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NASA NTRS2013

Discovery of a Giant Radio Halo in a New Planck Galaxy Cluster PLCKG171.9-40.7

We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from a NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, has an extent of approx.1 Mpc and a radio power of approx. 5×10(exp 24)W/Hz at 1.4 GHz. Its integrated radio spectrum has a slope of alpha approx. = 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMMNewton X-ray data shows that the cluster is hot (approx. 10 keV) and disturbed, consistent with X-ray selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.

Giacintucci, Simona↗

NASA NTRS2016

Fermi-Lat Observations of High-Energy Gamma-Ray Emission Toward the Galactic Center

The Fermi Large Area Telescope (LAT) has provided the most detailed view to date of the emission toward the Galactic center (GC) in high-energy gamma-rays. This paper describes the analysis of data taken during the first 62 months of the mission in the energy range 1-100 GeV from a 15 degrees x 15 degrees region about the direction of the GC. Specialized interstellar emission models (IEMs) are constructed to enable the separation of the gamma-ray emissions produced by cosmic ray particles interacting with the interstellar gas and radiation fields in the Milky Way into that from the inner 1 kpc surrounding the GC, and that from the rest of the Galaxy. A catalog of point sources for the 15 degrees x 15 degrees region is self-consistently constructed using these IEMs: the First Fermi-LAT Inner Galaxy Point SourceCatalog (1FIG). The spatial locations, fluxes, and spectral properties of the 1FIG sources are presented, and compared with gamma-ray point sources over the same region taken from existing catalogs. After subtracting the interstellar emission and point-source contributions a residual is found. If templates that peak toward the GC areused to model the positive residual the agreement with the data improves, but none of the additional templates tried account for all of its spatial structure. The spectrum of the positive residual modeled with these templates has a strong dependence on the choice of IEM.

cosmic rays â€“ Galaxy: center â€“ gamma-rays: gen↗

NASA NTRSDate not supplied

Microgreens Food Safety Evaluation

Microgreens have been recently identified as a new type of pick and eat salad crop that can be utilized in space crop production systems. The majority of traditionally grown leafy green crops can be grown as microgreens, in addition to crops such as legumes (e.g. pea shoots), sunflower, buckwheat, most herbs, and corn, presenting hundreds of microgreen crop options. With a wide variety of flavors, exceptional nutritional density, short growth cycles (7-14 days), and unmatched volume optimization potential, microgreens present as an interesting option for sustainable production of nutritious and flavorful crops in space. The food safety aspects of microgreens have been investigated by USDA in recent years, however, an assessment for crew consumption purposes has not yet been conducted to capture the variety of microgreen cultivar types grown in spaceflight relevant environmental conditions and hardware that could be a part of the astronaut diet. Seed sanitation methods will be developed for each microgreen cultivar to sanitize the seed coat and ensure viable germination and plant growth. Food safety analysis will be performed on 24 different fast-growing cultivars of microgreens by performing aerobic plate counts (APC), fungal counts, and select pathogen screening of edible plant tissue before and after treatment with ProSan sanitizing produce wash. Additional avenues of investigation into microgreens food safety will be undertaken to understand impacts of plant height at time of harvest (able to be manipulated by light spectrum), seed density at time of planting, and role of blue light in food safety metrics of microgreens (n=6-12 microgreen cultivars tested, depending on variable). These findings will be included in the Space Crop Production Hazard Analysis Critical Control Point (HACCP) plan. This new work is currently postponed due to Covid-19.

M E Hummerick↗

NASA NTRSDate not supplied

Processes and Methods used for NASA Communications Services Project Conceptualization and Formulation

The U.S. National Aeronautics and Space Administration (NASA) is partnering with the commercial SATCOM industry to demonstrate the industry’s capabilities to provide services to NASA’s near-Earth missions. Leveraging commercial capabilities will become increasingly necessary for NASA, as its incumbent Government-owned-and-operated near-Earth satellite network, the Tracking and Data Relay Satellite System (TDRSS), will approach retirement towards the end of the current decade. NASA is actively taking the first steps to making the vision of using commercial SATCOM a reality. For more than two years, NASA’s Communication Services Project (CSP) has been evaluating the feasibility of employing commercial satellite communication (SATCOM) networks for near-Earth operations. This past April, CSP awarded US$278.5 million in Funded Space Act Agreements to select commercial SATCOM providers, so they may begin developing and demonstrating their specific near-Earth space communication services that may support future agency missions. Each company will match or exceed agency contributions during the five-year development and demonstration period, totaling more than $1.5 billion of cost-share investment. The companies will complete technology development and in-space demonstrations by 2025, after which NASA intends to seek multiple long-term contracts to acquire these kinds of services. The six companies (Inmarsat Government Inc., Kuiper Government Solutions (KGS), SES Government Solutions, Space Exploration Technologies (SpaceX), Telesat U.S. Services and Viasat Inc.) will shortly begin developing and demonstrating their capabilities to provide services, ranging from launch to standard on-orbit operations. The demonstrations will be across multiple spectrum regimes from L-Band to optical, and will utilize Geostationary Orbit (GEO), Medium-Earth Orbit (MEO) and Low-Earth Orbit (LEO) constellations. This paper discusses methodologies and processes used over the past two years to reach the point of entering into these partnerships. It also includes CSP’s goals and objectives going forward, following the award of six Funded Space Act Agreements to commercial SATCOM providers to develop and demonstrate these capabilities.

