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NASA NTRS2023

Mineralogical, Elemental, and Tomographic Reconnaissance Investigation for CLPS (METRIC)

METRIC is a robotic science laboratory that can determine the mineralogy, elemental chemistry, micromorphology, and thermophysical properties of planetary regolith. The METRIC suite comprises METRIC XRD/F, an X-ray diffraction/X-ray fluorescence instrument that can determine the mineralogy and elemental chemistry of regolith samples; METRIC XCT, a micro X-ray computed tomography instrument that can be used to evaluate grain/crystallite sizes and textures; METRIC IRS, an imaging spectrometer mounted on a rover that can determine mineralogy and thermophysical properties at the landing site; and a pneumatic sample collection, processing, distribution system developed by Honeybee Robotics. The payload elements could be deployed on a static lander or a rover. Data returned from the METRIC payload would inform origin, formation, and evolution of rocky planetary bodies. METRIC XRD/F draws on heritage from the CheMin instrument on the Mars Science Laboratory (MSL) Curiosity rover [1], with a few important improvements. Like CheMin, METRIC XRD/F operates in transmission geometry and uses piezoelectric actuators on sample cells in a tuning fork geometry to induce convective grain motion of the regolith to create a randomly oriented powder. MSL CheMin uses an energy-sensitive CCD to collect XRD patterns and XRF spectra simultaneously from the same sample cell, resulting in qualitative XRF data. METRIC XRD/F uses two different sample cells, one optimized for XRD and one optimized for XRF, and a silicon drift detector to detect fluoresced X-rays. This improvement to the XRF capabilities provides quantitative geochemical data of major elements down to Z = 11 and allows for the detection of minor and trace elements that are critical for evaluating geologic evolution of the Moon (e.g., P and Th). Modest improvements to the XRD geometry and hardware allow for better angular resolution and the ability to distinguish between members of the pyroxene group. METRIC XCT uses the same geometry and much of the same hardware as METRIC XRD/F, where a CCD would capture images of a regolith sample in a 3 mm diameter sample tube that is rotated 360° in steps <1°. Image brightness can be used to infer compositional data, where brighter materials indicate a higher Z, much like scanning electron microscopy. Data from METRIC XCT complement those from METRIC XRD/F. Particle size, shape, and texture can provide petrologic and provenance information, whereas vesicle size and morphology in volcanic or impact melt lithologies can inform cooling rates. METRIC IRS is a hyperspectral thermal imager that can be mounted to a lander or rover to provide mineralogical data from the broader landing site and help determine whether the samples analyzed by METRIC XRD/F and XCT are representative. The METRIC IRS spectral range (8–14 μm) and resolution (10.8 cm-1) allow for quantitative mineralogy from modelling Reststrahlen bands of major rock-forming minerals (e.g., silicates, phosphates). Radiance cubes can be processed and modelled with an onboard high-performance computer to determine mineral abundances of plagioclase, high-Ca pyroxene, pigeonite, orthopyroxene, olivine, and glass. Regolith samples can be acquired, processed, and delivered to the X-ray instruments via multiple sample handling systems, but the pneumatic sampling systems developed by Honeybee Robotics [e.g., 2] are best suited for relatively low-cost missions that are being competed for the Moon (e.g., NASA’s Payloads and Research Investigations for the Surface of the Moon program). There are pneumatic sampling systems that collect surface material and other systems that pneumatically drill up to ~1 m below the surface, providing material that has not been space weathered and has not been affected by the lander’s exhaust. [1] Blake, D. F., Vaniman, D., Achilles, C., Anderson, R., Bish, D., et al. (2012). Space Sci. Rev. 170, 341-478. https://doi.org/10.1007/s11214-012-9905-1. [2] Zacny, K., Betts, B., Hedlund, M., Long, P., Gramlich, M., Tura, K., Chu, P., Jacob, A., Garcia, A. (2014). IEEE Aerospace Conference, 3-7 March 2014, Big Sky, MT, U.S.A.

