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  • LUNAR AND PLANETARY EXPLORATION  (1,449)
  • ASTRONOMY  (459)
  • COMMUNICATIONS AND RADAR
  • 1980-1984
  • 1975-1979  (2,311)
  • 1950-1954
  • 1977  (1,173)
  • 1976  (1,138)
Collection
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  • 1980-1984
  • 1975-1979  (2,311)
  • 1950-1954
Year
  • 1
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    Toward diffraction-limited seeing of dim astronomical objects from the Earth's surface using LIDAR (1977)
    In:  CASI
    Details
    Publication Date: 2005-02-28
    Keywords: ASTRONOMY
    Type: Res. in the Space Sci., Vol. 2, No. 1; 12 p
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  • 2
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    Infrared astronomy and high energy astrophysics (1977)
    In:  CASI
    Details
    Publication Date: 2006-08-09
    Description: Observations of the diffuse far-infrared flux from the galactic plane, as well as far-infrared measurements of the properties of dense molecular clouds, when combined with recent high-energy gamma-ray measurements and radio observations of carbon monoxide, yield information about the total mass of molecular clouds, the large-scale structure of the inner galaxy, and the density of cosmic rays.
    Keywords: ASTRONOMY
    Type: The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 203-214
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  • 3
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    A study of the cosmic sources of hard X-rays (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: An actively-shielded, high-energy X-ray telescope was launched onboard OSO-8 on 21 June 1975. The primary objectives of this experiment are the measurements of the energy spectrum of discrete cosmic X-ray sources in the range 20 keV to 3 MeV and of the temporal variations in the intensity of each source detected with a time resolution of 0.3 msec. This detector provides the highest duty factor and the finest time resolution of any of its kind for observations over a period of up to 10 days. The background spectrum of this detector in orbit was monitored continuously since shortly after launch. The minimum detectable source strength is estimated to be between 10,000 and 100,000 photons/sq-cm-sec keV, limited primary by the effects of induced radioactivity. From 16 July through 18 July 1975, the X-ray binary, Cen X-3, was observed with the hard X-ray telescope.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 739-746
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  • 4
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    Simultaneous X-ray and optical observations of X Persei (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Photoelectric photometry of X Persei was obtained on five out of seven consective nights in January 1975, from the Lick and Leuschner Observatories. The observations yield B = 6.848 + or - 0.002, B-V = 0.139 + or - 0.001, with no strong evidence for variability during the observing run. These are the faintest and bluest photoelectric magnitudes and colors ever reported for X Per; this change apparently occured relatively uniformly during 1973-74 and is reminiscent of behavior last observed in approximately 1900. The suggested association of X Persei with the weak X-ray source 3U 0352+30 raises the possibility of detection of X-ray/optical covariability. On January 21, 1975, 7 hours of data were obtained from both observatories simulataneous with OAO Copernicus X-ray observations of 3U 0352+30. The X-ray data varied during this period by a factor of two, but there is no obviously correspondent optical activity, to a level of 0.02 mag. The optical data are also used to limit to 0.01 mag variations coincident with the X-ray periodicity.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 719-726
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  • 5
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    OSO-8 GSFC results on Cen X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Spectra of Cen X-3 during eclipse, in transition out of eclipse, and during several later phases of the binary orbit were obtained from quick look data of the July 16-25, 1975 observation by the Goddard X-ray spectroscopy experiment on OSO-8. In the high state there was no absorption turn over. Pulsations were present at least to 23 keV. The spectrum at the pulse minimum was flatter above 7 keV than that of the pulse peak. In transition out of eclipse Cen X-3 emerged above a small low energy flux seen during eclipse. The observations appear to indicate absorption by cold and ionized matter and the presence of iron in the companion's atmosphere. Decreased intensities were observed at late phases of some binary orbits in some cases corresponding to dips. Absorption appears although the low energy component remains. Variable features may be interpretable as absorption and emission by iron and possibly other trace elements.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 207-218
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  • 6
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    X-ray spectroscopy with the ANS satellite (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Preliminary results from the Bragg crystal spectrometer on the ANS satellite are given. No significant Si XIII and Si XIV narrow line emission has been detected from Cygnus X-1, -2, or -3.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 49-52
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  • 7
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    OSO-8 observations of Hercules X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The X-ray binary Her X-1 was observed by the GSFC cosmic X-ray detectors aboard OSO-8 between August 26 and September 3, 1975. The results reported are based on quick look tapes which contain less than 10% of the total time spent on source. Spectra were observed during different phases of the binary period including the anomalous low state (dip) in X-ray intensity. The normal high spectra is well represented by a power law with a short cutoff above approximately 25 keV. A significant and varying enhancement in the intensity around 6.7 keV was observed, suggesting the presence of an iron line. Absorption was seen in the spectrum immediately following eclipse. The dip spectrum is found to be considerably flattened. Also spectra are presented for different phases of the pulse period.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 161-168
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  • 8
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    Some features of the X-ray source Cyg X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Data from the Copernicus satellite are presented which show that the 4.8 hour light curve of Cyg X-3 has been relatively stable in period, shape, and amplitude since the observation of the first giant radio outburst in September 1972. A pulse height spectrum of the source obtained by the Ariel 5 satellite in the 1.5 to 26 kev energy band shows convincing evidence for line emission at about 6.5 keV. The strength of this feature varies in phase with the 4.8 hour continuum modulation, but there is no simple long term relation with the mean continuum intensity per 4.8 hour cycle. Evidence is presented which indicates that the average 2-6 kev intensity of Cyg X-3 has been higher by a factor of 3 since the onset of the radio flares.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 255-265
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  • 9
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    OSO-8 observing schedule for X-ray binaries (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Six different instruments on OSO-8 have observed several binary X-ray sources between energies of 0.13 keV and 1 MeV at various times since 21 June 1975. The schedule for these observations is given, as well as the present plan for such future observations through July 1976. Included is the OSO-8 observing schedule for the transient X-ray source A0620-00.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 729-738
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  • 10
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    X-ray observation of 3U 1700-37 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: X-ray observations with Copernicus reveal three categories of flux variability in 3U 1700-37. High amplitude hourly variations are energy independent in the 3-11 keV range while a change in the low energy absorbing column causes variations in flux level on an orbital time scale. This absorption is most severe prior to eclipse ingress, suggesting that the distribution of absorbing material around the X-ray source is asymmetrical with respect to the line of centers of the binary system. The absorbing material may be identical with a high density region inferred from optical observations of HD 153919. In the third category, the maximum source intensity per binary cycle is variable by at least a factor of two between observations. Measurement of the eclipse duration on three occasions indicate that it is significantly less than when observed by Uhuru.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 559-567
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  • 11
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    A review of 3U 1700-37 = HD 153919 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: X-ray, spectroscopic, and photometric data for the source are reviewed briefly. Some points of controversy and difficulty are discussed. The X-ray source 3U 1700-37 is moderately strong (approximately 100 Uhuru counts) and shows a long eclipse, with a period of 3.412 days. The X-rays are attenuated near 0.5 phase, and show a very wide gradual decrease on either side of the total eclipse. The low-energy cutoff is the strongest of all the X-ray binaries. These characteristics are all qualitatively compatible with the optical star's, which represent an extreme in several ways: (1) the primary is an extreme star with large mass outflow through a spherically symmetric stellar wind; (2) it is the hottest of all X-ray binary primaries (with possible exception of Cen X-3); and (3) the mass ratio is very high and the relative separation of the stars is low.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 531-535
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  • 12
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    The nature of the X-ray nova A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: A model is presented for the X-ray nova A0620-00. Identification with a nova can be ruled out on two counts. A binary consisting of a late-type subgiant near the Roche lobe, irradiated by an accreting compact companion is shown, however, to be in agreement with all known observations. Photometry of the optical object should be pursued since variability on an approximately eight hour period is expected.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 361-367
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  • 13
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    New results from long-term observations of Cyg X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Cyg X-1 between October 1974 and July 1975 reveal a persistent 5.6 day modulation of the 3-6 keV X-ray intensity, having a minimum in phase with superior conjunction of the HDE 226868 binary system. The modulation is found to be most pronounced just prior to the April-May 1975 increase of Cyg X-1, after which both the modulation and intensity are at their lowest values for the entire duration of the observations. These data imply that the X-ray emission from Cyg X-1 arises from the compact member of HDE 226868, and that the increase of April-May 1975 may have represented the depletion of accreting material which had not yet been mixed into a cylindrically symmetric accretion disk about the compact member.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 391-405
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  • 14
