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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.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Apollo 14 visibility tests: Visibility of lunar surface features and lunar landing

An in-flight visibility test conducted on the Apollo 14 mission is discussed. The need for obtaining experimental data on lunar feature visibility arose from visibility problems associated with various aspects of the Apollo missions; and especially from anticipated difficulties of recognizing lunar surface features at the time of descent and landing under certain illumination conditions. Although visibility problems have influenced many other aspects of the Apollo mission, they have been particularly important for descent operations, due to the criticality of this mission phase and the crew's guidance and control role for landing site recognition and touchdown point selection. A series of analytical and photographic studies were conducted during the Apollo program (prior to as well as after the initial manned lunar operations) to delineate constraints imposed on landing operations by visibility limitations. The purpose of the visibility test conducted on Apollo 14 was to obtain data to reduce uncertainties and to extend the analytical models of visibility in the lunar environment.

Ziedman, K.↗
DOE OSTI2021

A Donor–Acceptor [2]Catenane for Visible Light Photocatalysis

Colored charge-transfer complexes can be formed by the association between electron-rich donor and electron-deficient acceptor molecules, bringing about the narrowing of HOMO–LUMO energy gaps so that they become capable of harnessing visible light. In an effort to facilitate the use of these widespread, but nonetheless weak, interactions for visible light photocatalysis, it is important to render the interactions strong and robust. Furthermore, we employ a well-known donor–acceptor [2]catenane—formed by the mechanical interlocking of cyclobis(paraquat-p-phenylene) and 1,5-dinaphtho[38]crown-10—in which the charge-transfer interactions between two 4,4'-bipyridinium and two 1,5-dioxynaphthalene units are enhanced by mechanical bonding, leading to increased absorption of visible light, even at low concentrations in solution. As a result, since this [2]catenane can generate persistent bipyridinium radical cations under continuous visible-light irradiation without the need for additional photosensitizers, it can display good catalytic activity in both photo-reductions and -oxidations, as demonstrated by hydrogen production—in the presence of platinum nanoparticles—and aerobic oxidation of organic sulfides, such as l-methionine, respectively. This research, which highlights the usefulness of nanoconfinement present in mechanically interlocked molecules for the reinforcement of weak interactions, can not only expand the potential of charge-transfer interactions in solar energy conversion and synthetic photocatalysis but also open up new possibilities for the development of active artificial molecular shuttles, switches, and machines.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Visible-telecom tunable dual-band optical isolator based on dynamic modulation in thin-film lithium niobate

Optical isolators are an essential component of photonic systems. Current integrated optical isolators have limited bandwidths due to stringent phase-matching conditions, resonant structures, or material absorption. Here, we demonstrate a wideband integrated optical isolator in thin-film lithium niobate photonics. We use dynamic standing-wave modulation in a tandem configuration to break Lorentz reciprocity and achieve isolation. We measure an isolation ratio of 15 dB and insertion loss below 0.5 dB for a continuous wave laser input at 1550 nm. In addition, we experimentally show that this isolator can simultaneously operate at visible and telecom wavelengths with comparable performance. Isolation bandwidths up to ∼100 nm can be achieved simultaneously at both visible and telecom wavelengths, limited only by the modulation bandwidth. Our device’s dual-band isolation, high flexibility, and real-time tunability can enable novel non-reciprocal functionality on integrated photonic platforms.

Shah, Manav↗
NASA NTRS1992

The ultraviolet and visible spectrum of the polycyclic aromatic hydrocarbon C10H8(+) - Possible contributions to the diffuse interstellar bands and to the ultraviolet-visible extinction

The properties of the cation of the PAH naphthalene (C10H8(+)) isolated in inert gas matrices under conditions relevant to astrophysical environments are described. The band at 6741 A is the strongest and falls close to the weak 6742 A diffuse interstellar bands (DIBs). Five other weaker bands also fall remarkably close to the positions of known DIBs. A very intense and broad continuum extended from the UV to the visible, which seems to be associated with the ion, is reported. The molar absorption coefficient at the peak of the continuum is 2.0 x 10 exp 6 cu dm/mol cm. If a continuum is a general property of PAH cations, this characteristic will have a strong impact on the understanding of how PAHs convert interstellar UV and visible radiation into IR radiation.

