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DOE OSTI2019

Heterogeneity in Local Chemical Bonding Explains Spectral Broadening in Quantum Dots with Cu Impurities

Quantum dots (QDs) with optically active Cu impurities have been proposed as heavy-metal-free alternatives to Cd and Pb chalcogenides. However, the origin of their unusual optical properties is not well understood. In particular, spectral broadening is an issue for their use in high-color-purity light-emitting diodes and reabsorption-free solar windows. In this paper, we show with density functional theory calculations that chemical bonding variations have a major effect on the optical properties of Cu-doped ZnSe QDs. The Cu–Se coordination sphere is highly covalent and therefore sensitive to local variations in electrostatics and bond geometry. Correspondingly, changes in the Cu impurity environment lead to large shifts in their ground-state energy, which causes spectral broadening when multiple Cu impurity bonding environments coexist as subensembles with distinct absorption and emission energies. We conclude that while electron–phonon coupling is stronger for these systems than for typical II–VI QDs, spectral broadening predominantly occurs because of the inhomogeneous spatial distribution of Cu impurities. This is in agreement with a study that has shown narrow (~60 meV) single-particle emission linewidths for Cu x In 2–x Se y S 2–y or “CIS” QDs, which also emit through Cu impurities. Therefore, we predict that narrow ensemble emission in photonic devices can be achieved if heterogeneity is controlled.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

NASA NTRS1974

Identification of irrigated crop types from ERTS-1 density contour maps and color infrared aerial photography

The author has identified the following significant results. The crop types of a Great Plains study area were mapped from color infrared aerial photography. Each field was positively identified from field checks in the area. Enlarged (50x) density contour maps were constructed from three ERTS-1 images taken in the summer of 1973. The map interpreted from the aerial photography was compared to the density contour maps and the accuracy of the ERTS-1 density contour map interpretations were determined. Changes in the vegetation during the growing season and harvest periods were detectable on the ERTS-1 imagery. Density contouring aids in the detection of such charges.

Marrs, R. W.↗

NASA NTRS1978

Predicted color excess ratios versus interstellar grain size

Various color excess ratios, the ratio (R) of total to selective extinction, and values of the wavelength of maximum interstellar linear polarization (lambda max) are computed and displayed as functions of mean interstellar grain size and absorption coefficients. E(V-K)/E(B-V)-E(u-b)/E(b-y) is shown to be highly sensitive to changes of mean grain size. The shape of the R versus lambda max curve is shown to depend on the amount of absorption initially present in the grains, and on the absorptivity of the material added to the grains. While no simple model of grain growth has been found to fit all the observations, the two stars with the largest values of lambda max (HD 147889 and W67) support the concept of dielectric mantles growing on dielectric grains. It is further shown that more accurate uby and JKL photometry of heavily reddened stars would permit better discrimination between grain growth theories.

Mcmillan, R. S.↗

NASA NTRS1980

Visible spectral reflectance measurements /0.33-1.1 microns/ of the Galilean satellites at many orbital phase angles

One hundred eighty-seven reflectance spectra (0.33-1.10 microns) of the Galilean satellites have been obtained. Solar phase angle color correction coefficients were derived and the spectra corrected to a solar phase of 6 deg. Solar phase angle coefficients beyond 0.55 micron are presented for the first time. The spectra as a function of orbital phase angle are presented in the form of images to display hemispheric spectral variations. Io and Europa are redder on their trailing hemispheres while Callisto is redder on its leading hemisphere. Ganymede shows small longitudinal color variations despite the complex albedo structure visible in Voyager images. Comparisons of these data with previous measurements reveal that most differences can be attributed to the solar calibration. Reflectance measurements of Io at 0.73 micron observed 8.5 years apart show a 6% global reflectance decrease. However, it is difficult to unambiguously attribute this particular decrease in reflectance to a change in Io's surface composition.