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    The interpretation of optical light variations of Centaurus X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The interpretation of optical light variations of X-ray binaries is discussed for the case of negligible reflection effect. The limiting cases of synchronous rotation of the visible star (Roche configuration) and of no rotation (pure tidal deformation) are considered. The theoretical results are compared with the available light curves of Cen X-3. X-ray data of the Copernicus satellite are used to get an impression of the atmospheric structure of the outer layers of the visible component. It is shown, that the X-ray eclipse duration is in good agreement with the mass ration derived from the optical variations. The X-ray eclipse duration is discussed with respect to the extended low states, and a possible correlation of the extended lows with the appearance of the optical light curves is considered.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 179-185
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  • 15
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    The observation program for the GSFC cosmic X-ray spectroscopy experiment (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The cosmic X-ray spectroscopy experiment on OSO-8 will observe seven X-ray binary sources in its first six months of operation. If possible, each of these sources will be observed for one or more binary orbits so that the X-ray spectrum of each object can be observed through all phases of its orbit. For the two pulsing binaries, Her X-1 and Cen X-3, spectral variations over the pulse period will be studied. Simultaneous radio observations of Cyg X-1 and Cyg X-3 will search for any correlation between radio and X-ray emission. During the first year of operation, the detectors will observe over 50% of the known X-ray sources.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 737-738
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  • 16
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    Spectrophotometry of the unusual optical candidate for 3U 1728-24 (=GX 2+5 = GX 1+4) a recurrent nova? (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The spectrum of the object suggested as a possible optical counterpart of GX 2+5, was studied, using the image tube scanner attached to the 3-m telescope of Lick Observatory. An improved X-ray error box obtained with Copernicus strongly supports this proposed identification. The candidate displays all the characteristics of the symbiotic stars and the related recurrent novae. The spectrum reveals the presence of an M star together with a blue component and a large number of emission lines displaying a wide range of ionization. There is evidence of variability of both the continuum and the line intensities. This object provides strong support for the often proposed association of some X-ray sources with nova-like systems.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 691-701
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  • 17
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    Long term X-ray studies of Sco X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: No modulation of the 3-6 keV X-ray intensity of Sco X-1 at a level of excess of 1% is observed at the optical period of .787313d. Evidence is found for shot-noise character in a large fraction or the X-ray emission. Almost all of the Sco X-1 emission can be synthesized in terms of approximately 200 shots per day, each with a duration of approximately 1/3 day.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 703-716
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  • 18
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    The X-ray binary HD 77581 + 3U 0900-40 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The properties of the binary system in the different regions of the electromagnetic spectrum are presented from X-rays to the radio. Physical parameters and a model for the system are derived.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 575-614
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  • 19
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    The Skylab S019 ultraviolet spectra of HD 153919 (=3U 1700-37) and HDE 226868 (=Cyg X-1) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Ultraviolet spectra of HD153919 (=3U1700-37) and HDE226868 (=Cyg X-1) were obtained with the ultraviolet objective-prism spectrograph of Skylab Experiment S019. The data consist of unwidened spectra which extend to 1,600A for HD153919 and to 2,400A for HDE226868. The wavelength resolution is about 2A to 1,400A and 12A at 2,000A. For HD153919, an unwidened spectrum of fair quality and extending to a wavelength of 1,600A was obtained at 22 sup h 08 sup m on 1 September 1973. The energy distribution in this spectrum generally resembles that of other reddened O stars. A break in continuum intensity seems to occur at a wavelength of about 1,720A. There is a suggestion of an emission line on the longward edge of the break but this could be either a chance clumping of grains or else a photographic edge-effect caused by the break.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 551-553
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  • 20
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    High resolution measurements of Cyg X-1 from rockets (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Cyg X-1 was observed on two occasions (Oct. 4, 1973 and Oct. 3, 1974) by the Goddard X-ray rocket payload. This payload consisted of two gas proportional counters (xenon-methane with 710 sq cm and argon-methane with 610 sq cm using the same 128 channel pulse height analyzer and having 320 micro sec temporal resolution on the 1973 flight and 160 micro sec resolution on the 1974 flight. During both flights, bursts of 1 ms duration were observed with very high statistical certainty. To date all 13 of these bursts were analyzed for spectral and temporal character, and the results of this analysis are presented. The spectra of overall X-ray emission from both flights is also presented. In a source known for its variability, it is remarkable that the spectra taken one year apart are virtually identical.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 443-451
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  • 21
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    The early light curve of A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The Ariel-5 All-Sky Monitor measured the 3-6 keV X-ray intensity of 0620-00 for two days shortly after peak emission in August 1975, and continuously throughout September 1975. The effective exposure each day for this source (and every other source in the 80% of the celestial sphere covered by the monitor) is approximately 250 sq cm sec. The light curve obtained through October 1 (when the spin axis was again pointed to A0620-00) is shown. The intensity difference at maximum is obviously a manifestation of the very soft spectrum of the source. Clearly, A0620-00 was approximately four times as bright as Sco X-1 at maximum in the band 3-6 keV. The decay is quite smooth, but cannot be fit with a single e-folding time. The interval between the early All-Sky Monitor points and the onset of continuous coverage has an inferred e-folding time of 22 days, but it is continually increasing throughout September. A0620-00 is apparently similar in its X-ray character to the very strong, long-lasting transient X-ray sources which presently number six. In contrast, only three can be sensibly reconciled with the lower-intensity, shorter-duration hard-spectrum transients which have been found to pulse on a time scale of minutes.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 311-316
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  • 22
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    Absence of iron line emission in Cyg X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: An observation of Cygnus X-3 was made with soft X-ray detectors launched on an Aerobee rocket. The iron line emission observed one month later and in May 1975 was not found. A 3 sigma upper limit for this feature is 0.006 ph/2 cm/s.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 285-292
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  • 23
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    The radio sources associated with Cyg X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Some of the conclusions derived from the data on the radio flaring of Cyg X-3 are summarized. In addition, recent data showing that Cyg X-3 has both active and quiet radio behavior are presented.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 233-244
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  • 24
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    Recent Uhuru results on Centaurus X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The current status of the analysis of Cen X-3 data from Uhuru concerning pulsations, orbital period and eccentricity, and extended lows, are reviewed. The pulse period decreases irregularly. The pulsed fraction (2-7 keV) is 70%-90% for single pulses but significantly less for superpositions of pulses, due to variability in shape. The pulses are narrower at higher energies with a correlated increase in fraction pulsed. The orbital period is found to both decrease and increase with p/p on the order of a few times 0.00001/year. A three sigma upper limit on the eccentricity of 0.003 is obtained; if no significant periastron motion is allowed over two years, the upper limit becomes 0.0016. The orbital period is found to be detectable during some extended lows but with a significantly decreased ratio of eclipsed to non-eclipsed intensity. Two transitions between normal high states and extended lows are studied, and a consistent model is obtained in which extended lows are caused by both burying the source in an increased stellar wind from the companion, and starving the source by decreasing the stellar wind. Changes in fraction pulsed during transitions and systematic differences in the harmonic content of the pulses are also found.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 197-206
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  • 25
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    Optical observations of HDE 226868 = Cygnus X-1: A review (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The present state of knowledge of the binary system HDE226868 = Cygnus X-1 is summarized, including system dimensions, nature of the secondary X-ray source, and mass transfer properties. Some deficiencies in the optical observations are pointed out; these deficiencies make interpretation of the system difficult, but can be corrected.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 465-484
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  • 26
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    Intensity and spectral variations of Cyg X-1 observed from balloons (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Cyg X-1 with a 20 to 200 keV balloon carried X-ray telescope in 1969, 1970, and 1972 are presented. These results reveal the following characteristics of Cyg X-1: The steep spectrum observed at E 10 keV during the radio quiet phase can extend to 200 keV. This phase may have lasted 21 months (July 1969 to March 1971). The low flux values are factors of 3 and 8 below the normal values at 30 and 100 keV respectively, are rarely observed, and may be associated with the early phase of the 1971 April X-ray transition. During some one hour periods, the intensity remained constant to approximately 20% and during other periods it varied a factor 2 in 5 minutes and a factor 10 in 1 hour. Complex spectral variations accompanied the intensity changes.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 407-424
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  • 27
