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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Hubble Space Telescope Images of Nearby Luminous Quasars: Results for Eight Quasars and Tests of the Detection Sensitivity - 2

Observations with the Wide-Field Camera of the Hubble Space Telescope (HST) are presented for eight intrinsically luminous quasars with redshifts between 0.16 and 0.29. These observations, when combined with a similar HST study of the quasar PKS 2349-014, show that luminous nearby quasars exist in a variety of environments. Seven companion galaxies brighter than M(V) = 16.5 (H(sub 0) = 100 km s(sup -1) Mpc(sup -1), Omega(sub 0) = 1.0) lie within a projected distance of 25 kpc of the quasars; three of the companions are located closer than 3'' (6 kpc projected distance) from the quasars, well within the volume that would be enclosed by a typical L* host galaxy. The observed association of quasars and companion galaxies is statistically significant and may he an important element in the luminous-quasar phenomenon. Apparent host galaxies are detected for three of the quasars: PG 1116+215, 3C 273, and PG 1444+407; the hosts have an average absolute magnitude of about 0.6 mag brighter than L*. The agreement between the previously published major-axis directions in ground-based images and in the present HST images of 3C 273 and PG 1444+407 constitutes important evidence supporting the reality of these candidate host galaxies. Upper limits are placed on the visual-band brightnesses of representative galactic hosts for all the quasars. These limits are established by placing galaxy images obtained with HST underneath the quasars and measuring at what faintness level the known galaxies are detected. On average, the HST spirals would have been detected if they were as faint as 1 mag below L*, and the early-type galaxies could have been detected down to a brightness level of about L*, where L* is the Schechter characteristic luminosity of field galaxies. Smooth, featureless galaxy models (exponential disks or de Vaucouleurs profiles) are fitted to the residual light after a best-fitting point source is subtracted from the quasar images. The results show that smooth spiral galaxies brighter than, on average, about L*, would have been detected. These upper limits, or possible detections, are consistent with, for example, the eight luminous quasars studied in this paper, occurring in host galaxies that have a Shechter luminosity function with a lower cutoff in the range 0.01-0.1 L*. Tests are performed to determine if our failure to detect, in some cases, luminous host galaxies could be an artifact caused by our analysis procedures. These tests include comparing the measured point-spread function (PSF) for our HST observations with the PSFs used in previous ground-based studies of host galaxies, measuring the fluctuations in the sky signals that were subtracted from the quasar images, evaluating empirically the effects of using different stellar PSFs in the analysis, carrying out the subtraction of the stellar (nuclear) source in different ways, creating and analyzing artificial active galactic nuclei (AGNs) with known surface brightnesses, and fitting the observed quasar light to an analytic model that includes a host galaxy.

Bahcall, John N.↗
NASA NTRS1998

WFPC2 Observations of Star Clusters in the Magellanic Clouds: The Oldest Star Clusters in the Small Magellanic Cloud - Report 2

We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F45OW ( approximately B) and F555W (approximately V) of the intermediate-age populous star clusters NGC 121, NGC 339, NGC 361, NGC 416, and Kron 3 in the Small Magellanic Cloud. We use published photometry of two other SMC populous star clusters, Lindsay 1 and Lindsay 113, to investigate the age sequence of these seven populous star clusters in order to improve our understanding of the formation chronology of the SMC. We analyzed the V vs B-V and M(sub V) vs (B-V)(sub 0) color-magnitude diagrams of these populous Small Magellanic Cloud star clusters using a variety of techniques and determined their ages, metallicities, and reddenings. These new data enable us to improve the age-metallicity relation of star clusters in the Small Magellanic Cloud. In particular, we find that a closed-box continuous star-formation model does not reproduce the age-metallicity relation adequately. However, a theoretical model punctuated by bursts of star formation is in better agreement with the observational data presented herein.

