bluuebunny/crossref_metadata_2025 huggingface dataset:
The apparent burden of unexplained sudden infant deaths in Lusaka, Zambia: Findings from analysis of verbal autopsies
Authors: Osei-Poku Godwin K. , Mwananyanda Lawrence , Elliott Patricia A. , MacLeod William B. , Somwe Somwe Wa , Pieciak Rachel C. , Gill Christopher J.
Published: February 2023

Background: The contribution of sudden unexpected infant death (SUID) has received little attention in global health. The objective of this study was to estimate the burden of SUID in Lusaka, Zambia.

Methods: Verbal autopsies were conducted on infants who died in Lusaka, between 2017 and 2020.  From these, we performed a qualitative analysis of the free text narratives of the final series of events leading to each infant’s death and classified these as symptomatic deaths or SUID. Any narrative that described an infant who was otherwise healthy with no antecedent illness prior to death and found dead in bed after a sleep episode was classified as SUID. We used logistic regression to test for statistical differences between asymptomatic deaths and SUIDs on key infant, maternal and other risk factors of SUIDs.

Results: Eight hundred and nine verbal autopsies were conducted with families of decedent infants younger than six months of age. A total of 92.6% (749/809) had presented with symptoms prior to death, whereas 7.4% (60/809) died without preceding symptoms or obvious cause of death. Of these, 16/60 were compatible with accidental suffocation deaths, and 54/60 appeared to be sudden infant death syndrome.  SUID deaths were concentrated in infants younger than two months of age with peak age of one to two months. Age at death was the only significant factor in multivariate analysis. Infants aged between one and two months had 2.84 increased odds of suspected SUIDs compared to infants in the first month of life (aOR = 2.84, 95% CI: 1.31, 6.16).

Conclusions: Our findings suggest SUID could be accounting for a significant proportion of infant deaths in Zambia, but this cause of infant mortality is going unrecognized. Public health interventions in Zambia, and Africa more broadly, are likely overlooking SUIDs as an important cause of infant mortality.
Phylogeny-wide analysis of G-protein coupled receptors in social amoebas and implications for the evolution of multicellularity
Authors: Hall Grant , Kelly Sarah , Schaap Pauline , Schilde Christina
Published: February 2023

G-protein coupled receptors (GPCRs) are seven-transmembrane proteins and constitute the largest group of receptors within eukaryotes. The presence of a large set of GPCRs in the unicellular Amoebozoa was surprising and is indicative of the largely undiscovered environmental sensing capabilities in this group. Evolutionary transitions from unicellular to multicellular lifestyles, like we see in social amoebas, have occurred several times independently in the Amoebozoa, and GPCRs may have been co-opted for new functions in cell-cell communication.

Methods

We have analysed a set of GPCRs from fully sequenced Amoebozoan genomes by Bayesian inference, compared their phylogenetic distribution and domain composition, and analysed their temporal and spatial expression patterns in five species of dictyostelids.

Results

We found evidence that most GPCRs are conserved deeply in the Amoebozoa and are probably performing roles in general cell functions and complex environmental sensing. All families of GPCRs (apart from the family 4 fungal pheromone receptors) are present in dictyostelids with family 5 being the largest and family 2 the one with the fewest members. For the first time, we identify the presence of family 1 rhodopsin-like GPCRs in dictyostelids. Some GPCRs have been amplified in the dictyostelids and in specific lineages thereof and through changes in expression patterns may have been repurposed for signalling in multicellular development.

Discussion

Our phylogenetic analysis suggests that GPCR families 1, 2 and 6 already diverged early in the Amoebozoa, whereas families 3 and 5 expanded later within the dictyostelids. The family 6 cAMP receptors that have experimentally supported roles in multicellular development in dictyostelids (carA-carD; tasA/B) originated at the root of all dictyostelids and only have weakly associated homologs in Physarum polycephalum. Our analysis identified candidate GPCRs which have evolved in the dictyostelids and could have been co-opted for multicellular development.
IoT on Wheels
Authors: De WAARD Gerrit
Published: February 2023

CHANGING CUSTOMER DEMANDS ARE PUSHING VEHICLE MANUFACTURERS TO INCORPORATE TECHNOLOGIES THAT CAN COLLECT VAST AMOUNTS OF DATA FOR ANALYSIS. FORTUNATELY THERE ARE FIRMS READILY ABLE TO ASSIST THEM
Bend-resistant stress-type segmented cladding large-mode-area single-mode fibers
Authors: Wang Yajie , Hou Shanglin , Xie Caijian , Wu Gang , Yan Zuyong
Published: February 2023

We propose a novel bend-resistant stress-type large-mode-area fiber with segmented cladding, to the best of our knowledge, in which a high refractive index stress rod is introduced at the core, to improve the loss ratio between the least high-order mode (HOM) and fundamental mode loss, and to reduce the fundamental mode loss effectively. The mode loss and effective mode field area with or without heat load, and mode field evolution between the straight and bending transition are investigated, by utilizing the finite element method and the coupled-mode theory. The results show that the effective mode field area and the loss of the fundamental mode can reach up to 1050.1 µm2 and 0.0055dB⋅m−1, respectively, and the loss ratio between the least loss HOM and fundamental mode loss is greater than 210. The coupling efficient of the fundamental mode in the straight-bending transition reaches 0.85 at a wavelength of 1.064 µm and a bending radius of 24 cm. In addition, the fiber is insensitive to the bending direction and has excellent single-mode performance in any bending direction; the fiber maintains single-mode operation under heat load from 0 to 8 W/m. This fiber has potential application in compact fiber lasers and amplifiers.
The Air Force Air Weather Service's Requirements for Global Meteorological Data
Authors: Moore Douglas A. , Peterson Robert E.
Published: February 2023

