11:30 AM - 11:45 AM
[PCG18-04] Performance test for calibration of ion energy mass spectrum analyzer onboard the Martian Moons eXploration (MMX) spacecraft
Keywords:Mass spectrometry, Solar system exploration, Mars, Phobos, Ion analyzer
The ion energy mass spectrum analyzer will conduct in-situ observations of ions around Mars and Phobos as part of the Martian Moons eXploration (MMX) mission. The MMX mission is a sample return project planned by the Japan Aerospace Exploration Agency (JAXA) to investigate the origin of the Martian moons and physical processes in the Martian environment. The ion analyzer is a component of the mass spectrum analyzer (MSA), along with the two magnetometers, which measures distribution functions and mass distributions of low-energy (< ~10s keV) ions. The MSA will measure ions emitted from Phobos and its torus as well as escaping ions from the Martian atmosphere with monitoring the solar wind to address the MMX science goals.
The ion analyzer employs nearly the same measurement techniques as that of Ion energy Mass Analyzer (IMA) for the Kaguya mission and mass spectrum analyzer (MSA) for BepiColombo/MIO. The ion analyzer is cylindrically symmetric in shape and consists of an energy analyzer and a mass analyzer (see the figure). The aperture of 360 degrees near the sensor top and neighboring angular scanning deflectors provide a 2-pi steradian field-of-view (FOV). The two angular scanning deflectors are alternately applied with a sweeping high voltage up to +5 kV for such a wide FOV. The energy analyzer measures energy/charge using a top-hat electrostatic method in which the inner spherical electrode is applied with a sweeping negative high voltage. In the mass analyzer, mass/charge is measured by a time-of-flight (TOF) method that uses a linear-electric field (LEF) for the higher mass resolution. At the entrance of the mass analyzer, ultra-thin carbon foil is mounted on a metal grid to emit secondary electrons for start signals. The TOF chamber is longer than that of the previous analyzers and is optimized to achieve a high mass resolution (m/dm~100). The top end of the TOF chamber are supplied with static high voltage of -12 kV for a post-acceleration of incident ions. The incident ions are detected by a micro-channel plate (MCP) assembly at the bottom as stop signals if they are neutralized by the carbon foil. In the other case, the incident ions pass through the carbon foil as ions and then are reflected by the LEF, resulting in ejection of secondary electrons at the ceiling of the TOF chamber. The secondary electrons are attracted by the LEF and are also detected by the MCP assembly as stop signals. The MCP assembly has a circular delay line anode to obtain the start signal and 360-degree-position information from the detection of the secondary electrons emitted from the carbon foil.
The MSA is now being developed to contribute to the MMX scientific objectives. The Critical Design Review (CDR) was completed last fall and we have conducted a performance test with a flight model (FM) of the ion analyzer for pre-flight calibration. We present the results of the FM performance tests and the current status of the development.
The ion analyzer employs nearly the same measurement techniques as that of Ion energy Mass Analyzer (IMA) for the Kaguya mission and mass spectrum analyzer (MSA) for BepiColombo/MIO. The ion analyzer is cylindrically symmetric in shape and consists of an energy analyzer and a mass analyzer (see the figure). The aperture of 360 degrees near the sensor top and neighboring angular scanning deflectors provide a 2-pi steradian field-of-view (FOV). The two angular scanning deflectors are alternately applied with a sweeping high voltage up to +5 kV for such a wide FOV. The energy analyzer measures energy/charge using a top-hat electrostatic method in which the inner spherical electrode is applied with a sweeping negative high voltage. In the mass analyzer, mass/charge is measured by a time-of-flight (TOF) method that uses a linear-electric field (LEF) for the higher mass resolution. At the entrance of the mass analyzer, ultra-thin carbon foil is mounted on a metal grid to emit secondary electrons for start signals. The TOF chamber is longer than that of the previous analyzers and is optimized to achieve a high mass resolution (m/dm~100). The top end of the TOF chamber are supplied with static high voltage of -12 kV for a post-acceleration of incident ions. The incident ions are detected by a micro-channel plate (MCP) assembly at the bottom as stop signals if they are neutralized by the carbon foil. In the other case, the incident ions pass through the carbon foil as ions and then are reflected by the LEF, resulting in ejection of secondary electrons at the ceiling of the TOF chamber. The secondary electrons are attracted by the LEF and are also detected by the MCP assembly as stop signals. The MCP assembly has a circular delay line anode to obtain the start signal and 360-degree-position information from the detection of the secondary electrons emitted from the carbon foil.
The MSA is now being developed to contribute to the MMX scientific objectives. The Critical Design Review (CDR) was completed last fall and we have conducted a performance test with a flight model (FM) of the ion analyzer for pre-flight calibration. We present the results of the FM performance tests and the current status of the development.