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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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NASA NTRS2021

Pointing Error Budget Development and Methodology on the Psyche Project

The Psyche mission was selected by NASA as the 14th mission in the Discovery Program in 2017. The Psyche spacecraft utilizes solar electric propulsion, and will journey to the asteroid (16) Psyche during a 3.5 year trajectory after its planned 2022 launch. The spacecraft instrument suite includes a magnetometer, a multispectral imager, a gamma ray neutron spectrometer, and an X-band radio telecommunications system. It also includes the Deep Space Optical Communication technical demonstration. These instruments along with other spacecraft components require pointing accuracy to meet their scientific and engineering performance requirements. Early on in the project development, the team established a methodology by which pointing accuracy (knowledge and control) is analyzed against the system requirements by means of pointing error budgets and requirement allocations. A margin policy was implemented to ensure the instrument and engineering component pointing accuracy requirements will be met during verification and in flight. Psyche’s pointing management framework defines detailed rationales for the system and subsystem error allocations of the top level pointing accuracy requirements, with sufficient project level pointing margin, and supports end-to-end pointing requirement verification. This paper will present an overview of the Psyche project’s pointing error budget development process, and discuss the rationale behind the methodology. Psyche’s pointing budget methodology integrates best practices and lessons learned from heritage missions, while focusing on the specific needs of the Psyche spacecraft and its science instruments. Key challenges in the pointing error budget development will be reviewed, and a deep dive into two key Psyche pointing budgets are presented. The systems engineering of Psyche’s pointing budget methodology outlined in this paper will serve as a resource for future deep space missions.

Lai, Peter↗
NASA NTRS1994

The vertical structure and stability of accretion disks surrounding black holes and neutron stars

The structure and stability of the inner regions of accretion disks surrounding neutron stars and black holes have been investigated. Within the framework of the alpha viscosity prescription for optically thick disks, we assume the viscous stress scales with gas pressure only, and the alpha parameter, which is less than or equal to unity, is formulated as alpha(sub 0)(h/r)(exp n), where h is the local scale height and n and alpha(sub 0) are constants. We neglect advective energy transport associated with radial motions and construct the vertical structure of the disks by assuming a Keplerian rotation law and local hydrostatic and thermal equilibrium. The vertical structures have been calculated with and without convective energy transport, and it has been demonstrated that convection is important especially for mass accretion rates, M-dot, greater than about 0.1 times the Eddington value, M-dot(sub Edd). Although the efficiency of convection is not high, convection significantly modifies the vertical structure of the disk (as compared with a purely radiative model) and leads to lower temperatures at a given M-dot. The results show that the disk can be locally unstable and that for n greater than or = 0.75, an S-shaped relation can exist between M-dot and the column density, sigma, at a given radius. While the lower stable branch (derivative of M-dot/derivative of sigma greater than 0) and middle unstable branch (derivative of M-dot/derivative of sigma less than 0) represent structures for which the gas and radiation pressure dominate respectively, the stable upper branch (derivative of M-dot/derivative of sigma greater than 0) is a consequence of the saturation of alpha. This saturation of alpha can occur for large alpha(sub 0) and at M-dot less than or = M-dot(sub Edd). The instability is found to occur at higher mass accretion rates for neutron stars than for black holes. In particular, the disk is locally unstable for M-dot greater than or = 0.5 M-dot(sub Edd) for neutron stars and for M-dot greater than or = M-dot(sub Edd) for black holes for a viscosity prescription characterized by n = 1 and alpha(sub 0) = 10.

Milsom, J. A.↗
NASA NTRS1991

New constraints on neutron star models of gamma-ray bursts. II - X-ray observations of three gamma-ray burst error boxes

Exosat observations are presented for 3 gamma-ray-burst error boxes, one of which may be associated with an optical flash. No point sources were detected at the 3-sigma level. A comparison with Einstein data (Pizzichini et al., 1986) is made for the March 5b, 1979 source. The data are interpreted in the framework of neutron star models and derive upper limits for the neutron star surface temperatures, accretion rates, and surface densities of an accretion disk. Apart from the March 5b, 1979 source, consistency is found with each model.

