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  • 1
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    The Beta Pictoris circumstellar disk. XV - Highly ionized species near Beta Pictoris (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Temporal variations of the Fe II, Mg II, and Al III circumstellar lines towards Beta Pictoris have been detected and monitored since 1985. However, the unusual presence of Al III ions is still puzzling, since the UV stellar flux from an A5V star such as Beta Pic is insufficient to produce such an ion. In order to better define the origin of such a phenomenon, new observations have been carried out to detect faint signatures of other highly ionized species in the short UV wavelength range, where the stellar continuum flux is low. These observations reveal variations not only near the C IV doublet lines, but also in C I and Al II lines, two weakly ionized species, not clearly detectable until now. In the framework of an infalling body scenario, highly ionized species would be created in the tail, far from the comet head, by collisions with ambient gas surrounding the star, or a weak stellar wind. Spectral changes have also been detected near a CO molecular band location, which, if confirmed, would provide the first molecular signature around Beta Pictoris.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 267; 1; p. 187-193.
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  • 2
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    Ultraviolet spectrometer experiment (1973)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The ultraviolet spectrometer (UVS) onboard the Apollo 17 orbiting spacecraft was used to measure emissions from the lunar atmosphere. The UVS and calibration are discussed along with the lunar atmosphere observations and lunar albedo measurements.
    Keywords: SPACE RADIATION
    Type: NASA. Johnson Space Center Apollo 17 Prelimin. Sci. Rept.; 10 p
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  • 3
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    Photoelectron excitation of N2 in the day airglow (1970)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Nitrogen photoelectron excitation in dayglow, examining 3371 A band intensity, energy spectrum and flux in ionosphere
    Keywords: SPACE RADIATION
    Type: ; TROPHYSICAL JOURNAL
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  • 4
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    The composition of comets (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Questions concerning the origin of comets are considered. It is pointed out that the molecular composition of a dense interstellar cloud appears to have exactly the composition needed to produce the observed features of the visible cometary spectrum, which consists mainly of emission bands of unstable free radicals. A working model of cometary structure is discussed together with the classical observations which have led to it. The discussed model was originally described by Whipple (1951). It is emphasized that the model can serve only as a rough guide in efforts to interpret the evolution of cometary behavior. A survey is provided of new techniques which have only recently been applied to cometary observations, taking into account the spectrum of a comet, radio observations, and ultraviolet observations.
    Keywords: ASTROPHYSICS
    Type: American Scientist; 65; May-June
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  • 5
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    Rocket measurements of low energy electrons and optical emissions in the dayglow and aurora. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: GEOPHYSICS
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  • 6
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    The spectrum of comets as derived from IUE observations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Eight comets were observed with the IUE at various-heliocentric and geocentric distances. Their UV spectra are remarkably similar despite the large differences in the dust to gas ratios. Since all the dominant atomic species (except N) radicals and ions of the coma are detected in this spectral region, the total gaseous output of the nucleus can be estimated. The abundance of the carbon atom-bearing species is still not very well known and there are indications that the CO content of the coma could vary from comet to comet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA 3rd European IUE Conf.; p 445-449
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  • 7
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    Spectroscopy of the extreme ultraviolet dayglow during active solar conditions (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The spectral characteristics of the mid-latitude daytime airglow observed between 530 and 1500 A under conditions of high solar activity are compared with those obtained at the same location during markedly lower solar activity. The spectral observations were made by two scanning spectrometers and an N2 3371 A photometer carried aboard Astrobee-F rockets launched from White Sands Missile Range, NM, on January 9, 1978 and June 27, 1980. The more recent data allow the partial resolution of the emission spectrum between 800 and 1200 A into a large number of weak N I, O I and N2 transitions. Data taken at 220 km altitude suggest an increase in atomic nitrogen density of more than a factor of 3 between the two observations, along with a doubling of the solar EUV flux at wavelengths less than 688 A. No evidence of a corresponding increase in the 10 to 50 eV photoelectron flux is found, however, an ionospheric sounding data indicate the peak electron density to have decreased during this period. The mechanism for this electron flux decrease in the face of increased EUV flux and only a three-fold increase in N concentration remains unknown.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 8; Dec. 198
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  • 8
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    Inner coma imaging of Comet Levy (1990c) with the Hubble Space Telescope (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Observations of comet Levy were carried out with the Hubble Space Telescope (HST) on UT 27 Sep. 1990. The comet was imaged with the Wide Field Camera (WFC) through both red and blue filters, which were selected to isolate continuum emission peaking sharply at the nucleus. The longest exposures (4 sec) through the red filter had sufficient signal to noise that image deconvolution could be used to recover virtually the full spatial resolution of HST. These images reveal a fan-shaped inner coma in which the sunward-facing hemisphere is significantly brighter than the tailward hemisphere, consistent with volatile sublimation occurring primarily on the dayside of the nucleus.
    Keywords: ASTRONOMY
    Type: Lunar and Planetary Inst., Abstracts for the International Conference on Asteroids, Comets, Meteors 1991; p 232
    Format: application/pdf
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  • 9
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    Ultraviolet spectroscopy of the zodiacal light at 20-deg elongation (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The zodiacal light at 20-deg elongation and 10-deg inclination was observed by rocket ultraviolet spectrometers at 10-15-A resolution in the spectral range 1200-3200 A during an experiment designed to observe comet Kohoutek (1973 XII). The data were obtained above 180 km when scattered horizon light in the startracker caused a loss of tracking on the comet. Airglow emission due to NO and O(+), identified spectroscopically and by its variation with altitude, is significant between 1900 and 2500 A. Longward of 2600 A, the spectrum matches that of the sun, and the derived value of the color ratio, relative to the visible, is 0.90 + or - 0.20. At 1600 A, an upper limit on the zodiacal-light emission of 0.07 R per A or 7 hundred-millionths erg/s per sq cm/sterad per A is obtained.
    Keywords: GEOPHYSICS
    Type: Astronomy and Astrophysics; 61; 5, De; Dec. 197
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  • 10
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    The UV dayglow 3, OI emissions at 989, 1027, 1152, 1304, and 1356A (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Rocket observations of the dayglow spectrum between 530 and 1500A were obtained on 9 January 1978 at a solar zenith angle of 56 deg. Data were obtained from 80 to 260 km with viewing angles of 40, 90, and 180 deg to the local zenith. OI emissions were observed at 989, 1027, 1152, 1304, and 1356A. Analysis of these data with a radiative transfer model using the energy dependences of currently accepted excitation cross sections, branching ratios and photoelectron fluxes shows that electron impact excitation is the primary source of these emissions. The infrared emission rates at 7990 and 11287A are also calculated in this analysis for comparison with previous observations and estimates.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters; 7; Dec. 198
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