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 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 Atmosphere Water Vapor Differential Absorption Lidar Dial Detection System NASA TP 1999 209348 August 6 1999 written by and published by . This book was released on 1999* with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advanced Atmospheric Water Vapor DIAL Detection System written by Tamer F. Refaat and published by . This book was released on 2000 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the design and validation of this new water vapor DIAL detection system which was integrated onto a small Printed Circuit Board (PCB) with minimal weight and power consumption. Comparing its measurements to an existing DIAL system for aerosol and water vapor profiling validated the detection system.

Download or read book Advanced atmospheric water vapor DIAL detection system written by and published by DIANE Publishing. This book was released on with total page 155 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

Download or read book Characterization of Advanced Avalanche Photodiodes for Water Vapor Lidar Receivers written by Tamer F. Refaat and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 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.

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 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 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 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 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 Differential Absorption Lidar Measurements of Atmospheric Water Vapor Using a Pseudonise Code Modulated AIGaAs Laser written by Jonathan Andrew Reily Rall and published by . This book was released on 1993 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Ultra Narrownad Optical Filters for Water Vapor Differential Absorption Lidar DIAL Atmospheric Measurements written by Ingrid Stenholm and published by . This book was released on 2001 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling Multiple Scattering and Absorption for a Differential Absorption LIDAR System written by Daniel D. Blevins and published by . This book was released on 2005 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The Digital Image and Remote Sensing Image Generation (DIRSIG) model has been developed and utilized to support research at the Rochester Institute of Technology (RIT) for over a decade. The model is an established, first-principles-based scene simulation tool that has been focused on passive multi- and hyper-spectral sensing from the visible to long wave infrared (0.4 to 14 [micron]). Leveraging photon mapping techniques utilized by the computer graphics community, a first-principles-based elastic Light Detection and Ranging (LIDAR) model was incorporated into the passive radiometry framework so that the model calculates arbitrary, time-gated photon counts at the sensor for atmospheric, topographic, and backscattered returns. The active LIDAR module handles a wide variety of complicated scene geometries, a diverse set of surface and participating media optical characteristics, multiple bounce and multiple scattering effects, and a flexible suite of sensor models. This robust modeling environment allows the researcher to evaluate sensor design trades for topographic systems and the impact that scattering constituents (e.g. water vapor, dust, sediment, soot, etc.) may have on a Differential Absorption LIDAR (DIAL) system's ability to detect and qualify constituents of interest within volumes including water and atmospheric systems. The interest in modeling DIAL sensor engagements involving participating media such as gaseous plumes presented significant challenges that were overcome using the photon mapping paradigm. Intuitively, researchers suspect that multiple scattering effects from additional constituents as simple as water vapor or soot could impact a DIAL sensor's ability to detect and quantify effluents of interest within a participating medium. Traditional techniques, however, are not conducive to modeling the multiple scattering and absorption within a non-homogenous finite volume, such as a plume. Specific numerical approaches are presented for predicting sensor-reaching photon counts, including the effects of multiple scattering and absorption within a realistic plume. These approaches are discussed and benchmarked against analytically predicted results using a non-stationary, diffusion approximation. The analytical development and consistency of this new variant of photon mapping is explored along with the underlying physics and radiative transfer theory for participating media. Additionally, a LIDAR equation that accounts for multiple scattering effects is presented in conjunction with a discussion of the importance of accounting for these effects. Representative datasets generated via DIRSIG for both a topographical LIDAR and DIAL system are then shown. The results from some interesting phenomenological case studies including standard terrain topography, forest canopy penetration, plume interrogation with scattering and absorbing constituents, and camouflaged hard targets are also presented. Based upon a limited number of case studies, the effects of multiple scattering on DIAL sensor performance are also qualitatively discussed"--Abstract.