Air Weather Service (AWS) provides weather support to the Air Force, Army, the Department of Defense, and designated joint and combined operations in wartime and in peacetime. Army support is primarily centered on the battlefield while support to the Air Force extends from the drawing board to the battlefield. Support to weapons system designers helps optimize the effectiveness of weapon systems and minimizes the risk of severely degraded performance in adverse weather situations. Battlefield support ranges from observations of traditional weather elements at airfields to forecasts of lock-on range for precision guided munitions (PGMs). To provide this support, AWS uses observations that potentially at least could be enhanced using coherent laser radar technology.
Remote Sensing at EPA: Present Uses and Future Needs
Authors: Wilson William E. , Conner William
Published: February 2023

Some of EPA's current uses and future needs for remote sensing techniques will be reviewed. Future needs and current developments will be outlined.
CO2 Laser Radar Systems Technology Development for Remote Atmospheric Measurement
Authors: Jelalian A. V.
Published: February 2023

This paper describes the historical development of CO2 laser radar systems and technology as it relates to remote atmospheric sensing. Laboratory, ground-based, and flight test system results encompassing the past 15 years of applied research and development will be presented along with an assessment of current technology status.
100 Watt Average Power CO2 Laser System for Pulsed Coherent Lidar Applications
Authors: Moody S. E. , Znotins T. A. , Byron S. R.
Published: February 2023

Pulsed coherent Doppler lidars operating at CO2 wavelengths have shown considerable promise for remote measurement of wind velocities. Range and data rates are limited at present by the single pulse energy and repetition rates available from current generation pulsed CO2 lasers. Recently, we have undertaken the development of a laser system for pulsed lidar application which is capable of producing 2 Joule pulses at a 50 Hz repetition rate. This laser will be installed in the NOAA ground-based Doppler lidar system.1 The laser system is designed to be tunable over a wide range of lines, including the 9 μm band of CO2, and to allow pulse length variability, which is relevant to DIAL applications. The laser system includes a cw local oscillator which is frequency locked to the transmitted pulse for use in the heterodyne receiver. Table 1 summarizes the specifications of the system under construction.
Modular CO2 Laser Radars for Atmospheric Sensing
Authors: Krause M. C. , Chandler R. L. , Dimarzio C. A. , Dickson D. , Donaldson R.
Published: February 2023

Until recently CO2 laser radar systems have been designed and developed specifically for each new application. In many cases this was required to incorporate the latest technology or to meet specific size or performance constraints. With the advent of waveguide lasers, high speed microprocessors, and advanced optical and electronic components, it is now possible to design standardized, modular CO2 laser radars. This approach provides a highly flexible and cost effective method for meeting the requirements of many ground based and airborne atmospheric sensing applications.
An Airborne Coherent Lidar for Turbulence Measurement
Authors: Keeler R. Jeffrey , Serafin Robert J.
Published: February 2023

The reliability of airborne laser systems using coherent CW C02 lasers has progressed to nearly operational status during the last five years. The Atmospheric Technology Division at the National Center for Atmospheric Reserach (NCAR) has an interest in supplementing and providing an alternative to its present gust probe air motion sensors (velocity and turbulence) on board its research aircraft. A future aircraft will probably serve as an airborne platform for remote sensor systems, such as a Doppler radar and a laser radar system in addition to the standard airborne in-situ sensors.
Polarization Measurements with a Pulsed Coherent CO2 Doppler Lidar
Authors: Singstad Ingar
Published: February 2023

The information content in lidar backscattering data is enhanced by measuring the depolarization properties of the backscattered beams rather than intensities alone.
Coherent Lidar Measurement of Range-Resolved Tropospheric Water Vapor Concentration and Backscattered Signal Statistics
Authors: Hardesty R.M.
Published: February 2023

The sensitivity advantages of coherent detection can potentially be employed to make range-resolved differential absorption lidar (DIAL) measurements of atmospheric species even when transmit pulse energies are relatively low. By operating in a shot-noise-limited mode, coherent lidars often obtain average carrier-to-noise ratios (CNR's) as much as 30 dB higher than would be measured with equivalent direct-detection systems. This apparent advantage in average CNR is at least partially offset by the characteristically large fluctuation in the instantaneous received irradiance due to target speckle effects.1 To measure mean backscattered-signal irradiance accurately, the variance due to these fluctuations must be reduced to an acceptable level by averaging.
A Scenario on Remote Sensing of Temperature and Humidity by Lidar Techniques
Authors: Kattawar G. W.
Published: February 2023

An overview of the most promising techniques for range-resolved remote sensing of temperature and humidity will be presented. These include spectroscopy of the unshifted Rayleigh line, as well as Raman and DIAL techniques.
Atmospheric Aerosol Backscatter Models in the Infrared
Authors: Kent G. S. , Yue G. K. , Farrukh U. , Deepak A.
Published: February 2023

