in organizing, arranging, managing and putting in order the conference. Their combined efforts lead to a successful result. In this volume of Journal of Physics: Conference Series you will find selected proceedings of the Workshop in Sofia. Please make a note that the 24th annual International Laser Physics Workshop (LPHYS'15) will take place from August 21 to August 25, 2015 in the city of Shanghai, China hosted by Shanghai Institute of Optics and Fine Mechanics at the Chinese Academy of Sciences. With kind regards, Steering and Advisory & Program committees LPHYS'14

  7. Initial Analysis of Internal Layers in the Snow Cover of the Ross Island Region using Ground Penetrating Radar Measurements

    NASA Astrophysics Data System (ADS)

    Kruetzmann, N. C.; George, S. E.; McDonald, A. J.; Rack, W.

    2009-04-01

    In snow and ice, internal layers are created by changes in the ambient conditions at the time of deposition, and represent contrasts in density, electrical conductivity, and ice crystal orientation. By identifying and tracing internal layers in ground penetrating radar (GPR) measurements of the Antarctic snow cover, these layers can be used to measure snow accumulation over time. This is particularly relevant for determining the Antarctic mass balance, as the areal coverage can be greatly expanded from the common, but potentially unrepresentative, point measurements from firn-cores, snow pits, or stake farms. This presentation discusses high-resolution GPR data acquired at three research sites in the vicinity of Scott Base (Antarctica), each site being characterised by different snow and surface properties. The first two sites examined, are located on the flat McMurdo Ice Shelf in zones with significantly different wind and accumulation patterns. The final site is located on the lower slopes of Mt. Erebus (Ross Island), in the dry snow zone, at approximately 350m above sea level. Using a pulseEKKO PRO GPR system, data was acquired at two frequencies simultaneously (500MHz and 1GHz; wavelength in dry snow: 40cm and 20cm, respectively). At the first two sites, transects were collected in an 800m x 800m grid at 100m intervals. Due to difficult terrain, the third site was restricted to a 400m x 400m domain. Radar shots were taken at 5cm intervals along each transect. This both provides a very high horizontal data resolution, and facilitates internal horizon tracking. The acquisition time-window of 135ns allows horizon detection down to a depth of approximately 12m. In order to convert layer depth to accumulation, information on snow density derived from snow pit- and CMP-measurements was also collected. The acquired data provides high-resolution ground-truth information required for the validation of CRYOSAT-2 satellite data (launch date in 2009). An additional reason

  8. An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements

    NASA Astrophysics Data System (ADS)

    Merete Bjoland, Lindis; Belyey, Vasyl; Løvhaug, Unni Pia; La Hoz, Cesar

    2016-09-01

    Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and cusp during more than one solar cycle. Data from ESR can be used to obtain information about primary plasma parameters: electron density, electron and ion temperature, and line-of-sight plasma velocity from an altitude of about 50 and up to 1600 km. Monthly averages of electron density and temperature and ion temperature and composition are also provided by the IRI model from an altitude of 50 to 2000 km. We have compared electron density data obtained from the ESR with the predicted electron density from the IRI-2016 model. Our results show that the IRI model in general fits the ESR data well around the F2 peak height. However, the model seems to underestimate the electron density at lower altitudes, particularly during winter months. During solar minimum the model is also less accurate at higher altitudes. The purpose of this study is to validate the IRI model at polar latitudes.

  9. HI-CLASS on AEOS: a large-aperture laser radar for space surveillance/situational awareness investigations

    NASA Astrophysics Data System (ADS)

    Kovacs, Mark A.; Dryden, Gordon L.; Pohle, Richard H.; Ayers, Kirstie; Carreras, Richard A.; Crawford, Linda L.; Taft, Russell

    2001-12-01

    The Air Force Research Laboratory/Directed Energy Directorate (AFRL/DE) via the ALVA (Applications of Lidars for Vehicles with Analysis) program installed in late 2000 a wideband, 12 J 15 Hz CO2 laser radar (ladar) on the 3.67 meter aperture AEOS (Advanced Electro-Optics System) telescope. This system is part of the Maui Space Surveillance System (MSSS), on the summit of Haleakala, Maui, HI. This ladar adopts the technology successfully demonstrated by the first generation HI-CLASS (High Performance CO2) Ladar Surveillance Sensor) operating on the nearby 0.6 meter aperture Laser Beam Director (LBD) and developed under the Field Ladar Demonstration program, jointly sponsored by AFRL/DE and the Army's Space and Missile Defense Command. The moderate power (approximately 180 watts) HI-CLASS/AEOS system generates multiple, coherent waveforms for precision satellite tracking and characterization of space objects for 1 m2 targets at ranges out to 10,000 km. This system also will be used to track space objects smaller than30 cm at ranges to 2,000 km. A third application of this system is to provide data for developing satellite identification, characterization, health and status techniques. This paper will discuss the operating characteristics and innovative features of the new system. The paper will also review recent results in support of AF needs, demonstrations, experiments, as well as planned activities that directly support applications in the DoD, scientific, and commercial arenas.

  10. Measurement of Non-Linear Internal Waves and Their Interaction with Surface Waves using Coherent Real Aperture Radars

    DTIC Science & Technology

    2010-03-08

    against that from a corner reflector so that fully calibrated normalized radar cross sections , σo, could be obtained. In 2005, only VV polarized...The Normalized Radar Cross Section of the Sea for Backscatter: Part 1. Mean Levels” “The Normalized Radar Cross Section of the Sea for...The multiscale model we developed previously to explain the dependence of the normalized radar cross section (NRCS) of the sea at microwave

  11. The internal structure of sand bars on the Colorado River, Grand Canyon, as determined by ground-penetrating radar

    USGS Publications Warehouse

    Barnhardt, Walter A.; Kayen, Robert; Rubin, David; Minasian, Diane L.

    2001-01-01

    High-resolution, subsurface imagery from ground-penetrating radar (GPR) has revealed the internal structure of sand bars at seven sites on the Colorado River, Grand Canyon. Based on reconnaissance-level surveys, we recognized three stratigraphic units and several intervening unconformities. Unit A, which exhibits hyperbolic reflections and always occurs at the base of the section, is interpreted as bedrock and/or talus. Unit B is a commonly observed sand deposit that overlies unit A and is characterized by reflections that gently dip down toward the river axis. Unit C is a sand deposit up to 2 m thick that always occurs at the top of the section and may represent a flood deposit from 1983. This study demonstrates the utility of GPR for non-destructive investigation of sand-bar thickness and the stratigraphic record of flood events in the Grand Canyon.

  12. Evaluation of 3D Ground Penetrating Radar Efficiency for Abandoned Tailings Pond Internal Structure Analysis and Risk Assessment

    NASA Astrophysics Data System (ADS)

    Cortada, Unai; Martínez, Julián; Hidalgo, Mª Carmen; Rey, Javier

    2017-04-01

    Evaluation of 3D Ground Penetrating Radar Efficiency for Abandoned Tailings Pond Internal Structure Analysis and Risk Assessment Abandoned tailings ponds constitute a severe environmental problem in old Pb mining districts due to their high contents in metallic and semi-metallic elements. In most of the cases, there is a lack of information about the construction procedures and the previous environmental situation, which hinders the environmental risk evaluation. In these cases, Ground Penetrating Radar (GPR) could be an interesting technique to analyze the internal structure of the tailings ponds and detect vulnerable zones for leaching processes. Consequently, the GPR could help in the abandoned tailings ponds environmental risk assessment. In this study, a GPR 3D campaign was carried out with a 250 MHz frequency antenna in order to evaluate the efficiency of this technique in both the analysis of internal structures and the environmental risk assessment. Subsequently, 2D and 3D models were undertaken to represent graphically the obtained results. The studied tailings pond is located in the Guadiel river bank, a water course draining the mining district of Linares, Spain. The dam is 150 m length and 80 m width. The GPR 3D was done in a selected area near the central part of the pond. The analyzed grid was 25x50 m and the spacing of the slides was 1 m. The study revealed that the contact between the tailings and the substratum is located at 2.5 m. No intermediate layer was found, which means that the tailings pond was heightened on the fluvial terrace without any insulation system. Inside the first meter of the pond, a cross stratification was identified. The orientation of those laminations changed with the depth, which means that the stockpiling was performed from the different sides of the tailings pond. Furthermore, the direction of these stratifications is slightly concentric to the middle of the dam which could be associated with a central drainage system

  13. Investigation of the Glacial History of the Siple Coast Using Radar-Detected Internal Layers and the Ice Core from Siple Dome

    NASA Astrophysics Data System (ADS)

    Winebrenner, D. P.; Conway, H.; Sylvester, J.

    2002-12-01

    The spatial patterns of post-glacial thinning on the West Antarctic Ice Sheet have evidently been complex; for example, Roosevelt Island has thinned more than 300m in the past 4000 years (Conway et al., Science 286, 1999), while 300 km to the south at Siple Dome, there has been little or no thinning (Nereson and Raymond, J. Glac. 47, 2001; J. White, pers. comm., 2002). Understanding past patterns of thinning and recession of the ice sheet is a crucial step toward understanding future possible changes. Radio-echo sounding of ice reveals internal reflecting layers, most of which are thought to result from the deposition of volcanic fallout on past ice sheet surfaces, and which hence represent isochrones. The age-depth relationship form the Siple Dome ice core (Taylor et al., JGR in review, 2002) allows dating of radar layers that are continuous for more than 100 km across the Dome. However, extending the timescale across the rest of the Siple Coast is problematic because the ice streams surrounding Siple Dome have disrupted the continuity of internal layers. Here we present preliminary results on the development of methods to extrapolate spatially the age-depth relationship from Siple Dome, using core data and data from the University of Washington monopulse radar, and beginning in particular with Ridge BC. In brief, these methods are: 1) Deconvolution of (an estimate of) the radar transmit waveform from radar echograms, so as to distill out the electromagnetic response of ice that depends only on essential, rather than changeable, characteristics of the radar. 2) Correspondence of radar layers with ice core measurements on Siple Dome, which shows fairly isolated radar layers linked to electrical conductivity (ECM) and volcanic sulfate features at 150, 190, 340, and 480 meters depth. An unusually large and thick ECM event at 215m depth marks the onset of a very distinctive radar layer that can be traced entirely across Siple Dome. 3) Identification, on the basis of

  14. Snow depth determination on Arctic sea-ice using a combination of laser altimetry and radar the CryoVex 2006 experiment

    NASA Astrophysics Data System (ADS)

    Hanson, S.; Hvidegaard, S. M.; Skorup, H.; Forsberg, R.; Wilkinson, J.; Jaapala, J.; Haas, C.

    2006-12-01

    In spring 2006 a major pre-launch campaign of CryoSat-2 was carried out in the Arctic Ocean North of Greenland and Canada. The aim was to validate the airborne radar and laser instrumentation planned for the CryoSat mission. The radar which was used was the ESA 13 GHz coherent ASIRAS radar. In situ snow depths, snow physics and sea ice depth / freeboard were measured at two sites on the sea ice north of the Canadian Forces Station Alert, Ellesmere Island (82°30' N 62°19' W). Site 1 was on multiyear fast ice (MYI), approximately 5 km from the coast line. Site 2 was approximately 10 km north of Alert, on first-year ice (FYI). Data was acquired through a combination of airborne laser and radar altimetry using a Twin-Otter aircraft. By combining laser altimetry with radar waves it is possible to distinguish the sea ice surface from the snow surface and in this manner determine the snow thickness. The results show good agreement between in situ and airborne measured data. Snow cover on sea ice is an effective insulator that regulates the exchange of energy and momentum between ocean and atmosphere. The knowledge of distribution and variability of snow depth is therefore vital to our understanding of the overall heat exchange in the Arctic region. Observing climatic parameters in the Arctic region is challenged by extreme weather together with logistic constrain which demands unconventional equipment and methods to gain data. The possibility to measure snow depth from aircraft will provide an opportunity to cover huge areas and still produce a fine-scale dataset and in addition provide data for converting satellite-measured sea ice-freeboard heights to ice thickness.

  15. IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): IV International Conference on Atomic and Molecular Pulsed Gas Lasers (AMPL'99)

    NASA Astrophysics Data System (ADS)

    Evtushenko, Gennadii S.; Kopylova, T. N.; Soldatov, A. N.; Tarasenko, Viktor F.; Yakovlenko, Sergei I.; Yancharina, A. M.

    2000-06-01

    A brief review of the most interesting papers presented at the IV International Conference on Atomic and Molecular Pulsed Gas Lasers (AMPL'99), which was held in Tomsk, September 13-17, 1999, is provided.

  16. Terahertz inverse synthetic aperture radar (ISAR) imaging with a quantum cascade laser transmitter.

    PubMed

    Danylov, Andriy A; Goyette, Thomas M; Waldman, Jerry; Coulombe, Michael J; Gatesman, Andrew J; Giles, Robert H; Qian, Xifeng; Chandrayan, Neelima; Vangala, Shivashankar; Termkoa, Krongtip; Goodhue, William D; Nixon, William E

    2010-07-19

    A coherent transceiver using a THz quantum cascade (TQCL) laser as the transmitter and an optically pumped molecular laser as the local oscillator has been used, with a pair of Schottky diode mixers in the receiver and reference channels, to acquire high-resolution images of fully illuminated targets, including scale models and concealed objects. Phase stability of the received signal, sufficient to allow coherent image processing of the rotating target (in azimuth and elevation), was obtained by frequency-locking the TQCL to the free-running, highly stable optically pumped molecular laser. While the range to the target was limited by the available TQCL power (several hundred microwatts) and reasonably strong indoor atmospheric attenuation at 2.408 THz, the coherence length of the TQCL transmitter will allow coherent imaging over distances up to several hundred meters. Image data obtained with the system is presented.

  17. PREFACE: 21st International Conference on Laser Spectroscopy - ICOLS 2013

    NASA Astrophysics Data System (ADS)

    Budker, Dmitry; Häffner, Hartmut; Müller, Holger

    2013-12-01

    The 21st International Conference on Laser Spectroscopy (ICOLS) took place at Berkeley, California on 9-14 June 2013. Following the tradition of previous meetings in this series, the conference featured about thirty invited talks broadly covering this burgeoning field of science that refuses to show any sign of saturation after more than half a century of continuous boom. In addition to the invited talks, there were two informative poster sessions, where the more than 300 ICOLS participants had an opportunity to exchange the latest scientific news and ideas while enjoying the gorgeous view of the San Francisco Bay from the vista of the Claremont Hotel, the meeting's venue. The heights of the cultural program of the meeting were excursions to several of the Bay Area gems (including the Lick observatory), as well as the conference banquet where the participants were treated to addresses by an inventor of the laser Professor Charles H Townes, a nonlinear optics pioneer Professor Erwin L Hahn, and one of the previous ICOLS chairs Professor Y R Shen. While the field of Laser Spectroscopy and the series of the bi-annual ICOLS meetings are as 'healthy' as one could imagine, the same cannot be said about the concept of published conference proceedings. With new ways to publish scientific articles and preprints, submitting papers to conference proceedings seems to be rapidly losing popularity. For this meeting, the great interest in attendance and opportunities to present is sharply contrasted with a somewhat sluggish response to the call for submission of the proceedings papers. The present collection represents a dozen or so contributions from the 'hero' invited speakers, to whom we are deeply grateful for submitting their work. We hope that this selection will faithfully convey to the readers the excitement of modern laser spectroscopy. In addition to these papers, we draw the reader's attention to the audio recordings and selected viewgraphs from the invited talks, and

  18. Short-range verification experiment of a trial one-dimensional synthetic aperture infrared laser radar operated in the 10-microm band.

    PubMed

    Yoshikado, S; Aruga, T

    2000-03-20

    A trial one-dimensional (1-D) synthetic aperture infrared laser radar (SAILR) system for imaging static objects, with two CO(2) lasers as a transmitter and a local oscillator for heterodyne detection, was constructed. It has a single receiving aperture mounted on a linearly movable stage with a length of 1 m and a position accuracy of 1 microm. In an indoor short-range experiment to confirm the fundamental functions of the system and demonstrate its unique imaging process we succeeded in obtaining 1-D synthetic aperture images of close specular point targets with theoretically expected resolution.

  19. Recent advances in efficient long-life, eye-safe solid state and CO2 lasers for laser radar applications

    NASA Technical Reports Server (NTRS)

    Hess, R. V.; Buoncristiani, A. M.; Brockman, P.; Bair, C. H.; Schryer, D. R.; Upchurch, B. T.; Wood, G. M.

    1989-01-01

    The key problems in the development of eye-safe solid-state lasers are discussed, taking into account the energy transfer mechanisms between the complicated energy level manifolds of the Tm, Ho, Er ion dopants in hosts with decreasing crystal fields such as YAG or YLF. Optimization of energy transfer for efficient lasing through choice of dopant concentration, power density, crystal field and temperature is addressed. The tailoring of energy transfer times to provide efficient energy extraction for short pulses used in DIAL and Doppler lidar is considered. Recent advances in Pt/SnO2 oxide catalysts and other noble metal/metal oxide combinations for CO2 lasers are discussed. Emphasis is given to the dramatic effects of small quantities of H2O vapor for increasing the activity and lifetime of Pt/SnO2 catalysts and to increased lifetime operation with rare isotope (C-12)(O-18)2 lasing mixtures.

  20. Recent advances in efficient long-life, eye-safe solid state and CO2 lasers for laser radar applications

    NASA Technical Reports Server (NTRS)

    Hess, R. V.; Buoncristiani, A. M.; Brockman, P.; Bair, C. H.; Schryer, D. R.; Upchurch, B. T.; Wood, G. M.

    1989-01-01

    The key problems in the development of eye-safe solid-state lasers are discussed, taking into account the energy transfer mechanisms between the complicated energy level manifolds of the Tm, Ho, Er ion dopants in hosts with decreasing crystal fields such as YAG or YLF. Optimization of energy transfer for efficient lasing through choice of dopant concentration, power density, crystal field and temperature is addressed. The tailoring of energy transfer times to provide efficient energy extraction for short pulses used in DIAL and Doppler lidar is considered. Recent advances in Pt/SnO2 oxide catalysts and other noble metal/metal oxide combinations for CO2 lasers are discussed. Emphasis is given to the dramatic effects of small quantities of H2O vapor for increasing the activity and lifetime of Pt/SnO2 catalysts and to increased lifetime operation with rare isotope (C-12)(O-18)2 lasing mixtures.

  1. Synthetic Aperture Radar Imagery of Airports and Surrounding Areas: Denver Stapleton International Airport

    NASA Technical Reports Server (NTRS)

    Onstott, Robert G.; Gineris, Denise J.

    1990-01-01

    This is the third in a series of three reports which address the statistical description of ground clutter at an airport and in the surrounding area. These data are being utilized in a program to detect microbursts. Synthetic aperture radar (SAR) data were collected at the Denver Stapleton Airport using a set of parameters which closely match those which are anticipated to be utilized by an aircraft on approach to an airport. These data and the results of the clutter study are described. Scenes of 13 x 10 km were imaged at 9.38 GHz and HH-, VV-, and HV-polarizations, and contain airport grounds and facilities (up to 14 percent), cultural areas (more than 50 percent), and rural areas (up to 6 percent). Incidence angles range from 40 to 84 deg. At the largest depression angles the distributed targets, such as forest, fields, water, and residential, rarely had mean scattering coefficients greater than -10 dB. From 30 to 80 percent of an image had scattering coefficients less than -20 dB. About 1 to 10 percent of the scattering coefficients exceeded 0 dB, and from 0 to 1 percent above 10 dB. In examining the average backscatter coefficients at large angles, the clutter types cluster according to the following groups: (1) terminals (-3 dB), (2) city and industrial (-7 dB), (3) warehouse (-10 dB), (4) urban and residential (-14 dB), and (5) grass (-24 dB).

  2. The Third International Workshop on the Physics and Modern Applications of Lasers

    NASA Astrophysics Data System (ADS)

    1994-08-01

    This document contains 31 abstracts and 7 papers on lasers and optical fibers presented at the third international workshop on the physics and modern applications of lasers. The main topics covered include: basics in lasers, geometrical, physical and quantum optics; optical techniques for research, education and development in Africa; application of lasers in optical fibre communication, environmental studies, bio medicine, chemistry, agriculture, engineering and industry. A list of lecturers, participants and programme of activities are also given.

  3. Development of a Radar/SAR Assimilation System for Internal Wave Prediction

    DTIC Science & Technology

    2016-06-07

    Oceanic internal waves, particularly large non-linear ones, can have a significant impact on ship and submarine operations when they move through a...region due to the surface currents and buoyancy issues such waves induce. Thus the Navy has a need for a predictive system that can tell a ship or...the MARSAIS staff on wind and ship algorithms; we anticipate continuing this collaboration to include internal wave algorithms. We will first

  4. Proceedings of the International Conference on LASERS 󈨖 Held at New Orleans, Louisiana on December 13-17, 1982,

    DTIC Science & Technology

    This International Conference on Lasers 󈨖 was held in New Orleans, Louisiana, Dec. 13-17, 1982. More than 150 papers were presented in a wide range of topical fields related to laser development and laser applications.

  5. Towards Quantitative Optical Cross Sections in Entomological Laser Radar – Potential of Temporal and Spherical Parameterizations for Identifying Atmospheric Fauna

    PubMed Central

    Brydegaard, Mikkel

    2015-01-01

    In recent years, the field of remote sensing of birds and insects in the atmosphere (the aerial fauna) has advanced considerably, and modern electro-optic methods now allow the assessment of the abundance and fluxes of pests and beneficials on a landscape scale. These techniques have the potential to significantly increase our understanding of, and ability to quantify and manage, the ecological environment. This paper presents a concept whereby laser radar observations of atmospheric fauna can be parameterized and table values for absolute cross sections can be catalogued to allow for the study of focal species such as disease vectors and pests. Wing-beat oscillations are parameterized with a discrete set of harmonics and the spherical scatter function is parameterized by a reduced set of symmetrical spherical harmonics. A first order spherical model for insect scatter is presented and supported experimentally, showing angular dependence of wing beat harmonic content. The presented method promises to give insights into the flight heading directions of species in the atmosphere and has the potential to shed light onto the km-range spread of pests and disease vectors. PMID:26295706

  6. Research on a kind of high precision and fast signal processing algorithm for FM/CW laser radar

    NASA Astrophysics Data System (ADS)

    Xu, Xinke; Liu, Guodong; Chen, Fengdong; Liu, Bingguo; Zhuang, Zhitao; Lu, Cheng; Gan, Yu

    2014-12-01

    Range accuracy and efficiency are two important indicators for Frequency modulated continuous wave (FM/CW) laser radar, improving the accuracy and efficiency of extracting beat frequency are key factors for them. Multiple Modulation Zoom Spectrum Analysis (ZFFT) and the Chirp-Z Transform (CZT) are two widely used methods for improving frequency estimation. The paper through analyze advantages and disadvantages of these methods, proposes a high accuracy and fast signal processing method which is ZFFT-CZT, it combines advantages that ZFFT can reduce data size, and CZT can zoom in frequency of any interested band. The processing of ZFFT-CZT is following: firstly ZFFT is conducted by conducting Fourier transform on short time signal to calculate amount of frequency shift, and transforming high-frequency signal into low-frequency signal of long time sampling, then CZT is conducted by choosing any interested band to continue subdividing the spectral peaks, which can reduce picket fence effect. By simulate experiment based on ZFFT-CZT method, two closed targets at distance of 50m and 50.001m are measured, and the measurement errors are 40μm and 34μm respectively. It proved that ZFFT-CZT has a small amount of calculation, which can meet the requirement of high precision frequency extraction.

  7. Semiconducter Optical Amplifier as a Phase Modulator for Coherent Laser Radar (Preprint)

    DTIC Science & Technology

    2012-01-01

    0.5 ns Saturated Gain  G  18.5 dB  Unsaturated Gain G0 30 dB Range Resolution   R   4.8 cm  Ratio of Input Energy to  Saturation Energy Ein/Esat 0.1...limited Gaussian pulses    Amplifier Modulated  LFM  Transform Limited  FWHM  1.6 ns  20 s  0.22 ns   R   4.8 cm  4.8 cm  4.8 cm  ISLR  2.58 dB  4.02...of Radar Signal Processing, McGraw Hill, 2005.  4. Agrawal,  Govind  P.  “Self‐phase modulation and spectral broadening of optical pulses in

  8. Satellite Synthetic Aperture Radar Detection of Ocean Internal Waves in the South China Sea

    DTIC Science & Technology

    2008-09-30

    Susanto, R. D., L. Mitnik and Q. Zheng, Ocean internal waves observed in the Lombok Strait, Oceanography, 18,4, 80-87, 2005 Susanto, R.D., A.L. Gordon and...J. Sprintall, 2007: Observations and Proxies of the Surface Layer Throughflow in Lombok Strait, J. Geophys. Res.-Oceans, Vol. 112, No. C3, C03S92

  9. CHRONICLE: Fourth International Conference on Lasers and Their Applications (Leipzig, East Germany, October 19-23, 1981)

    NASA Astrophysics Data System (ADS)

    Bukhenskiĭ, M. F.; Polkovnikov, Boris F.

    1983-06-01

    A brief review is given of the more important papers presented at the Fourth International Conference on Lasers and Their Applications. The Conference topics were as follows: lasers (development of new and improvement of old types); laser thermonuclear fusion; nonlinear optics; laser spectroscopy; optoelectronics; applications of lasers in chemistry, biology, and medicine; fundamental investigations; other applications.

  10. Remote chemical monitoring in an industrial environment using eyesafe IR laser radar technologies

    NASA Astrophysics Data System (ADS)

    Pasmanik, Guerman A.; Shklovsky, E. J.; Freidman, Gennady I.; Lozhkarev, Vladimir V.; Matveyev, Alexander Z.; Shilov, Alexander A.; Yakovlev, Ivan V.; Peterson, Darrel G.; Partin, Judy K.

    1997-07-01

    The brief description of new lidar prototype for remote chemical monitoring and profiling in the 8 - 12 micron range is given. The lidar includes a Nd:YAG laser (1 J per pulse) source, optical parametrical oscillator (0.2 J per pulse), and four-wave Raman emitter (20 mJ output per pulse). The receiver consists of the hydrogen SRS cells, pumped by an additional OPO pulse. Sensitivity of this receiver reaches approximately 1000 photons per pixel. The applications of this lidar for remote detection of chemicals in atmosphere will also be discussed.

  11. Laser-driven nuclear-polarized hydrogen internal gas target

    NASA Astrophysics Data System (ADS)

    Seely, J.; Crawford, C.; Clasie, B.; Xu, W.; Dutta, D.; Gao, H.

    2006-06-01

    We report the performance of a laser-driven polarized internal hydrogen gas target (LDT) in a configuration similar to that used in scattering experiments. This target used the technique of spin-exchange optical pumping to produce nuclear spin polarized hydrogen gas that was fed into a cylindrical storage (target) cell. We present in this paper the performance of the target, methods that were tried to improve the figure-of-merit (FOM) of the target, and a Monte Carlo simulation of spin-exchange optical pumping. The dimensions of the apparatus were optimized using the simulation and the experimental results were in good agreement with the results from the simulation. The best experimental result achieved was at a hydrogen flow rate of 1.1×1018atoms/s , where the sample beam exiting the storage cell had 58.2% degree of dissociation and 50.5% polarization. Based on this measurement, the atomic fraction in the storage cell was 49.6% and the density averaged nuclear polarization was 25.0%. This represents the highest FOM for hydrogen from an LDT and is higher than the best FOM reported by atomic beam sources that used storage cells.

  12. Laser-driven nuclear-polarized hydrogen internal gas target

    SciTech Connect

    Seely, J.; Crawford, C.; Clasie, B.; Xu, W.; Dutta, D.; Gao, H.

    2006-06-15

    We report the performance of a laser-driven polarized internal hydrogen gas target (LDT) in a configuration similar to that used in scattering experiments. This target used the technique of spin-exchange optical pumping to produce nuclear spin polarized hydrogen gas that was fed into a cylindrical storage (target) cell. We present in this paper the performance of the target, methods that were tried to improve the figure-of-merit (FOM) of the target, and a Monte Carlo simulation of spin-exchange optical pumping. The dimensions of the apparatus were optimized using the simulation and the experimental results were in good agreement with the results from the simulation. The best experimental result achieved was at a hydrogen flow rate of 1.1x10{sup 18} atoms/s, where the sample beam exiting the storage cell had 58.2% degree of dissociation and 50.5% polarization. Based on this measurement, the atomic fraction in the storage cell was 49.6% and the density averaged nuclear polarization was 25.0%. This represents the highest FOM for hydrogen from an LDT and is higher than the best FOM reported by atomic beam sources that used storage cells.

  13. Under the (legal) radar screen: global health initiatives and international human rights obligations

    PubMed Central

    2012-01-01

    Background Given that many low income countries are heavily reliant on external assistance to fund their health sectors the acceptance of obligations of international assistance and cooperation with regard to the right to health (global health obligations) is insufficiently understood and studied by international health and human rights scholars. Over the past decade Global Health Initiatives, like the Global Fund to fight AIDS, Tuberculosis and Malaria (Global Fund) have adopted novel approaches to engaging with stakeholders in high and low income countries. This article explores how this experience impacted on acceptance of the international obligation to (help) fulfil the right to health beyond borders. Methods The authors conducted an extensive review of international human rights law literature, transnational legal process literature, global public health literature and grey literature pertaining to Global Health Initiatives. To complement this desk work and deepen their understanding of how and why different legal norms evolve the authors conducted 19 in-depth key informant interviews with actors engaged with three stakeholders; the European Union, the United States and Belgium. The authors then analysed the interviews through a transnational legal process lens. Results Through according value to the process of examining how and why different legal norms evolve transnational legal process offers us a tool for engaging with the dynamism of developments in global health suggesting that operationalising global health obligations could advance the right to health for all. Conclusions In many low-income countries the health sector is heavily dependent on external assistance to fulfil the right to health of people thus it is vital that policies and tools for delivering reliable, long-term assistance are developed so that the right to health for all becomes more than a dream. Our research suggests that the Global Fund experience offers lessons to build on. PMID

  14. Application of a laser radar photogoniometer in the diagnosis of osteoporosis

    NASA Astrophysics Data System (ADS)

    Eberle, Hans-Georg; Beuthan, Juergen; Dierolf, Marc; Felsenberg, Dieter; Gowin, Wolfgang; Mueller, Gerhard J.

    1998-04-01

    First results on angle dependent light scattering performed on normal and osteoporotic human bone tissue in vitro are presented. The scattering distributions are measured in cw mode as well as in time-resolved (time-gated) mode. Significant differences in the angular distribution of 675 nm laser radiation transmitted through normal or osteoporotic bones are found in cw-scattering measurements. For aspiring in situ results the transition in time-resolved measurements is needed to suppress the disturbing soft tissue signals. In this way, a characterization of the bone part is aimed by selectively recording the scattered signal in a suitable chosen time window. The measurement's principle is based on time-correlated single photon counting using a 10 ps laser diode (830 nm) and a micro channel plate- photomultiplier tube. First in vitro results on human lumbar vertebrae (L1) obtained with this equipment show a correlation between the thermal peak position and the FWHM of the scattered light pulses and the bone mineral densities determined by Dual X-ray absorptiometry. The angle dependent scattering curves give distinct indications on the bone status in transmission mode.

  15. Improvement of the technique in treatment of internal hemorrhoids with Nd:YAG laser

    NASA Astrophysics Data System (ADS)

    Bao, Xiao-qing; Zhu, Jing; Shi, Hong-Min

    2005-07-01

    Objective: To observe and study the improvement of the technique in treatment of internal hemorrhoids with Nd:YAG laser and evaluate the effective rate. Methods: 60 patients of internal hemorrhoids were treated with Nd:YAG laser (10-15mw) irradiating on the mucosa of the lesions. Results: Among 60 patients, 57 patients were primarily cured with one treatment, 3 patients were primarily cured with two treatments. The effective rate was 95% with one treatment, and it reached to 100% with two treatments. Conclusions: the improvement of the technique in treatment of internal hemorrhoids with Nd:YAG laser is effective and easy to operate.

  16. Doublet Pulse Coherent Laser Radar for Tracking of Resident Space Objects

    NASA Technical Reports Server (NTRS)

    Prasad, Narasimha S.; Rudd, Van; Shald, Scott; Sandford, Stephen; Dimarcantonio, Albert

    2014-01-01

    In this paper, the development of a long range ladar system known as ExoSPEAR at NASA Langley Research Center for tracking rapidly moving resident space objects is discussed. Based on 100 W, nanosecond class, near-IR laser, this ladar system with coherent detection technique is currently being investigated for short dwell time measurements of resident space objects (RSOs) in LEO and beyond for space surveillance applications. This unique ladar architecture is configured using a continuously agile doublet-pulse waveform scheme coupled to a closed-loop tracking and control loop approach to simultaneously achieve mm class range precision and mm/s velocity precision and hence obtain unprecedented track accuracies. Salient features of the design architecture followed by performance modeling and engagement simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar parameters are presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits are discussed.

  17. Detection on micro-Doppler effect based on 1550 nm laser coherent radar

    NASA Astrophysics Data System (ADS)

    Jun, Zhang; Yang, Sun; Zenghui, Cao; Tengfei, Sun; Tiantian, Zheng

    2014-01-01

    A laser coherent detection system of 1550 nm wavelength was presented, and experimental research on detecting micro-Doppler effect in a dynamic target was developed. In this paper, the return signal in the time domain is decomposed into a set of components in different wavelet-scales by multi-resolution analysis, and the components are associated with the vibrational motions in a target. The micro-Doppler signatures are extracted by applying the reconstruction (inverse wavelet transform). During the course of the final data processing frequency analysis and time-frequency analysis are applied to analyze the vibrational signals and estimate the motion parameters successfully. The experimental results indicate that the micro-Doppler information in a moving can be effectively detected, and tiny vibrational signatures also can be acquired effectively by wavelet multi-resolution analysis and time-frequency analysis.

  18. Planetary boundary layer (PBL) monitoring by means of two laser radar systems: experimental results and comparison

    NASA Astrophysics Data System (ADS)

    Bellecci, C.; Gaudio, P.; Gelfusa, M.; Malizia, A.; Richetta, M.; Serafini, C.; Ventura, P.

