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  • Weitere Quellen  (630)
  • NASA Technical Reports  (630)
  • ASTRONOMY  (630)
  • 1980-1984  (630)
  • 1984  (372)
  • 1983  (258)
  • 1
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    The PDS-VAX intelligent plate scanning system of Trieste Astronomical Observatory (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-02-14
    Beschreibung: An intelligent subsystem for interfacing a PDS1010A digital microdensitometer to a DEC DR11W DMA 16 bit UNIBUS port in DEC VAX VMS environment was tested. The subsystem employs two MOTOROLA M68000 microprocessors with 128 KB data memory. The PDS primitives and the user defined high level scanning functions and preprocessing modules are loaded from the host computer into two 8 KB RAM memories in the microprocessors using a dedicated PDS control language. The subsystem is planned to employ a nonstandard photomultiplier electronics. Two design schemes were tested: (1) based on three amplifiers of gain 10 cascaded and multiplexed to a 12 bit AD converter, and (2) based on a single amplifier of gain 100 and two 14 bit AD converters.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Goddard Space Flight Center Astron. Microdensitometry Conf.; p 175-187
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  • 2
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    STEP flight experiments Large Deployable Reflector (LDR) telescope (1984)
    In:  CASI
    Details
    Publikationsdatum: 2006-04-03
    Beschreibung: Flight testing plans for a large deployable infrared reflector telescope to be tested on a space platform are discussed. Subsystem parts, subassemblies, and whole assemblies are discussed. Assurance of operational deployability, rigidization, alignment, and serviceability will be sought.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Langley Research Center STEP Expt. Requirements; p 257-278
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  • 3
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    Infrared mapping of galaxian centers: Star forming regions with kiloparsec scale sizes (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: A 1 to 20 micron mapping of the centers of galaxies encompassing the regions that extend out to several kiloparsecs from the nuclei is reviewed. Power emerging at or = 5 microns is a direct measure of the number of young stars present. This conclusion is strongly supported by the large-scale association of the infrared-emitting regions with visual continuum and line emission indicative of young stars, and by the similarity of the energy distributions to those of Galactic HII region/molecular cloud complexes. Much of the young-star activity is completely hidden from view. At shorter wavelengths, a variety of processes, including bremsstrahlung, are evident.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Observatory Star Formation Workshop; p 183-198
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  • 4
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    The Gamma-Ray Observatory mission objectives and its significance for gamma-ray astronomy (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The Gamma Ray Observatory (GRO) is an approved NASA mission, programmed for launch in 1988. Its complement of four detectors has established goals: (1) to study the nature of compact gamma-ray sources such as neutron stars and black holes, or objects whose nature is yet to be understood; (2) to search for evidence of nucleosynthesis especially in the regions of supernovae; (3) to study structural features and dynamical properties of the Galaxy; (4) to explore other galaxies, especially the extraordinary types such as radio, Seyferts, and quasars; and (5) to study cosmological effects by examining the diffuse radiation in detail. This paper discusses the design, objectives, and expected scientific results of each of the GRO instruments in view of the GRO mission goals.
    Schlagwort(e): ASTRONOMY
    Materialart: Advances in Space Research (ISSN 0273-1177); 3; 10-12
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  • 5
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    The S201 far-ultraviolet imaging survey. II - A field in Cygnus (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Far-ultraviolet imagery of a region in Cygnus, a 20 deg diameter field centered near (1950) R. A. 21 h 31.2 m decl. +37 deg 25 arcmin, was obtained by the S201 far-ultraviolet camera during the Apollo 16 mission. In a 10 minute exposure covering the 1250-1600 A wavelength range (effective wavelength 1400 A), 730 star images can be detected, corresponding to a limiting ultraviolet magnitude of about m (1400) = 10. Assuming nominal interstellar extinction values in this region near the galactic plane, this result corresponds to the detection of A0 V stars to a distance of 300 pc and of B0 V stars to 1500 pc. Uncertainties in spectral classification and interstellar extinction for individual objects are probably more significant than calibration or measurement errors. Most of the objects detected are identified with stars in the Smithsonian Astrophysical Observatory Star Catalog (1966), or the Catalog of Stellar Identifications (1979) or both, but 87 objects remain unidentified (or are identified with late-type stars).
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 54; 271-290
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  • 6
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    Determining asteroid masses from perturbations on Mars (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The orbit of Mars is perturbed more than 5 m, a value compatible with the accuracy of the Viking Lander ranging data, by about three dozen asteroids. In addition to larger asteroids throughout the belt, significant perturbations of long period are generated by smaller objects near commensurabilities with Mars. The largest periodic terms induced by 1 Ceres and 2 Pallas have amplitudes of 0.8 and 0.2 km, respectively, both with 10-year periods. Due to a near commensurability, 4 Vesta causes a 5-km, 52-year term. While the Viking ranges will yield significant mass determinations for the largest three asteroids, and some of the smaller bodies should be detectable, it will be difficult to separate the smaller bodies with useful accuracies. Accurate discrimination must await range data from future missions to Mars or other bodies in the neighborhood of the asteroid belt. The Viking ranges can also yield improved masses for the outer planets (except Pluto), an application which is being exploited by groups analyzing these data. Uncertainties in the asteroid masses limit the ultimate accuracy of the Viking determinations of both the long time scale motion of the system of the inner four planets with respect to an inertial frame and the rate of change of the gravitational constant.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 57; 1-13
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  • 7
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    A search for the 10-micron silicate feature in periodic Comet Grigg-Skjellerup (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: A 10-micron spectrum of periodic Comet Grigg-Skjellerup was obtained on 22 June 1982 with the UCL array spectrometer at the United Kingdom Infrared Telescope, Mauna Kea. No emission feature is obvious in the spectrum. The observed spectrum can be fit equally well by a model of small hot absorbing grains or by a composite model with less than or equal to 30 percent (3sigma) warm, 'dirty' silicate grains. The latter model is consistent with the silicate abundance in Comet Kohoutek, which did display an emission feature at 10 microns.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 89; 170
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  • 8
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    Broad band X-ray astronomical spectroscopy (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: The Broad Band X-Ray Telescope (BBXRT) experiment has been designed for high sensitivity, moderate resolution spectrophotometry of cosmic sources in the range 0.5 to 12 keV. Principal elements are two co-aligned imaging telescopes with cooled Si(Li) detectors at each focus. The mirror design uses an approximate geometry of tightly nested, conical, foil reflectors that allow a large filling factor (high throughput) at small grazing angles (high energy response). Each detector consists of a cluster of five elements defined with grooves on a single crystal. This arrangement affords some spatial resolution as well as a means of substantial background reduction. Shuttle borne measurements will typically be of 2000 s duration for sources with a flux of 10 to the -12 erg/sq cm-s.
