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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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Investigations of the central 10 pc of the Galaxy, and conclusions on energetics, dynamics, and mass distribution derived from X and gamma ray measurements and from infrared and microwave studies, especially from spectroscopy, high resolution imaging, and interferometry are reviewed. Evidence for and against a massive black hole is analyzed.
The objective is the continuation of a long-term research program designed to study the composition, structure and processes operating on the surfaces of solar system objects using the Mauna Kea Observatory with techniques and modern instrumentation. Reflectance spectroscopy and multispectral imaging in the spectral region, 0.3 to 5.0 micrometer are the major techniques used, although thermal (10 micrometer and 20 micrometer) radiometry are used in some aspects of the research. Some specific projects include: (1) systematic spectral imaging observations of the Moon; (2) systematic spectral imaging and spectral monitoring of the Martian surface; (3) thermal radiometry of asteroids as part of the IRAS follow-up and other target specific programs; (4) searches for asteroid satellites and dust belts using a stellar coronagraph; and (5) studies of circumstellar disks using a stellar coronagraph. Progress for each of the programs included is discussed. minerals; (2) completed observations of lunar multi-ringed basins and crater deposits in search of high-Ca spectral anomalies; (3) completed data reduction of an additional 5 asteroids observed by the coronagraphic technique in the search for asteroids satellites and debris clouds; and (4) completed the reduction and calibration of 350 asteroids observed at 10 micron and 20 micron using the NASA IRTF.
The capabilities of the Astro observatory and the Hubble Space Telescope (HST) for UV astronomical observations are discussed. The advantages of using UV for studying extragalactic problems are reviewed, including sensitivity to hot sources, the rich UV line spectra, sensitivity to interstellar dust, and dark UV sky background. The HST and Astro instrumentation and plans for launching the systems are described. Possibile uses of HST and Astro include the study of massive stars in the Galaxy and nearby galaxies, interstellar medium, the UV excess component in old stellar populations, deep UV surveys (filter imaging and slitless spectroscopy), active galactic nuclei, quasars, and starburst systems.
The application of ballistic-electron-emission microscopy (BEEM) to a study of the influence of GaAs(100) substrate conditions on the formation of a multidefect structure at the Au-GaAs(100) Schottky barrier interface is described. Interfaces prepared on both melt-grown GaAs(100) wafer substrates and MBF-deposited GaAs(100) buffer layers are considered. As a comparison to the study of Au-GaAs(100) interfaces, BEEM imaging is performed on Au-Si(100) interfaces. It is noted that Au-GaAs(100) interface formation is relatively insensitive to the effects of substrate surface condition and substrate bulk defect density, and that the combination of BEEM imaging and BEEM spectroscopy indicates that the heterogeneous interface defects are the result of diffusion between the Schottky barrier electrodes.
Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied field magnetohydrodynamic thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 times 10 (exp 18) to 8 times 10 (exp 18) m(exp -3) and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.
Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied-field MPD thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 x 10 to the 18th to 8 x 10 to the 18th cu m and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.
The 1000-R(sub J)-wide neutral sodium nebula of Jupiter has now been observed on four separate occasions from late 1989 to early 1992. The observations have consisted of both low-dispersion spectroscopy and direct imaging. These observations have allowed us to establish some of the general features of the nebula, such as the largely equatorial confinement of emission, the r(exp -1) intensity behavior in the equatorial plane, and flaring of the emission with respect to the equator. Some additional evidence exists for more subtle morphology, such as a possible variable east-west intensity asymmetry. In this paper, we present a summary of observational evidence of variability in overall intensity, as well as in some of the morphological features of the nebula, over timescales of days, months, and years.
