bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive convolution kernel network for change detection in hyperspectral images
Authors: Liu Song , Li Haiwei , Chen Junyu , Li Siyuan , Song Liyao , Zhang Geng , Hu Bingliang
Published: February 2023

Feature extraction is a key step in hyperspectral image change detection. However, many targets with great various sizes, such as narrow paths, wide rivers, and large tracts of cultivated land, can appear in a satellite remote sensing image at the same time, which will increase the difficulty of feature extraction. In addition, the phenomenon that the number of changed pixels is much less than unchanged pixels will lead to class imbalance and affect the accuracy of change detection. To address the above issues, based on the U-Net model, we propose an adaptive convolution kernel structure to replace the original convolution operations and design a weight loss function in the training stage. The adaptive convolution kernel contains two various kernel sizes and can automatically generate their corresponding weight feature map during training. Each output pixel obtains the corresponding convolution kernel combination according to the weight. This structure of automatically selecting the size of the convolution kernel can effectively adapt to different sizes of targets and extract multi-scale spatial features. The modified cross-entropy loss function solves the problem of class imbalance by increasing the weight of changed pixels. Study results on four datasets indicate that the proposed method performs better than most existing methods.
Effect of the annealing temperature on structural, morphological, and nonlinear optical properties of TeO2 thin films used for efficient THz generation
Authors: Mahendar M. , Krishna R. N. Vamsi , Chaudhary A. K.
Published: February 2023

This paper reports the effect of annealing on TeO2 films deposited using the thermal evaporation technique. TeO2 films of 120 nm thickness were grown on a glass substrate at room temperature (RT) and annealed at 400°C and 450°C. The structure of the film and the influence of the annealing temperature on the crystalline phase change were examined using the X-ray diffraction method. Optical properties such as transmittance, absorbance, complex refractive index, and energy bandgap were determined between ultraviolet-visible to terahertz (THz) range. These films have a direct allowed transition with the optical energy bandgap of 3.66, 3.64, and 3.54 eV at as-deposited temperatures (RTs) of 400°C and 450°C. The effect of the annealing temperature on the morphology and surface roughness of the films was investigated using atomic force microscopy. The nonlinear optical parameters, which are the refractive index and absorption coefficients, were calculated using THz time domain spectroscopy. The microstructure variation of the TeO2 films in terms of surface orientation plays an important role in understanding the change in the nonlinear optical properties of the films. Finally, these films were subjected to 800 nm wavelength of 50 fs pulse duration obtained from a Ti:sapphire amplifier at a 1 kHz repetition rate for efficient THz generation. The power of incidence of the laser beam was tuned at a range between 75 and 105 mW; the highest power of the generated THz signal was of the order of 210 nW for 450°C annealed film with respect to the incident power of 105 mW. The conversion efficiency was found to be ∼0.22×10−5%, which is 2.025 times more than the film annealed at 400°C.
Highly efficient and tunable polarization rotator based on lithium niobate on an insulator
Authors: He Xiangyu , Xu Yin , Zhang Bo , Dong Yue , Ni Yi
Published: February 2023

The lithium niobate on an insulator (LNOI) platform has greatly advanced the development of integrated photonics recently, where efficient polarization management components are indispensable. In this work, we propose a highly efficient and tunable polarization rotator based on the LNOI platform and the low-loss optical phase change material antimony triselenide (Sb2Se3). The key polarization rotation region is formed by a LNOI waveguide with a cross section of the double trapezoidal shape and a Sb2Se3 layer deposited atop the LNOI waveguide in an asymmetrical way, where an isolating layer of silicon dioxide is sandwiched between them to reduce the material absorption loss. Based on such a structure, we have achieved the efficient polarization rotation in a length of only 17.7 µm, where the polarization conversion efficiency and insertion loss are 99.6% (99.2%) and 0.38 dB (0.4 dB) for the trans-electric (TE)-to-trans-magnetic (TM) rotation. If we further change the phase state of the Sb2Se3 layer, other polarization rotation angles besides 90° can also be obtained for the same device, revealing a tunable function. We believe that the proposed device and design scheme could offer an efficient method for realizing the polarization management on the LNOI platform.
Implementation of miniaturized modular-array fluorescence microscopy for long-term live-cell imaging
Authors: Chen Qingyu , Son Jeonghwan , Jia Shu
Published: February 2023

Fluorescence microscopy imaging of live cells has provided consistent monitoring of dynamic cellular activities and interactions. However, because current live-cell imaging systems are limited in their adaptability, portable cell imaging systems have been adapted by a variety of strategies, including miniaturized fluorescence microscopy. Here, we provide a protocol for the construction and operational process of miniaturized modular-array fluorescence microscopy (MAM). The MAM system is built in a portable size (15cm×15cm×3cm) and provides in situ cell imaging inside an incubator with a subcellular lateral resolution (∼3µm). We demonstrated the improved stability of the MAM system with fluorescent targets and live HeLa cells, enabling long-term imaging for 12 h without the need for external support or post-processing. We believe the protocol could guide scientists to construct a compact portable fluorescence imaging system and perform time-lapse in situ single-cell imaging and analysis.
Evolution of adaptive optics retinal imaging [Invited]
Authors: Williams David R. , Burns Stephen A. , Miller Donald T. , Roorda Austin
Published: February 2023

