MAGNETOSPHERES AND MOONS. E. C. Sittler, J. F. Cooper, N. Paschalidis, S. L. Jones, W. L. Brinckerhoff, W. R. Paterson, A. Ali, M. A. Coplan, D. Chornay, S. J. Sturner, M. Benna, F. B. Bateman, D. Fontaine, C. Verdeil, N. Andre, M. Blanc and P. Wurz, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA, Edward.c.sittler@nasa.gov, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA, john.f.cooper@nasa.gov, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA, Nikolaos.paschalidis@nasa.gov, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA, sarah.l.jones@nasa.gov, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA, william.b.brinckerhoff@nasa.gov, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, USA, william.r.paterson@nasa.gov, Science Systems Applications, Inc., 6301 Ivy Lane, Suite 510, Greenbelt, MD, 20770, University of Maryland, College Park, MD, coplan@umd.edu, University of Maryland, College Park, MD/NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, dennis.j.chornay@nasa.gov, University of Maryland Baltimore County/NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, steven.j.sturner@nasa.gov, University of Maryland Baltimore County/NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD, 20771, mehdi.benna-1@nasa.gov, National Institute of Technology and Standards, Gaithersburg, MD, USA, fred.bateman@nist.gov, LPP-CNRS Ecole Polytechnique, Route de Saclay, 91128, Palaiseau, FR, Dominique.fontaine@lpp.polytechnique.fr, LPP-CNRS, 4 Place de Jussieu, tour 24-34, 75252, Paris, Cedex, FR, Christophe.verdeil@lpp.polytechnique.fr, IRAP, Center National de la Recherche Scientifique, Toulouse, FR, Nicolas.andre@irap.omp.eu, IRAP, Center National de la Recherche Scientifique, Toulouse, FR, michel.blanc@irap.omp.eu, University of Bern, Physikalisches Institut, Bern, Switzerland, peter.wurz@space.unibe.ch

Jupiter magnetospheric interactions and surface composition, both important to subsurface ocean detection for the Galilean icy moons Europa, Ganymede, and Callisto, can be measured using plasma ion mass spectrometry on either an orbiting spacecraft or one designed for multiple flybys of these moons. Detection of emergent oceanic materials at the Europa surface is more likely than at Ganymede and Callisto. A key challenge is to resolve potential intrinsic Europan materials from the space weathering patina of iogenic species implanted onto the sensible surface by magnetospheric interactions. Species-resolved measurements of pickup ion currents are also critical to extraction of oceanic induced magnetic fields from magnetospheric interaction background dominated by these currents. In general the chemical astrobiological potential of Europa should be determined through the combination of surface, ionospheric, and pickup ion composition measurements. The requisite Ion Mass Spectrometer (IMS) for these measurements would need to work in the high radiation environment of Jupiter's magnetosphere between the orbits of Europa and Ganymede, and beyond. A 3D hybrid model of the moon-magnetosphere interaction is also needed to construct a global model of the electric and magnetic fields, and the plasma environment, around Europa. Europa's ionosphere is probably usually dominated by hot pickup ions with 100–1000eV temperatures, excursions to a “classical” cold ionosphere likely being infrequent. A field aligned ionospheric wind driven by the electron polarization electric field should arise and be measurable.

Every scientific apparatus requires a mechanical structure, even a device that is fundamentally electronic or optical in nature. The design of this structure determines to a large extent the usefulness of the apparatus. It follows that a successful scientist must acquire many of the skills of the mechanical engineer in order to proceed rapidly with an experimental investigation. The designer of research apparatus must strike a balance between the makeshift and the permanent. Too little initial consideration of the expected performance of a machine may frustrate all attempts to get data. Too much time spent planning can also be an error, since the performance of a research apparatus is not entirely predictable. A new machine must be built and operated before all the shortcomings in its design are apparent. The function of a machine should be specified in some detail before design work begins. One must be realistic in specifying the job of a particular device. The introduction of too much flexibility can hamper a machine in the performance of its primary function. On the other hand, it may be useful to allow space in an initial design for anticipated modifications. Problems of assembly and disassembly should be considered at the outset, since research equipment rarely functions properly at first and often must be taken apart and reassembled repeatedly. Make a habit of studying the design and operation of machines. Learn to visualize in three dimensions the size and positions of the parts of an instrument in relation to one another. Before beginning a design, learn what has been done before. It is a good idea to build and maintain a library of commercial catalogs in order to be familiar with what is available from outside sources. Too many scientific designers waste time and money on the reinvention of the wheel and the screw. Use nonstandard parts only when their advantages justify the great cost of one-off construction in comparison with mass production. Consider modifications of a design that will permit the use of standardized parts. An evening spent leafing through the catalog of one of the major tool and hardware suppliers can be remarkably educational – catalogs from McMaster-Carr or W. M. Berg, for example, each list over 200 000 standard fasteners, bearings, gears, mechanical and electrical parts, tools etc. Become aware of the available range of commercial services. In most big cities, specialty job shops perform such operations as casting, plating, and heat-treating inexpensively. In many cases it is cheaper to have others provide these services rather than attempt them oneself. Some of the thousands of suppliers of useful services, as well as manufacturers of useful materials, are noted throughout the text. In the following sections we discuss the properties of materials and the means of joining materials to create a machine. The physical principles of mechanical design are presented. These deal primarily with controlling the motion of one part of a machine with respect to another, both where motion is desirable and where it is not. There are also sections on machine tools and on mechanical drawing. The former is mainly intended to provide enough information to enable the scientist to make intelligent use of the services of a machine shop. The latter is presented in sufficient detail to allow effective communication with people in the shop.

The interactions between plasma structures and neutral atom populations in interplanetary space can be effectively studied with energetic neutral atom imagers. For neutral atoms with energies less than 1 keV, the most efficient detection method that preserves direction and energy information is conversion to negative ions on surfaces. We have examined a variety of surface materials and conversion geometries in order to identify the factors that determine conversion efficiency. For chemically and physically stable surfaces smoothness is of primary importance while properties such as work function have no obvious correlation to conversion efficiency. For the noble metals, tungsten, silicon, and graphite with comparable smoothness, conversion efficiency varies by a factor of two to three. We have also examined the way in which surface conversion efficiency varies with the angle of incidence of the neutral atom and have found that the highest efficiencies are obtained at angles of incidence greater then 80deg. The conversion efficiency of silicon, tungsten and graphite were examined most closely and the energy dependent variation of conversion efficiency measured over a range of incident angles. We have also developed methods for micromachining silicon in order to reduce the volume to surface area over that of a single flat surface and have been able to reduce volume to surface area ratios by up to a factor of 60. With smooth micro-machined surfaces of the optimum geometry, conversion efficiencies can be increased by an order of magnitude over instruments like LENA on the IMAGE spacecraft without increase the instruments mass or volume.