    Schlagwort(e): ASTRONOMY
    Materialart: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-31; 786-790
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  • 9
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    Ultraviolet spectra of planetary nebulae. X - Physical conditions in the compact planetary nebula Sw St 1 (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: Photoelectric visual and ultraviolet observations of the compact planetary nebula Sw St 1 are analyzed. The electron density, determined from the C III 1907/1909 A line ratio, is N(e) = (1.1 + or - 0.1) x 10 to the 5th/cu cm, consistent with the high emission measure and high critical frequency determined from observations of the thermal radio emission. The C/O abundance ratio in the nebula is found to be N(C)/N(O) = 0.72 + or - 0.1, i.e. the envelope is oxygen-rich, as suggested by the identification of the silicate feature in the 8-13 micron infrared spectrum. Difficulties remain in accurately determining the reddening constant to the nebula and its electron temperature.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 206; 293-304
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  • 10
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    Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 56; 393-397
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  • 11
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    Radioastronomical observations of comets IRAS-Araki-Alcock (1983d) and Sugano-Saigusa-Fujikawa (1983e) (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: Continuum and spectral-line radio observations of the comets IRAS-Araki-Alcock and Sugano-Saigusa-Fujikawa obtained at a number of observatories during May and June, 1983, are compiled in tables and briefly characterized. The species NH3, H2O, CO, and HCN are considered in detail; visible-range observations of CN are compared; and the implications of the results and the experience gained in performing and coordinating the observations for the detection of important species in other comets, especially Halley's Comet, are explored.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 60; 215-220
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  • 12
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    A search at the millijansky level for milli-arcsecond cores in a complete sample of radio galaxies (1984)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Beschreibung: A complete sample of 26 extended radio galaxies was observed at 2.29 GHz with the Mark III VLBI system. The fringe spacing was about 3 milli-arcsec, and the detection limit was about 2 millijanskys. Half of the galaxies were found to possess milli-arcsec radio cores. In all but three sources, the nuclear flux density was less than 0.04 of the total flux density. Galaxies with high optical luminosity (less than -21.2) were more likely than less luminous galaxies to contain a detectable milliparcsec radio core (69 percent vs. 20 percent). For objects with arcsec cores, 80 percent were found to have a milli-arcsec core, even though the milli-arcsec object did not always contribute the greater part of the arcsec flux density.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 284; 519-522
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  • 13
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    The evolution of the infrared emission from the Type II supernova 1980k in NGC 6946 - The dust formation model (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper presents 1-4 micron photometry of supernova 1980 k in NGC 6946 obtained over a period of 1 year following the outburst. During the period between 1980 November 1 and December 19, the infrared emission probably originated from the extended atmosphere of the expanding star. The JHKL colors and a 1.3-2.6-micron spectrum observed during this period correspond to those of a blackbody with an average temperature of about 5000 K. Observations around 1981 May 31 showed that the supernova developed an infrared excess after 1980 December. This infrared excess persisted through 1981 October and is consistent with the appearance of thermal emission from about 700 to 900 K dust in addition to a hotter photosphere. The similarity of this behavior to that of the infrared evolution of some novae suggests that dust formation may be occurring in the supernova ejecta. The hypothesis, that the emission arises from preexisting grains in a circumstellar shell which are heated by the supernova outburst, is also consistent with the data.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 274; 168-174
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  • 14
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    Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. III - Reticon radial velocities (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Radial velocities for 72 stars, most of them known or suspected binaries with F - K giant-supergiant primaries, are derived from Reticon spectra in the region 6005-6235 A at a scale of 7 km/s per diode. Cross-correlation of the spectra normally produces results accurate to better than 1.0 km/s. Eight new radial velocity variables are found (HR 2786, R Pup, HR 3291, HR 4451, HD 114520, HR 5667, HR 7014, and Nu1 Sgr). Improved orbits are determined for 15 known spectroscopic binaries, and provisional orbits are obtained for seven new spectroscopic binaries.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 53; 553-571
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  • 15
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    Infrared observations of RS CVn stars (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The paper presents infrared photometry of the RS CVn binary stars AR Lac (1.2-10 microns) and MM Her (1.2-3.5 microns) as they egressed from their primary and secondary eclipses; of the eclipsing systems RS CVn and Z Her at maximum light (1.2-10 microns) and of the non-eclipsing systems UX Ari and HR 1099 (1.2-10 microns). An analysis of these and published V data based on flux ratio diagrams (linear analogues of color-color diagrams) shows that G and K stars supply the infrared light of these systems. In AR Lac, the combined light of a G5-K0 subgiant and either a late F dwarf or an early F subgiant can account for the observed visual and infrared light curves. None of these systems shows infrared emission from circumstellar matter. This result is simply understood: dust grains would not be expected to form in the physical conditions surrounding the subgiant, and the corona and chromosphere (whose properties have been deduced from spectroscopic X-ray observations) should not produce appreciable infrared emission.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 205; 859-873
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  • 16
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    Ultraviolet high-resolution spectroscopy from the Space Telescope (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The High Resolution Spectrograph is one of five scientific instruments which will be part of the Space Telescope observatory. The spectrograph was designed to take advantage of the imaging and pointing capabilities of the telescope to obtain ultraviolet spectra with spectral resolution comparable to large, ground-based coudeinstruments. Some of the results of the ground-based testing program will be described, along with applications of these properties to future science programs.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 95; 543-549
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  • 17
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    Theoretical studies of the effects of grain noise on photographic stellar astrometry and photometry (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A method of incorporating the effects of photographic emulsion grain noise into digital image centering algorithms is presented which improves the accuracy of the derived stellar positions and magnitudes. Theoretical formulae are then derived for the limiting error of the center, and the photometric parameters. For IIIa-J, this error is 0.2-0.3 mu for bright unsaturated images, which agrees quite well with measurements made with the Yale PDS microdensitometer. It is expected that, with further improvements in the positional accuracy of the PDS, it should be possible to reach the emulsion grain noise limit, providing that emulsion shifts or other large scale errors do not dominate. It is also shown that, with appropriate trimming, marginal distribution image centering algorithms can yield an accuracy only slightly poorer than that obtained with two-dimensional distributions.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; 1683-168
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  • 18
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    An improved celestial radio reference frame: JPL 1982-4 (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: In the development of a celestial radio reference frame, there are now over 100 sources whose relative positions are known with an average uncertainty less than 5 milliarcseconds. These sources are fairly uniformly distributed over the celestial sphere north of -40 deg declination. Their positions are expressed in the new IAU system. This presentation describes the analysis involved in obtaining these results, as well as future plans for linking this system to the JPL planetary ephemerides.
    Schlagwort(e): ASTRONOMY
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  • 19
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    New infrared observations of IRS1, IRS3, and the adjacent nebula in the OMC-2 cluster (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of the infrared cluster of low luminosity protostars in Orion Molecular Cloud 2 (OMC2) are reported. Results show that the asymmetric distribution of the extended emission seen about IRS1 is another infrared reflection nebula. Energy distributions show that the spectral shape is fairly constant throughout the nebula which indicates there is little internal extinction within this region. Integrated surface brightness values show that the nebula is 5 times brighter than IRS1 at K. Energy distributions show that IRS1 has a more pronounced ice band absorption feature at 3.1 micron; suggesting that there is more extinction along the direct line of sight to IRS1 than along a line from IRS1 to the scattering grains and then to the observer. The distribution of the extended emission around IRS1 is similar to the reflection nebula seen in NGC 7538 (Werner et al. 1979). The asymmetric shapes of the two nebulae are similar and in each case there is excess extinction along line of sight to the illuminating source.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Observatory Lab. and Observational Infrared Spectra of Interstellar Dust; p 162-166
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  • 20
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    Transient dips of Cygnus X-1 observed from Tenma (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The transient intensity dips of the binary system Cyg X-1 have been observed, using the gas scintillation proportional counter (GSPC) array onboard the Tenma X-ray astronomy satellite. The duration of the dips was in the range from several seconds to 10 minutes, with several dips occurring as much as 15 h before the superior conjunction. Within the dips, complex structures were observed with time scales of several seconds, and, in at least one case, shorter than two seconds. For a dip lasting longer than 10 minutes, a high-quality spectrum was obtained which reveals the K-absorption edge of iron at 7.18 + or - 0.18 keV. On the basis of the observed absorption, it is suggested that the dips are caused by absorption due to relatively cool matter (less than about 30,000 k); the low-energy excess observed during the dips is due either to an extended soft X-ray emitting corona or to partial obscuration of the X-ray source by multiple blobs. From the time structure of the dip, a blob size of the order of 10 to the 9th cm is derived.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Society of Japan, Publications (ISSN 0004-6264); 36; 4, 19
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  • 21
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    IUE observations of the 'Butterfly' Nebula M2-9 (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: IUE observations of the peculiar 'Butterfy' nebula M2-9 indicate that it is not a normal planetary nebula. The ultraviolet spectrum is characterized by few emission lines and a weak continuum. Mg II 2800 A is the strongest emission line present and may be indicative of a binary nucleus. Lines of N v, Q I, N III, N IV, Si III, and C III are seen, but C IV and O III are conspicuous by their absence. T(e) = 10,250 + or - 400 K was determined for the core. Nitrogen in the core is found to be overabundant by about a factor of 5 over the solar value. M2-9 may be an object in the early stages of becoming a planetary nebula.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 287; 353-358
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  • 22
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    Cometary showers and unseen solar companions (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The possibility that an invisible solar companion passing through the Oort cloud every 28 Myr precipitates a sufficiently high rate of cometary collisions with the earth to account for periodic mass species extinctions recorded in the fossil record is discussed. A Monte Carlo simulation shows that any hypothesized 'death star' with a 28 Myr orbit would experience an average 10 percent change in period per orbit. Production of an 18-fold increase in cometary impacts would be associated with a 0.055 probability that a 10 km nucleus would hit the earth in a shower once every 510 Myr, longer than the proposed extinction periodicity. However, if the death star orbit has a 0.6 eccentricity and the Oort cloud is sufficiently densely populated, a 2 billion comet shower may be possible. A survey of large terrestrial impact craters indicates that 6-12 craters with diameters over 10 km originated in periodic showers. The extinctions in any case occur at 26 Myr periods and cannot be correlated with the 33 Myr period of recrossing the galactic plane, or with any other known phenomena.
