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NASA NTRS1979

Recent developments at JPL in the application of image processing to astronomy

Four applications of image processing to astronomy, automated location and analysis of star and galaxy images, geometric and radiometric decalibration of vidicon spectra, display of multiband radio images, and generation of high resolution polarization direction and magnitude maps from images are presented with illustrative examples. The technique by which a digital image can be analyzed automatically to locate and segregate between stars and galaxies and the steps performed by the classifier to determine the nature of each object are outlined. The classification program executed on a 48 inch Schmidt plate of the cluster of galaxies 655 is described. The calibration and decalibration steps to remove geometric and radiometric distortions from a silicon vidicon camera digital spectra are discussed. Three methods of displaying multispectral radio data, generating a mosaic of each image, producing a color coded image to depict radio velocity, and producing a stereo pair with radial velocity as depth are described. The generation of polarization information from images obtained through linear polarizing filters is illustrated, and it is concluded that in each case information was displayed using digital techniques which could not readily have been provided visually.

Lorre, J. J.↗

NASA NTRS1976

The nature of flow distortions caused by rotor blade wakes

The distortion caused by wakes of rotor blades is one of the least understood phenomena in turbomachinery. An attempt is made to predict the decay characteristics of the defect in axial and tangential velocity components, and the decay of the maximum radial velocity inside the rotor wake using the momentum integral analysis. The predictions agree well with the experimental data taken at the exit of an axial flow fan operating at zero incidence. The measurements are carried out with a three sensor hot wire probe. The wake width is found to grow linearly with distance downstream and the defect in tangential velocity inside the rotor wake decays fastest of the three components. An empirical expression is also provided for the axial velocity profile of a rotor wake.

Lakshminarayana, B.↗

NASA NTRS1988

Effective radii of annuli in surface photometry

When surface photometry is done in concentric annuli, there is a tendency toward distortion of the true profile because of the finite widths of the annuli. This distortion can be avoided by choosing an effective radius for the annulus such that the actual surface brightness at that radius is equal to the average surface brightness over the annulus. This effective radius depends on the shape of the radial profile, but its calculation can be performed in an iterative way. Formulas for the effective radius are given for some typical profile shapes.

King, Ivan R.↗

NASA NTRS1957

Experimental Investigation of Vibratory Stresses in a Concentric-Ring Direct-Air-Cycle Nuclear Fuel Element

Preliminary tests made by the General Electric Company indicated that aerodynamic loads might cause large enough distortions in the thin sheet-metal rings of a nuclear fuel element to result in structural failure. The magnitude of the distortions in a test fuel element was determined from strains measured with airflow conditions simulating those expected during engine operation. The measured vibratory strains were low enough to indicate the improbability of failure by fatigue. A conservative estimate of the radial deflection that accompanied peak strains in the outer ring was +0.0006 inch.

Chiarito, Patrick T.↗

NASA NTRS2016

The Atacama Cosmology Telescope: Dynamical Masses for 44 SZ-Selected Galaxy Clusters over 755 Square Degrees

We present galaxy velocity dispersions and dynamical mass estimates for 44 galaxy clusters selected via the Sunyaev-Zeldovich (SZ) effect by the Atacama Cosmology Telescope. Dynamical masses for 18 clusters are reported here for the first time. Using N-body simulations, we model the different observing strategies used to measure the velocity dispersions and account for systematic effects resulting from these strategies. We find that the galaxy velocity distributions may be treated as isotropic, and that an aperture correction of up to 7 per cent in the velocity dispersion is required if the spectroscopic galaxy sample is sufficiently concentrated towards the cluster centre. Accounting for the radial profile of the velocity dispersion in simulations enables consistent dynamical mass estimates regardless of the observing strategy. Cluster masses M200 are in the range (1 - 15) times 10 (sup 14) Solar Masses. Comparing with masses estimated from the SZ distortion assuming a gas pressure profile derived from X-ray observations gives a mean SZ-to-dynamical mass ratio of 1:10 plus or minus 0:13, but there is an additional 0.14 systematic uncertainty due to the unknown velocity bias; the statistical uncertainty is dominated by the scatter in the mass-velocity dispersion scaling relation. This ratio is consistent with previous determinations at these mass scales.

Sunyaev-Zeldovich (SZ)↗

NASA NTRS1980

Spatial evolution of magnetic fields as seen in coronal streamers to 12 R sub o during the solar cycle

Outer coronal photographs made from high altitude aircraft at the solar eclipses of 1966, '70, '72, '73, and '79 which sample various times in the solar cycle are presented. Coronal streamers extending from the solar limb to 12 R sub o are displayed. The evolution of the streamers as they distort magnetic field lines to large distances from the Sun is examined. Results show that the distortion is varied, that the polar plumes can be traced beyond 8 R sub o, diverging apparently along dipole field lines, and that the divergence varies along the solar cycle. Various changes in nonpolar streamers are discussed including the tendency to become radial beyond 3 to 5 R sub o as if controlled by the solar wind.

