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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Airborne water vapor DIAL research: System development and field measurements

This paper describes the airborne differential absorption lidar (DIAL) system developed at the NASA Langley Research Center for remote measurement of water vapor (H2O) and aerosols in the lower atmosphere. The airborne H2O DIAL system was flight tested aboard the NASA Wallops Flight Facility (WFF) Electra aircraft in three separate field deployments between 1989 and 1991. Atmospheric measurements were made under a variety of atmospheric conditions during the flight tests, and several modifications were implemented during this development period to improve system operation. A brief description of the system and major modifications will be presented, and the most significant atmospheric observations will be described.

Higdon, Noah S.↗
NASA NTRS1995

Alexandrite laser transmitter development for airborne water vapor DIAL measurements

In the DIAL technique, the water vapor concentration profile is determined by analyzing the lidar backscatter signals for laser wavelengths tuned 'on' and 'off' a water vapor absorption line. Desired characteristics of the on-line transmitted laser beam include: pulse energy greater than or equal to 100 mJ, high-resolution tuning capability (uncertainty less than 0.25 pm), good spectral stability (jitter less than 0.5 pm about the mean), and high spectral purity (greater than 99 percent). The off-line laser is generally detuned less than 100 pm away from the water vapor line. Its spectral requirements are much less stringent. In our past research, we developed and demonstrated the airborne DIAL technique for water vapor measurements in the 720-nm spectral region using a system based on an alexandrite laser as the transmitter for the on-line wavelength and a Nd:YAG laser-pumped dye laser for the off-line wavelength. This off-line laser has been replaced by a second alexandrite laser. Diode lasers are used to injection seed both lasers for frequency and linewidth control. This eliminates the need for the two intracavity etalons utilized in our previous alexandrite laser and thereby greatly reduces the risk of optical damage. Consequently, the transmitted pulse energy can be substantially increased, resulting in greater measurement range, higher data density, and increased measurement precision. In this paper, we describe the diode injection seed source, the two alexandrite lasers, and the device used to line lock the on-line seed source to the water vapor absorption feature.

Chyba, Thomas H.↗
NASA NTRS1998

Chemistry and dynamics of the lower troposphere over North America and the North Atlantic Ocean in fall 1997 observed using an airborne UV DIAL system

The NASA Langley Research Center's airborne UV Differential Absorption Lidar (DIAL) system participated in the Subsonic Assessment, Ozone and Nitrogen Oxide Experiment (SONEX) mission from October 13 to November 12, 1997. The purpose of the mission was to study the upper troposphere/lower stratosphere in and near the North Atlantic flight corridor to better understand this region of the atmosphere and how civilian air travel in the corridor might be affecting the atmospheric chemistry. Bases of operations included NASA Ames, California (37.4 deg N, 122.1 deg W); Bangor, Maine (44.8 deg N, 68.8 deg W); Shannon, Ireland (52.7 deg N, 8.9 deg W); and Lajes, Terceira Island, Azores (38.8 deg N, 27.1 deg W). Since the UV DIAL system observes in the nadir as well as the zenith, aerosol and ozone data were obtained from near the Earth's surface to the lower stratosphere. A number of interesting features were noted relating to both chemistry and dynamics of the troposphere, which are reported here.

Grant, William B.↗
NASA NTRS2001

Compact Ozone Differential Absorption Lidar (DIAL) Transmitter Using Solid-State Dye Polymers

A new potential DIAL laser transmitter is described that uses solid-state dye laser materials to make a simpler, more compact, lower mass laser system. Two solid-state dye laser materials were tested to evaluate their performance in a laser oscillator cavity end pumped by a pulsed Nd:YAG laser at 532 nm. The polymer host polymethyl-methacrylate was injected with a pyrromethene laser dye, PM 580, or PM 597. A narrowband laser oscillator cavity was constructed to produce visible wavelengths of 578 and 600 nm which were frequency doubled into the UV region (299 or 300 nm) by using a BBO crystal, resulting in a maximum energy of 11 mJ at a wavelength of 578 nm when pumped by the Nd:YAG laser at an energy of 100 mJ (532 nm). A maximum output energy of 378 microJ was achieved in the UV region at a wavelength of 289 nm but lasted only 2000 laser shots at a repetition rate of 10 Hz. The results are promising and show that a solid-state dye laser based ozone DIAL system is possible with improvements in the design of the laser transmitter.