    Schlagwort(e): ASTRONOMY
    Materialart: Nature (ISSN 0028-0836); 312; 380; Rep
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  • 23
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    Evidence for material between Saturn's A and F rings from the Voyager 2 photopolarimeter experiment (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The region in the Saturn system between the F ring and the outer edge of the A ring is an area that appears, in images from the imaging experiment, to be virtually devoid of material except for three small satellites. Near the orbit of 1980S28, Atlas - the innermost satellite - the Voyager Photopolarimeter Stellar Occultation data show a discontinuity in count rate which marks a boundary between the tenuous material near the outer edge of the A ring and the orbit of Atlas. The data pertaining to this region have been examined with the aid of statistics and models generated from other similar ring structures. It is concluded that the discontinuity is real, implying the existence of tenuous material of normal optical depth of 0.01 to 0.006 in this region.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 60; 409-415
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  • 24
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    1984 AB - A unique Mars-crossing asteroid (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Asteroid 1984 AB, discovered in January 1984, proved to be a unique object with a close dynamical relationship to Mars. A brief history of the discovery and subsequent 'evolution' of the orbit as it was refined is presented. The preliminary orbit of 1984 AB indicated that it might be a Mars Trojan, and an extended discussion of this interesting possibility is presented, but this hypothesis had to be dismissed after further observations had refined the orbit. The semimajor axis and orbital eccentricity are very similar to that of Mars. No other known Mars-crossing asteroid exists with an orbit as closely associated to Mars.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 60; 404-408
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  • 25
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    A radar study of Comet IRAS-Araki-Alcock 1983d (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Radar echoes from Comet IRAS-Araki-Alcock at wavelengths 3.54 and 12.9 cm indicate that the comet's nucleus is very rough on a scale larger than the radar wavelengths; however, the low polarization ratio (25 percent at 3.54 cm) indicates that the scattering is not dominated by multiple reflections, internal reflections, or large abundances of sharp edges, cracks, and pits. The shape of the nucleus probably departs greatly from a sphere with average radii near 3-4 km. The nucleus does not appear to look significantly different from a number of Apollo and Amor asteroids except that: (1) there is a suggestion that minor structure moves rapidly across the spectra, and (2) the debris not gravitationally bound to the comet was detected, and contributes 25 percent of the total radar cross section at the 12.9-cm wavelength. Other considerations suggest that the pole was at least 45 deg away from the line of sight on two days of observation, and that the rotation period is approximately 1-2 days.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 89; 1745-175
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  • 26
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    A solar spectral line list between 10 and 200 A modified for application to high spectral resolution X-ray astronomy (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A spectral line list for the 10-200 A range is developed from existing solar spectra for application to high spectral resolution measurements of astrophysical plasmas. The solar spectral line lists are merged into a single comprehensive list. The effect of the solar emission measure distribution is removed from the line intensities, which results in a set of emission rates for the lines that can be applied to many optically thin, low density high temperature plasmas in ionization equilibrium. In addition to the measured solar lines, 250 theoretical lines are added to this list. These lines fall in wavelength regions where the existing solar lists have few lines because of limitations in instrumental sensitivity. Also, some lines have been added because the sun has very little plasma at temperatures of about one million K, and consequently these lines are weak or absent in solar spectra. The entire list contains about 600 lines. Finally, predicted spectra of the two RS CVn stars, alpha Aur (Capella) and UX Ari, are presented at 1 and 0.25 A spectral resolution. Also, the solar spectrum is shown at 1 A resolution, and the emission rate spectrum (spectrum not modified by an emission measure distribution) is shown at very high spectral resolution. The predicted spectra for Capella and UX Ari are based on results obtained from the Einstein and International Ultraviolet Explorer (IUE) spacecraft.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 56; 67-89
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  • 27
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    Reduction of astrographic catalogues (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An automatic program for the reduction of overlapping Carte du Ciel plates is described. The projection and transformation equations are given and the RAA subprogram flow is outlined. The program was applied to two different sets of data, namely to nine overlapping plates of the Cape Zone of the CdC, and to fifteen plates taken with the CIDA-refractor of the open cluster Tr10.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 99-104
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  • 28
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    Obtaining accurate comet positions despite some inaccurate catalog stars (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: From an astrographic negative a grid is determined from measurement of all the reference stars and using their catalog positions, and other grids from selections of reference stars. These grids are determined from many stars, and individual stars will have errors with respect to the grid. There are ways to identify stars X that are not at their cataloged position: (1) determine the focal length of the telescope from the measurements of each pair of stars and look for discordant results; (2) stars X are several arcseconds off the grid, and the other stars fit better when stars X do not help determine the grid; and (3) the grid is stretched or distorted to include the stars X. Fifteen to twenty percent of the stars in the S.A.O. catalog are 1.5 seconds or more off their catalog positions. An interactive session with a computer can find and eliminate these errant stars and result in more accurate comet positions.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 96-98
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  • 29
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    Desired characteristics of catalogs for cometary astrometry (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Reference star catalogs for cometary astrometry have to provide an all-sky coverage with suitable stellar density and limiting magnitude on a fundamental coordinate system. A general catalog meeting all these requirements will not be available for a foreseen timescale. The suitability of various existing catalogs for cometary astrometry is discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 87-92
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  • 30
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    The astrometry network of observers in USSR (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A list of observatories included in the Soviet Astrometry Network is given. Some aspects of Astrometry Network activity are discussed. The Comet Halley star catalog is outlined.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 76-83
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  • 31
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    The IHW reference star catalogs for Comets Halley and Giocobini-Zinner (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The general categories of catalogs are observed and compiled. Observed catalogs are tabulations of positions determined with a single instrument (transit circle or astrograph) at a single location with a single approximate mean epoch. Compiled catalogs are produced from a combination of observed catalogs and have the advantage of many more observations per star. In addition, catalogs may be classified according to their density and type of instrument used to produce them. The specific catalogs that should be used for Halley's Comet and Giaobini-Zinner Comet are described.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 93-95
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  • 32
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    The astrometry network of observers in Japan (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The astrometric network of observers and the main telescopes for professional and amateur astronomers in Japan and their availability for the International Halley Watch (IHW) are described.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astometry; p 74-75
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  • 33
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    The astrometry network of observers in China (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: In China, the Purple Mountain Observatory (32 deg. 04 min. N and 118 deg. 49 min. E), the Shanghai Observatory (31 deg 06 min N and 121 deg 11 min E), and the Qingdao Station (36 deg 05 min N and 120 deg 19 min E) will take part in the astrometry of Halley's Comet. The astrometric work together with the instrumentation used, is given.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 71-73
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  • 34
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    The astrometry programme at Mt. John Observatory (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The comet (and minor planet) astrometry program uses one of two 0.6 meter (24 in.) Cassegrain telescopes at Mt. John University Observatory. For astrometric photographs of comets and minor planets a simple guide probe camera is attached to the Cassegrain. Frequently the Cassegrain field does not include sufficient cataloged stars for a satisfactory reduction. In these cases the comet position is transferred to an astrograph plate. Ephemeris data are calculated to the tenth of a day nearest the meridian transit of the object or for dusk or dawn twilight for low objects. Star measurement and identification are checked by reducing positions of cataloged stars.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 66-70
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  • 35
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    Problems and procedures of cometary astometry (1984)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Photography of comets or asteroids for the purpose of astrometry requires consideration of a few details not met with in other astronomical problems. In the general case the object has a substantial non-sidereal motion and the decision must be made whether to track on the fiducial stars or on the object. The best method for introducing the required image motion compensation to the detector will depend on the focal plane facilities. Measurement of elongated images and the problems involved are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 58-65
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  • 36
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    Kitt Peak measurements of P/Halley positions (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Techniques used for the acquisition and reduction of imaging data for astrometric positions of comet Halley at Kitt Peak National Observatory are described. These techniques are applicable to the comet while it is fainter than magnitude V approximately 21. They yield positions that are uncertain by + or - 0.9 arcsec. The reliability and consistency of the positions already derived could be improved by as much as a factor of four in a more ambitious astrometric program.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 48-57
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  • 37
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    Astrometric plates obtained at the primary focus of large aperture reflectors (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Coma, astigmatism, and great differences in stellar magnitudes between photographed object and reference stars constitute the main sources of errors in measuring positional plates. These three sources of error can easily be eliminated by the method used at the Klet Observatory for obtaining precise observations of faint objects. The astrometric plates are taken by the method of two diaphragms. The first diaphragm, with a small central aperture; is located in front of the photographic plate. The second diaphragm is situated in front of the mirror. By a very short (of the order of tens of seconds) exposure a sufficient number of reference stars can be obtained throughout the entire plate. The stars are very well defined to the very edge of the plate and are easy to measure. Moreover, this method makes it possible to use plates of larger dimensions than usual so that it is always possible to find the necessary reference stars.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 45-47
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  • 38
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    Cometary astrometry with Schmidt cameras (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A great many of the professional comet discoveries are made using wide field Schmidt telescopes. In particular the Palomar Schmidt, the ESO Schmidt in Chile and the UK Schmidt at Siding Spring Observatory in Australia. The wide field of view and fast f ratio are two of the distinctive features of this design which make it attractive for comet work. The techniques described refer to those in current use on the UK Schmidt. However in large part the methods described may be applied quite widely.
