排序方式: 共有27条查询结果,搜索用时 375 毫秒
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S. A. Stern D. C. Slater J. Scherrer J. Stone M. Versteeg M. F. A’hearn J. L. Bertaux P. D. Feldman M. C. Festou Joel Wm. Parker O. H. W. Siegmund 《Space Science Reviews》2007,128(1-4):507-527
We describe the design, performance and scientific objectives of the NASA-funded ALICE instrument aboard the ESA Rosetta asteroid flyby/comet rendezvous mission. ALICE is a lightweight, low-power, and low-cost imaging spectrograph optimized for cometary far-ultraviolet (FUV) spectroscopy. It will be the first UV spectrograph to study a comet at close range. It is designed to obtain spatially-resolved spectra of Rosetta mission targets in the 700–2050 Å spectral band with a spectral resolution between 8 Å and 12 Å for extended sources that fill its ~0.05^ × 6.0^ field-of-view. ALICE employs an off-axis telescope feeding a 0.15-m normal incidence Rowland circle spectrograph with a toroidal concave holographic reflection grating. The microchannel plate detector utilizes dual solar-blind opaque photocathodes (KBr and CsI) and employs a two-dimensional delay-line readout array. The instrument is controlled by an internal microprocessor. During the prime Rosetta mission, ALICE will characterize comet 67P/Churyumov-Gerasimenko's coma, its nucleus, and nucleus/coma coupling; during cruise to the comet, ALICE will make observations of the mission's two asteroid flyby targets and of Mars, its moons, and of Earth's moon. ALICE has already successfully completed the in-flight commissioning phase and is operating well in flight. It has been characterized in flight with stellar flux calibrations, observations of the Moon during the first Earth fly-by, and observations of comet C/2002 T7 (LINEAR) in 2004 and comet 9P/Tempel 1 during the 2005 Deep Impact comet-collision observing campaign. 相似文献
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William V. Boynton Ann L. Sprague Sean C. Solomon Richard D. Starr Larry G. Evans William C. Feldman Jacob I. Trombka Edgar A. Rhodes 《Space Science Reviews》2007,131(1-4):85-104
The instrument suite on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft is well suited
to address several of Mercury’s outstanding geochemical problems. A combination of data from the Gamma-Ray and Neutron Spectrometer
(GRNS) and X-Ray Spectrometer (XRS) instruments will yield the surface abundances of both volatile (K) and refractory (Al,
Ca, and Th) elements, which will test the three competing hypotheses for the origin of Mercury’s high bulk metal fraction:
aerodynamic drag in the early solar nebula, preferential vaporization of silicates, or giant impact. These same elements,
with the addition of Mg, Si, and Fe, will put significant constraints on geochemical processes that have formed the crust
and produced any later volcanism. The Neutron Spectrometer sensor on the GRNS instrument will yield estimates of the amount
of H in surface materials and may ascertain if the permanently shadowed polar craters have a significant excess of H due to
water ice. A comparison of the FeO content of olivine and pyroxene determined by the Mercury Atmospheric and Surface Composition
Spectrometer (MASCS) instrument with the total Fe determined through both GRNS and XRS will permit an estimate of the amount
of Fe present in other forms, including metal and sulfides. 相似文献
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The importance of spectroscopy in the 80–800 å region for plasma diagnostics in the solar atmosphere
We discuss the importance of the spectral range from about 80 to 800 Å for determining physical conditions in different regions of the solar atmosphere. We give examples of line ratios that may be used to determine electron densities in quiet Sun regions, active regions, and flares. We discuss the possibility of determining electron temperatures from line ratios in the EUV.We show that profiles as well as intensities of spectral lines must be obtained for a proper interpretation of the spectra. We give approximate parameters for a solar grazing incidence spectrograph suitable for the study of the 80–800 Å wavelength region.Given as an invited review paper at the EGAS Meeting in Munich, Germany, 11–14 July 1978. 相似文献
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Paul D. Feldman 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(9):177-184
Since its launch in 1978 the () satellite observatory has been used to record ultraviolet spectra of nearly two dozen comets. These observations have been applied principally to studies of the composition, chemistry and evolution of the gaseous coma and more recently, with the substantially increased data base, to comparative analyses. The observations of Comets Bowell (1982 I) and Cernis (1983?) at a heliocentric distance of ≈ 3.4 AU show these two comets to be virtually identical and pose problems for water ice vaporization models. The most significant recent result from was the discovery of S2 in the Earth-approaching comet IRAS-Araki-Alcock (1983d) and the use of the S2 emission as a monitor of short-term variations in cometary activity. In early 1984, periodic comet Encke was observed for the second time by , this time post-perihelion. 相似文献
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Klaus Wilhelm Eckart Marsch Bhola N. Dwivedi Uri Feldman 《Space Science Reviews》2007,133(1-4):103-179
In Part I of this review, the concepts of solar vacuum-ultraviolet (VUV) observations were outlined together with a discussion
of the space instrumentation used for the investigations. A section on spectroradiometry provided some quantitative results
on the solar VUV radiation without considering any details of the solar phenomena leading to the radiation. Here, in Part
II, we present solar VUV observations over the last decades and their interpretations in terms of the plasma processes and
the parameters of the solar atmosphere, with emphasis on the spatial and thermal structures of the chromosphere, transition
region and corona of the quiet Sun. In addition, observations of active regions, solar flares and prominences are included
as well as of small-scale events. Special sections are devoted to the elemental composition of the solar atmosphere and theoretical
considerations on the heating of the corona and the generation of the solar wind. 相似文献
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The composition of the solar photosphere is believed to be uniform. Indeed a quantity that does not vary with solar surface
location or with a particular solar feature, i.e., no observational evidence is available to indicate that the photospheric
composition near the solar equator is different from the photospheric composition near the solar poles or that the photospheric
composition in quiet regions is different from the composition in active regions. In contrast, the composition of the solar
upper atmosphere is not well defined. Solar composition work in recent decades has brought the recognition that there are
systematic differences between the composition of the corona and the photosphere and revealed evidence for spatial and time
variability in the composition of various coronal features. We review the spectroscopic techniques used and the progress that
was made in recent years in deriving the plasma compositions of various solar upper atmosphere structures.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献