ALBERT

Description: The atmosphere of Titan, the largest moon of Saturn, is rich in organic molecules, and it has been suggested that the moon may serve as an analog for the pre-biotic Earth due to its highly reducing chemistry and existence of global hazes. Photochemical models of Titan have predicted the presence of propadiene (historically referred to as allene), CH2CCH2, an isomer of the well-measured propyne (also called methylacetylene) CH3CCH, but its detection has remained elusive due to insufficient spectroscopic knowledge of the molecule. This has recently been remedied with an updated spectral line list. Here we present the first unambiguous detection of the molecule in any astronomical object, observed with the Texas Echelle Cross Echelle Spectrograph on the NASA Infrared Telescope Facility in 2017 July. We model its emission line near 12 m and measure a volume mixing ratio of (6.9 0.8) 10(exp 10) at 175 km, assuming a vertically increasing abundance profile as predicted in photochemical models. Cassini measurements of propyne made during 2017 April indicate that the abundance ratio of propyne to propadiene is 8.2 1.1 at the same altitude. This initial measurement of the molecule in Titan's stratosphere paves the way toward constraining the amount of atomic hydrogen available on Titan, as well as future mapping of propadiene on Titan from 8 m and larger ground-based observatories, and future detection on other planetary bodies.

Description: We formulate an analytic description of a steady-state electron cloud and affiliated surface charge, formed in the plasma wake generated as the solar wind flows horizontally over a lunar crater. The solution is complementary to the well-known self-similar plasma expansion formulation, which breaksdown at the plasma wake front and thus fails to capture a substantial region of the crater interior. The present model establishes a theoretical basis for existing simulation results, which suggest that the cavity formed below the wake front is populated mainly by electrons, resulting in a substantial negative surface charge. The electrostatic potential throughout this subwake region is determined by solving Poisson'sequation for a Maxwellian electron cloud, bounded above by the self-similar plasma expansion front and below by the electrostatically charged surface.

Description: Electromagnetic ion cyclotron (EMIC) waves are understood to be one of the dominant drivers of relativistic electron loss from Earth's radiation belts. Theory predicts that the associated gyroresonant waveparticle interaction results in a distinct energydependent biteout signature in the normalized flux distribution of electrons as they are scattered into the loss cone. We identify such signatures along with the responsible EMIC waves captured in situ by the Van Allen Probes on 1516 February 2017. Using the cold plasma approximation, we predict the pitchangle cutoffs for the scattering signature for the captured EMIC wave and find it in good agreement with the observed electron biteout scattering signature. Employing the close conjunction between the Van Allen Probes and THEMIS during this time, we explore the temporal and spatial evolution of the scattering signature, as well as the surrounding wave activity, and find that the scattering signature formed during continued wave activity over a period less than a day. These results are consistent with waveparticle interaction theory and support the hypothesis that EMIC waves are an important mechanism for rapid relativistic electron loss from the radiation belts.

Description: This concept is based on the Skylab II concept, which proposes using a SLS propellant tank as the primary structure of a habitat. Common Habitat takes this a step further, proposing an interior architecture that is equally viable as a lunar surface hab, transit hab, and Mars surface hab, thus enabling a single development to support all three long duration habitat roles. Common Habitat has been pursued by the PI and co- investigators at MSFC and other centers in a spare time / funding available basis, often with heavy student intern support. Student resources have developed preliminary concepts, but these models must be refined to reflect accurate vehicle subsystems, utilities, stowage, workstations, and other crew systems. This investigation applies NASA civil servant and contractor expertise to correct errors in the most recent student concepts in order to prepare them for future human-in-the-loop evaluations to determine the most viable configuration for a Common Habitat.

Description: The Flow Boiling and Condensation Experiment (FBCE) is a flight experiment that is designed to operate in the Fluids Integrated Rack (FIR) on the International Space Station (ISS). The objective of the FBCE is to develop an integrated two-phase flow experiment that will serve as a primary platform for obtaining flow boiling and condensation heat transfer data in microgravity. This presentation discusses the overall design of the FBCE payload, as well as the status of the FBCE hardware as it continues through final verification testing.

Description: The NASA Orbital Debris Program Office (ODPO) has used various optical assets to acquire photometric data of Earth-orbiting objects to define the orbital debris environment. To better characterize and model optical data acquired from ground-based telescopes, the Optical Measurements Center (OMC) at NASA Johnson Space Center emulates illumination conditions seen in space by using equipment and techniques that parallel telescopic observations and source-target-sensor orientations. One of the OMC goals is to improve the size calculation used for optical data by developing an optical-based Size Estimation Model. The current size estimation requires applying a Lambertian phase function, a set albedo value, and range to the observed magnitude. The first step to improving the sampled brightness of laboratory targets is to remove aspect-angle dependencies. Then, the volume of possible object viewing angles is sampled at 21 combinations of azimuth and elevation angles for each solar phase angle. Finally, the acquired images are input into an image processing program that generates approximations for the objects Bidirectional Reflectance Distribution Function (BRDF) and phase function. The BRDF is a radiometric concept that identifies an objects material composition by matching a BRDF approximated with photometric data collected by ground-based telescopes with a BRDF generated experimentally from a known object in the laboratory. This paper presents the initial BRDF and phase function approximations for various fragments/targets acquired in the OMC and how the findings will be incorporated into ODPO models. A Lambertian sphere is used as a baseline for initial size estimation calculations and phase function comparisons. Spacecraft materials and fragments from hypervelocity laboratory impact tests are also presented to compare against the current assumed Lambertian phase function used for size estimates. This paper presents the preliminary phase function analysis and plan forward to utilize a laboratory-based phase function to improve the current optical size estimates using BRDF measurements for a large volume of targets composed of various shapes, sizes, and materials.

Description: This discussion is concerned with the radar-data analysis and usage involved in the building of model orbital debris (OD) populations in the near-Earth environment, focusing on radar cross section (RCS). While varying with radar wavelength, physical dimension, material composition, overall shape and structure, the RCS of an irregular object is also strongly dependent on its spatial orientation. The historical records of observed RCSs for cataloged OD objects in the Space Surveillance Network are usually distributed over an RCS range, forming respective characteristic patterns. The National Aeronautics and Space Administration (NASA) Size Estimation Model provides an empirical probability-density function of RCS as a function of effective diameter (or characteristic length), which makes it feasible to predict possible RCS distributions for a given model OD population and to link data with model from a statistical perspective. The discussion also includes application of the widely used method of moments (MoM) and the Generalized Multi-particle Mie-solution (GMM) in the prediction of the RCS of arbitrarily shaped objects. Theoretical calculation results for an aluminum cube are compared with corresponding experimental measurements.

Description: A better understanding of IV (current voltage) curve data collected from photo voltaic cells may lead to the construction of solar cells with improved electrical properties. With this in mind, IV curve data from different types of solar cells were acquired from the Photovoltaics and Electrochemical Systems Branch, NASA Glenn Research Center. Neural networks were created to predict the chemical composition of three classes of solar cells. The success of these predictions varied with class.

Description: Who cares? Magnetograms in the upper chromosphere are needed for accurate magnetic coronal extrapolations. The CLASP2 sounding rocket took spatially resolved spectropolarimetric data of Mg II h & k in the upper chromosphere, that can be used as a pathfinder to routine magnetograms. This work: Preliminary results of the center-to-limb variation (CLV) of the linear polarization in the quiet sun. We compare the signals to recent theoretical calculations of the expected polarization which include PRD, J-state interference, and magneto-optical effects.

Description: The DebriSat project analyzes the debris from a hypervelocity impact test conducted on a 56 kg-simulated satellite target in 2014. Its purpose is to generate a comprehensive database of the size, mass, material, shape, and the radar and optical properties of fragments generated from orbital collisions of modern-built spacecraft. Three hundred ninety-one foam catch panels from the DebriSat test have been X-rayed to locate the particles within them for subsequent extraction and assessment. The data from the tens of thousands of extracted particles has heretofore been the focus of the debris assessment. The work presented here connects the X-ray sample location images to reconstruct the 3D distribution of the entire fragment cloud. Although some errors are inherent to the process, this 3D database is valuable for qualitative studies of size and energy distributions. Further, the 3D database can indicate the extent of bending or breaking of the fragments as they decelerated to full capture. By virtue of its full sphere perspective, the 3D database allows graphical insight to the physics of the collision and breakup. This 3D representation has been developed as a point and click graphical interface to retrieve the full data set on individual recovered and assessed fragments within the growing database. Overall, this macro-level screening technique has added enormous insight to the experiment in unexpected ways.

Description: The statistical debris measurement campaigns conducted by the Haystack Ultrawideband Satellite Imaging Radar (HUSIR) on behalf of the NASA Orbital Debris Program Office are used to characterize the long-term behavior of the small, low Earth orbit (LEO) orbital debris environment. A long-recognized, unique component of the LEO environment is composed of small Sodium-Potassium (NaK) eutectic nuclear reactor coolant droplets associated with the Soviet Radar Ocean Reconnaissance Satellite (RORSAT) program. Beginning with the flight of Cosmos 1176, RORSAT vehicles would nominally separate their reactor core at end of mission, thereby venting the NaK coolant and producing the NaK droplet population. In this paper, we describe the methodology by which NaK are segregated from the statistically sampled general debris population and their sizes inferred; the current NaK environment; how it has changed over time; and a potential new source of NaK: RORSAT vehicles that did not separate their reactor core by either design or apparent malfunction.