X-ray diffraction↗

DOE OSTI2020

Probing free carrier plasmons in doped semiconductors using spatially resolved electron energy loss spectroscopy

We report spatially resolved measurements of free carrier collective excitations in a doped semiconductor. Using ~10 meV resolution electron energy loss spectroscopy (EELS) in an electron microscope with Å spatial resolution, we identify both surface and bulk carrier plasmons at infrared energies in a freestanding film of indium tin oxide (ITO). The interference patterns of long wavelength propagating surface carrier plasmons are revealed using spatially resolved EELS, from which we extract a dispersion relation. We further show that the energies of these plasmons vary near the surfaces and grain boundaries of the film due to band bending. Modeling based on dielectric theory agrees very well with experimental results. Finally, carrier plasmons in amorphous and crystalline ITO films are compared. These results should also be helpful for understanding the free carrier plasmons in other doped semiconductors in nanoscale volumes.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1998

Carbon Nanotube Based Nano-Electro-Mechanical Systems (NEMS)

Carbon nanotubes (CNT) enable nanoelectromechanical systems (NEMS) because of their inherent nanostructure, intrinsic electric conductivity and mechanical resilience. The collaborative work between Stanford (experiment) and NASA Ames (theory and simulation) has made progress in two types of CNT based NEMS for nanoelectronics and sensor applications. The CNT tipped scanning probe microscopy (SPM) is a NEMS in which CNT tips are used for nanoscale probing, imaging and manipulating. It showed great improvement in probing surfaces and biological systems over conventional tips. We have recently applied it to write (lithography) and read (image) uniform SiO2 lines on large Si surface area at speed up to 0.5 mm per s. Preliminary work using approximately 10 nm multiwall nanotube tips produced approximately 10 nm structures and showed that the CNT tips didn't wear down when crashed as conventional tips often do. This presents a solution to the long standing tip-wear problem in SPM nanolithography. We have also explored potential of CNT tips in imaging DNA in water. Preliminary experiment using 10 nm CNT tips reached 5 nm resolution. The 1 nm nanolithography and 1 nm DNA imaging can be expected by using approximately 1 nm CNT tips. In contrast to CNT tipped SPM, we also fabricated CNT devices on silicon wafer in which CNTs connect patterned metallic lines on SiO2/Si by a simple chemical vapor deposition process. Using conventional lithography for silicon wafer, we have been able to obtain CNT based transistors and sensors. Investigations of the CNT NEMS as physical, biological and chemical sensors are in progress and will be discussed.

Han, Jie↗

DOE OSTI2017

Radiative detached divertor with acceptable separatrix Z eff

The feasibility study is performed for the radiative detached divertor (RDD) concept, which characterizes a variety of detached plasmas with impurity amounts providing the highest levels of divertor radiation without X-point MARFE (XPM), based on a set of restrictive criteria for the leading plasma parameters (LPPs) including, e.g., tolerable peak power loads below 1 MW/m2, low separatrix densities, allowable impurity concentrations, and acceptable Z eff values for a DIII-D like tokamak. For this, extensive simulations with the 2-D edge plasma transport code were done scanning the deuterium and impurity inventories practically for all impurity elements from beryllium to neon and the analysis of LPP variations in these scans is presented. It is shown that, for a given D inventory, the total radiation fraction with an increase in the impurity inventory reaches a flat top level, f rad = 0.85 ± 0.01, whereas the higher f rad corresponds to XPM. This critical fraction is the same for all elements and values of the D inventory. Successful RDD solutions with a flat top radiation meeting all ad hoc LPP criteria are found for some elements. Boron and nitrogen are shown to be the most promising elements for seeding, since they are capable of providing alone the successful RDD at the lowest concentrations. Several important effects on impurity radiation are considered including: cross-field impurity transport in regions with strong temperature gradients, multi-species thermal force, charge-exchange of impurity ions with D atoms originating from recombination, impurity entrainment by parallel flows, flows caused by inner/outer divertor asymmetries, and Mach &sim; 1 flows reached inside radiation-ionization fronts. The impurity radiation profiles of various elements are analyzed suggesting three patterns differing in the radiation front position with respect to the D ionization source. The modeled relocation of D from the pedestal into divertor regions; an enhanced pedestal enrichment for impurities with high first ionization potential; and RDD capability of confining inside the divertors the large D inventories as neutral atoms, are considered as effects of increasing impurity inventory. The responses of a flat-top RDD to the input parameters variation are studied. For example, dependencies of LPPs on the input power increase, which express the sharp and even bifurcation transitions between two distinct branches corresponding to the detached and attached divertors, are discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2022