This review describes the progress that has been achieved since
adaptive optics (AO) was incorporated into the ophthalmoscope a
quarter of a century ago, transforming our ability to image the retina
at a cellular spatial scale inside the living eye. The review starts
with a comprehensive tabulation of AO papers in the field and then
describes the technological advances that have occurred, notably
through combining AO with other imaging modalities including confocal,
fluorescence, phase contrast, and optical coherence tomography. These
advances have made possible many scientific discoveries from the first
maps of the topography of the trichromatic cone mosaic to exquisitely
sensitive measures of optical and structural changes in photoreceptors
in response to light. The future evolution of this technology is
poised to offer an increasing array of tools to measure and monitor in
vivo retinal structure and function with improved resolution and
control.
Data Requirements for an Operational Weather Prediction System in the 1990's
Authors: Hovermale John B.
Published: February 2023

In order to meet societal needs for improved weather forecasts, old and new technology must be blended to provide a more detailed and spatially broader view of the atmosphere. Advancing technology, and its associated needs for efficiency, have increased demands for weather information at both short ranges (1-2 days) and extended ranges (1 week-1 month). Over the past two decades the introduction of improved mathematical techniques and electronic technology have allowed a more precise application of the laws of physics to the atmosphere, leading to significant increases in prediction accuracy. There is ample evidence that further advances in predictive ability can be achieved if inherent approximations remaining in the numerical weather prediction (NWP) system are made with more precision.
Navy Goals for Satellite Measurements and Environmental Parameters
Authors: Noble Vincent E.
Published: February 2023

Navy goals for satellite measurements of environmental parameters are often different for operation and research activities depending on the specific application area. Navy needs and goals for atmospheric terrestrial and oceanic parameters are described, and the difference between needs/goals and requirements is defined.
Laser Doppler Velocimetry by Backscatter Modulation of the Source
Authors: Churnside J. H.
Published: February 2023

It is well known that small quantities of stray light reflected back into a laser cavity can produce large perturbations in the laser characteristics. To the best of our knowledge, however, no one has recognized that this effect can be used as a sensitive detection process for making Doppler velocity measurements. This technique has the added featurs that the critical beamsplitter alignment requirements of conventional laser Doppler velocimetry have been eliminated by eliminating the beamsplitter. We report here a demonstration using a CO2 laser and a rotating disk target.
Miniaturized Laser Doppler Velocimeter (LDV)
Authors: Dickson David
Published: February 2023

A miniaturized 5 watt CO2 LDV will be demonstrated. This LDV is used as a diagnostic remote wind and turbulence sensor to probe the first few meters of the atmosphere.
Coherent DIAL at CO2 Laser Waveguide
Authors: Thomas Eric L.
Published: February 2023

Experimental difficulties inherent in both the DIAL and coherent detection techniques will be highlighted. Possible solutions for some of these problems will be discussed.
Airborne Remote Sensing of Earth Surface Signatures with the DIALEX Instrument
Authors: Wiesemann W. , Rother M. , Englisch W. , Lehmann F. , Werner Ch.
Published: February 2023

The Airborne DIALEX instrument /1/ is an active single-ended dual-wavelength sensor. At present it is equipped with two line-tunable cw CO2 lasers and employs heterodyne detection. The return signal is provided by scattering and reflection at the earth's surface. The processed signal takes the form Filtering the differential albedo effect provides a new exciting possibility for active remote sensing of earth surface spectral signatures. Instruments of the DIALEX-type are well suited for this purpose because the coherent detection scheme provides the required sensitivity even at high flight altitudes.
Analytical Comparison of Optimized Heterodyne and Direct-Detection CO2 Lidar for Atmospheric Remote Sensing*
Authors: Killinger D. K. , Menyuk N.
Published: February 2023

Our recent experimental study1 of the relative technical merits of heterodyne and direct-detection CO2 DIAL for path-averaged remote sensing was carried out using LIDAR backscattered returns from topographic targets. In these studies, the average SNR's and statistical and temporal characteristics of the LIDAR returns were measured simultaneously for each detection technique. The experimental results were found to be in good agreement with a simple analysis which predicted the relative sensitivity of each detection technique for path-averaged measurements. The detection systems used in the above experiments were not optimized for either of the two detection techniques.
Measurement of Atmospheric Temperature
Authors: Lading L. , Jensen A. Skov , Rasmussen E.
Published: February 2023

The spectrum of Rayleigh scattered light contains information about the temperature. Measuring principles are discussed. A system is analyzed. It has the potential for measuring the temperature at ranges up to 10 km in a few minutes. Problems in the implementation are discussed. Tentative measurements are presented.
GCM Simulation Studies on the Relative Importance of Wind Observing Systems for Numerical Weather Prediction
Authors: Halem M.
Published: February 2023