Mighell, Kenneth J.↗
NASA NTRS2004

The Astro-E2 Mission

The Astro-E2 observatory is a rebuild of the original Astro-E observatory that was lost during launch in February 2000. It is scheduled for launch into low earth orbit on a Japanese M-V rocket in early 2005. The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, is developing the observatory with major contributions from the US. The three instruments on the observatory are the high-resolution x-ray spectrometer (the XRS) featuring a 30-pixel x-ray microcalorimeter array, a set of four CCD cameras (the XIS) and a combination photo-diode/scintillator detector system (the HXD) that will extend the band pass up to nearly 700 keV. A significant feature of Astro-E2 is that all of the instruments are coaligned and operated simultaneously. With its high spectral resolution and collecting area for spectroscopy above 1 keV, Astro-E2 should enable major discovery space and pioneer new technology for use in space. Prime areas for investigation are supernova remnants, active galaxies and the measurement of black hole properties via relativistically-broadened Fe-K emission galaxies. A number of enhancements have been made for the Astro-E2/XRS, including a higher resolution microcalorimeter array, ii mechanical cooler for longer cryogen life, and an improved in-flight calibration system. The Astro-E2/XIS has also been improved to include two back-side-illuminated CCDs to enhance the low energy response. Improvements have also been made to the x-ray mirrors used for both the XRS and XIS to sharpen the point spread function and reduce the effects of stray light. In this talk we will present the essential features of Astro-E2, paying particular attention to the enhancements, and describe the major scientific strengths of the observatory.

Kelley, Richard L.↗
NASA NTRS1997

Are the Leonid Meteor Storms Coming?

In February 1997, the Japanese Space Agency ISAS launched the first space VLBI Space Observatory Program Satellite (VSOP) using the newly developed M-V launch vehicle.

Leonid Meteor Storms↗
NASA NTRS2010

The Kepler Full Frame Images

NASA's exoplanet discovery mission Kepler provides uninterrupted 1-min and 30-min optical photometry of a 100 square degree field over a 3.5 yr nominal mission. Downlink bandwidth is filled at these short cadences by selecting only detector pixels specific to 105 preselected stellar targets. The majority of the Kepler field, comprising 4 x 10(exp 6) m_v < 20 sources, is sampled at much lower 1-month cadence in the form of a full-frame image. The Full Frame Images (FFIs) are calibrated by the Science Operations Center at NASA Ames Research Center. The Kepler Team employ these images for astrometric and photometric reference but make the images available to the astrophysics community through the Multimission Archive at STScI (MAST). The full-frame images provide a resource for potential Kepler Guest Observers to select targets and plan observing proposals, while also providing a freely-available long-cadence legacy of photometric variation across a swathe of the Galactic disk.

Dotson, Jessie L.↗
NASA NTRS2016

A Neural Network Approach for Identifying Particle Pitch Angle Distributions in Van Allen Probes Data

Analysis of particle pitch angle distributions (PADs) has been used as a means to comprehend a multitude of different physical mechanisms that lead to flux variations in the Van Allen belts and also to particle precipitation into the upper atmosphere. In this work we developed a neural network-based data clustering methodology that automatically identifies distinct PAD types in an unsupervised way using particle flux data. One can promptly identify and locate three well-known PAD types in both time and radial distance, namely, 90deg peaked, butterfly, and flattop distributions. In order to illustrate the applicability of our methodology, we used relativistic electron flux data from the whole month of November 2014, acquired from the Relativistic Electron-Proton Telescope instrument on board the Van Allen Probes, but it is emphasized that our approach can also be used with multiplatform spacecraft data. Our PAD classification results are in reasonably good agreement with those obtained by standard statistical fitting algorithms. The proposed methodology has a potential use for Van Allen belt's monitoring.

Souza, V. M.↗
NASA NTRS2018

The Possible Contribution of Dielectric Breakdown to Space Weathering on Phobos

The origins of Phobos and Deimos are uncertain; both are so space weathered that their surface compositions are difficult to determine using spectral reflectance measurements. We show how the winter temperatures and associated conditions in the polar regions of Phobos could make the regolith susceptible to space weathering from dielectric breakdown caused by solar energetic particles (SEPs). During SEP events, charged particles accumulate throughout the top ~ 1 mm of the regolith, which has low condukctivity, and create subsurface electric fields that act to dissipate any net buildup of charge. The faster the net charge accumulates, the larger the electric field needed to dissipate it. If the magnitude of the subsurface electric field exceeds ~10 6 V m -1, then dielectric breadkown is likely. This process rapidly dissipates the buildup of charge by vaporizing electrically conducting channels through the regolith. Dielectric breakdown

