Download or read book Development of an Eye safe Diode laser based Micro pulse Differential Absorption Lidar mp DIAL for Atmospheric Water vapor and Aerosol Studies written by Amin Reza Nehrir and published by . This book was released on 2011 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation describes the design, construction, and testing of an all diode-laser-based water-vapor differential absorption lidar (DIAL) instrument through two distinct stages of development. A second generation low pulse energy, high pulse repetition frequency DIAL instrument was developed to overcome the power limitations of the first generation instrument which required unrealistic integration times approaching 1 hour. The second generation DIAL transmitter used a custom built external cavity diode laser (ECDL) as the seed source for an actively current pulsed tapered semiconductor optical amplifier (TSOA), yielding a maximum output transmitter pulse energy of 2 microjoules over a 1 microsecond duration pulse width at a 20 kHz pulse repetition frequency, decreasing the required integration Period to approximately 20-30 minutes. Nighttime and daytime water-vapor profiles were collected with the second generation DIAL instrument which showed good agreement with collocated radiosonde measurements from near the surface up to the top of the planetary boundary layer. Aerosol optical properties were also measured using the calibrated offline channel returns using the iterative Fernald solution to the lidar equation. Most recently, a third generation DIAL transmitter has been developed to further increase the output pulse energy and to also decrease the DIAL atmospheric spectral sampling time. Two custom built high power ECDL's and an electro-mechanical based fiber optic switch are used to sequentially seed a single stage actively current pulsed TSOA in order to minimize the systematic errors introduced in the DIAL retrievals resulting from air-mass miss-sampling between the two DIAL wavelengths. Peak output pulse energies of 7 microjoules have been measured over 1 microsecond pulse durations at a 10 kHz pulse repetition frequency with a 1-6 second DIAL spectral switching time, further decreasing the total required integration period to 20 minutes for both nighttime and daytime operation. The increased performance of the third generation transmitter has allowed for nighttime and daytime water vapor profiling under varying atmospheric conditions that shows good agreement with collocated radiosonde measurements up to ~ 6 km and ~ 3 km, respectively. A detailed description of the second and third generation DIAL instrument performance as well as data retrievals are presented in this dissertation. Future work to improve the current third generation DIAL instrument for full-time autonomous measurements of atmospheric water-vapor and aerosols is also discussed.

Download or read book Development and analysis of diode laser ns MOPA systems for high peak power application written by Thi Nghiem Vu and published by Cuvillier Verlag. This book was released on 2017-02-14 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work aims at designing and characterizing diode laser based master oscillator power amplifier (MOPA) systems, which are targeted to be implemented into micro light detection and ranging (LIDAR) or differential absorption LIDAR (DIAL) systems for water vapor and aerosol detections. These light sources operate in the ns-pulse regime at a repetition rate of 25 kHz, leading to a resolution in the meter range in an altitude of 6 km. The monolithic MOPA, where Master Oscillator (MO) and Power Amplifier (PA) are integrated on one single chip, operates at 1064 nm wavelength. A peak power of 16.3 W with a pulse width of 3 ns was obtained. A spectral linewidth of about 150 pm and a side mode suppression ratio (SMSR) of 30 dB was observed. A ratio of 9% between the amplified spontaneous emission (ASE) and the laser was estimated. These spectral properties fulfill the requirements for aerosol detection. The hybrid MOPA systems have separate chips for MO and PA. Different hybrid MOPA systems provide a stabilized wavelength at 1064 nm, a tunable wavelength around 975 nm and a dual wavelength around 964 nm. They therefore enable to detect a well-defined absorption line, scan over absorption line and switch between on/off line in DIAL applications, respectively. Their spectral linewidth is below 10 pm, limited by the resolution of the spectrum analyzer. An SMSR of more than 50 dB for the MO and of more than 37 dB for the whole MOPA was reached. A ratio between ASE and laser below 1% was estimated. These spectral properties meet the requirements for water vapor absorption lines detection at atmospheric condition. Diode laser based MOPA systems were therefore proven to be potential light sources for micro-pulse-LIDAR systems – the basis for a new generation of ultra-compact, low-cost systems.

