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Frequent satellite failures due to charging and arcing on solar array surface, there are strong demands for more thorough ElectroStatic Discharge (ESD) ground test before the launch. It is necessary to validate that a given solar array design can withstand repeated arcing in space before the launch. Test conditions, however, differ among countries, as there is no international standard to define the conditions. An international research project started in 2005 to establish International Standard Organization (ISO) standard on ESD test. In the first year, test coupons of the international round robin tests were produced and the preliminary experiments were carried out. In September 2006, the team members gathered at ONERA, Toulouse France. Demonstration experiments were carried out and in-depth discussion was done regarding the preliminary test results of KIT (Kyushu Institute of Technology). In November 2006, the First International Workshop on ISO Standardization of Electrostatic Discharge Test of Satellite Solar Array was held in Kitakyushu. The first version of the working draft of ISO document was discussed in the workshop and the participants agreed to seek the ISO standard by as early as Fall 2008., 資料番号: AA0063585003, レポート番号: JAXA-SP-06-035

The Advanced Land Observing Satellite that was launched by the Japan Aerospace Exploration Agency in 2006 carries a large solar-array paddle of 22 times 3 m in polar orbit. The wake side of the solar paddle can be charged to a negative value exceeding -1000 V. Numerical simulations and laboratory experiments are carried out to investigate charging and arcing phenomena on the backside of the solar paddle that has exposed bypass diode boards and silver-Teflon thermal film. Possibility of secondary arc and surge voltage between hot and return ends of power circuit has been investigated. The authors irradiate solar-panel coupons with an electron beam to simulate charging situation near the North Pole. Surface flashover is observed once the insulator potential exceeds -7000 V. The authors have also tested charging situation near the South Pole where carbon fiber-reinforced plastics surface facing dense ionospheric plasma may arc easily once a satellite potential drops to -80 or -90 V. The solar-paddle design has been modified to increase the safety margin against arcing, and tests have been carried out to identify the strength limit under extremely harsh test environment.

The conventional wisdom about solar array arcing in LEO is that only the parts of the solar array that are swept over by the arc-generated plasma front are discharged in the initial arc. This limits the amount of energy that can be discharged. Recent work done at the NASA Glenn Research Center has shown that this idea is mistaken. In fact the capacitance of the entire solar array may be discharged, which for large arrays leads to very large and possibly debilitating arcs, even if no sustained arc occurs. We present the laboratory work that conclusively demonstrates this fact by using a grounded plate that prevents the arc-plasma front from reaching certain array strings. Finally, we discuss the dependence of arc strength and arc pulse width on the capacitance that is discharged, and provide a physical mechanism for discharge of the entire array, even when parts of the array are not accessible to the arc plasma front. Mitigation techniques are also presented., 資料番号: AA0049206006, レポート番号: JAXA-SP-05-001E

Advanced Land Observing Satellite (ALOS) that will be launched by Japanese Aerospace Exploration Agency in 2005 will carry a large solar paddle of 22 m x 3 m in polar orbit. The wake side of solar paddle can be charged to a highly negative value. Laboratory experiments are carried out to investigate charging and arcing phenomena on the backside of the solar paddle that has exposed bypath diode boards and Silver-Teflon thermal coating. We irradiate solar panel coupons with an electron beam to simulate charging situation near the North Pole. Surface flashover is observed once the insulator potential exceeds - 7 kV. Possibility of sustained arc and surge voltage between hot and return ends of power circuit have been investigated., 資料番号: AA0049206098, レポート番号: JAXA-SP-05-001E

When we operate solar array at high voltage (greater than 100 V) in LEO environment, arcing occurs on the solar array surface. The solar cell can suffer degradation of electric performance due to only one arc with some probability. We performed degradation test of solar array coupons against arcing under simulated LEO environment in order to identify the threshold of arc energy to cause the solar cell degradation. The solar array coupons are made of silicon solar cells. The LCR circuit was attached to a solar array coupon through a vacuum chamber. In order to change trigger arc energy, we changed the value of capacitance of LCR circuit. The electric performance was measured inside the chamber without opening the chamber. The threshold of arc energy was identified. The arcing which has enough energy to cause the solar cell degradation may occur on solar array of 100 V satellite in Low Earth Orbit environment., 資料番号: AA0049206027, レポート番号: JAXA-SP-05-001E

The detrimental effects of spacecraft charging are well known, particularly when the charging leads to arcing on solar array and consequently to permanent power loss. Motivated by these concerns, ALCATEL SPACE has undertaken several test campaigns to qualify solar array design and to investigate margins. This paper describes the state-of-the-art of ALCATEL SPACE solar array ESD laboratory test set-up and procedure. The primary discharges are created using a plasma source and a negative polarization of the sample rear side. The required power to feed the arc can be delivered by a Solar Array Simulator with low capacitance power sources. The test sample is fully representative of a flight model., 資料番号: AA0049206045, レポート番号: JAXA-SP-05-001E

