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The Multiutility Spacecraft Charging Analysis Tool (MUSCAT), a spacecraft charging analysis software, has been developed as a collaboration work between Japan Aerospace Exploration Agency and Kyushu Institute of Technology. Laboratory experiments for fundamental code validation were carried out in both facilities' plasma chambers. MUSCAT is a particle simulation code based on particle-in-cell (PIC) and particle tracking (PT) algorithms capable of calculating the floating-body potential of a spacecraft with respect to the plasma potential. Three experiments were carried out regarding spacecraft--plasma interaction phenomena important in LEO and PEO. A Langmuir probe was used to measure the current collection and potential distribution in static plasma to validate the PIC and PT schemes. The floating potential of an object in plasma with an energetic electron component was measured to validate the floating-body calculation as well as the PT scheme. Current collection and potential distribution in the wake structure were measured to validate the PIC and PT scheme in flowing plasma condition. The experimental results and the simulation results agreed very well in all the three experiments, validating the accuracy of the MUSCAT solver. Index Terms--Simulation software, spacecraft charging, wake plasma.

A new numerical software package to analyze spacecraft charging, named 'Multi-Utility Spacecraft Charging Analysis Tool' (MUSCAT), has been developed. MUSCAT consists of an integrated graphical user interface tool called 'Vineyard' and the solver. Vineyard enables satellite engineers to compute spacecraft charging with little knowledge of the numerical calculations. Functions include 3-D satellite modeling, parameter input such as material and orbit environment, data transfer, and visualization of numerical results. Fundamental physical processes of charged-particle--surface interaction are included in the solver. These functions enable MUSCAT to analyze spacecraft charging at geostationary orbit, low Earth orbit, and polar Earth orbit (PEO). The numerical solver code is parallelized for high-speed computation, and the algorithm is optimized to achieve analysis of large-scale PEO satellite in the design phase. Variable time steps are also used to calculate the rapid change of the spacecraft body potential and the gradual change of the differential voltage in a single simulation with a practical number of iterations. In this paper, the functionality, algorithms, and simulation examples of MUSCAT are presented. Index Terms--Simulation software, spacecraft charging.

A series of spacecraft charging analyses was carried out for large GEO satellites using Multi-Utility Spacecraft Charging Analysis Tool. The purpose was to derive the number of electrostatic discharges expected for 15 years in orbit, which would be used as the basis of the number of primary electrostatic discharges (ESDs) to be used in future solar cell coupon ESD tests. The combinations of GEO plasma parameters (electron density, proton density, electron energy, and proton energy) that have a high probability of occurrence have been identified first. For each of those plasma parameters, a charging analysis was done. In the simulation, the time for the differential voltage between solar array cover glass and the spacecraft chassis to reach the ESD inception threshold was calculated. The results indicate that, for a typical GEO satellite, the expected number of ESDs in 15 years is on the order of 10 000, agreeing well with the previous work where another satellite was simulated by NASCAP/GEO. [ABSTRACT FROM AUTHOR]

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