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This paper reports on the Sub-keV Atom Reflecting Analyzer (SARA) experiment that will be flown on the first Indian lunar mission Chandrayaan-1. The SARA is a low energy neutral atom (LENA) imaging mass spectrometer, which will perform remote sensing of the lunar surface via detection of neutral atoms in the energy range from 10 eV to 3 keV from a 100km polar orbit. In this report we present the basic design of the SARA experiment and discuss various scientific issues that will be addressed. The SARA instrument consists of three major subsystems: a LENA sensor (CENA), a solar wind monitor (SWIM), and a digital processing unit (DPU). SARA will be used to image the solar wind-surface interaction to study primarily the surface composition and surface magnetic anomalies and associated mini-magnetospheres. Studies of lunar exosphere sources and space weathering on the Moon will also be attempted. SARA is the first LENA imaging mass spectrometer of its kind to be flown on a space mission. A replica of SARA is planned to fly to Mercury onboard the BepiColombo mission.

Context. The Rosetta spacecraft is escorting comet 67P/Churyumov-Gerasimenko from a heliocentric distance of >3.6 AU, where the comet activity was low, until perihelion at 1.24 AU. Initially, the solar wind permeates the thin comet atmosphere formed from sublimation. Aims. Using the Rosetta Plasma Consortium Ion Composition Analyzer (RPC-ICA), we study the gradual evolution of the comet ion environment, from the first detectable traces of water ions to the stage where cometary water ions accelerated to about 1 keV energy are abundant. We compare ion fluxes of solar wind and cometary origin. Methods. RPC-ICA is an ion mass spectrometer measuring ions of solar wind and cometary origins in the 10 eV–40 keV energy range. Results. We show how the flux of accelerated water ions with energies above 120 eV increases between 3.6 and 2.0 AU. The 24 h average increases by 4 orders of magnitude, mainly because high-flux periods become more common. The water ion energy spectra also become broader with time. This may indicate a larger and more uniform source region. At 2.0 AU the accelerated water ion flux is frequently of the same order as the solar wind proton flux. Water ions of 120 eV–few keV energy may thus constitute a significant part of the ions sputtering the nucleus surface. The ion density and mass in the comet vicinity is dominated by ions of cometary origin. The solar wind is deflected and the energy spectra broadened compared to an undisturbed solar wind. Conclusions. The flux of accelerated water ions moving from the upstream direction back toward the nucleus is a strongly nonlinear function of the heliocentric distance.

Wave induced attraction of matter is a unique aspect of ponderomotive forcing by electromagnetic (e/m) waves in plasmas. The Miller force, sometimes denoted the gradient force, is of particular interest, because the direction as well as magnitude of the Miller force on a plasma depends on the wave frequency. While plasma is usually considered in its gaseous form, solid bodies can also be treated as plasma, denoted solid-state plasma. The first experimental proof of wave effects in magnetized solid-state plasmas (Lundqvist, 1949, Herlofson, 1950) came after the suggestion by Alfv\'en (1942) on the possible existence of magneto-hydrodynamic (MHD) waves. However, most of our knowledge basis on MHD/Alfv\'en waves have since then emerged from space- and laboratory (gaseous) plasmas. It is therefore timely to investigate further the applicability of e/m wave ponderomotive forcing on solid-state plasma. In this report we discuss the applicability of the ponderomotive Miller force on solid-state plasmas. At this stage the treatise will be rather qualitative, based on theories developed for space plasma. We assume that e/m wave energy and momentum is transferred in a thin surface layer constituting solid-state plasma. A Miller force results from the wave pressure gradient set up in the surface layer. Since the solid body constitute a coupled system (lattice), the Miller force will act on all atoms in the body, the total force limited by the wave input power. A quantitative comparison with experimental results obtained from a Cavendish vacuum experiment (Lidgren and Lundin, 2010) gives a surprisingly good agreement between theory and experiments. As further proof for e/m wave attraction of matter, we show a simulation, taking into account the measured pendulum offsets., Comment: 13 pages, 2 figures

We present measurement results demonstrating that a conducting lead sphere exposed to electromagnetic (e/m) waves in the infrared (IR) regime, is attracted by e/m waves. The result may seem surprising and against conventional wisdom that electromagnetic wave forcing should lead to a repulsive force. Nonetheless, all our experiments show that the attractive force can be determined quantitatively, and that they are reproducible. Our experiment setup is a Cavendish torsion-balance experiment with lead spheres, one of the spheres intermittently irradiated by IR light. Because the Cavendish experiment is well known, simple, and readily available, the results can be easily verified or falsified. However, to avoid Bernoulli and other external forcing effects, the entire experimental setup should be placed in a vacuum chamber. In our case the experiments were performed at \approx 4 \cdot 10^-7 mbar. One of the 20 g lead spheres was intermittently irradiated by infrared radiation from a lamp covered by an aluminium foil. Two independent experiments (V1 and V2) are described. Besides showing that wave energy and momentum transfer leads to attraction, we also describe some experimental requirements and constraints. The lamp was powered on during 10 or 12 s, the power changing between 8, 16, and 26 W. All measurements, including those affected by lamp out-gassing, shows that the attracting force on the lead sphere increases with increasing irradiative energy. From the V2 experiment, preceded by lamp "baking" to eliminate repulsive out-gassing forces, the irradiative energy 8.7 Ws on the sphere resulted in a total force 2.9+/-0.5\cdot 10^-9 (N). From the V2 experiment we also derive a power law relation between incident radiation energy (W) and the attractive force, corresponding to F=2.8\cdot 10^-10 W^1.1, with R^2=0.95., Comment: 17 pages, 6 figures

Mars Orbiting Plasma Surveyor (MOPS) is a microsatellite mission focused on studies of the near -Mars environment and the planet - solar wind interaction. The recent findings by the ESA Mars Express mission further highlighted the complexity of the processes taking place at the planet resulting from the solar wind interaction that strongly affect the planet's atmosphere. However, despite many previous Martian missions carrying different types of space plasma experiments, a comprehensive investigation including simultaneous measurements of particles, fields, and waves has never been performed. We consider a spinning spacecraft of a wet mass of 76.1 kg with a 9.7 kg payload, which can “hitchhike” on another platform until Mars orbit insertion, and then be released into a suitable orbit. The spacecraft design is based on the experience gained in very successful Swedish space plasma missions, Viking, Freja, Astrid-1, and Astrid-2. In the present mission design, the MOPS spacecraft is equipped with its own 1m high gain antenna for direct communication with the Earth. The payload includes a wave experiment with wire booms, magnetometer with a rigid boom, Langmuir probes, electron and ion energy spectrometers and an ion mass analyzer. An energetic neutral atom imager and an UV photometer may complete the core payload. One of the proposed scenarios is piggy - backing on the Russian Phobos - Grunt mission to be launched to Mars in 2011. QC 20120321