Keller, C. F.↗

NASA NTRS1983

Rapid distortion of small-scale turbulence by an axisymmetric contraction

The rapid distortion of small-scale turbulence by an axisymmetric internal contracting flow has been investigated. The analysis is an example of the modern version of rapid distortion theory in that the effects of vortex bending and tilting are included. On the axis of symmetry, the classical results are recovered. The longitudinal and lateral velocity components are suppressed and amplified, respectively, with increasing contraction ratio. These effects are enhanced with increasing radial position. The numerical calculations also show that the correlation between the streamwise and radial velocity components increases monotonically with respect to both the radial location and the contraction ratio. The longitudinal and lateral one-dimensional spectra show a shift towards higher and lower wavenumbers, respectively, as the contraction ratio increases. Here, these effects become less pronounced for larger radii. These results also show that the downstream longitudinal integral length scale based on the streamwise velocity as well as the one based on the transverse velocity increase with the radial coordinate.

Hultgren, L. S.↗

NASA NTRS2002

Manufacturing Distortions of Curved Composite Panels

This papa briefly discusses the influences of through-thickness thermal expansion, a misaligned ply, and a resin-rich slightly thicker ply on the deformations of a curved composite laminate during cool down from tbc cure temperature. Both two-dimensional and three-dimensional level finite-element analyses are used. The deformations are categorized as to radial and tangential deformations and twist, and for each of the three influences, these deformations are quantified. An additional outcome of the study is an indication of the level of analysis needed to study each of these three influences.

Starnes, James H., Jr.↗

NASA NTRS1983

Inlet-fan flow field computation

The flow field of a tilt-nacelle inlet-fan combination used for V/STOL aircraft is studied. Under certain flight conditions the inlet is subjected to high angles of attack and/or yaw. This produces a non-uniform or distorted flow field at the fan-face that can lead to large blade stresses. This paper presents an analytical approach to the coupled inlet-fan problem. The nacelle is modelled by a distribution of source panels and the fan by a distribution of radial vortices. A modified actuator disc with losses and a quasi-steady rotor response is used to derive the boundary condition at the fan-face. An example of the calculation is shown.

Matwey, M. D.↗

NASA NTRS2013

Irradiation of an Accretion Disc by a Jet: General Properties and Implications for Spin Measurements of Black Holes

X-ray irradiation of the accretion disc leads to strong reflection features, which are then broadened and distorted by relativistic effects. We present a detailed, general relativistic approach to model this irradiation for different geometries of the primary X-ray source. These geometries include the standard point source on the rotational axis as well as more jet-like sources, which are radially elongated and accelerating. Incorporating this code in the RELLINE model for relativistic line emission, the line shape for any configuration can be predicted. We study how different irradiation geometries affect the determination of the spin of the black hole. Broad emission lines are produced only for compact irradiating sources situated close to the black hole. This is the only case where the black hole spin can be unambiguously determined. In all other cases the line shape is narrower, which could either be explained by a low spin or an elongated source. We conclude that for those cases and independent of the quality of the data, no unique solution for the spin exists and therefore only a lower limit of the spin value can be given

Accretion Disc↗

NASA NTRS1989

Distortion effects in spacecraft observations of MHD toroidal standing waves - Theory and observations

This paper considers the distortion effect of the simultaneous occurrence of locally resonant toroidal pulsations over a range of L shells on the interpretation of spacecraft observations of these waves. A theoretical model is developed which yields quantitative predictions of the phase shear effect that causes a shift from the true pulsation frequency measured from a spacecraft moving radially across L shells. Calculations with this model indicate that, due to this effect, the AMPTE/CCE satellite should observe 8-30 percent lower frequencies on outbound passes than on inbound passes. A comparison of fundamental mode frequency measurements made on 10 inbound and 9 outbound passes of the AMPTE/CCE satellite in the morning sector confirms the predictions of the model.

Anderson, B. J.↗

NASA NTRS1989

Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images

Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry parallel to the illumination vector and will appear increasingly compressed toward higher latitudes.

