Search NASA⌕ Search

SEARCH · Search NASA

Results for “absorption system”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

High-resolution photoabsorption cross sections of E1Pi - X1Sigma(+) vibrational bands of CO-12 and CO-13

Photodissociation following absorption of extreme-ultraviolet photons is an important factor in determining the abundance and isotropic fractionation of CO in diffuse and translucent interstellar clouds. The principal channel for destruction of CO-13 in such clouds begins with absorption in the (1,0) vibrational band of the E1Pi - X1Sigma(+) system; similarly, absorption in the (0,0) band begins a significant destruction channel for CO-12. Reliable modeling of the CO fractionation process depends critically upon the accuracy of the photoabsorption cross section for these bands. We have measured the cross sections for the relevant isotropic species and for the (1,0) band of CO-12. Our results, which are uncertain by about 10 percent, are for the most part larger than previous measurements.

Stark, G.↗
NASA NTRS2005

Monitoring the Intrinsic Absorption Complex Toward RX J1230.8+115

There is a very prominent intrinsic absorption complex in the spectrum of the quasar RX J1230.8+115. It was diagnosed as intrinsic due to partial covering of the quasar by the absorber, which can only happen for material very near to the quasar. Measuring a variability timescale for the absorption would allow us to place a more stringent constraint on the distance of the absorber from the central engine. Furthermore, understanding the variability and covering factors in different transitions can help to identify if it is due to changes in the ionizing source or transverse motion of the absorber. The OVI doublet is covered in the FUSE wavelength range. Unfortunately, our initial target, RX J1230.8+0115 could not be observed due to the failure of the first reaction wheel. We determined that another target, H 1821+643, could be observed and would satisfy similar science goals, understanding intrinsic narrow absorption line systems. Our specific goal for that target was to search for Ne VI11 absorption from the associated absorber. This observation was attempted, but the counts in the Sic channel, where the absorption was expected to lie, were too low to satisfy our science goal. This was, at least in part, due to a misalignment of the SiC mirrors. Because of this problem, more time was awarded. However, even the extra time was too little. It appears that the quasar may be too faint to properly align all the mirrors. So with disappointment, I report that we were not able to accomplish our science goals for this program. The funds were used to support my work with a graduate student, Jie Ding, to evaluate possible replacement targets once we learned that Rx J1230.8+115 would not be observable. We considered the intrinsic NAL candidates that we could find through a partial coverage analysis of doublets in the STIS E140M and E230M quasar spectra taken from the HST archive. We then checked the flux in the FUSE wavelength range, and in most cases of interest it was found to be too low to satisfy our S/N requirement in the exposure time we had been awarded. We decided that H1821+643 was the best choice for this project, even though the associated absorber we would be studying might in fact originate in the cluster with the quasar and not in intrinsic gas. Part of the appeal of the target, was in fact the opportunity to consider this issue. Please do not hesitate to contact me if more detail is needed for this report. I found it difficult to write a satisfying report under the circumstance and am uncertain if I've provided the proper level of information.

Charlton, Jane↗
NASA NTRS2015

Monitoring Atmospheric CO2 From Space: Challenge & Approach

Atmospheric CO2 is the key radiative forcing for the Earth's climate and may contribute a major part of the Earth's warming during the past 150 years. Advanced knowledge on the CO2 distributions and changes can lead considerable model improvements in predictions of the Earth's future climate. Large uncertainties in the predictions have been found for decades owing to limited CO2 observations. To obtain precise measurements of atmospheric CO2, certain challenges have to be overcome. For an example, global annual means of the CO2 are rather stable, but, have a very small increasing trend that is significant for multi-decadal long-term climate. At short time scales (a second to a few hours), regional and subcontinental gradients in the CO2 concentration are very small and only in an order of a few parts per million (ppm) compared to the mean atmospheric CO2 concentration of about 400 ppm, which requires atmospheric CO2 space monitoring systems with extremely high accuracy and precision (about 0.5 ppm or 0.125%) in spatiotemporal scales around 75 km and 10-s. It also requires a decadal-scale system stability. Furthermore, rapid changes in high latitude environments such as melting ice, snow and frozen soil, persistent thin cirrus clouds in Amazon and other tropical areas, and harsh weather conditions over Southern Ocean all increase difficulties in satellite atmospheric CO2 observations. Space lidar approaches using Integrated Path Differential Absorption (IPDA) technique are considered to be capable of obtaining precise CO2 measurements and, thus, have been proposed by various studies including the 2007 Decadal Survey (DS) of the U.S. National Research Council. This study considers to use the Intensity-Modulated Continuous-Wave (IM-CW) lidar to monitor global atmospheric CO2 distribution and variability from space. Development and demonstration of space lidar for atmospheric CO2 measurements have been made through joint adventure of NASA Langley Research Center and Exelis, Inc. As prototype space IPDA lidars, airborne laser absorption lidar systems operating in 1.57 CO2 absorption band have been developed and tested through lab, ground-based range, and flight campaigns. Very encouraging results have been obtained. The signal-to-noise ratio (SNR) for clear sky IPDA measurements of CO2 differential absorption optical depth (DAOD) for a 10-s integration over vegetated areas with about 10 km range was found to be as high as 1300, resulting in an error 0.077% or equivalent CO2 mixing ratio (XCO2) column precision of ~0.3 ppm. Precise range measurements using the IM-CW lidar approach were also achieved, and the uncertainties have been shown to be at sub meter level. Based on the airborne lidar development, space lidar and atmospheric CO2 observations are simulated. It shows that with the IM-CW approach, accurate atmospheric CO2 measurements can be achieved from space, and a space mission such as that proposed by the DS will meet science goals of atmospheric CO2 monitoring.