    Schlagwort(e): ASTRONOMY
    Materialart: JPL Cometary Astrometry; p 34-40
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  • 39
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    Experiments to test theoretical models of the polarization of light by rough surfaces (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A number of attempts have been made to provide theoretical models of the physical processes involved in the polarization of light scattered by a rough surface, such as the regolith of an atmosphereless planet. Some laboratory experiments designed to test different aspects of these models are described. It is concluded that double Fresnel reflection is usually the dominant process in producing negative polarization, but that diffraction effects may play a significant part in double events involving small-scale surface features.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 89-112
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  • 40
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    Comet Halley ephemeris uncertainties in 1985-1986 (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: For the planned flyby missions to Comet Halley in March 1986, the comet's ephemeris uncertainties completely dominate the spacecraft-comet miss distance. In an effort to determine realistic Comet Halley ephemeris uncertainties, a statistical covariance analysis was conducted using the actual data in 1909-1910-1911 and simulated data in 1984-1985-1986. In 1985-1986, Comet Halley's ephemeris uncertainties are very sensitive to the comet's orbital position, the optical data noise, data schedule, and whether or not the old data is included in the orbital solutions. The comet's ephemeris uncertainties in March 1986 are relatively insensitive to reasonable center of light/center of mass offsets and also to possible radar data taken in late November 1985. Accurate Space Telescope observations made in early March 1986 might significantly improve upon the comet's position uncertainties for the various intercepting spacecraft.
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    Dust particles in the anomalous tail of Comet Kohoutek (1973 XII) (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Intermediate results from theoretical models of the anomalous spikelike dust distribution observed in the tail of Comet Kohoutek using the Skylab white-light coronograph on December 28.996, 1973, are reported. The time evolution is studied using the model of Finson and Probstein (1968) and assuming power-law variation of the dust-production rate and the particle-size distribution. Brightness profiles are calculated and presented graphically for comparison with those derived from the observation photograph: the model predicts a longer duration of the spike phenomenon than was observed. It is shown qualitatively that this discrepancy can be removed by introducing a finite dust-emission velocity (e.g., 1 m/s) into the model.
    Schlagwort(e): ASTRONOMY
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  • 42
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    Cometary nucleus and active regions (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: On the basis of the icy-conglomerate model of cometary nuclei, various observations demonstrate the 'spotted' nature of many or most nuclei; i.e., regions of unusual activity, either high or low. Rotation periods, spin axes, and even precession of the axes have been determined. Narrow dust jets near the nuclei of some bright comets require that small sources be embedded in larger active areas. Certain evidence suggests that very dusty areas and very dusty comets may be less active, respectively, than surrounding areas or other comets.
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  • 43
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    Cryogenic telescope on the Infrared Astronomical Satellite (IRAS) (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Infrared Astronomical Satellite (IRAS) has completed an unbiased all-sky survey at wavelengths from 10 to 100 microns. The design and performance of the focal plane array is described with emphasis on in-orbit measurements of the sensitivity and stability. In the four broad spectral bands centered at 12, 25, 60, and 100 microns, the system noise equivalent flux density (NEFD) values are in Jy/(Square root of Hz), 0.03, 0.025, 0.046, and 0.21, respectively (Jansky = 10 to the -26th W/sq m/Hz). For point sources, a single scan at the survey rate of 3.8 arcmin/s yields limiting flux densities at the 3-sigma confidence level of 0.36, 0.30, 0.39, and 1.2 Jy. The dc stability of the junction field effect transistor (JFET) amplifiers and the excellent off-axis rejection of the telescope permit total flux measurements of extended infrared emission at levels below 6,000,000 Jy/sr. Response of the extrinsic silicon and germanium photo-detectors to ionizing radiation is described.
    Schlagwort(e): ASTRONOMY
    Materialart: Optical Engineering (ISSN 0091-3286); 23; 122-127
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    Preliminary scientific results from the first six months of the Infrared Astronomical Satellite (IRAS) (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The Infrared Astronomical Satellite (IRAS) was successfully launched on January 25, 1983. This paper presents results based on analysis of early scientific data returned from IRAS. Among the early results of IRAS are the discovery of comet IRAS-Araki-Alcock, evidence for a shell of large particles around the nearby bright star Vega, detection of stars in the process of formation, and detection of many infrared bright galaxies. These early results demonstrate that the IRAS data will be a treasure chest for astronomers for years to come.
    Schlagwort(e): ASTRONOMY
    Materialart: Optical Engineering (ISSN 0091-3286); 23; 128-130
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  • 45
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    Regions of stability of asteroids (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Using Hill's modified stability criterion, regions of orbital elements are established for conditions of stability. The model of the three-dimensional restricted problem of three bodies is used with the sun and Jupiter as the primaries. Four different cases are studied: direct and retrograde, outside and inside asteroidal orbits. The directions of the asteroidal orbits refer to the synodical reference frame and the positions refer to Jupiter's orbit. The orbital parameters of the asteroids are the semi-major axis (a), the eccentricity (e), and the inclination from Jupiter's orbital plane (i). The argument of the perihelion and the longitude of the ascending node are fixed at Omega = omega = 90 deg and the time of perihelion passage is T = 0 for all orbits.
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    The photometric method of detecting other planetary systems (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Rosenblatt (1971) has conducted an investigation regarding the use of photometric techniques to detect other planetary systems by searching for changes in starlight caused by the transit of a planet. The obtained results suggest that neither the intrinsic variation of the starlight nor the transmission fluctuations in the terrestrial atmosphere would prevent detection of planets as small as Mars with telescope apertures of 40 to 60 cm. The present investigation shows that Rosenblatt's results are too optimistic even for present-day differential photometric techniques. However, it appears that the detection of planets at least one-third the size of Jupiter is feasible, if a photometer with the required precision can be developed, taking into account the availability of a wide-angle telescope with a 1- to 2-m aperture.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 58; 121-134
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  • 47
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    The JPL 'long ephemeris', DE102/LE51 (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A number of applications exist in astronomical research for planetary and lunar ephemerides covering an extended length of time. This paper discusses such a set of ephemerides, DE102/LE51, produced at JPL, covering the time 1411 B.C. to 3001 A.D. The ephemerides are dynamically self-consistent, in that the equations of motion were integrated simultaneously. They also represent the most accurately known positions covering such a time span. They have already been used by a number of different users in a variety of different applications.
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  • 48
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    The S201 far-ultraviolet imaging survey. III - A field in Sagittarius (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Far-ultraviolet imagery of a 20 deg diameter field in Sagittarius, centered near (1950) R.A. 18 h 34 m, decl. -30 deg 25 arcmin, was obtained by the S201 far-ultraviolet camera during the Apollo 16 mission. In a 10-minute exposure covering the 1250-1600 A wavelength range, 1034 star images are detectable, with a limiting ultraviolet magnitude of about 10. Most of these objects are identified with early-type stars listed in the Smithsonian Astrophysical Observatory Star Catalog, the Catalog of Stellar Identifications, or both, but 203 objects remain unidentified or are identified with late-type stars. The photometric measurements appear to be in reasonable agreement with those of the International Ultraviolet Explorer for stars in common, and with expectations for A0 stars. A detailed photometric study was made of the Messier 8 region, and it is concluded that dust-scattered starlight contributes about half of the total radiation observed from the central region of M8.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 55; 101-125
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  • 49
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    Angular momentum drain - A mechanism for despinning asteroids (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The new mechanism of angular momentum drain is proposed to account for the relatively slow rotation rates of intermediate-sized asteroids. Impact ejecta on a spinning body preferentially escape in the direction of rotation, systematically draining away spin angular momentum and leading to the counterintuitive result that collisions can reduce the spin of midsized objects. The existing theory of asteroid rotation is reviewed, and the escape of ejecta from hypervelocity impacts on bodies of different sizes and physical properties is described. The effect of this mass loss on asteroidal rotation is calculated and shown to be a significant brake on the spins of intermediate-sized asteroids. Finally, this new process is incorporated in a revised theory of collisional evolution, its predictions are compared with observational data, and its applications are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 57; 464-476
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  • 50
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    The motion of the earth-moon system in modern tabular ephemerides. II - Inertial motion, mean longitude of the sun, and general precession in longitude (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Properties of astronomical time scales (ET and UT) are considered, with particular emphasis on correctly determining of-date longitude as the sum of inertial mean longitude of the sun relative to the mean equinox of a fixed epoch (1950.0), and the general precession in longitude accumulated since the epoch. The inertial mean longitude and motion (relative to the mean equinox) are derived from tabular ephemerides such as the Jet Propulsion Laboratories' DE 102 and DE 96, by comparisons with subroutines based on Newcomb's perturbation theory. An unresolved inconsistency of approximately 1 second per century among the mean inertial motion of DE 102, IAU precession speed (1976), and the classical Newcomb of-date mean motion is found. Interpretation difficulties arising from the use of different systems of Ephemeris Time are also discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 130; 2, Ja
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    Very large array observations of Jupiter's nonthermal radiation (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The VLA has been used at 18 and 20 cm to obtain observational data on Jupiter at all rotational aspects in all four Stokes parameters, yielding maps of the total, linearly polarized and circularly polarized intensity with a resolution of 0.25 Jupiter radii. These maps reveal such previously undetected phenomena as an emission feature close to the planetary surface north and south of each of the two main radiation peaks. The emission from 1.8 to about 3 Jupiter radii from the planet's center is sharply confined to the magnetic equator.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 54; 405-419
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  • 52
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    Dynamical evolution of the Oort cometary cloud (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The dynamical evolution of comets in the Oort cloud under the influence of stellar perturbations has been modeled using Monte Carlo techniques. It is shown that the cloud has been depleted over the history of the solar system. Comets are lost from the cloud by direct ejection due to close stellar encounters, diffusion of aphelia to distances beyond the sun's sphere of influence, or diffusion of perihelia into the planetary region where Jupiter and Saturn perturbations either eject them on hyperbolic trajectories or capture them to short-period orbits. The population of the cloud is estimated to be 1.0 - 1.5 x 10 to the 12th comets and the total mass is on the order of 1.9 earth masses. In addition to random passing stars, less frequent encounters with giant molecular clouds may play a significant role in randomizing the orbits of comets in the cloud and reducing the effective radius of the sun's sphere of influence.
