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31.
G. Randall Gladstone Steven C. Persyn John S. Eterno Brandon C. Walther David C. Slater Michael W. Davis Maarten H. Versteeg Kristian B. Persson Michael K. Young Gregory J. Dirks Anthony O. Sawka Jessica Tumlinson Henry Sykes John Beshears Cherie L. Rhoad James P. Cravens Gregory S. Winters Robert A. Klar Walter Lockhart Benjamin M. Piepgrass Thomas K. Greathouse Bradley J. Trantham Philip M. Wilcox Matthew W. Jackson Oswald H. W. Siegmund John V. Vallerga Rick Raffanti Adrian Martin J.-C. Gérard Denis C. Grodent Bertrand Bonfond Benoit Marquet François Denis 《Space Science Reviews》2017,213(1-4):447-473
The ultraviolet spectrograph instrument on the Juno mission (Juno-UVS) is a long-slit imaging spectrograph designed to observe and characterize Jupiter’s far-ultraviolet (FUV) auroral emissions. These observations will be coordinated and correlated with those from Juno’s other remote sensing instruments and used to place in situ measurements made by Juno’s particles and fields instruments into a global context, relating the local data with events occurring in more distant regions of Jupiter’s magnetosphere. Juno-UVS is based on a series of imaging FUV spectrographs currently in flight—the two Alice instruments on the Rosetta and New Horizons missions, and the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter mission. However, Juno-UVS has several important modifications, including (1) a scan mirror (for targeting specific auroral features), (2) extensive shielding (for mitigation of electronics and data quality degradation by energetic particles), and (3) a cross delay line microchannel plate detector (for both faster photon counting and improved spatial resolution). This paper describes the science objectives, design, and initial performance of the Juno-UVS. 相似文献
32.
H.Y. Wei C.T. Russell M.K. Dougherty Y.J. Ma K.C. Hansen H.J. McAndrews A. Wellbrock A.J. Coates M.F. Thomsen D.T. Young 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Observations of unusually large magnetic fields in the ionosphere indicate periods of maximum stress on Titan’s ionosphere and potentially of the strongest loss rates of ionospheric plasma. During Titan flyby T42, the observed magnetic field attained a maximum value of 37 nT between an altitude of 1200 and 1600 km, about 20 nT stronger than on any other Titan pass and close to five times greater in magnetic pressure. The strong fields occurred near the corotation-flow terminator rather than at the sub-flow point, suggesting that the flow which magnetized the ionosphere was from a direction far from corotation and possibly towards Saturn. Extrapolation of solar wind plasma conditions from Earth to Saturn using the University of Michigan MHD code predicts an enhanced solar wind dynamic pressure at Saturn close to this time. Cassini’s earlier exits from Saturn’s magnetosphere support this prediction because the Cassini Plasma Spectrometer instrument saw a magnetopause crossing three hours before the strong field observation. Thus it appears that Titan’s ionosphere was magnetized when the enhanced solar wind dynamic pressure compressed the Saturnian magnetosphere, and perhaps the magnetosheath magnetic field, against Titan. The solar wind pressure then decreased, leaving a strong fossil field in the ionosphere. When observed, this strong magnetic flux tube had begun to twist, further enhancing its strength. 相似文献
33.
Song T.L. Jo Young Ahn Tae Yoon Um 《IEEE transactions on aerospace and electronic systems》1990,26(5):867-875
A practical filter is suggested for ground-based missile tracking in a capture-guidance mode utilizing angle-only measurements from a passive missile sensor, and its performance is evaluated by a realistic system-simulation study. A missile-acceleration model that provides inputs to the filter is also suggested. The filter has a decoupled structure of independent azimuth and elevation channels, which requires fewer computations in solving the filter gain compared to a coupled structure. Simulation results show good tracking performance of the filter when used in association with the proposed missile-acceleration model 相似文献
34.
Blanc M. Bolton S. Bradley J. Burton M. Cravens T.E. Dandouras I. Dougherty M.K. Festou M.C. Feynman J. Johnson R.E. Gombosi T.G. Kurth W.S. Liewer P.C. Mauk B.H. Maurice S. Mitchell D. Neubauer F.M. Richardson J.D. Shemansky D.E. Sittler E.C. Tsurutani B.T. Zarka Ph. Esposito L.W. Grün E. Gurnett D.A. Kliore A.J. Krimigis S.M. Southwood D. Waite J.H. Young D.T. 《Space Science Reviews》2002,104(1-4):253-346
Magnetospheric and plasma science studies at Saturn offer a unique opportunity to explore in-depth two types of magnetospheres.
These are an ‘induced’ magnetosphere generated by the interaction of Titan with the surrounding plasma flow and Saturn's ‘intrinsic’
magnetosphere, the magnetic cavity Saturn's planetary magnetic field creates inside the solar wind flow. These two objects
will be explored using the most advanced and diverse package of instruments for the analysis of plasmas, energetic particles
and fields ever flown to a planet. These instruments will make it possible to address and solve a series of key scientific
questions concerning the interaction of these two magnetospheres with their environment.
The flow of magnetospheric plasma around the obstacle, caused by Titan's atmosphere/ionosphere, produces an elongated cavity
and wake, which we call an ‘induced magnetosphere’. The Mach number characteristics of this interaction make it unique in
the solar system. We first describe Titan's ionosphere, which is the obstacle to the external plasma flow. We then study Titan's
induced magnetosphere, its structure, dynamics and variability, and discuss the possible existence of a small intrinsic magnetic
field of Titan.