Lin, Bing↗
DOE OSTI2025

Continuum laser absorption spectroscopy of C 2 (a 3 Π u ) in a sublimating cloud of carbon black

A direct optical absorption diagnostic has been developed for rotationally resolved measurements of diatomic carbon (a 3 Π u →d 3 Π g (0,0) and (1,1)) at a repetition rate of 525 kHz and resolution of 7.3 pm over the range of 511.1–514.1 nm. The diagnostic utilizes a high-power pulsed continuum laser light source dispersed in a spectrograph and imaged by a high-speed camera. Measurements have been performed that capture the temporal evolution of C 2 number density and temperature of a cloud of carbon black sublimating in shock heated gas at high temperature and pressure (T = 5500 K, P = 3.7 atm). A simultaneous light absorption measurement of the condensed phase enables comparisons of the gaseous C 2 number density to the condensed phase mass. The continuum laser absorption diagnostic is applied to C 2 in this work but shows promise in being a simple “drop-in” system for absorption spectroscopy in the visible range at rapid repetition rates and high dispersion, filling an important gap for laser diagnostic systems.

Willhardt, Colton Dean [Univ. of Illinois at Urban↗
NASA NTRS1991

Dental equipment test during zero-gravity flight

The overall objectives of this program were to establish performance criteria and develop prototype equipment for use in the Health Maintenance Facility (HMF) in meeting the needs of dental emergencies during space missions. The primary efforts during this flight test were to test patient-operator relationships, patent (manikin) restraint and positioning, task lighting systems, use and operation of dental rotary instruments, suction and particle containment system, dental hand instrument delivery and control procedures, and the use of dental treatment materials. The initial efforts during the flight focused on verification of the efficiency of the particle containment system. An absorptive barrier was also tested in lieu of the suction collector. To test the instrument delivery system, teeth in the manikin were prepared with the dental drill to receive restorations, some with temporary filling materials and another with definitive filling material (composite resin). The best particle containment came from the combination use of the laminar-air/suction collector in concert with immediate area suction from a surgical high-volume suction tip. Lighting in the treatment area was provided by a flexible fiberoptic probe. This system is quite effective for small areas, but for general tasks ambient illumination is required. The instrument containment system (elastic cord network) was extremely effective and easy to use. The most serious problem with instrument delivey and actual treatment was lack of time during the microgravity sequences. The restorative materials handled and finished well.

Young, John↗
NASA NTRS1984

Spaceborne lidar investigations of the atmosphere

Atmospheric investigations with a spaceborne lidar system are discussed. Measurements of aerosols, O3, and H2O with the NASA/LaRC airborne DIAL system are presented as examples of data obtained from space. The NASA/CNES study of an autonomous differential absorption lidar system is described. This system is a precursor to a spaceborne lidar system. Simulations of spaceborne lidar experiments are reviewed, and laser requirements for a spaceborne lidar system are presented.

Browell, E. V.↗
NASA NTRS2002

Circumstellar Ti-II and V-II around Eta Carinae

We have used the STIS in E230H mode (R~130,000) on the Central source. We find hundreds of narrow absorption lines in about 20 velocity systems with velocities ranging from -140 km/s to -585 km/s. The prominent systems are the -140 km/s and the -513 km/s systems. The -140 km/s system has characteristically broad absorption profiles and is dominated by Fe II, Cr II absorptions. The -513 km/s system has very narrow absorption profiles and is dominated by Fe I, V II and Ti II. Both systems have many lines with lower levels being well above the ground state. Moreover, the lower levels are separated by spin energies and we suspect there is population inversion. This indicates that the species are being pumped by stellar radiation. More will be described in the presentation.