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    Introduction to Cyg X-1 X-ray panel (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The status of X-ray observations is summarized in tabular form along with general aspects of X-ray emission. Specific questions that arise when the observed phenomena are pieced together into a coherent picture are presented. Spectral states, transitions, periodic behavior, fluctuations, and bursts are among the topics discussed.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 369-372
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  • 28
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    The transient X-ray source A0620-00 (Nova Monocerotis 1975) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: A0620-00 is the first of the so-called X-ray novae to be identified with an optical object. Emission in the ultraviolet, infrared, and radio wavelength regions was observed from this source. From the observed properties of the optical radiation, it is suggested that the source is a recurrent nova.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 293-309
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  • 29
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    Pulsed X-ray observations of Cen X-3 from Ariel-5 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The 4.8 second X-ray pulsations from Centaurus X-3 were monitored by the MSSL collimated proportional counter on board Ariel-5 between 18-27 January 1975. Analysis of the source Doppler effect shows that the pulsation period of Cen X-3 decreased by 3.70 + or - 0.04 milliseconds during the preceding 2.3 years. The Doppler analysis also yields updated values for the binary phase and period of Cen X-3. Phase zero occurred at JD 2442438.628 + or - 0.003, and the average heliocentric binary period between October 1972 and January 1975 was 2.087129 + or - 0.000007 days. Light curves of the 4.8 second pulsations in the 3-9 keV band are characterized by two pronounced peaks, in contrast with the single peak profiles observed by Uhuru.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 219-231
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  • 30
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    The interstellar matter column density to Cen X-3 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The usual gas-to-dust ratio is shown to hold quite precisely for a sample of supernova remnants with available X-ray spectra and interstellar reddening observations. Supernova remnants are extended objects, tenuous enough to be optically thin in the X-ray range; it is shown that the X-ray observations can readily be interpreted in terms of a main source component and of an interstellar perturbation affecting the lower part of the spectrum. Cen X-3 is associated with an OB supergiant. The effect of the column density is easily detectable in the X-ray range. The spectrum exhibits a low energy cut-off, which is parameterized by a column of cold matter, NX. The cut-off is definitely observed to be variable. There is a suggestion that sometimes NX NH. It is concluded that on those occasions a spurious soft X-ray component is present in the source, bearing close similarity with Cyg X-1.
    Keywords: ASTRONOMY
    Type: X-ray Binaries; p 189-195
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    Radiation mechanisms and magnetospheric structure of pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: A model of pulsars is outlined. Key early considerations were those which led to the identification of pulsars with neutron stars, the Goldreich-Julian model of pulsar magnetospheres, and the recognition that, in a pulsar magnetosphere, a high energy gamma ray may annihilate to produce an electron-positron pair. Arguments that suggest that pulsar magnetospheres may contain large masses of plasma, a suggestion which has important implications concerning the structure of the magnetosphere, are considered along with observational data which support a magnetosphere model based on that idea rather than the Goldreich-Julian model.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 108-117
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    Galactic distribution of pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The density distributions of pulsars in luminosity, period, Z-distance, and galactocentric distance were derived using a uniform sample of pulsars detected during a 408 MHz pulsar survey at Jodrell Bank. There are indications of a fine scale structure in the spatial distribution and evidence that there is a general correlation with other galactic populations and the overall spiral structure. The electron layer in the galaxy is shown to be wider than the pulsar layer and uniform on a large scale. The number of pulsars in the galaxy was estimated and used to derive the pulsar birthrate.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 299-319
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    Gamma ray pulsars (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center The Struct. and Content of the Galaxy and Galactic Gamma Rays; p 118-127
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  • 34
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    Optical observation of WRA 977 (3U 1233-62?) (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: UBV photometry of WRA 977 on 36 nights between January and July of 1974 shows that this object is active on a time scale of days at the 0.1 mag level, but that it remains quite constant during monitoring intervals lasting up to 1 hour. Periodogram analysis reveals no significant periodic variation in the brightness of this object.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 677-682
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  • 35
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    He II lambda 4686 photometry of HD 153919 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The optical component of the binary X-ray source 3U1700-37/HD 153919 was observed with the interference filter centered on the He II lambda 4686 emission. This photometry does not reveal any dependence of lambda 4686 emission on the orbital phase thereby confirming earlier spectroscopic result that the region of formation of the ionized helium emission is confined to the envelope of the 06f primary.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 555-557
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  • 36
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    Blue band photometry of Cygnus X-1 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Results of blue band photometry of HDE 226868 in the years 1972-3-4 and provisional results for 1975 are presented. A mean light curve is obtained from the first three years observations which is based on 192 nights observations. Intercomparison of the results from the different years shows that the light curve is not constant.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 521-527
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  • 37
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    A0620-00 as a recurrent nova (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Evidence for and against the star associated with A0620-00 being a nova is presented. The conclusion is that this star closely resembles other recurrent novae with the only unusual characteristic being the apparent high temperature at maximum brightness.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 335-341
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  • 38
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    Optical identification of A0620-00 (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Identification of the optical counterpart to the transient X-ray source A0620-00 was made using image tube photography. Spectra taken subsequent to the identification showed no stellar absorption or emission features. Photometric data gave a V magnitude of 11.2 + or - .1. This is about 8 magnitudes brighter than the object appears on the Palomar Sky Survey.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 327-333
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  • 39
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    Observations of Cygnus X-3 by ANS (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The hard X-ray experiment (1 - 28 keV) on ANS observed Cygnus X-3 in November 1974, and in May 1975. The average flux intensities for these time periods were found to be 22.4 + or - 0.5 cts/sec and 12.8 + or - 0.3 cts/sec (1.3 - 7.1 keV), the former being the highest average value ever observed. The spectrum studies show an excess in the flux above the fitted continuum which can be interpreted as a line emission of FeXXIV and/or FeXXV, at approximately 6.5 keV. The strength of this feature varied in phase with the 4.8 hr X-ray modulation, and remained at a constant relative intensity. The period of the X-ray modulation is refined to 0.1996813 + or - 0.0000006 day and obtained at a 2 sigma upper limit to a continuous change in the period of 50 to the minus 13th power/sec. This new limit places serious constraints on several models for this object.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 267-275
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  • 40
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    Copernicus observations of a number of galactic X-ray sources (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: The Copernicus satellite was launched on 21 August 1972. The main experiment on board is the University of Princeton UV telescope. In addition a cosmic X-ray package of somewhat modest aperture was provided by the Mullard Space Science Laboratory (MSSL) of University College London. Following a brief description of the instrument, a list of galactic sources observed during the year is presented. Although the X-ray detection aperture is small, the ability to point the satellite for long periods of time with high accuracy makes Copernicus an ideal vehicle for the study of variable sources.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 1-25
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  • 41
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    Centaurus X-3: The observational picture (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Observations of Centaurus X-3 are briefly reviewed. The composition of the neutron star, optical light curves, and X-ray pulsations are among the topics discussed.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 173-176
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  • 42
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    Periodic flickering in the optical spectrum of HZ Herculis (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: Photometric observations of HZ Herculis in the ultraviolet with a time resolution of 5 seconds are discussed. The existence of periodic flickering with a time scale of 115 to 130 seconds is observed. The amplitude modulation is about 3 to 6 percent, larger than that associated with the erratic white flickering. The flickering, either erratic or periodic, occurs, but not always, near orbital phase 0.5, irrespective of the on and off parts of the X-ray cycle.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 101-111
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  • 43
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    ANS results on X-ray binaries (1976)
    In:  CASI
    Details
    Publication Date: 2006-04-18
    Description: A short description is given of the Astronomical Netherlands Satellite (ANS) and the X-ray instruments of the Space Research Laboratory in Utrecht. The ANS observed in February 1975 a soft (1/4 keV) X-ray flux in Her X-1 during the 'off'-state with an intensity of a factor 10 lower than observed in the 'on'-state. The ANS observations on Cyg X-1 are summarized. During the May 1975 flaring state a very high intensity at 0.5 keV is measured consistent with a power-law photon-spectrum with index 3.5 and an interstellar absorption of 7.10 to the 21st power atoms/sq cm, but not consistent with spectra that show an additional cut-off below 1 KeV and an absorption of 7.10 to the 21st power atoms/sq cm. Intensity changes on a time scale of minutes, as observed in Cyg X-1 low state, are not observed during the flaring state.