Salama, F.↗
DOE OSTI2021

Enhanced Visibility of Subduction Slabs by the Formation of Dense Hydrous Phase A

Abstract Phase A (Mg 7 Si 2 O 8 (OH) 6 ) is one of the important dense hydrous magnesium silicates in subducting slab, because it forms after the breakdown of antigorite serpentine and could be the dominant hydrous phase in the upper‐mantle deep slab for the water transportation into deep Earth. In this study, the compressional ( P ) and shear ( S ) wave velocities of phase A were measured at simultaneous pressure and temperature conditions up to 11 GPa and 1073 K. Combined with elastic properties of olivine and pyroxenes, we calculate the hydration effect on the velocities of harzburgite lithology in cold subduction zones throughout the depth ranges where phase A is thermodynamically stable. Our calculations suggest that the hydration increases both P ‐ and S ‐wave velocities of harzburgite; at ∼5 wt% hydration, its seismic detectability is enhanced by 1%–1.5% in velocity contrasts relative to its anhydrous counterpart.

Cai, Nao↗
DOE OSTI2021

Seismic Visibility of Eclogite in the Earth’s Upper Mantle—Implications From High Pressure‐Temperature Single‐Crystal Elastic Properties of Omphacite

Abstract Identifying and locating the geochemical and geophysical heterogeneities in the Earth’s interior is one of the most important and challenging tasks for the deep Earth scientists. Subducted oceanic crust metamorphizes into the dense eclogite in the upper mantle and is considered as a major cause of geochemical and geophysical heterogeneities in the deep Earth. In order to detect eclogitic materials inside the Earth, precise measurements of the high pressure‐temperature single‐crystal elasticity of major minerals in eclogite are thus exceedingly important. Omphacite, a Na,Al‐bearing clinopyroxene, constitutes up to 75 vol% of eclogite. In the present study, we performed the first high pressure‐temperature single‐crystal elasticity measurements of omphacite using Brillouin spectroscopy. Utilizing the finite‐strain approach, we obtained the following thermoelastic parameters for omphacite: K S0 ’ = 4.5(1), G 0 ’ = 1.53(5), ∂K S0 /∂ T = −0.029(5) GPa/K, ∂G 0 /∂ T = −0.013(5) GPa/K, with K S0 = 123(3) GPa, G 0 = 74(2) GPa, and ρ 0 = 3.34(1) g/cm 3 . We found that the seismic velocities of undeformed eclogite are similar to pyrolite at the depths of 200–300 and 410–500 km, thus eclogite is seismically invisible at these depths. Combined with the lattice‐preferred orientations of the omphacite in naturally deformed eclogites, we also modeled seismic anisotropy of eclogite at various pressure‐temperature conditions. A 10 km thick subducted eclogitic crust can result in ∼0.2 s shear wave splitting in the Earth’s upper mantle.

Hao, Ming↗
DOE OSTI2022

A visible to near-infrared nanocrystalline organic photodetector with ultrafast photoresponse

Organic photoelectron conversion devices, due to their solution process and wide use in portable devices, have attracted intensive interest. In this work, a newly developed active layer of D18:Y6 is used to fabricate an organic photodetector and the device of ITO/PEDOT:PSS/D18:Y6/Phen-NaDPO/Ag shows a responsivity of 680 mA W –1 and a detectivity of 6.35 × 10 13 Jones (1 Jones = 1 cm Hz 1/2 W –1 ) at a wavelength of 850 nm. Additionally, this device shows a wide linear dynamic range of 120 dB, indicating a potential near-infrared region (NIR) detector system. Owing to the minimal exciton binding energy of 37.6 meV for Y6, a desirable energy offset for efficient electron–hole pair dissociation and an ultrafast charge transfer of ~58 ps at the interface of D18:Y6, the obtained organic photodetector has demonstrated a photoresponse time as fast as 1.8 μs upon laser light excitation without an external driven voltage. More importantly, D18 shows a preferred out-of-plane orientation with strong intensities and Y6 exhibits a preferred orientation along the in-plane direction on lamellar stacking, which facilitates charge transport. This work has demonstrated significant progress in exploring D18:Y6 NIR organic devices with a wide photosensitivity linearity and ultrafast photoresponse.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Current status of visibility sensors for aviation