Two series of simulation experiments were conducted with the GLAS Fourth Order GCM to assess the information content of different observing systems capabilities to infer atmospheric states. In the first set of experiments, the "natural atmosphere" from which simulated observations were derived is a long integration of the model. In the second set of experiments, simulated observations were extracted from the NMC operational analysis for the FGGE Special Observing Period - 1. In both cases, the observations consisted of complete 3-dimensional fields of either winds, temperatures or surface pressure. These observations were then used to run a 12 hour analysis/forecast cycle and the ability of the observations to infer the other unobserved fields was determined from the (asymptotic) 12 hour forecast errors.
Polarization Properties of Coherent CO2 Lidar Scattering: Target Calibration and Cloud Characteristics
Authors: Gross Abraham , Post M. J. , Hardesty R. M. , Hall F. F.
Published: February 2023

Coherent lidars incorporate inherently a polarization-sensitive detection. Only the component of the backscattered radiation that is polarized parallel to the local oscillator laser field is detected. Moreover, monostatic laser Doppler velocimeters may utilize a Brewster-plate transmit-receive (TR) switch and the receiver detects the right circular polarization of a wave reflected from a left circular polarization transmitted beam. Thus the basic target characterization goes beyond the scalar target reflectivity. It is important to know, in principle, the full reflectivity matrix that includes polarization dependence of the reflection process.
Feasibility of a Windsat Free Flyer Using an Advanced TIROS-N Satellite
Authors: Altman W. P. , Gurk H. M. , Kaskiewicz P. F.
Published: February 2023

The feasibility of developing a Doppler lidar for flight on the Shuttle to measure tropospheric winds has been examined by others1. Such a development would ultimately lead to an operational system for measuring the global distribution of horizontal wind fields, which would improve meteorological forecasting. In the referenced study a design concept was developed for a lidar instrument which would require more than 2 kW and weigh 830 kg. In a subsequent study2, the feasibility of implementing this lidar instrument, with few changes of operating parameters, on board a free flying satellite was examined. The latter assessment indicated that the spacecraft technology is available for the deployment of such a system, although hardware development, would be needed. The total mass and power requirements of this system (including those of the spacecraft bus) were estimated to be 2260 kg and 3500 W. In fact, this system would require a new generation of satellites, since these requirements (in particular the power requirements) exceed the capabilities of present day operational low altitude meteorological satellites.
Definition Study of the WINDSAT Laser Subsystem
Authors: Byron S.R. , Moody S.E. , Znotins T.A.
Published: February 2023

Under the direction of NOAA, a recent study of the feasibility of a global wind measuring satellite system (WINDSAT) has been performed. The results of this study have defined a proposed system concept and hardware requirements of the WINDSAT TIROS-N operational platform. This paper describes the definition study of the laser subsystem undertaken by MSNW in support of the above effort. The laser subsystem requirements as determined by the present mission plan are summarized in Table 1. The design of such a system is guided by several constraints which relate to the space based nature of the device. The most notable are the power consumption requirements, and the subsystem weight and volume specifications. The system design is based on existing CO2 laser technology though some specific areas do require further development.
Requirements for Tunable Mode and Line Selection by Injection in a TEA-CO2 Laser
Authors: Menzies R. T. , Flamant P. H. , Kavaya M. J.
Published: February 2023

Mode selection in a TEA-CO2 laser cavity through the use of injection techniques provides high peak power single-longitudinal-mode (SLM) pulses with relatively low intensities of injected radiation. Provided the selected mode is near the center of the pressure-broadened TEA-CO2 gain transition, and the frequency proximity requirements are met, as little as 10 μW of injected power is sufficient to effectively produce a single-frequency pulse with peak power of several MW [1]. However, if tunable pulses are desired, the requirements for mode selection as the frequency of the injected radiation is tuned away from the CO2 transition center frequency become more demanding. An analytical treatment of the coupled rate equation for the molecular population densities and for the photon densities yields an expression for the "mode selection time", or the time during which the photon flux in the favored mode is a large fraction (e.g., >90%) of the total photon flux [2]. This expression is valid for values of molecular resonance detuning smaller than the pressure-broadened halfwidth (ΔνL) of the transition.
Chirp Analysis for Pulsed CO2 Laser Oscillators
Authors: Byron S.R. , Cassady P.E. , Znotins T.A. , Quimby D.C. , Moody S.E.
Published: February 2023

For many applications that utilize single frequency output of pulsed CO2 lasers, the shift in frequency during the pulse must be minimized. For example, in CO2 coherent Doppler lidar backscatter measurements of atmospheric wind speeds, the intrapulse chirp must be less than 200 kHz in order to achieve a wind speed resolution of 1 m/sec.1 Experimental studies in CO2 hybrid TEA lasers show a characteristic U-shape curve of frequency versus time, first falling during the early part of the pulse and then rising throughout the remainder of the pulse. Measured values of chirp range from 0.5 to 5 MHz for 3 μsec duration pulses. Analysis and experiments by Willetts and Harris2 have shown that the early chirp is due to decay of the plasma electron density in the laser gas and the late chirp is due to the gas density decrease near the optical axis of the cavity caused by nonuniform gas heating induced by the radial intensity profile of the laser mode structure.
Airborne Doppler Lidar Wind Systems and Inertial Motion References
Authors: Telford James W.
Published: February 2023

The availability of inertial navigation systems has made it possible to measure the vector velocity of earth relative to the aircraft, in aircraft coordinates. Thus, if the velocity of the air can be measured relative to the aircraft, the velocity of the air relative to the ground can be derived.
An Experimental Investigation of Ranging and Tracking with a Coherent Laser Radar
Authors: Cruickshank J. M. , Bonnier D. , Pace P. , Henshall H.
Published: February 2023