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    Observations of comet IRAS-Araki-Alcock 1983d (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Observations of comet IRAS-Araki-Alcock 1983d in the infrared region from 12 to 100 microns are reported. The dominant feature seen in the infrared is an extensive dust tail not reported in visual observations. A dust production rate of 200 kg/s is deduced. The far-infrared spectrum suggests that the radius of a mean grain decreases from 30 to 5 microns along the tail.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 278; L11-L14
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    The infrared properties of galaxy clusters - IRAS observations of the Hercules Cluster (Abell 2151) (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: A total of 41 sources have been detected at 60 microns to a level of 50 mJy in a 1.6 x 0.5 deg field centered on the rich galaxy cluster Abell 2151. Twenty-four of these sources can be identified with late-type spiral galaxies of estimated photographic magnitude 17 or brighter. Galaxies classified as E or S0 are notably absent in the infrared data. Within the field, eleven of the IRAS sources cannot be easily identified with galaxies in the Hercules Cluster. If the brightest 60 micron cluster source (NGC 6045) is neglected, the integral luminosity function in the far-infrared can be fitted well with two power laws of slope -1.1 and -2.5.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 278; L75-L78
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  • 55
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    Close encounters and collisions of comets with the earth (1984)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A computer search for earth-approaching comets among those listed in Marsden's (1983) updated orbit catalog has identified 36 cases at which minimum separation distance was less than 2500 earth radii. A strong representation of short period comets in the sample is noted, and the constant rate of the close approaching comets in the last 300 years is interpreted to suggest the lack of long-period comets intrinsically fainter than an absolute magnitude of about 11. A comet-earth collision rate derived from the statistics of these close encounters implies an average period of 33-64 million years between any two events. This rate is comparable with the frequency of geologically recent global catastrophes which appear to be associated with extraterrestrial object impacts, such as the Cretaceous-Tertiary extinction 65 million years ago and the late Eocene event 34 million years ago.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 89; 154-161
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    Properties of young clusters near reflection nebulae (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Near infrared observations in the reflection nebulae NGC 703, 2023, and 2068 are used to study clusters of young stars found associated with these nebulae. At least 30 percent to 60 percent of these stars are pre-main sequence objects, as indicated by their infrared excesses, hydrogen line emission, or irregular variability. The spatial distributions and observed luminosity functions of these young open clusters are derived, and the inferred mass function and star formation efficiencies are discussed. Previously announced in STAR as N83-25628
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; July 198
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    Cometary impacts with the sun - Physical and dynamical considerations (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Michels et al. (1982) observed the apparent impacting of the sun by a comet, and Sekanina (1982) showed that the comet, 1979XI, was probably a member of the Kreutz group of sun-grazing comets, although its perihelion of 0.35 solar radii was much smaller than the 1.2-1.9 solar radii common for this comet class. The perihelion change cannot be explained by planetary, stellar, or nongravitational perturbations. The most plausible explanation is collision with another body, probably a comet, at large heliocentric distance. The probability of such an event is, however, extremely small. The sublimation of the comet's nucleus before impact is discussed, and it is suggested that its ultimate destruction probably resulted from the shock of entry into the denser regions of the solar atmosphere, just above the photosphere.
    Schlagwort(e): ASTRONOMY
    Materialart: Icarus (ISSN 0019-1035); 55; Sept
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    An infrared study of the eclipsing dwarf nova U Geminorum (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: One series of data comprising the present J, H, K broadband IR photometry of the cataclysmic binary system U Geminorum over the course of two orbital cycles was obtained several days before an outburst, while a second was gathered when the system had almost completely returned to quiescence from that outburst. In quiescence, the M4-M5.5 red dwarf star supplies most of the IR luminosity of the system, while the light curves at this time are tidally induced ellipsoidal variations of the red dwarf which exhibit an amplitude such that the red dwarf must fill, or nearly fill, its Roche lobe. This shows directly that Roche lobe overflow is important in cataclysmic variable stars. The range of the disk IR colors after outbursts suggest that cool and optically thick gas, together with optically thin gas, supply most of the IR light of the disk.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 204; Sept
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    Very large spiral galaxies (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: As a first step in the systematic study of large spirals, which may be useful in cosmological tests and studies of galaxy evolution, a catalog of the 107 largest known spiral galaxies is presented. Catalog galaxies have isophotal diameters greater than 90 kpc, assuming an H(zero) value of 50 km/sec per Mpc. UBVR photoelectric photometry is presented for 20 of these galaxies, and absolute magnitudes are derived for all galaxies in the catalog by transforming Zwicky magnitudes to the B(T) system.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 204; Sept
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  • 60
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    Further studies on criteria for the onset of dynamical instability in general three-body systems (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Numerical experiments designed for the elucidation of the conditions under which self-gravitating, three-body systems become dynamically unstable are examined of the cases of four orbital configuration types: circular, prograde, and coplanar; circular, retrograde, and coplanar; circular, direct, and inclined; and eccentric, direct, and coplanar. Results indicate that orbital inclination does not significantly affect stability in 'outer planet' configurations, while the stability of 'inner planet' configurations, where the tertiary is in close orbit about one member of the binary, is markedly less affected, once the relative orbital inclination is greater than 50 deg. It is found that the onset of dynamical instability is only weakly dependent on the eccentricity of either the binary or tertiary orbit, as long as the mass of the tertiary is comparable to the reduced mass of the binary.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; Sept
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    DE 102 - A numerically integrated ephemeris of the moon and planets spanning forty-four centuries (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: It is pointed out that the 1960's were the turning point for the generation of lunar and planetary ephemerides. All previous measurements of the positions of solar system bodies were optical angular measurements. New technological improvements leading to immense changes in observational accuracy are related to developments concerning radar, Viking landers on Mars, and laser ranges to lunar corner cube retroreflectors. Suitable numerical integration techniques and more comprehensive physical models were developed to match the accuracy of the modern data types. The present investigation is concerned with the first integrated ephemeris, DE 102, which covers the entire span of the historical astronomical observations of usable accuracy which are known. The fit is made to modern data. The integration spans the time period from 1411 BC to 3002 AD.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 125; 1, Au; Aug. 198
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    The IRAS telescope (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: The IRAS telescope is described in terms of its system configuration and physical characteristics, subsystem functions and descriptions, and performance characteristics. The mission and the configuration are reviewed briefly, and the major functional components of the telescope are described, including the focal plane assembly, the optics, the electronics, the cryogenics, and the thermal control. Exploded and cross-sectional views and block diagrams are presented for the telescope system configuration, focal plane assembly, infrared subarray module, optical subsystem, infrared channel data flow, and main cryogen dewar. The telescope physical characteristics are listed. The performance characteristics are listed and discussed, including the spectral response, sensitivity, optical quality, and photometric accuracy. Relative system spectral response curves for the infrared bands are shown.