    Keywords: ASTRONOMY
    Type: NASA. Goddard Space Flight Center X-ray Binaries; p 27-47
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    The NASA-NMSU automated meteor observatory (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A new observatory for meteor research which provides data for study of meteor heights, velocities, orbits, and meteoroid abundances is described. The observing equipment is automated to take advantage of the long periods of favorable observing weather common to the region. Four K-24 cameras, electrically operated, provide the triangulation observations, and four Maksutov f/1.3 cameras with blazed transmission grating provide spectral coverage. The patrol cameras have operated for a year and a half, and approximately 6,000 frames have been exposed by 9 March 1975. Meteor trails appear on 260 of these frames. Sixty-eight trails are of meteors photographed from two locations and thus allow trajectory and orbit determinations for 34 meteors. Photoelectric sensors initiate the 2-second spectrograph exposures, and electrical controls open and close the observatory at present times.
    Keywords: ASTRONOMY
    Type: N. Mex. State Univ. Contrib. of the Observatory of N. Mex. State Univ., Vol 1, No. 4; p 166-173
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  • 45
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    Photometry of R Coronae Borealis (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Visual and photoelectric observations of R Coronae Borealis are presented, including a number of observations surrounding the 1974 minimum. The recent visual history of the variable is examined and the discrete cloud obscuration model is considered.
    Keywords: ASTRONOMY
    Type: Contrib. of the Observatory of N. Mex. State Univ., Vol. 1, No. 4; p 134-139
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  • 46
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    Intermediate-band photometry of faint standard stars (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The David Dunlap Observatory system uses six intermediate-band filters whose central wavelengths were chosen to cover important features in the spectrum of a late-type star. Calibrations of the color indices with physical parameters, allow one to estimate T sub eff, log g, Fe/H, M sub v and reddening directly from the photometry. Although a number of standards lists exist, only a small fraction of the stars is fainter than V=6. It is desirable to add to the numbers of faint standards. Results are presented of photometry of sixteen stars obtained during a program of variable-star photometry at Blue Mesa Observatory.
    Keywords: ASTRONOMY
    Type: Contrib. of the Observatory of N. Mex. State Univ., Vol. 1, No. 4; p 140-142
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  • 47
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    The mass of Phobos (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Radio tracking data associated with the February 1977 encounters between the Martian satellite Phobos and the Viking Orbiter I spacecraft have been analyzed to determine the gravitational constant of Phobos. A linear error analysis was conducted to determine the selection of data and the parameter solution set which would yield the best estimate of the gravitational constant. This error analysis indicated that the optimal data set was a data arc beginning just prior to the closest encounter and spanning three consecutive spacecraft orbits; data near periapsis were deleted. The most feasible parameter solution set consisted of the Phobos gravitational constant and the spacecraft initial conditions. The result of the data analysis was an estimate of (7.3 plus or minus 0.7) x 10 to the -4th cu km/sq sec for the gravitational constant of Phobos.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 4; Dec. 197
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  • 48
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    Stabilization of Kepler's problem (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A regularization of Kepler's problem due to Moser (1970) is used to stabilize the equations of motion. In other words, a particular solution of Kepler's problem is imbedded in a Liapunov stable system. Perturbations can be introduced into the stabilized equations.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 16; Sept
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  • 49
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    Spectrophotometric and color estimates of the Viking lander sites (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The spectral radiance and color of the Martian sky and soil and the spectral reflectance of soil features are estimated from six-channel (0.4-1.0 micron) spectral data obtained with the Viking lander cameras. Images taken near local noon from the two landers reveal a sky that is brighter near the horizon than the soil but with a similar spectral radiance shape and color. The scenes are predominantly moderate yellowish brown in color with only subtle variations except for some dark grey rocks. Most spectral reflectance estimates are similar: they rise rapidly with increasing wavelength between 0.4 and 0.8 micron and with only a few exceptions exhibit a pronounced minimum centered about 0.93 micron. These characteristics are consistent with an abundance of Fe(3+)-rich weathering products, notably nontronite. However, the delineation of the number and abundances of total mineral phases requires further analyses and laboratory comparisons. Reflectance estimates for rocks have not been repeatable, probably because most rocks have irregular pitted surfaces that introduce significant shadowing components.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Sept. 30
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    A search for ultraviolet OH emission from meteors (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of hydroxyl (OH) emission from meteors were made during the late summers of 1975 and 1976 from altitudes of 10,600 and 14,200 feet (3.2 km and 4.45 km). The observations were made with OH meteor photometers developed at the NASA-Langley Research Center. Two of the meteors were Perseids, and one was an Alpha Capricornid. The Perseid meteors produced a peak irradiance at a distance of 100 km from the meteors of about 0.00005 erg/sq cm per sec in the OH emission region. The zero-magnitude Alpha Capricornid meteor produced a spectral irradiance at 3100 A of 23 hundred-millionths erg/sq cm per A per sec. This may be indicative of significant amounts of H2O in these meteors.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 217
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  • 51
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    Aperture averaging effects in stellar scintillation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Stellar scintillation has been measured for apertures as low as 0.012 m by using photoncounting techniques. The scintillation measurements have been made for various aperture sizes in quick succession in order to determine experimentally the effects of aperture averaging. The results of the experiment are compared with the predictions of a model proposed earlier in the literature to quantify the phenomenon.