CO2 laser radar systems with either direct or heterodyne detection are being used for both atmospheric lidar measurements and ranging on 'hard' targets. A TEA-CO2 laser radar has been developed at DREV to evaluate, with field measurements, the possible role of 10.6-μm pulsed coherent laser radars for the ranging and angle tracking of airborne targets. To determine the signal-tonoise ratio required by a laser radar to detect a target with a desired probability of detection and a given false alarm rate, it is first necessary to characterize the signal returns from the targets of interest. This paper will present part of a recent investigation on the characteristics of the returns from standard reference targets obtained with heterodyne detection. A comparison will be made with similar measurements carried out with direct detection.
Progress towards pulsed CO2 lasers for use in space systems
Authors: Willetts D V
Published: February 2023

This review sets out to examine the technologies available to engineers designing space-based coherent CO2 laser radars of the kind which might be used for global atmospheric sounding. The purpose is not to generate a specific design but to consider the principles which must be adhered to to achieve success. We assume the following operating parameters [1].
Advances in 10.6 μm HgCdTe Detectors for Heterodyne Applications
Authors: Reine M.B.
Published: February 2023

This paper reviews recent progress in HgCdTe photodiodes operating at 77 K for near-quantum-limited heterodyne detection of CO2 laser radiation at bandwidths of up to 2.5 GHz.
Multisection Broadband Modulator
Authors: Lax B. , Marino R. M. , Eng R. S.
Published: February 2023

The single sideband (SSB) modulator described by Carter and Haus1 has limitations over a broadband frequencies. To maximize the output of their device with CdTe in a square waveguide, the beat frequency of the laser and the sideband are phase matched with the microwaves. The dimension of the guide a is determined by satisfying the equation where β1,2 are the propagation constants of the sideband and the laser beams respectively in CdTe at 10.6 μm, ϵ =7.2, ϵ
μ
=10.4. Equation(1) is satisfied for a =5.2 mm and f
μ
=16 GHz. When the microwave frequency deviates from this value , then the output is reduced according to the solution of the coupled-mode equations.1
Diode Laser Array Pumped Nd:YAG and Nd:Glass Slab Oscillators
Authors: Reed M. K. , Kozlovsky W. J. , Byer R. L. , Hamagel G. L. , Cross Peter S.
Published: February 2023

Rapid progress in the development of high power diode lasers and diode laser arrays has led to renewed interest in diode laser pumping of solid state lasers for remote sensing applications[1]. Recent work has shown that diode lasers offer many advantages in the pumping of neodymium doped crystals[2], Nd:Glass[3] and other ions in crystalline hosts[4,5]. Most of the early research has concentrated on end-pumped devices which take advantage of the high brightness of the diode laser to achieve low thresholds and high slope efficiencies. Although these devices are compact and effcient, they do not scale well to larger sizes and higher pump power levels provided by diode laser arrays. To investigate the performance and the potential scaling to higher peak and average powers, we have used a two dimensional array developed by Spectra Diode Labs to pump miniature slabs of Nd:YAG and Nd:Glass. Peak and average power levels of 70kW and 0.59W have been achieved.
A Conceptual Test of Frequency Diversity Lidar
Authors: Schotland R. M. , Cvijin P. Vujkovic , Zhao Yanzeng , Hudor A. M.
Published: February 2023

Atmospheric remote sensing by lidar frequently requires an accurate measurement of the mean intensity of the laser backscattered radiation. In the case of infrared coherent lidars, the return signal is characterized by rapid and deep fluctuations resulting from the interference of the fields backscattered to the lidar from moving, randomly located aerosol particles. The contrast ratio corresponding to the ratio of the standard deviation of the fluctuations of this signal to its mean value is unity if the mean signal is large compared to the signal shot noise.
The CNES-CNRS Ground-Based Infrared CO2 Lidar System
Authors: Flamant P.H. , Loth C. , Bouteyre A.
Published: February 2023

A ground-based coherent CO2 lidar system is under construction at LMD / CNRS-Ecole Polytechnique. The project is supported by CNES (the french space agency) for future spaceborne applications. The main goals of the mid-term program are twofold : 1) to develop and assess the technology for coherent lidar applications; 2) to conduct scientific studies such as backscatter and Doppler wind field measurements among others. The pulsed CO2 lidar is designed to acheive flexibility to be easily modified.
The Impact of Global Wind Measurements on the Global Circulation Model
Authors: Sparkman Jim
Published: February 2023

Summary not available.
Characteristics of Space Based Coherent UV Excimer Laser Radars
Authors: Grossman Jonathan Gary , Butman Jerry
Published: February 2023

Considerable interest in coherent UV laser radars has recently been generated with the advent of high power UV excimer lasers. This interest is due to the large Doppler shifts in the UV and the narrow beam divergences possible with UV lasers.
Perspectives in Coherent Doppler Lidar Signal Processing
Authors: Lee Robert
Published: February 2023

