Takanobu Muranaka

Development of Multi-Utility Spacecraft Charging Analysis Tool (MUSCAT)

A new numerical software package to analyze spacecraft charging, named ldquomulti-utility spacecraft charging analysis toolrdquo (MUSCAT), has been developed. MUSCAT consists of an integrated graphical user interface tool called ldquoVineyardrdquo 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.

ESD Ground Test of Solar Array Coupons for a Greenhouse Gases Observing Satellite in PEO

An electrostatic discharge test was carried out on a solar array paddle (SAP) for the Greenhouse gases Observing SATellite (GOSAT) on a simulated polar Earth orbit (PEO) environment. To simulate the spacecraft charging conditions in a PEO with an auroral band, when electrons with higher energy than LEO plasma flow to the Earth, three conditions of dielectric charging can be considered on each side of the SAP. At first, the threshold voltage differences of discharge inception were measured experimentally using solar array coupons simulating both the beginning and the end of life under six charging conditions. Next, the Multiutility Spacecraft Charging Analysis Tool was employed to analyze the spacecraft surface potential and the time needed for charging. From the threshold value and the charging analysis, the probability and the number of discharges were estimated in each charging condition during a lifetime of the GOSAT. Finally, the performance of the coupons against discharges was evaluated for each charging condition. All coupons had no sustained arc during these tests; however, there was some electrical degradation of the solar cell. The power degradation during the lifetime of the GOSAT was estimated from these results, and the design of the solar array coupon was confirmed to satisfy the power demand even if the estimated number of discharges occurs in the lifetime.

Verification of Multi-Utility Spacecraft Charging Analysis Tool (MUSCAT) via laboratory test

Multi-utility Spacecraft Charging Analysis Tool (MUSCAT), a spacecraft charging analysis software, has been developed as a joint work of JAXA and KIT. Experiments for the fundamental code validation were carried out at the plasma chamber of LaSEINE in KIT to show accuracy of the solver. We evaluated that the test section in the chamber with respect to the plasma environment by measuring two-dimensional plasma distribution and plasma drift velocity. A cube area of 400mm on a side whose center located at the 550mm downstream from plasma source can be considered as the test section with no plasma flow. The averaged plasma density, temperature and plasma potential within this test section were 3±2x10 12 m -3 , 2±1eV and 10±5V, respectively. The length of test section 400mm corresponds to about 67λ D . Spatial distribution of electric potential and IV characteristic curve were measured with an emissive probe and the Langmuir probe whose electrode were cubic in shape to adjust the rectangular numerical domain of MUSCAT. Comparing those experimental results with the numerical ones, both had good agreements. These results show that the physical functions of MUSCAT simulate charging processes quite well. Also, numerical model of the cell-side of solar array paddle was obtained. Conductor patches whose size is the quarter of total amount of the interconnector exposed area put on the coverglass can simulate the cell-side of a real solar array with respect to current collection.

Recent Progress of Development of Multi -Utility Spacecraft Charging Analysis Tool (MUSCAT)

A new numerical software package to analyze spacecraft charging, named ldquomulti-utility spacecraft charging analysis toolrdquo (MUSCAT), has been developed. MUSCAT consists of an integrated graphical user interface tool called ldquoVineyardrdquo 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.

Numerical Analysis of Active Spacecraft Charging in the Geostationary Environment

This paper treats the electric-potential characteristics of active spacecraft charging using a full particle-in-cell simulation. A new active spacecraft charging model that considers the velocity distribution of beam particles is proposed. The electric potential of active charging can be calculated numerically and quickly using the new model; by contrast, the conventional model can only express active charging qualitatively, and particle-in-cell simulations require a very high load. The numerical solution of the new model shows very good agreement with the results of the full particle-in-cell simulation for a cubic spacecraft model with electron beam emission.

Estimation of Electrostatic Force on Solar Sail IKAROS in Solar Wind Plasma

We have numerically analyzed the electrostatic force on the solar sail IKAROS in solar wind plasmas at 1.0 AU. We estimated the electrostatic force quantitatively to understand if the force could affect the thrust of the solar sail generated by the solar radiation pressure. The estimation was made by Maxwell stress tensor method from the electric field on the spacecraft obtained by the charging analysis of the spacecraft. A 3-D electrostatic fullParticle-In-Cell code was used in order to study precise charged particle distributions and the space charge effects on the electrostatic potential around the solar sail. MUSCAT, a spacecraft charging analysis tool, was used to determine the differential voltage of the spacecraft. According to the numerical analysis, highest absolute value of the electric field was recognized on the edge of the back insulator surface of the membrane constituting the spacecraft. The maximum magnitude of the electrostatic tension on the surface was 1.0x10 -8 Pa, which corresponds to 1% of the magnitude of the solar radiation pressure under the solar wind environment considered.