排序方式: 共有152条查询结果,搜索用时 62 毫秒
131.
Sharon Kedar Jose Andrade Bruce Banerdt Pierre Delage Matt Golombek Matthias Grott Troy Hudson Aaron Kiely Martin Knapmeyer Brigitte Knapmeyer-Endrun Christian Krause Taichi Kawamura Philippe Lognonne Tom Pike Youyi Ruan Tilman Spohn Nick Teanby Jeroen Tromp James Wookey 《Space Science Reviews》2017,211(1-4):315-337
InSight’s Seismic Experiment for Interior Structure (SEIS) provides a unique and unprecedented opportunity to conduct the first geotechnical survey of the Martian soil by taking advantage of the repeated seismic signals that will be generated by the mole of the Heat Flow and Physical Properties Package (HP3). Knowledge of the elastic properties of the Martian regolith have implications to material strength and can constrain models of water content, and provide context to geological processes and history that have acted on the landing site in western Elysium Planitia. Moreover, it will help to reduce travel-time errors introduced into the analysis of seismic data due to poor knowledge of the shallow subsurface. The challenge faced by the InSight team is to overcome the limited temporal resolution of the sharp hammer signals, which have significantly higher frequency content than the SEIS 100 Hz sampling rate. Fortunately, since the mole propagates at a rate of \(\sim1~\mbox{mm}\) per stroke down to 5 m depth, we anticipate thousands of seismic signals, which will vary very gradually as the mole travels.Using a combination of field measurements and modeling we simulate a seismic data set that mimics the InSight HP3-SEIS scenario, and the resolution of the InSight seismometer data. We demonstrate that the direct signal, and more importantly an anticipated reflected signal from the interface between the bottom of the regolith layer and an underlying lava flow, are likely to be observed both by Insight’s Very Broad Band (VBB) seismometer and Short Period (SP) seismometer. We have outlined several strategies to increase the signal temporal resolution using the multitude of hammer stroke and internal timing information to stack and interpolate multiple signals, and demonstrated that in spite of the low resolution, the key parameters—seismic velocities and regolith depth—can be retrieved with a high degree of confidence. 相似文献
132.
Mihail P. Petkov Steven M. Jones Gerald E. Voecks Kenneth J. Hurst Olivier Grosjean Delphine Faye Guillaume Rioland Cecily M. Sunday Emma M. Bradford William N. Warner Jerami M. Mennella Ned W. Ferraro Manuel Gallegos David M. Soules Philippe Lognonné W. Bruce Banerdt Jeffrey W. Umland 《Space Science Reviews》2018,214(8):112
We report on the development of a passive sorption pump, capable of maintaining high-vacuum conditions in the InSight seismometer throughout the duration of any extended mission. The adsorber material is a novel zeolite-loaded aerogel (ZLA) composite, which consists of fine zeolite particles homogeneously dispersed throughout a porous silica network. The outgassing species within the SEIS evacuated container were analyzed and the outgassing rate was estimated by different methods. The results were used to optimize the ZLA composition to adsorb the outgassing constituents, dominated by water, while minimizing the SEIS bakeout constraints. The InSight ZLA composite additionally facilitated substantial CO2 adsorption capabilities for risk mitigation against external leaks in Mars atmosphere. To comply with the stringent particle requirements, the ZLA getters were packaged in sealed containers, open to the SEIS interior through \(1~\upmu\mbox{m}\)-size pore filters. Results from experimental validation and verification tests of the packaged getters are presented. The pressure forecast based on these data, corroborated by rudimentary in situ pressure measurements, infer SEIS operational pressures not exceeding \(10^{-5}~\mbox{mbar}\) throughout the mission. 相似文献
133.