Remote sensing as a field of labor has a number of attractions. In addition to the fun of playing with high-technology gadgets and solving system problems there is the added satisfaction of measuring some parameter Nature has been trying to hide from us. Nevertheless it is occasionally necessary to step back from the immediate, usually narrowly confined problem and place the work in the context of the broad goals of the program we claim to support.
A Technique for Correcting Effects of Long CO2 Laser Pulses in Aerosol-Backscattered Coherent Lidar Returns
Authors: Zhao Yanzeng , Hardesty R. M.
Published: February 2023

A deconvolution technique for correcting effects of long CO2 laser pulses in aerosol-backscattered coherent lidar returns is developed and applied to backscattering coeffcient and H2O retrieval.
The JPL Lidar Target Calibration Facility
Authors: Menzies Robert T.
Published: February 2023

The objective of the JPL Lidar Target Calibration Facility is to provide accurate and consistent calibration of infrared lidar targets. Several CO2 lidar systems are in use or planned, and these will contribute to an improved understanding of the global climatology of aerosol backscatter coefficients in the 9-11 μm region. Since quantitative values of the backscatter coefficient are desired, a technique for accurately calibrating the atmospheric backscatter data is necessary. The use of the total backscatter to Rayleigh backscatter ratio technique, which is often used in the visible to calibrate lidar responsivity, does not apply at mid-infrared wavelengths. Thus the lidar responsivity must be determined either by a careful, systematic measurement of the optical and quantum efficiencies of the optical and detector elements in the lidar and the far-field spatial patterns of the transmitter beam and receiver field-of-view, or by the use of a calibrated hard target which can be placed in the field at a suitable range or series of ranges. Even when the former technique is employed, the use of the hard target measurement is desirable as a cross-check.
Reflectance Characteristics of Reference Materials Used in Lidar Hard Target Calibration
Authors: Haner David A. , Menzies Robert T.
Published: February 2023

There are numerous materials used for field targets in the calibration of lidar systems today. These choices are governed by the utility of the material with respect to its use, availability and mechanical properties as well as its reflectance properties. As a consequence of this wide variety of target materials, a standardization procedure is essential in order to keep the community of related users producing consistent data when quantitative backscatter cross-section measurements are conducted.
RF Discharge Technology for High Power Infrared Laser Sources
Authors: Hall D.R. , Baker H.J.
Published: February 2023

Recent advances in the understanding and control of transverse radiofrequency gas discharges in carbon dioxide and carbon monoxide laser gas mixtures have facilitated the development of new classes of laser devices, which have interesting and useful beam properties. In particular, the ability to control diffusion-cooled, transverse RF discharges with large electrode areas leads to the concept of two-dimensional (area) scaling of laser power, and the development of compact and efficient, high power laser sources (e.g. at the kilowatt average power level) which can be operated in a sealed configuration and without the need for convective gas cooling.
CO2 TEA laser for a transportable Wind LIDAR system
Authors: Stucchi E. , Galletti E. , Salvetti G. , Palange E.
Published: February 2023

CISE is carrying out since 1989 a programme of work for the development of a transportable CO2 Doppler Wind LIDAR system. Up to now the main effort has been spent in the design, the construction and the testing of a suitable pulsed laser source, as well as in the definition of system specifications and in the preliminary system design.
Homogeneous Catalysis for CO2 Lasers
Authors: Willetts D V , Harris M R
Published: February 2023

The attainment of long sealed gas lifetimes is one of the few outstanding areas of carbon dioxide laser technology which need to be addressed. Electron impact dissociation of carbon dioxide can be overcome by use of a catalyst to recombine the carbon monoxide and oxygen so formed. Heterogeneous catalysts have been extensively studied; although effective, such catalysts necessarily introduce problems of dust release in a vibrating environment and impedance to gas flow. In addition, attention must be paid to isotopic exchange between catalyst and gas. These difficulties disappear if a suitable homogenous catalyst can be found.
Coherent Semiconductor Laser Sources
Authors: Depatie David
Published: February 2023

Semiconductor diode lasers offer the benefits of high brightness, high efficiency, small size, and direct modulation. These sources are promising for a multitude of applications such as free space laser communications1 and laser radar.2 The development of single GaAlAs diode lasers has reached a high level of maturity in terms of power, efficiency, modulation capability and lifetime. However, narrow stripe diode lasers exhibiting good beam quality (high brightness) are typically limited to stripe widths of less than or equal to 8 µm.3 Also, facet damage problems limit outputs to 10-20 mW per micron of stripe width. Therefore, the maximum power that can be produced by good beam quality lasers is on the order of 100 mW.3 For these sources to produce higher output powers, the effective emitting area needs to be increased and/or several lasers ganged togeather in phase to form a phased array.
The design and performance of a mini-MOPA CO2 Doppler lidar transceiver for atmospheric monitoring
Authors: Pearson G.N. , Rye B.J. , Hardesty R.M.
Published: February 2023

