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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Optical Follow-Up of the Neutron Star-Black Hole Mergers S200105ae and S200115j

LIGO and Virgo’s third observing run revealed the first neutron star–black hole (NSBH) merger candidates in gravitational waves. These events are predicted to synthesize r-process elements creating optical/near-infrared ‘kilonova’ emission. The joint gravitational wave and electromagnetic detection of an NSBH merger could be used to constrain the equation of state of dense nuclear matter, and independently measure the local expansion rate of the Universe. Here, we present the optical follow-up and analysis of two of the only three high-significance NSBH merger candidates detected to date, S200105ae and S200115j, with the Zwicky Transient Facility. The Zwicky Transient Facility observed ~48% of S200105ae and ~22% of S200115j’s localization probabilities, with observations sensitive to kilonovae brighter than −17.5 mag fading at 0.5 mag d−1 in the g- and r-bands; extensive searches and systematic follow-up of candidates did not yield a viable counterpart. We present state-of-the-art kilonova models tailored to NSBH systems that place constraints on the ejecta properties of these NSBH mergers. We show that with observed depths of apparent magnitude ~22 mag, attainable in metre-class, wide-field-of-view survey instruments, strong constraints on ejecta mass are possible, with the potential to rule out low mass ratios, high black hole spins and large neutron star radii.

Shreya Anand↗
DOE OSTI2025

Alaska's Rural Building Stock: a Validation Study Using ResStock and Field Data

The availability of accurate national data on demographics, building stock, and energy use is vital for modeling residential buildings and evaluating decarbonization strategies. However, rural and Indigenous populations, including those in rural Alaska, are typically underrepresented in these datasets. These communities face unique challenges due to their remote locations, severe weather conditions, and limited access to resources, resulting in high energy burden. This report examines how rural Alaskan communities are underrepresented in the ResStock housing model and highlights the need for improved data to address their unique housing and energy challenges. Thus, this report examines the representation of rural Alaskan communities within the national housing stock model, ResStock. A validation study was conducted, considering ResStock, Field Data and Aerial and 3D-view data collection (A3DDC) datasets. The validation process started by using the down selecting approach on the ResStock building stock dataset. For the purpose of this study, only the rural Alaska Boroughs and Census areas located in ASHRAE IECC Climate Zone 8 were considered to ensure a more accurate and fair comparison with the field data, which was collected in rural areas located in climate zone 8, specifically within the Nome Census area. While ResStock may accurately represent several characteristics of the building stock for rural Alaska, some differences between modeled, field data, and aerial and 3D-view data collection datasets were identified. The following building characteristics have a high impact on modeled energy consumption and demonstrated large differences: Revisit heating setpoints and consider a substantially higher setpoint distribution, it could potentially address "missing loads" if this is the case. Develop and include Toyo heating in future modeling for ResStock and EnergyPlus. Remove natural gas as a water heater fuel type outside of North Slope County. Foundation type updated to have more crawlspaces rather than basements. Infiltration rates need reexamination for a larger distribution toward higher infiltration rates. Include more vinyl and less brick in exterior wall type and revise wall color for greater proportion of light rather than dark color. Roof material revised from majority shingles to majority metal. Update number of occupants to higher number of occupant count. Building orientation represents a higher proportion of south facing buildings rather than relatively equal. The findings suggest that updating ResStock's probability logic could better represent rural Alaskan buildings. ResStock can be utilized to identify the best upgrades or energy efficiency and energy efficiency improvements, helping community leaders in making more informed decisions.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1978

Advanced Multispectral Scanner (AMS) study

The status of aircraft multispectral scanner technology was accessed in order to develop preliminary design specifications for an advanced instrument to be used for remote sensing data collection by aircraft in the 1980 time frame. The system designed provides a no-moving parts multispectral scanning capability through the exploitation of linear array charge coupled device technology and advanced electronic signal processing techniques. Major advantages include: 10:1 V/H rate capability; 120 deg FOV at V/H = 0.25 rad/sec; 1 to 2 rad resolution; high sensitivity; large dynamic range capability; geometric fidelity; roll compensation; modularity; long life; and 24 channel data acquisition capability. The field flattening techniques of the optical design allow wide field view to be achieved at fast f/nos for both the long and short wavelength regions. The digital signal averaging technique permits maximization of signal to noise performance over the entire V/H rate range.

