Abstract
Abstract MAP-PACE (MAgnetic field and Plasma experiment-Plasma energy Angle and Composition Experiment) is one of the scientific instruments onboard the SELENE (SELenological and ENgineering Explorer) satellite. PACE consists of four sensors: ESA (Electron Spectrum Analyzer)-S1, ESA-S2, IMA (Ion Mass Analyzer), and IEA (Ion Energy Analyzer). ESA-S1 and S2 measure the distribution function of low-energy electrons below 15 keV, while IMA and IEA measure the distribution function of low energy ions below 28 keV/q. Each sensor has a hemispherical field of view. Since SELENE is a three-axis stabilized spacecraft, a pair of electron sensors (ESA-S1 and S2) and a pair of ion sensors (IMA and IEA) are necessary for obtaining a three-dimensional distribution function of electrons and ions. The scientific objectives of PACE are (1) to measure the ions sputtered from the lunar surface and the lunar atmosphere, (2) to measure the magnetic anomaly on the lunar surface using two ESAs and a magnetometer onboard SELENE simultaneously as an electron reflectometer, (3) to resolve the Moon-solar wind interaction, (4) to resolve the Moon-Earth’s magnetosphere interaction, and (5) to observe the Earth’s magnetotail.
Highlights
Low-energy charged particles around the Moon were vigorously observed by Moon orbiting satellites and plasma instrumentation placed on the lunar surface in 1960s and 1970s (Lyon et al, 1967; Colburn et al, 1967; Anderson et al, 1972; Howe et al, 1974; Neugebauer et al, 1972; Clay et al, 1972; Hills et al, 1972)
Except the low-energy electron measurement by Lunar Prospector (Binder, 1998), the lunar wake plasma data obtained by WIND during its Moon fly-by (Ogilvie et al, 1996), and reports on remote detection of the lunar ions (Hilchenbach et al, 1993; Mall et al, 1998; Futaana et al, 2003) and lunar electrons (Futaana et al, 2001) there has been almost no new information about the low-energy charged particles around the Moon
The solar wind electrons and the magnetotail electrons that reach the Moon will be absorbed if there is no magnetic field on the lunar surface
Summary
Low-energy charged particles around the Moon were vigorously observed by Moon orbiting satellites and plasma instrumentation placed on the lunar surface in 1960s and 1970s (Lyon et al, 1967; Colburn et al, 1967; Anderson et al, 1972; Howe et al, 1974; Neugebauer et al, 1972; Clay et al, 1972; Hills et al, 1972). The solar wind electrons and the magnetotail electrons that reach the Moon will be absorbed if there is no magnetic field on the lunar surface. The PACE-ESA sensors, due to the 90◦ orbit inclination of the SELENE main orbiter, will survey the remnant magnetic field on almost all the lunar surface with higher spatial resolution than previous electron reflectometer measurements. The start electrons are accelerated by the electric field inside the mass analyzer and their positions are detected by one-dimensional circular resistive anode that is placed behind the MCP. The time-of-flight section of IMA acts as the so-called “isochronous time-offlight” With this design of LEF-TOF mass spectrometer, the center anode detects both neutrals (direct time-of-flight) and secondary electrons from the top part of the mass analyzer, generated by ions (isochronous time-of-flight). Energy range Energy resolution Energy sweep step Mass range Mass resolution Field of view FOV sweep range Angular resolution g-factor (5◦×22.5◦) (efficiency is not included) Time resolution Analyzer type
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