    Keywords: ASTRONOMY
    Type: Optics Communications; 22; Sept
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    Reducing greenhouses and the temperature history of earth and Mars (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It has been suggested that NH3 and other reducing gases were present in the earth's primitive atmosphere, enhancing the global greenhouse effect; data obtained through isotopic archeothermometry support this hypothesis. Computations have been applied to the evolution of surface temperatures on Mars, considering various bolometric albedos and compositions. The results are of interest in the study of Martian sinuous channels which may have been created by aqueous fluvial errosion, and imply that clement conditions may have previously occurred on Mars, and may occur in the future.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 269; Sept. 15
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    Happy Canyon - A new type of enstatite achondrite (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Mineralogical and chemical characteristics of the Happy Canyon meteorite, found in 1971 near Wayside, Texas, show it to be a new type of enstatite achondrite occupying the gap between the recrystallized enstatite chondrites and the igneous, crystalline, unbrecciated enstatite chondrites. Although the bulk composition of the specimen is consistent with that of an E6 enstatite chondrite, it has a crystal cumulate texture. There are minor amounts of metal and troilite which have survived extensive weathering. The Happy Canyon meteorite may represent an E6 composition which has melted and reprecipitated at a slightly higher oxidation state, possibly in the core of a small parent body.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 12; June 30
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    The upper ionosphere of Titan (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photoionization of the upper atmosphere of Titan by sunlight is expected to produce a substantial ionospheric layer. One-dimensional forms of the mass, momentum, and energy conservation equations for ions and electrons have been solved along with electron number densities of about 1000/cu cm, using various model atmospheres. The significant ions in a CH4-H2 atmosphere are H(+), H3(+), CH5(+), CH3(+), and C2H5(+). Electron temperatures may be as high as 1000 K, depending on the abundance of hydrogen in the high atmosphere. Interaction of the solar wind with the ionosphere is also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 31; May 1977
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  • 55
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    Far-infrared scans of the Galactic plane (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for balloon-borne scans of the Galactic plane between longitudes of 348 and 32.5 deg, which were made in two broad spectral bands from 60 to 300 microns and from 150 to 300 microns. These results indicate that there are many bright H II regions embedded in a diffuse underlying band of emission in the examined longitude range, that the color temperatures range from 30 to 90 K, and that the width of the plane is at least 2 deg of arc in both spectral bands. A lower-limit IR luminosity of the order of 1 billion suns is computed for both the bright complex of sources at the nucleus and the underlying diffuse emission out to about + or -15 deg of arc from the nucleus. The strong relationship between far-IR emission and radio continuum expected for discrete sources is illustrated, and the results are compared with those of previous studies. It is concluded that the total far-IR luminosity of the central part of the Galaxy is understandable solely in terms of known distributions of stars and dust.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 214
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  • 56
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    The rings of Uranus (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A description is given of the observation of five brief occultations of the star SAO 158687 which occurred both before and after its occultation by Uranus on March 10, 1977. The events were observed with a three-channel occultation photometer, attached to a 91-cm telescope. The observations indicate that at least five rings encircle the planet Uranus. Possible reasons for the narrowness of the Uranus rings are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 267; May 26
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    Observations at the planet Mercury by the plasma electron experiment - Mariner 10 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Two nightside encounters with Mercury's magnetosphere by Mariner 10 revealed bow shock and magnetosheath signatures in the plasma electron data that are entirely consistent with the geometry expected for an interaction between a planet-centered magnetic dipole and the solar wind. The geometrically determined distance between the planet's center and the solar wind stagnation point is 1.4 plus or minus 0.1 R sub M. Both diffuse and sharp shock crossings were observed on the two magnetosphere encounters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; May 1
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  • 58
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    A radio lens in the ionosphere (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Using a modified version of the classical Cornu spiral, fading patterns in agreement with observations of radio signals on 140 and 360 MHz from the geostationary satellite ATS6, have been obtained. The particular fading patterns chosen show modulated quasi-periodic fading before and after a deep central minimum. It is shown that a cylindrical lens in the ionosphere required to produce this is only about 100 m across (an order of magnitude smaller than the size of the pattern on the ground) and if it were circular in cross-section would have a maximum plasma frequency of over 40 MHz. This suggests the reason why calculations based on a transparent phase screen did not give the observed fading pattern for 40 MHz signals. It was not possible to deduce the height of the lens above the ground, though we would incline to an E-region origin.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Mar. 197
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  • 59
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    90-GHz flux-density measurements of variable radio sources (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are presented for measurements of the flux densities of 10 variable extragalactic sources at 85.2 or 90 GHz, which were made over a period of almost seven years with the NRAO 36-ft millimeter-wave antenna. The primary flux-density calibration standards used include Jupiter, Saturn, Mars, and the small-diameter Galactic source DR 21. Measured flux densities are given as a function of time (in years) for the sources 3C 84, NRAO 150, 3C 120, OJ 287, 4C 39.25, 3C 273, 3C 279, 3C 345, BL Lac, and 3C 454.3. No statistically meaningful flux-density changes during an observing interval (1 to 3 days) are detected for any source, and a high degree of correlation between flux-density variations at 85.2 or 90 GHz and those observed at lower frequencies is found in all 10 sources. Some variations observed at different frequencies in several individual sources are briefly discussed.
    Keywords: ASTRONOMY
    Type: Astronomical Journal; 82; Apr. 197
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  • 60
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    Linearization of dynamical systems using integrals of the motion (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A method is presented which transforms certain nonlinear differential equations of dynamics into linear equations by introducing an independent variable and utilizing the integrals of motion. As examples of special interest, the linearizations of unperturbed and perturbed Keplerian motions are discussed.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 14; Dec. 197
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    On the stability of the solutions of the general problem of three bodies (1976)
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    Publication Date: 2011-08-17
    Description: The extent through which the initial conditions of a given three-body system may be varied without completely changing the qualitative nature of the subsequent system evolution is investigated. It is assumed that the three masses are equal, all initial velocities are zero, the first two bodies initially lie on the x-axis, and the position of the third body is confined to a specific region of space. Analysis of the system evolution for different initial positions of the third body shows that there is a whole area or 'island' in the x-y plane throughout which the initial position of the third body may be moved in a continuous fashion to produce an evolution which also changes in a continuous manner. A Monte Carlo approach is adopted to determine the full extent of this island in the general problem. It is concluded that the stability of a full solution may be directly related to the size of its island in phase space.
    Keywords: ASTRONOMY
    Type: Celestial Mechanics; 14; Dec. 197
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    Minor planets and related objects. XXII - Phase functions for /6/ Hebe (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Twenty-two light curves of Hebe are analyzed along with results of UBV photometry and photometric astrometry. A mean synodic period of approximately 7 hr 16 min 28.7 sec is adopted, and it is found that the amplitude of Hebe appears to vary directly with phase. The asteroid's magnitudes and colors are plotted against phase, its pole orientation is estimated, and the sidereal period is determined to be about 7 hr 16 min 28.01 sec from photometric astrometry. A color curve is plotted which shows that Hebe has a reddened region on its surface near the secondary minimum and that the asteroid is nearly spherical. Opposition effects are compared and found to be closely similar for Hebe, Ceres, Lydia, Massalia, and Vesta.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal; 82; Mar. 197
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  • 63
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    Limitations on oceanographic use of beam-limited target-referenced radars (1977)
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    Publication Date: 2011-08-17
    Description: A general development is undertaken to determine the limitations on the use of beam-limited target-referenced radars in the measurement of ocean wave height. This class of radars is concerned only with the range extent of the target, not the range to the target. The nonzero range extent of a flat waveless sea and the compounding effect of pointing errors due to radar platform instability cause difficulty in measuring low wave heights and impose a maximum operating altitude on such systems. It is seen that it is impractical to obtain accurate measurements for wave heights of interest at altitudes above those used by commercial aircraft (10,000 m). Additionally, the typical ratio of dominant wavelength to significant wave height (SWH) of 30 for wind-driven gravity waves imposes an upper limit on the SWH measurable for a given altitude and beamwidth.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; May 1977
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  • 64
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    The Del Rio ataxite, Texas (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Basic data are presented on the Del Rio, Nordheim, and Monahans ataxites found in Texas. Results are reported for bulk-chemistry analysis, metallographic observations, and electron-microprobe analysis of the Del Rio meteorite. It is shown that Del Rio is distinctly different from the other two ataxites in terms of nickel, phosphorous, and carbon content, and is composed of at least three coarse grains in different crystallographic orientations. All the kamacite in Del Rio is found to have transformation structures that are probable shock products, and minor inclusions of daubreelite, schreibersite, and troilite are observed. It is concluded that Del Rio was apparently mildly shocked prior to its fall.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 12; Mar. 31