Communications Services Project↗

NASA NTRSDate not supplied

Processes and Methods used for Nasa Communications Services Project Conceptualization and Formulation

Communications Services Project↗

NASA NTRS2008

Eta Car: The Good, the Bad and the Ugly of Nebular and Stellar Confusion

Observations in the far-UV provide a unique opportunity to investigate the very massive star Eta Car and its hot binary companion, Eta Car B. Eta Car was observed with FUSE over a large portion of the 5.54 year spectroscopic period before and after the 2003.5 minimum. The observed spectrum is defined by strong stellar wind signatures, primarily from Eta Car A, complicated by the strong absorptions of the ejecta surrounding Eta Car plus interstellar absorption. The Homunculus and Little Homunculus are massive bipolar ejecta historically associable with LBV outbursts in the 1840s and the 1890s and are linked to absorptions at -513 and -146 km/s, respectively. The FUSE spectra are confused by the extended nebulosity and thermal drifting of the FUSE co-pointed instruments. Interpretation is further complicated by two B-stars sufficiently close to h Car to be included most of the time in the large FUSE aperture. Followup observations partially succeeded in obtaining spectra of at least one of these B-stars through the smaller apertures, allowing potential separation of the B-star contributions and h Car. A complete analysis of all available spectra is currently underway. Our ultimate goals are to directly detect the hot secondary star if possible with FUSE and to identify the absorption contributions to the overall spectrum especially of the stellar members and the massive ejecta.

Gull, T.R.↗

DOE OSTI2026

Delayed Neutron Precursor Group Parameter and Spectra Generation from Fast Fission of 235U in SCALE

Delayed neutron precursor (DNP) group data are important for modeling reactor dynamics. Although the data for individual DNPs have been developed over time, the DNP group data present in the Evaluated Nuclear Data Files (ENDF) have not been updated in the past 20 years. In this work, we use SCALE to recreate the Godiva experiment that was used to generate the original DNP group structure for fast fission of 235U. However, each DNP is modeled using up-to-date data, and the results are then converted into a newly updated group structure. This conversion uses an iterative linear least squares solver to minimize chi-squared. The approaches used in this work also enable energy spectrum generation and uncertainty tracking. The method used in this paper for fast 235U fission DNP group structure updating can be applied to different energies and fissile nuclides. Demonstration of the uncertainty tracking in reactor kinetics and dynamics simulations is shown using point reactor kinetics simulations. Results show that there are data discrepancies between the International Atomic Energy Agency database and data used in ORIGEN, which are currently being fixed. Results also show that the proposed method for group spectra generation performs well.

Seifert, Luke [University of Illinois]↗

NASA NTRS1974

Cosmic ray telescope for OGO 2 and 4 spacecraft

The construction and subsequent flight are described of a cosmic ray telescope aboard the OGO-2 and 4 Spacecraft. This instrument was a combination Cerekov-scintillation counter telescope designed to measure the cosmic ray energy spectrum from 1-15 GV and charge composition from Z=1-8. OGO-2 was launched in October 1965; however, attitude control problems caused a rapid loss of control gas, so that after approximately 2 weeks it was no longer possible to point the spacecraft. This mission was officially declared a failure. The cosmic ray instrument appeared to work well during this time. OGO-4 was launched in July 1967, with a similar telescope aboard. It operated successfully approximately one year. The details of the experiment, its operation, and the results are given.