Model study of the energy dependence of the correlation between anisotropic flow and the mean transverse momentum in Au + Au collisions

A hybrid model that employs the hadron-string transport model UrQMD and the (3+1)-dimensional relativistic viscous hydrodynamic code vHLLE, is used to investigate the beam energy dependence of the correlation coefficient ρ(v$^{2}_{2}$,[p T ]) between the average transverse momentum [p T ] of hadrons emitted in an event and the square of the anisotropic flow coefficient v$^{2}_{2}$. For Au+Au collisions, the model predicts characteristic patterns for the energy and event-shape dependence of the variances for [p T ] and v$^{2}_{n}$ [Var([p T ] and Var(v$^{2}_{2}$)], and the covariance of v$^{2}_{n}$ and [p T ][cov(v$^{2}_{2}$,[p T ])], consistent with the attenuation effects of the specific shear viscosity η/s. Here in contrast, ρ(v$^{2}_{2}$,[p T ]) is predicted to be insensitive to the beam energy but sensitive to the initial-state geometry of the collisions. These observations suggest that a precise set of measurements for Var([p T ]), Var(v$^{2}_{2}$), cov(v$^{2}_{2}$,[p T ]) and ρ(v$^{2}_{2}$,[p T ]) as a function of beam energy and event shape, could serve to constrain better the eccentricities and their fluctuations over the entire span of beam energies, and consequently aid precision extraction of the temperature and baryon chemical-potential dependence of η/s from the wealth of Au+Au data obtained in the RHIC beam energy scan.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2018

Crosslinked Polyacrylamide Composite Hydrogels Impregnated with Fly Ash: Synthesis, Characterization and Their Application as Fractures Sealant for High Water Producing Zones in Oil and Gas Wells

Polymeric hydrogels are designed to serve many purposes in various fields of human endeavor. Herein, crosslinked polyacrylamide (PAM) composite hydrogels impregnated with coal fly ash (CFA) were synthesized, characterized and tested as fracture sealing agents in high water producing permeable zones in petroleum industry. The concept of utilizing CFA as an inorganic additive in the matrix of hydrogel emanates from the fact that CFA constitutes majorly alumina and silica. Both chemical oxides can induce the CFA to promote the inherent properties of hydrogel. Polyethyleneimine (PEI) was chosen as the crosslinking agent. Neat PAM/PEI hydrogel and PAM/PEI–CFA hydrogels at various CFA loadings (0.5, 1 and 2 wt%) were synthesized via a transamidation reaction pathway. The developed hydrogels were characterized by hybrid rheometer, FTIR, SEM and XRD instruments. Rheological results reveal that the PAM/PEI–CFA composite hydrogels embedded with various CFA quantities were more elastic than the neat PAM/PEI hydrogel, indicating the dispersion and reinforcing effect of CFA. The functional groups of these hydrogels were confirmed by the FTIR while SEM analysis show that the surface micrographs of neat PAM/PEI hydrogel and PAM/PEI–CFA1 hydrogel were porous in several regions. In contrast, the micrographs of PAM/PEI–CFA2 and PAM/PEI–CFA3 hydrogels demonstrated dense and “net-like” structural patterns. Further, XRD analysis revealed that CFA impregnation has a significant effect on the bulk structural properties of the fabricated hydrogels. The swelling rates of these hydrogels were determined by the gravimetric method and their diffusion parameters evaluated using Fickian diffusion and Schott-order kinetic models. Efficacy of the PAM/PEI–CFA composite hydrogel as fractures sealant in oil and gas wells was conducted at a typical reservoir temperature, 90 °C, and the outcome demonstrated considerable sealing potency.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Advanced FIB-based Preparation of Cryogenically-prepared Specimens for APT Analysis