Ford, J. P.↗

NASA NTRS1987

White light sunspot observations from the Solar Optical Universal Polarimeter on Spacelab-2

The flight of the Solar Optical Universal Polarimeter on Spacelab-2 provided the opportunity for the collection of time sequences of diffraction-limited (0.5 arcsec) solar images with excellent pointing stability (0.003 arcsec) and with freedom from the distortion that plagues ground-based images. A series of white-light images of active region 4682 were obtained on August 5, 1985, and the area containing the sunspot has been analyzed. These data have been digitally processed to remove noise and to separate waves from low-velocity material motions. The results include: (1) proper motion measurements of a radial outflow in the photospheric granulation pattern just outside the penumbra; (2) discovery of occasional bright structures ('streakers') that appear to be ejected outward from the penumbra; (3) broad dark 'clouds' moving outward in the penumbra, in addition to the well-known bright penumbral grains moving inward; (4) apparent extensions and contractions of penumbral filaments over the photosphere; and (5) observation of a faint bubble or looplike structure that seems to expand from two bright penumbral filaments into the photosphere.

Shine, R. A.↗

NASA NTRS1984

Convection-induced distortion of a solid-liquid interface

Measurements of convective flow fields and solid-liquid interface shapes during the solidification of a pure and a slightly alloyed transparent material reveal that the convective transport of solute can cause a macroscopic depression to develop in the solid-liquid interface. This effect occurs under conditions close to those which are predicted to produce morphological instability of a planar interface. A cellular or dendritic microstructure later develops within the interface depression. The convection is attributed to the effect of radial temperature gradients in the crystal growth apparatus.

Schaefer, R. J.↗

NASA NTRS1971

On propagation of long waves in curved ducts.

Propagation of waves in curved ducts and pipes belong to the class of motion which is characterized by wave patterns totally different from those known in straight ducts or in unlimited space. The curvilinear boundaries are responsible for the appearance of a continuous standing radial wave which in turn affects the transmitted tangential waves. The purpose of this paper is to solve the problem of propagation of long acoustic waves in slightly and sharply bent ducts. This problem has been only partially analyzed by various authors. In this study two acoustic systems are considered which allow determination of the basic modes of motion and describe the transition and distortion of plane waves as they propagate down the curved channel. A detailed study of the behavior of waves in junctions between straight and curved ducts is also given. Solutions and expressions for principal modes of the wave are obtained by using the linearized equation of motion solved for its characteristic values. This original approach required a novel use of Bessel functions to determine the characteristic values of the steady and the decaying fields of motion.

Rostafinski, W.↗

NASA NTRS1979

Structure and properties of Jupiter's magnetoplasmadisc

Voyager 1 plasma-wave observations have revealed the existence of an earthlike continuum radiation trapped in Jupiter's magnetospheric cavity at frequencies below the solar-wind plasma frequency. This radiation serves as an accurate diagnostic of the local electron number density throughout most of Jupiter's outer magnetosphere and yields information regarding the gross configuration of the magnetoplasmadisk as well as its kinematical properties. Magnetic-field observations are used to construct radial profiles of plasma pressure, density, and temperature from 20-80 Jupiter radii in the early-morning plasma sheet, along with plasma-sheet crossings and estimated thicknesses. The study suggests that hot protons (about 10 keV) are the dominant constituents of the plasma sheet (average thickness about 4.2 Jupiter radii) out to 80 Jupiter radii, beyond which centrifugal effects take over and distort the sheet toward the rotational equator.

Barbosa, D. D.↗

NASA NTRS1990

Analysis and design of helium-buffered face seals for the SSME high-pressure oxygen turbopump

One form of a gas-buffered seal consists of two opposed fluid-film face seals, each mating against a single collar. The buffer fluid is introduced at the OD and flows through the radial clearances of each seal to opposite and separate environments at the IDs. This arrangement was investigated for the helium buffer seals applied to the oxidizer pump of the Space Shuttle Main Engine (SSME). A variety of face configurations were considered, and the self-energized-hydrostatic and spiral-groove geometries were selected for detailed evaluation. Fluid-film performance, dynamic response, and thermoelastic distortions were determined. Because of very high temperature gradients, distortions of the turbine-side seal ring were excessive. Otherwise, performance was excellent in all respects.

Shapiro, Wilbur↗

NASA NTRS1997

An Experimental Investigation of Steady and Unsteady Flow Field in an Axial Flow Turbine

Measurements were made in a large scale single stage turbine facility. Within the nozzle passage measurements were made using a five hole probe, a two-component Laser Doppler Velocimeter (LDV), and a single sensor hot wire probe. These measurements showed weak secondary flows at midchord, and two secondary flow loss cores at the nozzle exit. The casing vortex loss core was the larger of the two. At the exit radial inward flow was found over the entire passage, and was more pronounced in the wake. Nozzle wake decay was found to be more rapid than for an isolated vane row due to the rotor's presence. The midspan rotor flow field was measured using a two-component LDV. Measurements were made from upstream of the rotor to a chord behind the rotor. The distortion of the nozzle wake as it passed through the rotor blade row was determined. The unsteadiness in the rotor flow field was determined. The decay of the rotor wake was also characterized.

Zaccaria, M.↗