A review is given of the problems encountered in modeling atmospheric aerosol backscattering at infrared wavelengths,βIR. The region of the atmosphere discussed is the lowest 20 kilometers; the main emphasis of the review is on the scattering properties at CO2 laser wavelengths (9.1 to 11.1 μm) but scattering at the Nd-YAG laser wavelength (1.06 μm) will also be discussed together with the results of calculations carried out for intermediate wavelengths. The review contains a summary of the relevant aerosol characteristics and the different methods of calculating the aerosol backscattering function, both from measured aerosol characteristics and from optical measurements made at other wavelengths, are described and their accuracy assessed. Effects of changing atmospheric humidity and temperature on the backscatter are presented and related to the real atmosphere. Modeled values for aerosol backscatter for different geographical regions and at different heights above the earth's surface are given.
Airborne and Ground-Based Measurement of Atmospheric Aerosol Backscatter at CO2 Laser Wavelengths
Authors: Jones William D.
Published: February 2023

Measurement of atmospheric winds by lidars is dependent upon receiving sufficient reflected laser radiation to allow reliable velocity estimates. The signal intensity is in turn dependent on the "reflectivity" of the atmosphere. However, this "reflectivity" (more properly termed atmospheric backscatter coefficient) is not constant, but rather varies with geographic location, season, altitude, etc. There are several ways that the reflectivity may be estimated - extrapolation from visible and near-ir backscatter, extinction measurements, and particle sizing and prediction based on Mie theory.
Multiple Scattering by Spherical and Cylindrical Particles
Authors: Cohen Ariel , Egert Smadar
Published: February 2023

Double-scattering calculations by a cloud of randomly oriented long cylinders in a lidar geometry are presented. Triple scattering involving Raman Mie processes by spherical cloud particles is also discussed.
Comparison of the Observed Antenna Gain Properties of the NOAA Doppler Lidar with Theory
Authors: Lawrence T. R.
Published: February 2023

Calibration of coherent lidar sensitivity and applications that use the observed signal magnitude (e.g., backscatter coefficient profiling) require accurate knowledge of the antenna gain. The effective antenna gain includes a contribution due to propagation effects (molecular and particulate extinction and phase distortion due to refractive index inhomogeneities). This contribution can be estimated by measurement of pertinent parameters (e.g., humidity, Cn2) and computation of the resulting loss at the applicable wavelength (10.59 μ). Lidar system contribution to the antenna gain (i.e., the free space gain) is a function of the telescope diameter, the range at which the telescope is focused, beam illumination patterns on the transmitter and receiver apertures and optical system aberrations. Theoretical free space gain curves can be generated when these quantities are known. Observations of aerosol backscatter and discrete target returns have been compared with predictions of antenna gain calculations. Good agreement exists between experiment and theory which indicates that the antenna gain properties of the NOAA Doppler lidar are well understood. Results are also presented on the amplitude calibration of the lidar.
Absolute Calibration of a 10.6 μm CW Coherent Laser Radar
Authors: Foord R , Jones R , Vaughan J M , Willetts D V
Published: February 2023

The signal to noise ratio expected theoretically in coherent, infra-red, heterodyne systems has been well documented for many years. In practice however it is usually accepted as a general rule that up to an order of magnitude degradation of experiment with theory will be found. At the last Aspen conference on coherent laser radar systems in 1980 the closest agreement claimed by any worker in the field was a loss factor of ~ 4 (discussion session). Just such a loss factor was reported in an early paper by Brandewie and Davis1 with a cw system and in more recent calibrations by several workers2,3. It has been suggested that these discrepancies, between predicted and observed signal to noise ratios, might be due at least in part to assumption of over optimistic values for the quantum efficiency of the detector, together with various optical mismatching and beam aberrations which could reduce heterodyning efficiency. An additional problem, which also renders difficult the comparison between the results of different groups, is the lack of reproducible, well calibrated scattering targets. We have recently had available surfaces of cut polystyrene and flame sprayed aluminium for which the scattering characteristics have been well established. Accordingly we have conducted a detailed examination of all the parameters entering the evaluation of signal to noise ratio with a two-fold aim: firstly to determine whether a discrepancy did exist that could be explained by factors not presently taken account of in the theoretical treatment, and secondly to provide an absolute calibration of our CO2 laser heterodyne system so that the measured signal to noise ratios could be translated into absolute backscattering strengths.
Laboratory Target Reflectance Measurements for Coherent Laser Radar Applications
Authors: Wang J. Y.
Published: February 2023

The target/background signatures of an imaging coherent laser radar are random in nature due to target surface roughness. These signatures must be characterized for proper sensor performance prediction and design optimization. Instead of a coherent reflectometer, a direct-detection reflectometer was constructed for the following reasons. The coherent reflectometer introduces the uncertainty of mixing efficiency between the signal beam and the local oscillator beam; the mean reflectivity of speckle-resolved measurements from a diffuse target is the same as that of speckle-averaged measurements; and by varying the distance between the detector and the target, the signature statistics with different degrees of speckle averaging may be obtained.
Refractive Turbulence Effect on Truncated Gaussian Beam Heterodyne Lidar
Authors: Murty Rom
Published: February 2023