The utilization of the focused ion beam scanning electron microscope (FIB-SEM) has aided the application of Atom Probe Tomography (APT) to a continually-growing variety of materials, including soft biological materials. However, the regular application of APT to hydrated interfaces such as those found in biological and environmental materials is lacking in large part due to difficulties in specimen preparation under high and ultra-high vacuum conditions. Although a FIB-SEM based cryogenic specimen preparation approach offers a rational route to the preparation of such specimens for APT analysis, many practical aspects such as welding and limitations in the cryo stage manipulation makes it challenging for routine liftout of site-targeted specimens. In this work, we describe our recent efforts in the development of a site-specific liftout and attachment scheme for cryogenically cooled specimens involving a combination of redeposition and overcoating of organic and organometallic molecules, as shown in Fig. 1a-d for a cryogenically-frozen corroded glass sample containing a hydrated porous gel surface layer. Application of an annular milling pattern to the frozen specimens leads to a needle-shaped morphology necessary for APT analysis with the targeted water-ice filled porous corroded silicate glass region of interest near the apex. Using a custom shuttle device and environmental transfer hub at PNNL to facilitate environmentally-protected specimen transfer, APT analysis was applied to directly map, for the first time, a water/solid interface in 3D to reveal the complex nanoscale water-filled porous network of corroded glass. Application of this unique specimen preparation approach to biological specimens will also be discussed, as well as the application of a unique cryo nanomaniupulator with integrated gas injection system to enable controlled FIB-based welding under cryogenic temperatures.

59 BASIC BIOLOGICAL SCIENCES↗

NASA NTRS1993

Ku-band ocean radar backscatter observations during SWADE

We present results obtained by an airborne Ku-band scatterometer during the Surface Wave Dynamics Experiment (SWADE). The specific objective of this study is to improve our understanding of the relationship between ocean radar backscatter and near surface winds. The airborne scatterometer, NUSCAT, was flown on the NASA Ames C-130 over an instrumented oceanic area near 37 deg N and 74 deg W. A total of 10 flights from 27 Feb. to 9 Mar. 1991 were conducted. Radar backscatter at incidence angles of 0 to 60 deg were obtained. For each incidence angle, the NUSCAT antenna was azimuthally scanned in multiple complete circles to measure the azimuthal backscatter modulations. Both horizontal and vertical polarization backscatter measurements were made. In some of the flights, the cross-polarization backscatter was measured as well. Internal calibrations were carried out throughout each of the flights. Preliminary results indicate that the radar was stable to +/-0.3 dB for each flight. In this paper, we present studies of the backscatter measurements over several crossings of the Gulf Stream. In these crossings, large air-sea temperature differences were encountered and substantial changes in the radar cross section were observed. We summarize the observations and compare them to the changes of several wind variables across the Gulf Stream boundary. In one of the flights, the apparent wind near the cold side of the Gulf Stream was very low (less than 3 m/s). The behavior of the radar cross sections at such low wind speeds and a comparison with models are presented. A case study of the effects of swell on the absolute cross section and the azimuthal modulation pattern is presented. Significant wave heights larger than m were observed during SWADE. The experimentally observed effects of the swell on the radar backscatter are discussed. The effects are used to assess the uncertainties in wind retrieval due to underlying waves. A summary of azimuthal modulation from our ten-flight of NUSCAT data is given. Wind velocities, air and sea surface temperature, ocean spectrum, and other variables measured from aircraft and buoys are also shown.