    2010-10-01

    The PBL is the lower layer of the atmosphere that is sensitive to the effect of the Earths surface, it controls the flow of heat and momentum between the surface and the free atmosphere, thus playing a key role in atmospheric circulation. At University of Rome "Tor Vergata", Quantum Electronic and Plasma Laboratories (EQP), two mobile Light Detection and Ranging (LIDAR) systems have been developed. With these systems the monitoring of the Planetary Boundary Layer (PBL) has been performed. The first mobile Lidar system is based on a pulsed Nd:YAG Q-Switched laser source operating at three wavelengths: 1064 nm, 532 nm and 355 nm. Acquiring the elastic backscattered signals, it has been possible to estimate the aerosolitic backscattering coefficient at the aim to reconstruct the vertical aerosol profiles. The second one is a Differential Absorption Lidar system (DIAL), composed by a CO2 laser, working in the window spectral range between 9 and 11μm. With this system it has been estimated the water vapour concentration in the PBL region using the two wavelengths 10R20 (10.591 μm) and 10R18 (10.571 μm), which represent, respectively, the absorbing wavelength and non-absorbing one of the water molecule. The comparison of the backscattered radiation at these wavelengths yields the trace gas number density as a function of distance along the field-of-view of the receiving telescope. Diurnal and nocturnal measurements have been performed simultaneity using the two Lidar/Dial systems. Vertical profiles of the aerosolitic backscattering coefficient and water vapour concentration profiles have been estimated. The results and their comparison will be present in this work.

  19. Internal architecture of a raised beach ridge system (Anholt, Denmark) resolved by ground-penetrating radar investigations

    NASA Astrophysics Data System (ADS)

    Clemmensen, Lars B.; Nielsen, Lars

    2010-01-01

    The internal architecture of raised beach ridge and associated swale deposits on Anholt records an ancient sea level. The Holocene beach ridges form part of a progradational beach ridge plain, which has been interpreted to have formed during an isostatic uplift and a relative fall in the sea level over the past 7700 years. The ridges are covered by pebbles and cobbles and commonly show evidence of deflation. Material presumably removed from the beach ridges and adjacent swales form the present dune forms on Anholt. Ground-penetrating radar (GPR) reflection lines have been collected with 250 MHz shielded antennae across the fossil ridge and swale structures. The signals penetrate the subsurface to a maximum depth of ˜ 10 m below the fossil features. The GPR data resolve the internal architecture of the beach ridges and swales with a vertical resolution of about 0.1 m. GPR mapping indicates that the Holocene beach ridges are composed of seaward-dipping beachface deposits as well as minor amounts of inland dipping deposits of wash-over origin. The beachface deposits downlap on underlying shoreface deposits, and we use these surfaces as markers of a relative palaeo-sea level. The new data indicate that the highest relative sea level at about 8.5 m was reached 6500 years ago; 700 years later the relative sea level had dropped 0.7 m indicating a change in the relative sea level around 1 mm/year. This fall in the relative sea level most likely records the influence of an isostatic rebound causing younger beach ridge deposits to indicate lower sea levels.

  20. Micropower impulse radar

    SciTech Connect

    Azevedo, S.; McEwan, T.E.

    1996-01-01

    Invented and developed at Lawrence Livermore National Laboratory is an inexpensive and highly sensitive, low-power radar system that produces and samples extremely short pulses of energy at the rate of 2 million per second. Called micropower impulse radar (MIR), it can detect objects at a greater variety of distances with greater sensitivity than conventional radar. Its origins in the Laboratory`s Laser Directorate stem from Nova`s transient digitizer. The MIR`s extraordinary range of applications include security, search and rescue, life support, nondestructive evaluation, and transportation.

  1. Abstracts of papers presented at the Eleventh International Laser Radar Conference

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Abstracts of 39 papers discuss measurements of properties from the Earth's ocean surface to the mesosphere, made with techniques ranging from elastic and inelastic scattering to Doppler shifts and differential absorption. Topics covered include: (1) middle atmospheric measurements; (2) meteorological parameters: temperature, density, humidity; (3) trace gases by Raman and DIAL techniques; (4) techniques and technology; (5) plume dispersion; (6) boundary layer dynamics; (7) wind measurements; visibility and aerosol properties; and (9) multiple scattering, clouds, and hydrometers.

  2. Eleventh International Laser Radar Conference, Wisconsin University-Madison, 21-25 June 1982.

    DTIC Science & Technology

    1982-06-01

    variations on water vapor profile accuracy. 2 - Generalities The measured quantity by the DIAL method is the local optical thick - ness AT (2) To derive...optimization criterion of the DIAL method,T. - 1.1 (tw integrated optical thickness between 0 and z)("), the suitable absorption lines for tropospheric...was encountered during flights on the morning of July 31, 1981. In situ and DIAL measurements resolved an optically thick layer over the entire region

  3. Doublet Pulse Coherent Laser Radar for Orbital Debris Tracking of Resident Space Objects

    NASA Astrophysics Data System (ADS)

    Prasad, N.; Rudd, V.,; DiMarcantonio, A.; Sandford, S.

    2014-09-01

    In this paper, the development of a long range ladar system known as ExoSPEAR at NASA Langley Research Center for tracking rapidly moving resident space objects is discussed. Based on 100 W, nanosecond class, near-IR laser, this ladar system with coherent detection technique is currently being investigated for short dwell time measurements of resident space objects (RSOs) in LEO and beyond for space surveillance applications. This unique ladar architecture is configured using a continuously agile doublet-pulse waveform scheme coupled to a closed-loop tracking and control loop approach to simultaneously achieve mm class range precision and mm/s velocity precision and hence obtain unprecedented track accuracies. Salient features of the design architecture followed by performance simulations illustrating the dependence of range and velocity precision in LEO orbits on ladar power aperture product will be presented. Estimated limits on detectable optical cross sections of RSOs in LEO orbits will be analyzed. The suitability of this ladar for precision orbit determination will be discussed.

  4. Miniaturized, multibeam, solid state scanning laser radar in automobile collision avoidance sensor systems

    NASA Astrophysics Data System (ADS)

    Sargent, Ronald A.

    1995-06-01

    Recent intelligent transportation systems (ITS) initiatives sponsored by commercial transportation companies and the U.S. Department of Transportation include an area dedicated to Automated Vehicle Control Systems (AVCS). AVCS systems are dedicated to improving passenger automobile safety, efficiency, and impact on the environment. Minimizing the number of automobile collisions through automated obstacle detection and vehicle response is vital to this effort. Simple, reliable, low cost sensors installed in automobiles to provide driver warning and/or input to vehicle systems such as braking or cruise control are the key piece to making this technology as common as air bags and seat belts. EPA emission regulations now require specific areas to periodically report the mix of vehicle types. These reports must include in the mix the 13 possible categories for vehicles. Simple low cost senors installed as part of the traffic management system will facilitate the determination of vehicle category. Laser Atlanta has recently developed two distinct types of sensors that utilize a unique multi- beam approach to detect `targets' that are potential hazards. They also provide range and range rate data to automobile control and traffic management systems.

  5. Coherent IR radar technology

    NASA Astrophysics Data System (ADS)

    Gschwendtner, A. B.; Harney, R. C.; Hull, R. J.

    Recent progress in the development of coherent IR radar equipment is reviewed, focusing on the Firepond laser radar installation and the more compact systems derived for it. The design and capabilities of Firepond as a long-range satellite-tracking device are outlined. The technological improvements necessary to make laser radar mobile are discussed: a lightweight, stable 5-10-W transmitter laser for both CW and pulsed operation, a 12-element HgCdTe detector array, an eccentric-pupil Ritchey-Chretien telescope, and a combination of near-field phase modification and anamorphic expansion to produce a fan beam of relatively uniform intensity. Sample images obtained with a prototype system are shown, and the applicability of the mobile system to range-resolved coherent DIAL measurement is found to be similar to that of a baseline DIAL system.

  6. An Ultra-Wideband, Microwave Radar for Measuring Snow Thickness on Sea Ice and Mapping Near-Surface Internal Layers in Polar Firn

    NASA Technical Reports Server (NTRS)

    Panzer, Ben; Gomez-Garcia, Daniel; Leuschen, Carl; Paden, John; Rodriguez-Morales, Fernando; Patel, Azsa; Markus, Thorsten; Holt, Benjamin; Gogineni, Prasad

    2013-01-01

    Sea ice is generally covered with snow, which can vary in thickness from a few centimeters to >1 m. Snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere, and it impacts sea-ice growth rates and overall thickness, a key indicator of climate change in polar regions. Snow depth is required to estimate sea-ice thickness using freeboard measurements made with satellite altimeters. The snow cover also acts as a mechanical load that depresses ice freeboard (snow and ice above sea level). Freeboard depression can result in flooding of the snow/ice interface and the formation of a thick slush layer, particularly in the Antarctic sea-ice cover. The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an ultra-wideband, microwave radar capable of operation on long-endurance aircraft to characterize the thickness of snow over sea ice. The low-power, 100mW signal is swept from 2 to 8GHz allowing the air/snow and snow/ ice interfaces to be mapped with 5 c range resolution in snow; this is an improvement over the original system that worked from 2 to 6.5 GHz. From 2009 to 2012, CReSIS successfully operated the radar on the NASA P-3B and DC-8 aircraft to collect data on snow-covered sea ice in the Arctic and Antarctic for NASA Operation IceBridge. The radar was found capable of snow depth retrievals ranging from 10cm to >1 m. We also demonstrated that this radar can be used to map near-surface internal layers in polar firn with fine range resolution. Here we describe the instrument design, characteristics and performance of the radar.

  7. Autofocus technique for three-dimensional imaging, direct-detection laser radar using Geiger-mode avalanche photodiode focal-plane array.

    PubMed

    Oh, Min Seok; Kong, Hong Jin; Kim, Tae Hoon; Jo, Sung Eun

    2010-12-15

    An autofocus technique is proposed for a three-dimensional imaging, direct-detection laser radar system that uses a Geiger-mode avalanche photodiode focal plane array (GmAPD-FPA). This technique is implemented by pointing laser pulses on a target of interest and observing its scattered photon distribution on a GmAPD-FPA. Measuring the standard deviation of the photon distribution on a GmAPD-FPA enables the best focus condition to be found. The feasibility of this technique is demonstrated experimentally by employing a 1 × 8 pixel GmAPD-FPA. It is shown that the spatial resolution improves when the GmAPD-FPA is located in the best focus position found by the autofocus technique.

  8. High-resolution laser radar: a powerful tool for 3D imaging with potential applications in artwork restoration and medical prosthesis

    NASA Astrophysics Data System (ADS)

    Fantoni, Roberta; Bordone, Andrea; Ferri De Collibus, Mario; Fornetti, Giorgio G.; Guarneri, Marianna; Poggi, Claudio; Ricci, Roberto

    2003-11-01

    A high-resolution laser radar has been developed for laboratory applications at an accurate 3D reconstruction of real objects. The laser scanner can be used to produce single cylindrical range image when the object is placed on a controlled rotating platform or, alternatively, 3 or more linear range images, in order to fully characterize the surface of the object as seen from different points of view. From the sample points, characterized by an uncertainty as small as 100 μm, the complete object surface can be reconstructed by using specifically developed software tools. The system has been successfully applied to scan different types of real surfaces (stone, wood, bones) with relevant applications in industrial machining, artwork classification and medical diagnostics. Significant examples of 3D reconstructions are shown and discussed in view of a specific utilization for reverse engineering applied to artwork restoration and medical prosthesis.

  9. Power Beaming for Space-Based Electricity on Earth: Near-Term Experiments with Radars, Lasers and Satellites

    NASA Astrophysics Data System (ADS)

    Hoffert, E.; Soukup, P.; Hoffert, M.

    2004-12-01

    Power beaming experiments thus far have been done over distances close enough where receiver apertures approximately the same diameter as transmitters can capture most of the beam (the "near- field"). The best experimentally verified wireless power transmission DC-to-DC efficiencies are 54% for a microwave transmission measured over a short distance; the longest range wireless power transmission stands at 1.6 km in 1975 (Brown, 1998; Dickinson, 1975, 2002). The next logical step is longer-range, "far-field" power beaming, particularly Space-to-Earth, or its reciprocal, Earth-to-Space, to validate beam propagation models and establish a solid experimental basis for power transmission through the atmosphere. To minimize costs, we propose adapting ground-based microwave transmitters designed for radio astronomy (Arecibo), planetary communications (NASA Deep Space Network) and detection (USAF Space Surveillance Network) for Earth-to-Space beaming tests. The receiving end could, in principle, be an NRO satellite antenna reportedly orbiting today and/or rectennas unfurled by the International Space Station (ISS). Laser SSP has lower transmission efficiency; but smaller, more flexible, and potentially cheaper components make it worth exploring. Lasers require smaller components because diffraction effects are less at optical than at microwave wavelengths The Air Force Maui Optical Station (AMOS), with facilities for accurately firing lasers through ground-based telescopes with adaptive optics at targets in space, appears ideal for laser beaming tests in conjunction with orbiting PV arrays targets. Platforms like the ISS and/or GEO communication satellites may likewise have (or could easily have) lightweight PV arrays capable of converting light to DC for end-to-end power efficiency tests. If successful, these experiments might be followed with impressive demonstrations of SSP technology such as illumination of lamps visible from Earth's surface on orbiting satellites, or

  10. Use of 3D laser radar for navigation of unmanned aerial and ground vehicles in urban and indoor environments

    NASA Astrophysics Data System (ADS)

    Uijt de Haag, Maarten; Venable, Don; Smearcheck, Mark

    2007-04-01

    This paper discusses the integration of Inertial measurements with measurements from a three-dimensional (3D) imaging sensor for position and attitude determination of unmanned aerial vehicles (UAV) and autonomous ground vehicles (AGV) in urban or indoor environments. To enable operation of UAVs and AGVs at any time in any environment a Precision Navigation, Attitude, and Time (PNAT) capability is required that is robust and not solely dependent on the Global Positioning System (GPS). In urban and indoor environments a GPS position capability may not only be unavailable due to shadowing, significant signal attenuation or multipath, but also due to intentional denial or deception. Although deep integration of GPS and Inertial Measurement Unit (IMU) data may prove to be a viable solution an alternative method is being discussed in this paper. The alternative solution is based on 3D imaging sensor technologies such as Flash Ladar (Laser Radar). Flash Ladar technology consists of a modulated laser emitter coupled with a focal plane array detector and the required optics. Like a conventional camera this sensor creates an "image" of the environment, but producing a 2D image where each pixel has associated intensity vales the flash Ladar generates an image where each pixel has an associated range and intensity value. Integration of flash Ladar with the attitude from the IMU allows creation of a 3-D scene. Current low-cost Flash Ladar technology is capable of greater than 100 x 100 pixel resolution with 5 mm depth resolution at a 30 Hz frame rate. The proposed algorithm first converts the 3D imaging sensor measurements to a point cloud of the 3D, next, significant environmental features such as planar features (walls), line features or point features (corners) are extracted and associated from one 3D imaging sensor frame to the next. Finally, characteristics of these features such as the normal or direction vectors are used to compute the platform position and attitude

  11. Development and Evaluation of New Algorithms for the Retrieval of Wind and Internal Wave Parameters from Shipborne Marine Radar Data

    DTIC Science & Technology

    2012-12-01

    110]. A good overview of radar backscattering mechanisms is given by Robinson [98]. Plant [85] provides an extensive discussion of Bragg and composite...the force exerted by IWs on a cylindrical pile. Finally, Plant et al. [91, 90] em- ployed a dual-polarized, coherent, X-band radar to study the...Eng., 33(7):974–980, 2006. [22] P. A. Catalán, M. C. Haller, R. A. Holman, and W. J. Plant . Optical and microwave detection of wave breaking in the

  12. Evaluating the potential for internal injuries from a pulsed 3.8-micron laser

    NASA Astrophysics Data System (ADS)

    Johnson, Thomas E.; Fitzhugh, Dawn C.; McPherson, Nicole; Winston, Golda C. H.; Winston, Tridaugh D.; Randolph, Donald Q.

    2005-04-01

    The goal of this study is to determine if a high energy laser pulse can cause internal injury that cannot be grossly visualized. High power lasers are currently in development such as the Medical Free Electron Laser (MFEL), the Anti-Ballistic Laser (ABL) and the Tactical High Energy Laser (THEL) and the potential exists for human exposure. Little is known about the effects of these high output lasers on internal organs when a thoracic exposure occurs. This study utilized a 3.8 micron single 8 microsecond pulse laser for all exposures. Yucatan miniature pigs were exposed to a single pulse over the sternum. In addition, some animals were also exposed in the axillary region. Creatine phosphokinase (CPK) and troponin levels were measured prior to and post exposure to assess cardiac muscle damage. Gross and histologic changes were determined for the porcine skin, lung tissue, and cardiac muscle. This study explores if a greater than class 4 laser classification is warranted based on the potential for thoracic injury.

  13. Determination of radar MTF

    SciTech Connect

    Chambers, D.

    1994-11-15

    The ultimate goal of the Current Meter Array (CMA) is to be able to compare the current patterns detected with the array with radar images of the water surface. The internal wave current patterns modulate the waves on the water surface giving a detectable modulation of the radar cross-section (RCS). The function relating the RCS modulations to the current patterns is the Modulation Transfer Function (MTF). By comparing radar images directly with co-located CMA measurements the MTF can be determined. In this talk radar images and CMA measurements from a recent experiment at Loch Linnhe, Scotland, will be used to make the first direct determination of MTF for an X and S band radar at low grazing angles. The technical problems associated with comparing radar images to CMA data will be explained and the solution method discussed. The results suggest the both current and strain rate contribute equally to the radar modulation for X band. For S band, the strain rate contributes more than the current. The magnitude of the MTF and the RCS modulations are consistent with previous estimates when the wind is blowing perpendicular to the radar look direction.

  14. Laser Radar Analyses.

    DTIC Science & Technology

    1983-07-15

    back-propagated aperture radius, Rm , in the corresponding expression (Equations (79)-(72)) of Reference 1. It should also be noted that Equation (18...incoherent detection efficiency approaches unity as Rm goes to zero and approaches zero in a limiting fashion as Rm goes to infinity, as required from the...the first two integrations reduce to the case previously treated, Equations (18) and (20), with Rm replaced by Rmi and RMO respectively. For the

  15. Frequency stabilization of internal-mirror He-Ne lasers by air cooling.

    PubMed

    Qian, Jin; Liu, Zhongyou; Shi, Chunying; Liu, Xiuying; Wang, Jianbo; Yin, Cong; Cai, Shan

    2012-09-01

    Instead of the traditional heating method, the cavity length of an internal-mirror He-Ne laser is controlled by air cooling which is implemented by a mini cooling fan. The responsive property of the cooling fan and the thermal expansion of the internal-mirror laser tube are investigated. According to these investigations, a controlling system is designed to drive the cooling fan controlling the cavity length of the laser. Then the frequency is stabilized by comparing the light intensities of two operating longitudinal modes. The results of beating with an iodine stabilized He-Ne laser show that a relative uncertainty (Δf/f-) of 4.3×10(-9) in 5 months, a frequency fluctuation of <1.4 MHz, and an Allan deviation of 6×10(-11) (τ=10,000 s) in 20 h are obtained.

  16. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Simple pulsed semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Hulicius, E.; Abrahám, A.; Sĭmeček, T.

    1988-11-01

    A brief review is given of the main characteristics of pulsed GaAlAs/GaAs lasers made in Czechoslovakia. A description is given of laser structures with large optical cavities and their electrical, optical, and service life characteristics are reported.

  17. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Surface effects in laser diodes

    NASA Astrophysics Data System (ADS)

    Beister, G.; Maege, J.; Richter, G.

    1988-11-01

    Changes in the current-voltage characteristics below the threshold current were observed in gain-guided stripe laser diodes after preliminary lasing. This effect was not fully understood. Similar changes in the laser characteristics appeared as a result of etching in a gaseous medium. The observed changes were attributed tentatively to surface currents.

  18. Noise and clutter rejection in radars and imaging sensors; Proceedings of the International Symposium, Tokyo, Japan, October 22-24, 1984

    NASA Astrophysics Data System (ADS)

    Musha, T.; Suzuki, T.; Ogura, H.

    Advanced techniques and systems for image processing and information extraction are considered along with subsurface radars, the polarization and statistical properties of clutter, characteristics of clutter properties, medical and acoustic imaging, remote sensing, radar signal processing, image processing, tracking techniques, antennas, and the imaging radar. Radar systems are discussed, taking into account radar image processing for surface aircraft recognition, clutter suppression in air traffic control radars, the Time Reference Scanning Beam (TRSB) Microwave Landing System (MLS) modelling and analysis in multipath environment, echo enhancement for a marine radar by new display techniques, compact FSK signals for radar clutter rejection, an energy efficient synthesis of an ambiguity surface, and experimental results on discrimination of radar signals by polarization. Attention is given to fast-scan processing in maritime surveillance radar, a distributed digital processing architecture for adaptive suppression of radar clutter and interference, and the noise properties of generators.

  19. Laser pulse length dependence of internal energy transfer in UV-MALDI-MS

    NASA Astrophysics Data System (ADS)

    Vertes, A.; Luo, G.; Ye, L.; Chen, Y.; Marginean, I.

    Recent internal energy (IE) measurements for various analytes in matrix-assisted laser desorption ionization (MALDI) have indicated that the amount of IE transferred to analytes not only depends on the matrix but also on the nature of the analyte. Common matrixes, such as α-cyano-4-hydroxycinnamic acid (CHCA), 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid, SA), and 2,5-dihydroxy-benzoic acid (DHB), had been characterized as ``cold'' or ``hot'' according to the IEs of analyte ions produced in the corresponding MALDI plume. In this contribution, we present evidence that IE transfer in MALDI depends on the matrix, analyte, as well as on the laser pulse properties. A substituted benzylpyridinium salt as a thermometer molecule (TM) was investigated in CHCA, SA, and DHB matrixes. A nitrogen laser (4 ns pulse length) and a mode locked frequency tripled Nd:YAG laser (22 ps pulse length) were used as excitation sources at various fluences. Survival yields (SYs) of the analyte molecular ions were extracted from the spectra and the corresponding IEs were obtained from Rice-Ramsperger-Kassel-Marcus (RRKM) theory. The SYs indicate that the IEs of analyte ions in MALDI are analyte, matrix, and laser source dependent. The ion generation threshold fluences follow the same order for both lasers: CHCAlaser source requires a higher threshold fluence than the nitrogen laser. Despite the higher fluence, the SYs are generally higher (the corresponding IEs are lower) for the 3×ω Nd:YAG laser than for the nitrogen laser. The SYs of the TM molecular ions decrease with an increase of fluence for both the ns laser and the ps laser.

  20. Internal temperature measurement of an ytterbium doped material under laser operation.

    PubMed

    Petit, J; Viana, B; Goldner, Ph

    2011-01-17

    Temperature of the pumped volume of an ytterbium doped material has been measured while laser action is taking place. This is achieved by recording green emissions at 530 and 550 nm from Er3+ impurities. These emissions result from energy transfer upconversion processes between Yb3+ and Er3+. Experiments performed on a Yb3+:CaGdAlO4 crystal show the effect of pump power and laser wavelength on the sample internal temperature. Temperature variation along the sample length has also been measured. This method can complement data obtained by thermal cameras which can only access surface temperatures in most laser materials.

  1. Radar principles

    NASA Technical Reports Server (NTRS)

    Sato, Toru

    1989-01-01

    Discussed here is a kind of radar called atmospheric radar, which has as its target clear air echoes from the earth's atmosphere produced by fluctuations of the atmospheric index of refraction. Topics reviewed include the vertical structure of the atmosphere, the radio refractive index and its fluctuations, the radar equation (a relation between transmitted and received power), radar equations for distributed targets and spectral echoes, near field correction, pulsed waveforms, the Doppler principle, and velocity field measurements.

  2. Equatorial MU Radar project

    NASA Astrophysics Data System (ADS)

    Yamamoto, Mamoru; Hashiguchi, H.; Tsuda, Toshitaka; Yamamoto, Masayuki

    Research Institute for Sustainable Humanosphere, Kyoto University (RISH) has been studying the atmosphere by using radars. The first big facility was the MU (Middle and Upper atmosphere) radar installed in Shiga, Japan in 1984. This is one of the most powerful and multi-functional radar, and is successful of revealing importance of atmospheric waves for the dynamical vertical coupling processes. The next big radar was the Equatorial Atmosphere Radar (EAR) installed at Kototabang, West Sumatra, Indonesia in 2001. The EAR was operated under close collaboration with LAPAN (Indonesia National Institute for Aeronautics and Space), and conducted the long-term continuous observations of the equatorial atmosphere/ionosphere for more than 10 years. The MU radar and the EAR are both utilized for inter-university and international collaborative research program for long time. National Institute for Polar Research (NIPR) joined EISCAT Scientific Association together with Nagoya University, and developed the PANSY radar at Syowa base in Antarctica as a joint project with University of Tokyo. These are the efforts of radar study of the atmosphere/ionosphere in the polar region. Now we can find that Japan holds a global network of big atmospheric/ionospheric radars. The EAR has the limitation of lower sensitivity compared with the other big radars shown above. RISH now proposes a plan of Equatorial MU Radar (EMU) that is to establish the MU-radar class radar next to the EAR. The EMU will have an active phased array antenna with the 163m diameter and 1055 cross-element Yagis. Total output power of the EMU will be more than 500kW. The EMU can detect turbulent echoes from the mesosphere (60-80km). In the ionosphere incoherent-scatter observations of plasma density, drift, and temperature would be possible. Multi-channel receivers will realize radar-imaging observations. The EMU is one of the key facilities in the project "Study of coupling processes in the solar-terrestrial system

  3. Internal stress distribution for generating closure domains in laser-irradiated Fe–3%Si(110) steels

    SciTech Connect

    Iwata, Keiji; Imafuku, Muneyuki; Orihara, Hideto; Sakai, Yusuke; Ohya, Shin-Ichi; Suzuki, Tamaki; Shobu, Takahisa; Akita, Koichi; Ishiyama, Kazushi

    2015-05-07

    Internal stress distribution for generating closure domains occurring in laser-irradiated Fe–3%Si(110) steels was investigated using high-energy X-ray analysis and domain theory based on the variational principle. The measured triaxial stresses inside the specimen were compressive and the stress in the rolling direction became more dominant than stresses in the other directions. The calculations based on the variational principle of magnetic energy for closure domains showed that the measured triaxial stresses made the closure domains more stable than the basic domain without closure domains. The experimental and calculation results reveal that the laser-introduced internal stresses result in the occurrence of the closure domains.

  4. International registry results for an interstitial laser BPH treatment device

    NASA Astrophysics Data System (ADS)

    Conn, Richard L.; Muschter, Rolf; Adams, Curtis S.; Esch, Victor C.

    1996-05-01

    Benign prostatic hyperplasia (BPH) can significantly impair quality of life in older men. Most men over 60 experience some symptoms due to BPH and it is thought that essentially all men would eventually be affected by it if they lived long enough. At present, transurethral resection of the prostate (TURP), a surgical treatment for BPH, is one of the more common procedures performed in the developed world, particularly in the United States. A number of other treatments are also often used, including open prostatectomy, side-firing lasers, and drug therapy. With the population in the developed world rapidly aging, BPH is expected to affect an even larger group of men in the future. Current methods of therapy carry significant disadvantages. Open prostatectomy carries a fairly high risk of impotence and incontinence, as well as sometimes significant risk of death depending on the patient's age and medical conditions. TURP also carries similar risks, albeit reduced, including the risk of substantial blood loss and a small but meaningful risk of death. Side-firing lasers are thought to have a reduced risk of death compared to TURP due to significantly reduced bleeding; however, patients often experience an extended period of pain during voiding due to prolonged tissue sloughing. Drug treatment, although useful for some patients, does not strongly improve symptoms in the majority of patients. Even with the current range of treatments, many patients with symptomatic BPH elect to avoid any current treatment due to risks and side effects. As a possible solution to this problem, previous writers have suggested the possibility of treating BPH through interstitial thermotherapy. In this treatment, prostatic tissue is heated from within the prostate to the point of irreversible necrosis. Healing processes then reduce the volume of the affected tissue, even in the absence of sloughing. This study covers initial human use of such a device, using an 810 nm wavelength diode laser

  5. Laser cooling of internal degrees of freedom of molecules

    NASA Astrophysics Data System (ADS)

    Horchani, R.

    2016-08-01

    Optical pumping techniques using laser fields combined with photo-association of ultracold atoms leads to control of the vibrational and/or rotational population of molecules. In this study, we review the basic concepts and main steps that should be followed, including the excitation schemes and detection techniques used to achieve ro-vibrational cooling of Cs2 molecules. We also discuss the extension of this technique to other molecules. In addition, we present a theoretical model used to support the experiment. These simulations can be widely used for the preparation of various experiments because they allow the optimization of several important experimental parameters.

  6. Raman Laser Spectrometer internal Optical Head current status: opto-mechanical redesign to minimize the excitation laser trace

    NASA Astrophysics Data System (ADS)

    Sanz, Miguel; Ramos, Gonzalo; Moral, Andoni; Pérez, Carlos; Belenguer, Tomás; del Rosario Canchal, María; Zuluaga, Pablo; Rodriguez, Jose Antonio; Santiago, Amaia; Rull, Fernando; Instituto Nacional de Técnica Aeroespacial (INTA), Universidad de Valladolid (UVa), Ingeniería de Sistemas para la Defesa de España S.A. (ISDEFE)

    2016-10-01

    Raman Laser Spectrometer (RLS) is the Pasteur Payload instruments of the ExoMars mission, within the ESA's Aurora Exploration Programme, that will perform for the first time in an out planetary mission Raman spectroscopy. RLS is composed by SPU (Spectrometer Unit), iOH (Internal Optical Head), and ICEU (Instrument Control and Excitation Unit). iOH focuses the excitation laser on the samples (excitation path), and collects the Raman emission from the sample (collection path, composed on collimation system and filtering system). The original design presented a high laser trace reaching to the detector, and although a certain level of laser trace was required for calibration purposes, the high level degrades the Signal to Noise Ratio confounding some Raman peaks.The investigation revealing that the laser trace was not properly filtered as well as the iOH opto-mechanical redesign are reported on. After the study of the Long Pass Filters Optical Density (OD) as a function of the filtering stage to the detector distance, a new set of filters (Notch filters) was decided to be evaluated. Finally, and in order to minimize the laser trace, a new collection path design (mainly consisting on that the collimation and filtering stages are now separated in two barrels, and on the kind of filters to be used) was required. Distance between filters and collimation stage first lens was increased, increasing the OD. With this new design and using two Notch filters, the laser trace was reduced to assumable values, as can be observed in the functional test comparison also reported on this paper.

  7. The use of airborne radar reflectometry to establish snow/firn density distribution on Devon Ice Cap, Canadian Arctic: A path to understanding complex heterogeneous internal layering patterns

    NASA Astrophysics Data System (ADS)

    Rutishauser, A.; Grima, C.; Sharp, M. J.; Blankenship, D. D.; Young, D. A.; Dowdeswell, J. A.

    2014-12-01

    The internal layer stratigraphy of polar ice sheets revealed by airborne radio-echo sounding (RES) contains valuable information about past ice sheet mass balance and dynamics. Internal layers in the Antarctic and Greenland ice sheets are considered to be isochrones and are continuous over several hundreds of kilometres. In contrast, internal layers in Canadian Arctic ice caps appear to be very heterogeneous and fragmentary, consisting of highly discontinuous layers that can be traced over only a few to several tens of kilometres. Internal layers most likely relate to former ice surfaces (the upper few meters of snow/firn), the properties which are directly influenced by atmospheric conditions including the air temperature, precipitation rate, and prevailing wind pattern. We hypothesize that the heterogeneous and complex nature of layers in the Canadian Arctic results from highly variable snow and firn conditions at the surface. Characterizing surface properties such as variations in the snow/firn density from dry to wet snow/firn, as well as high-density shallow ice layers and lenses of refrozen water can help to elucidate the complex internal layer pattern in the Canadian Arctic ice caps. Estimates of the snow/firn surface density and roughness can be derived from reflectance and scattering information using the surface radar returns from RES measurements. Here we present estimates of the surface snow/firn density distribution over Devon Ice Cap in the Canadian Arctic derived by the Radar Statistical Reconnaissance (RSR) methodology (Grima et al., 2014, Planetary & Space Sciences) using data collected by recent airborne radar sounding programs. The RSR generates estimates of the statistical distribution of surface echo amplitudes over defined areas along a survey transect. The derived distributions are best-fitted with a theoretical stochastic envelope, parameterized with the signal reflectance and scattering, in order to separate those two components. Finally

  8. Ground penetrating radar and terrestrial laser scanner surveys on deposits of dilute pyroclastic density current deposits: insights for dune bedform genesis

    NASA Astrophysics Data System (ADS)

    Rémi Dujardin, Jean; Amin Douillet, Guilhem; Abolghasem, Amir; Cordonnier, Benoit; Kueppers, Ulrich; Bano, Maksim; Dingwell, Donald B.

    2014-05-01

    Dune bedforms formed by dilute pyroclastic density currents (PDC) are often described or interpreted as antidunes and chute and pools. However, the interpretation remains essentially speculative and is not well understood. This is largely due to the seeming impossibility of in-situ measurements and experimental scaling, as well as the lack of recent, 3D exposures. Indeed, most dune bedform cross-stratifications from the dilute PDC record outcrop in 2D sections. The 2006 eruption of Tungurahua has produced well-developed bedforms that are well-exposed on the surface of the deposits with easy access. We performed a survey of these deposits combining ground penetrating radar (GPR) profiling with terrestrial laser scanning of the surface. The GPR survey was carried in dense arrays (from 10 to 25 cm spacing between profiles) over ca. 10 m long bedforms. GPR profiles were corrected for topography from photogrammetry data. An in-house software, RadLab (written in matlab), was used for common processing of individual profiles and 2D & 3D topographic migration. Each topography-corrected profile was then loaded into a seismic interpretation software, OpenDtect, for 3D visualization and interpretation. Most bedforms show high lateral stability that is independent of the cross-stratification pattern (that varies between stoss-aggrading bedsets, stoss-erosive bedsets and stoss-depositional lensoidal layers). Anecdotic bedforms have their profiles that evolve laterally (i.e. in a direction perpendicular to the flow direction). Cannibalization of two dune bedforms into a single one on one end of the profile can evolve into growth of a single bedform at the other lateral end. Also, lateral variation in the migration direction occurs, i.e. a single bedform can show upstream aggradation at one lateral end of the bedform, but show downstream migration at the other end. Some bedforms have great variations in their internal structure. Several episodes of growth and erosion can be

  9. Whither radar?

    NASA Astrophysics Data System (ADS)

    Radford, M. F.