Boer, M.↗
NASA NTRS1978

Orbital elements of 4U 0115+63 and the nature of the hard X-ray transients

Extended SAS 3 timing observations of the hard transient X-ray source 4U 0115+63 are reported, and a definitive measurement of the binary orbit of this transient source is presented. It is shown that this source is in a long orbit (period of approximately 24.3 days) that is moderately eccentric (e about 0.34) and that the mean value of the rate of decrease of the pulse period is consistent with the expected spinup of a rotating neutron star that is accreting from a disk. A distance of about 2.5 kpc is inferred, and the B-star optical counterpart is estimated to have an absolute magnitude of approximately -1.5 and a mass of at least 5 solar masses. It is suggested that the companion is a Be star which does not fill its Roche lobe and that the eccentricity and transient nature of the source result from the large orbital separation. It is proposed that hard X-ray transients as a class are collapsed stars (perhaps all neutron stars) in binary systems that are substantially wider than the more persistent X-ray binaries and that the large orbital separation, the small radius of the companion, or both, result in episodic rather than continuous mass transfer onto the X-ray star.

Rappaport, S.↗
NASA NTRS1986

Comets, X-ray bursts, and gamma-ray bursts

The proposal, revived by Tremaine and Zytkow (1985), that accretion of comets by neutron stars may be the origin of gamma-ray bursts is considered. This mechanism has difficulty accounting for the observed gamma-ray spectrum and optical counterparts of the bursts. The survival of comets near supernovae is investigated. Ablation rates and the thermal structure of an ablating surface layer are calculated. In some circumstances, mechanical disruption will erode a comet more rapidly than evaporation. The accretion of comets by neutron stars may produce a class of X-ray burst sources with novel properties.

Katz, J. I.↗
NASA NTRS2013

Using ISS Telescopes for Electromagnetic Follow-up of Gravitational Wave Detections of NS-NS and NS-BH Mergers

The International Space Station offers a unique platform for rapid and inexpensive deployment of space telescopes. A scientific opportunity of great potential later this decade is the use of telescopes for the electromagnetic follow-up of ground-based gravitational wave detections of neutron star and black hole mergers. We describe this possibility for OpTIIX, an ISS technology demonstration of a 1.5 m diffraction limited optical telescope assembled in space, and ISS-Lobster, a wide-field imaging X-ray telescope now under study as a potential NASA mission. Both telescopes will be mounted on pointing platforms, allowing rapid positioning to the source of a gravitational wave event. Electromagnetic follow-up rates of several per year appear likely, offering a wealth of complementary science on the mergers of black holes and neutron stars.

NS-NS and NS-BH mergers↗
NASA NTRS1983

X-rays from radio pulsars - The detection of PSR 1055-52

The short-period pulsar PSR 1055-52 has been detected as a soft X-ray source in the course of an Einstein Observatory survey of radio pulsars. Its X-ray to radio luminosity ratio is about 10,000, although the X-rays are not modulated at the neutron star's rotation frequency. High spatial resolution observations suggest that a significant fraction of the emission comes from an extended region surrounding the pulsar. Several possible scenarios for the origin of both point and extended X-ray emission from isolated neutron stars are investigated: radiation from the hot stellar surface, from hot polar caps, and from an optically thick atmosphere, as well as from a circumstellar nebula emitting thermal bremsstrahlung or synchrotron radiation. It is concluded that the spatial, spectral, and temporal characteristics of this source are most consistent with a model in which relativistic particles generated by the pulsar are radiating synchrotron X-rays in the surrounding magnetic field; i.e., that PSR 1055 is embedded in a mini-Crab nebula. Observational tests of this hypothesis are suggested, and the implications of this result for pulsar evolution are briefly discussed.

Cheng, A. F.↗
NASA NTRS2011

An Unusual Stellar Death on Christmas Day

Long Gamma-Ray Bursts (GRBs) are the most dramatic examples of massive stellar deaths, usually associated with supernovae. They release ultra-relativistic jets producing non-thermal emission through synchrotron radiation as they interact with the surrounding medium. Here we report observations of the peculiar GRB 101225A (the "Christmas burst"). Its gamma-ray emission was exceptionally long and followed by a bright X-ray transient with a hot thermal component and an unusual optical couuterpart. During the first 10 days, the optical emission evolved as an expanding, cooling blackbody after which an additional component, consistent with a faint supernova, emerged. We determine its distance to 1.6 Gpc by fitting the spectral-energy distribution and light curve of the optical emission with a GRB-supernova template. Deep optical observations may have revealed a faint, unresolved host galaxy. Our proposed progenitor is a helium star-neutron star merger that underwent a common envelope phase expelling its hydrogen envelope. The resulting explosion created a GRB-like jet which gets thermalized by interacting with the dense, previously ejected material and thus creating the observed black-body, until finally the emission from the supernova dominated. An alternative explanation is a minor body falling onto a neutron star io the Galaxy

