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The anomaly of Japanese satellite ADEOS-2 (ADvanced Earth Observing Satellite-2: Midori-2) appeared in 2003 is supposed to be caused by arcing discharges initiated due to ESD (ElectroStatic Discharge) in the bundled wire-harnesses of the solar paddle. In order to make the conditions of the occurrence of the discharge clear, it is necessary to evaluate the arcing discharge characteristics in vacuum quantitatively. Therefore we tried to investigate the characteristics of arcing discharges between two exposed conductors consisting of a pair of insulating wires for space use. The discharges were triggered by ESD released from a capacitor. These characteristics were obtained as parameters of the amplitude of ESD, the pressure in the chamber, the direction of the current flowing the conductor and so on. We obtained the result that the arcing discharge time increased with the amplitude of the ESD and the time is affected by the magnetic field formed between the conductors by the current flowing the conductor itself., 資料番号: AA0063965012

Diagnosis of space triple junction solar cells using ElectroLuminescence (EL) and PhotoLuminescence (PL) imaging techniques are demonstrated. Solar cells, which are essential satellites components, can be damaged easily because of their thin structure. Damaged cells are difficult to diagnose because the generating process is not visible. Evaluation of solar cells mostly depends on current and voltage (IV) characteristics. However, IV characteristics give little information other than the cells are damaged or not. A Triple Junction (TJ) solar cell, which has a complex structure consisting of three thin solar cells (subcells) stacking up with a thickness of 150 mu m, is even more difficult to evaluate. We have developed a diagnostic imaging technique employing EL and PL for analyzing semiconductor devices including solar cells. EL is light emission from solar cells under the forward bias condition as LEDs (Light Emitting Diodes). A TJ cell can be regarded as three diodes connected in series. PL is light emission from solar cells illuminated. When a solar cell is illuminated by light with energy larger than the bandgap, excess careers are generated. If the careers recombine radiatively, PL emission can be observed. When we perform EL and PL imaging, we use a cooled CCD (Charge Coupled Device) camera to detect the light emission and band-pass filters to select the appropriate wavelength from the respective subcell. This technique allows us to diagnose each subcell noncontact and nondestructively. TJ cells damaged after thermal cycling test and ElectroStatic Discharge (ESD) test were examined using EL and PL imaging technique as well as IV characteristics measurement. The thermal cycling test was performed in the range of -180 C to +180 C for 558 cycles. IV characteristics of a TJ cell after the test suggested only the existence of a current leakage but the location or the condition of the leakage point. In the EL and PL images of the cell, dark areas appeared and we could locate where the current leakage point was. In the EL images, dark areas tend to a form long and narrow shape affected by the grid electrodes, because the excess careers are injected through them. In the PL images, dark areas tend to form circular shape, because the excess careers are generated by the uniform light emission over the cell. A microscope photograph of the current leakage point, which was located by the EL and PL images, revealed micro cracks of about 10 micrometer. They seemed to be the cause of the current leakage. The ESD test was performed in a simulated LEO (Low Earth Orbit) plasma environment. Many flashovers were observed when the voltage between the strings equaled to 320 V and some cells were damaged severely. IV characteristics of one of the damaged cells suggested the existence of a current leakage again. So many discharge craters were left around the cells that which crater caused the current leakage was hard to tell. In the EL image of the cell, two neighboring current leakage points were located at a corner. In the PL image, an dark area was observed at the respective corner, but it was too large to distinguish the two points. A microscopic photograph showed two discharge craters where a portion of the cell was blown off. In both cases, IV characteristics suggests the cell is damaged but not showed which part of the cell was deteriorated. EL and PL images clearly located it., 資料番号: AA0063965008

The spacecraft like a communication or a broadcasting satellite flying in GEO (Geostationary Earth Orbit) is always exposed to plasma and/or radioactive-rays such as alpha-, beta- and gamma-rays. When the dielectric materials, in which the spacecraft is wrapped to keep temperature in it stable, are irradiated by the high energy electron beam, sometimes an unexpected accident due to an electrostatic discharge happens. The accident sometimes causes a serious mission error of the spacecraft. However, there remain many unknown factor about a charge accumulation in dielectric materials by irradiation of electron beam. Therefore, we need to measure the charge distribution in the bulk of dielectric materials. We have been developing a system for measuring such a charge distribution in dielectric materials using pressure wave propagation method. Using this system, we tried to measure the charge distribution under electron beam irradiated Low Density Polyethylene, Polyethylene Terephthalate, Polycarbonate, Polyethylene Naphthalate in addition to Polyimide and PTFE (PolyTetraFluoroEthylene) films which are used as a thermal control layer or a optical solar reflector of spacecrafts. We observed accumulation behavior of charge in each sample, survey relationship with each sample's molecular structure. As a result, It's believed that charging characteristics of insulating material is linked to benzene ring in each sample's molecular structure., 資料番号: AA0063997025, レポート番号: JAXA-SP-07-030

Spacecrafts flying in GEO (Geo-synchronous Earth Orbit) are always exposed to plasma and radioactive-rays such as alpha-, beta- or gamma-rays. Especially in GEO, dielectric materials are expected to be irradiated by high energy electron-beam. In the case of high energy electron beam irradiation, the electrons are injected into the bulk of dielectric materials and they accumulate in them. Because there are no basic data based on practical experiments, it is difficult to expect when and how an accident of ESD (Erector-Static Discharge) caused by accumulated charge will happen on spacecraft. Therefore, we need to measure the charge distribution in the bulk of dielectric materials. We have been developing a system for measuring such a charge distribution in dielectric materials using, so-called, PIPWP (Piezo-Induced Pressure Wave Propagation) method. However, the spatial resolution was low and it was difficult that the space charge distribution measurement in the material used with actual spacecrafts. To obtain a good experiment result, we must use the PEA (Pulsed Electro-Acoustic) method. It is necessary to develop a new PEA measurement system, for a real-time, continuous measurement to secure reliability while irradiating the sample. In this report, It introduces a small, real-time Space Charge Measurement System using PEA method., 資料番号: AA0063585030, レポート番号: JAXA-SP-06-035

application/pdf, In the case of the discharge from the pendent drop to the charged polymer surface, an electrostatically stressed liquid surface is distorted into a stable conical shape. This report presents the results of the electrostatic discharge between a pendent drop and the charged polymer surface. It was found that the multiple discharge appears only in the case of the positive charging polymer. This discharge depended on the conductivity or the surface tension of the sample water. It is considered that this multiple discharge is a kind of Trichel pulse corona.

宇宙エネルギーシンポジウム 宇宙航空研究開発機構 20080307 神奈川 日本, Space Energy Symposium Japan Aerospace Exploration Agency 20080307 Kanagawa Japan, 資料番号: AA0063965000