    The evolution of radar technology in the future is examined with respect to both civilian and military applications. Consideration is given to four broad categories of radar technology where improvements in the state of the art are expected. The categories include: antenna design; transmitter design; receiver/signal processor design; and data handling/radar management technology. The influence of CAD/CAM techniques and very high performance ICs on radar system design is evaluated. A formula is presented for calculating the performance requirements of a radar system with respect to sensitivity, resolution, and optimum data rate.

  10. Comparative research and its significance of deformation measurements by technologies of laser real-time holographic interferometry and radar differential interferometry

    NASA Astrophysics Data System (ADS)

    Mao, Xian-Jin; Xu, Zhao-Young; Qian, Jia-Dong; Hu, Yi-Li; Yang, Run-Hai; Wang, Bin

    2006-05-01

    The principles and applications of laser real-time holographic interferometry (LRTHI) and radar differential interferometry (RDI) technologies are described in this paper, respectively. By using LRTHI, we can observe the deformation of samples under pressure in the lab and study the anomaly characteristics relating to different strain fields in different fracture-developing areas; while by using RDI, we can observe the landform and surface deformation. The results of deformation observed before and after the M S=7.9 Mani earthquake (Tibet) and M S=6.2 Shangyi-Zhangbei earthquake in China are obtained. It is pointed out that LRTHI and RDI are similar, which study the characteristics of anomalous deformation field by fringe variations for both of them. Therefore, the observation of deformation field in the seismogenic process, especially in the period impending an earthquake by RDI, and the comparative study in the lab by LRTHI are of great significance.

  11. Application of acoustical thermometry to noninvasive monitoring of internal temperature during laser hyperthermia

    NASA Astrophysics Data System (ADS)

    Krotov, Eugene V.; Yakovlev, Ivan V.; Zhadobov, Maxim; Reyman, Alexander M.; Zharov, Vladimir P.

    2002-06-01

    This work present the results of experimental study of applicability of acoustical brightness thermometry (ABT) in monitoring of internal temperature during laser hyperthermia and interstitial therapy. In these experiments the radiation of pulse repetition Nd:YAG laser (1064 nm) and continuous diode laser (800 nm) were used as heating sources. Experiments were performed in vitro by insertion of optical fiber inside the objects - optically transparent gelatin with incorporated light absorbing heterogeneities and samples of biological tissues (e.g. liver). During laser heating, internal temperature in absorbing heterogeneity and at fiber end were monitored by means of multi-channel ABT. The independent temperature control was performed with tiny electronic thermometer incorporated in heated zones. The results of experiments demonstrated reasonable sensitivity and accuracy of ABT for real-time temperature control during different kind of laser thermal therapies. According to preliminary data, ABT allow to measure temperature in depth up to 3-5 cm (depends on tissue properties) with spatial resolution some mm. Obtained data show that ABT is a very promising tool to give quantitative measure for different types of energy deposition (laser, microwave, focused ultrasound etc) at the depth commonly encountered in tumors of vital organs. Besides, ABT could give information about diffusion effects in heated zones or optical absorption. This work was supported by Russian Foundation for Basic Research and 6th competition-expertise of young scientists of Russian Academy of Sciences.

  12. Internal modification of glass by ultrashort laser pulse and its application to microwelding

    NASA Astrophysics Data System (ADS)

    Miyamoto, Isamu; Cvecek, Kristian; Okamoto, Yasuhiro; Schmidt, Michael

    2014-01-01

    Internal modification process of glass by ultrashort laser pulse (USLP) and its applications to microwelding of glass are presented. A simulation model is developed, which can determine intensity distribution of absorbed laser energy, nonlinear absorptivity and temperature distribution at different pulse repetition rates and pulse energies in internal modification of bulk glass with fs- and ps-laser pulses from experimental modified structure. The formation process of the dual-structured internal modification is clarified, which consists of a teardrop-shaped inner structure and an elliptical outer structure, corresponding to the laser-absorbing region and heat-affected molten region, respectively. Nonlinear absorptivity at high pulse repetition rates increases due to the increase in the thermally excited free electron density for avalanche ionization. USLP enables crack-free welding of glass because the shrinkage stress is suppressed by producing embedded molten pool by nonlinear absorption process, in contrast to conventional continuous wave laser welding where cracks cannot be avoided due to shrinkage stress produced in cooling process. Microwelding techniques of glass by USLP have been developed to join glass/glass and Si/glass using optically contacted sample pairs. The strength of the weld joint as high as that of base material is obtained without pre- and post-heating in glass/glass welding. In Si/glass welding, excellent joint performances competitive with anodic bonding in terms of joint strength and process throughput have been attained.

  13. Effect of external and internal magnetic fields on the bias stability in a Zeeman laser gyroscope

    SciTech Connect

    Kolbas, Yu Yu; Saveliev, I I; Khokhlov, N I

    2015-06-30

    With the specific features of electronic systems of a Zeeman laser gyroscope taken into account, the basic physical mechanisms of the magnetic field effect on the bias stability and the factors giving rise to the internal magnetic fields are revealed. The hardware-based methods of reducing the effect of external and internal magnetic fields are considered, as well as the algorithmic methods for increasing the stability of the bias magnetic component by taking into account its reproducible temperature and time dependences. Typical experimental temperature and time dependences of the magnetic component of the Zeeman laser gyro bias are presented, and by their example the efficiency of the proposed methods for reducing the effect of magnetic fields is shown. (laser gyroscopes)

  14. Technology development for laser-cooled clocks on the International Space Station

    NASA Technical Reports Server (NTRS)

    Klipstein, W. M.

    2003-01-01

    The PARCS experiment will use a laser-cooled cesium atomic clock operating in the microgravity environment aboard the International Space Station to provide both advanced tests of gravitational theory to demonstrate a new cold-atom clock technology for space.

  15. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Degradation phenomena in laser diodes

    NASA Astrophysics Data System (ADS)

    Beister, G.; Krispin, P.; Maege, J.; Richter, G.; Weber, H.; Rechenberg, I.

    1988-11-01

    Accelerated tests on GaAlAs/GaAs double heterostructure laser diodes showed, in agreement with earlier results on light-emitting diodes, that ageing appeared in three distinct forms: initial and slow degradation stages, both obeying a logarithmic time dependence, and a superimposed "gradation" (enhancement of the output power). Measurements made by the method of deep level transient spectroscopy during the accelerated tests on these lasers, operated as light-emitting diodes, revealed the appearance right from the beginning of B levels attributed to the antisite GaAs defects. The B levels appeared again in diodes tested in the lasing mode. In the case of a group of 21 laser diodes the mean time-to-failure was 9000 h at 70°C for 5 mW (in accordance with the Weibull statistics of degradation rates).

  16. Highly reproducible laser beam scanning device for an internal source laser desorption microprobe Fourier transform mass spectrometer

    NASA Astrophysics Data System (ADS)

    Scott, Jill R.; Tremblay, Paul L.

    2002-03-01

    Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (˜5 μm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ˜9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz's law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies.

  17. Highly Reproducible Laser Beam Scanning Device for an Internal Source Laser Desorption Microprobe Fourier Transform Mass Spectrometer

    SciTech Connect

    Scott, Jill Rennee; Tremblay, Paul Leland

    2002-03-01

    Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (~5 µm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ~9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz's law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies.

  18. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Computer model for quasioptic waveguide lasers

    NASA Astrophysics Data System (ADS)

    Wenzel, H.; Wünsche, H. J.

    1988-11-01

    A description is given of a numerical model of a semiconductor laser with a quasioptic waveguide (index guide). This model can be used on a personal computer. The model can be used to find the radiation field distributions in the vertical and lateral directions, the pump currents at the threshold, and also to solve dynamic rate equations.

  19. Synthetic aperture radar capabilities in development

    SciTech Connect

    Miller, M.

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  20. Laser-driven polarized hydrogen and deuterium internal targets

    SciTech Connect

    Jones, C.E.; Fedchak, J.A.; Kowalczyk, R.S.

    1995-08-01

    After completing comprehensive tests of the performance of the source with both hydrogen and deuterium gas, we began tests of a realistic polarized deuterium internal target. These tests involve characterizing the atomic polarization and dissociation fraction of atoms in a storage cell as a function of flow and magnetic field, and making direct measurements of the average nuclear tensor polarization of deuterium atoms in the storage cell. Transfer of polarization from the atomic electron to the nucleus as a result of D-D spin-exchange collisions was observed in deuterium, verifying calculations suggesting that high vector polarization in both hydrogen and deuterium can be obtained in a gas in spin temperature equilibrium without inducing RF transitions between the magnetic substates. In order to improve the durability of the system, the source glassware was redesigned to simplify construction and installation and eliminate stress points that led to frequent breakage. Improvements made to the nuclear polarimeter, which used the low energy {sup 3}H(d,n){sup 4}He reaction to analyze the tensor polarization of the deuterium, included installing acceleration lenses constructed of wire mesh to improve pumping conductance, construction of a new holding field coil, and elimination of the Wien filter from the setup. These changes substantially simplified operation of the polarimeter and should have reduced depolarization in collisions with the wall. However, when a number of tests failed to show an improvement of the nuclear polarization, it was discovered that extended operation of the system with a section of teflon as a getter for potassium caused the dissociation fraction to decline with time under realistic operating conditions, suggesting that teflon may not be a suitable material to eliminate potassium from the target. We are replacing the teflon surfaces with drifilm-coated ones and plan to continue tests of the polarized internal target in this configuration.

  1. Radar Polarimetry

    DTIC Science & Technology

    2004-12-01

    RADAR CROSS SECTION (RCS) σ.................................................. 15 D. THE RADAR SYSTEM...spherical surface, as [13]: rV V s iV rH H s iH E D E E D E ρ ρ = Γ = Γ (2.27) 15 C. RADAR CROSS SECTION (RCS) σ The radar cross section is...Interpretation ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ 10 01 Odd- bounce Surface, sphere, corner reflectors ⎥ ⎦ ⎤ ⎢ ⎣ ⎡ −10 01 Even-bounce Dihedral ⎥

  2. Planetary Radar

    NASA Technical Reports Server (NTRS)

    Neish, Catherine D.; Carter, Lynn M.

    2015-01-01

    This chapter describes the principles of planetary radar, and the primary scientific discoveries that have been made using this technique. The chapter starts by describing the different types of radar systems and how they are used to acquire images and accurate topography of planetary surfaces and probe their subsurface structure. It then explains how these products can be used to understand the properties of the target being investigated. Several examples of discoveries made with planetary radar are then summarized, covering solar system objects from Mercury to Saturn. Finally, opportunities for future discoveries in planetary radar are outlined and discussed.

  3. Planetary Radar

    NASA Technical Reports Server (NTRS)

    Neish, Catherine D.; Carter, Lynn M.

    2015-01-01

    This chapter describes the principles of planetary radar, and the primary scientific discoveries that have been made using this technique. The chapter starts by describing the different types of radar systems and how they are used to acquire images and accurate topography of planetary surfaces and probe their subsurface structure. It then explains how these products can be used to understand the properties of the target being investigated. Several examples of discoveries made with planetary radar are then summarized, covering solar system objects from Mercury to Saturn. Finally, opportunities for future discoveries in planetary radar are outlined and discussed.

  4. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Pulsations of light emitted by laser diodes

    NASA Astrophysics Data System (ADS)

    Enders, P.

    1988-11-01

    A system of three simple rate equations, derived from equations describing the excess heating near the front face of a resonator, is used as a model of the appearance of spontaneous (self-sustained) pulsations of light emitted by injection lasers. The rate equations are considered as an almost conservative system and the limit cycle is calculated for the system. The good agreement with numerical results favors our approximation, compared with other approximate calculations.

  5. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Transient heat conduction in laser diodes

    NASA Astrophysics Data System (ADS)

    Enders, P.; Galley, J.

    1988-11-01

    The dynamics of heat transfer in stripe GaAlAs laser diodes is investigated by solving the linear diffusion equation for a quasitwo-dimensional multilayer structure. The calculations are rationalized drastically by the transfer matrix method and also using for the first time the asymptotes of the decay constants. Special attention is given to the convergence of the Fourier series. A comparison with experimental results reveals however that this is essentially the Stefan problem (with moving boundary conditions).

  6. Multi-point laser spark generation for internal combustion engines using a spatial light modulator

    NASA Astrophysics Data System (ADS)

    Lyon, Elliott; Kuang, Zheng; Cheng, Hua; Page, Vincent; Shenton, Tom; Dearden, Geoff

    2014-11-01

    This paper reports on a technique demonstrating for the first time successful multi-point laser-induced spark generation, which is variable in three dimensions and derived from a single laser beam. Previous work on laser ignition of internal combustion engines found that simultaneously igniting in more than one location resulted in more stable and faster combustion - a key potential advantage over conventional spark ignition. However, previous approaches could only generate secondary foci at fixed locations. The work reported here is an experimental technique for multi-point laser ignition, in which several sparks with arbitrary spatial location in three dimensions are created by variable diffraction of a pulsed single laser beam source and transmission through an optical plug. The diffractive multi-beam arrays and patterns are generated using a spatial light modulator on which computer generated holograms are displayed. A gratings and lenses algorithm is used to accurately modulate the phase of the input laser beam and create multi-beam output. The underpinning theory, experimental arrangement and results obtained are presented and discussed.

  7. Internal energy deposition with silicon nanoparticle-assisted laser desorption/ionization (SPALDI) mass spectrometry

    NASA Astrophysics Data System (ADS)

    Dagan, Shai; Hua, Yimin; Boday, Dylan J.; Somogyi, Arpad; Wysocki, Ronald J.; Wysocki, Vicki H.

    2009-06-01

    The use of silicon nanoparticles for laser desorption/ionization (LDI) is a new appealing matrix-less approach for the selective and sensitive mass spectrometry of small molecules in MALDI instruments. Chemically modified silicon nanoparticles (30 nm) were previously found to require very low laser fluence in order to induce efficient LDI, which raised the question of internal energy deposition processes in that system. Here we report a comparative study of internal energy deposition from silicon nanoparticles to previously explored benzylpyridinium (BP) model compounds during LDI experiments. The internal energy deposition in silicon nanoparticle-assisted laser desorption/ionization (SPALDI) with different fluorinated linear chain modifiers (decyl, hexyl and propyl) was compared to LDI from untreated silicon nanoparticles and from the organic matrix, [alpha]-cyano-4-hydroxycinnamic acid (CHCA). The energy deposition to internal vibrational modes was evaluated by molecular ion survival curves and indicated that the ions produced by SPALDI have an internal energy threshold of 2.8-3.7 eV. This is slightly lower than the internal energy induced using the organic CHCA matrix, with similar molecular survival curves as previously reported for LDI off silicon nanowires. However, the internal energy associated with desorption/ionization from the silicon nanoparticles is significantly lower than that reported for desorption/ionization on silicon (DIOS). The measured survival yields in SPALDI gradually decrease with increasing laser fluence, contrary to reported results for silicon nanowires. The effect of modification of the silicon particle surface with semifluorinated linear chain silanes, including fluorinated decyl (C10), fluorinated hexyl (C6) and fluorinated propyl (C3) was explored too. The internal energy deposited increased with a decrease in the length of the modifier alkyl chain. Unmodified silicon particles exhibited the highest analyte internal energy

  8. Lasers '86; Proceedings of the Ninth International Conference on Lasers and Applications, Orlando, FL, Nov. 3-7, 1986

    SciTech Connect

    Mcmillan, R.W.

    1987-01-01

    Laser physics, technology, and applications are examined in reviews and reports. Topics addressed include VUV and X-ray lasers, vibrational energy transfer and kinetics, medical applications, ultrashort lasers and spectroscopy, surface and material interactions, lasers in atmospheric physics, and fiber-optic systems. Consideration is given to alexandrite lasers, four-wave mixing and nonlinear optics, chemical lasers, semiconductor lasers, photothermal and photoacoustic spectroscopy, dye lasers, optical phase conjugation and SBS, excimer lasers, SDI laser applications, remote-sensing with lasers, FELs, and applications in chemistry. Diagrams, drawings, graphs, and photographs are provided.

  9. Surface modification and laser pulse length effects on internal energy transfer in DIOS.

    PubMed

    Luo, Guanghong; Chen, Yong; Siuzdak, Gary; Vertes, Akos

    2005-12-29

    Benzyl-substituted benzylpyridinium (BP) chloride salts were used as a source of thermometer ions to probe the internal energy (IE) transfer in desorption/ionization on porous silicon (DIOS). To modify their wetting properties and the interaction energies with the thermometer ions, the DIOS surfaces were silylated to produce trimethylsilyl- (TMS), amine- (NH2), perfluoroalkyl- (PFA), and perfluorophenyl-derivatized (PFP) surfaces. Two laser sources--a nitrogen laser with pulse length of 4 ns and a mode locked 3 x omega Nd:YAG laser with a pulse length of 22 ps--were utilized to induce desorption/ionization and fragmentation at various laser fluence levels. The corresponding survival yields were determined as indicators of the IE transfer and the IE distributions were extracted. In most cases, with increasing the laser fluence in a broad range (approximately 20 mJ/cm2), no change in IE transfer was observed. For ns excitation, this was in remarkable contrast with MALDI, where increasing the laser fluence resulted in sharply (within approximately 5 mJ/cm2) declining survival yields. Derivatization of the porous silicon surface did not affect the survival yields significantly but had a discernible effect on the threshold fluence for ion production. The IE distributions determined for DIOS and MALDI from alpha-cyano-4-hydroxycinnamic acid reveal that the mean IE value is always lower for the latter. Using the ps laser, the IE distribution is always narrower for DIOS, whereas for ns laser excitation the width depends on surface modification. Most of the differences between MALDI and DIOS described here are compatible with the different dimensionality of the plume expansion and the differences in the activation energy of desorption due to surface modifications.

  10. 3D imaging of the internal structure of a rock-cored drumlin using ground-penetrating radar

    NASA Astrophysics Data System (ADS)

    King, Edward; Spagnolo, Matteo; Rea, Brice; Ely, Jeremy; Lee, Joshua

    2016-04-01

    One key question linking subglacial bedform analyses to ice dynamics relates to the flux of sediment at the bed. It is relatively easy to measure the upper surface of subglacial sediments either in active contemporary systems (using ice-penetrating radar surveys) or in relict subglacial terrain (using high-resolution digital elevation models). However, constraining the lower surface of subglacial sediments, i.e. the contact between the bedform sediment and a lower sediment unit or bedrock, is much more difficult, yet it is crucial to any determination of sediment volume and hence flux. Without observations, we are reliant on assumptions about the nature of the lower sediment surface. For example, we might assume that all the drumlins in a particular drumlin field are deposited on a planar surface, or that all comprise a carapace of till over a rock core. A calculation of sediment volume will give very different results leading to very different interpretations of sediment flux. We have been conducting experiments in the use of ground-penetrating radar to find the lower sedimentary surface beneath drumlins near Kirkby Stephen (Northern England), part of the extensive Eden Valley drumlin field. The drumlins comprise diamict overlying a bedrock surface of Carboniferous limestone which outcrops frequently between the drumlins. Here we present the results of a grid survey over one of the drumlins that clearly demonstrate this drumlin comprises a thin carapace of till overlying a stepped limestone bedrock surface. We provide details on the field data acquisition parameters and discuss the implications for further geophysical studies of drumlin fields.

  11. Frequency stabilization of internal-mirror He-Ne lasers by air cooling

    NASA Astrophysics Data System (ADS)

    Qian, Jin; Liu, Zhongyou; Shi, Chunying; Liu, Xiuying; Wang, Jianbo; Yin, Cong; Cai, Shan

    2013-01-01

    Instead of traditional heating method, the cavity length of an internal-mirror He-Ne laser is controlled by air cooling which is generated by a mini cooling fan. A PID servo controlling system is designed to drive the cooling fan tuning the frequency of the laser. The frequency is stabilized by balancing the power of two operating longitudinal modes. Beating with an iodine stabilized He-Ne laser, a relative uncertainty(Δf / ̅f ) of 4.3×10-9 in 5 months, a frequency fluctuation of less than 2.6 MHz and an Allan deviation of 3×10-11 (τ=100 s) in 75 h are obtained.

  12. Internal strain analysis of ceramics using scanning laser acoustic microscopy

    NASA Astrophysics Data System (ADS)

    Kent, Renee M.

    1993-03-01

    Quantitative studies of material behavior characteristics are essential for predicting the functionality of a material under its operating conditions. A nonintrusive methodology for measuring the in situ strain of small dimeter (to 11 microns) ceramic fibers under uniaxial tensile loading and the local internal strains of ceramics and ceramic composites under flexural loading is introduced. The strain measurements and experimentally observed mechanical behavior are analyzed in terms of the microstructural development and fracture behavior of each test specimen evaluated. Measurement and analysis of Nicalon silicon carbide (SiC) fiber (15 microns diameter) indicate that the mean elastic modulus of the individual fiber is 185.3 GPa. Deviations observed in the experimentally determined elastic modulus values between specimens were attributed to microstructural variations which occur during processing. Corresponding variations in the fracture surface morphology were also observed. The observed local mechanical behavior of a lithium alumino-silicate (LAS) glass ceramic, a LAS/SiC monofilament composite, and a calcium alumino-silicate (CAS)/SiC fully reinforced composite exhibits nonlinearities and apparent hysteresis due to the subcritical mechanical loading. Local hysteresis in the LAS matrices coincided with the occurrence of multiple fracture initiation sites, localized microcracking, and secondary cracking. The observed microcracking phenomenon was attributed to stress relaxation of residual stresses developed during processing, and local interaction of the crack front with the microstructure. The relaxation strain and stress predicted on apparent mechanical hysteresis effects were defined and correlated with the magnitude of the measured fracture stress for each specimen studied. This quantitative correlation indicated a repeatable measure of the stress at which matrix microcracking occurred for stress relief of each material system. Stress relaxation occurred

  13. Internal strain analysis of ceramics using scanning laser acoustic microscopy

    NASA Technical Reports Server (NTRS)

    Kent, Renee M.

    1993-01-01

    Quantitative studies of material behavior characteristics are essential for predicting the functionality of a material under its operating conditions. A nonintrusive methodology for measuring the in situ strain of small dimeter (to 11 microns) ceramic fibers under uniaxial tensile loading and the local internal strains of ceramics and ceramic composites under flexural loading is introduced. The strain measurements and experimentally observed mechanical behavior are analyzed in terms of the microstructural development and fracture behavior of each test specimen evaluated. Measurement and analysis of Nicalon silicon carbide (SiC) fiber (15 microns diameter) indicate that the mean elastic modulus of the individual fiber is 185.3 GPa. Deviations observed in the experimentally determined elastic modulus values between specimens were attributed to microstructural variations which occur during processing. Corresponding variations in the fracture surface morphology were also observed. The observed local mechanical behavior of a lithium alumino-silicate (LAS) glass ceramic, a LAS/SiC monofilament composite, and a calcium alumino-silicate (CAS)/SiC fully reinforced composite exhibits nonlinearities and apparent hysteresis due to the subcritical mechanical loading. Local hysteresis in the LAS matrices coincided with the occurrence of multiple fracture initiation sites, localized microcracking, and secondary cracking. The observed microcracking phenomenon was attributed to stress relaxation of residual stresses developed during processing, and local interaction of the crack front with the microstructure. The relaxation strain and stress predicted on apparent mechanical hysteresis effects were defined and correlated with the magnitude of the measured fracture stress for each specimen studied. This quantitative correlation indicated a repeatable measure of the stress at which matrix microcracking occurred for stress relief of each material system. Stress relaxation occurred

  14. Spaceborne radar

    NASA Technical Reports Server (NTRS)

    Moore, R. K.; Eckerman, J.; Meneghini, R.; Atlas, D.; Boerner, W. M.; Cherry, S.; Clark, J. F.; Doviak, R. J.; Goldhirsh, J.; Lhermitte, R. M.

    1981-01-01

    The spaceborne radar panel considered how radar could be used to measure precipitation from satellites. The emphasis was on how radar could be used with radiometry (at microwave, visible (VIS), and infrared (IR) wavelengths) to reduce the uncertainties of measuring precipitation with radiometry alone. In addition, the fundamental electromagnetic interactions involved in the measurements were discussed to determine the key work areas for research and development to produce effective instruments. Various approaches to implementing radar systems on satellites were considered for both shared and dedicated instruments. Finally, a research and development strategy was proposed for establishing the parametric relations and retrieval algorithms required for extracting precipitation information from the radar and associated radiometric data.

  15. Internal degradation of 980nm emitting single-spatial-mode lasers during ultrahigh power operation

    NASA Astrophysics Data System (ADS)

    Tomm, Jens W.; Hempel, Martin; Elsaesser, Thomas; Jimenez, Juan; Hortelano, Vanesa; Bettiati, Mauro

    2014-03-01

    Internal degradation of 980 nm emitting single-spatial-mode diode lasers during ultrahigh power operation is investigated for pulsed operation (2 μJ, 20 W). Analysis of the evolution of the emission nearfield with picosecond time resolution enables the observation of the transition from single- to multi-spatial-mode operation at elevated emission powers. Moreover, internal degradation events and subsequent defect propagation processes are in situ monitored by thermal imaging. Subsequently, these devices are opened and defect pattern are inspected by cathodo- and photoluminescence spectroscopy. The results complete earlier findings obtained with broad-area lasers and help to establish models covering defect generation and propagation in edge-emitting devices in general.

  16. Hyperspectral laser-induced flourescence imaging for assessing internal quality of kiwi fruit

    NASA Astrophysics Data System (ADS)

    Liu, Muhua; Liao, Yifeng; Zhou, Xiaomei

    2008-03-01

    This paper describes an experimental study on non-destructive methods for predicting quality of kiwifruits using fluorescence imaging. The method is based on hyperspectral laser-induced fluorescence imaging in the region between 700 and 1110 nm, and estimates the kiwifruits quality in terms of internal sugar content and firmness. A station for acquiring hyperspectral laser-induced fluorescence imaging has been designed and carefully choosing each component. The fluorescence imaging acquired by the station has been pre-processed by selecting regions of interest (ROIs) of 50 100 × pixels. A line regressing prediction method estimates the quality of kiwifruit samples. The results obtained in classification show that the station and prediction model enables the correct discrimination of kiwifruits internal sugar content and firmness with a percentage of r= 98.5%, SEP=0.4 and r=99.9%, SEP=0.62.

  17. An end pumped all internal reflection small-sized slab picosecond laser amplifier

    NASA Astrophysics Data System (ADS)

    Chen, Junchi; Peng, Yujie; Su, Hongpeng; Leng, Yuxin

    2017-05-01

    An end pumped all internal reflection small-sized slab picosecond laser system amplifier is proposed and demonstrated based on the common Nd:YAG crystal. A cylinder lens is introduced to pre-compensate for the one-dimensional thermal effect caused by the high power pumping laser. The maximum output powers of 6.6 and 6.3 W are obtained at the absorbed pumping power of 25 W without and with a cylinder mirror, and the corresponding optical conversion efficiencies are about 10.4% and 9.3% respectively. The measured M 2 factors along the slow and fast axes are 1.71 and 2.47 respectively. The instability of the maximum output laser is below 0.8% (RMS) within measuring time up to 15 min. It is demonstrated that the all internal reflection slab can support long enough optical gain distance to realize the signal laser amplification for the newly developed crystal even with small size and low doped concentration.

  18. Comet Radar Explorer

    NASA Astrophysics Data System (ADS)

    Asphaug, Erik; CORE Science Team

    2010-10-01

    Comet Radar Explorer (CORE) is a low cost mission that uses sounding radar to image the 3D internal structure of the nucleus of Jupiter-family comet (JFC) Tempel 2. Believed to originate in the Kuiper Belt, JFCs are among the most primitive bodies in the inner solar system. CORE operates a 5 and 15 MHz Radar Reflection Imager from close orbit about the nucleus of Tempel 2, obtaining a dense network of echoes that are used to map its interior dielectric contrasts to high resolution (ង m) and resolve the dielectric constants to  m throughout the 16x8x9 km nucleus. The resulting clear images of internal structure and composition reveal how the nucleus was formed and how it has evolved. Radiometric tracking of the spacecraft orbit results in an interior mass distribution that constrains the radar-based models of interior composition. High-resolution visible and infrared color images provide the surface and exterior boundary conditions for interior models and hypotheses. They present the geology and morphology of the nucleus surface at meter-scales, and also the time-evolving activity, structure and composition of the inner coma. By making deep connections from interior to exterior, the data CORE provides will answer fundamental questions about the earliest stages of planetesimal evolution and planet formation, and lay the foundation for a comet nucleus sample return mission. CORE is led by Prof. Erik Asphaug of the University of California, Santa Cruz and is managed by JPL. It benefits from key scientific and payload contributions by ASI and CNES. The international science team has been assembled on the basis of their key involvement in past and ongoing missions to comets, and in Mars radar missions, and for their expertise in radar data analysis.

  19. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  20. Lasers.

    ERIC Educational Resources Information Center

    Schewe, Phillip F.

    1981-01-01

    Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

  1. Lasers '85; Proceedings of the Eighth International Conference, Las Vegas, NV, Dec. 2-6, 1985

    SciTech Connect

    Wang, C.P.

    1986-01-01

    The present conference on laser technology development encompasses issues in such areas as VUV and X-ray lasers; optical phase conjugation and nonlinear optics; laser applications in medicine; methods for optical processing; laser and nonlinear spectroscopy; ultrashort-pulse lasers and their applications; frequency selection in pulsed lasers; and interactions between laser beams, material surfaces, and material volumes. Also treated are laser applications in the Strategic Defense Initiative program, chemical laser design and performance, the lasing of biophysical materials, laser diagnostics in fluids and plasma, semiconductor laser diodes and arrays, solid state lasers, radiation- and solar-pumped lasers, laser cavities and propagation, remote sensing with lasers and fiber-optics, coupled resonators and diode lasers, industrial applications of lasers, excimer lasers, optoelectronics, CO/sub 2/ lasers, fiber-optic sensors, alexandrite lasers, free electron lasers, and IR and visible wavelength lasers.

  2. International Conference on Lasers '82, New Orleans, LA, December 13-17, 1982, Proceedings

    NASA Astrophysics Data System (ADS)

    Powell, R. C.

    Subjects are discussed which are related to phase conjugation, laser chemistry, laser induced ionization, free electron lasers and masers, applications of lasers in nuclear physics, solid state laser materials, laser applications of collisions and dissociation phenomena, excimer lasers, tunable coherent UV radiation, laser assisted collisions, cavities and propagation, chemically pumped iodine atom lasers, lasers in medicine, blue-green and metal vapor lasers, accelerators using laser light, and X-ray lasers and coherent X-ray optics. Other areas considered are connected with tunable IR lasers, fiber optical communications, infrared molecular lasers, modern laser spectroscopy, polarization, diatomic optically-pumped lasers, combustion and plasma diagnostics, collective atomic phenomena, multiphoton processes, photophysics of complex molecules, and lasers and atmospheric sciences. Attention is also given to laser action in emerald, operating conditions for the hydrogen/deuterium triplet lasers, longitudinal electron-beam pumped rare gas-halide excimer lasers, and UV laser induced chemistry of stilbene.

  3. Study of Internal Channel Surface Roughnesses Manufactured by Selective Laser Melting in Aluminum and Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Pakkanen, Jukka; Calignano, Flaviana; Trevisan, Francesco; Lorusso, Massimo; Ambrosio, Elisa Paola; Manfredi, Diego; Fino, Paolo

    2016-08-01

    Interest in additive manufacturing (AM) has gained considerable impetus over the past decade. One of the driving factors for AM success is the ability to create unique designs with intrinsic characteristics as, e.g., internal channels used for hydraulic components, cooling channels, and heat exchangers. However, a couple of the main problems in internal channels manufactured by AM technologies are the high surface roughness obtained and the distortion of the channel shape. There is still much to understand in these design aspects. In this study, a cylindrical geometry for internal channels to be built with different angles with respect to the building plane in AlSi10Mg and Ti6Al4V alloys by selective laser melting was considered. The internal surfaces of the channels produced in both materials were analyzed by means of a surface roughness tester and by optical and electron microscopy to evaluate the effects of the material and design choices.

  4. International Semiconductor Laser Conference. Held in Boston, Massachusetts on August 29 - September 1, 1988

    DTIC Science & Technology

    1988-11-01

    gitudinal mode (SLM) laser, we make the cavity length (L) short and the coupling coefficient (K ) large, since the internal ab- sorption loss is...BaTiO3 crystal in a self- pumped internal ring geometry. The beam intensity profile incident on the conjugator is shown in Fig. 2a. This is an image of...composition. Non-radiative recombination via the L minimum in the wells makes only a small contribution to the current even for lifetimes as short as I

  5. Femtosecond superradiance in semiconductor lasers: anomalous internal second-harmonic generation

    NASA Astrophysics Data System (ADS)

    Vasil'ev, P. P.; Putilin, A. N.; Sergeev, A. B.

    2016-10-01

    The emission of anomalously bright blue light under internal doubling of the frequency of femtosecond superradiance pulses in the active medium of semiconductor GaAs/AlGaAs laser heterostructures has been experimentally found. The efficiency of the internal second-harmonic generation is an order of magnitude higher than in the conventional lasing regime. This effect is due to the formation of a transient ordered state of electrons and holes under superradiance, occurrence of dynamic coherent population lattices, and periodic modulation of the nonlinear susceptibility of the medium.

  6. Studies on remote sensing method of particle size and water density distribution in mists and clouds using laser radar techniques

    NASA Technical Reports Server (NTRS)

    Shimizu, H.; Kobayasi, T.; Inaba, H.

