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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Determining Stellar Elemental Abundances from DESI Spectra with the Data-driven Payne

Abstract Stellar abundances for a large number of stars provide key information for the study of Galactic formation history. Large spectroscopic surveys such as the Dark Energy Spectroscopic Instrument (DESI) and LAMOST take median-to-low-resolution (R≲ 5000) spectra in the full optical wavelength range for millions of stars. However, the line-blending effect in these spectra causes great challenges for elemental abundance determination. Here we employDD-Payne, a data-driven method regularized by differential spectra from stellar physical models, to the DESI early data release spectra for stellar abundance determination. Our implementation delivers 15 labels, including effective temperatureT eff , surface gravity log g , microturbulence velocityv mic , and the abundances for 12 individual elements, namely C, N, O, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, and Ni. Given a spectral signal-to-noise ratio of 100 per pixel, the internal precisions of the label estimates are about 20 K forT eff , 0.05 dex for log g , and 0.05 dex for most elemental abundances. These results agree with the theoretical limits from the Crámer–Rao bound calculation within a factor of 2. The majority of the accreted halo stars contributed by the Gaia–Enceladus–Sausage are discernible from the disk and in situ halo populations in the resultant [Mg/Fe]–[Fe/H] and [Al/Fe]–[Fe/H] abundance spaces. We also provide distance and orbital parameters for the sample stars, which spread over a distance out to ∼100 kpc. The DESI sample has a significantly higher fraction of distant (or metal-poor) stars than the other existing spectroscopic surveys, making it a powerful data set for studying the Galactic outskirts. The catalog is publicly available.

Astronomy & Astrophysics↗
DOE OSTI2025

The Cocytos Stream: A Disrupted Globular Cluster from our Last Major Merger?

The census of stellar streams and dwarf galaxies in the Milky Way provides direct constraints on galaxy formation models and the nature of dark matter. The DESI Milky Way survey (with a footprint of 14,000$~deg{^2}$ and a depth of $r<19$ mag) delivers the largest sample of distant metal-poor stars compared to previous optical fiber-fed spectroscopic surveys. This makes DESI an ideal survey to search for previously undetected streams and dwarf galaxies. We present a detailed characterization of the Cocytos stream, which was re-discovered using a clustering analysis with a catalog of giants in the DESI year 3 data, supplemented with Magellan/MagE spectroscopy. Our analysis reveals a relatively metal-rich ([Fe/H]$=-1.3$) and thick stream (width$=1.5^\circ$) at a heliocentric distance of $\approx 25$ kpc, with an internal velocity dispersion of 6.5-9 km s$^{-1}$. The stream's metallicity, radial orbit, and proximity to the Virgo stellar overdensities suggest that it is most likely a disrupted globular cluster that came in with the Gaia-Enceladus merger. We also confirm its association with the Pyxis globular cluster. Our result showcases the ability of wide-field spectroscopic surveys to kinematically discover faint disrupted dwarfs and clusters, enabling constraints on the dark matter distribution in the Milky Way.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1980

The role of World Data Centers and the Lunar and Planetary Institute in the international exchange of lunar and planetary data

The success of many lunar and planetary investigations has resulted in the accumulation of a mass of data in a myriad of formats and medias. The application of these data to comparative planetology, origin of the solar system, and potential industrial applications of space has made it necessary for scientists from many disciplines to have access to the data. The collections of these data are so diverse that it is often difficult to select what is needed based on catalog information alone. The Lunar and Planetary Institute (LPI) proposes to bring the user and the data together. As a research support organization operated by the Universities Space Research Association, the LPI through its active Visiting Scientist Program, a balanced program of study workshops and topical conferences, and organized and supervised data collections has assisted scientists, educators, and students to review, study, and obtain the data necessary to the pursuit of their research.

Waranius, F. B.↗
NASA NTRS1980

Case study: Lockheed-Georgia Company integrated design process

A case study of the development of an Integrated Design Process is presented. The approach taken in preparing for the development of an integrated design process includes some of the IPAD approaches such as developing a Design Process Model, cataloging Technical Program Elements (TPE's), and examining data characteristics and interfaces between contiguous TPE's. The implementation plan is based on an incremental development of capabilities over a period of time with each step directed toward, and consistent with, the final architecture of a total integrated system. Because of time schedules and different computer hardware, this system will not be the same as the final IPAD release; however, many IPAD concepts will no doubt prove applicable as the best approach. Full advantage will be taken of the IPAD development experience. A scenario that could be typical for many companies, even outside the aerospace industry, in developing an integrated design process for an IPAD-type environment is represented.