Download or read book Shallow Clouds Water Vapor Circulation and Climate Sensitivity written by Robert Pincus and published by Springer. This book was released on 2018-05-29 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume presents a series of overview articles arising from a workshop exploring the links among shallow clouds, water vapor, circulation, and climate sensitivity. It provides a state-of-the art synthesis of understanding about the coupling of clouds and water vapor to the large-scale circulation. The emphasis is on two phenomena, namely the self-aggregation of deep convection and interactions between low clouds and the large-scale environment, with direct links to the sensitivity of climate to radiative perturbations. Each subject is approached using simulations, observations, and synthesizing theory; particular attention is paid to opportunities offered by new remote-sensing technologies, some still prospective. The collection provides a thorough grounding in topics representing one of the World Climate Research Program’s Grand Challenges. Previously published in Surveys in Geophysics, Volume 38, Issue 6, 2017 The aritcles “Observing Convective Aggregation”, “An Observational View of Relationships Between Moisture Aggregation, Cloud, and Radiative Heating Profiles”, “Implications of Warm Rain in Shallow Cumulus and Congestus Clouds for Large-Scale Circulations”, “A Survey of Precipitation-Induced Atmospheric Cold Pools over Oceans and Their Interactions with the Larger-Scale Environment”, “Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review”, “Mechanisms and Model Diversity of Trade-Wind Shallow Cumulus Cloud Feedbacks: A Review”, “Structure and Dynamical Influence of Water Vapor in the Lower Tropical Troposphere”, “Emerging Technologies and Synergies for Airborne and Space-Based Measurements of Water Vapor Profiles”, “Observational Constraints on Cloud Feedbacks: The Role of Active Satellite Sensors”, and “EUREC4A: A Field Campaign to Elucidate the Couplings Between Clouds, Convection and Circulation” are available as open access articles under a CC BY 4.0 license at link.springer.com.

Download or read book Hyperspectral Imaging for Fine to Medium Scale Applications in Environmental Sciences written by Michael Vohland and published by MDPI. This book was released on 2021-05-14 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of the Special Issue “Hyperspectral Imaging for Fine to Medium Scale Applications in Environmental Sciences” was to present a selection of innovative studies using hyperspectral imaging (HSI) in different thematic fields. This intention reflects the technical developments in the last three decades, which have brought the capacity of HSI to provide spectrally, spatially and temporally detailed data, favoured by e.g., hyperspectral snapshot technologies, miniaturized hyperspectral sensors and hyperspectral microscopy imaging. The present book comprises a suite of papers in various fields of environmental sciences—geology/mineral exploration, digital soil mapping, mapping and characterization of vegetation, and sensing of water bodies (including under-ice and underwater applications). In addition, there are two rather methodically/technically-oriented contributions dealing with the optimized processing of UAV data and on the design and test of a multi-channel optical receiver for ground-based applications. All in all, this compilation documents that HSI is a multi-faceted research topic and will remain so in the future.

Download or read book Water Vapor Profiling Using a Compact Widely Tunable Diode Laser Differential Absorption Lidar DIAL written by Amin Reza Nehrir and published by . This book was released on 2008 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric water vapor is an important driver of cloud formation, precipitation, and cloud microphysical structure. Changes in the cloud microphysical structure due to the interaction of aerosols and water vapor can produce more reflective clouds, resulting in more incoming solar radiation being reflected back into space, leading to an overall negative radiative forcing. Water vapor also plays an important role in the atmospheric feedback process that acts to amplify the positive radiative forcing resulting from increasing levels of atmospheric CO2. In the troposphere, where the water vapor greenhouse effect is most important, the situation is harder to quantify. A need exists for tools that allow for high spatial resolution range resolved measurements of water vapor number density up to about 4 km. One approach to obtaining this data within the boundary layer is with the Differential Absorption Lidar (DIAL) that is being developed at Montana State University. A differential absorption lidar (DIAL) instrument for automated profiling of water vapor in the lower troposphere has been designed, tested, and is in routine operation. The laser transmitter for the DIAL instrument uses a widely tunable external cavity diode laser (ECDL) to injection seed two cascaded semiconductor optical amplifiers (SOA) to produce a laser transmitter that accesses the 824-841 nm spectral range. The DIAL receiver utilizes a 28-cm-diameter Schmidt-Cassegrain telescope, an avalanche photodiode (APD) detector, and a narrow band optical filter to collect, discriminate, and measure the scattered light. A technique of correcting for the wavelength-dependent incident angle upon the narrow band optical filter as a function of range has been developed to allow accurate water vapor profiles to be measured down to 225 m above the surface. Data comparisons using the DIAL instrument and co-located radiosonde measurements are presented demonstrating the capabilities of the DIAL instrument.