    Schlagwort(e): ASTRONOMY
    Materialart: vol. 36; Jan. 198
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  • 63
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    Coordinate systems (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Jovian coordinate systems are different from those employed in the case of the earth. Latitude and longitude coordinates are usually established relative to some solid surface. Because Jupiter does not have a solid surface (at least none which is visible through the clouds), arbitrary, but convenient, coordinate grids have been prescribed. A spin equator is made out from observations of cloud motion, and the direction of the planetary spin axis is, therefore, determined with relatively good accuracy. The problem in establishing a Jupiter longitude system is that the mean rotation period of the clouds is a function of latitude. The solution selected was to define two separate longitude grids. A third longitude system became necessary with the detection of radio signals which gave evidence for a rotating planetary magnetic field. Attention is also given to orbital phase angle and longitude conventions for satellites, and two latitude systems for Jupiter
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    Transformations of the perturbed two-body problem to unperturbed harmonic oscillators (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: Singular, nonlinear, and Liapunov unstable equations are made regular and linear through transformations that change the perturbed planar problem of two bodies into unperturbed and undamped harmonic oscillators with constant coefficients, so that the stable solution may be immediately written in terms of the new variables. The use of arbitrary and special functions for the transformations allows the systematic discussion of previously introduced and novel anomalies. For the case of the unperturbed two-body problem, it is proved that if transformations are power functions of the radial variable, only the eccentric and the true anomalies (with the corresponding transformations of the radial variable) will result in harmonic oscillators. The present method significantly reduces computation requirements in autonomous space operations.
    Schlagwort(e): ASTRONOMY
    Materialart: Celestial Mechanics (ISSN 0008-8714); 30; May 1983
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    Revised orbits for 105 Herculis and Pi Cephei A and a model for the Pi Cephei system (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: New orbital elements for the giant primary components of 105 Herculis and Pi Cephei A are derived using radial velocities from Dominion Astrophysical Observatory coude plates. These data are combined with those of Harper (1925) in order to estimate the velocity amplitude of Pi Cephei A in the visual orbit of this triple system. Two models of this system are developed. In the first model, the unseen spectroscopic secondary component is a single main-sequence star, although this seems unlikely, while in the alternative model the unseen secondary component is itself double.
    Schlagwort(e): ASTRONOMY
    Materialart: Royal Astronomical Society; vol. 203
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    Lunar luminescence measurements (1983)
    In:  CASI
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    Publikationsdatum: 2016-06-07
    Beschreibung: Spectra of lunar sites obtained in June 1983 have been analyzed for residual luminescence using the spectral line depth technique. The results or three sites each at three wavelengths are presented. The sites observed were Mare Crisium, Kepler, and Aristarchus. In each case, the value quoted was based not only on the strong Fraunhofer line in the spectral range covered but also on from 11 to 21 weaker lines within 80 A of the strongest feature. These data do not support previous observations. The values given do not indicate a greatly reddened spectrum, and the luminescence spectrum of the mare site is not significantly different from the two young crater sites. These observations cannot be adequately explained by thermal luminescence, theories of direct excitation are also unable to explain the strength of the flux.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
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    Reduction to Outside the Atmosphere and Statistical Tests Used in Geneva Photometry (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-25
    Beschreibung: Conditions for creating a precise photometric system are investigated. The analytical and discriminatory potentials of a photometry obviously result from the localization of the passbands in the spectrum; they do, however, also depend critically on the precision attained. This precision is the result of two different types of precautions. Two procedures which contribute in an efficient manner to achieving greater precision are examined. These two methods are known as hardware related precision and software related precision.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center. Proc. of the Workshop on Improvements to Photometry; p 108-123
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    Light Scattered from Polished Optical Surfaces: Wings of the Point Spread Function (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-18
    Beschreibung: Random figure errors from the polishing process plus particles on the main mirrors in a telescope cause an extended point spread function (PSF) declining approximately as the inverse square of the sine of the angle from a star from about 100 micro-rad to a right angle. The decline in at least one case, and probably in general, proceeds as the inverse cube at smaller angles where the usual focal plane aperture radius is chosen. The photometric error due to misalignment by one Airy ring spacing with an aperture of n rings depends on the net variance in the figure. It is approximately 60/(n+1)(3) when using the data of Kormendy (1973). A typical value is 6 x 10 to the -5th power per ring of misalignment with n = 100 rings. The encircled power may be modulated on a time scale of hours by parts per thousand in a wavelength dependent manner due to relative humidity effects on mirror dust. The scattering according to an inverse power law is due to a random walk in aberration height caused by a multitude of facets and slope errors left by the polishing process. A deviation from such a law at grazing emergence may permit monitoring the dust effects.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 222-242
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    Photometry with Multi-anode Microchannel Arrays (mamas) and Charge Injection Devices (cids) (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-18
    Beschreibung: The characteristics of two kinds of detectors are summarized with emphasis on those aspects that would affect their use in high accuracy astronomical photometry. The first type, the multianode microchannel arrays (MAMA), are a family of pulse counting array detectors. Components and operation principles are reviewed and quantum efficiency, noise characteristics, and dynamic range characteristics are described. The second type, charge injection devices (CID), are discussed in reference to their applicability to photometric detection at optical wavelengths.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 203-215
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    The Use of Self-scanned Silicon Photodiode Arrays for Astronomical Spectrophotometry (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-18
    Beschreibung: The use of a Reticon self scanned silicon photodiode array for precision spectrophotometry is discussed. It is shown that internal errors are + or - 0.003 mag. Observations obtained with a photodiode array are compared with observations obtained with other types of detectors with agreement, from 3500 A to 10500 A, of 1%. The photometric properties of self scanned photodiode arrays are discussed. Potential pitfalls are given.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 182-192
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    Radio Astronomy (1983)
    In:  CASI
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    Publikationsdatum: 2014-09-12
    Beschreibung: Deep Space Network (DSN) 26- and 64-meter antenna stations were utilized in support of Radio Astronomy Experiment Selection Panel experiments. Within a time span of 10 days, in May 1983 (267.75 hours total), nine RAES experiments were supported. Most of these experiments involved multifacility interferometry using Mark 3 data recording terminals and as many as six non-DSN observatories. Investigations of black holes, quasars, galaxies, and radio sources are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: The Telecommun. and Data Acquisition Rept.; p 112-113
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    Far IR Observations of the Magellanic Clouds (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: Several Large Magellanic and Small Magellanic Cloud H II regions were observed at 50 and 100 microns. Observations were made on three flights of the Kuiper Airborne Observatory using a six channel detector system. Fully sampled maps were made simultaneously at both wavelengths. The integrated properties of the H II regions are listed and interpretations of the results regarding stellar formation are presented.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 272-276
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    Far Infrared Emission from Galaxies (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: The relationship between far infrared sources and star formation is discussed. It is argued that the relationship of star formation to compact nuclear sources and the relative importance of these fundamentally different types of activity in the most luminous galaxies is still unclear. Although there is evidence for a general correlation between far infrared emission and the amount of interstellar matter present, there are also indications of significant deviations from a simple stochastic model.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 247-254
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    High Sensitivity, High Angular Resolution Far-infrared Photometry from the KAO (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: Most of the luminosity of embedded sources is reemitted in the far-infrared continuum. Measurements in the far-infrared are essential to understand the energetics of the interstellar medium, and of star formation regions in particular. Measurements from the KAO, are made in diffraction limited beams that sample a spatial scale considerably smaller than that given by IRAS. The KAO instrument technology has matured to the point that the single scan limiting flux of IRAS at 100 micro can be reached in a diffraction limited beam in a single typical KAO observing leg. The far-infrared photometer system and selections of recent observations are presented.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 180-185
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    Multi-spectral Observations of the Star Formation: the Role of Far Infrared Photometry (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: The study and analysis of complex astrophysical process requires a multispectral approach employing many of the tools of modern astronomy. The study of the interaction of early type stars with the interstellar medium is an example of this point. Two examples of multi-spectral studies of individual objects are reviewed. The predominent theme is the combination of high resolution far infrared photometry, radio images and millimeter-wave spectroscopy with the radio sensitive to the ionization, the millimeter-wave lines showing the structure and excitation of the gas and the far infrared providing a picture of the energetics of the dust which connects the star to the interstellar medium. Multispectral observations of FIRSSE and IRAS objects are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 114-126
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    Far Infrared and Submillimeter Observations of the Giant Planets (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: Far infrared measurements of the effective temperatures of Jupiter, Saturn, Uranus and Neptune were made. The measurements presented here cover the range from 35-1000 micrometers in relatively narrow bands. The observations at lambda 350 micrometers were made at the 3m NASA Infrared Telescope Facility (IRTF) of the Mauna Kea Observatory; those at lambda 350 micrometer were made on the Kuiper Airborne Observatory (KAO). All observations of Saturn were made when the ring inclination to Earth was 1.7 deg assuring an unambiguous measurement of the flux from the disk itself. Mars was used as the calibration reference. The results represent a consistent set of calibration standards. In these measurements, it is assumed that sub b(lambda = 350 micrometers) = T sub (lambda 350 micrometers). Measurements have been made of roughly 50% of the total flux emitted by Jupiter, 65% by Saturn, and 92% by Uranus and Neptune. These measurements therefore permit a considerable reduction in the uncertainties associated with the bolometric thermal outputs of the planets. The effective temperatures (T sub e) and the ratios of emitted to absorbed solar radiation were calculated.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 81-86
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    Extreme Limb Profiles of the Sun at Far Infrared and Submillimeter Wavelengths (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: Limb intensity profiles at 30, 50, 100, and 200 microns, determined from Kuiper airborne observatory (KAO) observations of the occultation of the solar limb during the total eclipse of July 31, 1981, are presented. Significant but gradual limb brightening was found at the longer wavelengths consistent with the 6000 K temperature-plateau structure of the model chromospheres of Vernazza, Avrett, and Loeser. The 100 and 200 micrometers limbs are extended significantly further above the visible limb than the Vernazza, Avrett, and Loeser model predicts. These results show that the solar chromosphere is strongly perturbed from gravitational-hydrostatic equilibrium to heights as low as 1000 km. These profiles can serve as a powerful diagnostic for modeling the temperature and density of chromospheric structure free from the assumption of gravitational-hydrostatic equilibrium.