Nghiem, S. V.↗

DOE OSTI2019

Spatial control of heavy-fermion superconductivity in CeIrIn 5

While crystals of strongly correlated metals exhibit a diverse set of electronic ground states, few approaches exist for spatially modulating their properties. In this study, we demonstrate disorder-free control, on the micrometer scale, over the superconducting state in samples of the heavy-fermion superconductor CeIrIn 5 . We pattern crystals by focused ion beam milling to tailor the boundary conditions for the elastic deformation upon thermal contraction during cooling. The resulting nonuniform strain fields induce complex patterns of superconductivity, owing to the strong dependence of the transition temperature on the strength and direction of strain. These findings showcase a generic approach to manipulating electronic order on micrometer length scales in strongly correlated matter without compromising the cleanliness, stoichiometry, or mean free path.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2018

Synthesis and Characterization of Sol–Gel Auto Combustion-Derived Ce/Zr-Substituted Strontium Hexaferrite Nanoparticles

In this work, Ce/Zr-substituted strontium hexaferrite (SrFe{sub 12}O{sub 19}) nanoparticles have been synthesized by the sol–gel auto combustion method and the synthesized samples were annealed at 900 {sup ∘}C for 3 h. The powder XRD pattern revealed that all the diffraction peaks match the hexagonal phase of strontium hexaferrite and the lattice parameters are determined. The VSM study revealed that the values of saturation magnetization, coercivity and remanent magnetization are decreased for the Ce/Zr-substituted strontium hexaferrite sample. Thermal analysis reveals the formation of a hexagonal phase above 670 {sup ∘}C. The specific vibration band of hexagonal ferrite was observed in the range 400–600 cm{sup −1}. The FE-SEM image shows that the particles are spherical shaped and particle size varied from 37 to 44 nm.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2013

Forward-Looking IED Detector Ground Penetrating Radar

There have been many developments of mine or metal detectors based on ground penetrating radar techniques, usually in hand-held or rover-mounted devices. In most mine or metal detector applications, conditions are in a stationary mode and detection speed is not an important factor. A novel, forward-looking, stepped-frequency ground penetrating radar (GPR) has been developed with a capability to detect improvised explosive devices (IEDs) at vehicular speeds of 15 to 20 mph (24 to 32 km/h), 10 to 20 m ahead of the vehicle, to ensure adequate time for response. The GPR system employs two horn antennas (1.7 to 2.6 GHz, 20 dBi) as transmit and receive. The detector system features a user-friendly instantaneous display on a laptop PC and is a low-power-consumption (3 W) compact system with minimal impact on vehicle operations. In practice, the whole GPR system and a laptop PC can be powered by plugging into a cigarette lighter of a vehicle. The stepped-frequency continuous-wave (CW) radar scans frequency from 1.7 to 2.6 GHz in 1,000 steps of 0.9 MHz, with the full frequency scan in 60 ms. The GPR uses a bi-static configuration with one horn antenna used as a transmitter and the other used as a receiver so that isolation between transmitter and receiver is improved. Since the horn antennas (20 dBi) are mounted on the roof of a vehicle at a shallow inclination angle (15 to 25 with respect to horizontal), there is a first-order reduction in ground reflection so that a significant amount of the total reflected power received by the GPR comes from the scattering of RF energy off of buried objects. The stepped-frequency technique works by transmitting a tone at a particular frequency, while the received signal is mixed with the transmitted tone. As a result, the output of the mixer produces a signal that indicates the strength of the received signal and the extent to which it is in phase or out of phase with the transmitted tone. By taking measurements of the phase relationship between the transmitted and received signals over a wide frequency range, an interference pattern is produced showing all target reflections. When a Fourier transform is performed on this pattern, the result is a time-domain representation of targets. Among the advantages of this technique over impulse radar is the ability to transmit and receive much more total energy, and to use non-damped, highly focused horn antennas. The novelty of the IED detector GPR has been achieved by miniaturization of GPR electronics (single electronics board, 10x5x2 cm), low power consumption (3 W), faster signal processing capability, and minimal impact on vehicle operations.