Jones, Alton L., Jr.↗
NASA NTRS2000

A Compact Ti:Sapphire Laser With its Third Harmonic Generation (THG) for an Airborne Ozone Differential Absorption Lidar (DIAL) Transmitter

A compact and high-pulse-energy Ti:Sapphire laser with its Third Harmonic Generation (THG) has been developed for an airborne ozone differential absorption lidar (DIAL) to study the distributions and concentrations of the ozone throughout the troposphere. The Ti:Sapphire laser, pumped by a frequency-doubled Nd:YAG laser and seeded by a single mode diode laser, is operated either at 867 nm or at 900 nm with a pulse repetition frequency of 20 Hz. High energy laser pulses (more than 110 mJ/pulse) at 867 nm or 900 nm with a desired beam quality have been achieved and utilized to generate its third harmonic at 289nm or 300nm, which are on-line and off-line wavelengths of an airborne ozone DIAL. After being experimentally compared with Beta-Barium Borate (beta - BaB2O4 or BBO) nonlinear crystals, two Lithium Triborate (LBO) crystals (5 x 5 x 20 cu mm) are selected for the Third Harmonic Generation (THG). In this paper, we report the Ti:Sapphire laser at 900 nm and its third harmonic at 300 nm. The desired high ultraviolet (UV) output pulse energy is more than 30 mJ at 300 nm and the energy conversion efficiency from 900 nm to 300 nm is 30%.

Chen, Songsheng↗
NASA NTRS2000

A Novel High Efficient Laser Transmitter Design for a Space-borne Ozone Differential Lidar (DIAL)

Development of a UV laser transmitter capable of operating from a space platform is a critical step in enabling global earth observations of aerosols and ozone at resolutions greater than current passive instrument capabilities. Tropospheric chemistry is well recognized as the next frontier for global atmospheric measurement. NASA Langley Research Center (LaRC) and the Canadian Space Agency (CSA) have jointly studied the requirements for a satellite based, global ozone monitoring instrument. The study, called Ozone Research using Advanced Cooperative Lidar Experiment (ORACLE) has defined the Differential Absorption Lidar (DIAL) instrument performance, weight and power, and configuration requirements for a space based measurement. In order to achieve the measurement resolution and acceptable signal-to-noise from lidar returns, 500mJ/pulse (5 Watts average power) is required at both 305-308nm and 315-320nm wavelengths. These are consecutive pulses, in a 10 Hz, double-pulsed format. The two wavelengths are used as the on- and off-lines for the ozone DIAL measurement. NASA Langley is currently developing technology for a UV laser transmitter capable of meeting the ORACLE requirements. Experimental efforts to date have shown that the UV generation scheme is viable, and that energies greater than l00mJ/pulse are possible. In this paper, we will briefly discuss the down select process for the proposed laser design, the study effort to date and the laser system design, including both primary and alternate approaches. We will describe UV laser technology that minimizes the total number of optical components (for enhanced reliability) as well as the number of UV coated optics required to transmit the light from the laser (for enhanced optical damage resistance). While the goal is to develop a laser that will produce 500 mJ of energy, we will describe an optional design that will produce output energies between 100 - 200 mJ/unit and techniques for combining multiple laser modules in order to transmit a minimum of 500mJ of UV energy in each pulse of the on- and off-line pulse pairs. This modular laser approach provides redundancy and significantly reduces development time, risk and cost when compared to the development of a single, 500mJ double-pulsed laser subsystem. Finally, we will summarize the laser development effort to date, including results that include the highest known UV energy ( 130 mJ at 320nm) ever produced by a solid-state laser operating in this wavelength region.

Edwards, W. C.↗
NASA NTRS1997

Development of the Lidar Atmospheric Sensing Experiment (LASE): An Advanced Airborne DIAL Instrument

The Lidar Atmospheric Sensing Experiment (LASE) Instrument is the first fully-engineered, autonomous Differential Absorption Lidar (DIAL) System for the measurement of water vapor in the troposphere (aerosol and cloud measurements are included). LASE uses a double-pulsed Ti:Sapphire laser for the transmitter with a 30 ns pulse length and 150 mJ/pulse. The laser beam is "seeded" to operate on a selected water vapor absorption line in the 815-nm region using a laser diode and an onboard absorption reference cell. A 40 cm diameter telescope collects the backscattered signals and directs them onto two detectors. LASE collects DIAL data at 5 Hz while onboard a NASA/Ames ER-2 aircraft flying at altitudes from 16-21 km. LASE was designed to operate autonomously within the environment and physical constraints of the ER-2 aircraft and to make water vapor profile measurements across the troposphere to better than 10% accuracy. LASE has flown 19 times during the development of the instrument and the validation of the science data. This paper describes the design, operation, and reliability of the LASE Instrument.