Monostatic heterodyne lidar using aerosols as backscattering target is considered in this work in the presence of atmospheric turbulence. The objective is to study the combined effects of varying truncation of Gaussian beam and turbulence strength on the performance of the lidar system.
Global Wind Measuring Satellite System (WINDSAT) Feasibility Studies
Authors: Huffaker R.M.
Published: February 2023

Since 1976, the Wave Propagation Laboratory of the National Oceanic and Atmospheric Administration’s (NOAA) Environmental Research Laboratories has investigated the feasibility of measuring the global wind field using a pulsed coherent laser radar, under a joint program with the U.S. Air Force Space Division Defense Meteorological Satellite Program (DMSP). Both the analytical and the hardware feasibilities of a space-borne global wind measuring system (WINDSAT) have been investigated. The vertical distributions of the horizontal wind field, throughout the troposphere with 300-km2 horizontal and 1-km vertical resolution, were required by both NOAA and DoD. Studies were conducted for a 300-km Space Shuttle orbit and an operational polar orbit of 800 km.1,2 A hardware definition study was completed for a Space Shuttle demonstration system.3 The conceptual design of an operational WINDSAT system, mounted on an advanced TIROS-N spacecraft, has recently been completed. The NOAA WINDSAT computer simulation was used to determine the instrument parameters needed as inputs to these studies.
Influence of coherent mesoscale structure on satellite-based Doppler lidar wind measurements
Authors: Emmitt G. D.
Published: February 2023

The potential impact of mesoscale patterns of winds, clouds and aerosols upon satellite based lidar estimates of the global winds are discussed with examples taken from a NASA simulation study.
WINDSAT Free Flyer Telescope Concept Using Ultralightweight Beryllium Technology*
Authors: McHugh T. , Hancock K.
Published: February 2023

A feasibility study has been performed to determine whether the WINDSAT telescope subsystem, originally designed as a shuttle-based experiment, might be lightweighted and adapted for a TIROS type operational platform. The greatest challenge is in retaining the diffraction limited performance despite the weight reduction, using the same optical design concept.
Feasibility Study on LDA Cross Wind Velocity Measurements Using Pulsed Visible Laser Light
Authors: Sommer E. , J.Pfeifer H.
Published: February 2023

In a feasibility study for LDA cross wind velocity measurements first experiments were performed over distances up to 90 m using a long pulse Nd:YAG-Laser.
On-Line Data System for the DFVLR-Laser-Doppler-Anemometer
Authors: Bachstein F. , Werner Ch. , Köpp F.
Published: February 2023

The DFVLR infrared Doppler lidar is a cw homodyne system designed for boundary layer wind measurements, especially for aircraft related wind phenomena like the low level jet, shear winds and wake vorticities. The system is similar in size and optical layout to Doppler lidars in other research groups (as for example Schwiesow et al.1981). It has features to make convenient wind determination. Three of these features are scanning, readout, and data reduction. The on-line data system is described in this part.
The RSRE/RAE Laser True Airspeed System (LATAS)
Authors: Cannel J , Foord R , Vaughan J M , Woodfield A
Published: February 2023

For airborne use laser velocimetry provides a unique ability to measure airspeed relative to regions a long way ahead of the aircraft. Such a Laser True Airspeed System (LATAS) has been designed and built by the Optics Division (01) at RSRE, Malvern in collaboration with Flight Research Division (FS1) at RAE Bedford. Flight trials have been conducted in the HS125 executive jet aircraft at RAE. The optics equipment has been designed to be compact, rugged and lightweight, operable remotely in a hands-off manner and sited in an unpressurized part of the aircraft. In the aircraft cabin the control equipment, signal processing and recording have been developed for research purposes to give flexibility in operation using microprocessor programming techniques.
Navy Laser Radar Overview
Authors: Hintz R. T.
Published: February 2023

The U.S. Navy is pursuing the use of CO2 laser radar technology for a variety of applications. Rather than attempt to describe the specifics of these applications and rapidly get into classification problems, three major areas which support the uses of the technology will be described. Critical areas include componentry, signatures, and airborne imaging sensors. Under the componentry area a manufacturing technology program for CO2 waveguide lasers will be described. For the signatures part of this discussion a Navy built and operated van installation (Navy Active Target Signatures (NATS) System) will be described. Finally some results from a flight test conducted on a UH-IN helicopter of an imaging sensor will be reviewed.
Variable Reflectivity Unstable Resonators for Coherent Laser Radar Emitters
Authors: Parent André , Lavigne Pierre
Published: February 2023

Positive branch unstable resonators with graded convex couplers are an attractive configuration to produce high-power single-mode lasers suited to ladar applications [1]. The purpose of this presentation is first, to determine the reflectivity profile which will optimize the energy extraction while maintaining single transverse mode oscillation and second, to demonstrate that graded mirrors can be used to make high-power coherent TE-CO2 emitters when single longitudinal mode operation is achieved by injection seeding [2].
Compact Single Mode One Joule CO2 Laser with a Gaussian Reflectivity Resonator
Authors: Harris M R , Willetts D V
Published: February 2023