Kim, Soon Sam↗

NASA NTRS2000

Microscopic physical biomarkers in carbonate hot springs: implications in the search for life on Mars

Physical evidence of life (physical biomarkers) from the deposits of carbonate hot springs were documented at the scale of microorganisms--submillimeter to submicrometer. The four moderate-temperature (57 to 72 degrees C), neutral pH springs reported on in this study, support diverse communities of bacteria adapted to specific physical and chemical conditions. Some of the microbes coexist with travertine deposits in endolithic communities. In other cases, the microbes are rapidly coated and destroyed by precipitates but leave distinctive mineral fabrics. Some microbes adapted to carbonate hot springs produce an extracellular polymeric substance which forms a three-dimensional matrix with living cells and cell remains, known as a biofilm. Silicon and iron oxides often coat the biofilm, leading to long-term preservation. Submicrometer mineralized spheres composed of calcium fluoride or silica are common in carbonate hot spring deposits. Sphere formation is biologically mediated, but the spheres themselves are apparently not fossils or microbes. Additionally, some microbes selectively weather mineral surfaces in distinctive patterns. Hot spring deposits have been cited as prime locations for exobiological exploration of Mars. The presence of preserved microscopic physical biomarkers at all four sites supports a strategy of searching for evidence of life in hot spring deposits on Mars.

NASA Center JSC↗

DOE OSTI2017

A Novel Polyester Fabric Treated with Nanoclay/Nano TiO{sub 2}/PAMAM for Discoloration of Reactive Red 4 from Aqueous Solution Under UVA Irradiation

Here, a commercially available absorbent with a high absorbance capacity (Cloisite{sup ®} 15A) together with the high active nano photocatalyst (AEROXIDE{sup ®} TiO{sub 2} P 25) and polyamidoamine based dendrimer (PAMAM) were immobilized on polyester fabric through simple pad-dry-cure method for removing dye from an aqueous solution. Using three components with good activities toward discoloration expected to produce a substrate with an excellent discoloration capacity. FESEM images with EDX patterns and X-ray diffraction spectra revealed the presence of nanoclay and nano TiO{sub 2} on the surface of the fabric. Discoloration of Reactive Red 4 (RR4) was carried out successfully by addition of a piece of the treated fabric in the dye solution under UVA irradiation. UV–visible spectra of the remaining solutions after discoloration indicated complete discoloration of RR4 solution for several times. The photocatalytic properties of the treated fabric was not changed after consecutive discoloration however the fabric surface was colored due to the presence of nanoclay on the surface acting as the dye absorbent. Graphical Abstract: .

36 MATERIALS SCIENCE↗

NASA NTRSDate not supplied

Mapping Organic-Mineral Associations in Jezero crater

The search for potential signs of life on Mars, a primary aim of the Mars 2020 mission, is greatly informed by the detection of organic matter1. The presence of organic matter also provides key information about the habitability and biological potential of the planet throughout its history. The Perseverance rover was designed for in situ science with the ability to collect a suite of promising samples for eventual return to Earth. One of its instruments, Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals (SHERLOC), is a deep ultraviolet (DUV) Raman and fluorescence spectrometer designed to map the distribution of organic molecules and minerals on rock surfaces at a resolution of 100 μm2. With its unique spectral mapping capabilities, SHERLOC enables a novel understanding of organic-mineral relationships on Mars to better determine their formation, deposition, and preservation mechanisms. The rover’s landing site within Jezero crater combines a high potential for past habitability as the site of an ancient lake basin with a diverse set of minerals, including carbonates and clays, that may preserve organic materials and potential biosignatures. The Jezero crater floor includes three formations (fm); two of these, Máaz and Séítah, were explored as part of the mission’s first campaign. Here, we report the detection of multiple species of aromatic organic molecules using Raman and fluorescence spectroscopy across ten targets in the two formations. This is the first evidence of organic molecules in Martian materials obtained using Raman spectroscopy, and among the first using fluorescence spectroscopy, beyond Earth3. We report specific spatial patterns and classes of organic molecules in these compositionally distinct formations, potentially indicating different fates of carbon in these environments. Our findings indicate that there is a diversity of aromatic molecules prevalent on the Martian surface and these materials persist despite exposure to surface conditions. These organic molecules are largely found within minerals linked to aqueous processes, suggesting that these processes may have had a key role in organic synthesis, transport from their point of origin, or preservation.