Moore, Alvah S., Jr.↗
NASA NTRS2005

III-V Compound Detectors for CO2 DIAL Measurements

Profiling of atmospheric carbon dioxide (CO2) is important for understanding the natural carbon cycle on Earth and its influence on global warming and climate change. Differential absorption lidar is a powerful remote sensing technique used for profiling and monitoring atmospheric constituents. Recently there has been an interest to apply this technique, at the 2 m wavelength, for investigating atmospheric CO2. This drives the need for high quality detectors at this wavelength. Although 2 m detectors are commercially available, the quest for a better detector is still on. The detector performance, regarding quantum efficiency, gain and associated noise, affects the DIAL signal-to-noise ratio and background signal, thereby influencing the instrument sensitivity and dynamic range. Detectors based on the III-V based compound materials shows a strong potential for such application. In this paper the detector requirements for a long range CO2 DIAL profiles will be discussed. These requirements were compared to newly developed III-V compound infrared detectors. The performance of ternary InGaSb pn junction devices will be presented using different substrates, as well as quaternary InGaAsSb npn structure. The performance study was based on experimental characterization of the devices dark current, spectral response, gain and noise. The final results are compared to the current state-of-the-art InGaAs technology. Npn phototransistor structure showed the best performance, regarding the internal gain and therefore the device signal-to-noise ratio. 2-micrometers detectivity as high as 3.9 x 10(exp 11) cmHz(sup 1/2)/W was obtained at a temperature of -20 C and 4 V bias voltage. This corresponds to a responsivity of 2650 A/W with about 60% quantum efficiency.

Refaat, Tamer F.↗
NASA NTRS2010

Field Testing of a Two-Micron DIAL System for Profiling Atmospheric Carbon Dioxide

A 2-m DIAL system has been developed at NASA Langley Research Center through the NASA Instrument Incubator Program. The system utilizes a tunable 2-m pulsed laser and an IR phototransistor for the transmitter and the receiver, respectively. The system targets the CO2 absorption line R22 in the 2.05-m band. Field experiments were conducted at West Branch, Iowa, for evaluating the system for CO2 measurement by comparison with in-situ sensors. The CO2 in-situ sensors were located on the NOAA's WBI tower at 31, 99 and 379 m altitudes, besides the NOAA s aircraft was sampling at higher altitudes. Preliminary results demonstrated the capabilities of the DIAL system in profiling atmospheric CO2 using the 2-m wavelength. Results of these experiments will be presented and discussed.

Refaat, Tamer F.↗
NASA NTRS2013

Correlation of DIAL Ozone Observations with Lightning

The purpose of this project is to see whether ozone maxima measured by the DIfferential Absorption Lidar (DIAL) instrument in Huntsville, AL may be traced back to lightning events occurring 24‐ 48 hours beforehand. The methodology is to start with lidar measurements of ozone from DIAL as well as ozonesonde measurements. The HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is then used to determine the origin of these ozone maxima 24‐48 hours prior. Data from the National Lightning Detection Network (NLDN) are used to examine the presence/absence of lightning along the trajectory. This type of analysis suggests that lightning‐produced NOx may be responsible for some of the ozone maxima over Huntsville.

Peterson, Harold↗
NASA NTRS2013

Correlation of DIAL Ozone Observations with Lightning

The purpose of this project is to see whether ozone maxima measured by the DIfferential Absorption Lidar (DIAL) instrument in Huntsville, AL may be traced back to lightning events occurring 24‐ 48 hours beforehand. The methodology is to start with lidar measurements of ozone from DIAL as well as ozonesonde measurements. The HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is then used to determine the origin of these ozone maxima 24‐48 hours prior. Data from the National Lightning Detection Network (NLDN) are used to examine the presence/absence of lightning along the trajectory. This type of analysis suggests that lightning‐produced NOx may be responsible for some of the ozone maxima over Huntsville.

Peterson, Harold S.↗
NASA NTRS2014

Correlation of DIAL Ozone Observations with Lightning

The purpose of this project is to see whether ozone maxima measured by the DIfferential Absorption Lidar (DIAL) instrument in Huntsville, AL may be traced back to lightning events occurring 24‐48 hours beforehand. The methodology is to start with lidar measurements of ozone from DIAL. The HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is then used to determine the origin of these ozone maxima 24‐48 hours prior. Data from the National Lightning Detection Network (NLDN) are used to examine the presence/absence of lightning along the trajectory. This type of analysis suggests that lightning‐produced NOx may be responsible for some of the ozone maxima over Huntsville.

Peterson, Harold↗
NASA NTRS2014

Correlation of DIAL Ozone Observations with Lightning

The purpose of this project is to see whether ozone maxima measured by the DIfferential Absorption Lidar (DIAL) instrument in Huntsville, AL may be traced back to lightning events occurring 24‐48 hours beforehand. The methodology is to start with lidar measurements of ozone from DIAL. The HYbrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model is then used to determine the origin of these ozone maxima 24‐48 hours prior. Data from the National Lightning Detection Network (NLDN) are used to examine the presence/absence of lightning along the trajectory. This type of analysis suggests that lightning‐produced NOx may be responsible for some of the ozone maxima over Huntsville.