Existing CO2 pulsed Doppler lidars utilising aerosol backscatter are in general large, labour intensive and costly. Systems have predominantly used TEA technology, which has limitations with respect to pulse repetition frequency and does not give much scope for varying the parameters of the transmitted pulse.1 In contrast to these systems, fm/cw devices utilising RF waveguide technology and achieving range resolution by means of focusing are compact, easily transported and have long sealed-off lifetimes. This project is aimed at employing contemporary diffusion-cooled RF technology to develop a compact, high pulse repetition rate (prf) pulsed Doppler lidar which operates in this attractive sealed-off, automonous mode and is capable of high spatial (<100 m) and velocity (+/-0.10 ms−1) resolutions. The instrument should be as flexible as possible allowing different pulse widths (0.1-2.0 μs), repetition rates and wavelengths to be software selectable. The applications for such an instrument would include the analysis of wind fields, species concentrations and consequently fluxes in the planetary boundary layer (implying a range capability of between 3-5 km).
Simulations of discrete spectral peak estimators for single and multiple lidar pulse returns
Authors: Hardesty R.M. , Rye Barry J.
Published: February 2023

Given an estimate of the spectrum of a time series sample drawn from a single pulse lidar return, there are several ways in which the signal frequency can be estimated. Texts on weather radar stress use of the first moment expression for estimation of the mean Doppler frequency shift, with or without threshold techniques to remove contributions from the spectrum of the noise.1,2 For lidar, there is increasing interest in discrete spectral peak estimation (DSPE) techniques,3 where the frequency at which the spectral maximum occurs is accepted as the estimate. Indeed, the weighting algorithm proposed for use with radar wind profilers4 uses a DSPE as a ’first guess’ of the mean frequency, prior to formation of a weighted average of spectral elements in the neighborhood of this value that have power levels above a selected threshold. It evidently has more in common with the DSPE method than earlier moment algorithms.
Design and Performance of a Digital Signal Processing System for Coherent Laser Radar
Authors: Hampton Diana M. , Jones William D. , Rothermel Jeffry G.
Published: February 2023

A PC-based data acquisition, analysis, and display system has been developed for use with continuous wave (cw) lidar at NASA’s Marshall Space Flight Center (MSFC). The data system was designed around a 386SX computer with lidar data collection and spectrum estimation occurring via a high speed transient capture peripheral board slaved to a digital signal processor (DSP) peripheral board. This system was developed for use during the second survey mission of NASA’s GLObal Backscatter Experiment1 (GLOBE II). MSFC supported two separate CO2 cw lidars2 for the experiment, one operating at 10.6μm and the other at 9.11μm.
Laser Atmospheric Wind Sounder Trade Studies
Authors: Kenyon D.L. , Petheram J.C. , Vitz R.C.
Published: February 2023

The Laser Atmospheric Wind Sounder (LAWS) is a facility instrument of the Earth Observing System (EOS) designed to measure global wind profiles from a low-earth-orbiting platform. LAWS consists of a pulsed CO2 laser, a meter-class optical system conically-scanning about nadir, and a heterodyne receiver. A previous paper (Petheram et al, 1989) compared various system concepts for measuring wind velocities from space and presented the LAWS Phase I preliminary design. Platform configurations were not available for instrument accommodation studies during Phase I, and so a surrogate platform based on EOS-A was used. Figure 1 shows the Phase I preliminary instrument configuration accommodated on the EOS-A type platform. This paper further refines the Phase I design and discusses the methods used to select the subsystem parameters for the chosen CO2 Doppler lidar concept, given the instrument performance requirements and the spacecraft platform constraints.
Maximum Entropy and Bayesian Methods for Processing of LAWS Data
Authors: Inguva Ramarao , Johnson Steve , Jones Bill , Bilbro James
Published: February 2023

Results from the use of the maximum entropy and Bayesian methods for processing LIDAR/LAWS data will be presented.
Inverse Algorithm for Increasing The Resolution of Pulsed Lidars
Authors: Gurdev L.L. , Stoyanov D.U. , Dreischuh T.N.
Published: February 2023

The resolution of the pulsed lidars is usually accepted to be equal to the pulse duration. In this work an inverse algorithm to improve the lidar resolution is analysed, when the sampling intervals of A/D converters are shorter than the laser pulse. The theorethical analysis, supported by computer simulations show the retrieving of the lidar profile by increased resolution. The effect of additional noises on the algorithm performance is given. The method may be used to increase the resolution of the lidar return in lidars of long emitted pulses. Similar problems have been investigated in [1,2] by introducing a correction function for the lidar equation.
Solid State Lasers for Coherent Laser Radar
Authors: Moulton Peter F. , Harrison James , Flint John H. , Rines David M.
Published: February 2023

CO2 lasers at wavelengths in the 10-μm region have been the main sources used in coherent laser radar system experiments, due in part to their ability to generate high, single-frequency output powers in both cw and pulsed operating modes. Improvements in the technology of solid state lasers have recently opened up the possibility that these devices can be used as alternatives to CO2-laser systems, providing more compact and reliable operation. Initial efforts have demonstrated coherent radar systems based on 1.06-μm-wavelength, Nd-doped and 2.1-μm-wavelength, Ho-doped lasers, with the latter devices favored in most cases because of the eye-safe operating wavelength. At present, the demonstrated output-power levels of solid state lasers, especially Ho-doped systems, fall well below those of CO2 lasers, and are not sufficient for challenging applications such as space-based atmospheric sensing. In this presentation we will describe some of our efforts to obtain better understanding of, and improvements in, solid state lasers for coherent laser radar.
Efficient High Peak Power Output from Tunable Diode-pumped Q-switched 2μm Tm,Ho:YLF laser
Authors: McGuckin B.T. , Menzies R.T.
Published: February 2023

