Index: piggy-back satellite for aurora observation and technology demonstration

This paper describes outline of the piggy-back satellite “INDEX” for demonstration of advanced satellite technologies as well as for observation of fine structure of aurora. Aurora observation will be carried out by three cameras(MAC) with a monochromatic UV filter. Electron and ion spectrum analyzer (ESA/ISA) will measure the particle phenomena together with the aurora imaging. INDEX satellite will be launched in 2002 by Japanese H2-A. The satellite is mainly controlled by the high-speed, fault-tolerant on-board RICS processor (three-voting system of SH-3). The attitude control is a compact system of three-axis stabilization. Although the size of INDEX is small (50Kg class), several newly-developed technologies are applied to the satellite system, including silicon-on-insulator devices, variable emittance radiator, solar-concentrated paddles, lithium-ion battery, and GPS receiver with all-sky antenna-coverage.     

A noise attenuation method for medium-energy electron measurements in the radiation belt

From the viewpoint of plasma particle measurements in the radiation belt, background noise is a serious problem. High-energy particles penetrating the sensor shielding generate spurious signals, and their count rate often can be comparable to the true signals. In order to attenuate such background noise during medium-energy (5–83 keV) electron measurements, we propose the double energy analyses (DEA) method. DEA is conducted by a combination of an electrostatic analyser (ESA) and avalanche photo-diodes (APDs); ESA and APD independently determine the energy of each incoming particle. By using the DEA method, therefore, the penetrating particles can be rejected when the two energy determinations are inconsistent; spurious noise are caused only when the deposited energy at an APD is by chance consistent with the measured energy by ESA. We formulate the noise count rate and show the advantage of DEA method quantitatively.     

Processes leading to plasma losses into the high-latitude atmosphere

Space Science Reviews -     

In-flight Performance and Initial Results of Plasma Energy Angle and Composition Experiment (PACE) on SELENE (Kaguya)

MAP-PACE (MAgnetic field and Plasma experiment—Plasma energy Angle and Composition Experiment) on SELENE (Kaguya) has completed its ～1.5-year observation of low-energy charged particles around the Moon. MAP-PACE consists of 4 sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measured the distribution function of low-energy electrons in the energy range 6 eV–9 keV and 9 eV–16 keV, respectively. IMA and IEA measured the distribution function of low-energy ions in the energy ranges 7 eV/q–28 keV/q and 7 eV/q–29 keV/q. All the sensors performed quite well as expected from the laboratory experiment carried out before launch. Since each sensor has a hemispherical field of view, two electron sensors and two ion sensors installed on the spacecraft panels opposite each other could cover the full 3-dimensional phase space of low-energy electrons and ions. One of the ion sensors IMA is an energy mass spectrometer. IMA measured mass-specific ion energy spectra that have never before been obtained at a 100 km altitude polar orbit around the Moon. The newly observed data show characteristic ion populations around the Moon. Besides the solar wind, MAP-PACE-IMA found four clearly distinguishable ion populations on the dayside of the Moon: (1) Solar wind protons backscattered at the lunar surface, (2) Solar wind protons reflected by magnetic anomalies on the lunar surface, (3) Reflected/backscattered protons picked-up by the solar wind, and (4) Ions originating from the lunar surface/lunar exosphere.