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NASA NTRS1984

Improvements to the Photometric response and positional accuracy of the Yale PDS 2020G microdensitometer

The necessity to incorporate several hardware changes to optimize the Yale PDS 2020G microdensitometer for photometric and astrometric research are discussed. The properties of a new high speed photometer and a positional calibration system are described. The new photometer incorporates a high speed logarithmic analog to digital converter with more than 10 times the resolution of the former system and a cycle time of approximately 50 usec. The positional calibration system monitors the drunkenness of the stages with respect to fixed index lines and enables the correction of the +/- 5 micro stage errors to an accuracy of better than 1 micro.

Lee, J. F.↗

NASA NTRS1982

New two-dimensional photon camera

A photon-sensitive camera, applicable to speckle imaging of astronomical sources, high-resolution spectroscopy of faint galaxies in a crossed-dispersion spectrograph, or narrow-band direct imaging of galaxies, is presented. The camera is shown to supply 8-bit by 8-bit photon positions (256 x 256 pixels) for as many as 10 to the 6th photons/sec with a maximum linear resolution of approximately 10 microns. The sequence of photon positions is recorded digitally with a VHS-format video tape recorder or formed into an immediate image via a microcomputer. The four basic elements of the camera are described in detail: a high-gain image intensifier with fast-decay output phosphor, a glass-prism optical-beam splitter, a set of Gray-coded masks, and a photomultiplier tube for each mask. The characteristics of the camera are compared to those of other photon cameras.

Papaliolios, C.↗

NASA NTRS1991

Five degree-of-freedom control of an ultra-precision magnetically-suspended linear bearing

The authors constructed a high precision linear bearing. A 10.7 kg platen measuring 125 mm by 125 mm by 350 mm is suspended and controlled in five degrees of freedom by seven electromagnets. The position of the platen is measured by five capacitive probes which have nanometer resolution. The suspension acts as a linear bearing, allowing linear travel of 50 mm in the sixth degree of freedom. In the laboratory, this bearing system has demonstrated position stability of 5 nm peak-to-peak. This is believed to be the highest position stability yet demonstrated in a magnetic suspension system. Performance at this level confirms that magnetic suspensions can address motion control requirements at the nanometer level. The experimental effort associated with this linear bearing system is described. Major topics are the development of models for the suspension, implementation of control algorithms, and measurement of the actual bearing performance. Suggestions for the future improvement of the bearing system are given.

Trumper, David L.↗

NASA NTRS1986

Obtaining One-Degree Accuracy With Shaft Encoders

Circuit converts output of 1-pulse-per-revolution shaft encoder to precise 360-pulses-per-revolution output. Circuit allows shaft angular position to be measured with 1-degree accuracy. With simple modifications, circuit provides higher or lower resolution from single- or multiple-pulse-perrevolution sources. Circuit used to synchronize aircraft beacon transponder-based plan-position indicator (PPI) display to remote host interrogator search antenna. Constructed using standard, commercially available components.

Franke, J. M.↗

NASA NTRS1993

Subpixel Resolution In Depth Perceived Via 3-D Television

Report describes experiment in which two black vertical bars on featureless white background placed near intersection of optical axes of two charge-coupled-device video cameras positioned to give stereoscopic views. Trained human observers found to perceive depths at subpixel resolutions in stereoscopic television images. This finding significant for remote stereoscopic monitoring, expecially during precise maneuvers of remotely controlled manipulators. Also significant for research in processing of visual information by human brain.

Diner, Daniel B.↗

NASA NTRS2018

Quantitative validation of Ames IR intensity and new line lists for (32/33/34)S(16)O2, (32)S(18)O2 and (16)O(32)S(18)O