Space Weathering↗
NASA NTRS2022

Constraints on the Optical Depth to Reionization from Balloon-borne Cosmic Microwave Background Measurements

We assess the uncertainty with which a balloon-borne experiment, nominally called Tau Surveyor (τS), can measure the optical depth to reionization σ(τ) with given realistic constraints of instrument noise and foreground emissions. Using a τS fiducial design with six frequency bands between 150 and 380 GHz, with white and uniform map noise of 7 μK arcmin, achievable with a single midlatitude flight, and including Planck's 30 and 44 GHz data, we assess the error σ(τ) obtained with three foreground models and as a function of sky fraction f sky between 40% and 54%. We carry out the analysis using both parametric and blind foreground separation techniques. We compare the σ(τ) values to those obtained with low-frequency and high-frequency versions of the experiment called τS-lf and τS-hf, which have only four and up to eight frequency bands with narrower and wider frequency coverage, respectively. We find that with τS, the lowest constraint is σ(τ) = 0.0034, obtained for one of the foreground models with f sky = 54%. σ(τ) is larger, in some cases by more than a factor of 2, for smaller sky fractions, with τS-lf, or as a function of foreground model. The τS-hf configuration does not lead to significantly tighter constraints. The exclusion of the 30 and 44 GHz data, which give information about synchrotron emission, leads to significant τ misestimates. Decreasing noise by an ambitious factor of 10, while keeping f sky = 40%, gives σ(τ) = 0.0031. The combination of σ(τ) = 0.0034, baryon acoustic oscillation data from DESI, and future cosmic microwave background B-mode lensing data from the CMB-S3/CMB-S4 experiments could give σ(∑m v ) = 17 meV.

cosmic microwave background radiation↗
NASA NTRS1990

Observational effects of interaction in the Seyfert galaxy NGC 7469

Some pecularities of the circummucleus of the Seyfert galaxy NGC 7469 were revealed, plausibly caused by interaction with the satellite IC 5283 and a starlike detail, situated on the edge of the west spiral branch 14 seconds from the nucleus. Shock excited H II regions were noted in the part of NGC 7469 turned toward the satellite IC 5283. The galaxy's central radio structure (lambda approx. 6 cm) stretches in the direction toward the satellite IC 5283 and the starlike detail. The spectum and color index of the starlike detail suggest that it is a cluster of early type stars (M sub V = -19 sup m) and dust clouds (A sub V = 3 sup m), in NGC 7469.

Pronik, I. I.↗
NASA NTRS1995

Space photovoltaic modules based on reflective optics

The conceptual design and experimental results for two types of space application concentrator photovoltaic modules, employing reflective optical elements, are presented. The first type is based on the use of compound parabolic concentrators, the second type is based on the use of line-focus parabolic troughs. Lightweight concentrators are formed with nickel foil coated silver with a diamond-like carbon layer protection. Secondary optical elements, including lenses and cones, are introduced for a better matching of concentrators and solar cells. Both types of modules are characterized by concentration ratios in the range 20x to 30x, depending on the chosen range of misorientation angles. The estimated specific parameters of these modules operating with single junction AlGaAs/GaAs solar cells are 240 W/sq m and 3 kg/sq m.

Andreev, V. M.↗
NASA NTRS1931

Estimated Effect of Ring Cowl on the Climb and Ceiling of an Airplane, Special Report

Although the application of a ring cowl to an airplane with an air-cooled engine increases the maximum L/D and the high speed to an appreciable extent, the performance in climb and ceiling is not increased as much as one would expect without analyzing the conditions. When a ring cowl is installed on an airplane, the propeller is set at a higher pitch to allow the engine to turn its rated r.p.m. at the increased high speed. V/nD is increased and the propeller efficiency at high speed is increased slightly. The ratio of r.p.m. at climbing speed, V(sub c) , to the r.p.m. at maximum speed, V (sub m) is dependent upon the ratio of V(sub c) to V(sub m). The increase in V(sub c) for all airplane with ring cowl i s not as great as the increase in V(sub m), so that the ratio V(sub c)/V(sub m) is less than for the airplane without ring. Consequently the r.p.m. and full throttle thrust power available are less at V(sub c) for the airplane with ring cowl and in spite of the increase in L/D due to the installation of the ring, the excess thrust power available for climbing is not appreciably changed. The same method of reasoning accounts for the small increase in absolute ceiling in spite of a large increase in L/D maximum.