Applications for pulsed CO2 lasers in coherent radar systems generally require that the transmitter laser operates single mode and with a high degree of frequency stability. In pulsed CO2 lasers discharge effects [1] and a laser induced effect [2] lead to frequency sweeping. For longer pulse operation in particular the laser induced effect is the major source of frequency sweeping. This mechanism shows an inverse 4th power dependence on beam spot size and can, therefore, be minimised by employing cavities which enable a large mode radius to be achieved whilst maintaining good discriminiation against higher order transverse modes. Such a geometry enables large mode volumes to be obtained from short resonators allowing high energy operation from compact structures. Furthermore, since the energy is dispersed over a large area of mirror surface good resistance to damage should ensue.
Performance studies of detectors for CO2 laser heterodyne systems
Authors: Wilson D.J. , Constant G.D.J. , Foord R. , Vaughan J.M.
Published: February 2023

The photon detector is an essential component for all CO2 laser radar systems, the most desirable characteristic for the heterodyne mode being high quantum efficiency. For high frequency use most detectors are photo-voltaic Cadmium-Mercury-Telluride operating at 77K, with a greater than 1GHz capability.
Power-Handling Capability of Cooled Optical Isolators for CO2-Laser Radars
Authors: Klein Claude A. , Dorschner Terry A.
Published: February 2023

Our objective is to assess contemplated optical isolator (Faraday rotator) designs from the point of view of handling incident power loads without generating unacceptable phase distortions. For this purpose, we assume that thermally induced phase aberrations can be described by means of a fourth-order even polynomial,* which implies that, after refocussing, the irradiance at the original Gaussian focus amounts to1 For small aberrations, it follows that the degradation in focal intensity is specified by the relation which suggests that, in effect, the isolator "fails" if the RMS spherical aberration exceeds the 2π/14 limit.2 The problem we are addressing thus boils down to determining the power level at which the amplitude-weighted variance of δϕ4r4 exceeds the 0.2 limit. In this context, we will first consider the procedure that may allow us to perform this task in a simple but consistent manner for both edge-and face-cooled design candidates. Subsequently, the procedure will be applied to two cases of current interest in designing state-of-the-art optical isolators for CO2-laser radars.3
Monte Carlo Simulations of Coherent DIAL Water Vapor Measurement Performance
Authors: Kavaya Michael J. , Russell Edward C.
Published: February 2023

Previous DIAL performance simulations have employed "expected value" analytic expressions which relate the normalized variance of the measured quantity (e.g, water vapor density) to several variances, covariances, and values of other measurement parameters, such as received power and number of shot-pairs [1-4]. The calculated variance (error) vs height actually represents the expected value or ensemble average error that would be obtained through numerous DIAL measurements of N shot—pairs each, on a microscopically frozen atmosphere, However, atmospheric parameters vary both temporally and spatially in complex ways. A Monte Carlo DIAL computer simulation was developed to allow observation of relative magnitudes and interrelationships of various instrument and atmospheric effects. These include speckle; refractive turbulence; field curvature mismatch; transmitter and receiver diameters; wind velocity and/or lidar motion; pulse repetition frequency (PRE); time delay between pulses of one pulse—pair; total measurement time; pulse—pair averaging; pulse temporal profile; fluctuations in atmospheric backscatter and absorption; fluctuations in the densities of atmospheric constituents; and range smoothing.
Doppler Signatures of Hard Targets
Authors: Wilson David J. , Dedmon R. Burt , Montgomery W. W. , Craven C. E.
Published: February 2023

Monostatic coherent doppler signal-to-noise (S/N) ratio measurements were made with a 15 watt, continuous wave, homodyne 10.6 micrometer ladar. The path from the ladar to the target was 30m horizontal with a single fold of the beam to maximize path length. The beam was focused at the target through the 25cm aperture Schwartzchild telescope. Attenuation at the folding mirror was used to reduce power on the target and attenuate the returned beam to prevent saturation of the detector preamplifier circuit.
Coherent Lidar Systems Development at MSFC
Authors: Bilbro James W.
Published: February 2023

The coherent lidar work at the Marshall Space Flight Center has recently been moved to new quarters which allow a more permanent setup while providing sufficient space for more flexibility. The laboratory facilities include an electronics shop, calibration laboratory, and the main lidar laboratory. A room is in the process being set up for laser systems characterization studies. The airborne pulsed system has been refurbished to repair the failure of the modulator crystal during the 1984 flight tests and set up in the main laboratory. The telescope which had expericed considrable degradation after some four years of being shipped back and forth across the country was stripped, recoated and the alignment checked. A new completely programmable scan control system has been completed and the hemispherical scanner has been mounted to the roof of the laboratory. An extensive set of software is being developed for the collection, processing and display of the ground based data. The data collection and raw data display software have been completed and checked out. Real time and post processing capability for such features as automatic absorption and backscatter profiling, and VAD wind profiling are underway. The capability for single shot data collection and processing are also being provided. A number of experiments are being planned for the August/September time frame when the system comes on line. These experiments involve primarily investigations into atmospheric effects on signal processing and boundary layer measurements. The pulse energy (10 mJ) is too low to perform such long range measurements as backscatter profiling in the upper troposphere. An experiment is being designed to assess the feasibility of demonstrating of lag angle effects.
The Laser Atmospheric Wind Sounder (LAWS)
Authors: Curran R. , Bilbro J. , Fitzjarrald D.
Published: February 2023