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  • 65
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    Tracking performance of symbol synchronizers for Manchester coded data (1977)
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    Publication Date: 2011-08-17
    Description: The implementation and tracking performance of symbol synchronizers for Manchester coded data is presented with motivation provided by maximum a posteriori (MAP) estimation theory. Certain physically relizable closed-loop structures, readily implemented in practice, are suggested by the theory for uncoded data symbols with arbitrary data transition probabilities. The tracking performance of these loops is optimized and comparisons are made among the various configurations over a wide range of system parameters. Although not the major intent of the paper, the acquisition problem is briefly addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Apr. 197
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  • 66
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    Wind enhanced planetary escape - Collisional modifications (1977)
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    Publication Date: 2011-08-17
    Description: Effects of collisions and finite winds characteristic of a highly perturbed atmosphere on the thermal escape of terrestrial hydrogen and helium are investigated using a Monte Carlo approach. The limiting cases of vertical and horizontal winds are considered, and the relaxation layer between the collisionless exosphere and the collision-dominated thermosphere is modeled as a plane-parallel slab of given column density, depth, and atmospheric density. For both gases, the upwardly injected flux at the base of the relaxation layer is compared with the returning downward flux distribution at the same location; the technique is also applied to the atmosphere of Titan. The results show that inclusion of collisions in the escape model for terrestrial hydrogen with winds effectively throttles the escape process, that collisional throttling is negligible for helium when the exobase temperature is at least 5000 K, and that the escape of a planetary-atmosphere constituent depends on the ratio of its gravitational and kinetic energies as well as on the ratio of its mass to that of the background gas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 67
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    A low-frequency radio survey of the planets with RAE 2 (1977)
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    Publication Date: 2011-08-17
    Description: Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer 2 (RAE 2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025-13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 68
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    Exploration of the giant planets by infrared spectroscopy (1976)
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    Publication Date: 2011-08-17
    Description: The infrared spectrometer and radiometer for the Mariner-Jupiter-Saturn mission is described. Results of Nimbus and Mariner 9 IR spectroscopy of earth and Mars are used as examples to demonstrate the power and diversity of the technique. Determinations of planetary surface compositions, surface temperatures, vertical temperature profiles, surface pressures, and atmospheric constituents are summarized. Applications to Jupiter and Saturn are briefly mentioned.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 69
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    Copernicus observations of the Ap star Epsilon Ursae Majoris (1977)
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    Publication Date: 2011-08-17
    Description: Spectral scans of the Ap star Epsilon UMa made with the Copernicus satellite show strong line blanketing from profuse Cr II and Fe II lines. In the spectral region covering 1900 to 3000 A, about 500 lines are present which suppress the apparent continuum by at least 15-30%. An accurate line-identification list is compiled showing Eu II present in addition to Mn II and Ni II. The identification of Eu II, however, rests on very stringent identification limits for Fe II. If these are relaxed, the existence of Eu II is dubious. There are no broad features in this spectral region which would suggest strong photoionization discontinuities by metals, but one feature near 2137 A might contain the photoionization edge due to Cr I 5S lying 0.94 eV above the ground level. However, a significant correlation between the line-blanketing strength and the amplitude of the OAO-2 ultraviolet light curves was found such that both monotonically increase in the same proportion toward shorter wavelengths. This gives additional strength to the suggestion that variations in the metal line-blanketing cause the observed photometric variations.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal Supplement Series; 33; Jan. 197
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  • 70
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    An antenna for limited scan in one plane - Design criteria and numerical simulation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Aperture illumination is synthesized through the use of overlapping subarrays with independently controlled excitations. Detailed analysis and design criteria are provided for a specific limited-scan antenna configuration scanning in one plane. The number of phase shifts is the theoretical minimum corresponding to specified aperture size and field of view. Beam pointing and width are approximately constant for moderate frequency variation, and ultralow sidelobes outside the field of view can be produced at the cost of a slight loss of illumination efficiency. Accurate aperture illumination control makes for excellent independently specified sum and difference patterns in beamforming.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Mar. 197
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  • 71
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    Lunar soil - Iron and titanium bands in the glass fraction (1977)
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 195; Mar. 11
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  • 72
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    5 GHz observations of galactic supernova remnants (1977)
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    Publication Date: 2011-08-17
    Description: Brightness and polarization distributions over several galactic supernova remnants have been observed at a wavelength of 6 cm. These observations have confirmed the nonthermal nature of most of the observed sources. It is suggested, however, that the objects G33.1-0.1 (KES 78), G35.6-0.0, G37.6-0.1, G37.7+0.1, and G37.9-0.4 are thermal. The results of these observations are presented in the form of total intensity contour maps with superimposed polarization vectors.
    Keywords: ASTRONOMY
    Type: Astronomy and Astrophysics; 55; 1, Fe; Feb. 197
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  • 73
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    Far-ultraviolet imagery of the Barnard Loop Nebula (1977)
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    Publication Date: 2011-08-17
    Description: An electrographic Schmidt camera carried on a sounding rocket has yielded far-ultraviolet (1050-2000 A and 1230-2000 A) images of the Barnard Loop Nebula and of the general background in the Orion region due to scattering of ultraviolet starlight by interstellar dust particles. The total intensity in the Barnard Loop region agrees well with OAO-2 measurements, but the discrete Loop structure contributes only some 15% of the total. The measurements are consistent with a relatively high albedo for the dust grains in the far-ultraviolet.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 212
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  • 74
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    On the reality of the Venus winds (1977)
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    Publication Date: 2011-08-17
    Description: The article presents a rebuttal of Young's (1975) view that the 140 m/sec horizontal wind at 45 km reported by Venera 8 is anomalous or spurious. Some errors are discussed and the largest contribution is attributed to descent probe measurements designed to find the true probe descent rate. Young's suggestion of error in in situ measurement of winds due to selection of a reference speed and to unrecognized oscillator drift is scrutinized. Evidence is seen for a wide band of variable high-grade retrograde horizontal winds girdling Venus at the equator. Mariner 10 evidence (UV photographs) is taken into account. The band of winds at 45 km is seen to extend well beyond the top of the visible cloud, and an upper turbulent region is attributed to vertical convection currents carried along by high-speed horizontal winds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 30; Feb. 197
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  • 75
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    Optimum performance of suppressed carrier receivers with Costas loop tracking (1977)
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    Publication Date: 2011-08-17
    Description: The performance of suppressed carrier receivers with Costas loop tracking is optimized by proper choice of loop arm filter bandwidth. In particular, it is shown that for a variety of passive arm filter types, there exists, for a given data rate and data signal-to-noise ratio, an optimum filter bandwidth in the sense of minimizing the loop's squaring loss. For the linear theory case, this is equivalent to minimizing the loop's tracking jitter. When symbol synchronization is known, it is shown that by replacing the passive arm filters with active filters, i.e., integrate-and-dump circuits, one can achieve an improvement in carrier-to-noise ratio of as much as 4 to 6 dB depending on the passive arm filter type used for comparison and the value of data signal-to-noise ratio.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Feb. 197
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  • 76
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    Apollo-16 far-ultraviolet spectra in the Large Magellanic Cloud (1977)
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    Publication Date: 2011-08-17
    Description: Spectra in the wavelength ranges from 900 to 1600 A and 1050 to 1600 A of some OB associations in the Large Magellanic Cloud were obtained from the lunar surface by the Apollo-16 far-ultraviolet camera/spectrograph on April 22, 1972. The observed spectral distributions appear consistent with a stellar model having an effective temperature of 30,000 K, reddened by E(B-V) = 0.3, and characterized by the average far-ultraviolet extinction curve of Bless and Savage (1972). However, the absolute intensity of the far-ultraviolet spectrum of the associations NGC 2050 and 2055 seems somewhat too bright in comparison with ground-based photometry.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 211
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  • 77
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    Far infrared observations of IRC + 10216 (1977)
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    Publication Date: 2011-08-17
    Description: Results are reported for measurements of IRC + 10216 at 100 microns made with the 91-cm telescope of NASA's Kuiper Airborne Infrared Observatory. The IR photometer employed consisted of a gallium-doped germanium photoconductive detector with a MOSFET preamplifier and load resistor. Signals obtained from the source at modulation frequencies of 30 and 100 Hz are plotted, and the 100-micron flux measurements are shown to be in agreement with previous bolometric measurements. It is noted that the sensitivity of the photoconductive detection system is comparable to that of the conventional bolometers that have been used in airborne IR observations.