Eyesafe 2μm holmium lasers are regarded as promising sources for use in Doppler wind sensing [1,2], DIAL water vapor profiling [3] and airborne Doppler velocimeters, which are potentially attractive in aerospace sensor applications. Comparative assessments of Earth-orbiting Doppler lidar methods for global wind measurements conclude that the overall performance efficiency of coherent Doppler lidars is not strongly wavelength dependent [4]. Therefore, for next generation instruments, a diode-pumped solid-state transmitter operating at an eyesafe wavelength would proffer the potential benefits of extended lifetime and lower mass over pulsed CO2 systems, currently the most favored candidates for such use on the grounds of more mature development. These applications motivate further investigation of this laser technology.
Atmospheric Refractive Turbulence and Coherent Laser Radar Performance
Authors: Frehlich R.G.
Published: February 2023

The performance of coherent laser radar (CLR) is determined by the transmitter-receiver aperture and the geometry of the transmitter and Local Oscillator (LO) field. The detector is assumed to have uniform quantum efficiency η
Q
and collects all the energy of the LO beam. The detector noise is assumed to be dominated by LO shot noise.
Calibration of the CO2 DIAL measurements from the ENEA station
Authors: Barbini R. , Colao F. , Palucci A. , Ribezzo. S.
Published: February 2023

The ENEA ground based Lidar facility has been developed for atmospheric studies including aerosol distributions, wind and temperature measurements as well as monitoring of minor molecular constituents and pollutants.
Transmitter Evaluation for Lidar Testbed
Authors: Montgomery W. W.
Published: February 2023

There are many technology issues facing coherent, wind measuring lidar system developers. A coherent lidar testbed is being developed to provide data on carbon dioxide laser-based lidar system components.
Single Particle Mode Coherent Lidar Measurements of Aerosol Backscatter: Error Sources and Calibration
Authors: Kavaya Michael J. , Frehlich Rod G.
Published: February 2023

A lidar system may measure the aerosol backscatter coefficient β [m-1sr-1] in many different ways: 1) the lidar may be continuous-wave (CW) or pulsed; 2) the lidar may employ direct detection or heterodyne detection; 3) the laser beam may be focused or collimated; and 4) the measurement volume may contain numerous aerosol particles (volume mode – VM), a few particles, or only one particle at a time (single particle mode - SPM). β is defined as the fraction of incident electromagnetic energy at wavelength λ [m] which is scattered by atmospheric aerosol particles in the backward direction per unit solid angle, per unit atmospheric length. It is assumed to be constant over the measurement volume of interest.
Doppler Lidar Measurements of Wind Flow and Aerosol Concentration at The Grand Canyon
Authors: Olivier Lisa D. , Banta Robert M.
Published: February 2023

Over the past several decades there has been a marked increase in wintertime haze at Grand Canyon National Park. People travel from all over the world to enjoy the canyon, sometimes to find their view of the canyon is obscured by haze. The Navajo Generating Station (NGS) Visibility Contribution Study was conducted to determine whether there would be an improvement in the visibility at the Grand Canyon during winter months if the NGS reduced its emissions. This power plant, to the north of the canyon, has been targeted as a cause of wintertime haze at the canyon. The NOAA/WPL Doppler lidar1, along with many other instruments, participated in the study. The lidar simultaneously measured radial velocity and backscattered signal intensity in and above the canyon. Doppler lidar measurements of upper-level winds, canyon winds, and aerosol distribution, for the period 28 February 1990 to 5 March 1990, are discussed in this paper.
Frequency-chirped solid state laser radars
Authors: Schulz P. A. , Henion S. R.
Published: February 2023

Solid-state laser developments, including diode laser pumping, miniaturization, and new materials, have made compact, efficient, and long-lived lasers in the 1 to 2 μm range available.[1] In addition, high-quantum-efficiency receivers operating at room temperature exist in this range. Consequently, solid-state laser radars are being considered for many applications. For single-pulse coherent radar the product of the range resolution ΔR and the velocity resolution Δv, referred to as the product resolution, is equal to cλ/4, where λ, is the wavelength of the radiation. This product resolution improves (decreases) with decreasing wavelength (Fig. 1) providing further argument for the relatively short wavelength of the solid-state laser.
Hybrid CW-Pulsed Autodyne Doppler Lidar
Authors: Churnside J. , Gordov E.P. , Khachaturyan A.V. , Shcheglov V.B. , Orlovskii V.V. , Alekseev S.B.
Published: February 2023

Both the autodyne coherent lidars and conventional coherent lidars using the cw CO2-lasers have a restricted operational range while the use of the pulsed laser increases the range significantly. We try to combine high sensitivity inherent in the autodyne lidar techniques with the capabilities of the pulsed lidar. To this end the hybrid version of cw-pulsed autodyne lidar is suggested. Here both the cw-laser and the pulsed one are placed in the same resonator. The pulsed CO2-laser generates the sounding signals while the cw-laser is used here as a a high sensitive detector. Such an approach makes it possible to determine the time delay between a pulse and its echo, the Doppler frequency shift and to increase the cw autodyne lidar operational range. The description of the experimental setup and the experimental results will be reported as well.
Multiwavelength Stimulated Raman Scattering generation for atmospheric backscattering studies
Authors: Barbini R. , Colao F. , Fantoni R. , Giorgi M. , Palucci A. , van der Steen H.J.L. , Moliterni A. G.
Published: February 2023