Download or read book Evaluation of Tropospheric Water Vapor Profiling Using Eye safe Infrared Differential Absorption Lidar written by and published by . This book was released on 1996 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuous, high quality profiles of water vapor, free of systematic bias, and of moderate temporal and spatial resolution are fundamental to the success of the ARM CART program. In addition, these should be acquired over long periods at low operational and maintenance cost. The development and verification of realistic climate model parameterizations for clouds and net radiation balance, and the correction of other CART site sensor observations for interferences due to the presence of water vapor are critically dependent on water vapor profile measurements. To date, application of profiles have been limited by vertical resolution and uniqueness and high operating cost, or diminished daytime performance, lack of eye-safety, and high maintenance cost. Recent developments in infrared laser and detector technology make possible compact IR differential absorption lidar (DIAL) systems at eye-safe wavelengths. In the studies reported here, we develop DIAL system performance models and examine the potential of solving some of the shortcomings of previous methods using parameters representative of current technologies. These simulations are also applied to determine the strengths and weaknesses unique to the DIAL method for this application.

Download or read book Differential Absorption Lidars for Remote Sensing of Atmospheric Pressure and Temperature Profiles written by and published by . This book was released on 1995 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Differential Absorption Lidar Measurements of Atmospheric Water Vapor Using a Pseudonoise Code Modulated AlGaAs Laser written by and published by . This book was released on 1994 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Water Vapor Profiling Using a Widely Tunable Amplified Diode Laser Differential Absorption Lidar DIAL written by Michael Drew Obland and published by . This book was released on 2007 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis work involved the design, construction, and testing of a highly-tunable Differential Absorption Lidar (DIAL) instrument utilizing an all-semiconductor transmitter. It was an attempt to take advantage of semiconductor laser technology to obtain range-resolved water vapor profiles with an instrument that is cheaper, smaller, and more robust than existing field instruments. The eventual goal of this project was to demonstrate the feasibility of this DIAL instrument as a candidate for deployment in multi-point networks or satellite arrays to study water vapor flux profiles.

Download or read book Development and Deployment of a Compact Eye Safe Scanning Differential Absorption Lidar DIAL for Spatial Mapping of Carbon Dioxide for Monitoring Verification Accounting at Geologic Sequestration Sites written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A scanning differential absorption lidar (DIAL) instrument for monitoring carbon dioxide has been developed. The laser transmitter uses two tunable discrete mode laser diodes (DMLD) operating in the continuous wave (cw) mode with one locked to the online absorption wavelength and the other operating at the offline wavelength. Two in-line fiber optic switches are used to switch between online and offline operation. After the fiber optic switch, an acousto- optic modulator (AOM) is used to generate a pulse train used to injection seed an erbium doped fiber amplifier (EDFA) to produce eye-safe laser pulses with maximum pulse energies of 66 {micro}J, a pulse repetition frequency of 15 kHz, and an operating wavelength of 1.571 {micro}m. The DIAL receiver uses a 28 cm diameter Schmidt-Cassegrain telescope to collect that backscattered light, which is then monitored using a photo-multiplier tube (PMT) module operating in the photon counting mode. The DIAL instrument has been operated from a laboratory environment on the campus of Montana State University, at the Zero Emission Research Technology (ZERT) field site located in the agricultural research area on the western end of the Montana State University campus, and at the Big Sky Carbon Sequestration Partnership site located in north-central Montana. DIAL data has been collected and profiles have been validated using a co-located Licor LI-820 Gas Analyzer point sensor.

Download or read book Design of Advanced Atmospheric Water Vapor Differential Absorption Lidar DIAL Detection System written by Tamer F. Refaat and published by . This book was released on 1999 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: The measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The lidar atmospheric sensing equipment (LASE) is an instrument designed and operated by Langley Research Center for high precision water vapor measurements. The design details of a new water vapor lidar detection system that improves the measurement sensitivity of the LASE instrument by a factor of 10 are discussed. The new system consists of an advanced, very low noise, avalanche photodiode (APD) and a state-of-the-art signal processing unit. The new low-power system is also compact and lightweight so that it would be suitable for space flight and unpiloted atmospheric vehicles (UAV) applications. The whole system is contained on one small printed circuit board (9 by 15 cm[squared]). The detection system is mounted at the focal plane of a lidar receiver telescope, and the digital output is read by a personal computer with a digital data acquisition card.