Source record↗
NASA NTRS1980

X-ray bright points and the solar cycle dependence of emerging magnetic flux

Soft X-ray imaging of the solar corona during the period 1970 to 1978 resulted in significant modifications to the view of the solar cycle with respect to both the properties of the large scale (coronal holes) and small scale (X-ray Bright Points) solar magnetic field. In the latter case, the particular contribution is to the emerging magnetic flux. Sounding rocket observations combined with the Skylab data indicate that the XBP are anticorrelated with sunspot number and are the dominant contributors to the solar cycle. A continuous data set covering a complete cycle would enable the validity of this result which has serious implications for the nature of the solar dynamo, to be confirmed.

Davis, J. M.↗
NASA NTRS1984

A study on the imaging potential of QUASAT

The orbit, ground array, and sensitivities of the space and ground systems of the QUASAT spaceborne astronomy mission were studied. Parameters which yield images in which the noise is within a factor of three of the thermal noise limit were derived. With a very large ground array QUASAT should produce images as complex as the best of the VLA. At 22 GHz the resolution will be 0.1 milliarcsec, the field of view 15 milliarcsec, and it will be possible to make noise limited maps of complex objects. The QUASAT is essential for mapping southern declination objects. Without QUASAT, even the simple core-jet source cannot be mapped at declination minus 60 deg. It will be possible with QUASAT to make maps with observing times as short as 6 hr although the very best maps will require 48 hr observations.

Readhead, A. C. S.↗
NASA NTRS1990

Low-temperature thermal control for a lunar base

The generic problem of rejecting low- to moderate-temperature heat from space facilities located in a hot thermal sink environment is studied, and the example of a lunar base located near the equator is described. The effective thermal sink temperature is often above or near nominal room temperature. A three heat pump assisted thermal bus concept appears to be the most viable as they are the least sensitive to environmental conditions. Weight estimates are also developed for each of the five thermal control concepts studied: (1) 149kg/kW for a central thermal loop with unitary heat pumps; (2) 133 kg/kW for a conventional bus connected to large, central heat pumps at the radiator; (3) 134 kg/kW for a central, dual loop heat pump concept; (4) 95 kg/kW for the selective field-of-view radiator; and (5) 126 kg/kW for the regolith concept.

Swanson, Theodore D.↗
NASA NTRS1991

A combined finite element-boundary element formulation for solution of axially symmetric bodies

A new method is presented for the computation of electromagnetic scattering from axially symmetric bodies. To allow the simulation of inhomogeneous cross sections, the method combines the finite element and boundary element techniques. Interior to a fictitious surface enclosing the scattering body, the finite element method is used which results in a sparce submatrix, whereas along the enclosure the Stratton-Chu integral equation is enforced. By choosing the fictitious enclosure to be a right circular cylinder, most of the resulting boundary integrals are convolutional and may therefore be evaluated via the FFT with which the system is iteratively solved. In view of the sparce matrix associated with the interior fields, this reduces the storage requirement of the entire system to O(N) making the method attractive for large scale computations. The details of the corresponding formulation and its numerical implementation are described.