We report the discovery of neutral hydrogen in a second elliptical galaxy with shells, NGC 2865. Very Large Array (VLA) images reveal an association between the neutral hydrogen (H I) and the fine structure (shells, tails, and loops) in the galaxy. Similar to what we previously observed in NGC 5128 (Centaurus A), most of the 6 x 10(exp 8)/h(exp 2) solar mass of cold gas is found in a broken ring in the outer regions of NGC 2865 (beyond 0.5D(sub 25)) and is displaced to the outside of the shells and loops. The measured velocities cover a range of 500 km/s around the systematic velocity. The velocity field of the outer H I has the same sense and magnitude (and line of nodes) as that of the stars in the elliptical body. Although NGC 2865 appears to be a relaxed elliptical galaxy, deep images, photometry, and spectroscopy suggest that the galaxy might be the recent (less than 7 Gyr) product of a major disk-disk merger -- a 'dynamically young elliptical.' Our H I data support this hypothesis. Nevertheless, the association between gas and stellar fine structure, with gas displaced outward from the stars in projected position, implies gas motions not predicted by any of the current merger scenarios. Using the H I ring and assuming nearly circular motion, we measure M/L(sub B) at large radii (4 x 0.5D(sub 25)). We find M/L(sub B) = 33 +/- 4 h, a factor of 5 greater than the value of M/L(sub B) found for the central regions, indicating the presence of a dark halo.
The Large Area Modular Array of Reflectors (LAMAR) was selected as an attached payload for the Space Station Freedom in June 1989. It is a high throughput multiple X-ray telescope system that was capable of performing both imaging and dispersive spectroscopy measurements simultaneously. The LAMAR program was halted in 1990 when attached payloads were removed from the Space Station. A technical description of LAMAR is the main body of this report.
Computational models for the July, 1994 collision of comet Shoemaker Levy 9 with Jupiter have provided a framework for interpreting the observational data. Imaging, photometry, and spectroscopy data from ground-based, Hubble Space Telescope, and Galileo spacecraft instruments are consistent with phenomena that were dominated by the generation of incandescent fireballs that were ballistically ejected to high altitudes, where they formed plumes that subsequently collapsed over large areas of Jupiter's atmosphere. Applications of similar computational models to collisions into Earth's atmosphere show that a very similar sequence of events should take place for NEO impacts with energies as low as 3 megatons, recurring on 100 year timescales or less. This result suggests that the 1908 Tunguska event was a plume-forming atmospheric explosion, and that some of the phenomena associated with it might be related to the ejection and collapse of a high plume. Hazards associated with plume growth and collapse should be included in the evaluation of the impact threat to Earth, and opportunities should be sought for observational validation of atmospheric impact models by exploiting data already being collected from the natural flux of multikiloton to megaton sized objects that constantly enter Earth's atmosphere on annual to decadal timescales.
Micromachined Fabry-Perot tunable filters with a large clear aperture (12.5 to 40 mm) are being developed as an optical component for wide-field imaging 1:1 spectroscopy. This program applies silicon micromachining fabrication techniques to miniaturize Fabry-Perot filters for astronomical science instruments. The filter assembly consists of a stationary etalon plate mated to a plate in which the etalon is free to move along the optical axis on silicon springs attached to a stiff silicon support ring. The moving etalon is actuated electrostatically by electrode pairs on the fixed and moving etalons. To reduce mass, both etalons are fabricated by applying optical coatings to a thin freestanding silicon nitride film held flat in drumhead tension rather than to a thick optical substrate. The design, electro-mechanical modeling, fabrication, and initial results will be discussed. The potential application of the miniature Fabry-Perot filters will be briefly discussed with emphasis on the detection of extra-solar planets.
Individual, free-standing, vertically aligned multiwall carbon nanotubes or nanofibers are ideal for sensor and electrode applications. Our plasma-enhanced chemical vapor deposition techniques for producing free-standing and vertically aligned carbon nanofibers use catalyst particles at the tip of the fiber. Here we present a simple purification process for the removal of iron catalyst particles at the tip of vertically aligned carbon nanofibers derived by plasma-enhanced chemical vapor deposition. The first step involves thermal oxidation in air, at temperatures of 200-400 degrees C, resulting in the physical swelling of the iron particles from the formation of iron oxide. Subsequently, the complete removal of the iron oxide particles is achieved with diluted acid (12% HCl). The purification process appears to be very efficient at removing all of the iron catalyst particles. Electron microscopy images and Raman spectroscopy data indicate that the purification process does not damage the graphitic structure of the nanotubes.
We have developed techniques to measure branching fractions in the vacuum ultraviolet using diffraction grating spectroscopy and phosphor image plates as detectors. These techniques have been used to measure branching fractions in Fe II that give prominent emission lines in astrophysical objects.