The development of a new increased range higher visibility was investigated. The visibility sensor that is currently is the Transmissometer. Current transmissometer technology provides only a factor of 10 dynamic range with a single base line. The FAA is preparing to install automated weather observing systems (AWOS) at many locations. These systems require visibilities up to approximately 5 miles. To use a transmissometer for this type of measurement, the base line must be about 1,000 feet; where alignment becomes very difficult to maintain. New technologies were developd for measuring visibility. Improved transmissometers, forward-scatter meters and back-scatter meters have become available. A current practical issue for visibility sensors is how to specify one that is good enough to meet the needs of aviation. The first question is what performance is required; how accurately must the sensor measure? Visibility sensors do not actually measure the visibility directly. The purpose of measuring the visibility is to predict what the pilot will see a considerable distance away from the sensor location. The atmosphere introduces considerable variation in the measurement and the basic sensor accuracy needed is difficult to define. The second question for high visibilities is what to use as the standard reference sensor. The third question pertains to the competitive procurement of visibility sensors, which is mandated at present. Two acceptance test procedures to be used to insure satisfactory sensor performance is examined.

David C. Burnham↗
NASA NTRS1972

Visibility of lunar surface features - Apollo 14 orbital observations and lunar landing.

Description of an in-flight visibility test conducted during the Apollo 14 mission for the purpose of validating and extending the mathematical visibility models used previously in the course of the Apollo program to examine the constraints on descent operations imposed by lunar visibility limitations. Following a background review of the effects on mission planning of the visibility limitations due to downsun lunar surface detail 'washout' and a discussion of the visibility prediction techniques previously used for studying lunar visibility problems, the visibility test rationale and procedures are defined and the test results presented. The results appear to confirm the validity of the visibility prediction techniques employed in lunar visibility problem studies. These results provide also a basis for improving the accuracy of the prediction techniques by appropriate modifications.

Ziedman, K.↗
NASA NTRS2021

Quantifying the Impacts of PM2.5 Constituents and Relative Humidity on Visibility Impairment in a Suburban Area of Eastern Asia Using Long-Term In-Situ Measurements.

The deterioration of visibility due to air pollutants and relative humidity has been a serious environmental problem in eastern Asia. In most previous studies, chemical compositions of atmospheric particles were provided using filter-based offline analyses, which were unable to provide long-term and in-situ measurements that resolve sufficient temporal variations of air pollution and meteorology, hindering the resolution of the relationship between air quality and visibility. Here, we present a year-long continuously measured data from a comprehensive suite of online instruments to investigate diurnal and seasonal impacts of the aerosol chemical compositions in PM2.5 on visibility seasonally and diurnally. The measured dry aerosol extinction at λ = 550 nm reached a closure with that predicted by aerosol compositions within 12%. However, the hygroscopic growth of particles under ambient RH could enhance the aerosol extinction by a factor of 2 – 6, matching the perceptive visibility of the public. Particulate ammonium nitrate was most sensitive to reducing visibility, while ammonium sulfate contributed the most to the light extinction. In spring and winter, the monsoon and stagnant air masses reduced the visibility and increased PM2.5 (> 35 μg m-3).The moisture was found to substantially enhance the light extinction under RH = 60 – 90%,reducing visibility by approximately 15 km, largely attributed to hygroscopic inorganic salts.This study serves as a metric to highlight the need to consider the influence of RH, and aqueous reactions in producing secondary inorganic aerosols on atmospheric visibility, underpinning the more accurate mitigation strategies of air pollution.

visibility↗
DOE OSTI2022

Ultra-low loss visible light waveguides for integrated atomic, molecular, and quantum photonics

Atomic, molecular and optical (AMO) visible light systems are the heart of precision applications including quantum, atomic clocks and precision metrology. As these systems scale in terms of number of lasers, wavelengths, and optical components, their reliability, space occupied, and power consumption will push the limits of using traditional laboratory-scale lasers and optics. Visible light photonic integration is critical to advancing AMO based sciences and applications, yet key performance aspects remain to be addressed, most notably waveguide losses and laser phase noise and stability. Additionally, a visible light integrated solution needs to be wafer-scale CMOS compatible and capable of supporting a wide array of photonic components. While the regime of ultra-low loss has been achieved at telecommunication wavelengths, progress at visible wavelengths has been limited. Here, we report the lowest waveguide losses and highest resonator Qs to date in the visible range, to the best of our knowledge. We report waveguide losses at wavelengths associated with strontium transitions in the 461 nm to 802 nm wavelength range, of 0.01 dB/cm to 0.09 dB/cm and associated intrinsic resonator Q of 60 Million to 9.5 Million, a decrease in loss by factors of 6x to 2x and increase in Q by factors of 10x to 1.5x over this visible wavelength range. Additionally, we measure an absorption limited loss and Q of 0.17 dB/m and 340 million at 674 nm. This level of performance is achieved in a wafer-scale foundry compatible Si 3 N 4 platform with a 20 nm thick core and TEOS-PECVD deposited upper cladding oxide, and enables waveguides for different wavelengths to be fabricated on the same wafer with mask-only changes per wavelength. These results represent a significant step forward in waveguide platforms that operate in the visible, opening up a wide range of integrated applications that utilize atoms, ions and molecules including sensing, navigation, metrology and clocks.