Mcfadden, L. A.↗

NASA NTRS1981

Recent developments in space-borne zodiacal light photometry

The zodiacal light experiment to be flown aboard the International Solar Polar Mission in 1985 is presented. Overall objectives of the Zodiacal Light/Background Starlight Experiment include the study of the brightness, polarization, and color of the diffuse sky brightness and the determination of the spatial distributions and physical properties of the interplanetary dust as a function of spacecraft position in and out of the ecliptic. To meet these objectives, a multicolor sky-scanning photopolarimeter will be carried on the NASA spacecraft which will provide optimized stray light suppression and a capability for changing the viewing cone angle based on the use of a stepping device. Brightness and polarization measurements will be made for 11 center wavelengths in the UV and visible with 5.6 deg circular and 1.0 sq deg rectangular fields of view.

Schwehm, G. H.↗

NASA NTRSDate not supplied

Characterization of Novel Spacecraft Materials aboard the Materials International Space Station Experiment-Flight Facility (Preliminary Results)

This work will encompass the preflight characterization of 15 novel and heritage materials currently under observation on the Materials International Space Station Experiment-Flight Facility (MISSE-FF). MISSE-FF has been upgraded to perform active reflectance measurements of the materials. Images taken in RGB/IR colors are compared to results from an extensive ground testing campaign to obtain quantitative on-orbit material evolution data. Identical materials samples are to be flown on the ram, wake, and zenith faces of MISSE-FF, enabling deconvolution of the energetic electron, proton, atomic oxygen, and ultraviolet damage pathways. Energy deposition from the space environment leads to chemical changes in the material that in turn alter the optical properties. The same chemical damage that manifests as changes in optical reflectance and absorptance also leads to changes in myriad physical properties such as mechanical strength, electrical conductivity, and chemical reactivity. Therefore, flight materials are able to be characterized based on their unique reflectance spectra by comparing on-orbit measurements of optical reflectance with extensive terrestrial experiments, which help to correlate changes in reflectance with respect to changes in other material properties. The MISSE program has been a part of the International Space Station National Laboratory for many years and has been instrumental in understanding space weather modification of material properties. However, MISSE-FF has been limited to passive experiments with only pre/post flight material studies possible. In advance of the MISSE-16 experiment, the flight facility has received a major upgrade to provide daily spectral observations by way of a RGB/IR camera and a tunable light source. The MISSE-16 mission launched in February 2022 and carries 15 material samples for 6 months of the low Earth orbital exposure. Identical materials samples are to be flown on the ram, wake, and zenith faces of MISSE-FF, enabling deconvolution of the energetic electron, proton, atomic oxygen, and ultraviolet damage pathways. This paper discusses the MISSE-16 experiment, highlights the first use of the facility upgrades, and presents results from the extensive preflight material characterization that includes directional hemispherical reflectance, bidirectional reflectance, AFM, SEM, and electrical conductivity. Additionally, data showing the modification of these properties by ground-based exposure to space-like electron and atomic oxygen flux will be discussed. Finally, updates on deployment and initial check-out of the experiment on MISSE-FF will be presented. It is the ultimate goal of this program to provide validation for the development of ground based space weather simulation facilities and techniques.

Ryan Hoffman↗

NASA NTRS1986

Ignition of bulk 302 stainless steel in oxygen by laser heating

The effect of oxygen pressure on the ignition temperature of cylindrical 302 SS specimens ignited by a focused CW CO2 laser beam in a cool, static, oxygen environment was investigated. The ignition temperature was determined quantitatively from the specimen temperature history obtained from a fast response, near infrared, two-color pyrometer, which recorded the temperature history of a spot approximately 0.5 mm in diameter and located at the center of the cylindrical 302 SS specimen's top surface. Ignition and combustion occurred in three stages. The first stage began with specimen heating and ended with ignition, the second stage corresponded to combustion, and the third stage represented cooling. The physical changes that occurred in the first stage are described.