Description: The NASA Orbital Debris Program Office has developed the Orbital Debris Engineering Model (ORDEM) primarily as a tool for spacecraft designers and other users to understand the long-term risk of collisions with orbital debris. The newest version, ORDEM 3.1, incorporates the latest and highest fidelity datasets available to build and validate representative orbital debris populations encompassing low Earth orbit (LEO) to geosynchronous orbit (GEO) altitudes for the years 2016-2050. ORDEM 3.1 models fluxes for object sizes 〉 10 m within or transiting LEO and 〉 10 cm in GEO. The deterministic portion of the populations in ORDEM 3.1 is based on the U.S. Space Surveillance Network (SSN) catalog, which provides coverage down to approximately 10 cm in LEO and 1 m in GEO. Observational datasets from radar, in situ, and optical sources provide a foundation from which the model populations are statistically extrapolated to smaller sizes and orbit regions that are not well-covered by the SSN catalog, yet may pose the greatest threat to operational spacecraft. Objects in LEO ranging from approximately 5 mm to 10 cm are modeled using observational data from ground-based radar, namely the Haystack Ultrawideband Satellite Imaging Radar (HUSIR formerly known as Haystack). The LEO population smaller than approximately 3 mm in size is characterized based on a reanalysis of in situ data from impacts to the windows and radiators of the U.S. Space Transportation System orbiter vehicle, i.e., the Space Shuttle. Data from impacts on the Hubble Space Telescope are also used to validate the sub-millimeter model populations in LEO. Debris in GEO with sizes ranging from 10 cm to 1 m is modeled using optical measurement data from the Michigan Orbital DEbris Survey Telescope (MODEST). Specific, major debris-producing events, including the Fengyun-1C, Iridium 33, and Cosmos 2251 debris clouds, and unique populations, such as sodium-potassium droplets, have been re-examined and are modeled and added to the ORDEM environment separately. The debris environment greater than 1 mm is forecast using NASAs LEO-to- GEO ENvironment Debris model (LEGEND). Future explosions of intact objects and collisions involving objects greater than 10 cm are assessed statistically, and the NASA Standard Satellite Breakup Model is used to generate fragments from these events. Fragments smaller than 10 cm are further differentiated based on material density categories, i.e., high-, medium-, and low-density, to better characterize the potential debris risk posed to spacecraft. The future projection of the sub-millimeter environment is computed using a special small-particle degradation model where small particles are created from intact spacecraft and rocket bodies. This work discusses the development, features, and capabilities of the ORDEM 3.1 model; the ne new data analyses used to build the model populations; and sample verification and validation results.

Description: Since 1993, the NASA Orbital Debris Program Office has used the Goldstone Orbital Debris Radar (Goldstone) to sample statistically the orbital debris environment. Due to the sensitivity of this radar, which can detect an approximately 3 mm-diameter conducting sphere at 1,000 km, it has filled an important role in the characterization of the sub-centimeter-sized orbital debris population. Through the years, the capabilities of this system have increased recent updates include increased receiver bandwidth and a change in the bi-static observation geometry both of which enhance the radars ability to estimate orbital parameters. In 2016, dual polarization capability was added, making this the first year where both right- and left-hand circularly polarized information was available from this sensor. This additional polarization information may enable better characterization of sub-centimeter-sized particles in low Earth orbit, particularly since the receiver triggers on reflected energy from both left- and right-handed circular polarizations independently. In this paper, we present measurements and results derived from data taken during the calendar years (CY) 2016-2017 by Goldstone and compare this dataset to measurements taken by the Haystack Ultra-wideband Satellite Imaging Radar (HUSIR) during a similar timeframe.

Description: We examine the diagnostic power of rest-frame ultraviolet (UV) nebular emission lines, and compare them to more commonly used rest-frame optical emission lines, using the test case of a single star-forming knot of the bright lensed galaxy RCSGA 032727132609 at redshift z 1.7. This galaxy has complete coverage of all the major rest-frame UV and optical emission lines from Magellan/MagE and Keck/NIRSPEC. Using the full suite of diagnostic lines, we infer the physical properties: nebular electron temperature (T(sub e)), electron density (n(sub e)), oxygen abundance (log (O/H), ionization parameter [log (q), and interstellar medium (ISM) pressure (log (P/k)]. We examine the effectiveness of the different UV, optical, and joint UVoptical spectra in constraining the physical conditions. Using UV lines alone we can reliably estimate log (q), but the same is difficult for log (O/H). UV lines yield a higher (1.5 dex) log (P/k) than the optical lines, as the former probes a further inner nebular region than the latter. For this comparison, we extend the existing Bayesian inference code IZI, adding to it the capability to infer ISM pressure simultaneously with metallicity and ionization parameter. This work anticipates future rest-frame UV spectral data sets from the James Webb Space Telescope (JWST) at high redshift and from the Extremely Large Telescope (ELT) at moderate redshift.

Description: Transit spectroscopy of terrestrial planets around nearby M dwarfs will be a primary goal of space missions in coming decades. Three-dimensional climate modeling has shown that slow-synchronous rotating terrestrial planets may develop thick clouds at the substellar point, increasing the albedo. For M dwarfs with T(eff)〉3000 K, such planets at the inner habitable zone (IHZ) have been shown to retain moist greenhouse conditions, with enhanced stratospheric water vapor ( fH2O〉10(exp 3)) and low Earth-like surface temperatures. However, M dwarfs also possess strong UV activity, which may effectively photolyze stratospheric H2O. Prior modeling efforts have not included the impact of high stellar UV activity on the H2O. Here, we employ a 1D photochemical model with varied stellar UV, to assess whether H2O destruction driven by high stellar UV would affect its detectability in transmission spectroscopy. Temperature and water vapor profiles are taken from published 3D climate model simulations for an IHZ Earth-sized planet around a 3300 K M dwarf with an N2H2O atmosphere; they serve as self-consistent input profiles for the 1D model. We explore additional chemical complexity within the 1D model by introducing other species into the atmosphere. We find that as long as the atmosphere is well-mixed up to 1 mbar, UV activity appears to not impact detectability of H2O in the transmission spectrum. The strongest H2O features occur in the James Webb Space Telescope MIRI instrument wavelength range and are comparable to the estimated systematic noise floor of 50 ppm.

Description: The paper presents the results from a multi-year effort to develop and validate image processing methods forselecting the best physical models based on solar image observations. The approach consists of selecting the physical models based on their agreement with coronal holes extracted from the images. Ultimately, the goal is to use physical models to predict geomagnetic storms. We decompose the problem into three subproblems: (i) coronal hole segmentation based on physical constraints, (ii) matching clusters of coronal holes between different maps, and (iii) physical map classification. For segmenting coronal holes, we develop a multi-modal method that uses segmentation maps from three different methods to initialize a level-set method that evolves the initial coronal hole segmentation to the magnetic boundary. Then, we introducea new method based on Linear Programming for matchingclusters of coronal holes. The final matching is then performedusing Random Forests. The methods were carefully validatedusing consensus maps derived from multiple readers, manualclustering, manual map classification, and method validation for50 maps. The proposed multi-modal segmentation method significantly outperformed SegNet, U-net, Henney-Harvey, and FCNby providing accurate boundary detection. Overall, the methodgave a 95.5% map classification accuracy.

Description: Space weathering is an important process that affects the surfaces of airless bodies, such as (101955) Bennu. The consequences of this process include physical and chemical changes to materials on the surface, which in turn change spectral characteristics, especially in the visible to near infrared wavelengths. These spectral changes are not the same across airless bodies because the changes are dependent on the composition and mineralogy of the surface and even location within the Solar System. The main space weathering products responsible for these spectral changes are submicroscopic particles, which consist of two types, nanophase and microphase particles, and affect visible to near-infrared reflectance spectra differently. Nanophase particles are particles 〈33 nm in size and occur in agglutinates and within glassy patinas around regolith particles. In contrast, microphase particles are 〉33 nm in size and are present only within agglutinates. These spectral differences are best illustrated by lunar samples. In lunar soils, the nanophase and microphase particles consist of metallic iron. With increasing abundance of nanophase iron particles in a regolith, its spectrum exhibits a lower overall reflectance in the visible to near infrared, weakened absorption bands, and a reddened continuum slope. In contrast, an increasing abundance of microphase iron only causes decreases in reflectance and not reddening. Because of the spectral differences introduced by these two types of particles, it is possible to model the nanophase and microphase particle abundances of a surface through the radiative transfer technique. Beyond the Moon, the composition of the nanophase and microphase particles can include other phases because the mineralogy of the surfaces of other planetary bodies is different. For example, the nanophase and microphase particles may consist of amorphous carbon (Mercury) and sulfides (Itokawa). The mineralogy of Bennu is consistent with carbonaceous chondrites. From a number of space weathering experiments on CM chondrites, the likely nanophase and microphase mineral phases on Bennu includes iron, magnetite, and sulfides (i.e., pentlandite and troilite). The goal of this work is to input the predicted nanophase and microphase compositions for Bennu into the radiative transfer technique. Next, we use this technique to model the OSIRIS-REx Visible Infrared Spectrometer (OVIRS) so that we can model the nanophase and microphase particle abundances across the surface. This will result in space weathering maps of the surface of Bennu, which are useful for understanding the degree of space weathering across the surface and its relationship to various regions and geological features.