Summary not available.
Assessment of error sources for one component wind measurements with a space-based Doppler lidar
Authors: Emmitt G. D. , Bilbro J. W.
Published: February 2023

A space-based CO2 Doppler lidar is being considered by NASA, NOAA, DOD, and European groups to obtain direct measurements of the winds in the cloud free regions of the troposphere by measuring the Doppler shift in the backscattered energy from aerosols in motion. Workshops and panel meetings have addressed the needs of the user community and the desired measurement accuracies (NASA, 1985). Early feasibility studies by NOAA and NASA presented a generally optimistic outlook for obtaining useful wind measurements (Huffaker, et al., 1980). Current efforts are now in progress to assess the accuracies in more detail and to evaluate the impact that such global measurements will have on predictive atmospheric models (Emmitt, 1987).
Doppler Lidar Analysis and Display Techniques
Authors: Richter Ronald A.
Published: February 2023

Analysis and display techniques have proven to be a central component in the development of the NOAA Doppler lidar. A short history of our efforts in this area follows along with a description of the types of displays the NOAA Doppler lidar uses to support atmospheric science applications and research. A more complete history of Doppler lidar development at NOAA has been described by Hall, et. al.1
Self-Tuning Post Detector Processing of Doppler Lidar Returns
Authors: Rye B.J. , Hardesty R.M.
Published: February 2023

Identification of a signal model is a prerequisite for estimation of a signal. It is often the case for atmospheric lidar returns that the model is unknown and difficult to establish due to contamination by speckle or measurement noise. The goal is then a self-consistent estimation using what is possibly a suboptimal model, but one for which the structure and parameters are justified only by the data and a minimum of a priori assumptions.
Signal processing for the DFVLR cw CO2 laser Doppler anemometer
Authors: Hausamann D. , Köpp F. , Werner Ch.
Published: February 2023

Wind velocity measurements by laser Doppler anemometry have proved to be a very efficient method (1) for standard wind field investigations as well as for applications where standard methods are not applicable (2).
Hard Target Calibration of Coherent Lidar Backscatter Data: Polarization Effects
Authors: Kavaya Michael J.
Published: February 2023

The wavelength, height, and geographical dependences, and the statistical description of the atmospheric aerosol backscatter coefficient continues to be an important, but largely unknown, area of research. Improved knowledge and understanding of aerosol characteristics is important in atmospheric science and in assessing the performance of various lidar remote sensing concepts such as DIAL measurements of atmospheric species and pollutants, and coherent Doppler lidar measurements of wind velocity and turbulence. Remote sensing using lidar systems is ideally suited to measure the backscatter data; from the ground, airplanes, ships, or space. However, calibration of the lidar aerosol backscatter data has only recently progressed to the point where errors under 50% may be achieved [1-5].
Calibration of the Reflectance of Hard Targets for a Coherent Doppler Lidar
Authors: Anderson Richard , Bilbro James
Published: February 2023

During the summer of 1986 some preliminary experiments were performed to measure the reflectivity of hard targets used to calibrate a coherent Doppler lidar. The experiments were performed in an integrating sphere with the sample uniformly and normally irradiated. In this way both bihemispherical and directional-hemispherical reflectance were measured. The irradiated targets in the case of bihemispherical reflectance were the standard diffuse gold sample, flowers of sulfur, glass bead blasted aluminum, and 120 grade aluminum oxide sandpaper. In the case of normal directional-hemispherical measurements the samples were the diffuse gold standard, glass bead blasted aluminum, and the 120 grade sandpaper. In the bihemispherical measurements the integrating sphere wall was irradiated so the sample could be uniformly irradiated.
Development of a Tropospheric Aerosol Climatology Using Satellite Occulltation Data
Authors: Kent Geoffrey
Published: February 2023

Summary not available.
Simulation of the atmospheric cycle of desert dust particles using a general circulation model
Authors: Joussaume S. , Sadourny R.
Published: February 2023

Aerosol particles are interesting from many viewpoints - e.g. pollutant impact on ecosystems, climatic impact on the hydrologic cycle and through radiative properties - and can also be a tool for satellite measurements. Atmospheric general circulation models having proved their capability to reproduce the main features of climate, can be appropriate tools to study the atmospheric cycles of aerosol particles. Such simulations cannot be done without a severe comparison with observations, but afterwards they can give an extensive 3-dimensional vision of the tracer cycles and be used for sensitivity or forecasting studies.
A Comparison of Measured and Calculated Backscatter Properties of Atmospheric Aerosols at IR Wavelengths
Authors: Rosen J. M.
Published: February 2023

The research described here was motivated by a desire to develop a verifiable method for calculating the IR backscatter from measurements of typical atmospheric aerosols size distributions. The aerosol data base and general procedure employed is similar to that of a previous study which focused on optical properties in the visible region of the spectrum (Rosen and Hofmann, 1986). In that effort direct measurements of the extinction, backscatter and mass were compared to values calculated from the measured size distribution. The atmospheric particles under consideration were restricted to the stratospheric aerosol layer because they are spherical and of known composition, thus lending themselves to quantitative calculations. Results obtained in this earlier work indicate that measured size distributions could, in fact, be used with confidence to calculate physical and optical properties (in the visible) of the aerosol. In what follows is an attempt to extend this same study into the IR using available backscatter measurements at 10.6 μm. Again the majority of the effort will focus on the stratospheric aerosol layer, not because it is of inherent interest, but because it represents an ideal test target and aerosol system for quantitative calculations.
Australian Free Tropospheric Aerosol Measurements
Authors: Gras John L.
Published: February 2023

