Cassini plasma spectrometer investigation

D. T. Young*, J. J. Berthelier, M. Blanc, J. L. Burch, A. J. Coates, R. Goldstein, M. Grande, T. W. Hill, R. E. Johnson, Väinö Kelha, D. J. Mccomas, E. C. Sittler, K. R. Svenes, K. Szegö, P. Tanskanen, Kimmo Ahola, D. Anderson, S. Bakshi, R. A. Baragiola, B. L. BarracloughR. K. Black, S. Bolton, T. Booker, R. Bowman, P. Casey, F. J. Crary, D. Delapp, G. Dirks, N. Eaker, H. Funsten, J. D. Furman, J. T. Gosling, H. Hannula, Christer Holmlund, H. Huomo, J. M. Illiano, P. Jensen, M. A. Johnson, D. R. Linder, T. Luntama, S. Maurice, K. P. Mccabe, K. Mursula, B. T. Narheim, J. E. Nordholt, A. Preece, J. Rudzki, A. Ruitberg, K. Smith, S. Szalai, M. F. Thomsen, Kai Viherkanto, J. Vilppola, T. Vollmer, T. E. Wahl, M. Wüest, Tomi Ylikorpi, C. Zinsmeyer

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    469 Citations (Scopus)

    Abstract

    The Cassini Plasma Spectrometer (CAPS) will make comprehensive three-dimensional mass-resolved measurements of the full variety of plasma phenomena found in Saturn's magnetosphere. Our fundamental scientific goals are to understand the nature of saturnian plasmas primarily their sources of ionization, and the means by which they are accelerated, transported, and lost. In so doing the CAPS investigation will contribute to understanding Saturn's magnetosphere and its complex interactions with Titan, the icy satellites and rings, Saturn's ionosphere and aurora, and the solar wind. Our design approach meets these goals by emphasizing two complementary types of measurements: high-time resolution velocity distributions of electrons and all major ion species; and lower-time resolution, high-mass resolution spectra of all ion species. The CAPS instrument is made up of three sensors: the Electron Spectrometer (ELS), the Ion Beam Spectrometer (IBS), and the Ion Mass Spectrometer (IMS). The ELS measures the velocity distribution of electrons from 0.6 eV to 28,250 keV, a range that permits coverage of thermal electrons found at Titan and near the ring plane as well as more energetic trapped electrons and auroral particles. The IBS measures ion velocity distributions with very high angular and energy resolution from 1 eV to 49,800 keV. It is specially designed to measure sharply defined ion beams expected in the solar wind at 9.5 AU, highly directional rammed ion fluxes encountered in Titan's ionosphere, and anticipated field-aligned auroral fluxes. The IMS is designed to measure the composition of hot, diffuse magnetospheric plasmas and low-concentration ion species 1 eV to 50,280 eV with an atomic resolution M/ΔM ∼70 and, for certain molecules, (such asN 2 + and CO+), effective resolution as high as ∼2500. The three sensors are mounted on a motor-driven actuator that rotates the entire instrument over approximately one-half of the sky every 3 min.

    Original languageEnglish
    Pages (from-to)1-112
    Number of pages112
    JournalSpace Science Reviews
    Volume114
    Issue number1-4
    DOIs
    Publication statusPublished - 1 Dec 2004
    MoE publication typeA1 Journal article-refereed

    Funding

    The ELS team leader, A. J. Coates, acknowledges the support of the Royal Society. We would like also to acknowledge the support of the rest of the ELS team including G. Abel, C. Alsop, T. Barsby, S. Burge, J. Coker, N. Flowers, L. Free, L. Gilbert, J. Godfrey, B. Hancock, J. Holmes, C. Jackman, A. Johnstone, D. Kelsh, P. Kendon, T. Murrell, J. Raymont, D. Reading, A. Rymer, J. Rose, P. Sheather, F.Thurlow, and L. Worth. Morgan-Matroc Limited, Rugby, U.K. supplied ELS anodes. ELS MCPs were supplied by Philips Components Ltd., France. Work at the University of Virginia supported in part by NASA’s Planetary Geology and Geophysics program. The CAPS actuator (ACT) was developed and manufactured by the VTT under contract to SwRI. We particularly wish to thank members of the laboratory and workshops of VTT Automation: T. Antila, H. Berg, the personnel of the Fine-Mechanical Prototype Shop, and especially K. Siitari of Rejlers Inc. The ACT stepper motor was manufactured by SAGEM of France and provided by CETP. Starsys Research Inc., of Boulder, CO manufactured the wax thermal actuators and the IMS cover mechanism. We wish to acknowledge the primary support for CAPS development and operations in the U.S. provided by NASA/Cal Tech/JPL through JPL contracts 958964, 959401, 959930, and 1243218 to the SwRI, and by JPL contract 1210586 to the University of Michigan. Initial R & D funding was made available by the Advisory Committee for Research at SwRI, and by the Department of Energy at Los Alamos National Laboratory. Work at CETP was supported by CNES grants 92/204 and 95/04; in Hungary by OMFB-07851 and a Hungarian Space Office grant MUI/TP/47; in Finland early development work on the ACT was supported by internal VTT funding, with further support provided by the Academy of Finland and the Ministry of Trade and Industry of Finland; in the U.K. by the Particle Physics and Astronomy Research Council; and in Norway by the Norwegian Defense Research Establishment and the Research Council of Norway.

    Keywords

    • Ion composition
    • Magnetosphere
    • Saturn
    • Space plasma
    • Titan

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