    Keywords: ASTRONOMY
    Type: Nature; 265; Feb. 10
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  • 78
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    The elimination of short and intermediate period terms from the problem of a high altitude earth satellite (1976)
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    Publication Date: 2011-08-17
    Description: The Delaunay-Similar elements of Scheifele (1976) are applied to the problem of an earth satellite that is perturbed by the sun, moon, and J2. All three effects are assumed to be the same order of magnitude. Since the external body terms depend explicitly on time, the time element appears as an additional angle variable. Also, the eccentric anomaly is used as a noncanonical auxiliary variable. A solution to the first Von Zeipel equation allows simultaneous elimination of short- and intermediate-period terms. The canonical transformation to mean elements is defined by a generating function that is a series involving Bessel coefficients.
    Keywords: ASTRONOMY
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  • 79
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    Structure of Mars' atmosphere up to 100 kilometers from the entry measurements of Viking 2 (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Viking 2 entry data on the structure of Mars' atmosphere up to 100 kilometers define a morning atmosphere with an isothermal region near the surface; a surface pressure 10% greater than that recorded simultaneously at the Viking 1 site; and a thermal structure to 100 kilometers at least qualitatively consistent with pre-Viking modeling of thermal tides. The temperature profile exhibits waves whose amplitude grows with altitude, to about 25 K at 90 kilometers. The atmosphere is stable against convection, except possibly in some very local regions. Temperature is everywhere appreciably above the carbon dioxide condensation boundary at both landing sites, precluding the occurrence of carbon dioxide hazes in northern summer at latitudes to at least 50 deg N. Thus, ground-level mists seen in these latitudes would appear to be condensed water vapor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Dec. 17
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  • 80
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    Scientific results of the Viking missions (1976)
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    Publication Date: 2011-08-17
    Description: The two Viking missions to Mars have been extraordinarily successful. Thirteen scientific investigations yielded information about the atmosphere and surface. Two orbiters and landers operating for several months photographed the surface extensively from 1500 kilometers and directly on the surface. Measurements were made of the atmospheric composition, the surface elemental abundance, the atmospheric water vapor, temperature of the surface, and meteorological conditions; direct tests were made for organic material and living organisms. The question of life on Mars remains unanswered. The Viking spacecraft are designed to continue the investigations for at least one Mars year.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Dec. 17
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  • 81
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    Comet West and the scattering function of cometary dust (1976)
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    Publication Date: 2011-08-17
    Description: Observations of Comet West (1975n) at wavelengths from 0.5 to 18 microns and at a variety of scattering angles are used to infer the scattering phase function for the cometary dust. This function is strongly peaked in the forward direction. The form of the function indicates that the particles are dielectric grains with radii of approximately 1 micron. Abrupt increases in the intrinsic brightness of the coma (both in scattered sunlight and in thermal emission) are consistent with the projected times of comet fragmentation.
    Keywords: ASTRONOMY
    Type: Science; 194; Dec. 3
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  • 82
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    Estimated grain saltation in a Martian atmosphere (1976)
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    Publication Date: 2011-08-17
    Description: Mariner 9 spacecraft images showing evidence of variable surface features and surface erosion resulting from atmospheric wind on Mars have caused a renewed interest in the eolian mechanics of saltating grains. To study this phenomenon, both experimental investigation in an atmospheric wind tunnel and numerical solutions of the equations of motion of a single grain under Martian surface conditions were conducted. The numerical solutions for earth were used and empirically adjusted to correlate with existing experimental data for Mars. These modified equations were then solved to estimate grain motion for Mars. These calculations show the importance of a lifting force on the grain to initiate motion in both earth and Mars calculations. Major findings include a comparison of earth and Mars grain trajectories that show Mars length scales to be longer and to fall with a higher terminal grain velocity. The grains in the Mars calculation also made a smaller collision angle with the surface on rebound.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 81; Nov. 10
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  • 83
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    Al-26 in Kenna and other ureilites (1976)
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    Publication Date: 2011-08-17
    Description: A description is presented of the results of a nondestructive analysis conducted with a 42-g slice of the Kenna ureilite. The sample was analyzed in a gamma-gamma coincidence counting system, using a dual-parameter, 4096-channel pulse height analyzer. Data concerning Al-26 and Ne-22/Ne-21 in ureilites and Chassigny are presented in a table. A graph shows the ratio of measured Al-26 activity to that calculated from elemental production rates vs spallation Ne-22/Ne-21 for ureilites and Chassigny. The significance of the data with respect to findings reported by Wilkening et al. (1973) is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 40; Dec. 197
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  • 84
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    Interference in astronomical speckle patterns (1976)
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    Publication Date: 2011-08-17
    Description: Astronomical speckle patterns are examined in an atmospheric-optics context in order to determine what kind of image quality is to be expected from several different imaging techniques. The model used to describe the instantaneous complex field distribution across the pupil of a large telescope regards the pupil as a deep phase grating with a periodicity given by the size of the cell of uniform phase or the refractive index structure function. This model is used along with an empirical formula derived purely from the physical appearance of the speckle patterns to discuss the orders of interference in astronomical speckle patterns.
    Keywords: ASTRONOMY
    Type: Optical Society of America; vol. 66
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    On the energy deposition of photoelectrons in the atmosphere of Venus (1976)
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    Publication Date: 2011-08-17
    Description: Vertical components of photoelectron fluxes in the atmosphere of Venus are computed by solving an appropriate form of the Boltzmann equation in the cases where there is no flux of either photoelectrons or solar-wind particles across the ionopause and where photoelectrons are free to escape from the atmosphere. It is assumed that Venus has no magnetic field and that the atmosphere is composed of carbon dioxide, atomic oxygen, and helium. The results are plotted as a function of altitude for several energies in the range from 100 eV to a cutoff of the order of 1 eV. Heating rates for the two upper boundary conditions and the case of no spatial transport are determined which show that transport effects dominate at altitudes greater than about 200 km. Electron temperatures are calculated for the adopted model atmosphere and ionosphere by solving the pertinent conservation equation, and excitation rates are computed for the CO Cameron band as well as the CO2(+) A and B bands.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 81; Oct. 1
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  • 86
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    The 'soil' of Mars /Viking 1/ (1976)
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    Publication Date: 2011-08-16
    Description: The immediate environs of the Viking 1 lander are described, and the techniques employed to deduce the properties of the two different 'soil' types there are summarized. It is shown that the surface in the immediate vicinity of the lander consists of an area with fine-grained materials ('Sandy Flats') and a rocky area set in a matrix of finer-grained material ('Rocky Flats'). Estimates are given for the bulk density, particle density, particle size distribution, cohesion, angle of internal friction, and penetration resistance of the surface layer in each area. Footpad penetration into the surface layer is discussed, and wind removal of particles is examined. It is concluded that the surface layer of the Viking 1 landing site contains loess, dune sand, lunar nominal soil, lag gravel, and bare rock.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Oct. 1
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  • 87
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    Status of the Viking missions (1976)
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    Publication Date: 2011-08-16
    Description: A chronology of Viking 1 lander activities is presented for the first 43 sols (Martian days) of surface sampling and analysis. The orbital insertion of the second Viking spacecraft is reviewed along with the search for the second landing site. A general assessment of the planet is made on the basis of the data thus far obtained. Some of the findings reported are that: (1) there is extensive evidence of volcanism, fluvial and aeolian erosion, and deposition over the entire surface; (2) the floor of Vallis Marineris is significantly younger than the planet's surface; (3) the morphology of Martian crater ejecta is indicative of surface flow rather than ballistic deposition; (4) the rocks in the immediate vicinity of the lander are all covered by a layer of fine red dust; (5) the atmosphere is optically thick and well mixed, with suspended particles giving the sky a pink color; (6) the N and Ar isotopic ratios are different from those on earth; (7) atmospheric water vapor varies with both time of day and location; (8) the summer northern polar regions have a high water concentration in the atmosphere; (9) a large fraction of magnetic material resides in the surface; and (10) no complex organic compounds have been detected in the two samples analyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Oct. 1
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  • 88
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    Venus' night side ionosphere - Its origin and maintenance (1976)
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    Publication Date: 2011-08-16
