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At least 127 records · Page 7

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NASA NTRS1972

Microcraters on lunar rocks.

Microcrater frequency distributions have been obtained for nine Apollo rocks and an exterior chip of an Apollo 12 rock. The frequency distributions indicate that five of the Apollo 14 rocks were tumbled more than once exposing different rock faces whereas four were not tumbled and represent a single exposure interval. The cumulative frequency of craters per square centimeter was extended below optical resolution limits using a SEM scan of an exterior chip of breccia 12073. No craters with central pit diameters less than 15 microns were seen in a total area of 0.44 sq cm. A detailed SEM scan of crystal faces and glassy crater liners revealed no microcraters equal to or larger than the resolution limit of 5 microns. An upper limit of 170 craters per sq cm with central pit diameters larger than 5 microns was set. The slope of the cumulative frequency curve for craters with central pit diameters less than about 75 microns is less than that obtained by other workers.

Morrison, D. A.↗

NASA NTRS1977

The vibrational energy levels and dissociation energy of O2/+/ /X 2 Pi g/

The absolute vibrational energy levels of the X 2 Pi g state of O2(+) have been determined by the method of photoelectron spectroscopy in the range nu = 0-25. The precision of the method is comparable to that of conventional high resolution optical spectroscopy. The dissociation energy obtained by a linear extrapolation of the vibrational separations is found to be 6.67 plus or minus 0.18 eV.

Samson, J. A. R.↗

NASA NTRS1980

On optical imaging through aircraft turbulent boundary layers

Optical resolution quality as affected by aircraft turbulent boundary layers is analyzed. Wind-tunnel data was analyzed to obtained the variation of boundary layer turbulence scale length and mass density rms fluctuations with Mach number. The data gave good agreement with a mass density fluctuation turbulence spectrum that is either isotropic of orthogonally anisotropic. The data did not match an isotropic turbulence velocity spectrum which causes an anisotropic non-orthogonal mass density fluctuation spectrum. The results indicate that the average mass density rms fluctuation is about 10% of the maximum mass density across the boundary layer and that the transverse turbulence scale size is about 10% of the boundary layer thickness. The results indicate that the effect of the turbulent boundary layer is large angle scattering which decreases contrast but not resolution. Using extinction as a criteria the range of acceptable aircraft operating conditions are given.

Sutton, G. W.↗

NASA NTRS1982

The interstellar spectrum of the supernova 1980k in NGC 6946

Bright supernovae in external galaxies offer a rare opportunity to probe the intervening interstellar media over very extended path-lengths, including the disk and halo of the Galaxy and the parent galaxy of the supernova. SN 1980k was discovered in NGC 6946 on 1980 October 29. In the first month after discovery, high resolution optical and ultraviolet observations were obtained to exploit the supernova as a probe of the intervening interstellar media. The obtained data are discussed. In the spectra, absorption lines were observed of Mg I, Mg II, Fe II, Mn II, Ca II and Na I. The absorption lines are attributed to the intervening interstellar media distributed over the very extended line of sight sampled, of order 7 Mpc. These lines are wider and stronger than any previously measured in the quiescent interstellar gas in the halo and disk of the Milky Way and of external galaxies

Pettini, M.↗

NASA NTRS1985

Detection and analysis of photospheric CNO features in the ultraviolet spectrum of the hot DO white dwarf PG 1034 + 001

An analysis of PG 1034 + 001 extended to include the high-dispersion IUE spectra and the high-resolution optical multiple-mirror telescope echelle spectra is discussed. The observations reveal the presence of absorption lines (C IV at 1548 and 1551 A, N V at 1238 and 1242 A, and O V at 1371 A) from highly ionized species with large redshifts (+ 40-50) km/s) relative to the interstellar lines. The results of a preliminary abundance analysis of the photospheric lines, together with the results of a search of sharp shortward-shifted features are presented. An interpretation of the observed abundances is made in terms of selective radiative forces acting in a high-temperature photosphere. Some speculations on the evolutionary status of DO stars like PG 1034 + 001 are given.

Sion, E. M.↗

NASA NTRS1987

The design and analysis of single flank transmission error tester for loaded gears

To strengthen the understanding of gear transmission error and to verify mathematical models which predict them, a test stand that will measure the transmission error of gear pairs under design loads has been investigated. While most transmission error testers have been used to test gear pairs under unloaded conditions, the goal of this report was to design and perform dynamic analysis of a unique tester with the capability of measuring the transmission error of gears under load. This test stand will have the capability to continuously load a gear pair at torques up to 16,000 in-lb at shaft speeds from 0 to 5 rpm. Error measurement will be accomplished with high resolution optical encoders and the accompanying signal processing unit from an existing unloaded transmission error tester. Input power to the test gear box will be supplied by a dc torque motor while the load will be applied with a similar torque motor. A dual input, dual output control system will regulate the speed and torque of the system. This control system's accuracy and dynamic response were analyzed and it was determined that proportional plus derivative speed control is needed in order to provide the precisely constant torque necessary for error-free measurement.

