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  • 1
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    Ion neutral mass spectrometer results from the first flyby of Titan (2005)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2005-05-14
    Description: The Cassini Ion Neutral Mass Spectrometer (INMS) has obtained the first in situ composition measurements of the neutral densities of molecular nitrogen, methane, molecular hydrogen, argon, and a host of stable carbon-nitrile compounds in Titan's upper atmosphere. INMS in situ mass spectrometry has also provided evidence for atmospheric waves in the upper atmosphere and the first direct measurements of isotopes of nitrogen, carbon, and argon, which reveal interesting clues about the evolution of the atmosphere. The bulk composition and thermal structure of the moon's upper atmosphere do not appear to have changed considerably since the Voyager 1 flyby.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waite, J Hunter Jr -- Niemann, Hasso -- Yelle, Roger V -- Kasprzak, Wayne T -- Cravens, Thomas E -- Luhmann, Janet G -- McNutt, Ralph L -- Ip, Wing-Huen -- Gell, David -- De La Haye, Virginie -- Muller-Wordag, Ingo -- Magee, Brian -- Borggren, Nathan -- Ledvina, Steve -- Fletcher, Greg -- Walter, Erin -- Miller, Ryan -- Scherer, Stefan -- Thorpe, Rob -- Xu, Jing -- Block, Bruce -- Arnett, Ken -- New York, N.Y. -- Science. 2005 May 13;308(5724):982-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109-2143, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15890873" target="_blank"〉PubMed〈/a〉
    Keywords: Argon ; Atmosphere ; Carbon Isotopes ; *Elements ; Evolution, Planetary ; Extraterrestrial Environment ; *Hydrocarbons ; Hydrogen ; Isotopes ; Mass Spectrometry ; Methane ; Nitriles ; Nitrogen ; Nitrogen Isotopes ; *Saturn ; Spacecraft ; Temperature
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Cassini ion and neutral mass spectrometer: Enceladus plume composition and structure (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-03-11
    Description: The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (〈1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Waite, J Hunter Jr -- Combi, Michael R -- Ip, Wing-Huen -- Cravens, Thomas E -- McNutt, Ralph L Jr -- Kasprzak, Wayne -- Yelle, Roger -- Luhmann, Janet -- Niemann, Hasso -- Gell, David -- Magee, Brian -- Fletcher, Greg -- Lunine, Jonathan -- Tseng, Wei-Ling -- New York, N.Y. -- Science. 2006 Mar 10;311(5766):1419-22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Atmospheric, Oceanic, and Space Sciences, University of Michigan, Ann Arbor, MI 48109, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16527970" target="_blank"〉PubMed〈/a〉
    Keywords: Ammonia/analysis ; Atmosphere ; Carbon Dioxide/analysis ; Evolution, Planetary ; *Extraterrestrial Environment/chemistry ; Mass Spectrometry ; Methane/analysis ; *Saturn ; Spacecraft ; Water/analysis
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    A different view of plasma flow inside P/Halley (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The Giotto spacecraft carried two different instruments - the JPA and the IMS - for the observation of hot ions in the coma of P/Halley. Although there are many similarities in the time and distance profiles of the plasma flow parameters (bulk velocity, number density, and temperature) computed from the two data sets, there are also some significant differences, especially at cometocentric distances less than 500,000 km. The principal discrepancies between the JPA results presented by Formisano et al. (1990) and the IMS observations are: (1) the IMS did not detect the levelling off of the speed and temperature profiles that Formisano et al. interpreted as flow stabilization; (2) the IMS detected differential north-south flow between the solar wind and cometary ions for only a brief interval when the magnetic field was oriented nearly southward, whereas Formisano et al. reported more extensive differential north-south flow that was independent of the direction of the field; (3) the JPA ion densities were factors of 2 to 4 higher than the IMS ion densities which, in turn, were an order of magnitude greater than theoretical values.
    Keywords: ASTROPHYSICS
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 258; 2; p. 549-554.