    Description: A substantial nightside ionosphere has been observed on Venus by both Mariner 5 and Mariner 10. Major dayside ionic species such as O2(+) and other molecular ions have chemical lifetimes much shorter than the 244.3-day rotation period of the planet. Rapid transport of ions from the dayside to the nightside to the extent required seems most unlikely. Consequently, possibilities are investigated for local production of ions on the nightside itself. Constraints imposed by chemical lifetimes require atomic ions with low ionization potentials. It is suggested that metallic ions of meteoric origin are the positive charge carriers, and the plausibility of this mechanism is demonstrated. Other possibilities are examined and shown to be less likely. Meteor ablation on Venus, the aeronomy of metallic species, and the role of negative ions near the electron peaks of the atmosphere are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 81; Sept. 1
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  • 89
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    Direct photography of the Gum Nebula (1976)
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    Publication Date: 2011-08-16
    Description: The paper discusses a series of wide-angle photographs taken of the Gum Nebula in the traditional region including H-alpha with the aid of a 40-cm and an 80-cm lens in both the red and the green. The photographs support the large dimensions (75 deg in galactic longitude by 40 deg in galactic latitude) of the Gum Nebula suggested earlier, and the appearance is consistent with an origin due to photons from a supernova outburst. The relatively high-density gas has cooled and is visible on the red plates. The low-density gas has remained at a high temperature and may be visible as diffuse emission on the green plates.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; 208; Aug. 15
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  • 90
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    The Viking landing sites - Selection and certification (1976)
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    Publication Date: 2011-08-16
    Description: During the past several years the Viking project developed plans to use Viking orbiter instruments and earth-based radar to certify the suitability of the landing sites selected as the safest and most scientifically rewarding using Mariner 9 data. During June and July 1976, the earth-based radar and orbital spacecraft observations of some of the prime and backup sites were completed. The results of these combined observations indicated that the Viking 1 prime landing area in the Chryse region of Mars is geologically varied and possibly more hazardous than expected, and was not certifiable as a site for the Viking 1 landing. Consequently, the site certification effort had to be drastically modified and lengthened to search for a site that might be safe enough to attempt to land. The selected site considered at 47.5 deg W, 22.4 deg N represented a compromise between desirable characteristics observed with visual images and those inferred from earth-based radar. It lies in the Chryse region about 900 kilometers northwest of the original site.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 193; Aug. 27
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  • 91
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    The Halley rendezvous via solar sailing mission description (1976)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The possibility of using solar sails to achieve a rendezvous with Halley's Comet is explored. Rendezvous trajectories are calculated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Proc. of the Shuttle-Based Cometary Sci. Workshop; p 251-256
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  • 92
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    QH observations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A model of the dissociative lifetime of the hydroxyl radical is computed where the H2O and OH velocities are vectorially added. A lifetime of approximately 3 x 100,000 seconds is determined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Marshall Space Flight Center Proc. of the Shuttle-Based Cometary Sci. Workshop; p 222-226
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  • 93
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    Far-ultraviolet imagery of the Orion Nebula (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Two electrographic cameras carried on a sounding rocket have yielded useful-resolution far-ultraviolet (1000-2000 A) imagery of the Orion Nebula. The brightness distribution in the images is consistent with a primary source which is due to scattering of starlight by dust grains, although an emission-line contribution, particularly in the fainter outer regions, is not ruled out. The results are consistent with an albedo of the dust grains that is high in the far-ultraviolet and which increases toward shorter wavelengths below 1230 A.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 217
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  • 94
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    Martian isotopic ratios and upper limits for possible minor constituents as derived from Mariner 9 infrared spectrometer data (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 32; Sept
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  • 95
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    Impulsive penetration of filamentary plasma elements into the magnetospheres of the earth and Jupiter (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Assuming that the solar wind plasma is usually nonuniform over distances of 10,000 km or less, it is shown that filamentary plasma elements stretched out from the sun can penetrate impulsively and become engulfed into the magnetosphere. The diamagnetic effects associated with these plasma inhomogeneities are observed in outer magnetospheres and magnetosheaths as dips or directional discontinuities in the magnetic field measurements. From the mean penetration distances of these diamagnetic plasma elements one can deduce a mean deceleration time, as well as an approximate value of the integrated Pedersen conductivity in the polar cusp of the earth and Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science; 25; Sept
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  • 96
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    Distribution of molecular weight in glyceride polymerizates or aggregates of them after contact with lunar grains (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An attempt is made to report on experiments in which a molecular-weight increase was determined in thin layers of triglyceride-containing glycerides after thin-layer contact for two years with lunar topsoil grains at 25 C without any thermal activation. It is noted that solidification was observed on both dielectric grains and metal-rich areas and that changes in viscosity and molecular weights were first detected by solidification of surface layers. Gel permeation chromatography is described which detected a general shift of the Gaussian distribution of the molecular-weight data toward generally higher molecular weights as well as an increase in mean molecular weight. Reaction mechanisms are considered, and results of spectrographic analysis are cited which support the interpretations of the molecular-weight data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 16; May 1977
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  • 97
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    Possible Jovian methane emission at 76 GHz in coincidence with decameter activity (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The tentative detection of a methane line in emission at 76.2 GHz in the atmosphere of Jupiter is reported. The observed feature is well-correlated with the presence and absence of Jovian decameter-emission activity on successive days. The present results may represent the first detection of extraterrestrial methane microwave emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 216
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  • 98
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    OSO-8 X-ray observations of AM Herculis (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for hard X-ray observations of the binary system AM Her, which were coincident with soft X-ray and ground-based optical measurements. In the 2-60-keV band, variability was detected with an eclipse during phases 0.5 to 0.7 with respect to the 0.12892-day optical minima, synchronous with the known soft X-ray eclipse. The 2-60-keV uneclipsed flux was 9.5 by 10 to the -10th power erg/sq cm per sec, of which 86% lies above 10 keV. Thus, AM Her contains a hard source located near the similarly eclipsed soft X-ray source. The X-ray data are interpreted in terms of thermal bremsstrahlung from accretion onto a white dwarf.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 99
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    The far-infrared spectrum of the core of Sagittarius B2 (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A Michelson interferometer aboard NASA's Kuiper Airborne Observatory has been used to measure the spectrum of Sgr B2 from 40 to 200 kaysers with 5-kayser resolution in a 1.4-arcmin beam. The measured spectrum is smooth and featureless with a broad maximum at about 85 kaysers. The data can be fitted analytically with a model corresponding to thermal emission by a uniform sla of dust filling the beam, with an average temperature of approximately 32 K, an optical depth at 100 microns of about 1.6, and a spectral index of the dust emissivity about 1.5. The absence of features implies either that the source is optically thick or that the emission spectrum of the individual grains is smooth in the passband. The possible physical significance of this model is discussed.
    Keywords: ASTRONOMY
    Type: Astrophysical Journal; vol. 216
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  • 100
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    Optimum design and performance of Costas receivers containing soft bandpass limiters (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper investigates several key questions concerning the mechanization and design of a Costas receiver for reconstruction of a carrier from a suppressed carrier signal. For baseband NRZ encoded data symbols and a soft bandpass limiter preceding the loop, several design issues which are considered herein and which affect acquisition and tracking performance are: (1) The choice of an IF bandwidth. (2) The optimum choice of the Costas arm filter bandwidths as well as the spectral roll-off characteristics. (3) The optimum choice of loop bandwidth to data rate ratio for a given signal-to-noise ratio. (4) The signal suppression factor and the combined limiter-squaring loss. (5) The variations in loop bandwidth and damping with signal level. (6) The choice of the limiter transfer characteristic. (7) Performance degradation due to the presence of a limiter. Various new results in system design are presented and typical numerical results are given and graphically demonstrated in SNR regions of practical interest. The theory is applicable to the design of carrier reconstruction loops required in the implementation of spread spectrum communication receivers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Aug. 197
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