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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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226 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

UVOT Detection of GRB Afterglows

The automated response of the UltraViolet and Optical Telescope (UVOT) on Swift to new GRBs has remained stable since March 15,2006. From then through August 10, 2007, UVOT observed 122 of the 129 GRBs detected with Swift's Burst Alert Telescope (BAT). UVOT typically takes an initial 100-s exposure with the White filter (160-650 nm) starting 60 - 180 s after the trigger followed by exposures with the other 6 filters. UVOT detected 37% of the 79 long GRBs (T90 > 2.0 s) that had modest reddening in the Milky Way (E(B-V) < 0.5) and were observed within 180 seconds of the trigger. Magnitudes ranged from 12.8 to the sensitivity limit of approx.21. Only 1 of 8 short GRBs were detected, and its magnitude was near the sensitivity limit. We also report correlations of afterglow magnitudes with other GRB properties.

Marshall, Frank↗
NASA NTRS2012

Satellite Material Type and Phase Function Determination in Support of Orbital Debris Size Estimation

In performing debris surveys of deep-space orbital regions, the considerable volume of the area to be surveyed and the increased orbital altitude suggest optical telescopes as the most efficient survey instruments; but to proceed this way, methodologies for debris object size estimation using only optical tracking and photometric information are needed. Basic photometry theory indicates that size estimation should be possible if satellite albedo and shape are known. One method for estimating albedo is to try to determine the object's material type photometrically, as one can determine the albedos of common satellite materials in the laboratory. Examination of laboratory filter photometry (using Johnson BVRI filters) on a set of satellite material samples indicates that most material types can be separated at the 1-sigma level via B-R versus R-I color differences with a relatively small amount of required resampling, and objects that remain ambiguous can be resolved by B-R versus B-V color differences and solar radiation pressure differences. To estimate shape, a technique advanced by Hall et al. [1], based on phase-brightness density curves and not requiring any a priori knowledge of attitude, has been modified slightly to try to make it more resistant to the specular characteristics of different materials and to reduce the number of samples necessary to make robust shape determinations. Working from a gallery of idealized debris shapes, the modified technique identifies most shapes within this gallery correctly, also with a relatively small amount of resampling. These results are, of course, based on relatively small laboratory investigations and simulated data, and expanded laboratory experimentation and further investigation with in situ survey measurements will be required in order to assess their actual efficacy under survey conditions; but these techniques show sufficient promise to justify this next level of analysis.

Hejduk, M. D.↗
NASA NTRS2012

Preliminary Characterization of IDCSP Spacecrafts Through a Multi-Analytical Approach

Defining the risks present to both crewed and robotic spacecrafts is part of NASA s mission, and is critical to keep these resources out of harm s way. Characterizing orbital debris is an essential part of this mission. We present a proof-of-concept study that employs multiple techniques to demonstrate the efficacy of each approach. The targets of this study are IDCSPs (Initial Defense Communications Satellite Program). 35 of these satellites were launched by the US in the mid-1960s and were the first US military communications satellites in the GEO regime. They were emplaced in slightly sub-synchronous orbits. These targets were chosen for this proof-of-concept study for the simplicity of their observable exterior surfaces. The satellites are 26-sided polygons (86cm in diameter), initially spin-stabilized, and covered on all sides in solar panels. Data presented here include: (a) visible broadband photometry (Johnson/Kron-Cousins BVRI) taken with the 0.9m SMARTs telescope (Small and Medium Aperture Telescopes) at the Cerro Tololo Inter-American Observatory (CTIO) in Chile in April, 2012, (b) laboratory broadband photometry (Johnson/ Bessell BVRI) of solar cells, obtained using the Optical Measurements Center (OMC) at NASA/JSC [1], (c) visible-band spectra taken using the Magellan 6.5m Baade Telescope at Las Campanas Observatory in Chile in May, 2012 [2], and (d) visible-band laboratory spectra of solar cells using an ASD Field Spectrometer. Color-color plots using broadband photometry (e.g. B-R vs. B-V) demonstrate that different material types fall into distinct areas on the plots [1]. Spectra of the same material types as those plotted in the color-color plots each display their own signature as well. Here, we compare lab data with telescopic data, and photometric results with spectroscopic results. The spectral response of solar cells in the visible wavelength regime varies from relatively flat to somewhat older solar cells whose reflectivity can be gently or sharply peaked in the blue. With a target like IDCSPs, the material type is known a priori, aiding in understanding how material type affects one s observations.

Lederer, S. M.↗
NASA NTRS2016

On the Distance to the North Polar Spur and the Local CO-H2 Factor

Aims. Most models identify the X-ray bright North Polar Spur (NPS) with a hot interstellar (IS) bubble in the Sco-Cen star-forming region at approx. = to 130 pc. An opposite view considers the NPS as a distant structure associated with Galactic nuclear outflows. Constraints on the NPS distance can be obtained by comparing the foreground IS gas column inferred from X-ray absorption to the distribution of gas and dust along the line of sight. Absorbing columns towards shadowing molecular clouds simultaneously constrain the CO-H2 conversion factor. Methods. We derived the columns of X-ray absorbing matter N(sub Habs) from spectral fitting of dedicated XMM-Newton observations towards the NPS southern terminus (l(sup II) approx. = to 29 degrees, b(sup II) approx. = to +5 to +11 degrees). The distribution of the IS matter was obtained from absorption lines in stellar spectra, 3D dust maps and emission data, including high spatial resolution CO measurements recorded for this purpose. Results. N(sub Habs) varies from approx. = to 4.3 to approx. = to 1.3 x 10(exp 21) per sq cm along the 19 fields. Relationships between X-ray brightness, absorbing column and hardness ratio demonstrate a brightness decrease with latitude governed by increasing absorption. The comparison with absorption data, local and large-scale dust maps rules out a NPS near side closer than 300 pc. The correlation between N(sub Habs) and the reddening increases with the sightline length from 300 pc to 4 kpc and is the tightest with Planck tau(sub 353GHz) -based reddening, suggesting a much larger distance. N(H)/E(B-V)(sub tao) approx. = to 4.1 x 10(exp 21) per sq cm mag, close to Fermi-Planck determinations. N(sub Habs) absolute values are compatible with HI-CO clouds at -5 less than or equal to V(sub LSR) less than or equal to +25 to +45 km/s and a NPS potentially far beyond the Local Arm. A shadow cast by a b=+9 degree molecular cloud constrains X(sub CO) in that direction to less than or equal to 1.0 x 10(exp 20) sec/((sq cm)K km). The average X(sub CO) over the fields is less than or equal to 0.75 x 10(exp 20) sec/((sq cm)K km).

