Kumi Nitta

Flashover Discharge on Solar Arrays: Analysis of Discharge Current and Image

Electrostatic discharge testswere performed on large solar arraypanels under the simulated plasma environments of a geostationary orbit and a low Earth orbit to investigate the propagation length and velocity of flashover plasma. To investigate the propagation length, the neutralized current on the strings was also examined. The neutralized charge valuedue toflashover plasmawas found to decreasewith distance. Propagation lengthwas limited under both the geostationary orbit environment and the low-Earth-orbit environment. Visual investigation of the velocity of flashover plasma clarified that velocity decreases with time. The initial velocity of flashover plasma measured was several tens of km=s, regardless of orbital environment conditions.

Secondary Electron Emission Measurement of Insulating Materials for Spacecraft

We studied how to measure the secondary electron emission (SEE) of metal and insulating materials used for satellite thermal insulation or other such purposes. SEE yield measurement is very important for analyzing charge accumulation on the satellite surfaces due to the space environment because electron emission due to irradiated electrons influences the amount of surface charge. Therefore, we tried to measure the SEE yield. To measure SEE, we used an improved SEM system for SEE measurement that has a beam blanking unit and a Faraday cup. From this system, we can obtain the characteristics of the SEE yield from insulation materials irradiated by an electron beam with an energy of 600eV to 5keV. In this report, we introduce the SEE yield measurement results of reference materials (Au, Ag and Quartz glass) and insulating materials. From those results, we discuss the characteristics of SEE that depend on each material. Furthermore, we also propose a future plan of SEE measurement for satellite materials.

Measurement of surface and volume resistivity for alumina ceramics under vacuum condition

This paper reported the surface and volume resistivity of typical insulators under atmospheric condition and vacuum condition. The measured materials are some kinds of alumina ceramics which have different purity of Al2O3 component. It was confirmed that the surface resistivity for almost all of the insulator materials under vacuum condition was higher than that under atmospheric condition. In addition, we checked the dependence of surface resistivity on ambient pressure from the atmospheric condition to the medium vacuum condition. Desorption of moisture vapor from the insulator surface would be the main cause of the increase of the surface resistivity in vacuum. On the other hand, the volume resistivity had little change between vacuum and atmospheric condition.

Influence of atomic oxygen irradiation on secondary electron emission yield of polyimide films

We studied the measurement of secondary electron emission (SEE) of metal and insulating materials used for satellite thermal insulation or other such purposes. The SEE yield measurement is very important for analyzing charge accumulation on satellite surfaces in a space environment because electron emission related to irradiated electrons influences the amount of surface charge. We considered degradation phenomena of surface materials for spacecraft caused by radioactive rays. Those SEE yields might change for a nondegradation sample. We measured the SEE yields of surface materials for spacecraft that are treated using the degradation process. In preparation of the degradation sample, the samples were irradiated by atomic oxygen (AO) to simulate degradation in a space environment. We take three irradiation conditions and two irradiation methods related to a GEO orbit and operating period. This report introduces the measurement results of the reference material: polyimide films. We discuss the relationship between the SEE yields and sample degradation when irradiated by atomic oxygen. Furthermore, we consider the effect of different AO irradiation methods: the laser detonation method and the plasma asher method.

Secondary electron emission on degradation sample and development of new measurement system with low electron energy

We studied measurement of secondary electron emission (SEE) of metal and insulating materials used for satellite thermal insulation or other such purposes. The SEE yield measurement is very important for analyzing charge accumulation on satellite surfaces for a space environment because electron emission related to irradiated electrons influences the amount of surface charge. Therefore, we tried to measure the SEE yield. Furthermore, we must consider degradation phenomena of surface materials for spacecraft caused by radioactive rays. According to the degradation of materials, those SEE yields might change compared to a non-degradation sample. Therefore, we tried to measure the SEE yields of surface materials for spacecraft which are treated using the degradation process. For preparing a degradation sample, those samples were irradiated by an electron beam and UV to simulate degradation in a space environment. We take three irradiation conditions for electron beam and UV irradiation that related with GEO and operating period. This report introduce a few results of the SEE yield of the satellite materials applied degradation process simulated space environment and discuss the relationship between the SEE yields and sample degradation when irradiated by an e-beam and UV. Furthermore, we also introduce the new SEE measurement system which can irradiated electron with an energy under 0.6 keV.