Description: The NASA Orbital Debris Program Office has a long-standing optical program begun over three and a half decades ago in 1984, designed to observe the Earth-orbiting environment with optical telescopes. Photometrically calibrated optical data provides a statistical sample for input to NASA models of the debris population for understanding the current and future debris environment around the Earth. Tracked objects and orbits allow for analysis of break-up events. Both known (correlated target in the SSN catalogue, or CT) and unknown (uncorrelated target, or UCT) objects are of interest to better understand how to protect current spacecraft and design more robust future operational satellites, and advise on how policies and practices can lead to protecting the environment itself for future generations. In 2015, a joint NASA JSC Air Force Research Labs (AFRL) project culminated in the installation of the 1.3-meter Eugene Stansbery Meter Class Autonomous Telescope, ES-MCAT (a.k.a. MCAT) on Ascension Island. This DFM Engineering designed telescope provides nearly five-times greater light-collecting power than its predecessor, the 0.6-m MODEST telescope, and faster tracking capabilities by both the telescope and the 7-m ObservaDome. This allows for all orbital regimes to be easily within reach, ranging from low Earth to geosynchronous orbits. Extensive testing and commissioning activities of this custom system led to successfully reaching Initial Operational Capability in 2018, and the facility is currently on track to reach Full Operational Capability. The John Africano Observatory (JAO) comprises the primary 1.3-m ES-MCAT facility, the adjacent tower platform with a 0.4-m telescope, a sophisticated suite of weather instruments, and custom software by Euclid Research for autonomously running the entire system, including monitoring the weather and hardware, tasking all components, and collecting, processing, and analyzing the data. The mission of JAO and MCAT will be discussed, including survey and tracking tasking, a full discussion of data calibration, and both optics and weather-dependent performance.

Description: Accurate forecasting of the arrival time and subsequent geomagnetic impacts of coronal mass ejections (CMEs) at Earth is an important objective for space weather forecasting agencies. Recently, the CME Arrival and Impact working team has made significant progress toward defining communit yagreed metrics and validation methods to assess the current state of CME modeling capabilities. This will allow the community to quantify our current capabilities and track progress in models over time. First, it is crucial that the community focuses on the collection of the necessary metadata for transparency and reproducibility of results. Concerning CME arrival and impact we have identified six different metadata types: 3D CME measurement, model description, model input, CME (non)arrival observation, model output data, and metrics and validation methods. Second, the working team has also identified a validation time period, where all events within the following two periods will be considered: 1 January 2011 to 31 December 2012 and January 2015 to 31 December 2015. Those two periods amount to a total of about 100 hit events at Earth and a large amount of misses. Considering a time period will remove any bias in selecting events and the event set will represent a sample set that will not be biased by user selection. Lastly, we have defined the basic metrics and skill scores that the CME Arrival and Impact working team will focus on.

Description: Spectral studies of the target asteroids of the OSIRIS-REx and Hayabusa2 missions - Bennu and Ryugu - have included comparisons to several samples from the US Antarctic meteorite collection including MET 00639 (CM2), MET 01072 (CM2), ALH 83100 (CM1/2), and LAP 02277 (CM1). The fact that these four samples provide insight into understanding these asteroids leads one to wonder what carbonaceous chondrites (CCs) are represented in the US collection and are there others that might also be helpful for comparison? Here is an overview of the CCs in the collection (n=930) and a demonstration of the great diversity of samples available as a resource to these missions.

Description: No abstract available

Description: Abstract: Turbulence is fundamentally a multiscale phenomena, with energy, mass, and momentum being transported across both spatial and temporal scales. In a magnetized collisionless plasma, there are unresolved questions about the structure of the turbulent transfer of energy, as well as how the energy is extracted from the cascade and dissipated as heat in the constituent charged particles. The plasma in the solar wind acts as an accessible natural laboratory to study these processes, and much progress has indeed been made since the dawn of the space age in understanding turbulence via in situ observations of turbulent plasmas near Earth. However, to date, these observations have been limited to a single, or at best, a tight cluster of points, leading to ambiguities in at what scales energy is contained, how it is transported, and by what mechanism it is dissipated. In this presentation, we describe a heliophysics mission concept aimed at understanding turbulence that is enabled by a swarm of small satellites. The proposed "HelioSwarm" mission will measure turbulent fields and flows and charged particles simultaneously at many points spanning size and time scales from the fluid to sub-ion regime. In doing so, we will be able to disentangle how the turbulence depends on time and space, directly observe the change in internal energy in the plasma, and definitively capture the dynamic relation between turbulence and structures. While the processes under examination are universal, arising throughout our solar system and universe, they are difficult to reproduce in either terrestrial laboratories or numerical simulations, meaning that the only a multipoint observatory in the near-Earth heliosphere will be able to study them in sufficient detail to discern the underlying physics. In this talk, we highlight the enabling role that small satellites play in providing closure on these long-standing but critically important science questions.

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Description: Observations of surviving reentry debris on the ground and research performed by Hyperschall Technologie Gttingen (HTG) [1] indicated that significantly more glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) components survive reentry than current models predict. NASAs Orbital Debris Program Office conducted a series of tests to evaluate the accuracy of material demise models for reentering orbital debris used in NASAs Object Reentry Survival Analysis Tool (ORSAT) and Debris Assessment Software (DAS). Testing is planned in a multi-phase series to allow for quick quantification of results as well as refinement of methods resulting from lessons learned during early phases. The Phase 1 tests discussed here validated ORSAT models for homogeneous metals, provided an efficient quantification of composite material demisability properties like mass loss rate and overall time to demise, and identified potential failure modes, which are currently not well understood. Phase 2 tests will be used to further understand mass loss rates and modes of both thermal and mechanical failure in composite materials. The authors exposed 95 samples of aluminum, CFRP, Kevlar fiber-reinforced polymer, GFRP, and sheets of G10 fiberglass to conditions approximating the reentry environment using an inductively coupled plasma (ICP) torch facility. The cylindrical CFRP samples were exposed to the atmospheric pressure plasma, at both the end and the midpoint, to investigate the difference in demisability between parts with exposed edges, like panels, and parts with no edges, such as carbonoverwrapped pressure vessels (COPVs). In a non-oxidative environment, no composite materials demised within the 5-minute test time. In the oxidative, elevated heat flux environment, CFRP samples demised between 210 s and 270 s. For the first 100 s of insertion time, most of the mass loss was due to pyrolysis of resin, creating an approximately bi-linear mass-loss rate curve with time. In a non-oxidative environment, carbon filaments were observed to unravel from some of the CFRP end-burned samples; however, this effect did not seem to affect the overall time to demise for the samples significantly. These results indicate that both GFRP and CFRP components survive reentry with significantly more remaining mass than current models predict.

Description: No abstract available

Description: The surfaces of airless bodies experience solar wind irradiation and micrometeorite impacts, a process collectively known as space weathering. These mechanisms alter the chemical composition, microstructure, and optical properties of surface materials and considerable work has been done to understand this phenomenon in lunar and ordinary chondritic materials. However, ongoing sample return missions Hayabusa2 to asteroid Ryugu and OSIRIS-REx to asteroid Bennu have prompted the need to study the effects of space weathering on hydrated, organic-rich materials, especially in the context of early results. Understanding space weathering of these samples is critical for properly interpreting remote sensing data during asteroid encounters, for sample site selection, and for the eventual study of returned samples. We can better understand space weathering of carbonaceous materials by simulating these processes in the laboratory. Recent experiments have shown that the changes in spectral characteristics of carbonaceous chondrites are not consistent among experiments, suggesting additional work is needed before these results can inform our understanding of spectral variations on asteroidal surfaces. Similarly, substantial work remains to characterize the chemical and microstructural effects of these processes in order to correlate these features with spectral changes. Here, we build on our previous work, presenting new results of the pulsed laser irradiation of the Murchison (CM2) meteorite to simulate micrometeorite impacts and the progressive space weathering of carbonaceous surfaces.

Description: The Crew Earth Observations (CEO) Facility within the Earth Science and Remote Sensing Unit at NASAs Johnson Space Center supports the acquisition, analysis, and curation of astronaut photography of Earths surface and atmosphere. Astronauts on the International Space Station (ISS) respond to requests from CEO to acquire imagery of scientific and education targets, to include high profile targets in response to activations from the International Charter for Space & Major Disasters (also known as the International Disaster Charter, or IDC) and NASAs Disasters Program. CEO facilitates the acquisition of astronaut photography in response to IDC events and delivers georeferenced data products to the United States Geological Survey (USGS) for distribution to the disaster community. Using GeoRef, an internal web-based tool developed in collaboration with NASAs Ames Research Center, CEO generates data packages of georeferenced imagery, uncertainty images for assessing control and tie point accuracy, and metadata documenting raw and processed data. Operational experience with the Georef software identified vulnerabilities to internal code and server errors that can significantly increase time of data production. As such, CEO developed a backup procedure in case the GeoRef software experiences front-end or back-end errors. A system using OSGEOs open-source QGIS software combined with a semi-automated pipeline using the object-oriented Python language and the Geospatial Abstract Library for generating metadata is quantitatively compared to GeoRefs data package for quality and productivity. Root Mean Square Error (RMSE) provides a standard measurement of data quality as it relates to ground error. Assessing RMSE measurements generated from georeferenced astronaut photographs acquired with different obliquity and focal length offers a comprehensive accuracy assessment of the softwares transformation algorithms. This assessment will indicate the software's ability to produce data products with the least ground-error or highest data quality regarding ground accuracy. In addition, a comparison of the softwares efficiency in generating a data package that includes georeferenced images, metadata, and uncertainty images for measuring tie/ground point error was performed. Initial results, based on the comparison of three nadir-facing astronaut photographs acquired with a 95mm focal length, reveal the QGIS-based system's average RMSE is 2.36 (pixels) suggesting its georectification system produces data products that meet and perhaps improve upon Georef solution's average RMSE of 32.99 (pixels). However, the QGIS system was unable to reproduce two unique Georef data products, uncertainty images for measuring tie and control point errors and a translated unwrapped image. In addition, the Georef software is designed to accept handheld camera pose information from a hardware component (Geosens) scheduled for deployment on the ISS in late 2018; this information is intended to provide increased accuracy and auto-registration capability for astronaut photographs. Future work is expected to determine the QGIS-based georectification systems potential as an open-source alternative (and operational backup) to Georef for georeferencing the full range of resolutions and viewing angles unique to handheld digital camera imagery in support of ISS disaster response activities.

