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11.
Ludmilla Kolokolova Li Liu Michael I. Mishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(13):2175-2181
We study a new optical effect, a spectral manifestation of coherent backscattering, which reveals itself as systematic variations in the depth of absorption bands with changing phase angle. We used Cassini VIMS near-infrared spectra of Saturn's icy satellite Rhea in order to identify and characterize the spectral change with phase angle, focusing on the change in the depth of water-ice absorption bands. To model realistic characteristics of the surfaces of icy satellites, which are most likely covered by micron-sized densely packed particles, we perform simulations using a theoretical approach based on direct computer solutions of the macroscopic Maxwell equations. Our results show that this approach can reproduce the observed phase-angle variations in the depth of the absorption bands. The modeled changes in the absorption bands are strongly affected by physical properties of the regolith, especially by the size and packing density of the ice particles. Thus, the phase-angle spectral variations demonstrate a promising remote-sensing capability for studying properties of the surfaces of icy bodies and other objects that exhibit a strong coherent backscattering effect. 相似文献
12.
B. Pernice 《Il Nuovo Cimento C》1992,15(6):1133-1136
Summary The updated status of the cooperation between NASA and ASI on the Cassini mission is here presented. This outstanding scientific
mission is devoted to study the Saturnian system with a NASA orbiter and a ESA probe. The Italian involvement, managed by
the Agenzia Spaziale Italiana (ASI), concerns the design and development of important Cassini Orbiter subsystems. Promotion
of the Italian science community's interests and of the national industry's technological capabilities are the rationales
for the cooperation.
This is an updated version of the contribution presented at San Miniato. 相似文献
13.
The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite’s geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented. 相似文献
14.
The nonlinear attitude motion of gyrostat satellites in a central force field is investigated, with particular emphasis on their long-time dynamic behavior for a wide range of parameters. The numbers of equilibrium solutions, as well as their stability, vary with the rotor speed, and bifurcation diagrams have been obtained. Various dynamic behaviors of gyrostat satcllites, e.g. periodic, quasiperiodic, and chaotic, are studied via the Poincaré map technique. It is shown that the rotor speed has a significant effect on the dynamic behavior of gyrostat satellites. 相似文献
15.
K. Ram Narayana B. Seetharami Reddy S. S. Raju T. Seshi Reddy S. Lakshmi Narayana K. Premachand B. M. Rao M. V. R. Murti L. S. Mombasawala 《Pramana》2005,65(2):285-290
The KαL1/KαL0 intensity ratio of fluorine is measured in five fluorine compounds with a crystal spectrometer. An anomalous reduction of
this intensity ratio was observed in KF and SrF2, which is attributed to resonance electron transfer from the metal ion to the spectator vacancy in the fluorine ion. KαL2/KαL0 intensity ratio of fluorine is also measured. The measured relative intensities are compared with the theoretical estimates
of Aberg.
Formerly RSIC 相似文献
16.
Victoria Muñoz–Iglesias Laura Jiménez Bonales David Santamaría-Pérez Mercedes Taravillo Valentín García Baonza Olga Prieto-Ballesteros 《光谱学快报》2013,46(6):407-412
Clathrate hydrates are particular solids that planetologists study in detail because those solids may be present in several bodies of the solar system, such as Mars, comets, and the icy satellites. The solids are formed by solid H2O, like common water ice, but adopt open structures with cavities containing gas molecules. Clathrate hydrates are usually stable at relatively low temperature and high pressure, which are the typical conditions present inside these planetary objects. Their interest for astrobiology is that they represent potential sources of liquid water and gases when they decompose. The present work is focused on the crystallization of clathrates in Europa's (icy satellite of Jupiter) interior conditions. We postulate that clathrate hydrates may play an important role in its crust mineralogy and that it can explain some features of the satellite's surface due to their formation/destabilization. An in situ kinetic study by Raman Spectroscopy of the clathrate formation from salty solutions was performed in our laboratory. The chemical composition that we used mimics those obtained from Europa's surface during the Galileo mission. An effect of the salting-out process in the solution was monitored through the clathrate formational path. Our results demonstrate that this process may have geological consequences on Europa and confirm the suitability of Raman spectroscopy for planetary detection of clathrate hydrates and other ices. 相似文献
17.
The absorption spectrum of UF6 between 3400 and 4200 Å, is well-documented,(1–3) but the region below 3400 Å has not been studied in any detail. We present here a spectrum of UF6 between 2000 and 4200 Å that shows significant structure below 3400 Å. The absorption in this region must be observed at very low pressures and relatively short path lengths. 相似文献
18.
Surendra Poonia 《X射线光谱测定》2012,41(1):42-45
The satellite spectra arising due to the L3Mx–MxN4,5 (x = 1–5) transition array in the X‐ray emission spectra of 72Hf, 73Ta, 74W, 81Tl, 83Bi and 92U have been calculated using available HFS data on K–LM and L–MN Auger transition energies. The agreement between the calculated and measured energies, that between calculated and measured separations in energies and the consideration of the relative probabilities of all the L3Mx–MxN4,5 transitions have been used as the basis for deciding the origin of the satellites. It has been established that two satellites observed in the Lβ2 region of the X‐ray spectra of various elements, named β2I and β2II in the order of increasing energy, are mainly emitted by the L3M4,5–M4,5N4,5 transitions. It is observed that satellite β2I in the spectra of elements with 72Hf to 74W has been assigned to the superposition of the 3F4–3G5 and 3F4–3D3 transitions and must be the most intense one among all these satellites. The same transition has been proved to be the main origin of satellite β2II, reported in the element with 81Tl, 83Bi and 92U. Further, satellite β2I, reported in the spectra of elements with 81Tl and 92U, has been associated with the transitions 3D3–3F4 and 1D2–1F3. Finally, line β2II, reported in the spectra of elements with Z = 72–74, has been assigned to the 1F3–1G4 and 3P0–3D1 transitions. The possible contributions of other transitions of the L3Mx–MxN4,5 (x = 1–5) array having intensities comparable with those of the above transitions, as well as the corresponding lines that have not yet been observed, have also been discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
19.
20.
Mehdi Bouhram Jean-Jacques Berthelier Jean-Marie Illiano Howard T. Smith Edward C. Sittler Frank J. Crary Dave T. Young 《Comptes Rendus Physique》2005,6(10):1176-1181
The first pass of the Cassini probe in the vicinity of Saturn, above the E-ring, demonstrated a plasma consisting of water group ions (H+, O+, OH+, H2O+) with a small N+ ion component (3%). Using a simple model for the transport of magnetospheric ions, we show that the N+ ions can be traced back to the Enceladus satellite. Such a result can be explained by the existence in this icy satellite, supposed to be still geologically active, of volatile components such as ammonia NH3, or by the previous implantation of N+ ions of external origin on its surface. To cite this article: M. Bouhram et al., C. R. Physique 6 (2005). 相似文献