Thone, C. C.↗
NASA NTRS1986

Simultaneous X-ray and optical observations of GX 339-4 in an X-ray high state

Optical emission, soft X-rays, and hard X-rays have been observed simultaneously from the black hole candidate GX 3339-4 in a typical high state. Each of these components is interpreted as arising from a characteristic region of the accretion disk. Considered as a black hole, GX 339-4 lacks the variable 2 keV blackbody component that would be emitted from the 'solid' surface of a neutron star in the low-mass neutron star binaries. The X-ray emission in the high state is therefore extremely soft and stable in time. The intermediate disk region is optically thick and geometrically thin. The observed soft X-ray component with a 'disk blackbody' spectrum comes from this region. The innermost disk region is dynamically unstable due to the effect of general relativity and possibly due to radiation pressure. This region is responsible for the generation of the hard X-ray tail through Comptonization.

Makishima, K.↗
NASA NTRS1974

Measurement of capsule heat transfer gaps using neutron radiography

A technique is described for measuring heat transfer gaps from neutron radiographs. The method involves scanning the radiograph negative with a recording microdensitometer to obtain a trace of the optical density variation across the diameter of the capsule. The optical density change representing the gap is measured from the microdensitometer trace and related to the physical measurement. Heat transfer gaps from 0.061 to 0.178 cm have been determined by this technique and agree with preassembly physical measurements to plus or minus 0.005 cm.

Thaler, L. A.↗
NASA NTRS1988

Supernova 1987A

Supernova 1987A (February 23, 1987) in the Large Magellanic Cloud is the brightest supernova to be observed since SN 1604 AD (Kepler). Detection of a burst of neutrinos indicates that a neutron star was formed. Radioactive decay of about 0.07 solar mass of Co-56 is responsible for the observed optical light as well as hard X-rays and gamma-ray lines. Ultraviolet, optical, and infrared 'light echoes' and soft X-rays provide information on the distribution of circumstellar matter and the evolution of the progenitor star.

Mccray, Richard↗
NASA NTRS2011

Numerical Solution of the Radiative Transfer Equation: X-Ray Spectral Formation from Cylindrical Accretion onto a Magnetized Neutron Star

Predicting the emerging X-ray spectra in several astrophysical objects is of great importance, in particular when the observational data are compared with theoretical models. This requires developing numerical routines for the solution of the radiative transfer equation according to the expected physical conditions of the systems under study. Aims. We have developed an algorithm solving the radiative transfer equation in the Fokker-Planck approximation when both thermal and bulk Comptonization take place. The algorithm is essentially a relaxation method, where stable solutions are obtained when the system has reached its steady-state equilibrium. Methods. We obtained the solution of the radiative transfer equation in the two-dimensional domain defined by the photon energy E and optical depth of the system pi using finite-differences for the partial derivatives, and imposing specific boundary conditions for the solutions. We treated the case of cylindrical accretion onto a magnetized neutron star. Results. We considered a blackbody seed spectrum of photons with exponential distribution across the accretion column and for an accretion where the velocity reaches its maximum at the stellar surface and at the top of the accretion column, respectively. In both cases higher values of the electron temperature and of the optical depth pi produce flatter and harder spectra. Other parameters contributing to the spectral formation are the steepness of the vertical velocity profile, the albedo at the star surface, and the radius of the accretion column. The latter parameter modifies the emerging spectra in a specular way for the two assumed accretion profiles. Conclusions. The algorithm has been implemented in the XPEC package for X-ray fitting and is specifically dedicated to the physical framework of accretion at the polar cap of a neutron star with a high magnetic field (approx > 10(exp 12) G). This latter case is expected to be of typical accreting systems such as X-ray pulsars and supergiant fast X ray transients.