Secondary Electron Emission as a Measure of Sample Degradation Irradiated with Electrons and UV

We studied measurement of secondary electron emission (SEE) of metal and insulating materials used for satellite thermal insulation or other such purposes. The SEE yield measurement is very important for analyzing charge accumulation on satellite surfaces for a space environment because electron emission related to irradiated electrons influences the amount of surface charge. Therefore, we tried to measure the SEE yield. Furthermore, we must consider degradation phenomena of surface materials for spacecraft caused by radioactive rays. According to the degradation of materials, those SEE yields might change compared to a non‐degradation sample. Therefore, we tried to measure the SEE yields of surface materials for spacecraft which are treated using the degradation process. For preparing a degradation sample, those samples were irradiated by an electron beam and UV to simulate degradation in a space environment. We take three irradiation conditions for electron beam and UV irradiation that related with GEO ...

A measurement of light intensity and quantum yield in photoelectron emission from satellite surface materials in the 30–250-nm range

We studied the measurement of photoelectron emission (PE) of metal and insulating materials used for thermal insulation on satellites or other such purposes. The PE measurement is very important for analyzing charge accumulation on satellite surfaces in a space environment because photoelectron emission is related to the amount of surface charge. Based on these photoemission characteristics, we deduce that the risk of electrostatic discharge for a satellite in the day position is lower than that in the night position.

Material Property Measurements Related to Engineering Design Optimization Guidelines and Spacecraft Charging

This paper describes the study framework for material property measurements related to spacecraft charging, methods, and measurement results. This work specifically addresses analyses and measurements of surface resistivity, volume resistivity, and the dielectric constant. We also explain measurements of secondary electron and photoelectron emissions in this framework.This review is based on joint experimental studies conducted for the Japan Aerospace Exploration Agency (JAXA) at the High Energy Accelerator Research Organization (KEK), at the Musashi Institute of Technology and at the Saitama University to investigate the relation to spacecraft charging. This report introduces a summary of some typical measurement results following a brief explanation of the measurement project.

Measurement of Photoelectron Emission Using Vacuum Ultraviolet Ray Irradiation

Satellites have come to play many roles depending on their purpose, including communication, weather observation, astronomy observation, and space development. A satellite requires long life and high reliability in such a situation. However, at an altitude of several hundred kilometers, atomic oxygen (AO) is a destructive factor. With density of about 1015 atoms/m3, AO also has high reactivity. As the satellite collides with AO, surface materials of the satellite are degraded, engendering surface roughness and oxidation. Accordingly, it is necessary to monitor the surface conditions.In this study, photoemission characteristics of several materials, such as metals, glasses, and polymers are measured using a deuterium lamp and band pass filters. The threshold energy for photoemission and the quantum efficiency were evaluated from those measurements. Consequently, for the investigated materials the threshold energies for photoelectron emission were found to be 4.9–5.7 eV. The quantum efficiency of metals is ...

Effect of low temperature on threshold voltage for solar panel ESD ground tests

Solar panel failure is putatively caused by electrostatic charge and discharge. An investigation of its causes and efforts to determine measures for the future require both verification under as realistic a space environment as possible and enhanced ground tests. A plasma chamber was developed at the Tsukuba Space Center to carry out charge/discharge tests to verify low-Earth-orbit satellites solar panel durability against electrostatic discharge (ESD). This paper describes results of solar panel ESD tests at extremely low temperatures. The primary arc inception threshold voltages at 160 K and 230 K were similar at room temperature. In contrast, the rate of primary arc inception of 230 K was five times and the rate of primary arc inception of 160 K was ten times as much as that at 300 K at applied voltage 200 V. We also measured the capacitance C and dielectric constant epsivtau of the cover glass, which shows high resistivity and which is fairly constant over many frequencies. Apparently, the dielectric constant values have a slight influence on the rate of primary arc inception.