Waldrop, C. T.↗
NASA NTRS1986

Relationships between dust grain components responsible for observed interstellar extinction and polarization

Ultraviolet extinction properties of interstellar dust are well observed. The amount of extinction measured in the visible (E(B-V)), at the 2200 A feature (E(BUMP)), and in the far ultraviolet (E(1550-V)) are only vaguely correlated indicating that at least 3 fairly independent populations of grains contribute to the overall extinction curve. A search of literature was made for polarimetric observations of the 1415 stars included in the extinction catalog derived from the Astronomical Netherlands Satellite (ANS) data. It was found that about 900 of the stars had at least one unfiltered polarimetric observation, p (%). In addition, 150 stars had calculated values of lambda sub max (wavelength at which maximum polarization occurs). The lambda sub max and p/E(B-V) parameters are discussed.

Clayton, G. C.↗
NASA NTRS1988

Deep space target location with Hubble Space Telescope (HST) and Hipparcos data

Interplanetary spacecraft navigation requires accurate a priori knowledge of target positions. A concept is presented for attaining improved target ephemeris accuracy using two future Earth-orbiting optical observatories, the European Space Agency (ESA) Hipparcos observatory and the Nasa Hubble Space Telescope (HST). Assuming nominal observatory performance, the Hipparcos data reduction will provide an accurate global star catalog, and HST will provide a capability for accurate angular measurements of stars and solar system bodies. The target location concept employs HST to observe solar system bodies relative to Hipparcos catalog stars and to determine the orientation (frame tie) of these stars to compact extragalactic radio sources. The target location process is described, the major error sources discussed, the potential target ephemeris error predicted, and mission applications identified. Preliminary results indicate that ephemeris accuracy comparable to the errors in individual Hipparcos catalog stars may be possible with a more extensive HST observing program. Possible future ground and spacebased replacements for Hipparcos and HST astrometric capabilities are also discussed.

Null, George W.↗
NASA NTRS1992

Satellite situation report, volume 32, no. 4

This report consists of data computed at the U.S. Space Command, GSFC, or provided by satellite owners. A space objects box score table is presented with data under the following headings: source/organization, objects in orbit, and decayed objects. The objects in orbit and decayed objects headings have payload, debris, and total as subheadings. The bulk of the document is objects-in-orbit tables with data under the following headings: international designation, name, catalog number, source, launch date, period minutes, inclination, apogee (km), perigee (km), and notes.

Source record↗
NASA NTRS1993

The Extreme Ultraviolet Explorer archive

The objectives and data products of the EUVE public archive, created to handle the storage, maintenance, and distribution of EUVE data and ancillary documentation, information, and software, are briefly reviewed. Archive data products presently include calibration target spectra, a catalog of past and future calibration targets, the EUVE Bright Source List, extreme ultraviolet skymaps and images of extended sources, a list of approved guest observer targets, a bibliography of EUVE publications, and C routines to calculate interstellar medium transmission at EUV wavelengths.

Polomski, E.↗
NASA NTRS1992

Satellite situation report, volume 32, no. 1

This report consists of data computed at the U.S. Space Command, GSFC, or provided by satellite owners. A space objects box score table is presented with data under the following headings: source/organization, objects in orbit, and decayed objects. The objects in orbit and decayed objects headings have payload, debris, and total as subheadings. The bulk of the document is objects-in-orbit tables with data under the following headings: international designation, name, catalog number, source, launch date, period minutes, inclination, apogee (km), perigee (km), and notes.

Source record↗
NASA NTRS1992

Satellite situation report, volume 32, no. 2

This report consists of data computed at the U.S. Space Command, GSFC, or provided by satellite owners. A space objects box score table is presented with data under the following headings: source/organization, objects in orbit, and decayed objects. The objects in orbit and decayed objects headings have payload, debris, and total as subheadings. The bulk of the document is objects-in-orbit tables with data under the following headings: international designation, name, catalog number, source, launch date, period minutes, inclination, apogee (km), perigee (km), and notes.

Source record↗
NASA NTRS1991

Satellite situation report, volume 31, no. 4

This report consists of data computed at the U.S. Space Command, GSFC, or provided by satellite owners. A space objects box score table is presented with data under the following headings: source/organization, objects in orbit, and decayed objects. The objects in orbit and decayed objects headings have payload, debris, and total as subheadings. The bulk of the document is objects-in-orbit tables with data under the following headings: international designation, name, catalog number, source, launch date, period minutes, inclination, apogee (km), perigee (km), and notes.