Louden, F. A.↗
NASA NTRS1980

Detection of a white dwarf in a visual binary system

The F6 giant HD 160365 was detected to have a white dwarf companion about 8 arcsec south of the star. The UV energy distribution observed with International Ultraviolet Explorer (IUE) shows that the white dwarf has an effective temperature of 23,000 +/- 2,000 K. If log g = 8 the Ly(alpha) profile indicates an effective temperature around 24,500 K. Using the theoretical models, one finds a visual magnitude of m(sub v) is approximately 16.5. For T(sub eff) = 24,500 K one expects for a white dwarf a luminosity of log L/solar luminosity is approximately -1.3 and M(sub V) is approximately 10.67. This gives a distance modulus for the system of m(sub v) - M(sub V) = 5.83 and an absolute magnitude M(sub v) = 0.3 for the giant.

Boehm-Vitense, Erika↗
NASA NTRS1985

Optical monitoring of gamma-ray source fields

The three gamma-ray burst source fields GBS1028+46, GBS1205+24, and GBS2252-03 have been monitored for transient optical emission for a combined total of 52 hours. No optical events were seen. The limiting magnitude for the search was M sub V = 15.8 longer and M sub V = 17.0 for 6.0 s or longer.

Gehrels, N.↗
NASA NTRS1995

High efficient radiation stable AlGaAs/GaAs solar cells with internal Bragg reflector

An investigation of solar cells based on AlGaAs/GaAs heterostructures with an internal Bragg reflector as the back-surface reflector is presented. The Bragg reflector is grown by low pressure metalorganic chemical vapor deposition on n-GaAs substrates in a horizontal resistively heated reactor. The Bragg reflector with its maximum reflectance centered at a wavelength of 860 nm consists of 12 pairs of AlAs/GaAs layers. The resulting Bragg reflector has a thickness of 0.072 micrometers for AlAs and 0.059 micrometers for GaAs. The multi-layered quasi-dielectric stack selectively reflects weakly absorbed photons with energies near to the GaAs band gap for a second pass through the photoactive region, thus increasing the photocurrent. The use of the Bragg reflector allows the external quantum efficiency to be increased in the long wavelength of the spectrum. The use of the Bragg reflector and an antireflective coating and prismatic cover allowed an efficiency of 23.4 percent to be obtained.

Andreev, V. M.↗
NASA NTRS1988

Images in the rocket ultraviolet - UV fluxes of M31 globular clusters

Images obtained by a rocket-borne UV imaging telescope are used here to determine near-UV fluxes for 17 sources in M31 that are optical globular-cluster candidates and for the bright open cluster vdB0 in M31. Far-UV fluxes or flux limits are determined for the same clusters. The m(NUV)-V colors for M31 clusters are similar to those of Galactic clusters, except for the high-metallicity M31 cluster Bo 171. Four of the detected clusters have optical, m(NUV) - V, and m(FUV) - V colors indicating ages of about 100 million years. These four clusters are probably similar to the so-called 'blue globular' clusters of the LMC. The existence of young LMC-type blue globulars and the possible existence of middle-aged metal-rich globulars may indicate that M31 has continued to form globular clusters throughout its life.

Bohlin, Ralph C.↗
NASA NTRS1982

Anti-misting additives for jet fuels

The ignition characteristics of sprays, created by wind shear action, of Jet-A fuel containing polyisobutylene additives wee examined over ranges of air velocities from 45 to 90 m/s and of fuel/air mass ratios of 0.20 to 8.0. Ignition was by calibrated sparks of energies up to about 0.5 J and by a butane/oxygen flame at 165 J/s. The polymeric additives studied included the grades L80, L160, and L200 from Exxon Chemical and B200 and B230 from BASF. The ignition suppression ability of the additives, as well as their observed anti-misting (AM) behavior, ranked exactly as their molecular weights (viscosity average, M sub v) with 400-500 ppm of L80 (M sub v = 0.68 x 1,000,000) being required to suppress ignition of a spray at 51 m/s, 1.8 fuel/air mass ratio, by a 0.55 J spark while only 10 ppm of B230 (M sub v = 7.37 x 1,000,000) was required for the same conditions. The additive concentrations (L160) required for ignition suppression increased with increasing air velocity and with increasing fuel/air ratio.