Bassett, Duane E.↗

NASA NTRS1986

Kitt Peak spectroscopy of P/Halley: October 1983-March 1985

Four low-resolution optical spectra of P/Halley obtained at heliocentric distances between 8.78 ad 4.83 AU using the cryogenic camera and R-C spectrograph on the 4 m Mayall reflector of Kitt Peak National Observatory are discussed. The resulting spectrogram shows a lack of the emission bands commonly seen in nearby cometary spectra. The optical color of Halley indicates that the comet is redder than the sun at less than 6000 A and slightly bluer above 6500 A. The substantial extent of the Halley dust coma is discussed, and an oxygen production rate of 3 x 10 to the 26th atoms/s at r = 4.83 AU is derived. These results are compared with those for other comets and those found for Halley by other authors.

Spinrad, H.↗

NASA NTRS1985

Metastability of the midgap level EL 2 in GaAs - Relationship with the As antisite defect

It is found that the rate of the photoinduced transition of the GaAs midgap level EL 2 to its metastable state increases as its occupation increases. High-resolution optical spectra of this transition exhibit a sharp peak very similar to the no-phonon line of the intracenter absorption of the As antisite defect. These findings show that the transition to the metastable state is initiated from the ground state 1A1, and it is finalized via the excited state 1T2 of the neutral As antisite defect. They thus provide a new basis for the critical assessment of the EL 2 metastability models and further confirmation of the association of EL 2 with the isolated As antisite defect.

Skowronski, M.↗

NASA NTRS1988

The bipolar outflow from the rotating carbon star, V Hydrae

A high-resolution optical spectrum of the mass-losing red giant carbon star, V Hya, has been obtained, and the (C-12)O (J = 1-0) millimeter emission in the circumstellar envelope around this star has been mapped. It is found that the CO emission is extended, clearly anisotropic and can be interpreted as the superposition of an isotropic emission with that of a bipolar flow. The optical spectrum of the photosphere suggests that this star is rotating with v sin i between 10 and 20 km/s. These data are interpreted, together, to suggest that the bipolar nature of the outflow results from the flattening of the star induced by its rapid rotation.

Kahane, C.↗

NASA NTRS1988

Nuclear emission-line intensities and profiles in NGC 3783

High-resolution optical spectrophotometry is presented for the nucleus of the Seyfert 1 galaxy NGC 3783. The data suggest that the broadest components of the forbidden lines have blueshifts relative to systemic velocity which are correlated primarily with ionization potential, and FWHMs which are correlated primarily with criticl density. Similar trends also exist in the line components responsible for the larger part of the line emission, but are not as strong as for the broadest line components. Comparison of the profiles of the Balmer lines indicates that the Balmer decrement measured from the H-beta/H-alpha ratio flattens in the line wings. However, the H-gamma and H-delta line profiles are more similar to the H-alpha line profile than to the H-beta line profile, suggesting that the H-beta profile may be anomalous.

Evans, I. N.↗

NASA NTRS1987

Mauna Loa Aerosol Backscatter Intecomparison Experiment (MABIE)

Measurements of CO2 aerosol backscatter coefficients and other aerosol physicochemical properties were obtained in remote Pacific free tropospheric airmasses at the Mauna Loa Observatory in Hawaii. The experiment used an attenuated total reflection impactor (Johnson et al., 1983), a dispersive infrared spectrophotometer, and a high-resolution optical particle counter. Preliminary results suggest that sulfate compounds dominate background backscatter properties at CO2 wavelengths between 9 and 10 microns.

Bowdle, David A.↗

NASA NTRS1989

Broad-line variability in NGC 3783

New intermediate-resolution optical spectrophotometry of the nucleus of the southern Seyfert 1 galaxy NGC 3783 is presented. These data demonstrate that the nucleus was in a very luminous state in May, 1983 manifested through considerably enhanced broad-line and optical continuum emission compared to the quiescent state evident in the data of Evans (1988) obtained in March, 1984. The two data sets are compared to derive the relative strengths of the continuum and broad-line intensities, and profile ratios are constructed for the H-alpha and H-beta Balmer lines to detect differences in the line profiles between the two epochs.