Fairnelli, R.↗
NASA NTRS1984

Einstein observations of the Crab nebula pulsar

Einstein Observatory (HEAO 2) high-resolution (approximately 4 sec) images of the Crab nebula which clearly resolve the pulsar from the diffuse X-ray emission are presented. The pulsar contributes 3.9 + or - 0.2 percent of the observed 0.1-4.5 keV flux and shows no evidence (other than the 33 ms pulsations) for variations on time scales up to approximately 2.3 days. The pulsar flux decreases to zero over about one-eighth of the cycle, with the upper limit to point source emission during this interval implying a blackbody surface temperature of less than 2.5 x 10 to the 6th K for the neutron star (10 km assumed radius). The spatial distribution of nebular emission near the pulsar closely resembles that of the optical continuum.

Harnden, F. R., Jr.↗
NASA NTRS1988

Supernova 1987A in the Large Magellanic Cloud; Proceedings of the Fourth George Mason Astrophysics Workshop, George Mason University, Fairfax, VA, Oct. 12-14, 1987

Papers concerning SN 1987A are presented, covering topics such as images and spectrograms of the SN 1987A progenitor, a linear polarimetric study of SN 1987A, the energetics, nature, and uniqueness of the supernova, comparison of the SN 1987A light curve with other type II supernovae, P-Cygni features and photospheric velocities, the neutrino burst from SN 1987A, mass determination of neutrinos, neutrino transport, energetics, and oscillations. Additional papers discuss supernovae light echoes, the UV interstellar spectrum of SN 1987A, theoretical models of SN 1987A, circumstellar and interstellar interaction, the supernova as a stripped asymptotic-branch giant in a binary system, pulsar formation and the fall back mass fraction, the signals of particle acceleration at SN 1987A, the effects of the mixing of the ejecta on the hard X-ray emissions from the supernova, possible s-process gamma-ray lines in supernovae, detectability of early thermal radiation from a neutron star in SN 1987A, NASA studies of the supernova, and information exchange for SN 1987A. Observational studies presented include optical, IR, radio, and UV observations, IR speckle-interferometry, coded mask X-ray observations, broad band X-ray imaging spectrophotometry, gamma-ray and thermal X-ray observations, and reports from several observatories.

Kafatos, Minas↗
NASA NTRS2003

Mathematical Investigation of Gamma Ray and Neutron Absorption Grid Patterns for Homeland Defense Related Fourier Imaging Systems

Terrorist suitcase nuclear devices typically using converted Soviet tactical nuclear warheads contain several kilograms of plutonium. This quantity of plutonium emits a significant number of gamma rays and neutrons as it undergoes radioactive decay. These gamma rays and neutrons normally penetrate ordinary matter to a significant distance. Unfortunately this penetrating quality of the radiation makes imaging with classical optics impractical. However, this radiation signature emitted by the nuclear source may be sufficient to be imaged from low-flying aerial platforms carrying Fourier imaging systems. The Fourier imaging system uses a pair of co-aligned absorption grids to measure a selected range of spatial frequencies from an object. These grids typically measure the spatial frequency in only one direction at a time. A grid pair that looks in all directions simultaneously would be an improvement over existing technology. A number of grid pairs governed by various parameters were investigated to solve this problem. By examining numerous configurations, it became apparent that an appropriate spiral pattern could be made to work. A set of equations was found to describe a grid pattern that produces straight fringes. Straight fringes represent a Fourier transform of a point source at infinity. An inverse Fourier transform of this fringe pattern would provide an accurate image (location and intensity) of a point source.

Boccio, Dona↗
NASA NTRS2004

Lunar and Planetary Science XXXV: The Future of Mars Surface Exploration

The session The Future of Mars Surface Exploration includes the following topics: 1) High Resolution Laser Scanning Techniques for Rock Abrasion and Texture Analyses on Mars and Earth; 2) Definitive Mineralogical Analysis of Mars Analog Rocks Using the CheMin XRD/XRF Instrument; 3) Quantitative Mineralogical Analysis of Mars Analogues Using CHEMIN Data and Rietveld Refinement; 4) In Situ Analytical Strategy for Mars Combining X-Ray and Optical Techniques; 5) In-Situ Dating on Mars: The Potential of OSL Dating; 6) Experiment of Dynamic Albedo of Neutrons (DAN): Searching for Water-rich Spots from the Rover on the Surface of Mars; and 7) Developing an Automated Science Analysis System for Mars Surface Exploration for MSL and Beyond.

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