Grens, E. A., II↗
NASA NTRS1992

Observations of optical counterparts of Gamma-Ray bursts

This is a final report for a contract begun in Dec. 1987 and ended in Mar. 1989 to use the existing Lincoln Laboratory Experimental Test Site in Socorro, NM to search for optical counterparts to gamma-ray bursts. The objective was to develop an autonomous staring system to search for stationary, transient optical flashes. The search was to use an existing 31-inch telescope equipped with a sensitive video detector. The approach for the search was to develop real-time processing software to monitor the video signal from the detector and to record any transient, point-like flashes that occurred in the field of view. The system would have been able to detect fainter flashes (B is approximately 15(sup m) in 1/30 s, delta(m(sub v)) = 0.25(sup m)) than other systems but lacked a large field of view (only 1.2 deg diameter) necessary to give a high probability of detecting a random flash on the sky. As such, the plan was to monitor known gamma-ray burst error boxes and wait for a repetition of an earlier event. The high payoff of good sensitivity with high angular resolution (1 pixel = 10sec) and good time resolution (30 s) to allow post-burst searches warranted funding if the cost was not prohibitive. The contract began in the middle of the three-year cycle for High Energy Astrophysics Gamma-Ray Astronomy Research and Analysis Program. This final report briefly describes the portion of the plan completed under the original contract.

Knight, Frederick K.↗
NASA NTRS1998

Planetesimal Formation in the Protoplanetary Nebula

In this talk we will address two distinct phases of planetesimal formation, each of which is fundamentally dependent upon the coupled interactions of particles and turbulent nebula gas. It has been shown both numerically and experimentally that 3-D (three dimensional) turbulence concentrates aerodynamically size-selected particles by orders of magnitude. In a previous review chapter we illustrated the initial predictions of Turbulent Concentration (TC) as applied to the solar nebula. We predicted the particle size which will be most effectively concentrated by turbulence; it is the particle which has a gas drag stopping time equal to the overturn time of the smallest (Kolmogorov scale) eddy. The primary uncertainty is the level of nebula turbulence, or Reynolds number Re, which can be expressed in terms of the standard nebula eddy viscosity parameter alpha = Rev(sub m)/cH, where v(sub m) is molecular viscosity, c is sound speed, and H is vertical scale height. Several studies, and observed lifetimes of circumstellar disks, have suggested that the level of nebula turbulence can be described by alpha = 10(exp -2) - 10(exp -4). There is some recent concern about how energy is provided to maintain this turbulence, but the issue remains open. We adopt a canonical minimum mass nebula with a range of alpha is greater than 0. We originally showed that chondrule-sized particles are selected for concentration in the terrestrial planet region if alpha = 10(exp -3) - 10(exp -4). In addition, Paque and Cuzzi found that the size distribution of chondrules is an excellent match for theoretical predictions. One then asks by what concentration factor C these particles can be concentrated; our early numerical results indicated an increase of C with alpha, and were supported by simple scaling arguments, but the extrapolation range was quite large and the predictions (C is approximately equal to 10(exp 5) - 10(exp 6) not unlikely) uncertain. The work presented here, which makes use of our recent demonstration that the particle density field is a multifractal with flow-independent properties provides a far more secure ground for such predictions. We also indicate how fine-grained dust rims on chondrules might enter into constraining the situation. Once large particles (meter-size mass equivalent) reach the midplane, perhaps in the form of dense aggregates of the sort formed in 3D turbulence, they remain stable against gravitational instability but might grow rapidly by accretion of their drifting neighbors, depending on the level of global turbulence.

Cuzzi, Jeffrey N.↗