Gull, Theodore R.↗
NASA NTRS1977

Solar-powered air-conditioning

Report focuses on recent study on development of solar-powered residential air conditioners and is based on selected literature through 1975. Its purposes are to characterize thermal and mechanical systems that might be useful in development of Rankine-cycle approach to solar cooling and assessment of a Lithium Bromide/Water absorption cycle system.

Clark, D. C.↗
NASA NTRS1989

Superclustering of quasi-stellar object absorption clouds

The clustering of C IV absorption line systems along the lines of sight to the 55 quasars in the survey of Sargent, Boksenberg, and Steidel is examined. Their original result that there is strong clustering of these systems at separations less than 1000 km/s is confirmed. The peculiar velocities of the clouds that combine with the one-dimensional nature of the sampling is shown to preclude any detailed comparison of the observed clustering strength on these scales with that found for nearby systems such as galaxies. The sample also contains significant clustering on larger scales, 1000-10,000 km/s. This probably reflects true spatial clustering of an amplitude exceeding that observed for any nearby systems, even rich clusters of galaxies. The signal is due mainly to high equivalent width absorbers and is dominated by a single very large 'absorption supercluster' in the quasar 0237-233. It seems likely that this structure was produced by processes other than gravitational instability.

Heisler, Julia↗
NASA NTRS1989

A single rotating disk of H I in Arp 299 (NGC 3690/IC 694)

Ten-arcsec resolution 21-cm spectral line observations of the merging galaxies NGC 3690/IC 694 are presented. Strong H I absorption was seen at three sites of activity identified previously by Gehrz, Sramek, and Weedman (1983), and regions of weak emission were found extending from the optical edges of the system. The absorption data set lower limits on the neutral hydrogen mass contained in the nuclei and in the overlap region. The emission shows evidence of a single rotating disk of H I surrounding the system out to a radius twice that of the optical radius. This single H I disk morphology indicates that IC 694 and NGC 3690 are coverage of Arp 299 which now spans from the UV to radio regimes, thus making it possible to compare the distribution and kinematics of atomic hydrogen with previous observations, and offering new insight into the effect of a collision on a progenitor's interstellar medium.

Stanford, S. A.↗
NASA NTRS1976

Measured performance of a 3-ton LiBr absorption water chiller and its effect on cooling system operation

A 3-ton lithium bromide absorption water chiller was tested for a number of conditions involving hot-water input, chilled water, and the cooling water. The primary influences on chiller capacity were the hot water inlet temperature and the cooling water inlet temperature. One combination of these two parameters extended the output to as much as 125% of design capacity, but no combination could lower the capacity to below 60% of design. A cooling system was conceptually designed so that it could provide several modes of operation. Such flexibility is needed for any solar cooling system to be able to accommodate the varying solar energy collection and the varying building demand. It is concluded that a 3-ton absorption water chiller with the kind of performance that was measured can be incorporated into a cooling system such as that proposed, to provide efficient cooling over the specified ranges of operating conditions.

Namkoong, D.↗
NASA NTRS1998

Correlative Stratospheric Ozone Measurements with the Airborne UV DIAL System during TOTE/VOTE

The airborne UV differential absorption lidar (DIAL) system participated in the Tropical Ozone Transport Experiment/Vortex Ozone Transport Experiment (TOTE/VOTE) in late 1995/early 1996. This mission afforded the opportunity to compare the DIAL system's stratospheric ozone measuring capability with other remote-sensing instruments through correlative measurements over a latitude range from the tropics to the Arctic. These instruments included ground-based DIAL and space-based stratospheric instruments: HALOE; MLS; and SAGE II. The ozone profiles generally agreed within random error estimates for the various instruments in the middle of the profiles in the tropics, but regions of significant systematic differences, especially near or below the tropopause or at the higher altitudes were also found. The comparisons strongly suggest that the airborne UV DIAL system can play a valuable role as a mobile lower-stratospheric ozone validation instrument.

Grant, William B.↗
NASA NTRS1976

Measured performance of a 3 ton LiBr absorption water chiller and its effect on cooling system operation

A three ton lithium bromide absorption water chiller was tested for a number of conditions involving hot water input, chilled water, and the cooling water. The primary influences on chiller capacity were the hot water inlet temperature and the cooling water inlet temperature. One combination of these two parameters extended the output to as much as 125% of design capacity, but no combination could lower the capacity to below 60% of design. A cooling system was conceptually designed so that it could provide several modes of operation. Such flexibility is needed for any solar cooling system to be able to accommodate the varying solar energy collection and the varying building demand. It was concluded that a three-ton absorption water chiller with the kind of performance that was measured can be incorporated into a cooling system such as that proposed, to provide efficient cooling over the specified ranges of operating conditions.

