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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 6E: Right ascension range 16h 00m to 19h 59m

The Einstein Observatory (HEAO-2 launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics, which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images. The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentation describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers, and data useful for calculating upper limits and fluxes.

Harris, D. E.↗
NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 7E: Right ascension range 20h 00m to 23h 59m

The Einstein Observatory (HEAO-2, launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images. The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentation describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers, and data useful for calculating upper limits and fluxes.

Harris, D. E.↗
NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 1E: Documentation

The Einstein Observatory (HEAO-2, launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics, which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images. The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentation describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers, and data useful for calculating upper limits and fluxes.

Harris, D. E.↗
NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 2E: Right ascension range 00h 00m to 03h 59m

The Einstein Observatory (HEAO-2, launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images. The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentation describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers and data useful for calculating upper limits and fluxes.

Harris, D. E.↗
NASA NTRS1993

The Einstein Observatory catalog of IPC x ray sources. Volume 3E: Right ascension range 04h 00m to 07h 59m

The Einstein Observatory (HEAO-2, launched November 13, 1978) achieved radically improved sensitivity over previous x-ray missions through the use of focusing optics which simultaneously afforded greatly reduced background and produced true images. During its 2.5-yr mission, the Einstein X-Ray Telescope was pointed toward some 5,000 celestial targets, most of which were detected, and discovered several thousand additional 'serendipitous' sources in the observed fields. This catalog contains contour diagrams and source data, obtained with the imaging proportional counter in the 0.16 to 3.5 keV energy band, and describes methods for recovering upper limits for any sky position within the observed images. The main catalog consists of six volumes (numbered 2 through 7) of right ascension ordered pages, each containing data for one observation. Along with the primary documentation describing how the catalog was constructed, volume 1 contains a complete source list, results for merged fields, a reference system to published papers and data useful for calculating upper limits and fluxes.

Harris, D. E.↗
NASA NTRS2010

Use of Reference Frames for Interplanetary Navigation at JPL

Navigation of interplanetary spacecraft is typically based on range, Doppler, and differential interferometric measurements made by ground-based telescopes. Acquisition and interpretation of these observations requires accurate knowledge of the terrestrial reference frame and its orientation with respect to the celestial frame. Work is underway at JPL to reprocess historical VLBI and GPS data to improve realizations of the terrestrial and celestial frames. Improvements include minimal constraint alignment, improved tropospheric modeling, better orbit determination, and corrections for antenna phase center patterns.

International Celestial Reference Frame (ICRF)↗
NASA NTRS1977

HEAO-A nominal scanning observation schedule

The HEAO-A observatory, scheduled for launch in late June 1977, will spend most of its orbital lifetime in a scanning mode, spining from 0.03 to 0.1 rpm about an axis aligned with the sun. The dates of availability in the scan band are given for a list of 248 X-ray sources. Celestial maps of source locations and scan planes, and examples of the nighttime elevation of available sources are presented. This document is intended to aid ground-based observers in planning coordinated observations with HEAO-A.

Fishman, G. J.↗
NASA NTRS2011

Observation of Anisotropy in the Galactic Cosmic Ray Arrival Directions at 400 TEV With IceCube

In this paper we report the first observation in the Southern hemisphere of an energy dependence in the Galactic cosmic ray anisotropy up to a few hundred TeV. This measurement was performed using cosmic ray induced muons recorded by the partially deployed IceCube observatory between May 2009 and May 2010. The data include a total of 33x l0(epx 9) muon events with a median angular resolution of approx 3 degrees. A sky map of the relative intensity in arrival direction over the Southern celestial sky is presented for cosmic ray median energies of 20 and 400 Te V. The same large-scale anisotropy observed at median energies around 20 TeV is not present at 400 TeV. Instead, the high energy skymap shows a different anisotropy structure including a deficit with a post-trial significance of -6.30 sigma. This anisotropy reveals a new feature of the Galactic cosmic ray distribution, which must be incorporated into theories of the origin and propagation of cosmic rays.

Abbasi, R.↗
NASA NTRS2004

Extending the ICRF to Higher Radio Frequencies: 24 and 43 GHz Astrometry

We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-band) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

Jacobs, Christopher S.↗
NASA NTRS2004

Extending the ICRF to Higher Radio Frequencies: Imaging and Source Structure

We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-braid) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.

Boboltz, David A.↗
NASA NTRS2015

Aquarius L-Band Radiometers Calibration Using Cold Sky Observations

An important element in the calibration plan for the Aquarius radiometers is to look at the cold sky. This involves rotating the satellite 180 degrees from its nominal Earth viewing configuration to point the main beams at the celestial sky. At L-band, the cold sky provides a stable, well-characterized scene to be used as a calibration reference. This paper describes the cold sky calibration for Aquarius and how it is used as part of the absolute calibration. Cold sky observations helped establish the radiometer bias, by correcting for an error in the spillover lobe of the antenna pattern, and monitor the long-term radiometer drift.