Description: The chemical composition, microstructure, and optical properties of grains on the surfaces of airless bodies are predominantly altered by micrometeorite impacts and solar wind irradiation. These processes drive space weathering and result in the formation of features including chemically-altered, amorphous grain rims, Fe nanoparticles (npFe), and vesiculated grain textures. These characteristics have been identified in returned samples from the surfaces of the Moon and asteroid Itokawa. In order to advance our understanding of the formation of these microstructural and chemical features in returned samples, we have simulated space weathering processes for a variety of materials via laboratory experiments. These experiments include ion irradiation to simulate solar wind exposure and laser irradiation and in situ heating to simulate micrometeorite impacts. While these experiments have provided considerable insight into the formation mechanisms of many space weathering features, they are predominantly static and typically performed separately. Here we present results from the simulated space weathering of olivine grains via He irradiation and dynamic heating, both performed in situ inside the transmission electron microscope (TEM). These experiments allow for the real-time observation of chemical and microstructural changes resulting from the superposed effects of ion irradiation and pulsed heating.

Description: Prior to the return of data from the NASA MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft], information relating to Mercury was limited. From the NASA Mariner 10 flybys, in 1974 and 1975, ~45% of the planet was imaged, its magnetic field was detected, H, He, and O in the exosphere were measured, and other physical characteristics of the planet were determined. Despite these data, much information about Mercury still had to be inferred. It was over 30 years before MESSENGER provided the first in-depth study of the innermost planet. Orbiting Mercury from 2011 to 2015, the MESSENGER spacecraft was able to image the entirety of the planet and thus provide the first global view of Mercury. Coupling multispectral images with data from MESSENGER geochemical instruments, we have developed a better understanding of the geochemical terranes on the planet and the unique nature of Mercurys composition compared to the other terrestrial planets. MESSENGER also provided data that have led to great advancements in understanding the internal structure, exosphere, and magnetosphere of Mercury. The treasure trove of MESSENGER data reveal Mercury as a geochemical end-member among the terrestrial planets. However, we are left with many questions that can only be answered with further exploration.

Description: The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be attributed to varying degrees of aqueous alteration within the parent body asteroid. Previous analyses of soluble organic compounds from four Tagish Lake meteorite specimens (TL5b, TL11h, TL11i, TL11v) identified distinct distributions and isotopic compositions that appeared to be linked to their degree of parent body processing (Herd et al. 2011; Glavin et al. 2012; Hilts et al. 2014). In the present study, we build upon these initial observations and evaluate the molecular distribution of amino acids, aldehydes and ketones, monocarboxylic acids, and aliphatic and aromatic hydrocarbons, including compoundspecific 13C compositions, for three additional Tagish Lake specimens: TL1, TL4, and TL10a. TL1 contains relatively high abundances of soluble organics and appears to be a moderately altered specimen, similar to the previously analyzed TL5b and TL11h lithologies. In contrast, specimens TL4 and TL10a both contain relatively low abundances of all of the soluble organic compound classes measured, similar to TL11i and TL11v. The organicdepleted composition of TL4 appears to have resulted from a relatively low degree of parent body aqueous alteration. In the case of TL10a, some unusual properties (e.g., the lack of detection of intrinsic monocarboxylic acids and aliphatic and aromatic hydrocarbons) suggest that it has experienced extensive alteration and/or a distinct organicdepleted alteration history. Collectively, these varying compositions provide valuable new insights into the relationships between asteroidal aqueous alteration and the synthesis and preservation of soluble organic compounds.

Description: The Sariiek howardite meteorite shower consisting of 343 documented stones occurred on September 2, 2015 in Turkey and is the first documented howardite fall. Cosmogenic isotopes show that Sariiek experienced a complex cosmicray exposure history, exposed during ~1214 Ma in a regolith near the surface of a parent asteroid, and that an ~1 m sized meteoroid was launched by an impact 22 2 Ma ago to Earth (as did onethird of all HED meteorites). SIMS dating of zircon and baddeleyite yielded 4550.4 2.5 Ma and 4553 8.8 Ma crystallization ages for the basaltic magma clasts. The apatite UPb age of 4525 17 Ma, KAr age of ~3.9 Ga, and the U,ThHe ages of 1.8 0.7 and 2.6 0.3 Ga are interpreted to represent thermal metamorphic and impactrelated resetting ages, respectively. Petrographic; geochemical; and O, Cr, and Tiisotopic studies confirm that Sariiek belongs to the normal clan of HED meteorites. Petrographic observations and analysis of organic material indicate a small portion of carbonaceous chondrite material in the Sariiek regolith and organic contamination of the meteorite after a few days on soil. Video observations of the fall show an atmospheric entry at 17.3 0.8 km/s from NW; fragmentations at 37, 33, 31, and 27 km altitude; and provide a preatmospheric orbit that is the first dynamical link between the normal HED meteorite clan and the inner Main Belt. Spectral data indicate the similarity of Sariiek with the Vesta asteroid family (Vclass) spectra, a group of asteroids stretching to delivery resonances, which includes (4) Vesta. Dynamical modeling of meteoroid delivery to Earth shows that the complete disruption of a ~1 km sized Vesta family asteroid or a ~10 km sized impact crater on Vesta is required to provide sufficient meteoroids 4 m in size to account for the influx of meteorites from this HED clan. The 16.7 km diameter Antionia impact crater on Vesta was formed on terrain of the same age as given by the 4He retention age of Sariiek. Lunar scaling for crater production to crater counts of its ejecta blanketshow it was formed ~22 Ma ago.

Description: The Cassini Composite Infrared Spectrometer (CIRS) observed thermal emission in the far- and mid-infrared (from 10 to 1500 cm(exp 1)), enabling spatiotemporal studies of ethane on Titan across the span of the Cassini mission from 2004 through 2017. Many previous measurements of ethane on Titan have relied on modeling the molecules mid-infrared (sub 12) band, centered on 822 cm(exp 1). Other bands of ethane at shorter and longer wavelengths were seen, but have not been modeled to measure ethane abundance. Spectral line lists of the far-infrared (sub 4) torsional band at 289 cm(exp 1) and the mid-infrared (sub 8) band centered at 1468 cm(exp 1) have recently been studied in the laboratory. We model CIRS observations of each of these bands (along with the (sub 12) band) separately and compare the retrieved mixing ratios from each spectral region. Nadir observations of the (sub 4) band probe the low stratosphere below 100 km. Our equatorial measurements at 289 cm(exp 1) show an abundance of (1.00.4)x10(exp 5) at 88 km from 2007 to 2017. This mixing ratio is consistent with measurements at higher altitudes, in contrast to the depletion that many photochemical models predict. Measurements from the (sub 12) and (sub 8) bands are comparable to each other, with the (sub 12) band probing an altitude range that extends deeper in the atmosphere. We suggest that future studies of planetary atmospheres may observe the (sub 8) band, enabling shorter wavelength studies of ethane. There may also be an advantage to observing both the ethane (sub 8) band and nearby methane (sub 4) band in the same spectral window.

Description: Parametric cost models can be used by designers and project managers to compare cost between major architectural cost drivers and allow high-level design trades; enable cost-benefit analysis for technology development investment; and, provide a basis for estimating total project cost between related concepts. The NASA Marshall Space Flight Center has developed a 5- parameter cost model that explains 93% (Adjusted R2) of the cost variation in a database of 46 total ground and space telescope assemblies. This model can be used to estimate the most probably cost for the Habitable Exoplanet Telescope Assembly.

Description: Carbonaceous chondrites represent roughly 4% of all meteorite falls on Earth.1 Some of these carbon-rich meteorites (up to 3 wt % of carbon) contain a diverse suite of organic compounds that hold a record of the chemical inventory and processes that occurred in the early Solar System and through parent body processing. Most of the organic carbon in carbonaceous meteorites is in the form of insoluble organic matter (IOM), while the rest is composed of a complex mixture of soluble organic compounds, including aliphatic amino acids, which are the most extensively studied types of meteoritic organics. More than 90 dierent amino acids, which represent a nearly complete structural diversity, have been identied from carbonaceous chondrites. The diversity of organics provides insight into the chemical nature of the meteorite parent bodies,24 however although meteoritic amino acids have been studied for over 60 years using a variety of techniques,510 their synthetic origins remain a subject of debate.11 Accurately measuring the molecular distributions of organic compounds and comparing the relative abundances of dierent compound types is key for understanding the eects of aqueous and thermal processing inside the parent body and the synthetic relationships between various classes of meteoritic organic compounds. Although aldehydes and ketones (collectively called "carbonyl compounds") have been previously reported from carbonaceous chondrites,1217 and their potential synthetic relation to other organic compounds

Description: Space-based astrophysical and remote sensing observations often require the detection and measurement of light originating from distant and relatively faint objects. These observations are highly susceptible to scattered light which may introduce imaging artifacts, obscure object details, and increase measurement noise. This paper describes the initial work of characterizing representative black materials used in coronagraph instruments and other spaceborne instruments. Measurements of blackness and the achieved reflectance of black silicon are provided in the spectral range from 400nm to 2500nm using 8o directional hemispherical measurements. The bidirectional reflectance of black silicon was also measured at discrete wavelengths, 633nm, and 1064nm, using the optical scatterometer located at NASA Goddard Space Flight Centers Diffuser Calibration Laboratory (DCL). A 100mm diameter black silicon sample was fabricated and optically characterized. The BRDF of other well-known black materials such as Z306 and Fractal Black are also presented and discussed.