Chauhan, Nitesh↗
DOE OSTI2022

Dependence of the Ratio of Total to Visible Mass on Observable Properties of Sloan Digital Sky Survey MaNGA Galaxies

Abstract Using spectroscopic observations from the Sloan Digital Sky Survey Mapping Nearby Galaxies at Apache Point Observatory Data Release 15, we study the relationships between the ratio of total to visible mass and various parameters characterizing the evolution and environment of the galaxies in this survey. Measuring the rotation curve with the relative velocities of the H α emission line across a galaxy’s surface, we estimate each galaxy’s total mass. We develop a statistical model to describe the observed distribution in the ratio of total to visible mass, from which we extract the most probable value of this mass ratio for a given sample of galaxies. We present the relationships between the ratio of total to visible mass and several characteristics describing galactic evolution, such as luminosity, gas-phase metallicity, distance to the nearest neighbor, and position on the color–magnitude diagram. We find that faint galaxies with low metallicities, typically in the blue cloud, have the highest ratios of total to visible mass. This mass ratio is significantly reduced when we include the H i mass in the total visible mass, implying that feedback mechanisms are not as strong in low-mass galaxies as previously thought. Those galaxies that exhibit the second-highest ratios of total to visible mass are the brightest with high metallicities, typically members of the red sequence or green valley. Active galactic nucleus activity is likely both the quenching mechanism and the feedback that drives the mass ratio higher in these massive galaxies. Finally, we introduce a parameterization that predicts a galaxy’s ratio of total to visible mass based only on its photometry and luminosity.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1986

Visibility related to backscatter at 1.54 micron

The lidar process was shown to have the necessary potential to fulfill the need for a remote measurement of visibility. Visibility can be inferred from a lidar return optical extinction. The wavelength 1.54 micron was chosen, being near the visible wavelength region and having a high eye safety threshol, 200,000 times higher than 1.06 micron; 1.54 is the erbium laser wavelength. This research utilized 105 measured height profiles of natural droplet size distributions data, taken in clouds, fog, and haze. These profiles were examined to determine the completeness of the droplet counting data. It was found that the particle spectrometer data were incomplete in the very light ford and haze so this portion of the data was eliminated. Utilizing the Mie theory, these droplet size distribution profiles were converted to backscatter at 1.54 micron and extinction in the visible region, 0.55 micron. Using Koschmeider's relationship, the extinction profiles were converted to visibility. The visibility and backscatter profiles were compared to develop a relationship between visibility and backscatter at 1.54 micron.

Barber, T. L.↗
DOE OSTI2024

A Full Accounting of the Visible Mass in SDSS MaNGA Disk Galaxies

We present a study of the ratio of visible mass to total mass in spiral galaxies to better understand the relative amount of dark matter present in galaxies of different masses and evolutionary stages. Using the velocities of the Hα emission line measured in spectroscopic observations from the Sloan Digital Sky Survey (SDSS) MaNGA Data Release 17 (DR 17), we evaluate the rotational velocity of over 5500 disk galaxies at their 90% elliptical Petrosian radii, R 90 . We compare this to the velocity expected from the total visible mass, which we compute from the stellar, H i, H 2 , and heavy metals and dust masses. H 2 mass measurements are available for only a small subset of galaxies observed in SDSS MaNGA DR17, so we derive a parameterization of the H 2 mass as a function of absolute magnitude in the r band using galaxies observed as part of SDSS DR7. With these parameterizations, we calculate the fraction of visible mass within R 90 that corresponds to the observed velocity. Based on statistically analyzing the likelihood of this fraction, we conclude that the null hypothesis (no dark matter) cannot be excluded at a confidence level better than 95% within the visible extent of the disk galaxies. We also find that when all mass components are included, the ratio of visible to total mass within the visible extent of star-forming disk galaxies increases with galaxy luminosity.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1992