Saturn's magnetosphere, which is dynamically and chemically coupled to all other components of Saturn's environment in addition
to Titan, is then described. We start with a summary of the morphology of magnetospheric plasma and fields. Then we discuss
what we know of the magnetospheric interactions in each region. Beginning with the innermost regions and moving outwards,
we first describe the region of the main rings and their connection to the low-latitude ionosphere. Next the icy satellites,
which develop specific magnetospheric interactions, are imbedded in a relatively dense neutral gas cloud which also overlaps
the spatial extent of the diffuse E ring. This region constitutes a very interesting case of direct and mutual coupling between
dust, neutral gas and plasma populations. Beyond about twelve Saturn radii is the outer magnetosphere, where the dynamics
is dominated by its coupling with the solar wind and a large hydrogen torus. It is a region of intense coupling between the
magnetosphere and Saturn's upper atmosphere, and the source of Saturn's auroral emissions, including the kilometric radiation.
For each of these regions we identify the key scientific questions and propose an investigation strategy to address them.
Finally, we show how the unique characteristics of the CASSINI spacecraft, instruments and mission profile make it possible
to address, and hopefully solve, many of these questions. While the CASSINI orbital tour gives access to most, if not all,
of the regions that need to be explored, the unique capabilities of the MAPS instrument suite make it possible to define an
efficient strategy in which in situ measurements and remote sensing observations complement each other.
Saturn's magnetosphere will be extensively studied from the microphysical to the global scale over the four years of the mission.
All phases present in this unique environment — extended solid surfaces, dust and gas clouds, plasma and energetic particles
— are coupled in an intricate way, very much as they are in planetary formation environments. This is one of the most interesting
aspects of Magnetospheric and Plasma Science studies at Saturn. It provides us with a unique opportunity to conduct an in situ investigation of a dynamical system that is in some ways analogous to the dusty plasma environments in which planetary systems
form.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
35.
36.
T. E. Moore C. R. Chappell M. O. Chandler S. A. Fields C. J. Pollock D. L. Reasoner D. T. Young J. L. Burch N. Eaker J. H. Waite Jr. D. J. McComas J. E. Nordholdt M. F. Thomsen J. J. Berthelier R. Robson 《Space Science Reviews》1995,71(1-4):409-458
The Thermal Ion Dynamics Experiment (TIDE) and the Plasma Source Instrument (PSI) have been developed in response to the requirements of the ISTP Program for three-dimensional (3D) plasma composition measurements capable of tracking the circulation of low-energy (0–500 eV) plasma through the polar magnetosphere. This plasma is composed of penetrating magnetosheath and escaping ionospheric components. It is in part lost to the downstream solar wind and in part recirculated within the magnetosphere, participating in the formation of the diamagnetic hot plasma sheet and ring current plasma populations. Significant obstacles which have previously made this task impossible include the low density and energy of the outflowing ionospheric plasma plume and the positive spacecraft floating potentials which exclude the lowest-energy plasma from detection on ordinary spacecraft. Based on a unique combination of focusing electrostatic ion optics and time of flight detection and mass analysis, TIDE provides the sensitivity (seven apertures of 1 cm2 effective area each) and angular resolution (6°×18°) required for this purpose. PSI produces a low energy plasma locally at the POLAR spacecraft that provides the ion current required to balance the photoelectron current, along with a low temperature electron population, regulating the spacecraft potential slightly positive relative to the space plasma. TIDE/PSI will: (a) measure the density and flow fields of the solar and terrestrial plasmas within the high polar cap and magnetospheric lobes; (b) quantify the extent to which ionospheric and solar ions are recirculated within the distant magnetotail neutral sheet or lost to the distant tail and solar wind; (c) investigate the mass-dependent degree energization of these plasmas by measuring their thermodynamic properties; (d) investigate the relative roles of ionosphere and solar wind as sources of plasma to the plasma sheet and ring current.Deceased. 相似文献
37.
38.
The best active twist schedules exploiting various waveform types are sought taking advantage of the global search algorithm for the reduction of hub vibration and/or power required of a rotor in high-speed conditions.The active twist schedules include two non-harmonic inputs formed based on segmented step functions as well as the simple harmonic waveform input.An advanced Particle Swarm assisted Genetic Algorithm (PSGA) is employed for the optimizer.A rotorcraft Computational Structural Dynamics (CSD) code CAMRAD Ⅱ is used to perform the rotor aeromechanics analysis.A Computation Fluid Dynamics (CFD) code is coupled with CSD for verification and some physical insights.The PSGA optimization results are verified against the parameter sweep study performed using the harmonic actuation.The optimum twist schedules according to the performance and/or vibration reduction strategy are obtained and their optimization gains are compared between the actuation cases.A two-phase non-harmonic actuation schedule demonstrates the best outcome in decreasing the power required while a four-phase non-harmonic schedule results in the best vibration reduction as well as the simultaneous reductions in the power required and vibration.The mechanism of reduction to the performance gains is identified illustrating the section airloads,angle-of-attack distribution,and elastic twist deformation predicted by the present approaches. 相似文献
39.
40.
Uut de Haag M. Sayre J. Campbell J. Young S.D. Gray R.A. 《IEEE transactions on aerospace and electronic systems》2005,41(2):386-406
A real-time terrain database integrity monitor for synthetic vision systems (SVS) that are to be used in civil aviation is presented. SVS provides pilots with advanced display technology including terrain information as well as other information about the external environment such as obstacles and traffic. The use of SVS to support strategic and tactical decision-making and the compelling nature of the terrain depiction may require terrain database server certification at the essential and flight-critical levels. SVS and terrain database characteristics are discussed and a failure model is identified. Real-time integrity monitors are proposed that check the consistency between terrain profiles described by the database and terrain profiles that are sensed in flight by either a downward-looking (DWL) sensor or a forward-looking (FWL) season A DWL sensor scheme is discussed in detail and it is shown that this scheme can provide the necessary integrity required for an essential certification of a terrain database server. 相似文献