Description: Results are presented for the reflectivity of spray on foam insulation (SOFI) samples coated with a new high solar reflectivity coating. Reflectance spectra are presented comparing bare SOFI to samples with one, two, or three layers of the new coating as well as one sample with white paint. Samples were coated on the front side of the SOFI, where the surface height varies significantly, as well as on the flatter back surface. Predicted solar absorbance values are provided for a few select cases.

Description: No abstract available

Description: The 2019 Center Innovation Fund Annual Report contains FY18 completed reports. Attached is the executive summary/abstract section of the reports.

Description: No abstract available

Description: No abstract available

Description: We report on progress in the search for signs of space weathering on Bennu. We provide an overview of the space weathering evidence to date, and summarize relevant findings from several ongoing parallel studies of surface processes and surface properties. We examine trends from these studies in the context of space weathering, and what is known about near-Earth asteroid surface maturation. Because Bennu is covered with blocks, boulders, and rocks of various sizes, our search for space weathering signals has inevitably led to a study of the properties of Bennus rocks. Our research question is do Bennus bright and dark rock populations form a maturity continuum due to space weathering, or alternatively, do the bright and dark rocks provide compelling evidence for two distinct rock populations on Bennu? In particular, we present our best estimate of the sub-field-of-view OVIRS (OSIRIS-REx Visible and Infrared Spectrometer) spectral properties of the largest bright boulders and compare them with the darker materials on Bennus surface to see if the observed spectral and albedo differences are consistent with space weathering effects, or not.

Description: Spatially-resolved observations from the IRIS and SDO/AIA satellites, especially when coupled with realistic 3D RMHD simulations, are a powerful tool for analysis of processes in the solar chromosphere, transition region, and corona. However, the complexity of the data makes understanding the observations and modeling results difficult. In this work, we apply unsupervised clustering algorithms for analysis of observational and synthetic chromospheric Mg II h&k 2796&2803 and transition region C II 1334&1335 line profiles observed by IRIS, and extreme ultraviolet (EUV) emission observed by SDO/AIA, for various types of problems. The synthetic line profiles are computed for simulations of the quiescent solar atmosphere (using the StellarBox and RH1.5 codes). The K-Means clustering algorithm is applied, and the selection of an optimal number of clusters is supported by the average silhouette width technique. We discuss applications of the line profile clustering method to 1) visualization of computational and observational spectroscopic imaging data; 2) understanding of evolutionary trends and behavior patterns of quiet Sun emission and during solar flares; and 3) recognition of heating events and shock waves.

Description: The Community Coordinated Modeling Center has been leading communitywide space science and space weather model validation projects for many years. These efforts have been broadened and extended via the newly launched International Forum for Space Weather Modeling Capabilities Assessment (https://ccmc.gsfc.nasa.gov/assessment/). Its objective is to track space weather models' progress and performance over time, a capability that is critically needed in space weather operations and different user communities in general. The Space Radiation and Plasma Effects Working Team of the afore mentioned International Forum works on one of the many focused evaluation topics and deals with five different subtopics (https://ccmc.gsfc.nasa.gov/assessment/topics/radiationall.php) and varieties of particle populations: Surface Charging from tens of eV to 50keV electrons and internal charging due to energetic electrons from hundreds keV to several MeVs. Single event effects from solar energetic particles and galactic cosmic rays (several MeV to TeV), total dose due to accumulation of doses from electrons (〉100 keV) and protons (〉1 MeV) in a broad energy range, and radiation effects from solar energetic particles and galactic cosmic rays at aviation altitudes. A unique aspect of the Space Radiation and Plasma Effects focus area is that it bridges the space environments, engineering, and user communities. The intent of the paper is to provide an overview of the current status and to suggest a guide for how to best validate space environment models for operational/engineering use, which includes selection of essential space environment and effect quantities and appropriate metrics.

Description: We examine the role that ions and electrons play in reconnection using observations from the Magnetospheric Multiscale (MMS) mission on kinetic ion and electron scales, which are much shorter than magnetohydrodynamic scales. This study reports observations with unprecedented high resolution that MMS provides for magnetic eld (7.8 ms) and plasma (30 ms for electrons and 150 ms for ions). We analyze and compare approaches to the magnetopause in 2016 November, to the electron diffusion region in the magnetotail in 2017 July followed by a current sheet crossing in 2018 July. Besides magnetic eld reversals, changes in the direction of the ow velocity, and ion and electron heating, MMS observed large uctuations in the electron ow speeds in the magnetotail. As expected from numerical simulations, we have veried that when the eld lines and plasma become decoupled a large reconnecting electric eld related to the Hall current (110 mV/m) is responsible for fast reconnection in the ion diffusion region. Although inertial accelerating forces remain moderate (12 mV/m), the electric elds resulting from the divergence of the full electron pressure tensor provide the main contribution to the generalized Ohms law at the neutral sheet (as large as 200 mV/m). In our view, this illustrates that when ions decouple electron physics dominates. The results obtained on kinetic scales may be useful for better understanding the physical mechanisms governing reconnection processes in various magnetized laboratory and space plasmas.

Description: No abstract available

Description: The NASA Solar System Exploration Research Virtual Institute (SSERVI) is a virtual institute focused on research at the intersection of science and human exploration, training the next generation of exploration scientists, and developing the broad scientific and technical community. Part of SSERVIs mission is to act as a hub for opportunities that engage the larger scientific and exploration communities in order to form new interdisciplinary, research-focused collaborations. This talk will describe the research efforts of the SSERVI domestic teams that constitute the U.S. complement of the Institute and how the Institute engages the community through workshops, conferences, online seminars and classes, student exchange programs and internships. In addition, this talk will discuss SSERVIs current international partnerships, a key part of its global mission.

Description: A HgCdTe avalanche photodiode (APD) focal plane array assembly with linear mode photon-counting capability has been developed for space lidar applications. An integrated detector cooler assembly (IDCA) has been built using a miniature Stirling cooler. A microlens array has been included to improve the fill factor. The HgCdTe APD has a spectral response from 0.9- to 4.3-m wavelengths, a photon detection efficiency as high as 70%, and a dark count rate of 〈250 kHz at 110 K. The mass of the IDCA is 0.8 kg and the total electrical power consumption is about 7 W. The HgCdTe APD arrays have been characterized at NASA Goddard Space Flight Center. A series of environmental tests have been conducted for the IDCAs, including vibration, thermal cycling, and thermal vacuum tests. A description of the device and the test results at NASA are given in this paper.

Description: High-resolution infrared spectra of Jupiter-family comet 45P/Honda-Mrkos-Pajdukov were obtained with NIRSPEC at the W. M. Keck Observatory on two post- perihelion dates (UT 2017 February 13 and 19), when the comet was at heliocentric distances of 1.01 and 1.10 AU, respectively. On UT February 13, H2O was measured simultaneously with six trace parent molecules: CH3OH, C2H6, HCN, NH3, C2H2, and H2CO. On UT February 19, CH4 and CO were also targeted in addition to the species measured on UT February 13. Abundances of CO, CH4, and C2H2 relative to H2O are consistent with values obtained from IRTF/iSHELL observations of 45P in early January 2017 just after perihelion when the heliocentric distance was 0.550.56 AU. Differences are seen in H2CO/H2O, C2H6/H2O, CH3OH/H2O, and HCN/H2O in February compared to January. Additionally, NH3 abundances appear highly variable during the February measurements, suggesting possible fluctuations of a factor of ten; however, there is significant uncertainty in quantifying NH3 owing to the marginal detections of only one or two lines on each of the two dates. Combining all infrared spectroscopic observations of 45P in January and February 2017, a post-perihelion relationship of Q(H2O) = (2.81 0.25) 10(exp 27) [R(sub h) (sup 3.83 0.18)] molecules/s is derived. However, all measurements suggest significant variability in H O production on timescales of hours and days. Compared to other comets, volatile abundances relative to H2O in 45P are as follows: CO (depleted relative to all measured comets), CH3OH (enriched/all comets), CH4 and C2H6 (typical/all comets, enriched/Jupiter-family comets), C2H2 (depleted/all comets, typical/Jupiter-family comets), H2CO (January: typical, February depleted/all comets), HCN (January: severely depleted, February: typical/Jupiter-family comets). The small geocentric distances of the comet in February 2017 provide high spatial resolution in the coma of 45P (~12 and 19 km/pixel on February 13 and 19, respectively). Overall, the spatial distributions of volatiles and dust suggest a relatively symmetric and uniform coma during the UT February 13 and 19 observations, with small spatial differences noted between some volatile species. Measured C2H2 and HCN abundances are consistent with HCN as the primary parent of CN and C2H2 as a significant but not primary parent for C2, based on C2 and CN 2017 and previous apparitions. Extracted spectra show an increase in the dust-to-gas ratio in 45P from February 13 to 19 in agreement with contemporaneous narrowband optical measurements.