In this paper, we discuss the main ways of improving the aircraft aerodynamics. The results of a physical experiment are presented that is aimed to verify the theoretical results obtained earlier on the possible improvement in a seaplane wing model lift-to-drag ratio, by using a deflectable triangular extension along the wing leading edge near the wingtip. We confirm the slight effectiveness of using the wingtip leading edge triangular extensions on the nature of flow around the wing. 相似文献
134.
Alberto Adriani Gianrico Filacchione Tatiana Di Iorio Diego Turrini Raffaella Noschese Andrea Cicchetti Davide Grassi Alessandro Mura Giuseppe Sindoni Massimo Zambelli Giuseppe Piccioni Maria T. Capria Federico Tosi Roberto Orosei Bianca M. Dinelli Maria L. Moriconi Elio Roncon Jonathan I. Lunine Heidi N. Becker Alessadro Bini Alessandra Barbis Luciano Calamai Claudio Pasqui Stefano Nencioni Maurizio Rossi Marco Lastri Roberto Formaro Angelo Olivieri 《Space Science Reviews》2017,213(1-4):393-446
JIRAM is an imager/spectrometer on board the Juno spacecraft bound for a polar orbit around Jupiter. JIRAM is composed of IR imager and spectrometer channels. Its scientific goals are to explore the Jovian aurorae and the planet’s atmospheric structure, dynamics and composition. This paper explains the characteristics and functionalities of the instrument and reports on the results of ground calibrations. It discusses the main subsystems to the extent needed to understand how the instrument is sequenced and used, the purpose of the calibrations necessary to determine instrument performance, the process for generating the commanding sequences, the main elements of the observational strategy, and the format of the scientific data that JIRAM will produce. 相似文献
135.
Brigitte Knapmeyer-Endrun Matthew P. Golombek Matthias Ohrnberger 《Space Science Reviews》2017,211(1-4):339-382
The SEIS (Seismic Experiment for Interior Structure) instrument onboard the InSight mission will be the first seismometer directly deployed on the surface of Mars. From studies on the Earth and the Moon, it is well known that site amplification in low-velocity sediments on top of more competent rocks has a strong influence on seismic signals, but can also be used to constrain the subsurface structure. Here we simulate ambient vibration wavefields in a model of the shallow sub-surface at the InSight landing site in Elysium Planitia and demonstrate how the high-frequency Rayleigh wave ellipticity can be extracted from these data and inverted for shallow structure. We find that, depending on model parameters, higher mode ellipticity information can be extracted from single-station data, which significantly reduces uncertainties in inversion. Though the data are most sensitive to properties of the upper-most layer and show a strong trade-off between layer depth and velocity, it is possible to estimate the velocity and thickness of the sub-regolith layer by using reasonable constraints on regolith properties. Model parameters are best constrained if either higher mode data can be used or additional constraints on regolith properties from seismic analysis of the hammer strokes of InSight’s heat flow probe HP3 are available. In addition, the Rayleigh wave ellipticity can distinguish between models with a constant regolith velocity and models with a velocity increase in the regolith, information which is difficult to obtain otherwise. 相似文献
136.
G. M. Martínez C. N. Newman A. De Vicente-Retortillo E. Fischer N. O. Renno M. I. Richardson A. G. Fairén M. Genzer S. D. Guzewich R. M. Haberle A.-M. Harri O. Kemppinen M. T. Lemmon M. D. Smith M. de la Torre-Juárez A. R. Vasavada 《Space Science Reviews》2017,212(1-2):295-338
We analyze the complete set of in-situ meteorological data obtained from the Viking landers in the 1970s to today’s Curiosity rover to review our understanding of the modern near-surface climate of Mars, with focus on the dust, CO2 and H2O cycles and their impact on the radiative and thermodynamic conditions near the surface. In particular, we provide values of the highest confidence possible for atmospheric opacity, atmospheric pressure, near-surface air temperature, ground temperature, near-surface wind speed and direction, and near-surface air relative humidity and water vapor content. Then, we study the diurnal, seasonal and interannual variability of these quantities over a span of more than twenty Martian years. Finally, we propose measurements to improve our understanding of the Martian dust and H2O cycles, and discuss the potential for liquid water formation under Mars’ present day conditions and its implications for future Mars missions. Understanding the modern Martian climate is important to determine if Mars could have the conditions to support life and to prepare for future human exploration. 相似文献
137.