Source record↗
NASA NTRS1993

Satellite situation report, volume 33, no. 3

This report consists of data computed at the U.S. Space Command, GSFC, or provided by satellite owners. A space objects box score table is presented with data under the following headings: source/organization, objects in orbit, and decayed objects. The objects in orbit and decayed objects headings have payload, debris, and total as subheadings. The bulk of the document is objects-in-orbit tables with data under the following headings: international designation, name, catalog number, source, launch date, period minutes, inclination, apogee (km), perigee (km), and notes.

Source record↗
NASA NTRS1993

Satellite situation report, volume 33, number 2

This report consists of data computed at United States Space Command, GFSC, or provided by satellite owners. A space objects box score table is presented with data under the following headings: source/organization, objects in orbit, and decayed objects. The objects in orbit and decayed objects' headings have payload, debris, and total as subheadings. The bulk of the document is objects in orbit tables with data under the following headings: international designation, name, catalog number, source, launch date, period minutes, inclination, apogee (km), perigee (km) and notes.

Source record↗
NASA NTRS1994

On the nature of gamma-ray burst time dilations

The recent discovery that faint gamma-ray bursts are stretched in time relative to bright ones has been interpreted as support for cosmological distances: faint bursts have their durations redshifted relative to bright ones. It was pointed out, however, that the relative time stretching can also be produced by an intrinsic correlation bewteen duration and luminosity of gamma-ray bursts in a nearby, bounded distribution. While both models can explain the average amount of time stretching, we find a difference between them in the way the duration distribution of faint bursts deviates from that of bright ones, assuming the luminosity function of gamma-ray bursts is independent of distance. This allows us to distinguish between these two broad classes of model on the basis of the duration distributions of gamma-ray bursts, leading perhaps to an unambiguous determination of the distance scale of gamma-ray bursts. We apply our proposed test to the second Burst and Transient Source Experiment (BATSE) catalog and conclude, with some caution, that the data favor a cosmological interpretation of the time dilation.

Wijers, Ralph A. M. J.↗
NASA NTRS2000

Astrometry of the omega Centauri Hubble Space Telescope Calibration Field

Astrometry, on the International Celestial Reference Frame (epoch J2000.0), is presented for the Walker (1994, PASP, 106, 828) stars in the omega Centauri (=NGC 5139=C 1323-1472) Hubble Space Telescope Wide Field/Planetary Camera (WF/PC) calibration field of Harris et al. (1993, AJ, 105, 1196). Harris et al. stars were first identified on a WFPC2 observation of the omega Cen HST calibration field. Relative astrometry of the Walker stars in this field was then obtained using Walker's CCD positions and astrometry derived using the STSDAS METRIC task on the positions of the Harris et al. stars on the WFPC2 observation. Finally, the relative astrometry, which was based on the HST Guide Star Catalog, is placed on the International Celestial Reference Frame with astrometry from the USNO-A2.0 catalog. An ASCII text version of the astrometric data of the Walker stars in the omega Cen HST calibration field is available electronically in the online version of the article.

Mighell, Kenneth J.↗
NASA NTRS2015

NASA Conjunction Assessment Organizational Approach and the Associated Determination of Screening Volume Sizes

NASA is committed to safety of flight for all of its operational assets Performed by CARA at NASA GSFC for robotic satellites Focus of this briefing Performed by TOPO at NASA JSC for human spaceflight he Conjunction Assessment Risk Analysis (CARA) was stood up to offer this service to all NASA robotic satellites Currently provides service to 70 operational satellites NASA unmanned operational assets Other USG assets (USGS, USAF, NOAA) International partner assets Conjunction Assessment (CA) is the process of identifying close approaches between two orbiting objects; sometimes called conjunction screening The Joint Space Operations Center (JSpOC) a USAF unit at Vandenberg AFB, maintains the high accuracy catalog of space objects, screens CARA-supported assets against the catalog, performs OD tasking, and generates close approach data.

Conjunction↗
NASA NTRS1994

The analysis of star catalogs. 2: An intercomparison among the GC, the N30, and the FK5(B1950.0/FK4)

We use the general method of compiled data set analysis developed in our first paper (Bucciarelli et. al. 1994) and extend our analysis of fundamental star catalogs to include the two American ones. The problems found in the FK3/FK4/FK5 sequence are not present in either the GC or the N30. This lends support to the hypothesis advanced in our previous paper that the FK3, and to a lesser extent the FK4 declination system, are distorted by high angular frequency systematics. On the other hand, both the GC and N30 equatorial coordinate and proper motion distributions nicely follow the predictions of mathematical statistics. As with the FK3/FK4/FK5 analysis, the new results are as seen by the FK5 (on the FK4/B1950.0 system).

Taff, L. G.↗