Collins, Jeffrey D.↗
NASA NTRS1992

The ALEXIS data processing package: An IDL based system

The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of a mini-satellite containing six wide angle EUV/ultrasoft x-ray telescopes. Its purpose is to map out the sky in three narrow (approximately 5 percent) bandpasses around 66, 71, and 93 eV. The 66 and 71 eV bandpasses are centered on intense Fe emission lines which are characteristic of million degree plasmas such as the one thought to produce the soft x-ray background. The 93 eV bandpass is not near any strong emission lines and is more sensitive to continuum sources. The mission will be launched on the Pegasus Air Launched Vehicle in the second half of 1992 into a 400-nautical-mile, high inclination orbit and will be controlled entirely from a small ground station located at Los Alamos. The project is a collaborative effort between Los Alamos National Laboratory, Sandia National Laboratory, and the University of California-Berkeley Space Sciences Laboratory. The six telescopes are arranged in three pairs. As the satellite spins twice a minute they scan the entire anti-solar hemisphere. Each f/1 telescope consists of a spherical, multilayer-coated mirror with a curved, microchannel plate detector located at the prime focus. The multilayer coatings determine the bandpasses of the telescopes. The field of view of each telescope is 30 degrees with a spatial resolution of 0.5 degree, limited by spherical aberration. The data processing requirements for ALEXIS are large. Each event is one of the six telescopes is telemetered to the ground with its time of arrival and position on the detector. This information must be folded with the aspect solution for the satellite to reconstruct the direction on the sky from which the photon came. Because of the way the six telescopes scan the sky, the effective exposure calculation is also very computationally intensive. ALEXIS may generate up to 100 megabytes of raw data per day, which are converted into a gigabyte per day of processed data. While the processing job for ALEXIS is sizable, the programming staff is small. To maximize programming efficiency, and to make the best use of tools available in the public domain, we chose IDL as our software development platform. IDL was used from the start of instrument development through flight. We use IDL as a top-level executive for the processing tasks (replacing Unix shell scripts), as a device independent graphics engine, as a database manager, and as a final data manipulator. IDL routines spawn special purpose C programs to perform detailed telemetry deconvolution and other specialized functions. We discuss the use of IDL and C within the processing and archiving strategy for the ALEXIS data anlaysis system as implemented on a SPARCstation platform. We also show results from our End-to-End software simulation capability as processed by our analysis codes.

Bloch, J. J.↗
NASA NTRS1997

Application of a Threshold Method to the TRMM Radar for the Estimation of Space-Time Rain Rate Statistics

One of the TRMM radar products of interest is the monthly-averaged rain rates over 5 x 5 degree cells. Clearly, the most directly way of calculating these and similar statistics is to compute them from the individual estimates made over the instantaneous field of view of the Instrument (4.3 km horizontal resolution). An alternative approach is the use of a threshold method. It has been established that over sufficiently large regions the fractional area above a rain rate threshold and the area-average rain rate are well correlated for particular choices of the threshold [e.g., Kedem et al., 19901]. A straightforward application of this method to the TRMM data would consist of the conversion of the individual reflectivity factors to rain rates followed by a calculation of the fraction of these that exceed a particular threshold. Previous results indicate that for thresholds near or at 5 mm/h, the correlation between this fractional area and the area-average rain rate is high. There are several drawbacks to this approach, however. At the TRMM radar frequency of 13.8 GHz the signal suffers attenuation so that the negative bias of the high resolution rain rate estimates will increase as the path attenuation increases. To establish a quantitative relationship between fractional area and area-average rain rate, an independent means of calculating the area-average rain rate is needed such as an array of rain gauges. This type of calibration procedure, however, is difficult for a spaceborne radar such as TRMM. To estimate a statistic other than the mean of the distribution requires, in general, a different choice of threshold and a different set of tuning parameters.

Meneghini, Robert↗
NASA NTRS2003

Analysis of Burst Observations by GLAST's LAT Detector

Analyzing data from GLAST's Large Area Telescope (LAT) will require sophisticated techniques. The PSF and effective area are functions of both photon energy and the position in the field-of-view. During most of the mission the observatory will survey the sky continuously and thus the LAT will detect each count from a source at a different detector orientation; each count requires its own response function! The likelihood as a function of celestial position and photon energy will be the foundation of the standard analysis techniques. However the 20 MeV-300 GeV emission at the time of the approx.100 keV burst emission (timescale of approx.10 s) can be isolated and analyzed because essentially no non-burst counts are expected within a PSF radius of the burst location during the burst. Both binned and unbinned (in energy) spectral fitting will be possible. Longer timescale afterglow emission will require the likelihood analysis that will be used for persistent sources.