Description: Observations from the Kepler mission have revealed frequent superares on young and active solar-like stars. Superares result from the large-scale restructuring of stellar magnetic elds, and are associated with the eruption of coronal material (a coronal mass ejection, or CME) and energy release that can be orders of magnitude greater than those observed in the largest solar ares. These catastrophic events, if frequent, can signicantly impact the potential habitability of terrestrial exoplanets through atmospheric erosion or intense radiation exposure at the surface. We present results from numerical modeling designed to understand how an eruptive superare from a young solar-type star, (exp 1)Cet, could occur and would impact its astrospheric environment. Our data-inspired, three- dimensional magnetohydrodynamic modeling shows that global-scale shear concentrated near the radial-eld polarity inversion line can energize the closed-eld stellar corona sufciently to power a global, eruptive superare that releases approximately the same energy as the extreme 1859 Carrington event from the Sun. We examine proxy measures of synthetic emission during the are and estimate the observational signatures of our CME-driven shock, both of which could have extreme space-weather impacts on the habitability of any Earth-like exoplanets. We also speculate that the observed 1986 Robinson-Bopp superare from (exp 1)Cet was perhaps as extreme for that star as the Carrington are was for the Sun.

Description: The most important parameter in the coupling between solar wind and geomagnetic activity is the B(sub z)component of the interplanetary magnetic field (IMF). However, recent studies have shown that IMF B(sub y) is an additional, independent driver of geomagnetic activity. We use here local geomagnetic indices from a large network of magnetic stations to study how IMF B(sub y) affects geomagnetic activity at different latitudes for all solar wind and, separately, during coronal mass ejections. We show that geomagnetic activity, for all solar wind, is 20% stronger for B(sub y) 〉 0 than for B(sub y) 〈 0 at subauroral latitudes of about 60 corrected geomagnetic latitude. During coronal mass ejections, the B(sub y)effect is larger, about 40%, at slightly lower latitudes of about 57 (corrected geomagnetic) latitude. These results highlight the importance of the IMF B(sub y)component for space weather at different latitudes and must be taken into account in space weather modeling

Description: This concept is based on the Skylab II concept, which proposes using a SLS propellant tank as the primary structure of a habitat. Common Habitat takes this a step further, proposing an interior architecture that is equally viable as a lunar surface hab, transit hab, and Mars surface hab, thus enabling a single development to support all three long duration habitat roles. Common Habitat has been pursued by the PI and co-investigators at MSFC and other centers in a spare time / funding available basis, often with heavy student intern support. Student resources have developed preliminary concepts, but these models must be refined to reflect accurate vehicle subsystems, utilities, stowage, workstations, and other crew systems. This investigation applies NASA civil servant and contractor expertise to correct errors in the most recent student concepts in order to prepare them for future human-in-the-loop evaluations to determine the most viable configuration for a Common Habitat. In prior studies there was never an opportunity to trade both crew size and internal orientation. Prior work has been a series of point designs with inconsistent design constraints, making apples to apples comparisons impossible. The most recent student work produced CAD models of four habitat variants for future use in a trade study, but the student products contain model construction and geometry errors, inaccurate subsystems design and placement, and unrealistic structural elements and outfitting. These must be corrected before the models can be moved into a VR environment for humanin- the-loop testing. Through consultation with SMEs throughout the Agency, the fidelity of these designs will be upgraded to a level of quality sufficient to make a comparative analysis of crew size sensitivity and internal orientation. The product of this activity is four upgraded CAD models, each reflecting a different configuration of the Common Habitat. One is a horizontal configuration using the full length of the SLS LOX tank. One is a vertical configuration using the same tank dimensions. The third is a horizontal configuration using a truncated SLS LOX tank (half the barrel length). The fourth is a vertical configuration of the half-length SLS LOX tank.

Description: The Large and Small Magellanic Clouds (LMC and SMC), gas-rich dwarf companions of the Milky Way, are the nearest laboratories for detailed studies on the formation and survival of complex organic molecules (COMs) under metal-poor conditions. To date, only methanol, methyl formate, and dimethyl ether have been detected in these galaxiesall three toward two hot cores in the N113 star-forming region in the LMC, the only extragalactic sources exhibiting complex hot-core chemistry. We describe a small and diverse sample of the LMC and SMC sources associated with COMs or hot-core chemistry, and compare the observations to theoretical model predictions. Theoretical models accounting for the physical conditions and metallicity of hot molecular cores in the Magellanic Clouds have been able to broadly account for the existing observations, but they fail to reproduce the dimethyl ether abundance by more than an order of magnitude. We discuss future prospects for research in the eld of complex chemistry in the low- metallicity environment. The detection of COMs in the Magellanic Clouds has important implications for astrobiology. The metallicity of the Magellanic Clouds is similar to that of galaxies in the earlier epochs of the universe; thus, the presence of COMs in the LMC and SMC indicates that a similar prebiotic chemistry leading to the emergence of life, as it happened on Earth, is possible in low-metallicity systems in the earlier universe.

Description: Space-based astrophysical and remote sensing observations often require the detection and measurement of light originating from distant and relatively faint objects. These observations are highly susceptible to scattered light which may introduce imaging artifacts, obscure object details, and increase measurement noise. This paper describes the initial work of characterizing representative black materials used in coronagraph instruments and other spaceborne instruments. Measurements of blackness and the achieved reflectance of black silicon are provided in the spectral range from 400nm to 2500nm using 8o directional hemispherical measurements. The bidirectional reflectance of black silicon was also measured at discrete wavelengths, 633nm, and 1064nm, using the optical scatterometer located at NASA Goddard Space Flight Centers Diffuser Calibration Laboratory (DCL). A 100mm diameter black silicon sample was fabricated and optically characterized. The BRDF of other well-known black materials such as Z306 and Fractal Black are also presented and discussed.

Description: The SPLICE project is continuing NASA's efforts to develop precision landing GN&C technologies for future lander missions. One of those technologies is the next generation Hazard Detection System (HDS), which consists of a new Hazard Detection LIDAR and Hazard Detection Algorithms. The HDS is a modular system that will be adapted to fit specific mission needs in the future. This abstract presents the design approach and current challenges for the SPLICE HDS.

Description: Expected to launch in 2021 Spring, the Imaging X-ray Polarimetry Explorer (IXPE) is a NASA Astrophysics Small Explorer Mission with significant contributions from the Italian space agency (ASI). The IXPE observatory features three identical x-ray telescopes, each comprised of a 4-m-focal-length mirror module assembly (MMA, provided by NASA Marshall Space Flight Center) that focuses x rays onto a polarization-sensitive, imaging detector (contributed by ASI-funded institutions). This paper summarizes the MMAs design, fabrication, alignment and assembly, expected performance, and calibration plans.

Description: In NASAs Object Reentry Survival Analysis Tool (ORSAT), aerodynamic drag and aerothermal heating coefficients are computed for each of the free-molecular, continuum, and transitional flow regimes using analytical and semi-analytical methods. These methods are typically limited to convex, blunt objects (such as spheres) and are applied to other objects such as boxes and cylinders using multiplicative shape factors to account for the different behavior. Previous literature has analyzed the aerodynamic and aerothermodynamic properties of flow around sharp-edged objects like boxes and cylinders in transitional flow, though only those objects with solid external boundaries. However, many reentry objects we have encountered in real spacecraft have been hollow (i.e., with the potential to allow flow through them). We present here preliminary results from analyses performed using the NASA Direct Simulation Monte Carlo (DSMC) Analysis Code (DAC) on hollow cylinders and boxes (with varying wall thickness-diameter ratio).

Description: Author(s): Julien Garaud, Alberto Corticelli, Mihail Silaev, and Egor Babaev Disorder in two-band superconductors with repulsive interband interaction induces a frustrated competition between the phase-locking preferences of the various potential and kinetic terms. This frustrated interaction can result in the formation of an s + i s superconducting state that breaks the time-r... [Phys. Rev. B 98, 014520] Published Wed Jul 25, 2018

Description: Author(s): K. Rostem, P. J. de Visser, and E. J. Wollack When quasiparticles in a BCS superconductor recombine into Cooper pairs, phonons are emitted within a narrow band of energies above the pairing energy at 2 Δ . We show that a phonon band gap restricting the escape of recombination phonons from a superconductor can increase the quasiparticle recombinat... [Phys. Rev. B 98, 014522] Published Fri Jul 27, 2018

Description: Author(s): Shota Kanasugi and Youichi Yanase Motivated by recent studies on ferroelectriclike order coexisting with metallicity, we investigate ferroelectric (FE) superconductivity in which a FE-like structural phase transition occurs in the superconducting state. We consider a two-dimensional s -wave superconductor with Rashba-type antisymmetr... [Phys. Rev. B 98, 024521] Published Fri Jul 27, 2018

Description: Author(s): T. J. Volkoff and Yongkyung Kwon Under the assumption of two-fluid kinematics of a nonrelativistic Bose liquid in the presence of a local velocity field v ( x ) , local Galilei transformations are used to derive formulas for the spatial distribution of superfluidity. The local formulation is shown to subsume several descriptions of sup... [Phys. Rev. B 98, 014519] Published Wed Jul 25, 2018