Experiments simulating charging on a geostationary orbit were done in laboratory on a large solar array coupon (592 x 1,333 mm) in order to characterize electrostatic discharges. Such discharges were triggered by inverted voltage gradient situation produced on the coupon biased at - 5,000V by using an electron beam striking the sample. Current probes monitored blow-off and flashover currents produced by electrostatic discharges and showed that almost all the energy stored on the cover-glasses can participate to the flashover discharge. Surface potential measurements performed before and after electrostatic discharges, show neutralization area where the differential voltage between the cover glass surface and the coupon decreased from + 1,000 V to + 200 V. The size of the neutralization zone varied with the discharges: while some discharges produce neutralization on a limited surface, other can produce neutralization all over the coupon., 資料番号: AA0049206042, レポート番号: JAXA-SP-05-001E

In 2003, Dr. A. R. Frederickson initiated a program to recast and combine the primary guides for mitigating the effects of spacecraft charging. That effort had the ambitious goal of taking the existing NASA guidelines for preventing surface electrostatic charging, NASA-TP-2361 (Purvis et al., 1984), and internal electrostatic charging, NASA-HDBK 4002 (Whittlesey, 1998), and bringing them up to date with recent laboratory and on-orbit findings. With the death of Dr. Frederickson in 2004, that study devolved to the principle authors to complete. This paper will describe the status of those on-going efforts to combine and update the two guidelines with emphasis on the proposed contents and on the differences and similarities between surface and internal charging mitigation techniques. It is planned to have a draft revision ready for review by the spacecraft charging community by the fall of 2005, with 2006 dedicated to implementing reviewers' comments and additions leading to a new, officially approved NASA guideline by the fall of 2006., 資料番号: AA0049206047, レポート番号: JAXA-SP-05-001E

This article presents the summary of the tests performed in the frame of an ESA contract EMAGS2. While EMAGS1 concentrated its efforts on basic understanding of Electrostatic Discharge Phenomenon, EMAGS2 mainly consisted in different tests which aimed at: comparing the characteristics of the secondary arcs obtained in an electronic charging environment with those triggered in a plasma environment (inverted voltage gradient conditions in both cases) (tests in plasma gave results representative of those obtained in electron when the energy of the primary discharge was equivalent); assessing the secondary arc triggering sensitivity to materials. Current/voltage thresholds for self-sustained arc have then been determined for different Si and GaAs solar array samples (lower thresholds on GaAs); assessing the influence of the intercells gap width with regard to secondary arcs (higher secondary arc and permanent arc thresholds for large gaps); and determining the effect on solar cells of repetitive primary discharges and non-permanent secondary arcs has been studied (no impact for repetitive primary discharges and secondary arcs with low duration)., 資料番号: AA0049206043, レポート番号: JAXA-SP-05-001E

As the power level of Geostationary satellites increases, there is more demand of careful ground test on solar array insulation strength. International atmosphere surrounding commercial telecommunication satellites calls for common international standard on test conditions. In this paper, we review ESD tests of solar array carried out in recent years at Kyushu Institute of Technology jointly with the Japan Aerospace Exploration Agency. The purpose of this paper is to describe the test conditions with the reasons of selecting those conditions and how we certified the insulation strength of given solar array designs against electrostatic discharges in orbit. The paper is aimed to stimulate discussion among experts on the issue of international standardization of solar array ESD test., 資料番号: AA0049206046, レポート番号: JAXA-SP-05-001E

When solar array is operated at a high voltage, arcs occur on the array surface. Our task is to examine the effects of conductive current generated by arcing on solar array circuit of spacecraft. First, equivalent circuits of small solar array module are modeled. The equivalent circuits are made for various types of solar cell such as silicon, gallium arsenic (hetero junction), and triple junction cells, etc. The equivalent circuit is composed of current source, diode, resistance, inductance and capacitance. First, we measured the frequency characteristic and I-V characteristic of a given solar array, and modeled the equivalent circuit to have the same characteristics by electronic circuit simulation software (SPICE). Next, an electric equivalent circuit of the arc inception was made, and was compared with the ground test result. We simulated the transient current and surge voltage resulted from the ground test using the equivalent circuit. The circuit is under adjustment to experimental results at present. We plan to add the effect of arc expansion to the circuit., 資料番号: AA0049120016

衛星帯電技術国際会議 宇宙航空研究開発機構 20050404-20050408 茨城 日本, Spacecraft Charging Technology Conference Japan Aerospace Exploration Agency 20050404-20050408 Ibaraki Japan, 資料番号: AA0049206000, レポート番号: JAXA-SP-05-001E