    1979-01-01

    A method of remote measurement of the particle size and density distribution of water droplets was developed. In this method, the size of droplets is measured from the Mie scattering parameter which is defined as the total-to-backscattering ratio of the laser beam. The water density distribution is obtained by a combination of the Mie scattering parameter and the extinction coefficient of the laser beam. This method was examined experimentally for the mist generated by an ultrasonic mist generator and applied to clouds containing rain and snow. Compared with the conventional sampling method, the present method has advantages of remote measurement capability and improvement in accuracy.

  7. Proposed method for internal electron therapy based on high-intensity laser acceleration

    NASA Astrophysics Data System (ADS)

    Tepper, Michal; Barkai, Uri; Gannot, Israel

    2015-05-01

    Radiotherapy is one of the main methods to treat cancer. However, due to the propagation pattern of high-energy photons in tissue and their inability to discriminate between healthy and malignant tissues, healthy tissues may also be damaged, causing undesired side effects. A possible method for internal electron therapy, based on laser acceleration of electrons inside the patient's body, is suggested. In this method, an optical waveguide, optimized for high intensities, is used to transmit the laser radiation and accelerate electrons toward the tumor. The radiation profile can be manipulated in order to create a patient-specific radiation treatment profile by changing the laser characteristics. The propagation pattern of electrons in tissues minimizes the side effects caused to healthy tissues. A simulation was developed to demonstrate the use of this method, calculating the trajectories of the accelerated electron as a function of laser properties. The simulation was validated by comparison to theory, showing a good fit for laser intensities of up to 2×1020 (W/cm2), and was then used to calculate suggested treatment profiles for two tumor test cases (with and without penetration to the tumor). The results show that treatment profiles can be designed to cover tumor area with minimal damage to adjacent tissues.

  8. Internal structure of laser supported detonation waves by two-wavelength Mach-Zehnder interferometer

    SciTech Connect

    Shimamura, Kohei; Kawamura, Koichi; Fukuda, Akio; Wang Bin; Yamaguchi, Toshikazu; Komurasaki, Kimiya; Hatai, Keigo; Fukui, Akihiro; Arakawa, Yoshihiro

    2011-04-15

    Characteristics of the internal structure of the laser supported detonation (LSD) waves, such as the electron density n{sub e} and the electron temperature T{sub e} profiles behind the shock wave were measured using a two-wavelength Mach-Zehnder interferometer along with emission spectroscopy. A TEA CO{sub 2} laser with energy of 10 J/pulse produced explosive laser heating in atmospheric air. Results show that the peak values of n{sub e} and T{sub e} were, respectively, about 2 x 10{sup 24} m{sup -3} and 30 000 K, during the LSD regime. The temporal variation of the laser absorption coefficient profile estimated from the measured properties reveals that the laser energy was absorbed perfectly in a thin layer behind the shock wave during the LSD regime, as predicted by Raizer's LSD model. However, the absorption layer was much thinner than a plasma layer, the situation of which was not considered in Raizer's model. The measured n{sub e} at the shock front was not zero while the LSD was supported, which implies that the precursor electrons exist ahead of the shock wave.

  9. One-step femtosecond laser welding and internal machining of three glass substrates

    NASA Astrophysics Data System (ADS)

    Tan, Hua; Duan, Ji'an

    2017-05-01

    In this paper, it demonstrated one-step femtosecond laser welding and internal machining of three fused silica substrates in the optical- and non-optical-contact regimes by focusing 1030-nm laser pulses at the middle of the second substrate. Focusing laser pulses within the second glass in optical-contact and non-optical-contact samples induces permanent internal structural modification, leading to the three glass substrates bonding together simultaneously. The bonding mechanism is based on the internal modification of glass, and this mechanism is different from that of ordinary glass welding at the interface. Welding-spot size is affected by not only the gap distance (ablation effect) and heat transmission, but also by gravity through examining the sizes of the welding spots on the four contact welding surfaces. The maximum bonding strength of the lower interface (56.2 MPa) in the optical-contact regime is more than double that (27.6 MPa) in the non-optical-contact regime.

  10. Radar research at the University of Kansas

    NASA Astrophysics Data System (ADS)

    Blunt, Shannon D.; Allen, Christopher; Arnold, Emily; Hale, Richard; Hui, Rongqing; Keshmiri, Shahriar; Leuschen, Carlton; Li, Jilu; Paden, John; Rodriguez-Morales, Fernando; Salandrino, Alessandro; Stiles, James

    2017-05-01

    Radar research has been synonymous with the University of Kansas (KU) for over half a century. As part of this special session organized to highlight significant radar programs in academia, this paper surveys recent and ongoing work at KU. This work encompasses a wide breadth of sensing applications including the remote sensing of ice sheets, autonomous navigation methods for unmanned aerial vehicles (UAVs), novel laser radar capabilities, detection of highenergy cosmic rays using bistatic radar, different forms of waveform diversity such as MIMO radar and pulse agility, and various radar-embedded communication methods. The results of these efforts impact our understanding of the changing nature of the environment, address the proliferation of unmanned systems in the US airspace, realize new sensing modalities enabled by the joint consideration of electromagnetics and signal processing, and greater facilitate radar operation in an increasingly congested and contested spectrum.

  11. Direct Global Measurements of Tropspheric Winds Employing a Simplified Coherent Laser Radar using Fully Scalable Technology and Technique

    NASA Technical Reports Server (NTRS)

    Kavaya, Michael J.; Spiers, Gary D.; Lobl, Elena S.; Rothermel, Jeff; Keller, Vernon W.

    1996-01-01

    Innovative designs of a space-based laser remote sensing 'wind machine' are presented. These designs seek compatibility with the traditionally conflicting constraints of high scientific value and low total mission cost. Mission cost is reduced by moving to smaller, lighter, more off-the-shelf instrument designs which can be accommodated on smaller launch vehicles.

  12. Laser doppler and radar interferometer for contactless measurements on unaccessible tie-rods on monumental buildings: Santa Maria della Consolazione Temple in Todi

    NASA Astrophysics Data System (ADS)

    Gioffré, M.; Cavalagli, N.; Pepi, C.; Trequattrini, M.

    2017-01-01

    Non-contact measurements can be effectively used in civil engineering to assess the variation of structural performance with time. In the last decades this approach has received considerable interests from researchers working in the field of structural health monitoring (SHM). Indeed, non-contact measurements are very attractive because it is possible to perform non intrusive and non destructive investigations even being at a significant distance from the targets. Within this context, contactless measurements of the tie-rod vibrations in the Santa Maria della Consolazione Temple in Todi (Italy) are presented in this paper. In particular, laser vibrometer and radar interferometer measurements are used to estimate natural frequencies and mode shapes. This information is crucial to obtain the tensile axial force in the tie-rods, which can be used as an indicator of structural integrity or possible failure. Furthermore, a novel approach is proposed where drones (Unmanned Aerial Vehicles) can be successfully used to improve the effectiveness and the accuracy of the experimental activities.

  13. A novel low-cost targeting system (LCTS) based upon a high-resolution 2D imaging laser radar

    NASA Astrophysics Data System (ADS)

    Grasso, Robert J.; Odhner, Jefferson E.; Wikman, John C.; Skaluba, Fred W.; Dippel, George F.; McDaniel, Robert V.; Ferrell, David S.; Seibel, William

    2005-10-01

    BAE SYSTEMS has developed a Low Cost Targeting System (LCTS) consisting of a FLIR for target detection, laser-illuminated, gated imaging for target identification, laser rangefinder and designator, GPS positioning, and auto-tracking capability within a small compact system size. This system has proven its ability to acquire targets, range and identify these targets, and designate or provide precise geo-location coordinates to these targets. The system is based upon BAE Systems proven micro-bolometer passive LWIR camera coupled with Intevac's new EBAPS camera. A dual wavelength diode pumped laser provides eyesafe ranging and target illumination, as well as designation; a custom detector module senses the return pulse for target ranging and to set the range gates for the gated camera. Intevac's camera is a CMOS based device with used selectable gate widths and can read at up to 28 frames/second when operated in VGA mode. The Transferred Electron photocathode enables high performance imaging in the SWIR band by enabling single photon detection at high quantum efficiency. Trials show that the current detectors offer complete extinction of signals outside of the gated range, thus, providing high resolution within the gated region. The images have shown high spatial resolution arising from the use of solid state focal plane array technology. Imagery has been collected in both the laboratory and the field to verify system performance during a variety of operating conditions.

  14. RADAR WARNING SYSTEM,

    DTIC Science & Technology

    RADAR TRACKING, *AIRCRAFT DEFENSE SYSTEMS, RADAR EQUIPMENT, AIR TO AIR, SEARCH RADAR, GUIDED MISSILES, HIGH SPEED BOMBING, EARLY WARNING SYSTEMS, FIRE CONTROL SYSTEM COMPONENTS, AIRCRAFT, TIME, CHINA.

  15. The depth measurement of internal defect based on laser speckle shearing interference

    NASA Astrophysics Data System (ADS)

    Peng, Yanhua; Liu, Guixiong; Quan, Yanming; Zeng, Qilin

    2017-07-01

    Speckle shearing interference has been widely used in non-destructive testing (NDT) as a useful NDT tool for its 阿advantages such as full-field, non-contacting measurement and so on. It reveals internal defect of an object by identifying defect-induced deformation anomalies. The location and size of internal defects are critical factors in determining the stability of the performance and the service life of the workpiece. This paper put forward a method of the depth measurement of internal defect based on laser speckle shearing interference. The measurement of defect depth is achieved by establishing the mechanical model which contains defect depth, out-of-plane displacement and load conditions, etc., and combining the relevant image information obtained from speckle pattern. The measurement error is less than 10%. The experiments demonstrate that it has a good consistency between the actual depth and the measurement result obtained by the method of this paper.

  16. Laser metal deposition with spatial variable orientation based on hollow-laser beam with internal powder feeding technology

    NASA Astrophysics Data System (ADS)

    Shi, Tuo; Lu, Bingheng; Shi, Shihong; Meng, Weidong; Fu, Geyan

    2017-02-01

    In this study, a hollow-laser beam with internal powder feeding (HLB-IPF) head is applied to achieve non-horizontal cladding and deposition of overhanging structure. With the features of this head such as uniform scan energy distribution, thin and straight spraying of the powder beam, the deposition in spatial variable orientation is conducted using a 6-axis robot. During the deposition process the head keeps tangential to the growth direction of the part. In the experiment, a "vase" shaped metal part with overhanging structure is successfully deposited, and the largest overhanging angle achieves 80° to the vertical direction. The "step effect" between cladding layers is completely eliminated with the best surface roughness of Ra=3.864 μm. Cross section of cladding layers with unequal height are deposited for angle change. Test results indicate that the formed part has uniform wall thickness, fine microstructure and high microhardness.

  17. Scanning of the internal structure part with laser ultrasonic in aviation industry.

    PubMed

    Swornowski, Pawel J

    2011-01-01

    The detection of internal defects is a major production and safety issue for the newest generations of aircraft. New materials and manufacturing processes in the aircraft industry demand efficient quality assurance in manufacturing and inspection in maintenance. Advanced metallic material processes (titanium) are used or developed for the production of heavily loaded flying components (in fan blade construction). The inspection of these parts mainly made out of titanium (or CFRP) requires the determination of the percentage of bonded grain sizes around 10-30 µm. This is primarily due to the advantages of a high signal-to-noise ratio and good detection sensitivity. In this article, a diagnosing method of the blade interior by means of the laser ultrasonic is presented. Identification of small fatigue cracks presents a challenging problem during nondestructive testing of fatigue-damaged structures. Laser ultrasonic is a technique that uses two laser beams; one with a short pulse for the generation of ultrasound and another with a long pulse or continuous coupled to an optical interferometer for detection. The results of research of the internal blade structure are presented.

  18. Marginal and internal fit of metal-ceramic crowns fabricated with a new laser melting technology.

    PubMed

    Quante, Katrin; Ludwig, Klaus; Kern, Matthias

    2008-10-01

    The purpose of this in vivo investigation was to evaluate the marginal and internal fit of metal-ceramic crowns fabricated with a new laser melting procedure (BEGO Medical, Bremen, Germany), and to investigate the influence of ceramic firing on the marginal and internal accuracy of these crowns. After tooth preparation, impression taking using polyvinylsiloxane and model casting, each preparation was contact less scanned by strip-light-projection. The finishing line and the virtual construction of the metal coping were defined by means of a computer. Using CAD/CAM software the metal copings were produced by BEGO Medical (Germany). A base metal alloy (Wirobond C) and a precious alloy (BioPontoStar, both: BEGO Medical) were used in this study with 14 restorations each. The internal and marginal accuracy of the specimens were examined using a silicone indicator paste (Fit Checker, GC, Japan). After setting, the silicone films were embedded in acrylic resin and sectioned four times. Each slice was photographed digitally at 60x magnification for marginal and at 15x magnification for occlusal adaptation, respectively. Using a light microscope the thickness of the silicone layer was measured at 10 reference points, a total of 3360 measurements. This procedure was repeated after the ceramic firing in the dental laboratory and after intraoral adjustment clinically. No statistically significant differences between the two alloys were found at any time. The mean marginal discrepancies ranged from 74 to 99 microm for both alloys. The internal gaps ranged from 250 to 350 microm. Ceramic firing increased the marginal discrepancies while the internal gaps decreased especially at occlusal surface. However, only in one case a slight statistically significance could be determined (p=0.046). The results of this in vivo study show that crowns produced with laser melting technology exhibit a marginal and internal accuracy that is comparable to conventional production procedures.

  19. A laser induced fluorescence technique for quantifying transient liquid fuel films utilising total internal reflection

    NASA Astrophysics Data System (ADS)

    Alonso, Mario; Kay, Peter J.; Bowen, Phil J.; Gilchrist, Robert; Sapsford, Steve

    2010-01-01

    This paper describes the development of a laser induced fluorescence (LIF) technique to quantify the thickness and spatial distribution of transient liquid fuel films formed as a result of spray-wall interaction. The LIF technique relies on the principle that upon excitation by laser radiation the intensity of the fluorescent signal from a tracer like 3-pentanone is proportional to the film thickness. A binary solution of 10% (v/v) of 3-pentanone in iso-octane is used as a test fuel with a Nd:YAG laser as the excitation light source (utilising the fourth harmonic at wavelength 266 nm) and an intensified CCD camera is used to record the results as fluorescent images. The propagation of the excitation laser beam through the optical piston is carefully controlled by total internal reflection so that only the fuel film is excited and not the airborne droplets above the film, which had been previously shown to induce significant error. Other known sources of error are also carefully minimised. Calibrated temporally resolved benchmark results of a transient spray from a gasoline direct injector impinging on a flat quartz crown under atmospheric conditions are presented, with observations and discussion of the transient development of the fuel film. The calibrated measurements are consistent with previous studies of this event and demonstrate the applicability of the technique particularly for appraisal of CFD predictions. The potential utilisation of the technique under typical elevated ambient conditions is commented upon.

  20. Ground penetrating radar evaluation of the internal structure of fluvial tufa deposits (Dévanos-Añavieja system, NE Spain): an approach to different scales of heterogeneity

    NASA Astrophysics Data System (ADS)

    Pueyo Anchuela, Ó.; Luzón, A.; Pérez, A.; Muñoz, A.; Mayayo, M. J.; Gil Garbi, H.

    2016-07-01

    The Quaternary Añavieja-Dévanos tufa system is located in the northern sector of the Iberian Chain. It has been previously tackled by means sedimentological studies focused on the available outcrops and some boreholes. They have permitted the proposal of a sedimentary scenario that fits with a pool-barrage fluvial tufa model. However a better knowledge of the characteristics and internal distribution of the usually non-outcropping pool deposits as well as of its relationship with barrage deposits has not been evaluated in detail yet. Palaeoenvironmental studies on tufas are usually biased because tufas are commonly delicate facies exposed to intense erosion during water level fall stages; for this reason outcrops are usually scarce and very often coincide with the most cemented barrage deposits. In order to analyse the internal characteristics of the tufa deposits under study, but also the lateral correlation among different facies, ground penetrating radar (GPR) has been employed both for the evaluation of its applicability in such kind of environments and to improve, if possible, the sedimentary model using geophysical data in sectors without outcrops. A GPR survey including different antennas ranging from 50 to 500 MHz along different sectors and its comparison with natural outcrops has been carried out. GPR results have permitted to deduce clear differences between pool and barrage deposits and to recognise its internal structure and geometrical relationships. The survey also permitted an approach to different scales of heterogeneities in the radarfacies evaluation by using distinct antennas and therefore, reaching different resolutions and penetrations. The resulting integration from different antennas allows three different attenuant and eight reflective radarfacies to be defined permitting a better approach to the real extension of the pool areas. These results have permitted to decipher the horizontal and vertical facies changes and the identification of

  1. Desorption Dynamics, Internal Energies and Imaging of Organic Molecules from Surfaces with Laser Desorption and Vacuum Ultraviolet (VUV) Photoionization

    SciTech Connect

    Kostko, Oleg; Takahashi, Lynelle K.; Ahmed, Musahid

    2011-04-05

    There is enormous interest in visualizing the chemical composition of organic material that comprises our world. A convenient method to obtain molecular information with high spatial resolution is imaging mass spectrometry. However, the internal energy deposited within molecules upon transfer to the gas phase from a surface can lead to increased fragmentation and to complications in analysis of mass spectra. Here it is shown that in laser desorption with postionization by tunable vacuum ultraviolet (VUV) radiation, the internal energy gained during laser desorption leads to minimal fragmentation of DNA bases. The internal temperature of laser-desorbed triacontane molecules approaches 670 K, whereas the internal temperature of thymine is 800 K. A synchrotron-based VUV postionization technique for determining translational temperatures reveals that biomolecules have translational temperatures in the range of 216-346 K. The observed low translational temperatures, as well as their decrease with increased desorption laser power is explained by collisional cooling. An example of imaging mass spectrometry on an organic polymer, using laser desorption VUV postionization shows 5 mu m feature details while using a 30 mu m laser spot size and 7 ns duration. Applications of laser desorption postionization to the analysis of cellulose, lignin and humic acids are briefly discussed.

  2. Desorption dynamics, internal energies, and imaging of organic molecules from surfaces with laser desorption and vacuum ultraviolet (VUV) photoionization.

    PubMed

    Kostko, Oleg; Takahashi, Lynelle K; Ahmed, Musahid

    2011-11-04

    There is enormous interest in visualizing the chemical composition of organic material that comprises our world. A convenient method to obtain molecular information with high spatial resolution is imaging mass spectrometry. However, the internal energy deposited within molecules upon transfer to the gas phase from a surface can lead to increased fragmentation and to complications in analysis of mass spectra. Here it is shown that in laser desorption with postionization by tunable vacuum ultraviolet (VUV) radiation, the internal energy gained during laser desorption leads to minimal fragmentation of DNA bases. The internal temperature of laser-desorbed triacontane molecules approaches 670 K, whereas the internal temperature of thymine is 800 K. A synchrotron-based VUV postionization technique for determining translational temperatures reveals that biomolecules have translational temperatures in the range of 216-346 K. The observed low translational temperatures as well as their decrease with increased desorption laser power is explained by collisional cooling. An example of imaging mass spectrometry on an organic polymer by using laser-desorption VUV postionization shows 5 μm feature details while using a 30 μm laser spot size and 7 ns pulse duration. Applications of laser-desorption postionization to the analysis of cellulose, lignin, and humic acids are briefly discussed. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Sub-microsecond wavelength stabilization of tunable lasers with the internal wavelength locker

    NASA Astrophysics Data System (ADS)

    Kimura, Ryoga; Tatsumoto, Yudai; Sakuma, Kazuki; Onji, Hirokazu; Shimokozono, Makoto; Ishii, Hiroyuki; Kato, Kazutoshi

    2016-08-01

    We proposed a method of accelerating the wavelength stabilization after wavelength switching of the tunable distributed amplification-distributed feedback (TDA-DFB) laser using the internal wavelength locker to reduce the size and the cost of the wavelength control system. The configuration of the wavelength stabilization system based on this locker was as follows. At the wavelength locker, the light intensity after an optical filter is detected as a current by the photodiodes (PDs). Then, for estimating the wavelength, the current is processed by the current/voltage-converting circuit (IVC), logarithm amplifier (Log Amp) and field programmable gate array (FPGA). Finally, the laser current is tuned to the desired wavelength with reference to the estimated wavelength. With this control system the wavelength is stabilized within 800 ns after wavelength switching, which is even faster than that with the conventional control system.

  4. Scanning-Pencil-Beam Radar Scatterometer

    NASA Technical Reports Server (NTRS)

    Long, David G.; Freilich, Michael H.; Leotta, Daniel F.; Noon, Don E.

    1992-01-01

    SCANSCAT conceptual scanning radar scatterometer placed in nearly polar orbit around Earth at altitude of 705 km aboard Spacecraft B of NASA's Earth Observing System. Measures radar backscattering from surface of ocean. Data processed on ground into normalized radar-backscattering cross sections, then processed into velocities of winds near surface of ocean by use of empirical mathematical model of relationship between normalized backscattering cross section, wind vector at scanned spot, and angle of incidence and azimuth angle of radar beam. Accuracy and coverage exceeds those of fan-beam scatterometer. Modified versions of scanning plan useful in laser inspection of surface finishes on machined parts.

  5. Scanning-Pencil-Beam Radar Scatterometer

    NASA Technical Reports Server (NTRS)

    Long, David G.; Freilich, Michael H.; Leotta, Daniel F.; Noon, Don E.

    1992-01-01

    SCANSCAT conceptual scanning radar scatterometer placed in nearly polar orbit around Earth at altitude of 705 km aboard Spacecraft B of NASA's Earth Observing System. Measures radar backscattering from surface of ocean. Data processed on ground into normalized radar-backscattering cross sections, then processed into velocities of winds near surface of ocean by use of empirical mathematical model of relationship between normalized backscattering cross section, wind vector at scanned spot, and angle of incidence and azimuth angle of radar beam. Accuracy and coverage exceeds those of fan-beam scatterometer. Modified versions of scanning plan useful in laser inspection of surface finishes on machined parts.

  6. GEOS-3 C-Band radar investigations

    NASA Technical Reports Server (NTRS)

    Dempsey, D. J.

    1978-01-01

    The absolute accuracy of instrumentation radar systems, refined methods of calibrating these systems, and the techniques employed in processing the associated data. A world-wide network of C-Band instrumentation radars augmented by lasers and other tracking instrumentation systems were used. The NASA WFC AN/FPQ-6 instrumentation radar and the AN/FPS-16 instrumentation radar also located at NASA WFC were the primary instruments used in the accuracy and calibration evaluations. The results achieved at WFC were then disseminated to other Ranges where they were verified, augmented and used as part of routine operations.

  7. Radar volcano monitoring system in Iceland

    NASA Astrophysics Data System (ADS)

    Arason, Þórður; Yeo, Richard F.; Sigurðsson, Geirfinnur S.; Pálmason, Bolli; von Löwis, Sibylle; Nína Petersen, Guðrún; Bjornsson, Halldór

    2013-04-01

    Weather radars are valuable instruments in monitoring explosive volcanic eruptions. Temporal variations in the eruption strength can be monitored as well as variations in plume and ash dispersal. Strength of the reflected radar signal of a volcanic plume is related to water content and droplet sizes as well as type, shape, amount and the grain size distribution of ash. The Icelandic Meteorological Office (IMO) owns and operates three radars and one more is planned for this radar volcano monitoring system. A fixed position 250 kW C-band weather radar was installed in 1991 in SW-Iceland close to Keflavík International Airport, and upgraded to a doppler radar in 2010. In cooperation with the International Civil Aviation Organization (ICAO), IMO has recently invested in two mobile X-band radars and one fixed position C-band radar. The fixed position 250 kW doppler C-band weather radar was installed in April 2012 at Fljótsdalsheiði, E-Iceland, and in June 2012 IMO received a mobile 65 kW dual-polarization doppler X-band radar. Early in 2013 IMO will acquire another mobile radar of the same type. Explosive volcanic eruptions in Iceland during the past 22 years were monitored by the Keflavík radar: Hekla 1991, Gjálp 1996, Grímsvötn 1998, Hekla 2000, Grímsvötn 2004, Eyjafjallajökull 2010 and Grímsvötn 2011. Additionally, the Grímsvötn 2011 eruption was mointored by a mobile X-band radar on loan from the Italian Civil Protection Authorities. Detailed technical information is presented on the four radars with examples of the information acquired during previous eruptions. This expanded network of radars is expected to give valuable information on future volcanic eruptions in Iceland.

  8. Principles of the formation of laser radar image being observed through a sea surface and water thickness

    NASA Astrophysics Data System (ADS)

    Luchinin, Alexandr G.

    1994-09-01

    A great number of articles, special reference books and monographs are dedicated to the problem of underwater objects visibility. However many important problems remain unsolved. It concerns the underwater objects visibility through rough surface mainly. The present article is dedicated to the main aspects of this problem, exactly to the underwater objects observation with the aid of certain devices using artificial (laser) illumination. The notion of the image signal/noise ratio is introduced which takes into account both shot noises and signal fluctuations caused by a random air/water interface. Various methods of image formation for optic observation systems are considered. It is shown that the best results are obtained with the aid of the system, which has the maximum space and time averaging of fluctuations during the signal formation. Most important is the conclusion that the equivalence of two most popular methods of image formation (known in the theory visibility in turbid media) is violated, when observation is performed through a rough sea surface. In the considered case the best parameters has a system, which uses a pulsed laser beam of illumination with a wide aperture and a multi-unit receiver with time gating. The examples of calculation of the main characteristics of such systems are given.

  9. Principles of the formation of laser radar image being observed through a sea surface and water thickness

    NASA Astrophysics Data System (ADS)

    Luchinin, Alexandr G.

    1994-11-01

    A great number of articles, special reference books and monographs are dedicated to the problem of underwater objects visibility. However many important problems remain unsolved. It concerns the underwater objects visibility through rough surface mainly. The present article is dedicated to the main aspects of this problem, exactly to the underwater objects observation with the aid of certain devices using artificial (laser) illumination. The notion of the image signal/noise ratio is introduced which takes into account both shot noises and signal fluctuations caused by a random air/water interface. Various methods of image formation for optic observation systems are considered. It is shown that the best results are obtained with the aid of the system, which has the maximum space and time averaging of fluctuations during the signal formation. Most important is the conclusion that the equivalence of two most popular methods of image formation (known in the theory visibility in turbid media) is violated, when observation is performed through a rough sea surface. In the considered case the best parameters has a system, which uses a pulsed laser beam of illumination with a wide aperture and a multi-unit receiver with time gating. The examples of calculation of the main characteristics of such systems are given.

  10. Neutron Imaging for Selective Laser Melting Inconel Hardware with Internal Passages

    NASA Technical Reports Server (NTRS)

    Tramel, Terri L.; Norwood, Joseph K.; Bilheux, Hassina

    2014-01-01

    Additive Manufacturing is showing great promise for the development of new innovative designs and large potential life cycle cost reduction for the Aerospace Industry. However, more development work is required to move this technology into space flight hardware production. With selective laser melting (SLM), hardware that once consisted of multiple, carefully machined and inspected pieces, joined together can be made in one part. However standard inspection techniques cannot be used to verify that the internal passages are within dimensional tolerances or surface finish requirements. NASA/MSFC traveled to Oak Ridge National Lab's (ORNL) Spallation Neutron Source to perform some non-destructive, proof of concept imaging measurements to assess the capabilities to understand internal dimensional tolerances and internal passages surface roughness. This presentation will describe 1) the goals of this proof of concept testing, 2) the lessons learned when designing and building these Inconel 718 test specimens to minimize beam time, 3) the neutron imaging test setup and test procedure to get the images, 4) the initial results in images, volume and a video, 4) the assessment of using this imaging technique to gather real data for designing internal flow passages in SLM manufacturing aerospace hardware, and lastly 5) how proper cleaning of the internal passages is critically important. In summary, the initial results are very promising and continued development of a technique to assist in SLM development for aerospace components is desired by both NASA and ORNL. A plan forward that benefits both ORNL and NASA will also be presented, based on the promising initial results. The initial images and volume reconstruction showed that clean, clear images of the internal passages geometry are obtainable. These clear images of the internal passages of simple geometries will be compared to the build model to determine any differences. One surprising result was that a new cleaning

  11. Reliability of scanning laser acoustic microscopy for detecting internal voids in structural ceramics

    NASA Technical Reports Server (NTRS)

    Roth, D. J.; Baaklini, G. Y.

    1986-01-01

    The reliability of 100 MHz scanning laser acoustic microscopy (SLAM) for detecting internal voids in sintered specimens of silicon nitride and silicon carbide was evaluated. The specimens contained artificially implanted voids and were positioned at depths ranging up to 2 mm below the specimen surface. Detection probability of 0.90 at a 0.95 confidence level was determined as a function of material, void diameter, and void depth. The statistical results presented for void detectability indicate some of the strengths and limitations of SLAM as a nondestructive evaluation technique for structural ceramics.

  12. Compressive Sensing for Radar and Radar Sensor Networks

    DTIC Science & Technology

    2013-12-02

    27] Hong-Sam Le, Qilian Liang, “Joint Multi-target Identification and Classification in Cognitive Radar Sensor Networks,” International Journal of Wireless Information Networks , vol...Networks," International Journal of Wireless Information Networks , vol. 18, no. 2, pp. 100-107, 2011. 8. Sukhvinder Singh, Qilian Liang, Dechang

  13. Validation of International Society of Urological Pathology (ISUP) grading for prostatic adenocarcinoma in thin core biopsies using TROG 03.04 'RADAR' trial clinical data.

    PubMed

    Delahunt, B; Egevad, L; Srigley, J R; Steigler, A; Murray, J D; Atkinson, C; Matthews, J; Duchesne, G; Spry, N A; Christie, D; Joseph, D; Attia, J; Denham, J W

    2015-10-01

    In 2014 a consensus conference convened by the International Society of Urological Pathology (ISUP) adopted amendments to the criteria for Gleason grading and scoring (GS) for prostatic adenocarcinoma. The meeting defined a modified grading system based on 5 grading categories (grade 1, GS 3+3; grade 2, GS 3+4; grade 3, GS 4+3; grade 4, GS 8; grade 5, GS 9-10). In this study we have evaluated the prognostic significance of ISUP grading in 496 patients enrolled in the TROG 03.04 RADAR Trial. There were 19 grade 1, 118 grade 2, 193 grade 3, 88 grade 4 and 79 grade 5 tumours in the series, with follow-up for a minimum of 6.5 years. On follow-up 76 patients experienced distant progression of disease, 171 prostate specific antigen (PSA) progression and 39 prostate cancer deaths. In contrast to the 2005 modified Gleason system (MGS), the hazards of the distant and PSA progression endpoints, relative to grade 2, were significantly greater for grades 3, 4 and 5 of the 2014 ISUP grading scheme. Comparison of predictive ability utilising Harrell's concordance index, showed 2014 ISUP grading to significantly out-perform 2005 MGS grading for each of the three clinical endpoints.

  14. Variability in Arctic sea ice topography and atmospheric form drag: Combining IceBridge laser altimetry with ASCAT radar backscatter.

    NASA Astrophysics Data System (ADS)

    Petty, A.; Tsamados, M.; Kurtz, N. T.

    2016-12-01

    Here we present atmospheric form drag estimates over Arctic sea ice using high resolution, three-dimensional surface elevation data from NASA's Operation IceBridge Airborne Topographic Mapper (ATM), and surface roughness estimates from the Advanced Scatterometer (ASCAT). Surface features of the ice pack (e.g. pressure ridges) are detected using IceBridge ATM elevation data and a novel surface feature-picking algorithm. We use simple form drag parameterizations to convert the observed height and spacing of surface features into an effective atmospheric form drag coefficient. The results demonstrate strong regional variability in the atmospheric form drag coefficient, linked to variability in both the height and spacing of surface features. This includes form drag estimates around 2-3 times higher over the multiyear ice north of Greenland, compared to the first-year ice of the Beaufort/Chukchi seas. We compare results from both scanning and linear profiling to ensure our results are consistent with previous studies investigating form drag over Arctic sea ice. A strong correlation between ASCAT surface roughness estimates (using radar backscatter) and the IceBridge form drag results enable us to extrapolate the IceBridge data collected over the western-Arctic across the entire Arctic Ocean. While our focus is on spring, due to the timing of the primary IceBridge campaigns since 2009, we also take advantage of the autumn data collected by IceBridge in 2015 to investigate seasonality in Arctic ice topography and the resulting form drag coefficient. Our results offer the first large-scale assessment of atmospheric form drag over Arctic sea ice due to variable ice topography (i.e. within the Arctic pack ice). The analysis is being extended to the Antarctic IceBridge sea ice data, and the results are being used to calibrate a sophisticated form drag parameterization scheme included in the sea ice model CICE, to improve the representation of form drag over Arctic and

  15. International linking of research and development on the model of Laser Centre Hanover

    NASA Astrophysics Data System (ADS)

    Nowitzki, Klaus-Dieter; Boedecker, Olaf

    2005-10-01

    Asia is becoming one of the most important regions in the world from the political, economic and scientific point of view. Germany believes that it is becoming increasingly necessary to cooperate with certain Asian countries especially for scientific and technological reasons. Above and beyond exchanges of scientists, the scientific and technological cooperation will be organized to cover projects with specific targets and to find solutions to important problems. International economic development is characterized by a mixture of competition and cooperation within the context of growing globalization. Germany, being one of the world's largest exporting nation, must therefore combine its active role in cooperation with these countries in the fields of education, research and innovation with economic cooperation. The Laser Centre Hanover pursues the goal of establishing and operating a Chinese German center for training and further education in laser technology and setting up a joint platform for long-term German Chinese cooperation in laser technology. An optimized training infrastructure combined with modern production processes support consequently long-term German businesses in China and secures their market-shares. LZH establishes Laser academies for skilled workers and technical decision makers in Shanghai and Changchun together with local universities and German partners. Due to the economic growth, Russia records since more than two years, the economic conditions are improving the cooperation between Germany and Russia step-by-step. The main goal of Russian science-politics is to stabilize an efficient scientific-technical potential with better chances in the global competition. The German-Russian scientific and technological cooperation plays an important role in this context. It has considerably increased in the last years in terms of width and depth and virtually includes all areas of science and technology at present. The region around Moscow is regarded

  16. The Triglav Glacier (South-Eastern Alps, Slovenia): Volume Estimation, Internal Characterization and 2000-2013 Temporal Evolution by Means of Ground Penetrating Radar Measurements

    NASA Astrophysics Data System (ADS)

    Del Gobbo, Costanza; Colucci, Renato R.; Forte, Emanuele; Triglav Čekada, Michaela; Zorn, Matija

    2016-08-01

    It is well known that small glaciers of mid latitudes and especially those located at low altitude respond suddenly to climate changes both on local and global scale. For this reason their monitoring as well as evaluation of their extension and volume is essential. We present a ground penetrating radar (GPR) dataset acquired on September 23 and 24, 2013 on the Triglav glacier to identify layers with different characteristics (snow, firn, ice, debris) within the glacier and to define the extension and volume of the actual ice. Computing integrated and interpolated 3D using the whole GPR dataset, we estimate that at the moment of data acquisition the ice area was 3800 m2 and the ice volume 7400 m3. Its average thickness was 1.95 m while its maximum thickness was slightly more than 5 m. Here we compare the results with a previous GPR survey acquired in 2000. A critical review of the historical data to find the general trend and to forecast a possible evolution is also presented. Between 2000 and 2013, we observed relevant changes in the internal distribution of the different units (snow, firn, ice) and the ice volume reduced from about 35,000 m3 to about 7400 m3. Such result can be achieved only using multiple GPR surveys, which allow not only to assess the volume occupied by a glacial body, but also to image its internal structure and the actual ice volume. In fact, by applying one of the widely used empirical volume-area relations to infer the geometrical parameters of the glacier, a relevant underestimation of ice-loss would be achieved.