Sea surface velocities from visible and infrared multispectral atmospheric mapping sensor imagery

High resolution (100 m), sequential Multispectral Atmospheric Mapping Sensor (MAMS) images were used in a study to calculate advective surface velocities using the Maximum Cross Correlation (MCC) technique. Radiance and brightness temperature gradient magnitude images were formed from visible (0.48 microns) and infrared (11.12 microns) image pairs, respectively, of Chandeleur Sound, which is a shallow body of water northeast of the Mississippi delta, at 145546 GMT and 170701 GMT on 30 Mar. 1989. The gradient magnitude images enhanced the surface water feature boundaries, and a lower cutoff on the gradient magnitudes calculated allowed the undesirable sunglare and backscatter gradients in the visible images, and the water vapor absorption gradients in the infrared images, to be reduced in strength. Requiring high (greater than 0.4) maximum cross correlation coefficients and spatial coherence of the vector field aided in the selection of an optimal template size of 10 x 10 pixels (first image) and search limit of 20 pixels (second image) to use in the MCC technique. Use of these optimum input parameters to the MCC algorithm, and high correlation and spatial coherence filtering of the resulting velocity field from the MCC calculation yielded a clustered velocity distribution over the visible and infrared gradient images. The velocity field calculated from the visible gradient image pair agreed well with a subjective analysis of the motion, but the velocity field from the infrared gradient image pair did not. This was attributed to the changing shapes of the gradient features, their nonuniqueness, and large displacements relative to the mean distance between them. These problems implied a lower repeat time for the imagery was needed in order to improve the velocity field derived from gradient imagery. Suggestions are given for optimizing the repeat time of sequential imagery when using the MCC method for motion studies. Applying the MCC method to the infrared brightness temperature imagery yielded a velocity field which did agree with the subjective analysis of the motion and that derived from the visible gradient imagery. Differences between the visible and infrared derived velocities were 14.9 cm/s in speed and 56.7 degrees in direction. Both of these velocity fields also agreed well with the motion expected from considerations of the ocean bottom topography and wind and tidal forcing in the study area during the 2.175 hour time interval.

Pope, P. A.↗
NASA NTRS2003

Large-Diameter Visible and Buried Impact Basins on Mars: Implications for Age of the Highlands and (Buried) Lowlands and Turn-Off of the Global Magnetic Field

The global populations of visible and buried impact basins greater than 200 km diameter revealed by high resolution gridded MOLA indicate: (a) a small (approximately 10) number of very large basins (D=1300-3000km), most of which have remained visible over martian history; (b) a much larger population of smaller basins (D=200-800 km) with many more buried than visible (on images); (c) a depletion of visible basins at intermediate diameters which may be a signature of some global-scale event (formation of the lowlands? origin of Tharsis?); and (d) a crater retention age for the buried lowlands greater than that of the visible highlands but less than that of the total (visible + buried) highlands. Crustal magnetic anomalies are generally not present in the interiors of the largest basins with two exceptions: these two (which appear to be the oldest) may predate the demise of the global magnetic field.

Frey, H. V.↗
NASA NTRS2003

Large-Diameter Visible and Buried Impact Basins on Mars: Implications for age of the Highlands and (Buried) Lowlands and Turn-off of the Global Magnetic Field

The global populations of visible and buried impact basins less than 200 km diameter revealed by high resolution gridded MOLA indicate: (a) a small (approx. 10) number of very large basins (D=1300-3000km), most of which have remained visible over martian history; (b) a much larger population of smaller basins (D=200-800 km) with many more buried than visible (on images); (c) a depletion of visible basins at intermediate diameters which may be a signature of some global-scale event (formation of the lowlands? origin of Tharsis?); and (d) a crater retention age for the buried lowlands greater than that of the visible highlands but less than that of the total (visible + buried) highlands. Crustal magnetic anomalies are generally not present in the interiors of the largest basins with two exceptions: these two (which appear to be the oldest) may predate the demise of the global magnetic field.

Frey, Herbert V.↗