Sunanda Sharma↗

NASA NTRS2016

Retrievals of Cloud Droplet Size from the RSP Data: Validation Using in Situ Measurements

We present comparisons of cloud droplet size distributions retrieved from the Research Scanning Polarimeter (RSP) data with correlative in situ measurements made during the North Atlantic Aerosols and Marine Ecosystems Study (NAAMES). This field experiment was based at St. Johns airport, Newfoundland, Canada with the latest deployment in May - June 2016. RSP was onboard the NASA C-130 aircraft together with an array of in situ and other remote sensing instrumentation. The RSP is an along-track scanner measuring polarized and total reflectances in9 spectral channels. Its unique high angular resolution allows for characterization of liquid water droplet size using the rainbow structure observed in the polarized reflectances in the scattering angle range between 135 and 165 degrees. A parametric fitting algorithm applied to the polarized reflectances provides retrievals of the droplet effective radius and variance assuming a prescribed size distribution shape (gamma distribution). In addition to this, we use a non-parametric method, Rainbow Fourier Transform (RFT), which allows us to retrieve the droplet size distribution (DSD) itself. The latter is important in the case of clouds with complex structure, which results in multi-modal DSDs. During NAAMES the aircraft performed a number of flight patterns specifically designed for comparison of remote sensing retrievals and in situ measurements. These patterns consisted of two flight segments above the same straight ground track. One of these segments was flown above clouds allowing for remote sensing measurements, while the other was at the cloud top where cloud droplets were sampled. We compare the DSDs retrieved from the RSP data with in situ measurements made by the Cloud Droplet Probe (CDP). The comparisons show generally good agreement with deviations explainable by the position of the aircraft within cloud and by presence of additional cloud layers in RSP view that do not contribute to the in situ DSDs. In the latter case the distributions retrieved from the RSP data were consistent with the multi-layer cloud structures observed in the correlative High Spectral Resolution Lidar (HSRL) profiles. The comparison results provide a rare validation of polarimetric droplet size retrieval techniques, which can be used for analysis of satellite data on global scale.

cloud droplets↗

NASA NTRS1992

Groundbased near-IR observations of the surface of Venus

We present images of the nightside of Venus taken in the near-infrared windows at 1.0, 1.1, 1.18, 1.28, 1.31, and 2.3 microns with the new infrared camera/spectrometer IRIS on the Anglo-Australian Telescope. These data were taken in spectral-mapping mode. This technique involves scanning the telescope perpendicular to the slit, while collecting spectra at successive slit positions across the planet. We produce data cubes with one spectral and two spatial dimensions. Images can be extracted over any wavelength regions. Each image has square pixels of 0.8 inch resolution. We reduced the scattered light from the sunlit crescent in images extracted from each window by subtracting images taken on either side of the window, where the Venus atmosphere is opaque. Unlike the short wavelength windows, which reveal thermal contrasts that originate primarily from the surface and deep atmosphere, the emission in the 2.3 microns window is produced at much higher altitudes (30-40 km). Emission contrasts seen near 2.3 microns are associated with horizontal variations in the cloud optical depths, and have rotation periods of about six days. We detect large contrasts in infrared emission (20-40 percent) across the disc of Venus in the 1.0-, 1.1-, 1.18-, 1.28-, and 1.31-micron images. Contrasts at these wavelengths may be due to a combination of variations in the optical depths of the overlying sulfuric acid clouds and differences in surface emission. Comparison with the 2.3-micron images show that the patterns seen in the 1.28- and 1.31-micron windows are consistent with cloud optical depth variations alone and require no contribution from the surface. However, images at 1.0, 1.1, and 1.8 microns from July 1991 show a dark feature having a contrast that increases with decreasing wavelength. This behavior is contrary to that expected of cloud absorption. Images taken on three successive days in October show another dark feature that is stationary with respect to the surface. These regions of lower emission correspond closely to the high-altitude surface regions of Beta Regio and Aphrodite Terra. The images can potentially reveal the near-infrared emissiveity of the surface of Venus, thereby complementing Magellan radar reflectivity and ground based radio emissivity measurements. The contrast ratio between highlands and plains is much smaller than would be expected for blackbody radiation from the surface along. Unlike at radio wavelengths, where the atmosphere is essentially transparent, at near-infrared wavelengths the atmosphere emits, absorbs, and scatters radiation, and can modify the observed topographically induced contrasts. The additional radiation from the atmosphere reduces the contrast, and further modification would be expected if terrain at different altitudes has different emissivities. A fit to our data therefore requires, and may constrain, a model of the lowest scale height of the atmosphere.