Webber, W. R.↗

NASA NTRS1979

Particle acceleration by propagating interplanetary shocks

The process of charged particle acceleration in interplanetary shocks has been simulated for typical parameters. Since space probe observations of charged particle fluxes are the principle means of inferring the action of an acceleration mechanism, the simulation was designed to follow particles backwards in time from a given observing point, usually 1 AU. This allowed a full diagnosis of which observed particles had interacted with an oncoming shock, where the interacting occurred, and by how much the energy had been changed by the shock interaction. Simple assumptions about the preshock energy spectrum allow the construction of a full temporal profile of the expected intensity, anisotropy, and energy spectrum. The simulations are apparently capable of reproducing the main features of the less than 10 MeV/nuc ion flux enhancements observed at interplanetary shocks using only a laminar interplanetary magnetic field, Archimidean spiral, and a spherical oblique shock with typical speed, strength, and shock normal-magnetic field angle.

Armstrong, T. P.↗

NASA NTRS1985

The wave pattern produced by a point source on a rotating disk

It is pointed out that the boundary layer on a rotating disk is important in stability theory because it provides a particularly simple way to study the important phenomenon of crossflow instability. This type of instability is responsible for early transition on sweptback wings. Mack and Kendall (1983) have studied the wave patterns formed by harmonic point sources in a Blasius boundary layer on the basis that the source uniformly excites all oblique normal modes of the source frequency. The calculation procedure for planar boundary layers was modified to fit the different geometry of the rotating disk and the lack of an axis of symmetry. Calculations were performed of the wave pattern produced by a zero-frequency point source located at the Reynolds number of the artificial roughness element in an experiment conducted by Wilkinson and Malik (1983). The results provided in the present investigation confirm that the experimental wave pattern is a superposition of the complete azimuthal wavenumber spectrum of zero-frequency normal modes with uniform initial amplitude and phase.

Mack, L. M.↗

NASA NTRS1985

Cluster-cluster clustering

The cluster correlation function xi sub c(r) is compared with the particle correlation function, xi(r) in cosmological N-body simulations with a wide range of initial conditions. The experiments include scale-free initial conditions, pancake models with a coherence length in the initial density field, and hybrid models. Three N-body techniques and two cluster-finding algorithms are used. In scale-free models with white noise initial conditions, xi sub c and xi are essentially identical. In scale-free models with more power on large scales, it is found that the amplitude of xi sub c increases with cluster richness; in this case the clusters give a biased estimate of the particle correlations. In the pancake and hybrid models (with n = 0 or 1), xi sub c is steeper than xi, but the cluster correlation length exceeds that of the points by less than a factor of 2, independent of cluster richness. Thus the high amplitude of xi sub c found in studies of rich clusters of galaxies is inconsistent with white noise and pancake models and may indicate a primordial fluctuation spectrum with substantial power on large scales.

Barnes, J.↗

NASA NTRS1986

Small-scale coronal structure, part 3

Recent observations and models pertaining specifically to solar coronal bright points (BPs) and generally to small-scale coronal structure are reviewed. Two questions were addressed: What is the degree of correspondence among various alleged signatures of BPs at different levels of atmosphere and what can PBs tell about the emerging flux spectrum of the sun?

Webb, David F.↗

NASA NTRS1988

High altitude current-voltage measurement of GaAs/Ge solar cells

Measurements of high-voltage (Voc of 1.2 V) gallium arsenide on germanium tandem junction solar cells at air mass 0.22 showed that the insolation in the red portion of the solar spectrum is insufficient to obtain high fill factor. On the basis of measurements in the LeRC X-25L solar simulator, these cells were believed to be as efficient as 21.68 percent AM0. Solar simulator spectrum errors in the red end allowed the fill factor to be as high as 78.7 percent. When a similar cell's current-voltage characteristic was measured at high altitude in the NASA Lear Jet Facility, a loss of 15 percentage points in fill factor was observed. This decrease was caused by insufficient current in the germanium bottom cell of the tandem stack.

Hart, Russell E., Jr.↗

NASA NTRS2001

High Resolution Observations and Modeling of Small-Scale Solar Magnetic Elements

This research contract investigating the radiative transfer and dynamic physics of the smallest observable magnetic structures in the solar photosphere. Due to the lack of a high-resolution visible light satellite instrument for solar studies, all data were acquired using ground-based instrumentation. The primary goal of the investigation was to understand the formation and evolution of "G-band bright points" in relation to the associated magnetic elements. G-band bright points are small (on the order of 100 kin or less in diameter) bright signatures associated with magnetic flux elements in the photosphere. They are seen in the A2A-X2 4308 A molecular bandhead of the CH radical ill the solar spectrum and offer the highest spatial resolution and highest contrast "tracers" of small magnetic structure on the Sun.