Peterson, Harold S.↗
DOE OSTI2025

Archival records housed at USTUR support radium dial worker dosimetry

The American radium dial worker (RDW) cohort of over 3200 persons is being revisited as part of the Million Person Study (MPS) to include a modern approach to RDW dosimetry. An exceptional source of data and contextualization in this project is an extensive collection of electronic records (digitized from existing microfilm and microfiche) housed at the United States Transuranium and Uranium Registries (USTUR). Although the type, extent, and quality (e.g. legibility) of record(s) varies between individuals, the remarkable occupational, medical and demographic data include in vivo radiation measurements (e.g. radon breath, whole body counts), autopsy results, medical records (including copies of radiographs), interviews over the years, and correspondence. Of particular dosimetric interest are the details of radiation measurements. For example, there are some instances where hand-written and transcribed values are both available, along with notes providing context for why a particular measurement in a series of measurements was chosen to assign an intake, or if there were concerns about a particular measurement. Born prior to 1935, RDW have nearly all passed away. Thus, the updated dosimetry, especially for the skeletal tissues, will allow the correlation of lifetime cumulative dose with radiation risk. Here we review typical information available in this collection of historical records and highlight some interesting finds. Additionally, we discuss the relevance to current and ongoing work related to updating the dosimetry of the RDW in the MPS, including providing an example of the usefulness of information contained in these records. The RDW cohort provides a unique historical perspective on occupational exposure to radium, making it a valuable dataset for understanding long-term health effects and improving current radiation protection standards.

Million Person Study↗
NASA NTRSDate not supplied

Progress of 2.05 uM Fiber Laser Development for A Martian Co2 Dial

We have proposed a new concept for differential absorption lidar (DIAL) operating in the 2050 nm CO 2 absorption band for atmospheric CO 2 and pressure observations on Mars. This concept has earned us funding from NASA's PICASSO Program to advance 2050 nm fiber laser technology for future space applications. The laser design is an all-fiber master oscillator and power amplifier (MOPA) system. The master oscillator with pulse shaping and several stages of fiber preamplifiers has been built. Preliminary tests show the output pulse energy can reach 1 mJ, meeting our baseline goal. However, the current power amplifier design has an issue with undesired parasitic lasing at a different frequency, which exhausts pump energy and limits the laser energy. We have modified the power amplifier design to suppress parasitic lasing, and higher laser power energy is expected. To achieve high measurement accuracy, the laser frequency must be stabilized. A fraction of the master oscillator is split to lock the laser frequency to the center of the selected absorption line. The laser can then be shifted to a frequency far from the absorption line center, where extinction due to CO 2 and other trace gases is minimal, serving as the offline reference. The online wavelength is optimized at 2050.44156 nm, ensuring a CO 2 absorption optical depth (AOD) of approximately 1.1 at 3 km, which maximizes the signal-to-noise ratio (SNR) for measurements in the lower Martian atmosphere. At the conference, we will provide more details about this project and report on the progress of instrument development.

DIAL↗
DOE OSTI2022

Quadrupole and multi-collector ICP-MS analysis of 226 Ra in brain from a radium dial painter

We report two ICP-MS methods were developed to measure the radiotoxic isotope 226 Ra in brain tissues from a radium dial painter worker. The first method was a direct analysis of acid digested samples using quadrupole ICP-MS. The instrumental LOD of 226 Ra was 0.1 ng kg -1 . Polyatomic interferences at m/z 226 were investigated and Pb was identified from a polyatomic interferent in an in-house sample prepared from bovine brain, with a 226/208 formation ratio of 4 × 10 -8 . The quadrupole ICP-MS method was also used to measure levels of beryllium, strontium, and uranium. A second method was developed that included cation-exchange chromatography to separate 226 Ra followed by analysis with sector field MC-ICP-MS. The instrumental LOD for the cation exchange method with MC-ICP-MS detection was 0.5 pg kg -1 (19 mBq kg -1 ). The measured concentrations of 226 Ra in different brain regions ranged from 0.09–0.72 ng kg -1 (3.3–27 Bq kg -1 ) and radium was non-uniformly distributed in the brain.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

scikit-SUNDAE ((SUN)DIALS Differential Algebraic Equations) [SWR-24-137]

Scikit-SUNDAE provides Python bindings to SUNDIALS integrators. The implicit differential algebraic (IDA) solver and C-based variable-coefficient ordinary differential equations (CVODE) solver are both included. The name SUNDAE combines (SUN)DIALS and DAE, which stands for differential algebraic equations. Solvers specific to DAE problems are not frequently available in Python. An ordinary differential equation (ODE) solver is also included for completeness. ODEs can be categorized as a subset of DAEs (i.e., DAEs with no algebraic constraints). https://pypi.org/project/scikit-sundae

Randall, Corey↗