X-rays: ISM / radio lines: ISM / local insterstell↗
DOE OSTI2020

Materials Data on VB2 by Materials Project

VB2 is hexagonal omega structure structured and crystallizes in the hexagonal P6/mmm space group. The structure is three-dimensional. V is bonded to twelve equivalent B atoms to form a mixture of face and edge-sharing VB12 cuboctahedra. All V–B bond lengths are 2.30 Å. B is bonded in a 9-coordinate geometry to six equivalent V and three equivalent B atoms. All B–B bond lengths are 1.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V3B2 by Materials Project

V3B2 crystallizes in the tetragonal P4/mbm space group. The structure is three-dimensional. there are two inequivalent V2+ sites. In the first V2+ site, V2+ is bonded in a square co-planar geometry to four equivalent B3- atoms. All V–B bond lengths are 2.32 Å. In the second V2+ site, V2+ is bonded in a distorted hexagonal planar geometry to six equivalent B3- atoms. There are four shorter (2.27 Å) and two longer (2.28 Å) V–B bond lengths. B3- is bonded in a 9-coordinate geometry to eight V2+ and one B3- atom. The B–B bond length is 1.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V3B4 by Materials Project

V3B4 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are two inequivalent V2+ sites. In the first V2+ site, V2+ is bonded to twelve B+1.50- atoms to form a mixture of edge and face-sharing VB12 cuboctahedra. There are eight shorter (2.30 Å) and four longer (2.36 Å) V–B bond lengths. In the second V2+ site, V2+ is bonded in a 7-coordinate geometry to seven B+1.50- atoms. There are a spread of V–B bond distances ranging from 2.22–2.33 Å. There are two inequivalent B+1.50- sites. In the first B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to seven V2+ and two equivalent B+1.50- atoms. Both B–B bond lengths are 1.76 Å. In the second B+1.50- site, B+1.50- is bonded in a 9-coordinate geometry to six V2+ and three B+1.50- atoms. The B–B bond length is 1.73 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V2B3 by Materials Project

V2B3 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are two inequivalent V+4.50+ sites. In the first V+4.50+ site, V+4.50+ is bonded to twelve B3- atoms to form a mixture of edge and face-sharing VB12 cuboctahedra. There are a spread of V–B bond distances ranging from 2.30–2.36 Å. In the second V+4.50+ site, V+4.50+ is bonded in a 7-coordinate geometry to seven B3- atoms. There are a spread of V–B bond distances ranging from 2.21–2.32 Å. There are three inequivalent B3- sites. In the first B3- site, B3- is bonded in a 9-coordinate geometry to six equivalent V+4.50+ and three B3- atoms. There is two shorter (1.72 Å) and one longer (1.73 Å) B–B bond length. In the second B3- site, B3- is bonded in a 9-coordinate geometry to six V+4.50+ and three B3- atoms. Both B–B bond lengths are 1.76 Å. In the third B3- site, B3- is bonded in a 9-coordinate geometry to seven V+4.50+ and two equivalent B3- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on VB by Materials Project

VB1 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. V3+ is bonded in a 7-coordinate geometry to seven equivalent B3- atoms. There are a spread of V–B bond distances ranging from 2.24–2.33 Å. B3- is bonded in a 9-coordinate geometry to seven equivalent V3+ and two equivalent B3- atoms. Both B–B bond lengths are 1.79 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on V5B6 by Materials Project

V5B6 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are three inequivalent V+2.40+ sites. In the first V+2.40+ site, V+2.40+ is bonded in a 7-coordinate geometry to seven B2- atoms. There are a spread of V–B bond distances ranging from 2.24–2.33 Å. In the second V+2.40+ site, V+2.40+ is bonded in a 7-coordinate geometry to seven B2- atoms. There are a spread of V–B bond distances ranging from 2.22–2.33 Å. In the third V+2.40+ site, V+2.40+ is bonded to twelve B2- atoms to form a mixture of edge and face-sharing VB12 cuboctahedra. There are eight shorter (2.30 Å) and four longer (2.36 Å) V–B bond lengths. There are three inequivalent B2- sites. In the first B2- site, B2- is bonded in a 9-coordinate geometry to seven V+2.40+ and two equivalent B2- atoms. Both B–B bond lengths are 1.76 Å. In the second B2- site, B2- is bonded in a 9-coordinate geometry to six V+2.40+ and three B2- atoms. The B–B bond length is 1.73 Å. In the third B2- site, B2- is bonded in a 9-coordinate geometry to seven V+2.40+ and two equivalent B2- atoms. Both B–B bond lengths are 1.80 Å.

36 MATERIALS SCIENCE↗