Description: Author(s): F. Weber, D. Parshall, L. Pintschovius, J.-P. Castellan, M. Kauth, M. Merz, Th. Wolf, M. Schütt, J. Schmalian, R. M. Fernandes, and D. Reznik Nematicity is ubiquitous in electronic phases of high- T c superconductors, particularly in the Fe-based systems. While several experiments have probed nematic fluctuations, they have been restricted to uniform or momentum-averaged fluctuations. Here, we investigate the behavior of finite-momentum nem... [Phys. Rev. B 98, 014516] Published Tue Jul 24, 2018

Description: Author(s): Tao Zhou, Yi Gao, and Z. D. Wang We study theoretically single-particle spectra of Weyl superconductors. Three different superconducting pairing states are addressed, which are the BCS-type states with the s -wave pairing symmetry and the p + i p -wave pairing symmetry, and the FFLO pairing state. We elaborate that these three states ca... [Phys. Rev. B 98, 024515] Published Tue Jul 24, 2018

Description: Author(s): S. J. Zhang, Z. X. Wang, L. Y. Shi, T. Lin, M. Y. Zhang, G. D. Gu, T. Dong, and N. L. Wang We report near and midinfrared pump, c -axis terahertz probe measurements on a superconducting single crystal La 1.905 Ba 0.095 CuO 4 with T c = 32  K. The measurements reveal that the pump-induced change occurs predominantly at the Josephson plasma edge position below T c . Upon excitation by strong near-infra... [Phys. Rev. B 98, 020506(R)] Published Tue Jul 24, 2018

Description: Author(s): Philipp Materne, Wenli Bi, Esen Ercan Alp, Jiyong Zhao, Michael Yu Hu, Anton Jesche, Christoph Geibel, Rhea Kappenberger, Saicharan Aswartham, Sabine Wurmehl, Bernd Büchner, Dongzhou Zhang, Til Goltz, Johannes Spehling, and Hans-Henning Klauss We present a detailed investigation of the electronic properties of CeFeAsO under in-plane chemical (As by P substitution) and hydrostatic pressure by means of in-house and synchrotron Mössbauer spectroscopy. The Fe magnetism is suppressed due to both pressures and no magnetic order was observed abo... [Phys. Rev. B 98, 014517] Published Tue Jul 24, 2018

Description: Author(s): Maxim Dzero and Alex Levchenko Motivated by the recent experimentally observed manifestations of the quantum critical point fluctuations in the thermodynamic properties of multiband superconductors, we derive a general expression for the Josephson current of various junctions between two superconductors in the phase of supercondu... [Phys. Rev. B 98, 054501] Published Mon Aug 06, 2018

Description: Author(s): Rustem Khasanov, Rafael M. Fernandes, Gediminas Simutis, Zurab Guguchia, Alex Amato, Hubertus Luetkens, Elvezio Morenzoni, Xiaoli Dong, Fang Zhou, and Zhongxian Zhao Magnetism induced by external pressure ( p ) was studied in a FeSe crystal sample by means of muon-spin rotation. The magnetic transition changes from second order to first order for pressures exceeding the critical value p c ≃ 2.4 – 2.5  GPa. The magnetic ordering temperature ( T N ) and the value of the magn... [Phys. Rev. B 97, 224510] Published Wed Jun 13, 2018

Description: Author(s): Kukka-Emilia Huhtinen, Marek Tylutki, Pramod Kumar, Tuomas I. Vanhala, Sebastiano Peotta, and Päivi Törmä We study the attractive Hubbard model with spin imbalance on two lattices featuring a flat band: the Lieb and kagome lattices. We present mean-field phase diagrams featuring exotic superfluid phases, similar to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, whose stability is confirmed by dynami... [Phys. Rev. B 97, 214503] Published Tue Jun 05, 2018

Description: Author(s): Chun-Xiao Liu, Jay D. Sau, and S. Das Sarma Trivial Andreev bound states arising from chemical-potential variations could lead to zero-bias tunneling conductance peaks at finite magnetic field in class-D nanowires, precisely mimicking the predicted zero-bias conductance peaks arising from the topological Majorana bound states. This finding ra... [Phys. Rev. B 97, 214502] Published Tue Jun 05, 2018

Description: Author(s): Marcin Matusiak, Krzysztof Rogacki, and Thomas Wolf Nematicity turns out to be a surprisingly common form of self-organization in strongly correlated electronic systems. Its presence along with superconductivity raises the question about a mutual relation between these two types of electronic order as well as about mechanisms that leads to their formation. Here, the authors show that the in-plane anisotropy of the Nernst effect (Δ ν / T ) in detwinned Ba(Fe 1 − x Co x ) 2 As 2 single crystals emerges at a temperature much higher than the temperature of the magnetic transition (TSDW). Furthermore, the temperature dependence of Δ ν / T retains its exponential character below and above TSDW, which suggests that the origin of nematicity might be something different from magnetic. [Phys. Rev. B 97, 220501(R)] Published Tue Jun 05, 2018

Description: Author(s): Kejing Ran, Ruidan Zhong, Tong Chen, Yuan Gan, Jinghui Wang, B. L. Winn, A. D. Christianson, Shichao Li, Zhen Ma, Song Bao, Zhengwei Cai, Guangyong Xu, J. M. Tranquada, Genda Gu, Jian Sun, and Jinsheng Wen We present inelastic neutron scattering results of phonons in ( Pb 0.5 Sn 0.5 ) 1 − x In x Te powders, with x = 0 and 0.3. The x = 0 sample is a topological crystalline insulator, and the x = 0.3 sample is a superconductor with a bulk superconducting transition temperature T c of 4.7 K. In both samples, we observe un... [Phys. Rev. B 97, 220502(R)] Published Fri Jun 15, 2018

Description: Author(s): Abduweli Ablimit, Yun-Lei Sun, Hao Jiang, Si-Qi Wu, Ya-Bin Liu, and Guang-Han Cao We report the synthesis, crystal structure, physical properties, and first-principles calculations of a vanadium-based oxytelluride Rb 1 − δ V 2 Te 2 O ( δ ≈ 0.2 ). The crystal structure bears two-dimensional V 2 O square nets sandwiched with tellurium layers, mimicking the structural motifs of cuprate and iron-b... [Phys. Rev. B 97, 214517] Published Wed Jun 20, 2018

Description: Author(s): Liran Wang, Mingquan He, Frédéric Hardy, Peter Adelmann, Thomas Wolf, Michael Merz, Peter Schweiss, and Christoph Meingast The nematic susceptibility of Ba 1 − x Na x Fe 2 As 2 single crystals is studied by measuring the Young's modulus using a three-point-bending setup in a capacitance dilatometer over a wide doping range. Particular emphasis is placed on the behavior within the double- Q antiferromagnetic C 4 re-entrant phase. H... [Phys. Rev. B 97, 224518] Published Fri Jun 22, 2018

Description: Author(s): Sourav Biswas, Clemens B. Winkelmann, Hervé Courtois, and Anjan K. Gupta Micron-sized superconducting interference devices ( μ -SQUIDs) based on constrictions optimized for minimizing thermal runaway are shown to exhibit voltage oscillations with applied magnetic flux despite their hysteretic behavior. We explain this remarkable feature by a significant supercurrent contri... [Phys. Rev. B 98, 174514] Published Tue Nov 27, 2018

Description: Author(s): A. V. Lebedev, G. B. Lesovik, V. M. Vinokur, and G. Blatter A quantum Maxwell demon is a device that can lower the entropy of a quantum system by providing it with purity. The functionality of such a quantum demon is rooted in a quantum-mechanical SWAP operation exchanging mixed and pure states. We describe the setup and performance of a quantum Maxwell demo... [Phys. Rev. B 98, 214502] Published Tue Dec 04, 2018

Description: Author(s): Jonatan Wårdh, Brian M. Andersen, and Mats Granath We derive the effective Ginzburg-Landau (GL) theory for finite-momentum [Fulde-Ferrell-Larkin-Ovchinnikov/pair-density wave (FFLO/PDW)] superconductivity without spin population imbalance from a model with local attraction and repulsive pair hopping. We find that the GL free energy must include up t... [Phys. Rev. B 98, 224501] Published Tue Dec 04, 2018

Description: Author(s): Yahya Alavirad, Junhyun Lee, Ze-Xun Lin, and Jay D. Sau We use an effective model to calculate properties of the supercurrent carried by chiral edge states of a quantum Hall weak link. This “chiral” supercurrent is qualitatively distinct from the usual Josephson supercurrent in that it cannot be mediated by a single edge alone, i.e., both right- and left... [Phys. Rev. B 98, 214504] Published Thu Dec 06, 2018

Description: Author(s): Teemu J. Peltonen, Risto Ojajärvi, and Tero T. Heikkilä Recent experiments show how a bilayer graphene twisted around a certain magic angle becomes superconducting as it is doped into a region with approximate flat bands. We investigate the mean-field s -wave superconducting state in such a system and show how the state evolves as the twist angle is tuned... [Phys. Rev. B 98, 220504(R)] Published Mon Dec 10, 2018

Description: Author(s): Tarapada Sarkar, Richard L. Greene, and S. Das Sarma We present experimental results for the in-plane resistivity of the electron-doped cuprate superconductor L a 2 − x C e x Cu O 4 above its transition temperature T c as a function of Ce doping x and temperature. For the doping x between 0.11 and 0.17, where T c varies from 30 K ( x = 0.11 ) to 5 K ( x = 0.17 ), we find... [Phys. Rev. B 98, 224503] Published Mon Dec 10, 2018