    Schlagwort(e): ASTRONOMY
    Materialart: Airborne Astron. Symp.; p 58-62
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    Exploration of the Solar System by Airborne Astronomy (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: The contributions of airborne astronomy to the knowledge of our solar system are reviewed, beginning in 1967 when planetary observations became a vigorous part of NASA's airborne astronomy initiatives using aircraft outfitted with 30 cm diameter telescopes for infrared observations at altitudes between 12 and 15 km. These early facilities and their successor, the Kuiper airborne observatory (KAO), profoundly influenced many areas of planetary science by providing optimized platforms for the conduct of certain types of remote sensing experiments that were incompatible with both ground-based and spacecraft environments. Specific topics reviewed include energy balance in the outer planets, the composition and structure of planetary atmospheres, and planetary ring systems.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 39-57
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    The Beginnings of Airborne Astronomy, 1920 - 1930: an Historical Narrative (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-17
    Beschreibung: The emergence of airborne astronomy in the early twentieth century is recounted. The aerial expedition to observe the solar eclipse on September 10, 1923, is described. Observation of the total solar eclipse of January 24, 1925, is discussed. The Honey Lake aerial expedition to study the solar eclipse of April 28, 1930, is also described. Four major accomplishments in airborne astronomy during the period 1920 to 1930 are listed. Airborne expeditions were undertaken at every logical opportunity, starting a continuous sequence of airborne astronomical expeditions which was to remain unbroken, except by World War II, to the present day. Although the scientific returns of the first ten years were modest, they did exist. Interest in, and support for, airborne astronomy was generated not only among astronomers but also among the public. Albert Stevens, arguably the true father of airborne astronomy, was to become interested in applying his considerable skill and experience to the airborne acquisition of astronomical data.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 9-25
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    Photodiodes for Astronomical Stellar Radiometry (1984)
    In:  CASI
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    Publikationsdatum: 2014-09-18
    Beschreibung: The theory of photodiodes and their application to radiometric measurements is reviewed. Some suggestions concerning photodiode detectors for use in stellar radiometric measurements are given. Quantum efficiency, linear response characteristics, and noise current values of silicon photodiodes are considered.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 193-202
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  • 81
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    Time Series Photometry with a CCD Camera (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Time series observations of a field in the cluster NGC 4755 with a CCD camera are used to show that differential photometry between stars on the CCD frame is limited in accuracy mostly by photon statistics, over a 5 magnitude range. Scintillation noise appears to be almost entirely suppressed. The maximum accuracy possible is limited by the storage capacity of the CCD to about 0.001 mag.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 177-181
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  • 82
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    Ccds: Their Cause and Cure (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Charge coupled devices (CCDs) have opened new horizons in the optical astronomy. Most of the presently existing astronomical CCD systems are oriented and designed primarily for work on faint objects. The use of CCDs for high precision work on bright objects remains to be explored. Issues and problems specific to (CCDs) are covered in detail. The important structural characteristics of CCDs are that they are integrating, self scanned, photon counting (one selection for each detected photon), solid state devices. The typical physical sizes are of the order of 1 - 3 cm, and typical raster formats of 500x500 pixels (TI), 320x512 (RCA), 385x576 (GEC), 800x800 (TI), and 1500x1500 (GEC) should be available soon. Typical (and optimal) operating temperatures are around -100 C, with liquid N2 as the most common coolant. Some CCDs are physically warped. This causes focus variations across the surface, which amount to a spatially variable PSF. Other relevant properties of CCDs as detectors and a comparison with some other astronomical detectors are given.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 152-176
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  • 83
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    A CCD System for Photometry of Direct and Spectroscopic Images (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: A charge-coupled device (CCD) for direct imagery at the focus of a ground-based telescope and for high dispersion spectroscopy of stars is evaluated. The CCD is an RCA SID 53612 thinned, buried channel array of 512x320 30-micron square pixels that are back-illuminated and refrigerated to about -60 C in a rugged, RF-shielded vacuum housing. The double-correlated sampling (integrator) readout system, the Z80 microprocessor readout control system, and the data collection system are described. The readout noise is 120 electron-hole pairs (ehp) per pixel per readout, the thermal dark current is 50 ehp/pixel/sec, and the scale of the 12-bit analog-to-digital converter is 25 ehp/AD unit. Unique features of this system are compared to other astronomical implementations of the same model of CCD.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 137-151
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  • 84
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    Gain Instabilities in Photomultipliers: How Accurate are Photon Counting Measurements? (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Experiments performed on five commercially available photomultiplier tubes indicate that gain instabilities can be an important source of error in photon counting measurements at the 1% level. It is shown that the error cannot be significantly reduced by standard differential measurement techniques. Analysis of time variations in the pulse height distribution is shown to be a sensitive diagnostic tool for the measurement of gain variations. Using this technique it is found that gain variations occur at counting rates as low as 100 Hz. It is argued that such errors will be present at some level in all tubes. Several calibrating schemes capable of reducing the error to below the 0.1% level are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 125-136
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  • 85
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    The Atmospheric Extinction Problem (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Atmospheric extinction, which is one of the main causes of errors in photometry is investigated. The incorrect determination of the extinction coefficient, and its variability, leads to an erroneous measurement. An erroneous extinction coefficient can arise from a number of causes including: (1) instrumental instabilities; (2) too few data points; (3) temporal changes in the atmosphere; and (4) differing airmasses due to components with different scale heights. While it is true that differential measuring techniques can achieve a precision approaching 0.1 percent, at higher levels of precision all of the above causes will be significant sources of error. The conditions that must be met in order to properly determine and correct for atmospheric extinction are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 88-107
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  • 86
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    A Statistical Evaluation of the Limitations of Single-channel Intermediate-band Photoelectric Stellar Photometry (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Error distribution in differential photometry for a moving solar system object is investigated. The results of differential photometry of several dozen pairs of planetary comparison stars observed since 1972 are reviewed. Each pair of stars was observed along with the corresponding planet or satellite, typically about ten times during the course of a single apparation lasting about four months. The comparison stars are chosen to bracket the opposition position of the planet, the expected opposition magnitude, and solar color. In practice, this means that the range of spectral type was mid-F to early K, the range of B-Y color was about 0.25 to 0.95 mag, the range of differential magnitude was less than 2 mag but most often less than 1.0 mag, and the difference in declination was typically less than 3 deg. The difference in air mass at meridian transit was usually less than 0.03, and rarely exceeded 0.01. Hence, differential extinction effects are negligible, except under extraordinary conditions.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 79-87
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  • 87
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    Atmospheric Limitations in Stellar Seismology: Should One Measure Radial Velocity or Brightness Fluctuations? (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Low degree p-modes of the Sun have been measured in spatially integrated sunlight (the Sun as a star) both in Doppler shift and in intensity fluctuations. These observations are a good starting point for the discussion of the best way to collect equivalent data on other stars. It is assumed that the Sun is removed far enough in space to become an ordinary star of magnitude zero to one. Evidently another star will oscillate with different frequencies and different amplitudes, but some reference must be made to start with. Using this scheme, a detailed investigation of the limitations of observational accuracy in the search for global p-modes is made. The sources of noise stand in the Sun itself, in the instrumentation, in the observing time duration, in the corpuscular nature of the light and mostly in the Earth atmosphere in the case of ground based observations.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 68-78
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  • 88
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    The Ground Based Photometric Limitations to the Search for Light Variations Due to 5-minute Solar-type Oscillations in Other Stars (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: High speed photometric observations obtained with a single channel photometer on the South African Astronomical Observatory 0.5-m and 1.9-m telescopes are presented. It is argued that the dominant source of noise at periods near 5 minutes is sky transparency variation rather than scintillation. For bright stars this means that, at this period, increased telescope aperture does not improve photometric accuracy. It is claimed that ground based photometric observations cannot reach accuracies sufficient to study solar-type oscillations in other stars. Such observations must be made from space. Recommendations for improving ground based observations are made.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 56-67