Band, David L.↗
NASA NTRS2010

Goddard Robotic Telescope - Optical Follow-up of GRBs and Coordinated Observations of AGNs

Since it is not possible to predict when a Gamma-Ray Burst (GRB) will occur or when Active Galactic Nucleus (AGN) flaring activity starts, follow-up/monitoring ground telescopes must be located as uniformly as possible all over the world in order to collect data simultaneously with Fermi and Swift detections. However, there is a distinct gap in follow-up coverage of telescopes in the eastern U.S. region based on the operations of Swift. Motivated by this fact, we have constructed a 14" fully automated optical robotic telescope, Goddard Robotic Telescope (GRT), at the Goddard Geophysical and Astronomical Observatory. The aims of our robotic telescope are 1) to follow-up Swift/Fermi GRBs and 2) to perform the coordinated optical observations of Fermi Large Area Telescope (LAT) AGN. Our telescope system consists of off-the-shelf hardware. With the focal reducer, we are able to match the field of view of Swift narrow instruments (20' x 20'). We started scientific observations in mid-November 2008 and GRT has been fully remotely operated since August 2009. The 3(sigma) upper limit in a 30-second exposure in the R filter is approx.15.4 mag; however, we can reach to approx.18 mag in a 600-second exposures. Due to the weather condition at the telescope site. our observing efficiency is 30-40%, on average.

Sakamoto, T.↗
NASA NTRS1992

Demonstration of magnetic domain boundary movement using an easily assembled videocam-microscope system

The objectives are to build and demonstrate a low cost and highly flexible TV microscope facility and then use it to view the motion of magnetic domain boundaries as the local magnetic field is varied. The expense of an optical microscope and the videocam adapters sold for them is largely avoided by using the facility described below. The equipment, supplies, and procedure are presented.

Patterson, John W.↗
NASA NTRS2012

The Fermi Large Area Telescope on Orbit: Event Classification, Instrument Response Functions, and Calibration

The Fermi Large Area Telescope (Fermi-LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy -ray telescope, covering the energy range from 20 MeV to more than 300 GeV. During the first years of the mission the LAT team has gained considerable insight into the in-flight performance of the instrument. Accordingly, we have updated the analysis used to reduce LAT data for public release as well as the Instrument Response Functions (IRFs), the description of the instrument performance provided for data analysis. In this paper we describe the effects that motivated these updates. Furthermore, we discuss how we originally derived IRFs from Monte Carlo simulations and later corrected those IRFs for discrepancies observed between flight and simulated data. We also give details of the validations performed using flight data and quantify the residual uncertainties in the IRFs. Finally, we describe techniques the LAT team has developed to propagate those uncertainties into estimates of the systematic errors on common measurements such as fluxes and spectra of astrophysical sources.

Ackermann, M.↗
DOE OSTI2023

Overview on Shielding Analyses for the VENUS Instrument at SNS

VENUS, a world‐class versatile neutron imaging instrument, is under construction and is expected to be completed and ready to start commissioning in 2023. The range of cold to epithermal neutrons at SNS will give users of VENUS access to novel imaging methods, as well as to significantly improved existing methods. The instrument is being built on beam line 10 at Spallation Neutron Source (SNS) First Target Station (FTS) facing a decoupled poisoned hydrogen moderator. Instrument design, which includes optics, Front-End components and instrument enclosure components and shape started over 10 years ago and during this time had significant changes. All changes were supported by neutronics analyses to provide adequate shielding for both Front-End and instrument enclosure.Final optics design will provide the field of view (FOV) at the detector position (where the image is formed) to be as high as 0.20 by 0.20 m. Both the beam, which contains a large fraction of high-energy neutrons, and the desire for a large footprint on the detector are challenges for shielding design and budget, because the driving cost for the instrument is the beam line and enclosure shielding. For cost reason VENUS baseline design is optimized with respect to both the instrument cave footprint and its wall thickness, and Front-End shielding is tailored along the beam. Analyses are performed with the Monte Carlo particle transport code MCNPX version 2.7.0 to make choices on materials, thicknesses and configurations of the shielding. Numerous calculations are performed to meet space and coast constrain and to satisfy instrument physics needs and to comply with radiation protection requirements.