Download or read book Design of Advanced Atmospheric Water Vapor Differential Absorption Lidar Dial Detection System written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-19 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: The measurement of atmospheric water vapor is very important for understanding the Earth's climate and water cycle. The lidar atmospheric sensing experiment (LASE) is an instrument designed and operated by the Langley Research Center for high precision water vapor measurements. The design details of a new water vapor lidar detection system that improves the measurement sensitivity of the LASE instrument by a factor of 10 are discussed. The new system consists of an advanced, very low noise, avalanche photodiode (APD) and a state-of-the-art signal processing circuit. The new low-power system is also compact and lightweight so that it would be suitable for space flight and unpiloted atmospheric vehicles (UAV) applications. The whole system is contained on one small printed circuit board (9 x 15 sq cm). The detection system is mounted at the focal plane of a lidar receiver telescope, and the digital output is read by a personal computer with a digital data acquisition card.Refaat, Tamer F. and Luck, William S., Jr. and DeYoung, Russell J.Langley Research CenterATMOSPHERIC MOISTURE; WATER VAPOR; DESIGN ANALYSIS; DIFFERENTIAL ABSORPTION LIDAR; DETECTION; AVALANCHES; SENSITIVITY; LOW NOISE; PHOTODIODES; SIGNAL PROCESSING; PRINTED CIRCUITS; LOW WEIGHT; SIGNAL TO NOISE RATIOS; ATMOSPHERIC SOUNDING

Download or read book Ultra Narrowband Optical Filters for Water Vapor Differential Absorption Lidar Dial Atmospheric Measurements written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2018-09-17 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: Differential absorption lidar (DIAL) systems are being deployed to make vertical profile measurements of atmospheric water vapor from ground and airborne platforms. One goal of this work is to improve the technology of such DIAL systems that they could be deployed on space-based platforms. Since background radiation reduces system performance, it is important to reduce it. One way to reduce it is to narrow the bandwidth of the optical receiver system. However, since the DIAL technique uses two or more wavelengths, in this case separated by 0.1 nm, a fixed-wavelength narrowband filter that would encompass both wavelengths would be broader than required for each line, approximately 0.02 nm. The approach employed in this project is to use a pair of tunable narrowband reflective fiber Bragg gratings. The Bragg gratings are germanium-doped silica core fiber that is exposed to ultraviolet radiation to produce index-of-refraction changes along the length of the fiber. The gratings can be tuned by stretching. The backscattered laser radiation is transmitted through an optical circulator to the gratings, reflected back to the optical circulator by one of the gratings, and then sent to a photodiode. The filter reflectivities were >90 percent, and the overall system efficiency was 30 percent.Stenholm, Ingrid and DeYoung, Russell J.Langley Research CenterBRAGG GRATINGS; DIFFERENTIAL ABSORPTION LIDAR; NARROWBAND; OPTICAL FILTERS; REFLECTANCE; ATMOSPHERIC MOISTURE; BACKSCATTERING; DOPED CRYSTALS

Download or read book Tunable Diode Laser Spectroscopy Lidar and DIAL Techniques for Environmental and Industrial Measurements written by Alan Fried and published by . This book was released on 1994 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Development of a UAV based Differential Absorption Lidar for Measuring Atmospheric Water Vapor written by Brian William Thomas and published by . This book was released on 2003 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of advanced avalanche photodiodes for water vapor lidar receivers written by and published by DIANE Publishing. This book was released on with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Advanced Avalanche Photodiodes for Water Vapor Lidar Receivers written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-05-29 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: Development of advanced differential absorption lidar (DIAL) receivers is very important to increase the accuracy of atmospheric water vapor measurements. A major component of such receivers is the optical detector. In the near-infrared wavelength range avalanche photodiodes (APD's) are the best choice for higher signal-to-noise ratio, where there are many water vapor absorption lines. In this study, characterization experiments were performed to evaluate a group of silicon-based APD's. The APD's have different structures representative of different manufacturers. The experiments include setups to calibrate these devices, as well as characterization of the effects of voltage bias and temperature on the responsivity, surface scans, noise measurements, and frequency response measurements. For each experiment, the setup, procedure, data analysis, and results are given and discussed. This research was done to choose a suitable APD detector for the development of an advanced atmospheric water vapor differential absorption lidar detection system operating either at 720, 820, or 940 nm. The results point out the benefits of using the super low ionization ratio (SLIK) structure APD for its lower noise-equivalent power, which was found to be on the order of 2 to 4 fW/Hz(sup (1/2)), with an appropriate optical system and electronics. The water vapor detection systems signal-to-noise ratio will increase by a factor of 10.Refaat, Tamer F. and Halama, Gary E. and DeYoung, Russell J.Langley Research CenterDIFFERENTIAL ABSORPTION LIDAR; ATMOSPHERIC MOISTURE; AVALANCHE DIODES; MOISTURE METERS; PHOTODIODES; RADAR RECEIVERS; WATER VAPOR; CHARACTERIZATION; RADAR MEASUREMENT; FREQUENCY RESPONSE; IONIZATION; NOISE REDUCTION; SIGNAL TO NOISE RATIOS; ELECTRIC POTENTIAL; NOISE MEASUREMENT