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  • 89
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    A Survey for Photometric Variability from Space (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: A survey for photometric variability in a wide variety of astronomical objects would produce much new information about their interiors and dynamics. Reasons for such a survey are given, as well as an example of the solar-constant variations that can be used as a guide to what may be expected from main-sequence stars. A concept for a satellite dedicated to a survey of photometric variability is proposed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 43-54
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  • 90
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    Five-minute P Modes Detected in Doppler Shift Measurement on Alpha Centauri (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: A spectrophotometer using the principle of optical resonance spectroscopy, designed for the goal of identifying radial and weakly non radial eigenmodes in the five minute range in the case of stars, is discussed. The conclusion of the first test of this new instrument was that if the observation can be photon noise limited (i.e., in total absence of any instrumental source of noise), the five-minute solar oscillation could still be detected by removing the Sun far enough for its magnitude to become zero or one. Such a situation is very closely represented by the observation of Alpha Centauri A, because it is a G2 V star, very similar to the Sun, with a mass of 1.1 in solar unit. Six nights were granted to this program on a 3.6m telescope, from 22 to 28 May 1983. Two and half nights provided over 20 hours of data of photometric quality good enough for analysis.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvement to Photometry; p 28-32
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  • 91
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    History of Photometric Precision (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: A history of photometric precision is given. The fixing of the scale of stellar magnitudes, progress toward precision and accuracy, and the use of photography are discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 8-14
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  • 92
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    High Precision Measurement of Stellar Radial Velocity Variations (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: A prototype instrument for measurement of stellar radial velocity variations to a precision of a few meters per second is discussed. The instrument will be used to study low amplitude stellar non-radial oscillations, to search for binary systems with large mass ratios, and ultimately to search for extrasolar planetary systems. The instrument uses a stable Fabry-Perot etalon, in reflection, to impose a set of fixed reference absorption lines on the stellar spectrum before it enters the coude spectrograph of the McDonald Observatory 2.7-m telescope. The spectrum is recorded on the Octicon detector, which consists of eight Reticon arrays placed end to end. Radial velocity variations of the star are detected by measuring the shift of the stellar lines with respect the artificial Fabry-Perot lines, and correcting for the known motions in the solar system.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Proc. of the Workshop on Improvements to Photometry; p 33-42
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  • 93
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    SIRTF: the Next Step (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: The space infrared telescope facility (SIRTF) is a 1-meter class, long duration, super fluid helium-cooled telescope in Earth orbit, equipped with imaging and spectroscopic instrumentation operating over the wavelength range from 1.8 to 700 microns. The SIRTF will be the most powerful tool available for studying many of the compelling problems in contemporary astrophysics and for further exploration of the infrared sky demonstrated by IRAS. Adaptation of IRAS technology (cryogenics, optics, and pointing and guidance) is discussed.
    Schlagwort(e): ASTRONOMY
    Materialart: Airborne Astron. Symp.; p 348-362
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  • 94
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    A New Generation of Sub Mm Telescopes, Made of Carbon Fiber Reinforced Plastic (1984)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-18
    Beschreibung: Carbon fiber reinforced plastic (CFRP) appears to be the material most suited for the construction of submillimeter telescopes (SMT) not only for ground-based use but also for space applications. The accuracy of the CFRP reflectors needs to be improved beyond value of the 17 micron rms envisaged for the 10 m SMT.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA. Ames Research Center Airborne Astron. Symp.; p 341-347
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  • 95
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    Upper Limits to the Annihilation Radiation Luminosity of Centaurus a (1983)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-10
    Beschreibung: A high resolution observation of the active nucleus galaxy Centaurus A (NGC 5128) was made by the GSFC low energy gamma-ray spectrometer (LEGS) during a balloon flight on 1981 November 19. The measured spectrum between 70 and 500 keV is well represented by a power law of the form 1.05 x 10 (-4) (E/100 keV) (-1.59) ph/sq cm /s with no breaks or line features observed. The 98% confidence (2 sigma) flux upper limit for a narrow ( 3 keV) 511-keV positron annihilation line is 9.9 x 10 (-4) ph/ sq cm /s. Using this upper limit, the ratio of the narrow-line annihilation radiation luminosity to the integral or = 511 keV luminosity is estimated to be 0.09 (2 sigma upper limit). This is compared with the measured value for our galactic center in the Fall of 1979 of 0.10 to 0.13, indicating a difference in he emission regions in the nuclei of the two galaxies.
    Schlagwort(e): ASTRONOMY
    Materialart: NASA(Goddard Space Flight Center Contrib. to the Workshop on Positron-Electron Pairs in Astrophys.; p 39-44
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  • 96
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    HD 207739 - A strange composite star (1983)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-18
    Beschreibung: This star, classified F8 IIe + B:, has a very unusual ultraviolet spectrum, with abnormally strong and numerous absorption features in the far-UV and exceptionally strong Mg II emission. There is some resemblance to shell and pre-main-sequence B stars, but it more closely matches the strange spectra of the eclipsing systems VV Cep and SX Cas, and it probably has considerable circumstellar material at fairly high temperature. HD 207739 is probably an interacting binary and needs to be monitored for light and velocity variations.
    Schlagwort(e): ASTRONOMY
    Materialart: Astrophysical Journal; vol. 264
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  • 97
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    Radio interferometry from space platforms (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: While current VLBI observations are limited in their resolution by the earth diameter magnitude, which is the largest antenna separation available, as well as in their information content, because of the small number of antennas in use at a given time, the extension of VLBI to include one or more antennas in space will relieve both constraints and help to map distant radio sources with the highest possible resolution. Attention is given to the implementation of such an orbital VLBI system extension through (1) a Shuttle-launch mission, (2) a six-month to one-year near earth orbit mission based on a space platform associated with the Space Station, (3) a large orbit free flyer platform mission of more than 2-year duration, and (4) lunar and/or deep space orbits, aimed at reaching the resolution limits set by interstellar scattering.
    Schlagwort(e): ASTRONOMY
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  • 98
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    AXAF - A major spaceborne X-ray observatory (1984)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Attention is given to the design configuration and performance requirements of the Advanced X-ray Astrophysics Facility, as established by Phase A study results, noting the conceptual apprach to instrument accommodation by means of a focal plane assembly. Conceptually, the various instruments incorporated are modular in design, so that they may be replaced in orbit using standard interfaces. The instruments in question are high and moderate resolution imagers, a high resolution dispersive spectrometer, a moderate resolution spectrometer, and a focal plane polarimeter.
    Schlagwort(e): ASTRONOMY
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  • 99
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    U.S. data processing for the IRAS project (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The JPL's Scientific Data Analysis System (SDAS), which will process IRAS data and produce a catalogue of perhaps a million infrared sources in the sky, as well as other information for astronomical records, is described. The purposes of SDAS are discussed, and the major SDAS processors are shown in block diagram. The catalogue processing is addressed, mentioning the basic processing steps which will be applied to raw detector data. Signal reconstruction and conversion to astrophysical units, source detection, source confirmation, data management, and survey data products are considered in detail.
    Schlagwort(e): ASTRONOMY
    Materialart: vol. 36; Jan. 198
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    Experimental test of the variability of G using Viking lander ranging data (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: Results are presented from the analysis of solar-system astrometric data, notably the range data to the Viking landers on Mars. A least-squares fit of the parameters of the solar system model to these data limits a simple time variation in the effective Newtonian gravitational constant to (2 + or - 4) x 10 to the -12th/yr and a rate of drift of atomic clocks relative to the implicit clock of relativistic dynamics to (1 + or - 8) x 10 to the -12th/yr. The error limits quoted are the result of uncertainties in the masses of the asteroids.
    Schlagwort(e): ASTRONOMY
    Materialart: Physical Review Letters (ISSN 0031-9007); 51; 1609-161
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