Gallmeier, Franz X.↗
NASA NTRS2010

Interplanetary Shocks Lacking Type 2 Radio Bursts

We report on the radio-emission characteristics of 222 interplanetary (IP) shocks detected by spacecraft at Sun-Earth L1 during solar cycle 23 (1996 to 2006, inclusive). A surprisingly large fraction of the IP shocks (approximately 34%) was radio quiet (RQ; i.e., the shocks lacked type II radio bursts). We examined the properties of coronal mass ejections (CMEs) and soft X-ray flares associated with such RQ shocks and compared them with those of the radio-loud (RL) shocks. The CMEs associated with the RQ shocks were generally slow (average speed approximately 535 km/s) and only approximately 40% of the CMEs were halos. The corresponding numbers for CMEs associated with RL shocks were 1237 km/s and 72%, respectively. Thus, the CME kinetic energy seems to be the deciding factor in the radio-emission properties of shocks. The lower kinetic energy of CMEs associated with RQ shocks is also suggested by the lower peak soft X-ray flux of the associated flares (C3.4 versus M4.7 for RL shocks). CMEs associated with RQ CMEs were generally accelerating within the coronagraph field of view (average acceleration approximately +6.8 m/s (exp 2)), while those associated with RL shocks were decelerating (average acceleration approximately 3.5 m/s (exp 2)). This suggests that many of the RQ shocks formed at large distances from the Sun, typically beyond 10 Rs, consistent with the absence of metric and decameter-hectometric (DH) type II radio bursts. A small fraction of RL shocks had type II radio emission solely in the kilometric (km) wavelength domain. Interestingly, the kinematics of the CMEs associated with the km type II bursts is similar to those of RQ shocks, except that the former are slightly more energetic. Comparison of the shock Mach numbers at 1 AU shows that the RQ shocks are mostly subcritical, suggesting that they were not efficient in accelerating electrons. The Mach number values also indicate that most of these are quasi-perpendicular shocks. The radio-quietness is predominant in the rise phase and decreases through the maximum and declining phases of solar cycle 23. About 18% of the IP shocks do not have discernible ejecta behind them. These shocks are due to CMEs moving at large angles from the Sun-Earth line and hence are not blast waves. The solar sources of the shock-driving CMEs follow the sunspot butterfly diagram, consistent with the higher-energy requirement for driving shocks.

Gopalswamy, N.↗
NASA NTRS1979

A cryogenically-cooled, balloon-borne far infrared survey telescope

The design and performance of the Arizona cryogenically-cooled, balloon-borne, multiband far infrared survey telescope are described. The 40 cm Cassegrain telescope is completely contained in a liquid helium dewar. The focal plane array consists of Fabry optics and four detectors which each have a 12 arc minute field of view. Both photoconductive and bolometer detectors are utilized at effective wavelengths of 20, 80, 100 and 150 microns. In 1977 the telescope was used to make multicolor large scale maps of 70 square degrees in the Cygnus X region and the W3 region.

Campbell, M. F.↗
NASA NTRS1981

Some fluid-dynamical problems in galaxies

Galaxies are examined through their primary components of gas and stars. The normal spiral and barred spiral galaxies have gaseous and stellar constituents in a thin disk, with a prominent nuclear bulge in the inner parts. The gaseous disk of matter is considered as a large-scale motion of the interstellar medium in the presence of the collective gravitational field of the massive stellar component in normal and spiral galaxies. The stellar component is viewed from a fluid-dynamical perspective; finally the asymptotic theory, dynamical mechanisms, and modal maintenance are discussed.

Lin, C. C.↗
NASA NTRS1985

Visual and motion cueing in helicopter simulation

Early experience in fixed-cockpit simulators, with limited field of view, demonstrated the basic difficulties of simulating helicopter flight at the level of subjective fidelity required for confident evaluation of vehicle characteristics. More recent programs, utilizing large-amplitude cockpit motion and a multiwindow visual-simulation system have received a much higher degree of pilot acceptance. However, none of these simulations has presented critical visual-flight tasks that have been accepted by the pilots as the full equivalent of flight. In this paper, the visual cues presented in the simulator are compared with those of flight in an attempt to identify deficiencies that contribute significantly to these assessments. For the low-amplitude maneuvering tasks normally associated with the hover mode, the unique motion capabilities of the Vertical Motion Simulator (VMS) at Ames Research Center permit nearly a full representation of vehicle motion. Especially appreciated in these tasks are the vertical-acceleration responses to collective control. For larger-amplitude maneuvering, motion fidelity must suffer diminution through direct attenuation through high-pass filtering washout of the computer cockpit accelerations or both. Experiments were conducted in an attempt to determine the effects of these distortions on pilot performance of height-control tasks.

Bray, R. S.↗