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  • 4
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    Giotto IMS measurements of the production rate of hydrogen cyanide in the coma of Comet Halley (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The ion composition measurements in the ionosphere of Comet Halley by the ion mass spectrometer (IMS) experiment on the Giotto spacecraft are used to estimate the relative abundance of HCN. From a comparison of the normalized number density of ions with mass-to-charge (M/q) ratio of 28 AMU/e with steady-state photochemical models, it can be determined that the production rate of HCN directly from the central nucleus is Q(HCN) is less than about 0.0002 Q(H2O) at the time of Giotto encounter. The related photochemical- model calculations also indicate that Q(NH3)/Q(H2O) at the time of Giotto encounter. The related photo-chemical model calculations also indicate that Q(HN3)/Q(H2O) equals about 0.005, in agreement with recent determination from ground-based observations. The estimated value of Q(HCN) is lower than the relative abundance of Q(HCN)/Q(H2O) of about 0.001, as derived from radio observations of the 88.6 GHz emission of the J = 1 - 0 transition of HCN. The difference may be the result of time variations of the coma composition and dynamics, as well as other model-dependent effects.
    Keywords: ASTROPHYSICS
    Type: Annales Geophysicae (ISSN 0992-7689); 8; 319-325
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  • 5
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    Densities and abundances of hot cometary ions in the coma of P/Halley (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: On its flight by P/Halley, the Giotto spacecraft carried a High Energy Range Spectrometer (HERS) for measuring the properties of cometary ions picked up by the solar wind in the nearly collisionless regions of the coma. Preliminary estimates of the ion densities observed by HERS were reevaluated and extended; density profiles along the Giotto trajectory are presented for 13 values of ion mass/charge. Comparison with the physical-chemical model of the interaction of sunlight and the solar wind with the comet by other researchers reveals that, with the exception of protons and H2(+), all ion densities were at least an order of magnitude higher than predicted. The high ion densities cannot be explained on the basis of compression of the plasma, but require additional or stronger ionization mechanisms. Ratios of the densities of different ion species reveal an overabundance of carbonaceous material and an underabundance of H2(+) compared to the predictions of the Schmidt. While the densities of solar wind ions (H(+) and He(++)) changed sharply across a magnetic discontinuity located 1.35(10)(exp 5) km from the comet, this feature, which has been called both the 'cometopause' and the 'magnetic pileup boundary' was barely distinguishable in the density profiles of hot cometary ions. This result is consistent with the interpretation that the magnetic pileup boundary detected by Giotto was caused by a discontinuity in the solar wind and is not an intrinsic feature of the interaction of the solar wind with an active comet.
    Keywords: ASTROPHYSICS
    Type: LMSC, A Study of Ion Composition and Dynamics at Comet Halley; 34 p
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  • 6
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    An outer ion coma model in two dimension (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A simple cometary outer ion coma model is constructed by adopting published results from numerical MHD computations. The ion composition and density distributions so derived are used to highlight some of the basic features of cometary plasma flows and the need for cometary ion observations with absolute brightness calibration.
    Keywords: ASTROPHYSICS
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  • 7
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    Interpretation of the ion mass spectra in the mass range 25-35 obtained in the inner coma of Halley's comet by the HIS-sensor of the Giotto IMS Experiment (1991)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: The IMS-HIS double-focussing mass spectrometer that flew on the Giotto spacecraft covered the mass per charge range from 12 to 56 (AMU/e). By comparing flight data, calibration data, and results of model calculations of the ion population in the inner coma, the absolute mass scale is established, and ions in the mass range 25 to 35 are identified. Ions resulting from protonation of molecules with high proton affinity are relatively abundant, enabling us to estimate relative source strengths for H2CO, CH3OH, HCN, and H2S, providing for the first time a positive in situ measurement of methanol. Also, upper limits for NO and some hydrocarbons are derived.