  17. Effect of internal optical loss on the modulation bandwidth of a quantum dot laser

    NASA Astrophysics Data System (ADS)

    Wu, Yuchang; Suris, Robert A.; Asryan, Levon V.

    2012-03-01

    We show that the internal optical loss, which increases with free-carrier density in the waveguide region, considerably reduces the modulation bandwidth ω-3 dB of a quantum dot laser. At a certain optimum value j0opt of the dc component of the injection current density, the maximum bandwidth ω-3dBmax is attained and the modulation response function becomes as flat as possible. With internal loss cross-section σint increasing and approaching its maximum tolerable value, ω-3dBmax decreases and becomes zero. As with j0opt, there also exists the optimum cavity length, at which ω-3 dB is highest; the larger is σint, the longer is the optimum cavity.

  18. Shuttle imaging radar experiment

    USGS Publications Warehouse

    Elachi, C.; Brown, W.E.; Cimino, J.B.; Dixon, T.; Evans, D.L.; Ford, J.P.; Saunders, R.S.; Breed, C.; Masursky, H.; McCauley, J.F.; Schaber, G.; Dellwig, L.; England, A.; MacDonald, H.; Martin-Kaye, P.; Sabins, F.

    1982-01-01

    The shuttle imaging radar (SIR-A) acquired images of a variety of the earth's geologic areas covering about 10 million square kilometers. Structural and geomorphic features such as faults, folds, outcrops, and dunes are clearly visible in both tropical and arid regions. The combination of SIR-A and Seasat images provides additional information about the surface physical properties: topography and roughness. Ocean features were also observed, including large internal waves in the Andaman Sea. Copyright ?? 1982 AAAS.

  19. Laser assisted internal mammary artery-coronary artery anastomosis - an experimental study

    NASA Astrophysics Data System (ADS)

    Zhu, Hong-Sheng; Zhang, Liang-ping; Feng, Lian

    2005-07-01

    Objective: To observe the time required for anastomosis and the reliability for pressure tolerance after internal mammay artery (IMA) -coronary artery anastomosis. Method: Eight sheep underwent thoracotomy and left IMA harvest. In group I (T) the IMA were anastomosed to left anterior descending artery (LAD) with 7-0 prolene suture (n=4) and in group II (LA) IMA were anastomosed to LAD with laser. Result: The time required for laser technique was shorter than that required in suturing technique [117.5+/-39.48min (total) and 38.25+/-6.23 min vs 62.5+/-37.83 min (total) and 20+/-6.53 min respectively ] (p<0.01). Prior to closing thoracotomy both two groups endured the impact of pharmacologic vasopressor. No leakage at the anastomosed site was observed in both groups. After the closure of thoracotomy, well tolerance for both adrenalin and thoracic negative pressure was observed in the two groups. The peak systolic pressure induced by pharmacologic agent was similar in both groups. Neither stenosis nor thrombus or embolism was observed and immediate patency rate in both groups was 100%. Conclusion: Laser assisted technique seems to be favorable for patency rate and could lead to better result after coronary artery bypass grafting(CABG).

  20. PAWS locker: a passively aligned internal wavelength locker for telecommunications lasers

    NASA Astrophysics Data System (ADS)

    Boye, Robert R.; Te Kolste, Robert; Kathman, Alan D.; Cruz-Cabrera, Alvaro; Knight, Douglas; Hammond, J. Barney

    2003-11-01

    This paper presents the passively aligned Wavesetter (PAWS) locker: a micro-optic subassembly for use as an internal wavelength locker. As the wavelength spacing in dense wavelength division multiplexing (WDM) decreases, the performance demands placed upon source lasers increase. The required wavelength stability has led to the use of external wavelength lockers utilizing air-spaced, thermally stabilized etalons. However, package constraints are forcing the integration of the wavelength locker directly into the laser module. These etalons require active tuning be done during installation of the wavelength locker as well as active temperature control (air-spaced etalons are typically too large for laser packages). A unique locking technique will be introduced that does not require an active alignment or active temperature compensation. Using the principles of phase shifting interferometry, a locking signal is derived without the inherent inflection points present in the signal of an etalon. The theoretical background of PAWS locker will be discussed as well as practical considerations for its implementation. Empirical results will be presented including wavelength accuracy, alignment sensitivity and thermal performance.

  1. Synchronization of internal and external degrees of freedom of atoms in a standing laser wave

    SciTech Connect

    Argonov, V.Yu.; Prants, S.V.

    2005-05-15

    We consider dissipative dynamics of atoms in a strong standing laser wave and find a nonlinear dynamical effect of synchronization between center-of-mass motion and internal Rabi oscillations. The synchronization manifests itself in the phase space as limit cycles, which may have different periods and riddled basins of attraction. The effect can be detected in fluorescence spectra of atoms as equidistant sideband frequencies with the space between adjacent peaks to be inversely proportional to the value of the period of the respective limit cycle. With increasing intensity of the laser field, we numerically observe cascades of bifurcations that eventually end up in settling a strange chaotic attractor. A broadband noise is shown to destroy a fine structure of the bifurcation scenario, but prominent features of period-1 and period-3 limit cycles survive under a weak noise. The character of the atomic motion is analyzed with the help of the friction force whose zeroes are attractor or repellor points in the velocity space. We find ranges of the laser parameters where the atomic motion resembles a random but deterministic walking of atoms erratically jumping between different wells of the optical potential. Such a random walking is shown to be fractal.

  2. Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings

    PubMed Central

    Kim, Myung-Joo; Choi, Yun-Jung; Kim, Seong-Kyun; Heo, Seong-Joo; Koak, Jai-Young

    2017-01-01

    Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe’s test, and Pearson’s correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05). The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit. PMID:28772451

  3. Marginal Accuracy and Internal Fit of 3-D Printing Laser-Sintered Co-Cr Alloy Copings.

    PubMed

    Kim, Myung-Joo; Choi, Yun-Jung; Kim, Seong-Kyun; Heo, Seong-Joo; Koak, Jai-Young

    2017-01-23

    Laser sintered technology has been introduced for clinical use and can be utilized more widely, accompanied by the digitalization of dentistry and the development of direct oral scanning devices. This study was performed with the aim of comparing the marginal accuracy and internal fit of Co-Cr alloy copings fabricated by casting, CAD/CAM (Computer-aided design/Computer-assisted manufacture) milled, and 3-D laser sintered techniques. A total of 36 Co-Cr alloy crown-copings were fabricated from an implant abutment. The marginal and internal fit were evaluated by measuring the weight of the silicone material, the vertical marginal discrepancy using a microscope, and the internal gap in the sectioned specimens. The data were statistically analyzed by One-way ANOVA (analysis of variance), a Scheffe's test, and Pearson's correlation at the significance level of p = 0.05, using statistics software. The silicone weight was significantly low in the casting group. The 3-D laser sintered group showed the highest vertical discrepancy, and marginal-, occlusal-, and average- internal gaps (p < 0.05). The CAD/CAM milled group revealed a significantly high axial internal gap. There are moderate correlations between the vertical marginal discrepancy and the internal gap variables (r = 0.654), except for the silicone weight. In this study, the 3-D laser sintered group achieved clinically acceptable marginal accuracy and internal fit.

  4. Internal magnetic field measurements by laser-based POlarimeter-INTerferometer (POINT) system on EAST

    NASA Astrophysics Data System (ADS)

    Liu, H. Q.; Jie, Y. X.; Ding, W. X.; Brower, D. L.; Zou, Z. Y.; Qian, J. P.; Li, W. M.; Yang, Y.; Zeng, L.; Zhang, S. B.; Lan, T.; Wang, S. X.; Hanada, K.; Wei, X. C.; Hu, L. Q.; Wan, B. N.

    2016-01-01

    A multi-channel far-infrared laser-based POlarimeter-INTerferometer (POINT) system utilizing the three-wave technique has been implemented for fully diagnosing the internal magnetic field in the EAST tokamak. Double-pass, horizontal, radially-viewing chords access the plasma via an equatorial port. The laser source consists of three CW formic acid (HCOOH) FIR lasers at nominal wavelength 432.5 μm which are optically pumped by independent infrared CO2 lasers. Output power is more than 30 mW of per cavity. Novel molybdenum retro-reflectors, can with withstand baking temperature up to 350°C and discharge duration more than 1000 s, are mounted in the inside wall for the double-pass optical arrangement. A Digital Phase Detector with 250 kHz bandwidth, which provide real-time Faraday rotation angle and density phase shift output for plasma control, have been developed for the POINT system. Reliability of both polarimetric and interferometric measurement are obtained in 22 s long pulse H mode discharge and 8 s NBI H mode discharge, indicating the POINT system works for any heating scheme on EAST so far. The electron line-integrated density resolution of POINT is less than 1 × 1016 m-2 (< 1°), and the Faraday rotation angle rms phase noise is < 0.1°. With the high temporal (~ 1 μsec) and phase resolution (< 0.1°), perturbations associated with the sawtooth cycle and MHD activity have been observed. The current profile, density profile and safety factor (q) profile are reconstructed by using EFIT code from the external magnetic and the validation POINT data. Realtime EFIT with Faraday angle and density phase shift constraints will be implemented in the plasma control system in the future.

  5. Open Skies Treaty imaging radar technology issues

    NASA Astrophysics Data System (ADS)

    Sandoval, M. B.

    1992-06-01

    This paper discusses the imaging radar technology requirements for the Open Skies regime, including the unresolved issues to be discussed at future Open Skies Consultative Commission (OSCC) meetings. Compliance with international rules on shared technology is addressed and some of the practical considerations for operational deployment of the radar imaging equipment in an Open Skies aircraft are presented. The Open Skies Treaty requirements and validation methodologies for imaging radars that were agreed on and those that will require future OSCC review are discussed.

  6. Spaceborne radar research in the 1980's

    NASA Technical Reports Server (NTRS)

    Elachi, C.

    1983-01-01

    The SEASAT SAR and Shuttle Imaging Radar SIR-A experiments demonstrated that spaceborne synthetic aperture radars provide synoptic images of land and ocean features. Radar images clearly show geologic structures, morphologic features, clear cutting, subsurface features (in very arid regions), agricultural and urban land use, ocean surface waves, current boundaries, internal waves, ice floes and numerous other ocean features which affect the surface roughness.

  7. Intra-Pulse Radar-Embedded Communications

    DTIC Science & Technology

    2011-08-26

    Blunt, E. Mokole, R. Schneible, and M. Wicks, SciTech Publishing, 2010. 3. S.D. Blunt, T. Higgins, A.K. Shackelford , and K. Gerlach, “Multistatic... Shackelford , “Multi-dimensional Adaptive Processing for Angle-Dependent Radar Waveforms,” in preparation for IET Radar, Sonar & Navigation. 8. H... Shackelford , “Time-Range Adaptive Processing for Pulse Agile Radar,” 5 th International Waveform Diversity & Design Conference, Niagara Falls, Canada

  8. Frequency stabilization of ambience-isolated internal-mirror He-Ne lasers by thermoelectric-cooling thermal compensation

    NASA Astrophysics Data System (ADS)

    Shirvani-Mahdavi, Hamidreza; Narges, Yaghoubi

    2016-12-01

    An approach for frequency stabilization of an ambience-isolated internal-mirror He-Ne laser (632.8 nm) utilizing temperature control of the laser tube with Peltier thermoelectric coolers is demonstrated. Measurements indicate that there are an optimal temperature (23 °C) and an optimal discharge current (5.5 mA) of laser tube for which the laser light power is separately maximized. To prevent the effect of fluctuation of discharge current on the laser stability, an adjustable current source is designed and fabricated so that the current is set to be optimal (5.50 ± 0.01 mA). To isolate the laser tube from the environment, the laser metallic box connected to two Peltier thermoelectric coolers is surrounded by two thermal and acoustic insulator shells. The laser has two longitudinal modes very often. Any change in the frequency of longitudinal modes at the optimal temperature is monitored by sampling the difference of longitudinal modes' intensities. Therefore, using a feedback mechanism, the current of thermoelectric coolers is so controlled that the frequency of modes stays constant on the gain profile of the laser. The frequency stability is measured equal to 1.17 × 10-9 (˜2700×) for less than 1 min and 2.57 × 10-9 (˜1200×) for more than 1 h.

  9. Planetary radar

    NASA Technical Reports Server (NTRS)

    Taylor, R. M.

    1980-01-01

    The radar astronomy activities supported by the Deep Space Network during June, July, and August 1980 are reported. The planetary bodies observed were Venus, Mercury, and the asteroid Toro. Data were obtained at both S and X band, and the observations were considered successful.

  10. Multispecies in situ monitoring of a static internal combustion engine by near-infrared diode laser sensors.

    PubMed

    Gérard, Yvan; Holdsworth, Robert J; Martin, Philip A

    2007-07-01

    A multispecies near-infrared diode laser spectrometer has been constructed for measurements of carbon monoxide, carbon dioxide, and methane directly in the exhaust of a static internal combustion engine. A wavelength modulation-division multiplexing scheme was implemented for the two distributed feedback diode lasers. Gas concentration variations were observed for changes in operating conditions such as increasing and decreasing the throttle, adjusting the air-fuel ratio, and engine start-up.

  11. Rebalancing of internally generated carriers for mid-infrared interband cascade lasers with very low power consumption.

    PubMed

    Vurgaftman, I; Bewley, W W; Canedy, C L; Kim, C S; Kim, M; Merritt, C D; Abell, J; Lindle, J R; Meyer, J R

    2011-12-13

    The interband cascade laser differs from any other class of semiconductor laser, conventional or cascaded, in that most of the carriers producing population inversion are generated internally, at semimetallic interfaces within each stage of the active region. Here we present simulations demonstrating that all previous interband cascade laser performance has suffered from a significant imbalance of electron and hole densities in the active wells. We further confirm experimentally that correcting this imbalance with relatively heavy n-type doping in the electron injectors substantially reduces the threshold current and power densities relative to all earlier devices. At room temperature, the redesigned devices require nearly two orders of magnitude less input power to operate in continuous-wave mode than the quantum cascade laser. The interband cascade laser is consequently the most attractive option for gas sensing and other spectroscopic applications requiring low output power and minimum heat dissipation at wavelengths extending from 3 μm to beyond 6 μm.

  12. International, private-public, multi-mission, next-generation lunar laser retroreflectors

    NASA Astrophysics Data System (ADS)

    Dell'Agnello, Simone

    2017-04-01

    Since the 1970s Lunar Laser Ranging (LLR) to the Apollo/Lunokhod Cube Corner Retroreflector (CCR) arrays supplied some of the best tests of General Relativity (GR): possible changes in the gravitational constant, weak and strong equivalence principle, gravitational self-energy (PPN parameter beta), geodetic precession, inverse-square force-law [1][2]. LLR has also provided significant information on the composition of the deep interior of the Moon [3]. LLR physics analysis also allows for constraints on extensions of GR (like spacetime torsion [4]) and on new gravitational physics that may explain the gravitational universe without Dark Matter and Dark Energy (like Non-Minimally Coupled gravity [5]). LLR is the only Apollo/Lunokhod experiment still in operation. In the 1970s LLR arrays contributed a negligible fraction of the ranging error budget. Since the capabilities of ground stations of the International Laser Ranging Service (in particular APOLLO in USA) improved by more than two orders of magnitude, now, because of the lunar librations, current CCR arrays dominate the error. With the US/Italy project LLRRA21/MoonLIGHT (Lunar Laser Ranging Retroreflector Array for the 21st century/Moon Laser Instrumentation for General relativity High accuracy Tests) UMD (Univ. of Maryland) and INFN (Italian National Institute for Nuclear Physics) developed a new-generation LLR payload made by a single, large CCR (100 mm diameter), unaffected by the effect of librations, that will improve the LLR accuracy by a factor of ten to one hundred. The performance of this 'big CCR' is being characterized at the SCF_Lab test facility at INFN-LNF, Frascati, Italy [6]. INFN also developed INRRI (INstrument for landing-Roving laser Retroreflector Investigations), a microreflector payload for the lunar surface to be laser-ranged by orbiters [7]. This will further extend the physics and lunar science reach of LLR. INRRI can also provide positioning services on the far side (it is proposed

  13. X-ray lasers. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Mauk, S. C.

    1980-01-01

    Various aspects of X-ray lasers are discussed in approximately 122 citations. Included are laser plasmas and outputs, plasma radiation, far ultraviolet radiation, gamma rays, optical pumping, optical resonators, and electron transitions. Laser applications, laser materials, and laser fusion are also included.

  14. Neodymium YAG lasers. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Mauk, S. C.

    1980-01-01

    Various aspects of neodymium yag lasers are discussed in approximately 267 citations. Laser materials and outputs, laser mode locking; crystal, fiber, and nonlinear optics, optical pumping communications, energy conversion efficiency, and laser applications are covered. Pulsed, continuous wave, solid state, Q switched, infrared, and dye lasers are included.

  15. Reconstructing the internal structure and long-term evolution of hazardous sinkholes combining trenching, electrical resistivity imaging (ERI) and ground penetrating radar (GPR)

    NASA Astrophysics Data System (ADS)

    Fabregat, Ivan; Gutiérrez, Francisco; Roqué, Carles; Comas, Xavier; Zarroca, Mario; Carbonel, Domingo; Guerrero, Jesús; Linares, Rogelio

    2017-05-01

    The approaches aimed at characterising specific damaging sinkholes have received limited attention compared with other ground instability phenomena (e.g. landslides). Moreover, the practicality of the trenching technique in combination with numerical dating and retro-deformation analysis for sinkhole site-investigations has been barely explored. This work illustrates the advantages of combining geomorphic mapping, electrical resistivity imaging (ERI), ground penetrating radar (GPR) and trenching for sinkhole characterisation and shows how the trenching technique contributes to fill significant gaps that neither geomorphic nor geophysical methods can address. Two large sinkholes (> 200 m long) related to the interstratal karstification of evaporites and generated by contrasting subsidence mechanisms (sagging, collapse) were investigated in the Fluvia Valley, NE Spain. Although GPR data may provide high resolution information on subsidence-related stratigraphic and structural features at shallow depth, the profiles acquired in the investigated sites with 100 MHz shielded and 40 MHz unshielded antennae provided limited insight into the internal geometry of the sinkholes due to reduced signal penetration related to the presence of conductive clayey material. The ERI sections satisfactorily imaged the general geometry of the sagging and collapse subsidence structures up to depths higher than 100 m and clearly captured the basal contact of the low-resistivity sinkhole fill in the sections with adequate layout and resolution. The trenches, despite their limited depth (ca. 5 m) allowed us to obtain valuable objective information on several key aspects of the subsidence phenomenon: (1) mechanisms (deformation style) and kinematics (progressive versus episodic); (2) limits of ground deformation; (3) temporal evolution (expansion versus contraction); (4) chronology and timing of most recent deformation phase; (5) rates of subsidence and sedimentation; and (6) the role played

  16. Mars meter-scale roughness: Goldstone Solar System Radar delay-doppler database

    NASA Technical Reports Server (NTRS)

    Haldemann, A. F. C.; Jurgens, R. F.; Slade, M. A.

    2002-01-01

    The entire fourteen-year database of Goldstone Solar System Radar Mars near-nadir radar scattering model fits is being revised using the latest topography from the Mars Global Surveyor Mars Orbiter Laser Altimeter instrument.

  17. Thermometer ions for matrix-enhanced laser desorption/ionization internal energy calibration.

    PubMed

    Greisch, J-F; Gabelica, V; Remacle, F; De Pauw, E

    2003-01-01

    This work describes a method to use relative fragmentation yields to characterize the internal energy distribution of ions produced by matrix-enhanced laser desorption/ionization mass spectrometry (MELDI-MS, see: Wright LG, Cooks RG, Wood KL. Biomed. Mass Spectrom. 1985; 12: 153-162). Assuming that the fragmentation proceeds statistically and that the collisions in the source lead to a Boltzmann-like distribution of the internal energy, a characteristic parameter, the effective temperature, is introduced to describe the internal energy distribution of the ions observed. The hypotheses, advantages and drawbacks of the implementation of the method that uses substituted benzylpyridinium salts as thermometer ions are discussed. Use is made of two matrices that produce no matrix cations in MELDI and are suitable for small cationic salts. The actual value of this effective temperature significantly depends on an accurate determination of the threshold dissociation energies and on the time spent in the source, in addition to the statistical hypothesis itself. The method could be applied to normalize spectra in order to compare results issued from different instruments.

  18. The Second Spaceborne Imaging Radar Symposium

    NASA Technical Reports Server (NTRS)

    1986-01-01

    Summaries of the papers presented at the Second Spaceborne Imaging Radar Symposium are presented. The purpose of the symposium was to present an overwiew of recent developments in the different scientific and technological fields related to spaceborne imaging radars and to present future international plans.

  19. Watchdog for ARM Radar Network Operations

    SciTech Connect

    2016-07-28

    WARNO is a software system designed to monitor the radars in the ARM Radar Network. It allows real time monitoring and tracking of instrument state and condition. It provides a web portal on the front end to interact with users, a REST API webpoint for interactions with third party systems, and an internal distributed architecture to allow it to be deployed at multiple sites.

  20. [Spectrophotometric and visual analysis of internal dental bleaching utilizing laser and heat as catalyzing sources].

    PubMed

    de Carvalho, Elaine Manso Oliveira Franco; Robazza, Carlos Roberto Colombo; Lage-Marques, José Luiz

    2002-01-01

    This experiment aimed at evaluating, in vitro, the chromatic alteration of dental crowns submitted to internal bleaching. Color alterations were evaluated by means of spectrophotometric analysis and visual observation, at the following experimental phases: initial reading (LI), after-darkening reading (LE), immediate after-bleaching reading (LC), bleaching checked after 15 days (LC15) and after 30 days (LC30). After finding the values of L* (luminosity), a* and b* (shade and saturation), which made it possible to quantify the chromatic alterations of the specimens, color differences (deltaE ) were assessed by means of the CIE Lab Program. The statistical analysis of the results did not reveal any significant difference between conventional bleaching and bleaching activated by Er:YAG laser. No statistical difference was observed between the results after 15 and 30 days, for both experimental groups.

  1. Radars in space

    NASA Technical Reports Server (NTRS)

    Delnore, Victor E.

    1990-01-01

    The capabilities of active microwave devices operating from space (typically, radar, scatterometers, interferometers, and altimeters) are discussed. General radar parameters and basic radar principles are explained. Applications of these parameters and principles are also explained. Trends in space radar technology, and where space radars and active microwave sensors in orbit are going are discussed.

  2. Optical design and laser ablation of surface textures: demonstrating total internal reflection

    NASA Astrophysics Data System (ADS)

    Gommans, Hans; Booij, Silvia; Pijlman, Fetze; Krijn, Marcel; de Zwart, Siebe; Sepkhanov, Ruslan; Beaumont, Dave; van der Schaft, Hans; Sanders, Rene

    2015-09-01

    In lighting applications key drivers for optical design of surface textures are integration of optical elements, the disentanglement of optical functionality and appearance and late stage configuration. We investigated excimer laser ablation as a mastering technology for micro textured surfaces, where we targeted an increase in correspondence between surface design and ablated surface for high aspect ratio structures. To achieve this we have improved the photo mask design using a heuristic algorithm that corrects for the angular dependence of the ablation process and the loss of image resolution at ablation depths that exceed the depth of field. Using this approach we have been able to demonstrate close correspondence between designed and ablated facet structures up to 75° inclination at 75 μm depth. These facet design parameters allow for total internal reflection (TIR) as a means of beam deflection which is demonstrated in a range of mono shaped cone arrays in hexagonal tessellation. BSDF analysis was used to characterize the narrow TIR deflection beams that matched the peak positions of the design down to 28° apex. In addition, a single surface TIR-Fresnel lens design with focal distance 5 mm has been manufactured using this photo mask design algorithm and beam collimation up to 12° beam angle and 32° field angle is shown. These outcomes demonstrate that the laser ablation process intrinsically yields sufficient small dispersion in structure and fillet radii for lighting applications.

  3. TRMM radar

    NASA Technical Reports Server (NTRS)

    Okamoto, Kenichi

    1993-01-01

    The results of a conceptual design study and the performance of key components of the Bread Board Model (BBM) of the Tropical Rainfall Measuring Mission (TRMM) radar are presented. The radar, which operates at 13.8 GHz and is designed to meet TRMM mission objectives, has a minimum measurable rain rate of 0.5 mm/h with a range resolution of 250 m, a horizontal resolution of about 4 km, and a swath width of 220 km. A 128-element active phased array system is adopted to achieve contiguous scanning within the swath. The basic characteristics of BBM were confirmed by experiments. The development of EM started with the cooperation of NASDA and CRL.

  4. Novel laser communications transceiver with internal gimbal-less pointing and tracking

    NASA Astrophysics Data System (ADS)

    Chalfant, Charles H., III; Orlando, Fred J., Jr.; Gregory, Jeff T.; Sulham, Clifford; O'Neal, Chad B.; Taylor, Geoffrey W.; Craig, Douglas M.; Foshee, James J.; Lovett, J. Timothy

    2002-12-01

    This paper describes a novel laser communications transceiver for use in multi-platform satellite networks or clusters that provides internal pointing and tracking technique allowing static mounting of the transceiver subsystems and minimal use of mechanical stabilization techniques. This eliminates the need for the large, power hungry, mechanical gimbals that are required for laser cross-link pointing, acquisition and tracking. The miniature transceiver is designed for pointing accuracies required for satellite cross-link distances of between 500 meters to 5000 meters. Specifically, the designs are targeting Air Force Research Lab's TechSat21 Program, although alternative transceiver configurations can provide for much greater link distances and other satellite systems. The receiver and transmitter are connected via fiber optic cabling from a separate electronics subsystem containing the optoelectronics PCBs, thereby eliminating active optoelectronic elements from the transceiver's mechanical housing. The internal acquisition and tracking capability is provided by an advanced micro-electro-mechanical system (MEMS) and an optical design that provides a specific field-of-view based on the satellite cluster's interface specifications. The acquisition & tracking control electronics will utilize conventional closed loop tracking techniques. The link optical power budget and optoelectronics designs allow use of transmitter sources with output powers of near 100 mW. The transceiver will provide data rates of up to 2.5 Gbps and operate at either 1310 nm or 1550 nm. In addition to space-based satellite to satellite cross-links, we are planning to develop a broad range of applications including air to air communications between highly mobile airborne platforms and terrestrial fixed point to point communications.

  5. Quantitative Analysis of Carbon Steel with Multi-Line Internal Standard Calibration Method Using Laser-Induced Breakdown Spectroscopy.

    PubMed

    Pan, Congyuan; Du, Xuewei; An, Ning; Zeng, Qiang; Wang, Shengbo; Wang, Qiuping

    2016-04-01

    A multi-line internal standard calibration method is proposed for the quantitative analysis of carbon steel using laser-induced breakdown spectroscopy (LIBS). A procedure based on the method was adopted to select the best calibration curves and the corresponding emission lines pairs automatically. Laser-induced breakdown spectroscopy experiments with carbon steel samples were performed, and C, Cr, and Mn were analyzed via the proposed method. Calibration curves of these elements were constructed via a traditional single line internal standard calibration method and a multi-line internal standard calibration method. The calibration curves obtained were evaluated with the determination coefficient, the root mean square error of cross-validation, and the average relative error of cross-validation. All of the parameters were improved significantly with the proposed method. The results show that accurate and stable calibration curves can be obtained efficiently via the multi-line internal standard calibration method. © The Author(s) 2016.

  6. Radar Sounder

    DTIC Science & Technology

    1988-09-01

    over the shorter time period (resulting in a multilook SAR ) with the result that spatial resolution, the usual r~ason for using SAR techniques, degrades...Field - - - ALT 21. Sea Surface Topography - - - SAR , ALT 22. Ocean Waves (sea, swell, surf) V. Good Some V. Good SAR , ALT * with additional lower freq...OLS - Operational Line-scan System radiometer (4-6 GHz?) ALT - Altimeter •* good at low microwave SAR - Synthetic Aperture frequencies Radar + over

  7. PREFACE: Fourteenth International Symposium on Laser-Aided Plasma Diagnostics (LAPD14)

    NASA Astrophysics Data System (ADS)

    Giudicotti, L.; Pasqualotto, R.

    2010-04-01

    The attached PDF contains, the full preface, a list of the scientific committee, former LAPD chairmen, local organizers, previous locations of LAPD meetings, participants email contacts and a list of the contributed papers. logo The Fourteenth International Symposium on Laser-Aided Plasma Diagnostics (LAPD14), was held from 21-24 September 2009 in Castelbrando, Treviso, Italy. The series of LAPD symposia was originally started at Kyushu University in 1983, and since then it has been organized every two years alternately in Japan, Europe and the United States, traveling around the world five times. Each LAPD Symposium brings together scientists working in different disciplines all related to the diagnostics of any type of plasma by laser or similar techniques. Researchers working on nuclear fusion, industrial process, low temperature plasma chemistry, laser development and material science, are invited to present prominent new diagnostic developments, with the aim of synergetic discussions. The broad spectrum of contributions represents one of the strengths of this symposium, which is an important, unique and fruitful source of cross-fertilization between these fields and a forum of discussions. The scope of LAPD14 was very broad, including many techniques related to laser probing of plasmas: incoherent and coherent Thomson scattering, polarimetry, interferometry, reflectometry, laser induced fluorescence, laser absorption spectroscopy, laser photodetachment spectroscopy, cavity ringdown spectroscopy, Raman scattering, reflectometry, microwave diagnostics and related laser and hardware developments. LAPD14 was attended by 66 researchers, from 15 different countries who presented a total of 57 papers (13 general, 12 topical, 10 short talks and 23 poster contributions). It is a tradition of LAPD that the first lecture of each meeting, which is more general and aims to review prominent new developments, is called 'the Akazaki lecture' in honor of Professor Masanori

  8. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Calculation of the temperature distribution in ridged-waveguide laser diodes

    NASA Astrophysics Data System (ADS)

    Piprek, J.; Nürnberg, R.

    1988-11-01

    A numerical solution is obtained of the steady-state heat conduction equation for InGaAsP/InP ridge-waveguide lasers (λ = 1.3 μm) soldered upside down to a heat sink. Two-dimensional temperature distributions perpendicular to the ridge are obtained. It is assumed that the heat sources inside such a laser are the active region and the contact at the top of the ridge. An increase in the temperature of the junction and the corresponding thermal resistance of a laser chip and solder are calculated for several sets of laser parameters. The results indicate that the thermal properties are particularly sensitive to the width of the ridge and the thickness of the solder. The results obtained should be useful in thermal optimization of ridge-waveguide laser diodes.

  9. Analysis of experimental NRL radar altimeter data

    NASA Technical Reports Server (NTRS)

    Walsh, E. J.

    1974-01-01

    An X-band radar capable of continuously variable transmitted pulse durations down to 1 nsec is being flown to investigate the interaction of radar altimeter signals with the sea surface. There is good agreement between the observed radar altimeter leading edge rise time for a 1-nsec transmitted pulse and the rise time predicted from the radar parameters and the sea state determined by a laser profilometer. Using a threshold tracker on 29-pulse averages for a transmitted pulse of 24 nsec, it was found that the range noise varied linearly with the power level of the threshold over a considerable range. The altimeter range quantization was 9.35 cm, and a minimum range noise of 3.9 cm was obtained. A comparison of pulse-to-pulse correlation observed in the radar data with that predicted by a Monte Carlo simulation is used to obtain a measure of sea surface scatterer motion.

  10. Internal stress-induced melting below melting temperature at high-rate laser heating

    SciTech Connect

    Hwang, Yong Seok; Levitas, Valery I.

    2014-06-30

    In this Letter, continuum thermodynamic and phase field approaches (PFAs) predicted internal stress-induced reduction in melting temperature for laser-irradiated heating of a nanolayer. Internal stresses appear due to thermal strain under constrained conditions and completely relax during melting, producing an additional thermodynamic driving force for melting. Thermodynamic melting temperature for Al reduces from 933.67 K for a stress-free condition down to 898.1 K for uniaxial strain and to 920.8 K for plane strain. Our PFA simulations demonstrated barrierless surface-induced melt nucleation below these temperatures and propagation of two solid-melt interfaces toward each other at the temperatures very close to the corresponding predicted thermodynamic equilibrium temperatures for the heating rate Q≤1.51×10{sup 10}K/s. At higher heating rates, kinetic superheating competes with a reduction in melting temperature and melting under uniaxial strain occurs at 902.1 K for Q = 1.51 × 10{sup 11 }K/s and 936.9 K for Q = 1.46 × 10{sup 12 }K/s.