Meadows, V. S.↗

NASA NTRS2000

System Concepts for the Advanced Post-TRMM Rainfall Profiling Radars

Global rainfall is the primary distributor of latent heat through atmospheric circulation. The recently launched Tropical Rainfall Measuring Mission satellite is dedicated to advance our understanding of tropical precipitation patterns and their implications on global climate and its change. The Precipitation Radar (PR) aboard the satellite is the first radar ever flown in space and has provided. exciting, new data on the 3-D rain structures for a variety of scientific uses. However, due to the limited mission lifetime and the dynamical nature of precipitation, the TRMM PR data acquired cannot address all the issues associated with precipitation, its related processes, and the long-term climate variability. In fact, a number of new post-TRMM mission concepts have emerged in response to the recent NASA's request for new ideas on Earth science missions at the post 2002 era. This paper will discuss the system concepts for two advanced, spaceborne rainfall profiling radars. In the first portion of this paper, we will present a system concept for a second-generation spaceborne precipitation radar for operations at the Low Earth Orbit (LEO). The key PR-2 electronics system will possess the following capabilities: (1) A 13.6/35 GHz dual frequency radar electronics that has Doppler and dual-polarization capabilities. (2) A large but light weight, dual-frequency, wide-swath scanning, deployable antenna. (3) Digital chirp generation and the corresponding on-board pulse compression scheme. This will allow a significant improvement on rain signal detection without using the traditional, high-peak-power transmitters and without sacrificing the range resolution. (4) Radar electronics and algorithm to adaptively scan the antenna so that more time can be spent to observe rain rather than clear air. and (5) Built-in flexibility on the radar parameters and timing control such that the same radar can be used by different future rain missions. This will help to reduce the overall instrument development costs. In the second portion of this paper, we will present a system concept for a geostationary rainfall monitoring radar for operations at the geosynchronous Earth Orbit (GEO). In particular, the science requirements, the observational strategy, the instrument design, and the required technologies will be discussed.

Im, Eastwood↗

DOE OSTI2018

Mechanism of zeolite X crystallization from diatomite

Highlights: • The intermediate species of zeolite X appears on the surface of solid particles. • The β cages build up the intermediate species, which was consist of four-membered rings (4R) and six-membered rings (6R). • The double six-membered ring (D6R) played a critical role for the crystallization process. • The β cages interconnect via double six-membered rings to form the framework of zeolite X. - Abstract: Here we systemically investigated the crystallization process of zeolite X using diatomite, a natural cost-effective silica precursor by the hydrothermal method. To decipher the mechanism, solids were separated from the mixtures at various stages of crystallization and were characterized by XRD, SEM, solid state NMR, FT-IR, UV-Raman and XRF. The XRD patterns revealed that the crystallization started between 3 and 3.5 h and ended by 5 h. The SEM images showed that the intermediate species of zeolite X appear on the surface of particles. The FT-IR and UV-Raman spectra suggested the presence of double six-membered rings (D6R) in the framework of zeolite X and they played a critical role in the crystallization process. Furthermore, the UV-Raman spectra indicated that the secondary building units of β cages formed the intermediate species and they were interconnected via double six-membered rings to form the framework of zeolite X.

36 MATERIALS SCIENCE↗