Recent improvements in the development of tunable solid state laser sources operating in the near IR have pushed the scientific community to consider possible LIDAR applications in the eye-safe region between 1 μm and 4 μm.
Integrating Sphere Depolarization
Authors: Haner David A. , Menzies Robert T.
Published: February 2023

In our previous work(1), we reported on angular reflectance properties of a gold standard surface commonly used in a commercially available integrating sphere for infrared reflectance studies. It was noted that the gold standard photometric function, reflectance vs. angle from line of source, exhibited a large broad off spectral reflectance and the polarization ratio (SP/SS) is on the order of about 0.1. Clearly these characteristics are not a good approximation to a Lambertian reflector.
Comparison of Backscatter Measurements with Aerosol Microphysics: Wavelength Dependence
Authors: Srivastava Vandana , Jarzembski Maurice , Clarke Antony D. , Porter John , Rothermel Jeffry
Published: February 2023

The GLObal Backscatter Experiment (GLOBE) flight survey missions were sponsored by the National Aeronautics Space Administration (NASA) during 1989 and 1990, involving a series of flights over the Pacific Ocean. Lidar backscatter and aerosol microphysics measurements were made simultaneously. Among the complement of instruments on board the NASA DC-8 aircraft were two continuous wave (CW), focused, CO2 Doppler lidars operating at 9.1μm and 10.6μm, and a thermally pre-conditioned Laser Optical Particle Counter (LOPC). Aerosol backscatter can be theoretically modeled from the measured aerosol microphysics data by using Mie theory (Mie, 1908). Comparison of this theoretical backscatter with direct lidar backscatter measurements will yield better aerosol models for various atmospheric conditions. Aerosol microphysics model can then be used to predict backscatter at other wavelengths for which lidar measurements are not currently available.
NASA Wind Measurement Instruments in the 1990s and Beyond
Authors: Kakar Ramesh
Published: February 2023

NASA has maintained a long-term investment in the development of Doppler lidar for wind measurements. The current program includes airborne lidars as well as concepts for potential shuttle and free flyer opportunities. Various airborne lidar measurement objectives, providing both new scientific data and experience applicable to future global scale measurements, will be highlighted.
The WIND data center: concept, realisation and first results
Authors: Streicher Jürgen , Rahm Stephan
Published: February 2023

The estimated 300kBytes per second data stream gives approximately 1 GBytes per hour and 2-3GBytes per flight. In the data center, these level 0 data from the WIND sensor and from the aircraft instrumentation will be combined and preprocessed. After that procedure the resulting level 1 data - the corrected LOS velocity components- can be handled further on, to produce level 2 data- the end product of the sensor line. These are, for example wind vectors or turbulent quantities together with information like time, height, and geographical position. Archiving and delivery of the data is possible at any position of the data chain. Table 1 one shows an overview for the different levels of data processing.
The ODIN1 Doppler Wind Lidar, A New Tool for Meteorological Airport Surveillance
Authors: Klein Volker , Roths Johannes , Resch Manfred , Erhard Markus , Hilber B. , Heilmann Rolf , Werner Christian , Streicher Jürgen
Published: February 2023

Severe turbulence and low altitude wind shear are posing a significant threat to landing and departing aircraft. According to FAA and ICAO statistics, more than 600 persons lost their lives between 1965 and 1985 in the United States alone.
JPL lidar multiwavelength correlative measurements during LITE overpasses of Southern California
Authors: Haner David A. , McDermid I. Stuart , Tratt David M. , Menzies Robert T.
Published: February 2023

The Lidar In-space Technology Experiment (LITE)1,2 was launched aboard the Space Shuttle Discovery on mission STS-64 at 22:23 UTC, Sept. 9, 1994. Over the ensuing 10-day period the LITE instrument accumulated 53 hours of 10-sec. averaged backscatter data within a few degrees of nadir at three wavelengths: 353, 532, and 1064 nm. The vertical resolution was 35 m and the transmit beam footprint diameter at the earth’s surface was 300 m, with an orbit inclination of 57°. The launch ensured night conditions for conjunction with most of the ground stations which supported the correlative measurement program. As part of this correlative program the Jet Propulsion Laboratory (JPL) operated two lidar systems coincident with predicted LITE overpass events. A brief description of the two systems follows.
Conical sector scan in wind velocity measurements by CW Doppler lidar
Authors: Banakh Victor A. , Kerkis Natalia N. , Smalikho Igor N. , Köpp Friedrich , Werner Christian
Published: February 2023

To determine the magnitude and direction of the horizontal wind by cw coherent lidar, some form of scanning in azimuth and elevation is required1. As is shown in Ref.2 it is possible to retrieve mean horizontal wind magnitude and direction from radial velocity data around horizontal circles centered on the vertical axes of the scanner (conical scanning). The representativeness of wind velocity values derived from scans over parts of a full circle (sector conical scanning) was studied in Ref. 1,3. In this paper we discuss the influence of dynamical turbulence on statistical uncertainty of Doppler lidar measurement of mean wind velocity in dependence on sector scanning angle and number of rotation.