  11. INTERNATIONAL CONFERENCE ON SEMICONDUCTOR INJECTION LASERS SELCO-87: Behavior of gain-guided lasers generating high-power nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Erbert, G.

    1988-11-01

    Computer-controlled apparatus was used in an investigation of gain-guided narrow-stripe AlGaAs double heterostructure lasers. These lasers were excited with current pulses of 10 ns duration and amplitudes up to 3 A. The watt-ampere characteristics together with near- and far-field radiation patterns were considered using an analytic model of the lasers. The results showed that the values of the gain under a stripe contact or of the absorption outside this region varied with the output power.

  12. Planetary landing-zone reconnaissance using ice-penetrating radar data: Concept validation in Antarctica

    NASA Astrophysics Data System (ADS)

    Grima, Cyril; Schroeder, Dustin M.; Blankenship, Donald D.; Young, Duncan A.

    2014-11-01

    The potential for a nadir-looking radar sounder to retrieve significant surface roughness/permittivity information valuable for planetary landing site selection is demonstrated using data from an airborne survey of the Thwaites Glacier Catchment, West Antarctica using the High Capability Airborne Radar Sounder (HiCARS). The statistical method introduced by Grima et al. (2012. Icarus 220, 84-99. http://dx.doi.org/10.1007/s11214-012-9916-y) for surface characterization is applied systematically along the survey flights. The coherent and incoherent components of the surface signal, along with an internally generated confidence factor, are extracted and mapped in order to show how a radar sounder can be used as both a reflectometer and a scatterometer to identify regions of low surface roughness compatible with a planetary lander. These signal components are used with a backscattering model to produce a landing risk assessment map by considering the following surface properties: Root mean square (RMS) heights, RMS slopes, roughness homogeneity/stationarity over the landing ellipse, and soil porosity. Comparing these radar-derived surface properties with simultaneously acquired nadir-looking imagery and laser-altimetry validates this method. The ability to assess all of these parameters with an ice penetrating radar expands the demonstrated capability of a principle instrument in icy planet satellite science to include statistical reconnaissance of the surface roughness to identify suitable sites for a follow-on lander mission.

  13. Femtosecond laser written 16.5 mm long glass-waveguide amplifier and laser with 5.2 dB cm-1 internal gain at 1534 nm

    NASA Astrophysics Data System (ADS)

    Hoyo, J.; Berdejo, V.; Toney Fernandez, T.; Ferrer, A.; Ruiz, A.; Valles, J. A.; Rebolledo, M. A.; Ortega-Feliu, I.; Solis, J.

    2013-10-01

    A 16.5 mm long, heavily doped erbium-ytterbium phosphate glass-waveguide amplifier was fabricated by the femtosecond laser (fs-laser) inscription technique. The femtosecond laser inscription of waveguides was carried out at 500 kHz repetition rate using a 0.68 NA aspheric lens. The energy deposition profile in the dielectric material was initially simulated using a generalized adaptive fast-Fourier evolver (GAFFE) algorithm. The size and shape of the guiding structures were carefully controlled by the slit shaping technique to reduce the coupling losses, with achievable values down to less than 0.1 dB. Rigorous simulations of the response of the active waveguides were carried out to optimize their performance as optical amplifiers. A maximum of 8.6 dB internal gain at 1534 nm was obtained upon bidirectional laser pumping at 976 nm, leading to a gain per unit length of 5.2 dB cm-1. Laser action was also achieved for both ring and linear cavity configurations.

  14. Internal structure of the nanogratings generated inside bulk fused silica by ultrafast laser direct writing

    SciTech Connect

    Sharma, S. P.; Vilar, R.; Oliveira, V.; Herrero, P.

    2014-08-07

    The aim of the present work was to characterize the internal structure of nanogratings generated inside bulk fused silica by ultrafast laser processing and to study the influence of diluted hydrofluoric acid etching on their structure. The nanogratings were inscribed at a depth of 100 μm within fused silica wafers by a direct writing method, using 1030 nm radiation wavelength and the following processing parameters: E = 5 μJ, τ = 560 fs, f = 10 kHz, and v = 100 μm/s. The results achieved show that the laser-affected regions are elongated ellipsoids with a typical major diameter of about 30 μm and a minor diameter of about 6 μm. The nanogratings within these regions are composed of alternating nanoplanes of damaged and undamaged material, with an average periodicity of 351 ± 21 nm. The damaged nanoplanes contain nanopores randomly dispersed in a material containing a large density of defects. These nanopores present a roughly bimodal size distribution with average dimensions for each class of pores 65 ± 20 × 16 ± 8 × 69 ± 16 nm{sup 3} and 367 ± 239 × 16 ± 8 × 360 ± 194 nm{sup 3}, respectively. The number and size of the nanopores increases drastically when an hydrofluoric acid treatment is performed, leading to the coalescence of these voids into large planar discontinuities parallel to the nanoplanes. The preferential etching of the damaged material by the hydrofluoric acid solution, which is responsible for the pores growth and coalescence, confirms its high defect density.

  15. Improved Measurement Performance of Inorganic Elements in Coal by Laser-Induced Breakdown Spectroscopy Coupled with Internal Standardization

    NASA Astrophysics Data System (ADS)

    Yao, Shunchun; Xu, Jialong; Bai, Kaijie; Lu, Jidong

    2015-11-01

    Laser-induced breakdown spectroscopy was employed to determine the inorganic elements in coal. To improve the measurement's accuracy and precision, a new internal standardization scheme, which we named changed internal standardization, was compared with the traditional internal standardization and no internal standardization for the analysis of inorganic elements. The new internal standardization scheme used the atomic line of carbon at 247.86 nm and the molecular band of CN at 388.34 nm and C2 at 516.32 nm to normalize the lines of inorganic elements that were distributed in the same spectral channel. The performance of the utilization of the new internal standardization scheme was evaluated using a set of coal samples, including twenty calibration samples and five validation samples. The results show that the coefficients of determination R2 and the slope of calibration models coupled with changed internal standardization are better than that of the calibration models coupled with fixed internal standardization and no internal standardization. Moreover, the measurement accuracy and reproducibility of changed internal standardization for the analysis of five validation samples also yielded further improvement. The results that we obtained suggest that changed internal standardization could compensate for the matrix effects, as well as the influence of the difference in the spectral response of the light collection system. supported by Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology of China (No. SKL2013KF03), National Natural Science Foundation of China (Nos. 51206055, 51476061), the Fundamental Research Funds for the Central Universities of China (No. 2014ZZ0014), the New Star of Pearl River on Science and Technology of Guangzhou, China (No. 2014J2200054), the Key Laboratory of Efficient and Clean Energy Utilization of Guangdong Higher Education Institutes of China (No. KLB10004) and Guangdong Province Key Laboratory of Efficient and

  16. PREFACE: 3rd International Symposium on Laser Ultrasonics and Advanced Sensing

    NASA Astrophysics Data System (ADS)

    2014-06-01

    Based on the use of laser as a coherent and intense light source, the photo-acoustics originated from the discovery made by Alexander Graham Bell was extended to laser-ultrasonics (LU), and it has been applied to wide area of ultrasonics, optics, material characterization and nondestructive inspection. In 1996, a research group for LU was started in the Japanese Society for Nondestructive Inspection (JSNDI), and researches on LU and related topics such as noncontact measurements and elastic wave theories were discussed. Similar activities were pursued also in North America and in Europe. The international symposium on LU was started in Montreal, Canada in 2008 by Jean Pierre Monchalin in order to offer a forum for involved with basic researches and industrial applications of LU. In the second symposium in Bordeaux, France nearly 120 papers were presented. It is our honor to have organized the third symposium, LU2013 on 25-28 June in Yokohama, Japan. The articles published here provide a sample of achievements presented there. In LU2013, we focused on the laser generation and/or detection of acoustic waves, application to nondestructive testing, ultrafast-optoacoustics and innovative instruments. Research achievements in biomedical applications, advanced sensing including noncontact, micro/nanoscale or nonlinear measurements, as well as theory and simulation of ultrasound were also included, considering the interdisciplinary nature of this field. We enjoyed very excellent and informative 3 plenary talks, 11 invited talks, 81 oral and 41 poster presentations with 168 attendees. According to requests, we organized a post deadline poster session to give an opportunity to present recent achievements after the deadline. Contributions of the participants, the scientific and organizing committees are highly appreciated. The conference tour was a dinner cruise to the Tokyo bay, and we hope this experience will remain as a pleasant memory in attendees. As decided in the

  17. Kharkiv Meteor Radar System (the XX Age)

    NASA Astrophysics Data System (ADS)

    Kolomiyets, S. V.

    2012-09-01

    Kharkiv meteor radar research are of historic value (Kolomiyets and Sidorov 2007). Kharkiv radar observations of meteors proved internationally as the best in the world, it was noted at the IAU General Assembly in 1958. In the 1970s Kharkiv meteor automated radar system (MARS) was recommended at the international level as a successful prototype for wide distribution. Until now, this radar system is one of the most sensitive instruments of meteor radars in the world for astronomical observations. In 2004 Kharkiv meteor radar system is included in the list of objects which compose the national property of Ukraine. Kharkiv meteor radar system has acquired the status of the important historical astronomical instrument in world history. Meteor Centre for researching meteors in Kharkiv is a analogue of the observatory and performs the same functions of a generator and a battery of special knowledge and skills (the world-famous studio). Kharkiv and the location of the instrument were brand points on the globe, as the place where the world-class meteor radar studies were carried out. They are inscribed in the history of meteor astronomy, in large letters and should be immortalized on a world-wide level.

  18. Radar applications of gigawatt sources at millimeter wave frequencies

    SciTech Connect

    Bruder, J.A.; Belcher, M.L. . Research Inst.)

    1991-06-01

    The high transmit powers provided by free electron laser (FEL) sources in combination with the narrow antenna beamwidths achievable at millimeter wave (MMW) frequencies offer potential for use in a number of radar applications. Potential applications of high power millimeter wave sources include satellite imaging, low angle radar tracking, radar astronomy, and a number of other possible applications such as atmospheric research, space debris detection, and space vehicle tracking. 3 refs., 3 figs.

  19. Evaluation of holmium laser versus cold knife in optical internal urethrotomy for the management of short segment urethral stricture

    PubMed Central

    Jain, Sudhir Kumar; Kaza, Ram Chandra Murthy; Singh, Bipin Kumar

    2014-01-01

    Objectives: Sachse cold knife is conventionally used for optical internal urethrotomy intended to manage urethral strictures and Ho: YAG laser is an alternative to it. The aim of this study was to evaluate the role of urethral stricture treatment outcomes, efficacy, and complications using cold knife and Ho: YAG (Holmium laser) for optical internal urethrotomy Materials and Methods: In this prospective study included, 90 male patients age >18 years, with diagnosis of urethral stricture admitted for internal optical urethrotomy during April 2010 to March 2012. The patients were randomized into two groups containing 45 patients each using computer generated random number. In group A (Holmium group), internal urethrotomy was done with Holmium laser and in group B (Cold knife group) Sachse cold knife was used. Patients were followed up for 6 months after surgery in Out Patient Department on 15, 30 and 180 post-operative days. At each follow up visit physical examination, and uroflowmetry was performed along with noting complaints, if any. Results: The peak flow rates (PFR) were compared between the two groups on each follow up. At 180 days (6 month interval) the difference between mean of PFR for Holmium and Cold knife group was statistically highly significant (P < 0.001). Complications were seen in 12.22% of cases. Conclusion: Both modalities are effective in providing immediate relief to patients with single and short segment (<2 cm long) urethral strictures but more sustained response was attained with Cold knife urethrotomy. PMID:25371611

  20. Radar Absorbing Material Design

    DTIC Science & Technology

    2003-09-01

    simulations of coated plates were performed to estimate the effectiveness of the absorbing layers in reducing radar cross section . The reduction in monostatic... radar cross section value is shown by plotting the radar cross section of the plate with and without radar absorbing material. ε t 15. NUMBER OF

  1. A total internal reflection-fluorescence correlation spectroscopy setup with pulsed diode laser excitation

    NASA Astrophysics Data System (ADS)

    Weger, Lukas; Hoffmann-Jacobsen, Kerstin

    2017-09-01

    Fluorescence correlation spectroscopy (FCS) measures fluctuations in a (sub-)femtoliter volume to analyze the diffusive behavior of fluorescent particles. This highly sensitive method has proven to be useful for the analysis of dynamic biological systems as well as in chemistry, physics, and material sciences. It is routinely performed with commercial fluorescence microscopes, which provide a confined observation volume by the confocal technique. The evanescent wave of total internal reflectance (TIR) is used in home-built systems to permit a surface sensitive FCS analysis. We present a combined confocal and TIR-FCS setup which uses economic low-power pulsed diode lasers for excitation. Excitation and detection are coupled to time-correlated photon counting hardware. This allows simultaneous fluorescence lifetime and FCS measurements in a surface-sensitive mode. Moreover, the setup supports fluorescence lifetime correlation spectroscopy at surfaces. The excitation can be easily switched between TIR and epi-illumination to compare the surface properties with those in liquid bulk. The capabilities of the presented setup are demonstrated by measuring the diffusion coefficients of a free dye molecule, a labeled polyethylene glycol, and a fluorescent nanoparticle in confocal as well as in TIR-FCS.

  2. Dynamic Oil Consumption Measurement of Internal Combustion Engines using Laser Spectroscopy.

    PubMed

    Sellmeier, Stefan; Alonso, Eduardo; Boesl, Ulrich

    2014-01-07

    A new approach has been developed to measure dynamic consumption of lubricant oil in an internal combustion engine. It is based on the already known technique where sulfur is used as a natural tracer of the engine oil. Since ejection of motor oil in gaseous form into the exhaust is by far the main source of engine oil consumption, detection of sulfur in the exhaust emission is a valuable way to measure engine oil consumption in a dynamic way. In earlier approaches, this is done by converting all sulfur containing chemical components into SO2 by thermal pyrolysis in a high temperature furnace at atmospheric pressure. The so-formed SO2 then is detected by broadband-UV-induced fluorescence or mass spectrometric methods. The challenge is to reach the necessary detection limit of 50 ppb. The new approach presented here includes sulfur conversion in a low-pressure discharge cell and laser-induced fluorescence with wavelength and fluorescence lifetime selection. A limit of detection down to 10 ppb at a temporal resolution in the time scale of few seconds is reached. Extensive, promising studies have been performed at a real engine test bench. Future developments of a compact, mobile device based on these improvements are discussed.

  3. Achieving operational two-way laser acquisition for OPALS payload on the International Space Station

    NASA Astrophysics Data System (ADS)

    Abrahamson, Matthew J.; Oaida, Bogdan V.; Sindiy, Oleg; Biswas, Abhijit

    2015-03-01

    The Optical PAyload for Lasercomm Science (OPALS) experiment was installed on the International Space Station (ISS) in April 2014. Developed as a technology demonstration, its objective was to experiment with space-to-ground optical communications transmissions from Low Earth Orbit. More than a dozen successful optical links were established between a Wrightwood, California-based ground telescope and the OPALS flight terminal from June 2014 to September 2014. Each transmission required precise bi-directional pointing to be maintained between the space-based transmitter and ground-based receiver. This was accomplished by acquiring and tracking a laser beacon signal transmitted from the ground telescope to the OPALS flight terminal on the ISS. OPALS demonstrated the ability to nominally acquire the beacon within three seconds at 25° elevation and maintain lock within 140 μrad (3σ) for the full 150-second transmission duration while slewing at rates up to 1°/sec. Additional acquisition attempts in low elevation and weather-challenged conditions provided valuable insight on the optical link robustness under off-nominal operational conditions.

  4. Radar and Lidar Radar DEM

    NASA Technical Reports Server (NTRS)

    Liskovich, Diana; Simard, Marc

    2011-01-01

    Using radar and lidar data, the aim is to improve 3D rendering of terrain, including digital elevation models (DEM) and estimates of vegetation height and biomass in a variety of forest types and terrains. The 3D mapping of vegetation structure and the analysis are useful to determine the role of forest in climate change (carbon cycle), in providing habitat and as a provider of socio-economic services. This in turn will lead to potential for development of more effective land-use management. The first part of the project was to characterize the Shuttle Radar Topography Mission DEM error with respect to ICESat/GLAS point estimates of elevation. We investigated potential trends with latitude, canopy height, signal to noise ratio (SNR), number of LiDAR waveform peaks, and maximum peak width. Scatter plots were produced for each variable and were fitted with 1st and 2nd degree polynomials. Higher order trends were visually inspected through filtering with a mean and median filter. We also assessed trends in the DEM error variance. Finally, a map showing how DEM error was geographically distributed globally was created.

  5. Space Radar Image of Long Island Optical/Radar

    NASA Technical Reports Server (NTRS)

    1994-01-01

    visible in the radar image; many of them can also be seen as bright lines i the optical image. The runways of John F. Kennedy International Airport appear as a dark rectangle in Jamaica Bay on the left side of the image. Developed areas appear generally as bright green and orange, while agricultural, protected and undeveloped areas appear darker blue or purple. This contrast can be seen on the barrier islands along the south coast of Long Island, which are heavily developed in the Rockaway and Long Beach areas south and east of Jamaica Bay, but further to the east, the islands are protected and undeveloped.

  6. Capabilities and limitations of existing MST radars: Colorado wind profilers

    NASA Technical Reports Server (NTRS)

    Strauch, R. G.

    1983-01-01

    The Wave Propagation Laboratory is developing a ground-based remote sensing system called PROFILER to measure troposphere parameters currently measured in operational meteorology by radiosondes. The prototype PROFILER uses two radars for wind sounding: a 6-m radar located at Platteville, Colorado, and a 33-cm radar located at Denver's Stapleton International Airport. In addition, a network of three 6-m wind-profiling radars is being installed in Colorado, and a fourth site is planned. The location of the five radars, their characteristics, and their limitations are described.

  7. Capabilities and limitations of existing MST radars: Colorado wind profilers

    NASA Astrophysics Data System (ADS)

    Strauch, R. G.

    1983-12-01

    The Wave Propagation Laboratory is developing a ground-based remote sensing system called PROFILER to measure troposphere parameters currently measured in operational meteorology by radiosondes. The prototype PROFILER uses two radars for wind sounding: a 6-m radar located at Platteville, Colorado, and a 33-cm radar located at Denver's Stapleton International Airport. In addition, a network of three 6-m wind-profiling radars is being installed in Colorado, and a fourth site is planned. The location of the five radars, their characteristics, and their limitations are described.

  8. Single mode wavelength control of modulated AlGaAs lasers with external and internal etalon feedback

    NASA Technical Reports Server (NTRS)

    Maynard, William L.

    1989-01-01

    Single mode lasing without mode hops has been obtained for VSIS and CSP laser diodes with an external etalon attached to the laser's front facet for up to an 8 C range CW and a 4 C range pulsed, with .07 nm/C tuning. Tests of thin tapered-thickness (TTT) laser diodes show CW and pulsed single mode lasing over 10 C and 2 C ranges, respectively, with .08 nm/C tuning. An analysis of the TTT structure reveals the equivalent of an internal etalon. The time-resolved pulsed behavior for both types of lasers show single mode lasing within the proper temperature ranges with minor modes present only early in the optical pulse, if at all. The external etalon produces noticeable interference fringes in the farfield pattern, while those of the TTT lasers are smooth. Ongoing CW lifetest results indicate stability to within one longitudinal mode after a few hundred hours of operation, along with at least several thousand hours lifetime.

  9. Analysis of internal crack propagation in silicon due to permeable pulse laser irradiation: study on processing mechanism of stealth dicing

    NASA Astrophysics Data System (ADS)

    Ohmura, Etsuji; Kawahito, Yuta; Fukumitsu, Kenshi; Okuma, Junji; Morita, Hideki

    2010-07-01

    Stealth dicing (SD) is an innovative dicing method developed by Hamamatsu Photonics K.K. In the SD method, a permeable nanosecond laser is focused inside a silicon wafer and scanned horizontally. A thermal shock wave propagates every pulse toward the side to which the laser is irradiated, then a high dislocation density layer is formed inside the wafer after the thermal shock wave propagation. In our previous study, it was concluded that an internal crack whose initiation is a dislocation is propagated when the thermal shock wave by the next pulse overlaps with this layer partially. In the experimental result, the trace that a crack is progressed gradually step by step was observed. In this study, the possibility of internal crack propagation by laser pulses was investigated. A two-dimensional thermal stress analysis based on the linear fracture mechanics was conducted using the stress distribution obtained by the axisymmetric thermal stress analysis. As a result, the validity of the hypothesis based on a heat transfer analysis result previously presented was supported. Also it was concluded that the internal crack is propagated by at least two pulses.

  10. Analysis of internal crack propagation in silicon due to permeable pulse laser irradiation: study on processing mechanism of stealth dicing

    NASA Astrophysics Data System (ADS)

    Ohmura, Etsuji; Kawahito, Yuta; Fukumitsu, Kenshi; Okuma, Junji; Morita, Hideki

    2011-02-01

    Stealth dicing (SD) is an innovative dicing method developed by Hamamatsu Photonics K.K. In the SD method, a permeable nanosecond laser is focused inside a silicon wafer and scanned horizontally. A thermal shock wave propagates every pulse toward the side to which the laser is irradiated, then a high dislocation density layer is formed inside the wafer after the thermal shock wave propagation. In our previous study, it was concluded that an internal crack whose initiation is a dislocation is propagated when the thermal shock wave by the next pulse overlaps with this layer partially. In the experimental result, the trace that a crack is progressed gradually step by step was observed. In this study, the possibility of internal crack propagation by laser pulses was investigated. A two-dimensional thermal stress analysis based on the linear fracture mechanics was conducted using the stress distribution obtained by the axisymmetric thermal stress analysis. As a result, the validity of the hypothesis based on a heat transfer analysis result previously presented was supported. Also it was concluded that the internal crack is propagated by at least two pulses.

  11. Two-photon-induced internal modification of silicon by erbium-doped fiber laser.

    PubMed

    Verburg, P C; Römer, G R B E; Huis In 't Veld, A J

    2014-09-08

    Three-dimensional bulk modification of dielectric materials by multiphoton absorption of laser pulses is a well-established technology. The use of multiphoton absorption to machine bulk silicon has been investigated by a number of authors using femtosecond laser sources. However, no modifications confined in bulk silicon, induced by multiphoton absorption, have been reported so far. Based on results from numerical simulations, we employed an erbium-doped fiber laser operating at a relatively long pulse duration of 3.5 nanoseconds and a wavelength of 1549 nm for this process. We found that these laser parameters are suitable to produce modifications at various depths inside crystalline silicon.

  12. Application of laser induced breakdown spectroscopy (LIBS) instrumentation for international safeguards

    SciTech Connect

    Barefield Ii, James E; Clegg, Samuel M; Lopez, Leon N; Le, Loan A; Veirs, D Kirk; Browne, Mike

    2010-01-01

    Advanced methodologies and improvements to current measurements techniques are needed to strengthen the effectiveness and efficiency of international safeguards. This need was recognized and discussed at a Technical Meeting on 'The Application of Laser Spectrometry Techniques in IAEA Safeguards' held at IAEA headquarters (September 2006). One of the principal recommendations from that meeting was the need to pursue the development of novel complementary access instrumentation based on Laser Induced Breakdown Spectroscopy (UBS) for the detection of gaseous and solid signatures and indicators of nuclear fuel cycle processes and associated materials'. Pursuant to this recommendation the Department of Safeguards (SG) under the Division of Technical Support (SGTS) convened the 'Experts and Users Advisory Meeting on Laser Induced Breakdown Spectroscopy (LIBS) for Safeguards Applications' also held at IAEA headquarters (July 2008). This meeting was attended by 12 LlBS experts from the Czech Republic, the European Commission, France, the Republic of South Korea, the United States of America, Germany, the United Kingdom of Great Britain, Canada, and Northern Ireland. Following a presentation of the needs of the IAEA inspectors, the LIBS experts agreed that needs as presented could be partially or fully fulfilled using LIBS instrumentation. Inspectors needs were grouped into the following broad categories: (1) Improvements to in-field measurements/environmental sampling; (2) Monitoring status of activities in Hot Cells; (3) Verify status of activity at a declared facility via process monitoring; and (4) Need for pre-screening of environmental samples before analysis. The primary tool employed by the IAEA to detect undeclared processes and activities at special nuclear material facilities and sites is environmental sampling. One of the objectives of the Next Generation Safeguards Initiative (NGSI) Program Plan calls for the development of advanced tools and methodologies to

  13. LPHYS'13: 22nd International Laser Physics Workshop (Prague, 15-19 July 2013)

    NASA Astrophysics Data System (ADS)

    Yevseyev, Alexander V.

    2013-04-01

    The 22nd annual International Laser Physics Workshop (LPHYS'13) will be held from 15-19 July 2013 in the city of Prague, Czech Republic, at the Hotel Krystal and Czech Technical University hosted this year by the Institute of Physics ASCR and Czech Technical University in Prague. LPHYS'13 continues a series of workshops that took place in Dubna, 1992; Dubna/Volga river tour, 1993; New York, 1994; Moscow/Volga river tour (jointly with NATO SILAP Workshop), 1995; Moscow, 1996; Prague, 1997; Berlin, 1998; Budapest, 1999; Bordeaux, 2000; Moscow, 2001; Bratislava, 2002; Hamburg, 2003; Trieste, 2004; Kyoto, 2005; Lausanne, 2006; León, 2007; Trondheim, 2008; Barcelona, 2009; Foz do Iguaçu, 2010; Sarajevo, 2011; and Calgary, 2012. The total number of participants this year is expected to be about 400. In the past, annual participation was typically from over 30 countries. 2013 Chairmen: Miroslav Jelinek (Czech Republic) and Pavel P Pashinin (Russia) LPHYS'13 will offer eight scientific section seminars and one general symposium: Seminar 1 Modern Trends in Laser Physics Seminar 2 Strong Field & Attosecond Physics Seminar 3 Biophotonics Seminar 4 Physics of Lasers Seminar 5 Nonlinear Optics & Spectroscopy Seminar 6 Physics of Cold Trapped Atoms Seminar 7 Quantum Information Science Seminar 8 Fiber Optics Symposium Extreme Light Technologies, Science and Applications Abstract of your presentation A one-page abstract should contain: title; list of all co-authors (the name of the speaker underlined); affiliations; correspondence addresses including phone numbers, fax numbers, e-mail addresses; and the text of the abstract. Abstracts should be sent to the following co-chairs of the scientific seminars and the symposium: Kirill A Prokhorov (Seminar 1) E-mail: cyrpro@gpi.ru Mikhail V Fedorov (Seminar 2) E-mail: fedorov@ran.gpi.ru Sergey A Gonchukov (Seminar 3) E-mail: gonchukov@mephi.ru Ivan A Shcherbakov (Seminar 4) E-mail: gbufetova@lsk.gpi.ru Vladimir A Makarov (Seminar 5) E

  14. LPHYS'14: 23rd International Laser Physics Workshop (Sofia, Bulgaria, 14-18 July 2014)

    NASA Astrophysics Data System (ADS)

    Yevseyev, Alexander V.

    2014-04-01

    The 23rd annual International Laser Physics Workshop (LPHYS14) will be held from 14 July to 18 July 2014 in the city of Sofia, Bulgaria, at the Ramada Sofia Hotel hosted this year by the Institute of Electronics, Bulgarian Academy of Sciences. LPHYS14 continues a series of workshops that took place in Dubna,1992; Dubna/Volga river tour, 1993; New York, 1994; Moscow/Volga river tour (jointly with NATO SILAP Workshop), 1995; Moscow, 1996; Prague, 1997; Berlin, 1998; Budapest, 1999; Bordeaux, 2000; Moscow, 2001; Bratislava, 2002; Hamburg, 2003; Trieste, 2004; Kyoto, 2005; Lausanne, 2006; Len, 2007; Trondheim, 2008; Barcelona, 2009; Foz do Iguau, 2010; Sarajevo, 2011; Calgary, 2012 and Prague, 2013. The total number of participants this year is expected to be about 400. In the past, annual participation was typically from over 30 countries. 2014 Chairpersons Sanka Gateva (Bulgaria), Pavel Pashinin (Russia) LPHYS14 will offer eight scientific section seminars and one general symposium: Seminar 1 Modern Trends in Laser Physics Seminar 2 Strong Field and Attosecond Physics Seminar 3 Biophotonics Seminar 4 Physics of Lasers Seminar 5 Nonlinear Optics and Spectroscopy Seminar 6 Physics of Cold Trapped Atoms Seminar 7 Quantum Information Science Seminar 8 Fiber Optics Symposium Extreme Light Technologies, Science and Applications Abstract of your presentation A one-page abstract should contain: title; list of all co-authors (the name of the speaker underlined); affiliations; correspondence addresses including phone numbers, fax numbers, e-mail addresses; and the text of the abstract. Abstracts should be sent to the following co-chairs of the scientific seminars and the symposium: Kirill A Prokhorov (Seminar 1) E-mail: cyrpro@gpi.ru Mikhail V Fedorov (Seminar 2) E-mail: fedorov@ran.gpi.ru Sergey A Gonchukov (Seminar 3) E-mail: gonchukov@mephi.ru Ivan A Shcherbakov (Seminar 4) E-mail: gbufetova@lsk.gpi.ru Vladimir A Makarov (Seminar 5) E-mail: makarov@msu.ilc.edu.ru Vyacheslav

  15. A development of red internal mirror He-Ne lasers with near critical concave-convex stable resonators

    SciTech Connect

    Li Xianshu; Chen Yuchuan; Li Taoyu; Wang Yongni; He Yongjun; Gao Yangqiu; Cao Huiying; Deng Shousong

    1996-12-31

    Basic properties of the concave-convex stable resonator (CCSR) with cavity parameter g{sub 1}g{sub 2} near to 1 are discussed in the infinite aperture approximation. The field distributions and diffraction losses of the low order transverse modes of related resonators with finite aperture are analyzed numerically. The stability of the output power of the lasers with CCSR are studied experimentally. The authors have made a total of 120 red internal mirror He-Ne lasers with CCSR (g{sub 1}g{sub 2} {ge} 0.90) whose cavity lengths are approximately 63 cm and the effective lengths of discharge tubes are about 52 cm. Most of the lasers operate with TEM{sub 00} stably, and the highest output power is 30 mw. The laser beam waist lies outside the resonator at a distance of 1.0m from the convex mirror, and the beam divergence is 0.45mrad. For the TEM{sub 00} lasers operate normally, the misalignment angle of the resonator mirrors must be less than 10{sup {minus}5} rad. The following facts are of particular value. (1) When the resonant frequency spacing between two successive transverse modes of a CCSR {Delta}{nu} is so small that its effect on the competition among transverse modes in the lasers with the CCSR can be negligible, such a CCSR is called near critical CCSR (NCSR). It is observed that even if the round trip total loss (including the transmission loss and so on) of TEM{sub 01} is only about 0.2 round trip small signal gain of the laser, and the round trip diffraction loss of TEM{sub 00} is only about 0.001, still the laser with the NCSR operate with pure TEM{sub 00} stably. It is clear that the mode competition in a laser with NCSR is extraordinarily favorable for TEM{sub 00}. (2) While the TEM{sub 00} lasers operate normally, the center frequency of every longitudinal mode is stable, its drift per hour is less than 0.1 longitudinal mode spacing ({approx}2.4 {times} 10{sup 7} Hz). (3) The superradiant transition at 3.30 {micro}m is suppressed.

  16. Velocity measurement inside a motored internal combustion engine using three-component laser Doppler anemometry

    NASA Astrophysics Data System (ADS)

    Chan, V. S. S.; Turner, J. T.

    2000-10-01

    A three-component laser Doppler anemometry (LDA) system has been employed to investigate the structure of the flow inside the cylinder of a motored internal combustion engine. This model engine was reasonably representative of a typical, single cylinder, spark ignition engine although it did not permit firing. It was equipped with overhead valve gear and optical access was provided in the top and side walls of the cylinder. A principal objective was to study the influence of the inlet port design on the flow within the cylinder during the induction and compression strokes of the engine. Here, it can be noted that results obtained in an unfired engine are believed to be representative of the flow behaviour before combustion occurs in a fired engine (see P.O. Witze, Measurements of the spatial distribution and engine speed dependence of turbulent air motion in an i.c. engine, SAE Paper No. 770220, 1977; Witze, Sandia Laboratory Energy Report, SAND 79-8685, Sandia Laboratories, USA, 1979). Experimental data presented for an inclined inlet port configuration reveal the complex three-dimensional nature of the flow inside the model engine cylinder. Not surprisingly, the results also show that the inclined inlet port created flow conditions more favourable to mixing in the cylinder. Specifically, the inclined inlet flow was found to generate a region with a relatively high shear and strong recirculation zones in the cylinder. Inclining the inlet port also produced a more nearly homogeneous flow structure at top dead centre during the compression stroke. The paper identifies the special difficulties encountered in making the LDA measurements. The experimental findings are examined and the problems that arise in presenting time-varying three-dimensional data of this type are discussed. Finally, the future potential of this experimental approach is explored.