The quality of Ames-296K SO2 Infrared (IR) line list intensities is first validated by quantitative exploration of several dipole moment surfaces (DMSs) and partition sum convergence. The DMSs are computed with several of Dunning’s correlation-consistent basis sets and their vibrational dependence are compared to the empirical model derived from Stark effect experiments reported by D. Patel, D. Margolese, and T.R. Dykea [J.Chem.Phys. 70, 2740 (1979)]. The effective dipole deviations from the DMS adopted in the Ames IR lists is 0.2-0.4% for vibrational states up to 3v3. The vibrational dependence of the dipole moment is also in good agreement, except for nv1. Partition sum convergence at 296K is confirmed by new calculations with rotational quantum number J up to 150 and upper state E’ up to 8000 cm-1. The isotopologue consistency of the Ames IR line lists is superior relative to the regular Effective Hamiltonian (EH) models and Effective Dipole Moment (EDM) models. The v1+v2 and v2+v3 intensity consistency check reveals the recently reported experimental intensities need significant improvement or re-analysis. After the accuracy, convergence, and isotopologue consistency have been confirmed, the theoretical Ames-296K intensities are combined with the experimental line positions or EH models that experimental spectroscopists published after 2009. Three high-resolution IR line sets are reported for the (32/33/34)S(16)O2, (32)S(18)O2 and (16)O(32)S(18)O isotopologues: (1) the “New Lines Sets” include experimentally measured line positions; (2) the “Expanded Line Sets” include possible transitions among new rovibrational levels assigned in experiments and ground state (GS) levels predicted by reliable EH models; (3) the “Ames + MARVEL Sets” include possible transitions among all those levels reported in a recent MARVEL analysis. [Tóbiás et al, JQSRT 208, 152 (2018)]. Compared to the limited data in High-resolution TRANsmission molecular absorption database (HITRAN), these line sets have significantly improved the data coverage up to 4000 cm-1. Some missing bands can be traced to the unpublished experimental data. The isotopologue consistency of these line sets will help identify the uncertainties and defects in the experimental EH and EDM models. These line sets are good candidates for the next HITRAN update, if line shape parameters are available. The line sets can be downloaded from supplementary files or from the Ames Molecular Spectroscopic Database at http://huang.seti.org.

Xinchuan Huang↗

NASA NTRS1973

Anisotropic detector system for the measurement of gamma-ray source position

Detection efficiencies of cylindrical detectors for various gamma ray photon angular distributions in the energy range from .10 MeV to 15 MeV are studied. It was found that a properly chosen cylindrical crystal can produce a significantly modulated count rate as a function of angle when rotated in the anisotropic flux, The studies further indicate that simple detector systems can be used on small satellites for the determination of a gamma ray source position. Results are outlined and extended to examine source resolution angles for a practical size detector.

Trombka, J. I.↗

NASA NTRS1975

Sonic spark chambers for cosmic-ray experiments

The sonic spark chamber provides an attractive high resolution hodoscope for low flux cosmic ray experiments. Spark position is determined by measurement of the time of flight of the sonic shock front from the spark position to a number of piezoelectric transducers placed at the periphery of the chamber. For each spark, four quantities must be determined: the spark coordinates, the sound velocity, and the spark 'size'. By over-determining the four parameters, high accuracy is possible. With eight sonic transducers, air-gap spark positions were measured with an error of less than 100 microns everywhere over a 1 sq m region.

Ahlen, S. P.↗

NASA NTRS1978

Trajectories of high energy electrons in a plasma focus

Measurements are made of high-energy electron trajectories in a plasma focus as functions of position, time, energy, and angle of emission. The spatial resolution of the X-ray emission shows that low-energy X-rays are emitted from the anode surface. It is also suggested that the highest energy X-rays originate from a small region on the axis. The so-called shadow technique shows that the electron beam is perpendicular to the anode surface. Polar diagrams of medium and high-energy X-rays agree with the bremsstrahlung emission from a relativistic electron beam, the current of which is several 100 A.

Harries, W. L.↗

NASA NTRS1981

Development of a Shuttle Infrared Telescope Facility /SIRTF/ fine guidance sensor

Fine guidance technology development for the Shuttle Infrared Telescope Facility (SIRTF) centers upon the use of a single multiple-star-tracking sensor to provide the position information necessary to produce three-axis attitude control signals for precision payload pointing. The effort described in this paper is concerned with the development of a fine guidance sensor that employs a high-density charge-coupled imaging device for producing position information signals by using star fields. Multiple star position information produces three-axis position error signals that are used to update inertial reference gyros. The sensor employs advanced position interpolation algorithms to enhance field-of-view resolution and to correct for optical aberrations inherent in spatially chopped star images resulting from the telescope's movable secondary mirror. Operation of the sensor is under the control of a high-performance microcomputer that provides both autonomy and flexibility in a guidance application.