Nguyen, K.↗

NASA NTRS1991

Corona-producing cirrus cloud properties derived from polarization lidar and photographic analyses

Polarization lidar data are used to demonstrate that clouds composed of hexagonal ice crystals can generate multiple-ringed colored coronas. Although relatively uncommon in the mid-latitude cirrus sample, the coronas are associated with unusual cloud conditions that appear to be effective in generating the displays. Invariably, the cirrus cloud tops are located at or slightly above elevated tropopauses at temperatures between -60 and -70 C. The cloud top region also generates relatively strong laser backscattering and unusually high 0.5-0.7 linear depolarization ratios. Color photograph analysis of corona ring angles indicates crystals with mean diameters of from 12 to 30 microns. The cirrus cloud types were mainly subvisual to thin cirrostratus, but also included fibrous cirrus. Estimated cloud optical thicknesses at the 0.694-micron laser wavelength ranged from about 0.001 to 0.2, where the upper limit reflects the effects of multiple scattering and/or unfavorable changes in particle characteristics in deep cirrus clouds.

Sassen, Kenneth↗

NASA NTRS1994

Ocean color remote sensing using polarization properties of reflected sunlight

The effects of the atmosphere and surface on sunlight backscattered to space by the ocean may be substantially reduced by using the unpolarized component of reflectance instead of total reflectance. At 450 nm, a wavelength of interest in ocean color remote sensing, and for typical conditions, 45% of the unpolarized reflectance may originate from the water body instead of 20% of the total reflectance, which represents a gain of a factor 2.2 in useful signal for water composition retrieval. The best viewing geometries are adjacent to the glitter region; they correspond to scattering angles around 100 deg, but they may change slightly depending on the polarization characteristics of the aerosols. As aerosol optical thickness increases, the atmosphere becomes less efficient at polarizing sunlight, and the enhancement of the water body contribution to unpolarized reflectance is reduced. Since the perturbing effects are smaller on unpolarized reflectance, at least for some viewing geometries, they may be more easily corrected, leading to a more accurate water-leaving signal and, therefore, more accurate estimates of phytoplankton pigment concentration.

R. Frouin↗

NASA NTRS2019

Improvements in the on-orbit response versus scan-angle characterization for the MODIS ocean color bands

On-orbit characterization of the response versus scan-angle (RVS) is one of the most challenging aspects of the reflective solar band (RSB) calibration for the MODIS instruments onboard the Terra and Aqua spacecraft. The degradation of the solar diffuser, together with the lack of onboard calibrators (OBCs) to cover additional scan angles, other than the one for the lunar observations, has resulted in the use of Earth view responses from the pseudo-invariant desert sites to track the on-orbit RVS changes. This approach has been implemented in Collection 6 (C6) and C6.1 for bands 1-4, 8 and 9 of both instruments and also band 10 of Terra MODIS. As the missions continue to operate over a decade beyond their designed life and the instrument optics continue to degrade, it is expected that the OBC based RVS currently applied to other bands, specifically the high-gain ocean bands, will be inadequate to maintain the long-term calibration stability. An interband calibration approach is formulated and implemented in this paper. The proposed approach relies on the use of a spectrally matching stable reference band to evaluate the long-term calibration stability of the high-gain ocean bands that typically saturate while viewing the selected calibration deserts. Results from this approach indicate a noticeable drift for Terra MODIS bands 11 and 12 whereas the Aqua bands continue to show excellent temporal stability. These results are consistent with the corrections derived by the NASA Ocean Biology Processing Group (OBPG) and are expected to have minimum impacts on the downstream science products.

MODIS↗

NASA NTRSDate not supplied

NASA’s PACE Ocean Color Instrument Thermal Design Evolution: from Goddard’s Instrument Design Lab through Flight Development