Airborne measurements of the spatial and temporal distributions of aerosol particle microphysical properties have been made recently in the Australian region (from the surface to about 6 km altitude). The most recent of these measurement series (a joint CSIRO/NASA field program) along the Australian east coast and across New Guinea, also included simultaneous measurement of particle backscatter at 10 microns and visible wavelength backscatter using ground-based lidar (at two sites). These data are of particular relevance for feasibility studies of satellite IR laser wind determination systems.
Measurements of Aerosol Backscatter at CO2 Wavelengths with the Airborne Laser True Airspeed System (LATAS)
Authors: Vaughan J. Michael , Brown Derek W. , Rothermel Jeffry , Bowdle David A.
Published: February 2023

Since 1981, the Royal Signals and Radar Establishment (RSRE) and the Royal Aircraft Establishment (RAE), United Kingdom, have been making detailed measurements of aerosol backscatter coefficients using an airborne, 10.6 micrometer, continuous-wave (CW) focused CO2 Doppler lidar, the Laser True Airspeed System (LATAS) (Foord et al, 1983). The LATAS measures both the backscatter cross-section and the line-of-sight velocity (with respect to the LATAS) of micrometer-sized atmospheric aerosol particles. During this extended period of field trials, the LATAS has proven to be quite rugged and reliable, with a minimal amount of maintenance and with minimal loss of sensitivity.
Summary of CSIRO/NASA Backscatter Measurements
Authors: Jones William D. , Huffaker Robert M.
Published: February 2023

From mid-May to mid-June, 1986, NASA’s Marshall Space Flight Center (MSFC), Huntsville, AL and the Commonwealth Scientific and Industrial Research Organization (CSIRO), Division of Atmospheric Research, Aspendale, Victoria, Australia conducted a cooperative airborne atmospheric measurement program to determine aerosol size, concentration, and chemical composition, and to determine the atmospheric backscatter coefficient (β(π)) at CO2 laser wavelengths (10.6 μm).
LDV Comparative Wind Measurements in Clouds
Authors: Dickson David H.
Published: February 2023

Laser Doppler Velocimeter wind measurements are compared to the Boulder Atmospheric Observatory 300 meter tower. The beam filling influence of low clouds and fog is presented. Data for both clear and cloudy conditions is presented.
Fluctuation and Change in Measured Backscatter from Atmospheric Aerosols
Authors: Vaughan J M , Brown D W , Callan R D , Davies P H , Foord R , Nash C , Perry J W H , Wilson D J , Alejandro S B , Bedo D , Koenig G
Published: February 2023

Signal fluctuations from coherent lidar systems have been considered both theoretically and experimentally by many authors in different wavelength regimes. At 10.6µm Hardesty et al [1] considered characteristics of coherent lidar returns from calibration targets and aerosols; Flamant et al [2] used a pulsed CO2 lidar to study speckle effects from various rough surfaces and Letalick et al [3] measured signal amplitude distributions for a FM-cw CO2 laser radar. In other studies Vaughan et al [4] employed correlation analysis to study signal fluctuations from a moving belt.
The GLObal Backscatter Experiment (GLOBE) Pacific Survey Mission
Authors: Bowdle David A. , Rothermel Jeffry , Williams Steven F. , Arnold James E.
Published: February 2023

The National Aeronautics and Space Administration (NASA) conducted the GLObal Backscatter Experiment (GLOBE) survey missions on a NASA DC-8 aircraft over the central and near-coastal Pacific Ocean during November 6 - 30, 1989 (GLOBE I) and May 13 - June 5, 1990 (GLOBE II). These missions were designed to study the optical, physical, and chemical properties of atmospheric aerosols. Particular emphasis was given to the magnitude and spatial variability of aerosol backscatter coefficients (β, m−1sr−1) at mid-infrared (9-11 µm) and mid-visible to near-infrared (0.5-1.5 µm) wavelengths. Both missions concentrated on the remote middle and upper troposphere, where these aerosol properties are poorly understood.
The Infrared Doppler Lidar: An important tool for experimental investigation of aircraft wake vortices
Authors: Koepp Friedrich
Published: February 2023

Aircraft wake vortices are a severe air-traffic problem. Especially during landing and take-off, the strong vortices of heavy aircraft present a potential hazard to other aircraft following closely behind. Vortex imposed separation standards have been established. But they will prove to be a strong restriction on future capacity demands at major airports.
Lidar Windshear Detection For Commercial Aircraft
Authors: Targ Russell , Forney Paul
Published: February 2023

Low-altitude windshear is recognized by the commercial aviation industry as a major hazard. In the United States, during the period 1964 to 1985, windshear was a contributing factor in at least 26 civil transport incidents and 3 accidents, involving 500 fatalities and 200 injuries. On a single day, in July 1988, windshear caught four jetliners at Denver/Stapleton Airport and dropped one of them within 100 feet of the ground. The FAA has now mandated that all commercial aircraft have some kind of windshear warning devices onboard by 1994, or a predictive, forward-looking device by 1996.
Performance Characteristics of a TE CO2 Laser with a Long Excitation Pulse
Authors: Harris M R , Willetts D V
Published: February 2023