Salomon, P. M.↗

NASA NTRS1985

Constraints on cosmic-ray observation of Cygnus X-3

Two experimental groups working at different minimum energies have reported underground muons coming from the direction of Cygnus X-3 with rates that vary in synchrony with its binary period. At the Mont Blanc detector the events are, within statistics, uniformly spread over a 5 degree circle around the position of Cygnus X-3, even though the angular resolution is significantly better than this. The ratio of events in the phase peak to total muons observed rises as a function of minimum muon energy. An experiment also sees an excess in the number of pairs of codirectional multiple muon events arriving within about 5000 seconds of each other, the excess events coming from a direction about 20 degrees away from Cygnus X-3.

Barnhill, M. V., III↗

NASA NTRS1985

Comparison of the frequencies of NH3, CO2, H2O, N2O, CO, and CH4 as infrared calibration standards

The absolute accuracies of infrared calibration standards for the line positions have been investigated using a 0.0056-kayser-resolution (unapodized) Fourier-transform spectrum recorded from 550 to 5000 kayser. The spectrum has been obtained using a multicell arrangement containing the various molecular species. Detailed comoparisons reveal that standards for CO2, CH4, and N2O obtained from laser research and NH3 from Fourier-transform spectrometer research are consistent within the accuracies of the present data (+ or 0.0001 kayser). However, certain N2O, H2O, and CO values in the 1100-to 2300 kayser region are systematically high by 0.0001 to 0.0004 kayser. Correction factors for the H2O and CO standards are obtained to bring these into agreement with the laser values. In addition, corrected values for the 2nu-2 and nu-1 bands of N2O at 9 microns are reported.

Brown, L. R.↗

NASA NTRS1989

High-resolution observations of the multicomponent nucleus of NGC 5929

The central region of the type 2 Seyfert galaxy NGC 5929 is known to contain double radio-continuum and optical emission-line clouds separated by about 1 arcsec. High-resolution VLA mapping at 2 cm shows these two steep-spectrum radio clouds to be compact (about 13 pc FWHM) and well collimated on either side of a central source having a flatter spectrum. When the radio continuum and forbidden O III 5007-A image of Whittle et al. (1986) are compared at the same spatial resolution, there is no evidence that the separations or position angles of the radio and emission-line clouds differ. The double H-alpha clouds appear to differ in position angle by about 20 deg from the radio lobes. Large variations in excitation of the gas occur on the scale of the seeing. If the line-emitting clouds are confined in or near the radio lobes and the gas is ionized by a compact nuclear source, this source is likely to be beamed along the radio axis.

Wilson, Andrew S.↗

NASA NTRS1991

Arcsecond grating drive mechanism for operation at 4 K

A grating drive mechanism that achieves arcsecond positional control at both room temperature and 4 K is described. The mechanism accommodates eight equally spaced facets on a 360-deg drum, with each facet having arcsecond control over an angular range of +/-3 deg. The cryogenic portion consists of dry lubricated angular contact bearings, a dc brushless torque motor, and a compact magnetic position sensor capable of less than 1 arcsec rms resolution. Test results demonstrate angular repeatability of less than 2 arcsec rms at 4 K and static power dissipation to the helium bath of less than 100 microW.