NASA’s Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission, set to launch in 2024, seeks to provide data continuity for the ocean color, aerosol and cloud measurements acquired by NASA’s on-orbit Earth Science observatories since the 1990s. It will accomplish this through its Ocean Color Instrument (OCI), an optical spectrometer being developed for hyper-spectral measurements in the ultraviolet-to-near-infrared band between 340 nm and 2260 nm. Although OCI’s instrument architecture will provide greater insight and resolution than its predecessors in this wavelength range, the engineering required to achieve this also poses a greater challenge. In thermal engineering, this translates to a more complex thermal control approach to address high heat dissipations, stringent stabilities, the volume of heat that requires transport, and changing thermal environments due to tilting of the entire instrument ±20° twice per orbit. This current work explores how the PACE OCI instrument design has evolved from its initial conception in NASA Goddard’s Instrument Design Laboratory (IDL) to the current iteration of its flight design. The IDL studies explored three separate instrument configurations and two spatial resolutions per configuration, which were then down selected to a single instrument type and spatial resolution for flight instrument development. OCI subsequently went through major project milestones, including Preliminary Design Review (PDR), Critical Design Review (CDR), Pre-Environmental Review (PER) and Pre-Ship Review (PSR), with significant design updates along the way. This paper aims to provide a comprehensive account of OCI’s thermal control architecture evolution and the engineering drivers that have shaped it, with the goal of identifying trends spanning the full instrument development timeline to inform and advance future instrument thermal designs.

PACE↗

NASA NTRSDate not supplied

NASA’s PACE Ocean Color Instrument Thermal Design Evolution: from Goddard’s Instrument Design Lab through Flight Development

PACE↗

NASA NTRS1992

The changing nature of spacecraft operations: From the Vikings of the 1970's to the great observatories of the 1990's and beyond

Four trends in spacecraft flight operations are discussed which will reduce overall program costs. These trends are the use of high-speed, highly reliable data communications systems for distributing operations functions to more convenient and cost-effective sites; the improved capability for remote operation of sensors; a continued rapid increase in memory and processing speed of flight qualified computer chips; and increasingly capable ground-based hardware and software systems, notably those augmented by artificial intelligence functions. Changes reflected by these trends are reviewed starting from the NASA Viking missions of the early 70s, when mission control was conducted at one location using expensive and cumbersome mainframe computers and communications equipment. In the 1980s, powerful desktop computers and modems enabled the Magellan project team to operate the spacecraft remotely. In the 1990s, the Hubble Space Telescope project uses multiple color screens and automated sequencing software on small computers. Given a projection of current capabilities, future control centers will be even more cost-effective.

Ledbetter, Kenneth W.↗

DOE OSTI2023

Recycling of a post-industrial printed multilayer plastic film containing polyurethane inks by solvent-targeted recovery and precipitation

The recently reported Solvent-Targeted Recovery And Precipitation (STRAP) strategy is used to deconstruct multilayer plastic packaging films into their constituent resins by selective polymer dissolution. To broaden the applicability of STRAP, we demonstrate the process with a flexible post-industrial printed multilayer plastic film used for food packaging. The material was a reverse printed film composed of polyethylene (PE), ethylene vinyl alcohol (EVOH), polyethylene terephthalate (PET), and polyurethane (PU)-based inks. Removal of all colors was observed with biomass-derived gamma-valerolactone (GVL) and the recovered polymers possessed comparable properties to the corresponding virgin resins. A technoeconomic analysis indicates that this STRAP process could be economically feasible at a processing capacity of 6,000 tons per year. Furthermore, the production of plastic films with materials recovered by this STRAP process can have a lower climate change impact than the production of films from virgin polymers.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1986

Variability of the productive habitat in the eastern equatorial Pacific

It is shown that satellite ocean color data can be used to define the spatial extent of the region of enhanced biological production (the productive habitat) in the eastern equatorial Pacific. The degree of interannual variability in the areal extent of the productive habitat and in the estimated primary production of the region is determined. Frequency distributions of satellite-derived pigment concentrations are used to determine whether major changes in phytoplankton biomass have taken place from one period to the next.