    Keywords: ASTROPHYSICS
    Type: LMSC, A Study of Ion Composition and Dynamics at Comet Halley; 34 p
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  • 8
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    Observations of cometary plasma wave phenomena (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The ICE plasma wave investigation utilized very long electric antennas (100 m tip-to-tip) and a very high sensitivity magnetic search coil to obtain significant local information on plasma physics phenomena occurring in the distant pickup regions of Comet Giacobini-Zinner and Comet Halley; and information on the processes that developed in the coma and tail of Giacobini-Zinner. The ICE plasma wave measurements associated with both comet encounters are summarized, and high sensitivity ICE observations are related to corresponding measurements from the other Halley spacecraft.
    Keywords: ASTROPHYSICS
    Type: ESA Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 1: Plasma and Gas; p 163-168
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  • 9
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    Observations of solar wind ion charge exchange in the comet Halley coma (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Giotto Ion Mass Spectrometer/High Energy Range Spectrometer (IMS/HERS) observations of solar wind ions show charge exchange effects and solar wind compositional changes in the coma of comet Halley. As the comet was approached, the He(++) to proton density ratio increased until about 1 hour before closest approach after which time it decreased. Abrupt increases in this ratio were also observed in the beginning and near the end of the so-called Mystery Region (8.6 - 5.5(10)(exp 5) km from the comet along the spacecraft trajectory). These abrupt increases in the density ratio were well correlated with enhanced fluxes of keV electrons as measured by the Giotto plasma electron spectrometer. The general increase and then decrease of the He(++) to proton density ratio is quantitatively consistent with a combination of the addition of protons of cometary origin to the plasma and loss of plasma through charge exchange of protons and He(++). In general agreement with the solar wind proton and He(++) observations, solar wind oxygen and carbon ions were observed to charge exchange from higher to lower charge states with decreasing distance to the comet. The more abrupt increases in the He(++) to proton and the He(++) to O(6+) density ratios in the mystery region require a change in the solar wind ion composition in this region while the correlation with energetic electrons indicates processes associated with the comet.
    Keywords: ASTROPHYSICS
    Type: LMSC, A Study of Ion Composition and Dynamics at Comet Halley; 25 p
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  • 10
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    Observations of plasma dynamics in the coma of P/Halley by the Giotto Ion Mass Spectrometer (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Observations in the coma of P/Halley by the Giotto Ion Mass Spectrometer (IMS) are reported. The High Energy Range Spectrometer (HERS) of the IMS obtained measurements of protons and alpha particles from the far upstream region to the near ionopause region and of ions from mass 12 to 32 at distances of about 250,000 to 40,000 km from the nucleus. Plasma parameters from the High Intensity Spectrometer (HIS) of the IMS obtained between 150,000 to 5000 km from the nucleus are also discussed. The distribution functions of water group ions (water group will be used to refer to ions of 16 to 18 m/q, where m is in AMU and q is in unit charges) are observed to be spherically symmetric in velocity space, indicating strong pitch angle scattering. The discontinuity known as the magnetic pile-up boundary (MPB) is apparent only in proton, alpha, and magnetometer data, indicating that it is a tangential discontinuity of solar wind origin. HERS observations show no significant change in the properties of the heavy ions across the MPB. A comparison of the observations to an MHD model is made. The plasma flow directions at all distances greater than 30,000 km from the nucleus are in agreement with MHD calculations. However, despite the agreement in flow direction, within 200,000 km of the nucleus the magnitude of the velocity is lower than predicted by the MHD model and the density is much larger (a factor of 4). Within 30,000 km of the nucleus there are large theoretical differences between the MHD model flow calculations for the plane containing the magnetic field and for the plane perpendicular to the magnetic field. The observations agreed much better with the pattern calculated for the plane perpendicular to the magnetic field. The data obtained by the High Energy Range Spectrometer (HERS) of the IMS that are published herein were provided to the International Halley Watch archive.
    Keywords: ASTROPHYSICS
    Type: LMSC, A Study of Ion Composition and Dynamics at Comet Halley; 23 p
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