  17. 8TH International Laser Physics Workshop Lphys󈨧 Budapest, July 2-6, 1999, Program

    DTIC Science & Technology

    2007-11-02

    Therapy of Squamous Cell Hyperplasia of Vulva 4. I. Manuchin , T. Kraposhina, G. Minkina, T. Zacharova, L. Studenaya (Mos- cow, Russia) Laser Therapy of...Condyloma Acuminata of Vulva 5. G. Minkina, I. Manuchin , L. Studenaya, T. Kraposhina (Moscow, Russia) CO2 laser in the Treatment of the Wide-Spread

  18. Evaluation of the Diode laser (810nm,980nm) on dentin tubule diameter following internal bleaching

    PubMed Central

    Kiomarsi, Nazanin; Salim, Soheil; Sarraf, Pegah; Javad-Kharazifard, Mohammad

    2016-01-01

    Background The aim of this study was to evaluate the effect of diode laser irradiation and bleaching materials on the dentinal tubule diameter after laser bleaching. Material and Methods The dentin discs of 40 extracted third molar were used in this experiment. Each disc surface was divided into two halves by grooving. Half of samples were laser bleached at different wavelengths with two different concentrations of hydrogen peroxide. Other half of each disc with no laser bleaching remained as a negative control. Dentin discs were assigned randomly into four groups (n=10) with following hydrogen peroxide and diode laser wavelength specifications; Group 1 (30% - 810 nm), group 2 (30% - 980 nm), group 3 (46% - 810 nm) and group 4 (46% - 980 nm). All specimens were sent for scanning electron microscopic (SEM) analysis in order to measure tubular diameter in laser treated and control halves. Data were analyzed by ANOVA and Tukey test (p<0.05). Results A significant reduction in dentin tubule diameter was observed in groups 1, 2 and 4. There was no significant difference between groups 1 and 2 and between groups 3 and 4 after bleaching. Conclusions The SEM results showed that diode laser was able to reduce dentin tubule diameter and its effect on dentin was dependent on chemical action of bleaching material. Key words:Laser, diode, dentin, tubule, diameter. PMID:27398172

  19. The proposed flatland radar

    NASA Technical Reports Server (NTRS)

    Green, J. L.; Gage, K. S.; Vanzandt, T. E.; Nastrom, G. D.

    1986-01-01

    A flexible very high frequency (VHF) stratosphere-troposphere (ST) radar configured for meteorological research is to be constructed near Urbana, Illinois. Measurement of small vertical velocities associated with synoptic-scale meteorology can be performed. A large Doppler microwave radar (CHILL) is located a few km from the site of the proposed ST radar. Since the microwave radar can measure the location and velocity of hydrometeors and the VHF ST radar can measure clear (or cloudy) air velocities, simultaneous observations by these two radars of stratiform or convective weather systems would provide valuable meteorological information.

  20. Analysis of synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Blanchard, B. J. (Principal Investigator)

    1976-01-01

    The author has identified the following significant results. Average radar response for L-band like polarized system appeared to be related to the watershed runoff coefficients when the viewing angle was approximately 42 deg off nadir. Four requirements for radar systems used to verify applications of active microwave for water resources were identified: (1) first generation digital data will be required; (2) radar should be calibrated both internally and externally; (3) new systems should avoid radom use; and (4) images should be geometrically rectified prior to delivery to the user.

  1. Space Radar Image of Baikal Lake, Russia

    NASA Image and Video Library

    1999-05-01

    This is an X-band black-and-white image of the forests east of the Baikal Forest in the Jablonowy Mountains of Russia. The image is centered at 52.5 degrees north latitude and 116 degrees east longitude near the mining town of Bukatschatscha. This image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar aboard the space shuttle Endeavour on October 4, 1994, during the second flight of the spaceborne radar. This area is part of an international research project known as the Taiga Aerospace Investigation using Geographic Information System Applications. http://photojournal.jpl.nasa.gov/catalog/PIA01754

  2. Space Radar Image of Baikal Lake, Russia

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is an X-band black-and-white image of the forests east of the Baikal Forest in the Jablonowy Mountains of Russia. The image is centered at 52.5 degrees north latitude and 116 degrees east longitude near the mining town of Bukatschatscha. This image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar aboard the space shuttle Endeavour on October 4, 1994, during the second flight of the spaceborne radar. This area is part of an international research project known as the Taiga Aerospace Investigation using Geographic Information System Applications.

  3. IV INTERNATIONAL CONFERENCE ON ATOM AND MOLECULAR PULSED LASERS (AMPL'99): Discharge characteristics in a nonchain HF(DF) laser

    NASA Astrophysics Data System (ADS)

    Apollonov, V. V.; Kazantsev, S. Yu; Saifulin, A. V.; Firsov, K. N.

    2000-06-01

    It is found that for SF6—hydrocarbon (deuterocarbon) mixtures having a composition typical for nonchain HF(DF) lasers, the electric field strength reduced to the partial pressure of SF6 (pSF6) in the quasistationary phase of a volume self-sustained discharge (E/pSF6)st=92 V m-1 Pa-1 is close to the known critical value (E/p)cr=89 V m-1 Pa-1, which is specified by the condition that the electron-impact ionisation rate of SF6 is equal to the rate of electron attachment to SF6 molecules. This testifies to the decisive role of these two processes and allows the use of the known approximations of the effective ionisation coefficient and the electron drift velocity for pure SF6 when calculating the discharge characteristics. The oscilloscope traces of voltage and current calculated in this approximation for lasers with apertures ranging from 4 to 27 cm deviated from the experimental data by no more than 10%.

  4. Diode-Pumped Solid-State Lasers for Internal Fusion Energy

    SciTech Connect

    Payne, S A; Bibeau, C; Beach, R J; Bayramian, A; Chanteloup, J C; Ebbers, C A; Emanuel, M A; Orth, C D; Rothenberg, J. E; Schaffers, K I; Skidmore, J A; Sutton, S B; Zapata, L E; Powell, H T

    1999-11-15

    We have begun building the ''Mercury'' laser system as the first in a series of new generation diode-pumped solid-state lasers for inertial fusion research. Mercury will integrate three key technologies: diodes, crystals, and gas cooling, within a unique laser architecture that is scalable to kilojoule and megajoule energy levels for fusion energy applications. The primary near-term performance goals include 10% electrical efficiencies at 10 Hz and 100J with a 2-10 ns pulse length at 1.047 mm wavelength. When completed, Mercury will allow rep-rated target experiments with multiple chambers for high energy density physics research.

  5. Weather Radar Technology Development

    DTIC Science & Technology

    1990-08-15

    uelocitV WMs ) data processing systems such as NEXRAD to have a reliable technique for removing ambiguities due to velocity aliasing. Performance of many...intended for automated implementation on radar systems such as the NEXt generation weather RADar ( NEXRAD ) system. Several research areas were addressed...with Doppler radar will soon be realized with the deployment of the NEXRAD radar systems. Some of these large scale storms can have devastating wind

  6. Application of a high-repetition-rate laser diagnostic system for single-cycle-resolved imaging in internal combustion engines.

    PubMed

    Hult, Johan; Richter, Mattias; Nygren, Jenny; Aldén, Marcus; Hultqvist, Anders; Christensen, Magnus; Johansson, Bengt

    2002-08-20

    High-repetition-rate laser-induced fluorescence measurements of fuel and OH concentrations in internal combustion engines are demonstrated. Series of as many as eight fluorescence images, with a temporal resolution ranging from 10 micros to 1 ms, are acquired within one engine cycle. A multiple-laser system in combination with a multiple-CCD camera is used for cycle-resolved imaging in spark-ignition, direct-injection stratified-charge, and homogeneous-charge compression-ignition engines. The recorded data reveal unique information on cycle-to-cycle variations in fuel transport and combustion. Moreover, the imaging system in combination with a scanning mirror is used to perform instantaneous three-dimensional fuel-concentration measurements.

  7. SMAP RADAR Processing and Calibration

    NASA Astrophysics Data System (ADS)

    West, R. D.; Jaruwatanadilok, S.; Kwoun, O.; Chaubell, M. J.

    2013-12-01

    The Soil Moisture Active Passive (SMAP) mission uses L-band radar and radiometer measurements to estimate soil moisture with 4% volumetric accuracy at a resolution of 10 km, and freeze-thaw state at a resolution of 1-3 km. Model sensitivities translate the soil moisture accuracy to a radar backscatter accuracy of 1 dB at 3 km resolution and a brightness temperature accuracy of 1.3 K at 40 km resolution. This presentation will describe the level 1 radar processing and calibration challenges and the choices made so far for the algorithms and software implementation. To obtain the desired high spatial resolution the level 1 radar ground processor employs synthetic aperture radar (SAR) imaging techniques. Part of the challenge of the SMAP data processing comes from doing SAR imaging on a conically scanned system with rapidly varying squint angles. The radar echo energy will be divided into range/Doppler bins using time domain processing algorithms that can easily follow the varying squint angle. For SMAP, projected range resolution is about 250 meters, while azimuth resolution varies from 400 meters to 1.2 km. Radiometric calibration of the SMAP radar means measuring, characterizing, and where necessary correcting the gain and noise contributions from every part of the system from the antenna radiation pattern all the way to the ground processing algorithms. The SMAP antenna pattern will be computed using an accurate antenna model, and then validated post-launch using homogeneous external targets such as the Amazon rain forest to look for uncorrected gain variation. Noise subtraction is applied after image processing using measurements from a noise only channel. Variations of the internal electronics are tracked by a loopback measurement which will capture most of the time and temperature variations of the transmit power and receiver gain. Long-term variations of system performance due to component aging will be tracked and corrected using stable external reference

  8. Lunar radar backscatter studies

    NASA Technical Reports Server (NTRS)

    Thompson, T. W.

    1979-01-01

    The lunar surface material in the Plato area is characterized using Earth based visual, infrared, and radar signatures. Radar scattering in the lunar regolith with an existing optical scattering computer program is modeled. Mapping with 1 to 2 km resolution of the Moon using a 70 cm Arecibo radar is presented.

  9. Radar: Human Safety Net

    ERIC Educational Resources Information Center

    Ritz, John M.

    2016-01-01

    Radar is a technology that can be used to detect distant objects not visible to the human eye. A predecessor of radar, called the telemobiloscope, was first used to detect ships in the fog in 1904 off the German coast. Many scientists have worked on the development and refinement of radar (Hertz with electromagnetic waves; Popov with determining…

  10. Radar: Human Safety Net

    ERIC Educational Resources Information Center

    Ritz, John M.

    2016-01-01

    Radar is a technology that can be used to detect distant objects not visible to the human eye. A predecessor of radar, called the telemobiloscope, was first used to detect ships in the fog in 1904 off the German coast. Many scientists have worked on the development and refinement of radar (Hertz with electromagnetic waves; Popov with determining…

  11. Solar Radar Experiments

    DTIC Science & Technology

    1998-01-01

    communications satellites and electric power grids. RELATED PROJECTS Studies with the HAARP radar facility being constructed in Alaska are conducted with...on wave-plasma interactions and also are assessing the possible use of HAARP as a solar radar. REFERENCES James, J. C., Radar studies of the sun, in

  12. CloudSat as a Global Radar Calibrator

    SciTech Connect

    Protat, Alain; Bouniol, Dominique; O'Connor, E. J.; Baltink, Henk K.; Verlinde, J.; Widener, Kevin B.

    2011-03-01

    The calibration of the CloudSat spaceborne cloud radar has been thoroughly assessed using very accurate internal link budgets before launch, comparisons with predicted ocean surface backscatter at 94 GHz, direct comparisons with airborne cloud radars, and statistical comparisons with ground-based cloud radars at different locations of the world. It is believed that the calibration of CloudSat is accurate to within 0.5 to 1 dB. In the present paper it is shown that an approach similar to that used for the statistical comparisons with ground-based radars can now be adopted the other way around to calibrate other ground-based or airborne radars against CloudSat and / or detect anomalies in long time series of ground-based radar measurements, provided that the calibration of CloudSat is followed up closely (which is the case). The power of using CloudSat as a Global Radar Calibrator is demonstrated using the Atmospheric Radiation Measurement cloud radar data taken at Barrow, Alaska, the cloud radar data from the Cabauw site, The Netherlands, and airborne Doppler cloud radar measurements taken along the CloudSat track in the Arctic by the RASTA (Radar SysTem Airborne) cloud radar installed in the French ATR-42 aircraft for the first time. It is found that the Barrow radar data in 2008 are calibrated too high by 9.8 dB, while the Cabauw radar data in 2008 are calibrated too low by 8.0 dB. The calibration of the RASTA airborne cloud radar using direct comparisons with CloudSat agrees well with the expected gains and losses due to the change in configuration which required verification of the RASTA calibration.

  13. Study of Ultrafast Internal Conversion in Molecules and Ultrafast Dephasing in Condensed Matter with Picosecond Dye Lasers.

    NASA Astrophysics Data System (ADS)

    Xie, Yongjin

    A picosecond cascaded transient oscillator (CTO) dye laser system was modified to generate continuous tunable, near transform-limited picosecond pulses. To improve the CTO system, the characteristics of a simple N_2 laser side-pumped dye laser (the first stage of CTO system) was thoroughly examined. It was found that both the pulse shape and the duration were affected strongly by the tuned wavelength, cavity length, pumping intensity, and the feedback signal from both the front and the back reflectors. A single output pulse as short as 40 ps could be generated by optimizing the operating parameters. The final output of the CTO system has a pulse duration less than 10 ps and a bandwidth less than 1 A. The technique of infrared multiphoton ionization was used to obtain state specific internal conversion rates in CrO_2Cl_2. Using narrow-band tunable 10 ps dye laser pulses, different vibrational states in the B_1 manifold were excited and the energy relaxation was monitored by an IR ps laser pulse. The relaxation can be characterized by a fast component, which is due to internal conversion to the ^1A_1 state, and a slow component, which is due to cooling of the vibrationally hot ^1A _1 ground state. The nonradiative energy transfer rate changes by almost three orders of magnitude for an excess vibrational energy change of merely 550 cm ^{-1}. With broadband incoherent picosecond dye laser pulse, the measurement of the dephasing time T _2 in dye solutions and semiconductor-doped glasses by the two pulse correlation method was demonstrated, with T_2<=ss than the correlation time of the excitation pulse tau_ {rm c}. It was found the dephasing time T_2 measured depended on the excitation photon energy relative to the band-edge or the energy difference between the ground state and the first excited electronic state. In the case of band-edge excitation, a quantum beat behavior with a beat frequency about 28 tera-hertz was observed in Rh-560 dye solutions.

  14. Free Electron Laser for Gamma-Gamma Collider at a Low-Energy Option of International Linear Collider

    SciTech Connect

    Saldin, Evgeny; Schneidmiller, Evgeny; Yurkov, Mikhail; Seryi, Andrei; /SLAC

    2009-10-30

    Different scenarios of a start-up with International Linear Collider (ILC) are under discussion at the moment in the framework of the Global Design Effort (GDE). One of them assumes construction of the ILC in stages from some minimum CM energy up to final target of 500 GeV CM energy. Gamma-gamma collider with CM energy of 180GeV is considered as a candidate for the first stage of the facility. In this report we present conceptual design of a free electron laser as a source of primary photons for the first stage of ILC.

  15. Fluorescence imaging inside an internal combustion engine using tunable excimer lasers.

    PubMed

    Andresen, P; Meijer, G; Schlüter, H; Voges, H; Koch, A; Hentschel, W; Oppermann, W; Rothe, E

    1990-06-01

    Tunable excimer lasers are used to obtain 2-D images of molecular (and some state-specific) density distributions inside a cylinder of a modified four-cylinder in-line engine that has optical access. Natural fluorescence (i.e., without a laser) is used for some OH pictures, normal laser-induced fluorescence (LIF) for those of NO and of the isooctane fuel, and laser-induced predissociative fluorescence (LIPF) for other OH pictures and for those of O(2). Relevant spectroscopy is done to find the laser and fluorescence frequencies needed to measure isolated species. LIPF works well at high pressures, is state specific, and is ideally suited to follow turbulent processes. No similar measurements in engines have been previously reported. Pictures are taken in succeeding engine cycles. Their sequence is either at a particular point of the engine's cycle to show cyclic fluctuations, or at succeeding portions of the cycle to illustrate the progress of the gasdynamics or of the combustion.

  16. [Lasers].

    PubMed

    Passeron, T

    2012-11-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  17. Lasers.

    PubMed

    Passeron, T

    2012-12-01

    Lasers are a very effective approach for treating many hyperpigmented lesions. They are the gold standard treatment for actinic lentigos and dermal hypermelanocytosis, such as Ota nevus. Becker nevus, hyperpigmented mosaicisms, and lentigines can also be successfully treated with lasers, but they could be less effective and relapses can be observed. However, lasers cannot be proposed for all types of hyperpigmentation. Thus, freckles and café-au-lait macules should not be treated as the relapses are nearly constant. Due to its complex pathophysiology, melasma has a special place in hyperpigmented dermatoses. Q-switched lasers (using standard parameters or low fluency) should not be used because of consistent relapses and the high risk of post-inflammatory hyperpigmentation. Paradoxically, targeting the vascular component of the melasma lesion with lasers could have a beneficial effect. However, these results have yet to be confirmed. In all cases, a precise diagnosis of the type of hyperpigmentation is mandatory before any laser treatment, and the limits and the potential side effects of the treatment must be clearly explained to patients.

  18. Radar stage uncertainty

    USGS Publications Warehouse

    Fulford, J.M.; Davies, W.J.

    2005-01-01

    The U.S. Geological Survey is investigating the performance of radars used for stage (or water-level) measurement. This paper presents a comparison of estimated uncertainties and data for radar water-level measurements with float, bubbler, and wire weight water-level measurements. The radar sensor was also temperature-tested in a laboratory. The uncertainty estimates indicate that radar measurements are more accurate than uncorrected pressure sensors at higher water stages, but are less accurate than pressure sensors at low stages. Field data at two sites indicate that radar sensors may have a small negative bias. Comparison of field radar measurements with wire weight measurements found that the radar tends to measure slightly lower values as stage increases. Copyright ASCE 2005.

  19. Partial screening of internal electric fields in strained piezoelectric quantum well lasers: Implications for optoelectronic integration

    NASA Astrophysics Data System (ADS)

    Pabla, A. S.; Woodhead, J.; Khoo, E. A.; Grey, R.; David, J. P. R.; Rees, G. J.

    1996-03-01

    The spectral electroluminescence characteristics of broad-area (Al)GaAs/In0.23Ga0.77As/(Al)GaAs single quantum well separate confinement heterostructure lasers grown on (111)B GaAs have been studied under forward biased current injection. A room-temperature threshold current density of 750 A/cm2 is measured for a 1000 μm laser. The subthreshold electroluminescence spectrum blue shifts with increasing current up to the point of lasing threshold. Our measurements reveal that lasing is achieved while there is a strong residual or ``unscreened'' electric field across the quantum well. Based on these observations we outline how piezoelectric quantum wells can be used to monolithically integrate a quantum well laser with a blue-shifting electroabsorption modulator.

  20. International.

    ERIC Educational Resources Information Center

    Hoover, Linn

    1979-01-01

    The International Geological Correlation Project has attained scientific maturity and broad support and participation by geologists world wide. Its purpose is to provide a mechanism for international cooperation and information exchange about geological problems that transcend national boundaries. (Author/BB)

  1. Fabrication of scattering source for an optical fiber sensor using femtosecond laser internal processing

    NASA Astrophysics Data System (ADS)

    Chinen, Naoki; Shiraishi, Masahiko; Goya, Kenji; Seki, Atsushi; Watanabe, Kazuhiro

    2016-02-01

    Micro-processing by using an ultrashort pulsed laser has been previously reported and developed in the past decade for fabricating micro devices. Using tightly focused short pulse laser beam, the laser intensity easily can reach more than 1013 W/cm2. Under such conditions non-linear phenomena are triggered, hence multiphoton ionization and self-focusing are notably induced in a medium. Femtosecond laser enables micro-fabrication without critical heat damage owing to extremely shorter pulse width and very fast multi-photon absorption at the laser focal point, compared with longer pulse irradiation. In this report, a micro-voids array was created in optical fiber line by using a femtosecond laser to produce sensing area only at local micro-region of the fiber line. At sensing portion consisted of the voids array, transmitted light was partially scattered by voids after that the leaked light could be reflected on the interface of cladding and outsides, which held the incident angle depending on structures of the micro-voids array. Voids array played as a role of scattering sources to transmitted light and consequently it was expected that the transmitted light can be broadly leaked out from the fiber core to the cladding. Furthermore, optical losses attributed to the creation of micro voids were quantitatively obtained so as to figure out the sensor characteristics. Consequently the reflection region which was considered as a sensing area showed the re-coupling rate of 0.04 dB (3.03%) to insertion loss of 1.32 dB, and the incident angle existed between 67.2 -71.9°.

  2. A radar tour of Venus

    NASA Astrophysics Data System (ADS)

    Beatty, J. K.

    1985-06-01

    The surface of Venus is briefly characterized in a summary of results obtained by the Soviet Venera 15 and 16 8-cm synthetic-aperture radars, IR radiometers, and radar altimeters. A series of radar images, mainly from Kotelnikov et al. (1984), are presented and discussed, and the descent vehicles to be released by the two Vega spacecraft as they pass Venus in June 1985 on their way to an encounter with Halley's comet are described. Plans for the missions Phobos (two spacecraft to orbit Mars, rendezvous with Phobos and Deimos, release small instrumented landers, and perform mass spectrometry of vapors released by laser pulses directed at the satellite surfaces, beginning in 1988), a lunar-orbiter mission for 1989-1990, and Vesta (a not-yet-approved 1991 mission comprising a French probe to the asteroid 4 Vesta and perhaps 53 Kalypso and 453 Tea and a Soviet spacecraft to release a kite-supported Venus-atmosphere probe before flying on to an unknown destination) are considered.

  3. Physical working principles of medical radar.

    PubMed

    Aardal, Øyvind; Paichard, Yoann; Brovoll, Sverre; Berger, Tor; Lande, Tor Sverre; Hamran, Svein-Erik

    2013-04-01

    There has been research interest in using radar for contactless measurements of the human heartbeat for several years. While many systems have been demonstrated, not much attention have been given to the actual physical causes of why this work. The consensus seems to be that the radar senses small body movements correlated with heartbeats, but whether only the movements of the body surface or reflections from internal organs are also monitored have not been answered definitely. There has recently been proposed another theory that blood perfusion in the skin could be the main reason radars are able to detect heartbeats. In this paper, an experimental approach is given to determine the physical causes. The measurement results show that it is the body surface reflections that dominate radar measurements of human heartbeats.

  4. 2. VIEW SOUTHWEST, prime search radar tower, height finder radar ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. VIEW SOUTHWEST, prime search radar tower, height finder radar towards, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

  5. Radar Image of Galapagos Island

    NASA Technical Reports Server (NTRS)

    1994-01-01

    This is an image showing part of Isla Isabella in the western Galapagos Islands. It was taken by the L-band radar in HH polarization from the Spaceborne Imaging Radar C/X-Band Synthetic Aperture Radar on the 40th orbit of the space shuttle Endeavour. The image is centered at about 0.5 degree south latitude and 91 degrees west longitude and covers an area of 75 by 60 kilometers (47 by 37 miles). The radar incidence angle at the center of the image is about 20 degrees.

    The western Galapagos Islands, which lie about 1,200 kilometers (750 miles) west of Ecuador in the eastern Pacific, have six active volcanoes similar to the volcanoes found in Hawaii. Since the time of Charles Darwin's visit to the area in 1835, there have been over 60 recorded eruptions of these volcanoes. This SIR-C/X-SAR image of Alcedo and Sierra Negra volcanoes shows the rougher lava flows as bright features, while ash deposits and smooth pahoehoe lava flows appear dark. A small portion of Isla Fernandina is visible in the extreme upper left corner of the image.

    The Galapagos Islands are one of the SIR-C/X-SAR supersites and data of this area will be taken several times during the flight to allow scientists to conduct topographic change studies and to search for different lava flow types, ash deposits and fault lines.

    Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes

  6. Monitoring by holographic radar systems

    NASA Astrophysics Data System (ADS)

    Catapano, Ilaria; Crocco, Lorenzo; Affinito, Antonio; Gennarelli, Gianluca; Soldovieri, Francesco

    2013-04-01

    Nowadays, radar technology represents a significant opportunity to collect useful information for the monitoring and conservation of critical infrastructures. Radar systems exploit the non-invasive interaction between the matter and the electromagnetic waves at microwave frequencies. Such an interaction allows obtaining images of the region under test from which one can infer the presence of potential anomalies such as deformations, cracks, water infiltrations, etc. This information turns out to be of primary importance in practical scenarios where the probed structure is in a poor state of preservation and renovation works must be planned. In this framework, the aim of this contribution is to describe the potentialities of the holographic radar Rascan 4/4000, a holographic radar developed by Remote Sensing Laboratory of Bauman Moscow State Technical University, as a non-destructive diagnostic tool capable to provide, in real-time, high resolution subsurface images of the sounded structure [1]. This radar provides holograms of hidden anomalies from the amplitude of the interference signal arising between the backscattered signal and a reference signal. The performance of the holographic radar is appraised by means of several experiments. Preliminary tests concerning the imaging below the floor and inside wood structures are carried out in controlled conditions at the Electromagnetic Diagnostic Laboratory of IREA-CNR. After, with reference to bridge monitoring for security aim, the results of a measurement campaign performed on the Musmeci bridge are presented [2]. Acknowledgments This research has been performed in the framework of the "Active and Passive Microwaves for Security and Subsurface imaging (AMISS)" EU 7th Framework Marie Curie Actions IRSES project (PIRSES-GA-2010-269157). REFERENCES [1] S. Ivashov, V. Razevig, I. Vasilyev, A. Zhuravlev, T. Bechtel, L. Capineri, The holographic principle in subsurface radar technology, International Symposium to

  7. Quantitative analysis of oxide materials by laser-induced breakdown spectroscopy with argon as an internal standard

    NASA Astrophysics Data System (ADS)

    Lasheras, R. J.; Bello-Gálvez, C.; Anzano, J. M.

    2013-04-01

    Laser-induced breakdown spectroscopy (LIBS) is demonstrated as a quantitative technique for geochemical analysis. This study demonstrates the applicability of LIBS to multielemental analysis of minerals using argon as an internal standard. Laser-induced breakdown spectroscopy has been applied to measure elements in oxide form. In the present study, the contents of several oxides, such as Fe2O3, CaO and MgO, in geological samples from the Tierga Mine (Zaragoza, Spain) were analyzed by LIBS. An argon environment was used to eliminate interference from air at atmospheric pressure. Furthermore, argon was used as an internal standard. The result was enhanced signal and enhanced linearity of the calibration curves. The Fe2O3, CaO and MgO concentrations determined by LIBS were compared with the results obtained using another analytical technique, inductively coupled plasma optical emission spectrometry (ICP-OES). The concentrations found using LIBS were in good agreement with the values obtained by ICP-OES.

  8. Radar based autonomous sensor module

    NASA Astrophysics Data System (ADS)

    Styles, Tim

    2016-10-01

    Most surveillance systems combine camera sensors with other detection sensors that trigger an alert to a human operator when an object is detected. The detection sensors typically require careful installation and configuration for each application and there is a significant burden on the operator to react to each alert by viewing camera video feeds. A demonstration system known as Sensing for Asset Protection with Integrated Electronic Networked Technology (SAPIENT) has been developed to address these issues using Autonomous Sensor Modules (ASM) and a central High Level Decision Making Module (HLDMM) that can fuse the detections from multiple sensors. This paper describes the 24 GHz radar based ASM, which provides an all-weather, low power and license exempt solution to the problem of wide area surveillance. The radar module autonomously configures itself in response to tasks provided by the HLDMM, steering the transmit beam and setting range resolution and power levels for optimum performance. The results show the detection and classification performance for pedestrians and vehicles in an area of interest, which can be modified by the HLDMM without physical adjustment. The module uses range-Doppler processing for reliable detection of moving objects and combines Radar Cross Section and micro-Doppler characteristics for object classification. Objects are classified as pedestrian or vehicle, with vehicle sub classes based on size. Detections are reported only if the object is detected in a task coverage area and it is classified as an object of interest. The system was shown in a perimeter protection scenario using multiple radar ASMs, laser scanners, thermal cameras and visible band cameras. This combination of sensors enabled the HLDMM to generate reliable alerts with improved discrimination of objects and behaviours of interest.

  9. Radar scattering by boulders studied using geometric optics

    NASA Astrophysics Data System (ADS)

    Virkki, A.; Muinonen, K.

    2015-12-01

    We simulate radar scattering from meter-scale boulders of ice and rock using an algorithm of geometric optics. The scattering particles are Gaussian-random-sphere particles with different levels of irregularity. We study the effect of particle size, geometry, and material on the radar albedo and circular polarization ratio at microwaves concentrating on the S-band wavelength of 12.6 cm. We show that increased absorption causes the radar albedos in both polarization states to attenuate exponentially when the contribution of the internally scattered waves decreases. Consequently, also the polarization ratio decreases. Semi-empirical models for the radar albedos are derived.

  10. Proceedings of the International Laser Science Conference (4th) Held in Atlanta, Georgia on 2-7 October 1988 (Advances in Laser Science-4)

    DTIC Science & Technology

    1988-10-07

    Pettevi6, S. K. Gayen, and R. R. Alfano Laser Diode Pumped 11L Nd:YAG and Nd:BEL Lasers ................................... 39 R. Scheps, P. Poirier...J. F. Myers, and D. F. Heller Laser Performance and Tuning Characteristics of a Diode Pumped Nd:YAIO 3 Laser at 1083 am...these parameters and we want to tune into resonance with some specific transition for diode laser pumping or other applLca- tLons. The next thing I listed

  11. The development of a non-contact screening system for rapid medical inspection at a quarantine depot using a laser Doppler blood-flow meter, microwave radar and infrared thermography.

    PubMed

    Matsui, T; Suzuki, S; Ujikawa, K; Usui, T; Gotoh, S; Sugamata, M; Abe, S

    2009-01-01

    In order to conduct fast screening of passengers with infections such as severe acute respiratory syndrome (SARS) or pandemic influenza at a quarantine depot, we developed a non-contact screening system with self-produced program to conduct a human screening within five seconds, via a linear discriminant function from non-contact derived variables, i.e. palmer pulse derived from a laser Doppler blood-flow meter, respiration rate determined by a 10-GHz microwave radar, and facial temperature measured by thermography. The system evaluation was conducted on seven healthy male subjects (23 +/- 1 years). In order to achieve a pseudo-infection condition, the subjects maintained an ergometer exercise load (100 W, 10 minutes). Before (normal condition) and after (pseudo-infection condition) exercise, a significant linear discriminant function (p < 0.001) was determined to distinguish pseudo-infection condition from normal condition (Mahalanobis D-square = 20.3, classification error rate <5%). The proposed system appears promising for future application in fast screening of infection at a quarantine depot.

  12. Development of a non-contact screening system for rapid medical inspection at a quarantine depot using a laser Doppler blood-flow meter, microwave radar and infrared thermography.

    PubMed

    Matsui, T; Suzuki, S; Ujikawa, K; Usui, T; Gotoh, S; Sugamata, M; Badarch, Z; Abe, S

    2009-01-01

    In order to conduct fast screening of passengers with infections such as severe acute respiratory syndrome (SARS) or pandemic influenza at a quarantine depot, we developed a non-contact screening system with a self-produced program to conduct a human screening within five seconds, via a linear discriminant function from non-contact derived variables, i.e. palmer pulse derived from a laser Doppler blood-flow meter, respiration rate determined by a 10-GHz microwave radar, and facial temperature measured by a thermography. The system evaluation was conducted on seven healthy male subjects (23+1 years). In order to achieve a pseudo-infection condition, the subjects maintained an ergo-meter exercise load (100 W, 10 minutes). Before (normal condition) and after (pseudo-infection condition) exercise, a significant linear discriminant function (p50.001) was determined to distinguish the pseudo-infection condition from the normal condition (Mahalanobis D-square 1/4 20.3, classification error rate55%). The proposed system appears promising for future application in fast screening of infection at a quarantine depot.

  13. 3. VIEW NORTHWEST, height finder radar towers, and radar tower ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. VIEW NORTHWEST, height finder radar towers, and radar tower (unknown function) - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

  14. 30. Perimeter acquisition radar building room #318, showing radar control. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. Perimeter acquisition radar building room #318, showing radar control. Console and line printers - Stanley R. Mickelsen Safeguard Complex, Perimeter Acquisition Radar Building, Limited Access Area, between Limited Access Patrol Road & Service Road A, Nekoma, Cavalier County, ND

  15. Common mode frequency instability in internally phase-locked terahertz quantum cascade lasers.

    PubMed

    Wanke, M C; Grine, A D; Fuller, C T; Nordquist, C D; Cich, M J; Reno, J L; Lee, Mark

    2011-11-21

    Feedback from a diode mixer integrated into a 2.8 THz quantum cascade laser (QCL) was used to phase lock the difference frequencies (DFs) among the Fabry-Perot (F-P) longitudinal modes of a QCL. Approximately 40% of the DF power was phase locked, consistent with feedback loop bandwidth of 10 kHz and phase noise bandwidth ~0.5 MHz. While the locked DF signal has ≤ 1 Hz linewidth and negligible drift over ~30 min, mixing measurements between two QCLs and between a QCL and molecular gas laser show that the common mode frequency stability is no better than a free-running QCL. © 2011 Optical Society of America

  16. Educational and retraining programs in the International Laser Center of Moscow State University

    NASA Astrophysics Data System (ADS)

    Makarov, V. A.; Shlenov, S. A.

    2005-10-01

    We present educational programs on nonlinear optics and laser physics in the ILC MSU. These programs are aimed on both full-t ime students of physics faculty and students of retraining courses. As a part of life-l ong learning we offer different types of programs ranging from short courses to one-y ear long retraining programs. These programs include lecture courses, practical work in the training laboratories, and graduate research work in the scientific labs under a supervision of an expert. Special attention will be paid to new tendencies in the educational activities at the ILC MSU: developing and using multimedia courses, short-range practical courses in adjacent fields, constantly developing university teaching laboratory on laser physics and optics.

  17. The proceedings of the 1st international workshop on laboratory astrophysics experiments with large lasers

    SciTech Connect

    Remington, B.A.; Goldstein, W.H.

    1996-08-09

    The world has stood witness to the development of a number of highly sophisticated and flexible, high power laser facilities (energies up to 50 kJ and powers up to 50 TW), driven largely by the world-wide effort in inertial confinement fusion (ICF). The charter of diagnosing implosions with detailed, quantitative measurements has driven the ICF laser facilities to be exceedingly versatile and well equipped with diagnostics. Interestingly, there is considerable overlap in the physics of ICF and astrophysics. Both typically involve compressible radiative hydrodynamics, radiation transport, complex opacities, and equations of state of dense matter. Surprisingly, however, there has been little communication between these two communities to date. With the recent declassification of ICF in the USA, and the approval to commence with construction of the next generation ``superlasers``, the 2 MJ National Ignition Facility in the US, and its equivalent, the LMJ laser in France, the situation is ripe for change. . Given the physics similarities that exist between ICF and astrophysics, one strongly suspects that there should exist regions of overlap where supporting research on the large lasers could be beneficial to the astrophysics community. As a catalyst for discussions to this end, Lawrence Livermore National Laboratory sponsored this workshop. Approximately 100 scientists attended from around the world, representing eight countries: the USA, Canada, UK, France, Germany, Russia, Japan, and Israel. A total of 30 technical papers were presented. The two day workshop was divided into four sessions, focusing on nonlinear hydrodynamics, radiative hydrodynamics, radiation transport, and atomic physics-opacities. Copies of the presentations are contained in these proceedings.