138.
M. C. De Sanctis A. Coradini E. Ammannito G. Filacchione M. T. Capria S. Fonte G. Magni A. Barbis A. Bini M. Dami I. Ficai-Veltroni G. Preti VIR Team 《Space Science Reviews》2011,163(1-4):329-369
The Dawn spectrometer (VIR) is a hyperspectral spectrometer with imaging capability. The design fully accomplishes Dawn’s scientific and measurement objectives. Determination of the mineral composition of surface materials in their geologic context is a primary Dawn objective. The nature of the solid compounds of the asteroid (silicates, oxides, salts, organics and ices) can be identified by visual and infrared spectroscopy using high spatial resolution imaging to map the heterogeneity of asteroid surfaces and high spectral resolution spectroscopy to determine the composition unambiguously. The VIR Spectrometer—covering the range from the near UV (0.25 μm) to the near IR (5.0 μm) and having moderate to high spectral resolution and imaging capabilities—is the appropriate instrument for the determination of the asteroid global and local properties. VIR combines two data channels in one compact instrument. The visible channel covers 0.25–1.05 μm and the infrared channel covers 1–5.0 μm. VIR is inherited from the VIRTIS mapping spectrometer (Coradini et al. in Planet. Space Sci. 46:1291–1304, 1998; Reininger et al. in Proc. SPIE 2819:66–77, 1996) on board the ESA Rosetta mission. It will be operated for more than 2 years and spend more than 10 years in space. 相似文献
139.
A. A. Baranov A. F. B. de Prado V. Yu. Razumny Anatoly A. BaranovJr. 《Cosmic Research》2011,49(3):269-279
Four types of optimal solutions are demonstrated to exist for transfers (time of flight is not fixed) between close near-circular
coplanar orbits. One solution is realized with the help of fixed orientation of the propulsion system (PS) along a transversal
in the orbital coordinate system. Another is reached at fixed orientation of the PS in the inertial coordinate system. The
third and fourth types of solutions change the PS orientation in the process of executing the maneuver. Regions of existence
are established for all types of solutions, and algorithms for determination of parameters of these maneuvers are suggested.
The algorithms were used to calculate parameters of the maneuvers of transfer from a launching orbit to a working Sun-synchronous
orbit, and to calculate the maneuvers of supporting the parameters of such an orbit in a specified range. 相似文献
140.
Vytenis M. Vasyliūnas 《Space Science Reviews》2011,158(1):91-118
Many widely used methods for describing and understanding the magnetosphere are based on balance conditions for quasi-static
equilibrium (this is particularly true of the classical theory of magnetosphere/ionosphere coupling, which in addition presupposes
the equilibrium to be stable); they may therefore be of limited applicability for dealing with time-variable phenomena as
well as for determining cause-effect relations. The large-scale variability of the magnetosphere can be produced both by changing
external (solar-wind) conditions and by non-equilibrium internal dynamics. Its developments are governed by the basic equations
of physics, especially Maxwell’s equations combined with the unique constraints of large-scale plasma; the requirement of
charge quasi-neutrality constrains the electric field to be determined by plasma dynamics (generalized Ohm’s law) and the
electric current to match the existing curl of the magnetic field. The structure and dynamics of the ionosphere/magnetosphere/solar-wind
system can then be described in terms of three interrelated processes: (1) stress equilibrium and disequilibrium, (2) magnetic
flux transport, (3) energy conversion and dissipation. This provides a framework for a unified formulation of settled as well
as of controversial issues concerning, e.g., magnetospheric substorms and magnetic storms. 相似文献