Feldman, Gene Carl↗

NASA NTRS1995

Very low mass stars and white dwarfs in NGC 6397

Deep Wide Field/Planetary Camera 2 (WFPC2) images in wide bands centered at 606 and 802 nm were taken with the Hubble Space Telescope (HST) 4.6 min from the center of the galactic globular cluster NGC 6397. The images were used to accurately position approximately 2120 stars detected in the field on a color magnitude diagram down to a limiting magnitude m(sub 814) approximately = m(sub I) approximately = 26 determined reliably and solely by counting statistics. A white dwarf sequence and a rich, narrow cluster main sequence are detected for the first time, the latter stretching from m(sub 814) = 18.5 to m(sub 814) = 24.0 where it becomes indistinguishable from the field population. Two changes of slope of the main sequence at m(sub 814) approximately = 20 and m(sub 814) approximately = 22.5 are evident. The corresponding luminosity function increases slowly from M(sub 814) approximately = 6.5 to 8.5 are expected from ground-based observations but then drops sharply from there dwon to the measurement limit. The corresponding mass function obtained bu using the only presently available mass-luminosity function for the cluster's metallicity rises to a plateau between approximately 0.25 and approximately 0.15 solar mass, but drops toward the expected mass limit of the normal hydrogen burning main sequence at approximately 0.1 solar mass. This result is in clear contrast to that obtained from the ground and implies either a substantial modification of the cluster's initial mass function due to dynamical evolution in its lifetime, or that very low mass stars are not produced in any dynamically significant amount by clusters of this type. The white dwarf sequence is in reasonable agreement with a cooling sequence of models of mass 0.5 solar mass at the canonical distance of NGC 6397 with a scatter that is most likely due to photometric errors, but may also reflect real differences in mass or chemical composition. Contamination from unresolved galaxies, which cannot be reliably identified with our filters, makes it difficult to meaningfully compare the observed white dwarf luminosity function with its theoretical counterpart.

Paresce, Francesco↗

NASA NTRS2021

Jobos Bay Water Resources: Using Earth Observations to Analyze Shoreline Changes and Understand the Effects of Sea Level Rise in Southern Puerto Rico

Jobos Bay is located on the southern coast of Puerto Rico, which is known for intense hurricane seasons and increased seasonal storm surge. Scientists at Jobos Bay National Estuarine Research Reserve (JBNERR) are concerned that sea level rise will exacerbate coastal damage from these weather events. Using NASA Earth observations, our team analyzed coastal change, land use land cover change (LULC), mangrove forest extent, and water quality of Jobos Bay. Using Google Earth Engine, we evaluated coastal change and mangrove forest habitat within the study region by classifying NASA Earth observation imagery. We created historic LULC composite images to observe how land use changes over time and improve understanding of urbanization in the watershed. Leveraging previous water quality studies, our team compared water quality datasets generated by the Optical Reef and Coastal Area Assessment (ORCAA) tool to in situ sensors provided by JBNERR partners to understand the overall quality of water in the study area with respect to turbidity, chlorophyll-a, sea surface temperature, and colored dissolved organic matter (CDOM) concentrations. We discovered that 17% of the reserve has shifted from land to water since 1997 and lost 4.85 square kilometers of mangrove habitat over the past decade. Results from this study will inform the scientists of JBNERR and community members of the regional impacts of sea level rise. Being the first comprehensive study done in the estuary in nearly a decade, this serves as a baseline for future conservation efforts and research in the estuary.

Olivia Spencer↗

NASA NTRSDate not supplied

Integrating Earth Observations and Socioeconomic Data to Address Health, Equity, and Environmental Justice

Access to reliable data about the characteristics of populations is a crucial component of decision making, policy development, and the assessment of progress towards strategic goals. Social determinants of health provide insight into the status of social and economic conditions within populations that have profound effects on public health, equity, and vulnerability. International frameworks such as the Sustainable Development Goals (SDGs) fundamentally focus on equality, but to efficiently address targets and indicators, socioeconomic data and Earth observations must be integrated to help identify populations most vulnerable to the impacts of climate change, natural disasters, health disparities, and poor policy planning. The ability to identify vulnerable populations with data analysis has the potential to empower community stakeholders with spatial awareness needed to inform decision-making that addresses equity and environmental justice issues within their communities. The EPA defines environmental justice (EJ) as “the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation and enforcement of environmental laws, regulations and policies.” NASA’s Earth Science Division (ESD) recognizes the benefits that Earth observations with NASA satellites create by equipping individuals with the knowledge to address community challenges. NASA’s Socioeconomic Data and Applications Center (SEDAC) supports the integration of socioeconomic and Earth science data as an “informational gateway.” This integration of data is advancing health, equity, and environmental justice initiatives.

Natasha Johnson-Griffin↗