Description: Author(s): Li Xiang, Raquel A. Ribeiro, Udhara S. Kaluarachchi, Elena Gati, Manh Cuong Nguyen, Cai-Zhuang Wang, Kai-Ming Ho, Sergey L. Bud'ko, and Paul C. Canfield Measurements of temperature-dependent resistance and magnetization under hydrostatic pressures up to 2.13 GPa are reported for single-crystalline, superconducting BaBi 3 . A temperature-pressure phase diagram is determined and the results suggest three different superconducting phases α , β , and γ in t... [Phys. Rev. B 98, 214509] Published Thu Dec 13, 2018

Description: Author(s): R. J. Sun, Y. Quan, S. F. Jin, Q. Z. Huang, H. Wu, L. Zhao, L. Gu, Z. P. Yin, and X. L. Chen Iron selenide superconductors exhibit unique characteristics distinct from iron pnictides, especially in the electron-doped region. Here, the authors report the synthesis of a new family of Li x (C 3 N 2 H 10 ) 0 . 37 FeSe materials, which features a continuous superconducting dome harboring a Lifshitz transition within the wide range of 0.06 ≤ x ≤ 0.68. Under electron doping, the anion height of FeSe layers deviates linearly away from the optimized values of pnictides. This feature leads to a new superconducting zone with unique electronic structures and strong orbital-selective electronic correlation. [Phys. Rev. B 98, 214508] Published Wed Dec 12, 2018

Description: Author(s): Bao-Tian Wang, Peng-Fei Liu, Jing-Jing Zheng, Wen Yin, and Fangwei Wang Layered 1 T − TiSe 2 has attracted much interest for the competition of charge density wave (CDW) and superconductivity in its bulk and even monolayer forms. Here we perform first-principles calculations of the electronic structure, phonon dispersion, and electron-phonon coupling of the Pb-intercalated ... [Phys. Rev. B 98, 014514] Published Tue Jul 24, 2018

Description: Author(s): Quan Zhuang, Xilian Jin, Tian Cui, Die Zhang, Ying Li, Xin Li, Kuo Bao, and Bingbing Liu For exploring the superconductivity mechanisms and seeking potential high-temperature superconductors in hydrogen-rich compounds, we perform a systematical investigation of the phase diagram, crystal structures, electronic properties, and electron-phonon coupling (EPC) of titanium hydrides under hig... [Phys. Rev. B 98, 024514] Published Tue Jul 24, 2018

Description: Author(s): K. H. A. Villegas, V. M. Kovalev, F. V. Kusmartsev, and I. G. Savenko We propose an effective optical approach to monitor superconductors in a two-layer superconductor-normal metal structure. Effectively, such a hybrid system represents a resonator, where electrons are strongly coupled with light. We show that the interaction of light with the superconductor is strong... [Phys. Rev. B 98, 064502] Published Tue Aug 07, 2018

Description: Author(s): Yue Sun, Shunichiro Kittaka, Shota Nakamura, Toshiro Sakakibara, Peng Zhang, Shik Shin, Koki Irie, Takuya Nomoto, Kazushige Machida, Jingting Chen, and Tsuyoshi Tamegai We investigate the band structure, nematic state, and superconducting gap structure of two selected FeSe single crystals containing different amounts of disorder. Transport and angle-resolved photoemission spectroscopy measurements show that the small amount of disorder has little effect on the band... [Phys. Rev. B 98, 064505] Published Mon Aug 13, 2018

Description: Author(s): A. G. Mal'shukov The Ruderman-Kittel-Kasuya-Yosida interaction of magnetic impurities in a superconductor exponentially decreases when the distance r between them is larger than the superconductor's coherence length because this interaction is mediated by quasiparticles, which have a gap in their energy spectra. At ... [Phys. Rev. B 98, 054504] Published Mon Aug 13, 2018

Description: Author(s): Chien-Te Wu, F. Setiawan, Brandon M. Anderson, Wei-Han Hsiao, and K. Levin We study fermion-parity-changing quantum phase transitions (QPTs) in platform Josephson junctions. These QPTs, associated with zero-energy bound states, are rather widely observed experimentally. They emerge from numerical calculations frequently without detailed microscopic insight. Importantly, th... [Phys. Rev. B 98, 064504] Published Mon Aug 13, 2018

Description: Author(s): R. B. Adhikari, D. L. Kunwar, I. Jeon, M. B. Maple, M. Dzero, and C. C. Almasan Motivated by current research efforts toward exploring the interplay between magnetism and superconductivity in multiband electronic systems, we have investigated the effects of Eu substitution through thermodynamic measurements on the superconducting filled skutterudite alloys Pr 1 − x Eu x Pt 4 Ge 12 . An i... [Phys. Rev. B 98, 064506] Published Mon Aug 13, 2018

Description: Author(s): Yu Song, Guotai Tan, Chenglin Zhang, Rasmus Toft-Petersen, Rong Yu, and Pengcheng Dai We use inelastic neutron scattering to study the fate of the two spin resonance modes in underdoped superconducting NaFe 1 − x Co x As ( x = 0.0175 ) under applied magnetic fields. While an in-plane magnetic field of B = 12  T only modestly suppresses superconductivity and enhances static antiferromagnetic order,... [Phys. Rev. B 98, 064507] Published Mon Aug 13, 2018

Description: Author(s): N. R. Lee-Hone, V. Mishra, D. M. Broun, and P. J. Hirschfeld We argue that recent measurements on both the superfluid density and the optical conductivity of high-quality La 2 − x Sr x CuO 4 (LSCO) films can be understood almost entirely within the theory of disordered BCS d -wave superconductors. The large scattering rates deduced from experiments are shown to arise... [Phys. Rev. B 98, 054506] Published Tue Aug 14, 2018

Description: Author(s): S. Mitra, A. P. Petrović, D. Salloum, P. Gougeon, M. Potel, Jian-Xin Zhu, C. Panagopoulos, and Elbert E. M. Chia We present magnetic penetration depth and electrical transport data in single crystals of quasi-one-dimensional (q1D) Tl 2 Mo 6 Se 6 , which reveal a 1 D → 3 D superconducting dimensional crossover. The c -axis penetration depth shows the onset of superconducting fluctuations below T 1 D o n s = 6.7 K, whereas signat... [Phys. Rev. B 98, 054507] Published Tue Aug 14, 2018

Description: Author(s): L. Kuerten, E. Fillis-Tsirakis, C. Richter, J. Mannhart, and H. Boschker Numerous two-dimensional superconductors exhibit a characteristic dome-shaped dependence of the critical temperature T c on the carrier density. The reduction of the critical temperature with increasing charge carrier density on the overdoped side of this dome is frequently related to scattering aris... [Phys. Rev. B 98, 054509] Published Wed Aug 15, 2018

Description: Author(s): Christian Spånslätt One of the salient signatures of Majorana zero modes and topological superconductivity is a 4 π -periodic Josephson effect due to the combination of fermion parity conservation and the presence of a topologically protected odd number of zero-energy crossings in the Andreev spectrum. In this paper, we ... [Phys. Rev. B 98, 054508] Published Wed Aug 15, 2018

Description: Author(s): Risto Ojajärvi, Timo Hyart, Mihail A. Silaev, and Tero T. Heikkilä The effective attractive interaction between electrons, mediated by electron-phonon coupling, is a well-established mechanism of conventional superconductivity. In metals exhibiting a Fermi surface, the critical temperature of superconductivity is exponentially smaller than the characteristic phonon... [Phys. Rev. B 98, 054515] Published Wed Aug 22, 2018

Description: Author(s): O. Cyr-Choinière, D. LeBoeuf, S. Badoux, S. Dufour-Beauséjour, D. A. Bonn, W. N. Hardy, R. Liang, D. Graf, N. Doiron-Leyraud, and Louis Taillefer Cuprate superconductors have a universal tendency to form charge density-wave (CDW) order which competes with superconductivity and is strongest at a doping p ≃ 0.12 . Here we show that in the archetypal cuprate YBa 2 Cu 3 O y (YBCO) pressure suppresses charge order but does not affect the pseudogap phase. ... [Phys. Rev. B 98, 064513] Published Thu Aug 30, 2018

Description: Author(s): Xin Wang, Zhiqiang Wang, and Catherine Kallin The effects of finite temperature, Meissner screening, and surface roughness on the spontaneous edge current for higher chirality quasi-two-dimensional superconductors are studied in the continuum limit using the quasiclassical Eilenberger equations. We find that the total spontaneous current is non... [Phys. Rev. B 98, 094501] Published Tue Sep 04, 2018

Description: Author(s): Zitao Wang, Shang-Qiang Ning, and Xie Chen In this paper, we present an exactly solvable model for two-dimensional topological superconductors with helical Majorana edge modes protected by time-reversal symmetry. Our construction is based on the idea of decorated domain walls and makes use of the Kasteleyn orientation on a two-dimensional la... [Phys. Rev. B 98, 094502] Published Tue Sep 04, 2018

Description: Author(s): Shunji Tsuchiya, Daisuke Yamamoto, Ryosuke Yoshii, and Muneto Nitta A massive Goldstone (MG) mode, often referred to as a Higgs amplitude mode, is a collective excitation that arises in a system involving spontaneous breaking of a continuous symmetry, along with a gapless Nambu-Goldstone mode. It has been known in the previous studies that a pure amplitude MG mode e... [Phys. Rev. B 98, 094503] Published Tue Sep 04, 2018