Berger, Thomas E.↗

NASA NTRS2001

Captain, sensors report ...: Correction of Remote Sensing Data

Remote sensing data acquired by airborne and satellite Systems have many impressive virtues for ecology and other sciences. They are synoptic. They are extremely cheap per data point. They cover large areas. They are not subjective. They detect features that are of clear and obvious interest for many uses. But, they also yield totally irreproducible measurements. Sensors that operate in the visible, near infrared and thermal portions of the spectrum are sensitive to a host of phenomena that are usually of little interest to the average user. Fully recognizing the power and sophistication of the algorithms currently available to users of remote sensing, the authors as long time developers (20+ years) of such algorithms, demonstrate that a host of other signals are convolved with the typical data set, and that many of these signals are very commonly not even recognized, and that these signals are often larger than the signal from the putative target. These derive from both geometric and radiometric sources as well as fundamental flaws in sensor engineering. Until such extraneous factors can be controlled or eliminated the utility of the data is greatly restricted. Finally, the authors lay out a design elements for a rational sensor and methods of deconvolving the complexity of the real world data using such a sensor.

Rickman, Doug↗

NASA NTRS2016

A Numerical Theory for Impedance Education in Three-Dimensional Normal Incidence Tubes

A method for educing the locally-reacting acoustic impedance of a test sample mounted in a 3-D normal incidence impedance tube is presented and validated. The unique feature of the method is that the excitation frequency (or duct geometry) may be such that high-order duct modes may exist. The method educes the impedance, iteratively, by minimizing an objective function consisting of the difference between the measured and numerically computed acoustic pressure at preselected measurement points in the duct. The method is validated on planar and high-order mode sources with data synthesized from exact mode theory. These data are then subjected to random jitter to simulate the effects of measurement uncertainties on the educed impedance spectrum. The primary conclusions of the study are 1) Without random jitter the method is in excellent agreement with that for known impedance samples, and 2) Random jitter that is compatible to that found in a typical experiment has minimal impact on the accuracy of the educed impedance.

Watson, Willie R.↗

DOE OSTI2025

Window convolution of the galaxy clustering bispectrum

In galaxy survey analysis, the observed clustering statistics do not directly match theoretical predictions but rather have been processed by a window function that arises from the survey geometry including the sky footprint, redshift-dependent background number density and systematic weights. While window convolution of the power spectrum is well studied, for the bispectrum with a larger number of degrees of freedom, it poses a significant numerical and computational challenge. In this work, we consider the effect of the survey window in the tripolar spherical harmonic decomposition of the bispectrum and lay down a formal procedure for their convolution via a series expansion of configuration-space three-point correlation functions, which was first proposed by Sugiyama et al. (2019). We then provide a linear algebra formulation of the full window convolution, where an unwindowed bispectrum model vector can be directly premultiplied by a window matrix specific to each survey geometry. To validate the pipeline, we focus on the Dark Energy Spectroscopic Instrument (DESI) Data Release 1 (DR1) luminous red galaxy (LRG) sample in the South Galactic Cap (SGC) in the redshift bin 0.4 ≤ z ≤ 0.6. We first perform convergence checks on the measurement of the window function from discrete random catalogues, and then investigate the convergence of the window convolution series expansion truncated at a finite of number of terms as well as the performance of the window matrix. This work highlights the differences in window convolution between the power spectrum and bispectrum, and provides a streamlined pipeline for the latter for current surveys such as DESI and the Euclid mission.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

Re-evaluating the prompt fission neutron spectrum of spontaneously fissioning 252 Cf

The prompt fission neutron spectrum (PFNS) of spontaneously fissioning 252 Cf is a Neutron Data Standards observable. Nearly all fission spectra of actinides were measured relative to it, using efficiencies derived from it, or analyzed with simulations validated by it. The current Standards evaluation was published by W. Mannhart in 1987. It could not be updated because the evaluation input, experimental mean values and covariances, were lost. First, we attempt to reproduce it. However, Mannhart’s evaluation can only be reproduced within its one-σ uncertainties as some of its aspects (e.g., experimental covariances, rejected data points) remain unknown. Therefore, a new evaluation is presented: We revisit all existing experimental 252 Cf(sf) PFNS data, including those published after the release of the current Standards evaluation, and re-estimate associated covariances. The newly evaluated 252 Cf(sf) PFNS differs distinctly from Mannhart’s below 300 keV and extends it to lower and higher outgoing neutron energies (500 eV–25 MeV). The new evaluated uncertainties are larger from 3–9 MeV and smaller otherwise. Spectrum averaged cross sections of importance to the International Reactor Dosimetry and Fusion File community calculated with the new spectrum are close to those calculated with Mannhart’s evaluation and agree with experimental values well within their uncertainties.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