Downey, C. H.↗

NASA NTRS1994

Convective flow effects on protein crystal growth

The long-term stability of the interferometric setup for the monitoring of protein morphologies has been improved. Growth or dissolution of a crystal on a 100 A scale can now be clearly distinguished from dimensional changes occurring within the optical path of the interferometer. This capability of simultaneously monitoring the local interfacial displacement at several widely-spaced positions on the crystal surface with high local depth resolution, has already yielded novel results. We found with lysozyme that (1) the normal growth rate is oscillatory, and (2) the mean growth step density is greater at the periphery of a facet than in its center. The repartitioning of Na(+) and Cl(-) ions between lysozyme solutions and crystals was studied for a wide range of crystallization conditions. A nucleation-growth-repartitioning model was developed to interpret the large body of data in a unified way. The results strongly suggests that (1) the ion to lysozyme ratio in the crystal depends mostly on kinetic rather than crystallographic parameters, and (2) lysozyme crystals possess a salt-rich core with a diameter on the order of 10 microns. The computational model for diffusive-convective transport in protein crystallization (see the First Report) has been applied to a realistic growth cell geometry, taking into account the findings of the above repartitioning studies. These results show that some elements of a moving boundary problem must be incorporated into the model in order to obtain a more realistic description. Our experimental setup for light scattering investigations of aggregation and nucleation in protein solutions has been extensively tested. Scattering intensity measurements with a true Rayleigh scatterer produced systematically increased forward scattering, indicating problems with glare. These have been resolved. Preliminary measurements with supersaturated lysozyme solutions revealed that the scatterers grow with time. Work has begun on a computer program for the unified evaluation of simultaneously obtained, multi-angle static and dynamic light scattering data.

Rosenberger, Franz↗

NASA NTRS1995

Unification of some advection schemes in two dimensions

The relationship between two approaches towards construction of genuinely two-dimensional upwind advection schemes is established. One of these approaches is of the control volume type applicable on structured cartesian meshes. It resulted in the compact high resolution schemes capable of maintaining second order accuracy in both homogeneous and inhomogeneous cases. Another one is the fluctuation splitting approach, which is well suited for triangular (and possibly) unstructured meshes. Understanding the relationship between these two approaches allows us to formulate here a new fluctuation splitting high resolution (i.e. possible use of artificial compression, while maintaining positivity property) scheme. This scheme is shown to be linearity preserving in inhomogeneous as well as homogeneous cases.

Sidilkover, D.↗

NASA NTRS1995

Ionized gas in the halos of edge-on, starburst galaxies: Data and results

We present narrowband H-alpha and broadband R images, as well as long-slit spectra oriented along the minor and major axes of a sample of about 50 edge-on (a/b greater than or equal to 2), infrared-warm (S(sub 60 microns)/S(sub 100 microns) greater than 0.04), infrared-bright S(sub 60 microns) greater than or equal to 5.4 Jy galaxies. The infrared luminosity of the sample ranges over 10(exp 10) - 10(exp 12) solar luminosity. The spatially resolved spectroscopy includes the measurement of velocity relative to the nuclear velocity, full width at half-maximum, total integrated flux in the profile (for those spectra taken under photometric conditions) for the lines (N II) lambda lambda 6548, 6583, (O I) lambda 6300, H-alpha, and (S II) lambda lambda 6716, 6713 and line ratios as a function of slit position along both the major and minor axes. The resolution of the spectra are between about 3 and 5 A. The spectroscopic data are presented for 5 bins along each axis -- a nuclear bin that is a sum of the CCD rows that cover the half-light diameter centered on the nucleus of the galaxy, two near-nuclear bins which are sums of the CCD rows that cover from one to two half-light radii on each side of the nucleus, and two off-nuclear bins which are sums of the rows at nuclear distances greater than two half-light radii on each side of the nucleus. Additionally, we present recession velocities, nuclear line asymmetries, rotation speeds, minor axis velocity shears, H-alpha luminosities, R-band absolute magnitudes, minor axis H-alpha `excess' and effective radii of the galaxies in h-alpha and the R continuum. We defer discussion of the properties of the emission-line gas and their correlation with the infrared properties of this sample of galaxies to a later paper and limit ourselves to a presentation of the data and analysis.

Lehnert, Matthew D.↗

NASA NTRS1995

X-ray emission from giant H II regions in M101

We have examined the archival ROSAT Position Sensitive Proportional Counter (PSPC) and the High-Resolution Imager (HRI) images of the galaxy M101 to study the X-ray properties of its giant H II regions. All five giant H II regions, NGC 5447, NGC 5445, NGC 5461, NGC 5462, and NGC 5471, show X-ray emission. By observing their basic properties, such as size, hardness ratio, and estimated luminosity, and by comparisons with better known regions in the Large Magellanic Cloud (LMC), we are able to suggest some possible mechanisms for the sources of the X-ray emission.

Williams, Rosa Murphy↗