  18. Planetary radar studies

    NASA Technical Reports Server (NTRS)

    Thompson, T. W.; Cutts, J. A.

    1981-01-01

    A catalog of lunar and radar anomalies was generated to provide a base for comparison with Venusian radar signatures. The relationships between lunar radar anomalies and regolith processes were investigated, and a consortium was formed to compare lunar and Venusian radar images of craters. Time was scheduled at the Arecibo Observatory to use the 430 MHz radar to obtain high resolution radar maps of six areas of the lunar suface. Data from 1978 observations of Mare Serenitas and Plato are being analyzed on a PDP 11/70 computer to construct the computer program library necessary for the eventual reduction of the May 1981 and subsequent data acquisitions. Papers accepted for publication are presented.

  19. Internal modification of intrinsic and doped silicon using infrared nanosecond laser

    NASA Astrophysics Data System (ADS)

    Yu, Xiaoming; Wang, Xinya; Chanal, Margaux; Trallero-Herrero, Carlos A.; Grojo, David; Lei, Shuting

    2016-12-01

    We report experimental results of three-dimensional (3D) modification inside intrinsic and doped silicon wafers using laser pulses with 1.55 µm wavelength and 3.5 ns pulse duration. Permanent modification in the form of lines is generated inside silicon by tightly focusing and continuously scanning the laser beam inside samples, without introducing surface damage. Cross sections of these lines are observed after cleaving the samples and are further analyzed after mechanical polishing followed by chemical etching. With the objective lens corrected for spherical aberration, tight focusing inside silicon is achieved and the optimal focal depth is identified. The laser-induced modification has triangular shape and appears in regions prior to the geometrical focus, indicating significant absorption in those regions. Experiments with doped samples show similar modification for doping concentrations (and corresponding initial free carrier densities) in the range of 1013-1016 cm-3. At carrier densities of 1018 cm-3, linear absorption of light becomes significant and the modification is reduced in size.

  20. Historical sketch: Radar geology

    NASA Technical Reports Server (NTRS)

    Macdonald, H.

    1980-01-01

    A chronological assessment is given of the broad spectra of technology associated with radar geology. Particular attention is given to the most recent developments made in the areas of microwave Earth resources applications and geologic remote sensing from aircraft and satellite. The significance of space derived radar in geologic investigations is discussed and the scientific basis for exploiting the sensitivity of radar signals to various aspects of geologic terrain is given.

  1. Bistatic-radar investigation

    NASA Technical Reports Server (NTRS)

    Howard, H. T.; Tyler, G. L.

    1972-01-01

    A bistatic-radar study during the Apollo 15 flight is reviewed, with the orbiting command module as one terminal. Bistatic-radar slopes are compared to geological maps of Copernicus and Riphaeus mountain regions and Kepler region. Basic theory is discussed, including the radar echoes composed of the sum of the reflections from the moon area that is mutually visible from the spacecraft and earth. A signal receiving system and data processing system are outlined schematically.

  2. A Polarization Technique for Mitigating Low Grazing Angle Radar Sea Clutter

    DTIC Science & Technology

    2017-03-03

    and future challenges,” 2008 IEEE International Conference on Radar, pp. 10–16, 2008. [3] M. Greco, F. Gini, A. Younsi, M. Rangaswamy, and A. Zoubir...Non- stationary sea clutter: impact on distubance covariance matrix estimate and detector CFAR,” 2008 IEEE International Conference on Radar, pp. 558...polarimetric CFAR-detector which works on this data,” Record of the IEEE 1990 International Radar Conference, pp. 514-519, 1990. [7] A. De Maio and G

  3. The Comet Radar Explorer Mission

    NASA Astrophysics Data System (ADS)

    Asphaug, Erik; Belton, Mike; Bockelee-Morvan, Dominique; Chesley, Steve; Delbo, Marco; Farnham, Tony; Gim, Yonggyu; Grimm, Robert; Herique, Alain; Kofman, Wlodek; Oberst, Juergen; Orosei, Roberto; Piqueux, Sylvain; Plaut, Jeff; Robinson, Mark; Sava, Paul; Heggy, Essam; Kurth, William; Scheeres, Dan; Denevi, Brett; Turtle, Elizabeth; Weissman, Paul

    2014-11-01

    Missions to cometary nuclei have revealed major geological surprises: (1) Global scale layers - do these persist through to the interior? Are they a record of primary accretion? (2) Smooth regions - are they landslides originating on the surface? Are they cryovolcanic? (3) Pits - are they impact craters or sublimation pits, or rooted in the interior? Unambiguous answers to these and other questions can be obtained by high definition 3D radar reflection imaging (RRI) of internal structure. RRI can answer many of the great unknowns in planetary science: How do primitive bodies accrete? Are cometary nuclei mostly ice? What drives their spectacular activity and evolution? The Comet Radar Explorer (CORE) mission will image the detailed internal structure of the nucleus of 10P/Tempel 2. This ~16 x 8 x 7 km Jupiter Family Comet (JFC), or its parent body, originated in the outer planets region possibly millions of years before planet formation. CORE arrives post-perihelion and observes the comet’s waning activity from safe distance. Once the nucleus is largely dormant, the spacecraft enters a ~20-km dedicated Radar Mapping Orbit (RMO). The exacting design of the RRI experiment and the precise navigation of RMO will achieve a highly focused 3D radar reflection image of internal structure, to tens of meters resolution, and tomographic images of velocity and attenuation to hundreds of meters resolution, tied to the gravity model and shape. Visible imagers will produce maps of the surface morphology, albedo, color, texture, and photometric response, and images for navigation and shape determination. The cameras will also monitor the structure and dynamics of the coma, and its dusty jets, allowing their correlation in 3D with deep interior structures and surface features. Repeated global high-resolution thermal images will probe the near-surface layers heated by the Sun. Derived maps of thermal inertia will be correlated with the radar boundary response, and photometry and

  4. Introduction to Radar Polarimetry

    DTIC Science & Technology

    1991-04-23

    to VI° - SSýSh = fSMI2. But according to the radar formula [143, the power is proportional to the radar cross section , in this case af. Hence we are...knowledge the scattering matrix S can be rewritten as where the phases 4 of the measured voltages and the radar cross sections are made explicit. c...absolute phase the scattering matrix consists ef 8 - 2 - 1 = 5 independent parameters: three radar cross sections and two phase ]ifferences (see Eq.(5.6

  5. Origins of radar

    NASA Astrophysics Data System (ADS)

    Hill, R. D.

    Sessions on the history of thunderstorm and lightning research were held December 11, 1985, at the AGU Fall Meeting in San Francisco, Calif. At that time, since it was well known that lightning researchers were intimately involved in the development of radar and since the 50th anniversary of radar in the United States was at hand, it was suggested that a session on the history of meteorological radar would be appropriate and interesting. The following contribution was presented in the History of Meteorological Radar session May 22, 1986, at the AGU Spring Meeting in Baltimore, Md.

  6. Space Radar Image of Long Island Optical/Radar

    NASA Image and Video Library

    1999-05-01

    visible in the radar image; many of them can also be seen as bright lines i the optical image. The runways of John F. Kennedy International Airport appear as a dark rectangle in Jamaica Bay on the left side of the image. Developed areas appear generally as bright green and orange, while agricultural, protected and undeveloped areas appear darker blue or purple. This contrast can be seen on the barrier islands along the south coast of Long Island, which are heavily developed in the Rockaway and Long Beach areas south and east of Jamaica Bay, but further to the east, the islands are protected and undeveloped. http://photojournal.jpl.nasa.gov/catalog/PIA01785

  7. A Fine-Resolution Radar for Mapping Near-Surface Isochronous Layers

    NASA Astrophysics Data System (ADS)

    Rink, T. P.; Kanagaratnam, P.; Braaten, D.; Zimmerman, K.; Akins, T.; Gogineni, S.

    2005-12-01

    Information on the spatial and temporal variation of snow accumulation is required for interpreting satellite-based radar and laser surface elevation measurements made by CryoSAT and ICESAT altimeters. Current methods of using ice cores and analyzing snow pit stratigraphy is time consuming and prone to errors in spatial representation due to the sparse sampling. Remote sensing methods that can map near-surface internal layers for estimating spatial and temporal variation are required. To accomplish this, we developed a 12-18 GHz FMCW radar to map near-surface layers with 3 cm vertical resolution to a depth of about 10 m. We developed the system to be mobile and self-contained so that spatial variability of the accumulation over a large area can be characterized. The fine resolution of this radar is achieved by its wide bandwidth and by illuminating the target area with a plane-wave, which is implemented using an offset-fed parabolic reflector. Traditional wide-beamwidth antennas are susceptible to spherical wave scattering from off-vertical targets that can potentially mask weaker reflections from internal layers. The radar features a fast transmit waveform synthesizer implemented using a voltage controlled oscillator (VCO) and a phase-locked loop (PLL) using a linear chirp as the reference. The highly linear reference chirp was generated by a direct digital synthesis (DDS) waveform generator and compared against the instantaneous output of the VCO to create a highly linear 12 to 18 GHz transmit chirp. The waveform synthesizer can be swept from 12 to 18 GHz in 500 microseconds. The antenna was mounted on a sled and the radar system was integrated with the antenna feed. We designed and built the sled with a gimbaled antenna mount and sensing control system to ensure that the antenna points at nadir. The radar system was successfully tested at the Summit camp, Greenland, in July 2005. We collected a large amount of data from various locations around Summit camp. The

  8. Combined radar and telemetry system

    DOEpatents

    Rodenbeck, Christopher T.; Young, Derek; Chou, Tina; Hsieh, Lung-Hwa; Conover, Kurt; Heintzleman, Richard

    2017-08-01

    A combined radar and telemetry system is described. The combined radar and telemetry system includes a processing unit that executes instructions, where the instructions define a radar waveform and a telemetry waveform. The processor outputs a digital baseband signal based upon the instructions, where the digital baseband signal is based upon the radar waveform and the telemetry waveform. A radar and telemetry circuit transmits, simultaneously, a radar signal and telemetry signal based upon the digital baseband signal.

  9. Internal absorption coefficient and threshold for pulsed laser disruption of melanosomes isolated from retinal pigment epithelium

    NASA Astrophysics Data System (ADS)

    Jacques, Steven L.; Glickman, Randolph D.; Schwartz, Jon A.

    1996-05-01

    This study determine the threshold radiant exposure from a 10-ns pulsed laser (532 nm) which caused bovine melanosomes to present various observable endpoints of disruption. The endpoints tested were (1) a visible region of clearing in a uniform field of melanosomes under a glass cover slip, (2) an audible sound, and (3) the increase in melanin photoreactivity due to photodisruption of melanosomes. The thresholds were tested for different starting temperatures by pre-equilibrating the melanosomes in aqueous solution at various temperatures. Lower temperatures required larger exposures to attain a given endpoint. The data suggest that bovine RPE melanosomes are about 4-fold denser in melanin content than cutaneous melanosomes.

  10. Radar Sensing for Intelligent Vehicles in Urban Environments

    PubMed Central

    Reina, Giulio; Johnson, David; Underwood, James

    2015-01-01

    Radar overcomes the shortcomings of laser, stereovision, and sonar because it can operate successfully in dusty, foggy, blizzard-blinding, and poorly lit scenarios. This paper presents a novel method for ground and obstacle segmentation based on radar sensing. The algorithm operates directly in the sensor frame, without the need for a separate synchronised navigation source, calibration parameters describing the location of the radar in the vehicle frame, or the geometric restrictions made in the previous main method in the field. Experimental results are presented in various urban scenarios to validate this approach, showing its potential applicability for advanced driving assistance systems and autonomous vehicle operations. PMID:26102493

  11. Radar Sensing for Intelligent Vehicles in Urban Environments.

    PubMed

    Reina, Giulio; Johnson, David; Underwood, James

    2015-06-19

    Radar overcomes the shortcomings of laser, stereovision, and sonar because it can operate successfully in dusty, foggy, blizzard-blinding, and poorly lit scenarios. This paper presents a novel method for ground and obstacle segmentation based on radar sensing. The algorithm operates directly in the sensor frame, without the need for a separate synchronised navigation source, calibration parameters describing the location of the radar in the vehicle frame, or the geometric restrictions made in the previous main method in the field. Experimental results are presented in various urban scenarios to validate this approach, showing its potential applicability for advanced driving assistance systems and autonomous vehicle operations.

  12. space Radar Image of Long Valley, California

    NASA Technical Reports Server (NTRS)

    1994-01-01

    An area near Long Valley, California, was mapped by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar aboard the space shuttle Endeavor on April 13, 1994, during the first flight of the radar instrument, and on October 4, 1994, during the second flight of the radar instrument. The orbital configurations of the two data sets were ideal for interferometric combination -- that is overlaying the data from one image onto a second image of the same area to create an elevation map and obtain estimates of topography. Once the topography is known, any radar-induced distortions can be removed and the radar data can be geometrically projected directly onto a standard map grid for use in a geographical information system. The 50 kilometer by 50 kilometer (31 miles by 31 miles) map shown here is entirely derived from SIR-C L-band radar (horizontally transmitted and received) results. The color shown in this image is produced from the interferometrically determined elevations, while the brightness is determined by the radar backscatter. The map is in Universal Transverse Mercator (UTM) coordinates. Elevation contour lines are shown every 50 meters (164 feet). Crowley Lake is the dark feature near the south edge of the map. The Adobe Valley in the north and the Long Valley in the south are separated by the Glass Mountain Ridge, which runs through the center of the image. The height accuracy of the interferometrically derived digital elevation model is estimated to be 20 meters (66 feet) in this image. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global

  13. space Radar Image of Long Valley, California

    NASA Technical Reports Server (NTRS)

    1994-01-01

    An area near Long Valley, California, was mapped by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar aboard the space shuttle Endeavor on April 13, 1994, during the first flight of the radar instrument, and on October 4, 1994, during the second flight of the radar instrument. The orbital configurations of the two data sets were ideal for interferometric combination -- that is overlaying the data from one image onto a second image of the same area to create an elevation map and obtain estimates of topography. Once the topography is known, any radar-induced distortions can be removed and the radar data can be geometrically projected directly onto a standard map grid for use in a geographical information system. The 50 kilometer by 50 kilometer (31 miles by 31 miles) map shown here is entirely derived from SIR-C L-band radar (horizontally transmitted and received) results. The color shown in this image is produced from the interferometrically determined elevations, while the brightness is determined by the radar backscatter. The map is in Universal Transverse Mercator (UTM) coordinates. Elevation contour lines are shown every 50 meters (164 feet). Crowley Lake is the dark feature near the south edge of the map. The Adobe Valley in the north and the Long Valley in the south are separated by the Glass Mountain Ridge, which runs through the center of the image. The height accuracy of the interferometrically derived digital elevation model is estimated to be 20 meters (66 feet) in this image. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global

  14. Wind Shear radar program future plans

    NASA Technical Reports Server (NTRS)

    Robertson, Roy E.

    1991-01-01

    The status of the Windshear Radar Program at the Collins Air Transport Division of Rockwell International is given in viewgraph form. Topics covered include goals, modifications to the WXR-700 system, flight test plans, technical approaches, design considerations, system considerations, certification, and future plans.

  15. The PROUST radar

    NASA Technical Reports Server (NTRS)

    Bertin, F.; Glass, M.; Ney, R.; Petitdidier, M.

    1986-01-01

    The Stratosphere-Troposphere (ST) radar called PROUST works at 935 MHz using the same klystron and antenna as the coherent-scatter radar. The use of this equipment for ST work has required some important modifications of the transmitting system and the development of receiving, data processing and acquisition (1984,1985) equipment. The modifications are discussed.

  16. Synchronization in multistatic radar

    NASA Astrophysics Data System (ADS)

    Jubrink, H. G.

    1993-08-01

    This report gives a summary of multistatic radar principles and synchronization methods. Different methods are described using direct and indirect synchronization. The report also presents a general review of synchronization methods for the future. Two LORAN C receivers have been analyzed for use as local reference oscillators in multistatic radar.

  17. Quantum radar cross sections

    NASA Astrophysics Data System (ADS)

    Lanzagorta, Marco

    2010-06-01

    The radar cross section σC is an objective measure of the "radar visibility" of an object. As such, σC is an important concept for the correct characterization of the operational performance of radar systems. Furthermore, σC is equally essential for the design and development of stealth weapon systems and platforms. Recent years have seen the theoretical development of quantum radars, that is, radars that operate with a small number of photons. In this regime, the radar-target interaction is described through photon-atom scattering processes governed by the laws of quantum electrodynamics. As such, it is theoretically inconsistent to use the same σC to characterize the performance of a quantum radar. In this paper we define a quantum radar cross section σQ based on quantum electrodynamics and interferometric considerations. We discuss the theoretical challenges of defining σQ, as well as computer simulations of σC and σQ for simple targets.

  18. Polarization Radar Processing Technology

    DTIC Science & Technology

    1989-10-01

    Oi"C FILE ( J qII RADC-TR-89-144 In-House Report October 1989 AD-A215 242 POLARIZATION RADAR PROCESSING TECHNOLOGY Kenneth C. Stiefvater, Russell D...NO. NO. NO. ACCESSION NO. 62702F 4506 11 58 11. TITLE (Include Security Classification) POLARIZATION RADAR PROCESSING TECHNOLOGY 12. PERSONAL AUTHOR(S

  19. Radar illusion via metamaterials

    NASA Astrophysics Data System (ADS)

    Jiang, Wei Xiang; Cui, Tie Jun

    2011-02-01

    An optical illusion is an image of a real target perceived by the eye that is deceptive or misleading due to a physiological illusion or a specific visual trick. The recently developed metamaterials provide efficient approaches to generate a perfect optical illusion. However, all existing research on metamaterial illusions has been limited to theory and numerical simulations. Here, we propose the concept of a radar illusion, which can make the electromagnetic (EM) image of a target gathered by radar look like a different target, and we realize a radar illusion device experimentally to change the radar image of a metallic target into a dielectric target with predesigned size and material parameters. It is well known that the radar signatures of metallic and dielectric objects are significantly different. However, when a metallic target is enclosed by the proposed illusion device, its EM scattering characteristics will be identical to that of a predesigned dielectric object under the illumination of radar waves. Such an illusion device will confuse the radar, and hence the real EM properties of the metallic target cannot be perceived. We designed and fabricated the radar illusion device using artificial metamaterials in the microwave frequency, and good illusion performances are observed in the experimental results.

  20. Noncooperative rendezvous radar system

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A fire control radar system was developed, assembled, and modified. The baseline system and modified angle tracking system are described along with the performance characteristics of the baseline and modified systems. Proposed changes to provide additional techniques for radar evaluation are presented along with flight test data.

  1. Java Radar Analysis Tool

    NASA Technical Reports Server (NTRS)

    Zaczek, Mariusz P.

    2005-01-01

    Java Radar Analysis Tool (JRAT) is a computer program for analyzing two-dimensional (2D) scatter plots derived from radar returns showing pieces of the disintegrating Space Shuttle Columbia. JRAT can also be applied to similar plots representing radar returns showing aviation accidents, and to scatter plots in general. The 2D scatter plots include overhead map views and side altitude views. The superposition of points in these views makes searching difficult. JRAT enables three-dimensional (3D) viewing: by use of a mouse and keyboard, the user can rotate to any desired viewing angle. The 3D view can include overlaid trajectories and search footprints to enhance situational awareness in searching for pieces. JRAT also enables playback: time-tagged radar-return data can be displayed in time order and an animated 3D model can be moved through the scene to show the locations of the Columbia (or other vehicle) at the times of the corresponding radar events. The combination of overlays and playback enables the user to correlate a radar return with a position of the vehicle to determine whether the return is valid. JRAT can optionally filter single radar returns, enabling the user to selectively hide or highlight a desired radar return.

  2. Laser Disks at the Library Door: The Microsoft First International Conference on CD-ROM.

    ERIC Educational Resources Information Center

    Miller, David C.

    1986-01-01

    Description of First International CD-ROM Conference held by Microsoft, Inc., in March, 1986, covers types of participants, hardware and support services, and technical standards and intellectual property rights as market barriers. The importance of librarians planning for CD-ROM is stressed, and a detailed directory of references and contacts is…

  3. Intelligent radar data processing

    NASA Astrophysics Data System (ADS)

    Holzbaur, Ulrich D.

    The application of artificial intelligence principles to the processing of radar signals is considered theoretically. The main capabilities required are learning and adaptation in a changing environment, processing and modeling information (especially dynamics and uncertainty), and decision-making based on all available information (taking its reliability into account). For the application to combat-aircraft radar systems, the tasks include the combination of data from different types of sensors, reacting to electronic counter-countermeasures, evaluation of how much data should be acquired (energy and radiation management), control of the radar, tracking, and identification. Also discussed are related uses such as monitoring the avionics systems, supporting pilot decisions with respect to the radar system, and general applications in radar-system R&D.

  4. Micropower impulse radar imaging

    SciTech Connect

    Hall, M.S.

    1995-11-01

    From designs developed at the Lawrence Livermore National Laboratory (LLNL) in radar and imaging technologies, there exists the potential for a variety of applications in both public and private sectors. Presently tests are being conducted for the detection of buried mines and the analysis of civil structures. These new systems use a patented ultra-wide band (impulse) radar technology known as Micropower Impulse Radar (GPR) imaging systems. LLNL has also developed signal processing software capable of producing 2-D and 3-D images of objects embedded in materials such as soil, wood and concrete. My assignment while at LLNL has focused on the testing of different radar configurations and applications, as well as assisting in the creation of computer algorithms which enable the radar to scan target areas of different geometeries.

  5. Spaceborne weather radar

    NASA Technical Reports Server (NTRS)

    Meneghini, Robert; Kozu, Toshiaki

    1990-01-01

    The present work on the development status of spaceborne weather radar systems and services discusses radar instrument complementarities, the current forms of equations for the characterization of such aspects of weather radar performance as surface and mirror-image returns, polarimetry, and Doppler considerations, and such essential factors in spaceborne weather radar design as frequency selection, scanning modes, and the application of SAR to rain detection. Attention is then given to radar signal absorption by the various atmospheric gases, rain drop size distribution and wind velocity determinations, and the characteristics of clouds, as well as the range of available estimation methods for backscattering, single- and dual-wavelength attenuation, and polarimetric and climatological characteristics.

  6. Meteorological radar calibration

    NASA Technical Reports Server (NTRS)

    Hodge, D. B.

    1978-01-01

    A meteorological radar calibration technique is developed. It is found that the integrated, range corrected, received power saturates under intense rain conditions in a manner analogous to that encountered for the radiometric path temperature. Furthermore, it is found that this saturation condition establishes a bound which may be used to determine an absolution radar calibration for the case of radars operating at attenuating wavelengths. In the case of less intense rainfall or for radars at nonattenuating wavelengths, the relationship for direct calibration in terms of an independent measurement of radiometric path temperature is developed. This approach offers the advantage that the calibration is in terms of an independent measurement of the rainfall through the same elevated region as that viewed by the radar.

  7. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    SciTech Connect

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; Van Berkel, Gary J.

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to compare internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.

  8. Comparison of Internal Energy Distributions of Ions Created by Electrospray Ionization and Laser Ablation-Liquid Vortex Capture-Electrospray Ionization

    DOE PAGES

    Cahill, John F.; Kertesz, Vilmos; Ovchinnikova, Olga S.; ...

    2015-06-27

    Recently a number of techniques have combined laser ablation with liquid capture for mass spectrometry spot sampling and imaging applications. The newly developed non-contact liquid-vortex capture probe has been used to efficiently collect 355 nm UV laser ablated material in a continuous flow solvent stream in which the captured material dissolves and then undergoes electrospray ionization. This sampling and ionization approach has produced what appear to be classic electrospray ionization spectra; however, the softness of this sampling/ionization process versus simple electrospray ionization has not been definitely determined. A series of benzlypyridinium salts, known as thermometer ions, were used to comparemore » internal energy distributions between electrospray ionization and the UV laser ablation liquid-vortex capture probe electrospray combination. Measured internal energy distributions were identical between the two techniques, even with differences in laser fluence (0.7-3.1 J cm-2) and when using UV-absorbing or non-UV-absorbing sample substrates. This data indicates ions formed directly by UV laser ablation, if any, are likely an extremely small constituent of the total ion signal observed. Instead, neutral molecules, clusters or particulates ejected from the surface during laser ablation, subsequently captured and dissolved in the flowing solvent stream then electrosprayed are the predominant source of ion signal observed. The electrospray ionization process used controls the softness of the technique.« less

  9. Non-specific internalization of laser ablated pure gold nanoparticles in pancreatic tumor cell.

    PubMed

    Sobhan, M A; Sreenivasan, V K A; Withford, M J; Goldys, E M

    2012-04-01

    We investigate the intracellular uptake of 7.3 nm, 21.2 nm and 31.3 nm average size pure colloidal gold nanoparticles synthesized using femtosecond laser ablation technique in pure water. Dark-field imaging, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) was used to assess the uptake of these pure gold nanoparticles in the pancreatic tumor cell line. We show that these ligand-free gold nanoparticles are non-toxic to these cells. The nanoparticles and cell images indicated that unmodified gold nanoparticles interacted with the cells, despite negative surface charge on both the cells and the nanoparticles. We also demonstrate that the uptake of the gold nanoparticles is size-dependent.

  10. 4. VIEW NORTHEAST, radar tower (unknown function), prime search radar ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    4. VIEW NORTHEAST, radar tower (unknown function), prime search radar tower, emergency power building, and height finder radar tower - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

  11. 5. VIEW EAST, height finder radar towers, radar tower (unknown ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VIEW EAST, height finder radar towers, radar tower (unknown function), prime search radar tower, operations building, and central heating plant - Fort Custer Military Reservation, P-67 Radar Station, .25 mile north of Dickman Road, east of Clark Road, Battle Creek, Calhoun County, MI

  12. Accuracy analysis of the 2014-2015 Global Shuttle Radar Topography Mission (SRTM) 1 arc-sec C-Band height model using International Global Navigation Satellite System Service (IGS) Network

    NASA Astrophysics Data System (ADS)

    Mukul, Manas; Srivastava, Vinee; Mukul, Malay

    2016-07-01

    Global Shuttle Radar Topography Mission (SRTM) data products have been widely used in Earth Sciences without an estimation of their accuracy and reliability even though large outliers exist in them. The global 1 arc-sec, 30 m resolution, SRTM C-Band (C-30) data collected in February 2000 has been recently released (2014-2015) outside North America. We present the first global assessment of the vertical accuracy of C-30 data using Ground Control Points (GCPs) from the International GNSS Service (IGS) Network of high-precision static fiducial stations that define the International Terrestrial Reference Frame (ITRF). Large outliers (height error ranging from -1285 to 2306 m) were present in the C-30 dataset and 14% of the data were removed to reduce the root mean square error (RMSE) of the dataset from ˜187 to 10.3 m which is close to the SRTM goal of an absolute vertical accuracy of RMSE ˜10 m. Globally, for outlier-filtered data from 287 GCPs, the error or difference between IGS and SRTM heights exhibited a non-normal distribution with a mean and standard error of 6.5 ± 0.5 m. Continent-wise, only Australia, North and South America complied with the SRTM goal. At stations where all the X- and C-Band SRTM data were present, the RMSE of the outlier-filtered C-30 data was 11.7 m. However, the RMSE of outlier-included dataset where C- and X-Band data were present was ˜233 m. The results suggest that the SRTM data must only be used after regional accuracy analysis and removal of outliers. If used raw, they may produce results that are statistically insignificant with RMSE in 100s of meters.

  13. Spaceborne imaging radar - Geologic and oceanographic applications

    NASA Technical Reports Server (NTRS)

    Elachi, C.

    1980-01-01

    Synoptic, large-area radar images of the earth's land and ocean surface, obtained from the Seasat orbiting spacecraft, show the potential for geologic mapping and for monitoring of ocean surface patterns. Structural and topographic features such as lineaments, anticlines, folds and domes, drainage patterns, stratification, and roughness units can be mapped. Ocean surface waves, internal waves, current boundaries, and large-scale eddies have been observed in numerous images taken by the Seasat imaging radar. This article gives an illustrated overview of these applications.

  14. Radar Thickness Measurements over the Southern Part of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Chuah, Teong Sek; Gogineni, Siva Prasad; Allen, Christopher; Wohletz, Brad; Wong, Y. C.; Ng, P. Y.; Ajayi, E.

    1996-01-01

    We performed ice thickness measurements over the southern part of the Greenland ice sheet during June and July 1993. We used an airborne coherent radar depth sounder for these measurements. The radar was operated from a NASA P-3 aircraft equipped with GPS receivers. Radar data were collected in conjunction with laser altimeter and microwave altimeter measurements of ice surface elevation. This report provides radio echograms and thickness profiles from data collected during 1993.

  15. Quantitative analysis of soil calcium by laser-induced breakdown spectroscopy using addition and addition-internal standardizations

    NASA Astrophysics Data System (ADS)

    Shirvani-Mahdavi, Hamidreza; Shafiee, Parisa

    2016-12-01

    Matrix mismatching in the quantitative analysis of materials through calibration-based laser-induced breakdown spectroscopy (LIBS) is a serious problem. In this paper, to overcome the matrix mismatching, two distinct approaches named addition standardization (AS) and addition-internal combinatorial standardization (A-ICS) are demonstrated for LIBS experiments. Furthermore, in order to examine the efficiency of these methods, the concentration of calcium in ordinary garden soil without any fertilizer is individually measured by each of the two procedures. To achieve this purpose, ten standard samples with different concentrations of calcium (as the analyte) and copper (as the internal standard) are prepared in the form of cylindrical tablets, so that the soil plays the role of the matrix in all of them. The measurements indicate that the relative error of concentration compared to a certified value derived by induced coupled plasma optical emission spectroscopy is 3.97% and 2.23% for AS and A-ICS methods, respectively. Furthermore, calculations related to standard deviation indicates that A-ICS method may be more accurate than AS one.

  16. Correction of self-absorption effect in calibration-free laser-induced breakdown spectroscopy by an internal reference method.

    PubMed

    Sun, Lanxiang; Yu, Haibin

    2009-07-15

    A simplified procedure for correcting self-absorption effect was proposed in calibration-free laser-induced breakdown spectroscopy (CF-LIBS). In typical LIBS measurement conditions, the plasma produced is often optically thick, especially for the strong lines of major elements. The selection of self-absorption lines destroys the performance of CF-LIBS, and the familiar correction method based on the curve of growth is complex in implementation. The procedure we proposed, named internal reference for self-absorption correction (IRSAC), first chose an internal reference line for each species, then compared other spectral line intensity of the same species with the reference line to estimate the self-absorption degrees of other spectral lines, and finally achieved an optimal correction by a regressive algorithm. The self-absorption effect of the selected reference line can be ignored, since the reference line with high excitation energy of the upper level is slightly affected by the self-absorption. Through the IRSAC method, the points on the Boltzmann plot become more regular, and the evaluations of the plasma temperature and material composition are more accurate than the basic CF-LIBS.

  17. Simulation of error in optical radar range measurements.

    PubMed

    Der, S; Redman, B; Chellappa, R

    1997-09-20

    We describe a computer simulation of atmospheric and target effects on the accuracy of range measurements using pulsed laser radars with p-i-n or avalanche photodiodes for direct detection. The computer simulation produces simulated images as a function of a wide variety of atmospheric, target, and sensor parameters for laser radars with range accuracies smaller than the pulse width. The simulation allows arbitrary target geometries and simulates speckle, turbulence, and near-field and far-field effects. We compare simulation results with actual range error data collected in field tests.

  18. Radar Imaging with a Network of Digital Noise Radar Systems

    DTIC Science & Technology

    2009-03-01

    III. Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.1 Radar Range Equation and Radar Cross Section . . . . . 29 3.2 UWB...noise radar system. This particular ap- plication tracked a corner reflector that moved from a range of 40 ft to 185 ft from the radar while using an...target scenario and the resulting SAR image. In this test, a radar was placed outside a room with a trihedral reflector placed on the other side of the

  19. Radar remote sensing in biology

    USGS Publications Warehouse

    Moore, Richard K.; Simonett, David S.

    1967-01-01

    The present status of research on discrimination of natural and cultivated vegetation using radar imaging systems is sketched. The value of multiple polarization radar in improved discrimination of vegetation types over monoscopic radars is also documented. Possible future use of multi-frequency, multi-polarization radar systems for all weather agricultural survey is noted.

  20. Spaceborne meteorological radar studies

    NASA Technical Reports Server (NTRS)

    Meneghini, R.

    1988-01-01

    Various radar designs and methods are studied for the estimation of rainfall parameters from space. An immediate goal is to support the development of the spaceborne radar that has been proposed for the Tropical Rain Measuring Mission (TRMM). The effort is divided into two activities: a cooperative airborne rain measuring experiment with the Radio Research Laboratory of Japan (RRL), and the modelling of spaceborne weather radars. An airborne rain measuring experiment was conducted at Wallops Flight Facility in 1985 to 1986 using the dual-wavelength radar/radiometer developed by RRL. The data are presently being used to test a number of methods that are relevant to spaceborne weather radars. An example is shown of path-averaged rain rates as estimated from three methods: the standard reflectivity rain rate method (Z-R), a dual-wavelength method, and a surface reference method. The results from the experiment shows for the first time the feasibility of using attenuation methods from space. The purposes of the modelling are twofold: to understand in a quantitative manner the relationships between a particular radar design and its capability for estimating precipitation parameters and to help devise and test new methods. The models are being used to study the impact of various TRMM radar designs on the accuracy of rain rate estimation as well as to test the performance of range-profiling algorithms, the mirror-image method, and some recently devised graphical methods for the estimation of the drop size distribution.