Aquarius↗
NASA NTRS1989

Autonomous star referenced attitude determination

A general star pattern recognition algorithm has been used to develop JPL's redundant, microcomputer-equipped ASTROS II CCD star tracker into a full-sky autonomous star tracker (FAST), capable of determining its attitude about all three axes without requiring any a priori attitude knowledge. A large field of view allows the number of guide stars in the all-sky data-base of the tracker to be limited to a manageable number, while high accuracy ensures that the pattern formed by the observed guide stars is unique. The recognition algorithm can also be used for automating the acquisition of celestial targets by astronomy telescopes, for autonomously updating the attitude of gyro-based attitude control systems, and for automating ground-based attitude recognition. Using both Monte Carlo simulations and a quasi-analytical method, it is shown that the general recognition algorithm and a less software-intensive special algorithm can be used to reliably automate the acquisition of celestial targets by astronomy telescopes.

Van Bezooijen, R. W. H.↗
NASA NTRS1993

The Ultraviolet Plume Instrument (UVPI)

The Ultraviolet Plume Instrument (UVPI) was launched aboard the Low-power Atmospheric Compensation Experiment (LACE) satellite on 14 Feb. 1990. Both the spacecraft and the UVPI were sponsored by the Directed Energy Office of the Strategic Defense Initiative Organization. The mission of the UVPI was to obtain radiometrically calibrated images of rocket plumes at high altitude and background image data of the Earth, Earth's limb, and celestial objects in the near- and middle-UV wave bands. The UVPI was designed for nighttime observations, i.e., to acquire and track relatively bright objects against a dark background.

Horan, D. M.↗
NASA NTRS1985

The determination of physical and dynamical parameters of Pluto/Charon and binary asteroids by least-square formation of a matched filter for a time series of images. I - The operational theory

A theory is derived for the determination of the masses, radii, and orbital elements of the Pluto/Charon, or similar, system based on the prediction of an image distribution over space and time and its comparison with observation. The comparison may be ultimately through the theory of least squares or the application of a matched filter to the observations as a three-dimensional signal stream at an initial or intermediate state. The theory is an approximation correct to fifth order in the diameters of celestial bodies. The theory of astronomical seeing that is used is based on Kolmogorov turbulence in the long-exposure limit. The images must be photometric. Linear tracking errors that can be removed are preferable to either automatic or manual guiding, in the collection of candidate observations.

Wildey, R. L.↗
NASA NTRS1985

A VLBI survey at 2.29 GHz

The Deep Space Network (DSN) is establishing a high-accuracy VLBI celestial reference frame. The results of a search for suitable radio sources to be used in constructing this frame are given. The VLBI observations using DSN baselines at 2.29 GHz with fringe spacings of about 3 milliarcseconds have been performed on 1398 radio sources spread over the entire sky. Of those, 917 sources were detected including 93% of the identifed BL Lacertae objects, 86% of Quasars and 36% of galaxies. The resulting catalog of compact radio sources is also useful for various astrophysical studies and in the formation of VLBI celestial reference frames.

Morabito, D. D.↗
DOE OSTI2024

Overview of the distributed image processing infrastructure to produce the Legacy Survey of Space and Time

The Vera C. Rubin Observatory is preparing to execute the most ambitious astronomical survey ever attempted, the Legacy Survey of Space and Time (LSST). Currently the final phase of construction is under way in the Chilean Andes, with the Observatory’s ten-year science mission scheduled to begin in 2025. Rubin’s 8.4-meter telescope will nightly scan the southern hemisphere collecting imagery in the wavelength range 320–1050 nm covering the entire observable sky every 4 nights using a 3.2 gigapixel camera, the largest imaging device ever built for astronomy. Automated detection and classification of celestial objects will be performed by sophisticated algorithms on high-resolution images to progressively produce an astronomical catalog eventually composed of 20 billion galaxies and 17 billion stars and their associated physical properties. In this article we present an overview of the system currently being constructed to perform data distribution as well as the annual campaigns which reprocess the entire image dataset collected since the beginning of the survey. These processing campaigns will utilize computing and storage resources provided by three Rubin data facilities (one in the US and two in Europe). Each year a Data Release will be produced and disseminated to science collaborations for use in studies comprising four main science pillars: probing dark matter and dark energy, taking inventory of solar system objects, exploring the transient optical sky and mapping the Milky Way. Also presented is the method by which we leverage some of the common tools and best practices used for management of large-scale distributed data processing projects in the high energy physics and astronomy communities. We also demonstrate how these tools and practices are utilized within the Rubin project in order to overcome the specific challenges faced by the Observatory.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1979

A large-beam sky survey at millimeter and submillimeter wavelengths made from balloon altitudes

A survey has been made of a quarter of the celestial sphere from balloon altitudes with a telescope having a 1.6-deg beamwidth and two spectral bands: 3-10 kaysers and 10-25 kaysers. The limiting sensitivity of the survey was 10,000 Jy. The galactic disk was detected from 358 to 45 deg galactic longitude. The total far-infrared flux from several regions on the galactic plane measured in this survey is 5-10 times larger than that observed by others using smaller beamwidths and small-amplitude spatial chopping, indicating that a substantial part of the emission comes from extended sources. Two other extended sources were also observed, one in the Cygnus region and the other a spur running off the galactic plane at 130 deg galactic longitude toward the north celestial pole. In addition, lower limits for the spectral index of interstellar dust emission are presented.

Owens, D. K.↗