Namkoong, D.↗
NASA NTRS1971

Radiant energy absorption enhancement in optical imaging systems

Reimaging system efficiently uses incident light and overcomes previous imaging detector problems. Optical system collects reflected and focal plane transmitted light and redirects it so it again impinges on focal plane in register with original image. Reimaging unabsorbed light increases light absorption and detector use probability.

Brown, R. M.↗
NASA NTRS1998

LASE validation experiment: preliminary processing of relative humidity from LASE derived water vapor in the middle to upper troposphere

Lidar Atmospheric Sensing Experiment (LASE) is the first fully engineered, autonomous airborne DIAL (Differentials Absorption Lidar) system to measure water vapor, aerosols, and clouds throughout the troposphere. This system uses a double-pulsed Ti:sapphire laser, which is pumped by a frequency-doubled flashlamp-pumped Nd: YAG laser, to transmit light in the 815 mn absorption band of water vapor. LASE operates by locking to a strong water vapor line and electronically tuning to any spectral position on the absorption line to choose the suitable absorption cross-section for optimum measurements over a range of concentrations in the atmosphere. During the LASE Validation Experiment, which was conducted over Wallops Island during September, 1995, LASE operated on either the strong water line for measurements in middle to upper troposphere, or on the weak water line for measurements made in the middle to lower troposphere including the boundary layer. Comparisons with water vapor measurements made by airborne dew point and frost point hygrometers, NASA/GSFC (Goddard Space Flight Center) Raman Lidar, and radiosondes showed the LASE water vapor mixing ratio measurements to have an accuracy of better than 6% or 0.01 g/kg, whichever is larger, throughout the troposphere. In addition to measuring water vapor mixing ratio profiles, LASE simultaneously measures aerosol backscattering profiles at the off-line wavelength near 815 nm from which atmospheric scattering ratio (ASR) profiles are calculated. ASR is defined as the ratio of total (aerosol + molecular) atmospheric scattering to molecular scattering. Assuming a region with very low aerosol loading can be identified, such as that typically found just below the tropopause, then the ASR can be determined. The ASR profiles are calculated by normalizing the scattering in the region containing enhanced aerosols to the expected scattering by the "clean" atmosphere at that altitude. Images of the total ASR clearly depict cloud regions, including multiple cloud layers, thin upper level cirrus, etc., throughout the troposphere. New data products that are being derived from the LASE aerosol and water measurements include: 1) aerosol extinction coefficient, 2) aerosol optical thickness, 3) precipitable water vapor, and 4) relative humidity (RH). These products can be compared with airborne in-situ, and ground and satellite remote sensing measurements,. This paper presents a preliminary examination of RH profiles in the middle to upper troposphere that are generated from LASE measured water vapor mixing ratio profiles coupled with rawinsonde profiles of temperature and pressure.

Brackett, Vincent G.↗
NASA NTRS1993

Measurement and modeling of moist processes

The keynote talk summarized five years of work simulating observed mesoscale convective systems with the RAMS (Regional Atmospheric Modeling System) model. Excellent results are obtained when simulating squall line or other convective systems that are strongly forced by fronts or other lifting mechanisms. Less highly forced systems are difficult to model. The next topic in this colloquium was measurement of water vapor and other constituents of the hydrologic cycle. Impressive accuracy was shown measuring water vapor with both the airborne DIAL (Differential Absorption Lidar) system and the the ground-based Raman Lidar. NMC's plans for initializing land water hydrology in mesoscale models was presented before water vapor measurement concepts for GCIP were discussed. The subject of using satellite data to provide mesoscale moisture and wind analyses was next. Recent activities in modeling of moist processes in mesoscale systems was reported on. These modeling activities at the Canadian Atmospheric Environment Service (AES) used a hydrostatic, variable-resolution grid model. Next the spatial resolution effects of moisture budgets was discussed; in particular, the effects of temporal resolution on heat and moisture budgets for cumulus parameterization. The conclusion of this colloquium was on modeling scale interaction processes.

Cotton, William↗
NASA NTRS1976

Optimization of absorption air-conditioning for solar energy applications

Improved performance of solar cooling systems using the lithium bromide water absorption cycle is investigated. Included are computer simulations of a solar-cooled house, analyses and measurements of heat transfer rates in absorption system components, and design and fabrication of various system components. A survey of solar collector convection suppression methods is presented.

Perry, E. H.↗