Spitzer Space Telescope, the fourth and final of NASA's Great Observatories, and the cornerstone to NASA's Origins Program, launched on 25 August 2003 into an Earth-trailing solar orbit to acquire infrared observations from space. Spitzer has an 85cm diameter beryllium telescope, which operates near absolute zero utilizing a liquid helium cryostat for cooling the telescope. The helium cryostat, though designed for a 2.5 year lifetime, through creative planning now has an expected lifetime of 5.5 years. Spitzer has completed its in-orbit checkout/science verification phases and the first two years of nominal operations, becoming the first mission to execute astronomical observations from a solar orbit. Spitzer was designed to probe and explore the universe in the infrared utilizing three state of the art detector arrays providing imaging, photometry, and spectroscopy over the 3-160 micron wavelength range...
The Wide Field Infrared Survey Telescope (WFIRST) mission concept was ranked first in new space astrophysics mission by the Astro2010 Decadal Survey incorporating the Joint Dark Energy Mission (JDEM)-Omega payload concept and multiple science white papers. This mission is based on a space telescope at L2 studying exoplanets [via gravitational microlensing], probing dark energy, and surveying the near infrared sky. Since the release of NWNH, the WFIRST project has been working with the WFIRST science definition team (SDT) to refine mission and payload concepts. We present the driving requirements. The current interim reference mission point design, based on the use of a 1.3m unobscured aperture three mirror anastigmat form, with focal imaging and slitless spectroscopy science channels, is consistent with the requirements, requires no technology development, and out performs the JDEM-Omega design.
The Herschel Space Observatory is providing unprecedented sensitivity and angular resolution in the far-infrared. The DUNES Key Project (DUst around NEarby Stars, PI Carlos Eiroa) has finished its survey of 133 FGK stars within 25 pc of the Sun using the PACS photometer at 100 and 160 microns. We report the detection of a resolved debris ring around HIP 32480, a G0 star 16.5 parsecs distant. The ring is almost 300 AU in diameter and inclined 30 degrees from edge-on. We present a thermal emission model for the system that fits the Spitzer spectroscopy and Herschel images of the system. We find a minimum grainsize of approximately 4 microns in the main ring and a distinct warm dust population interior to it. Faint detached emission features just outside the ring may trace a separate, more distant ring in the system. The non-detection of the ring in archival HST/ACS coronagraphic images limits the dust grain albedo in the ring to be no more than 10%.
The Herschel Space Observatory is providing unprecedented sensitivity and angular resolution in the far-infrared. The DUNES Key Project (DUst around NEarby Stars, PI Carlos Eiroa) has finished its survey of 133 FGK stars within 25 pc of the Sun using the PACS photometer at 100 and 160 microns. We report the detection of a resolved debris ring around HIP 32480, a GO star 16.5 parsecs distant. The ring is almost 300 AU in diameter and inclined 30 degrees from edge-on. We present a thermal emission model for the system that fits the Spitzer spectroscopy and Herschel images of the system. We find a minimum grain-size of 4 microns in the main ring and a distinct warm dust population interior to it. Faint detached emission features just outside the ring may trace a separate, more distant ring in the system. The non-detection of the ring in archival HST/ACS coronagraphic images limits the dust grain albedo in the ring to be no more than 10%.
The New Worlds, New Horizons report released by the Astronomy and Astrophysics Decadal Survey Board in 2010 listed the Wide Field Infrared Survey Telescope (WFIRST) as the highest-priority large space mission for the . coming decade. This observatory will provide wide-field imaging and slitless spectroscopy at near infrared wavelengths. The scientific goals are to obtain a statistical census of exoplanets using gravitational microlensing. measure the expansion history of and the growth of structure in the Universe by multiple methods, and perform other astronomical surveys to be selected through a guest observer program. A Science Definition Team has been established to assist NASA in the development of a Design Reference Mission that accomplishes this diverse array of science programs with a single observatory. In this paper we present the current WFIRST payload concept and the expected capabilities for planet detection. The observatory. with science goals that are complimentary to the Kepler exoplanet transit mission, is designed to complete the statistical census of planetary systems in the Galaxy, from habitable Earth-mass planets to free floating planets, including analogs to all of the planets in our Solar System except Mercury. The exoplanet microlensing survey will observe for 500 days spanning 5 years. This long temporal baseline will enable the determination of the masses for most detected exoplanets down to 0.1 Earth masses.