Evans, I. N.↗

NASA NTRS1989

The high-resolution spectrum of the pulsating, pre-white dwarf star PG 1159-035 (GW VIR)

High-resolution and low-resolution UV spectra and a high-resolution optical spectrum were obtained for PG 1159-035, revealing apparent photospheric absorption features with defined cores from N V 1240 A, N IV 1270 A, O V 1371 A, and C IV 1550 A. The photospheric velocity derived using all of these lines except for C IV is about +35 km/s. Equivalent-width measurements determined for all of the features may provide a tighter constraint on the photospheric temperature in a detailed model atmosphere analysis treating the CNO ions.

Liebert, James↗

NASA NTRS1990

Nucleation and growth control in protein crystallization

The five topics summarized in this final report are as follows: (1) a technique for the expedient, semi-automated determination of protein solubilities as a function of temperature and application of this technique to proteins other than lysozyme; (2) a small solution cell with adjustable temperature gradients for the growth of proteins at a predetermined location through temperature programming; (3) a microscopy system with image storage and processing capability for high resolution optical studies of temperature controlled protein growth and etching kinetics; (4) growth experiments with lysozyme in thermosyphon flow ; and (5) a mathematical model for the evolution of evaporation/diffusion induced concentration gradients in the hanging drop protein crystallization technique.

Rosenberger, Franz↗

NASA NTRS1990

The circumstellar environment of the emission-line star LkH-alpha 101

The environs of the premain-sequence, emission-line star, LkH-alpha 101, have been observed by broad-band CCD imaging, high-resolution optical spectroscopy, IRAS imaging, and single-dish, as well as interferometric, millimeter-line mapping. LkH-alpha 101 exhibits a high mass-loss rate (0.000011) low-velocity (350 km/s) ionized wind typical of early-type premain-sequence stars (Barsony, 1989). The millimeter interferometer maps show that this wind has cleared out a cavity in the molecular cloud surrounding LkH-alpha 101, allowing the rapid expansion of the previously observed VLA H II region (Becker and White, 1988).

Barsony, M.↗

NASA NTRS1991

High resolution lunar radar studies: Preliminary results

High resolution radar data for the lunar surface were acquired over 14 sites in June and November 1990 using the new 10 MHz data taking system at the Arecibo Observatory. The raw data collected for each site covers an area approximately 100 by 400 km and will be processed using delay-Doppler techniques into images of backscatter cross section with three fo four independent looks. All observations transmitted a circularly polarized signal and both senses of circular polarization were received containing the polarized and depolarized component of the backscatter signal. The relative power in these two polarizations provides useful information on properties of the surface, in particular surface roughness. The effort to date focused on the initial data analysis with new software written to perform a full synthetic aperture focusing on the raw radar data. This analysis will involve the use of complementary high resolution optical and topographic data sets to aid interpretation of surface scattering mechanisms.

Stacy, Nicholas J. S.↗

NASA NTRS1992

The structure of the BAL QSO 1700 + 518

The paper presents 0.5-arcsec-resolution optical images of the low-redshift, bright, broad-absorption-line QSO 1700 + 518. A bright arc 2 arcsec is found to the NE of the nucleus which is redder than the surrounding host galaxy. There is also a faint radial structure to the SE, which is aligned with the core radio structure. The principal radio structure is a slightly resolved component coincident with the optical nucleus and an unresolved lobe 1 arcsec to the W which has no corresponding optical structure. The morphological and other properties of the QSO are discussed.

Hutchings, J. B.↗

NASA NTRS1993

High-resolution study of luminous infrared galaxies. I - The composite nature of the Seyfert 1 galaxy IRAS 20044-6114 (NGC 6860)

The physical conditions in the ionized gas, the stellar population, and the kinematics of the Seyfert 1 galaxy IRAS 20044-6114 (NGC 6860) are studied by high spatial resolution optical imaging and optical and near-IR spectroscopy of this luminous IR source. The broadband images show a compact nucleus, two weak spiral arms, a bar, a bulge, an inner ring, and a possible outer ring. The I-alpha image reveals bright emission-line regions associated with the Seyfert nucleus and an inner ring of intense star formation. The forbidden O III 5007-A image shows that the high-excitation gas is elongated perpendicularly to the direction of the bar, and reveals a bright compact object at about 40 arcsec NE of the nucleus which is undetectable in the broadband images. This object is interpreted as a dwarf young H II galaxy. The optical, near-IR, and FIR results show clear evidence that the nuclear and circumnuclear regions have composite and complex structure: a variable Seyfert 1 nucleus embedded in an intense and dusty star formation. environment.

Lipari, Sebastian↗