Coherent laser radar applications often require longer optical pulselengths than can be delivered by conventional TE CO2 lasers. E-beam sustenance offers a satisfactory but complex solution, or optical output can be extended by using very nitrogen rich mixtures at the penalty of low efficiency (1).
Performance of a Sealed-Off CO2-Isotope Laser Amplifier for High Resolution Optical Radar/Lidar Applications
Authors: Freed C. , Eng R. S. , Green J. S. , Marcus S. , Theriault J. R. , O'Donnell R. G. , Pape W. , Parshall E. R.
Published: February 2023

This paper will describe the characteristics and evaluation of a CO2-isotope laser MOPA system that has been in operation at MIT Lincoln Laboratory for well over a year. The CO2 MOPA system consists of an ultrastable sealed-off cw CO2-isotope laser oscillator whose output is chopped to produce a pulse train, which in turn is amplified by a two-stage pulsed CO2-isotope laser amplifier with a net power gain of over 30dB.
Enhanced Lidar Sensitivity by Optical Amplification
Authors: Harris M , Loudon R , Shepherd T J , Vaughan J M
Published: February 2023

Several authors have considered the use of an optical amplifier to increase the strength of a signal in order to improve detection sensitivity1. Whether or not amplification achieves an improvement in practise depends upon a number of factors: properties of both amplifier and detection system must be taken into account.
Pulse-Repetiton Solid-State Laser Coherent Lidar with Nonlinear Optical Converters: Suggestions and Testing of Optical Scheme
Authors: Kulagin O. , Matveyev A. , Pasmanik G. , Shilov A.
Published: February 2023

We consider a traditional measurement scheme involving illimination of the given atmosphere region and detection of the radiation scattered within this region.
Discharge Characteristics of the LP-140 Pulsed CO2 Laser
Authors: Spiers Gary D.
Published: February 2023

The LP-140 is a low pressure pulsed transversely excited CO2 laser Manufactured by PSI(1). The laser has a folded cavity construction and each am of the cavity contains four discharge sections. The eight cathodes are placed on the outer edges of the cavity arms so that they can share a single large wire grid anode. Eight additional electrodes each consisting of a potted array of resistively ballasted pins are located behind the grid anode directly opposite each of the cathodes. The sympathetic discharge used in the LP-140 relies on a preliminary discharge between the anode and these pin electrodes to preionise the main discharge volume. Each electrode pair has a discharge volume of 280 cm3. The discharge circuit is arranged such that each electrode pair has its own energy storage capacitors and pfn (fig. 1.) but all share a common thyratron and HV supply. The capacitors are charged to 9 kV. The de HV supply consists principally of a large HV step-up transformer with no regulation or adjustment of the output voltage possible without modification.
An Automatically Aligned Lidar System
Authors: Harris M , Loudon R , Perry J W H , Shepherd T J , Vaughan J M
Published: February 2023

Optimum alignment of a coherent lidar is notoriously difficult to achieve1, particularly in compact systems designed for field operation. The correct spatial overlap and wavefront matching of signal and local oscillator beams can be especially time-consuming in systems at non-visible wavelengths (eg CO2). Several authors have suggested re-injection of the signal into the laser oscillator to achieve automatic alignment2-4.
RF Excited Waveguide CO2 Laser with Low Thermal Drift
Authors: Callenås Anders , Renhom Ingmar
Published: February 2023

Power stability is a fundamental requirement in most laser applications. Especially in relatively high powered lasers for material processing is the thermal stability of the cavity design of great importance. In the lower power region we find waveguide lasers intended for applications ranging from marking, scribing, cutting etc. to coherent radar and spectroscopy. The single frequency lasers, which are needed in coherent systems, are often dither stabilized and/or referenced to an external reference. The cavity design and its thermal characteristics have an important effect on the practical aspects of frequency stabilisation. Although a high degree of stability can be achieved without taking too much care of the thermal drift by using an elaborate feedback system1, 2, 3, 4, the demand on the feedback system can be substantially lowered by using a thermal compensated cavity design.
Performance studies on a HgCdTe detector for heterodyne systems
Authors: Letalick Dietmar , Renhom Ingmar
Published: February 2023

In all laser radar systems the detector is an essential part that can influence the performance of the system to a great extent. It is therefore necessary to study the detector characteristics in order to determine the effect of the detector on the overall performance of the laser radar system.
The Study of Streghthening Signal-to-Noise Ratio on CO2 Coherent Laser Radar
Authors: Yongjiang Dai , Haibin Wu , Xuedong Yang
Published: February 2023

The signal-to-noise ratio of system is a impotant parameter for the CO2 coherent laser radar. In order to improve the signal-to-noise ratio of system the matched filter, interlock processor and frame-average are extensive applied(1). The methods of improving signal-to-noise ratio of the system by computer are digital-filter, accumulated average, interlock operation and so on(2),(3). At first, the backwave signal from target has been analysed, then the coast average method has been used in signal processing. We have developed a computer system for improved signal to noies ratio and it has been increased by 60db.