Teppei Okumura

Degradation of High-Voltage Solar Array Due to Arcing in Plasma Environment

A degradation test for a solar array coupon against electrostatic discharge was performed under a simulated lowEarth-orbit environment as part of research project to develop the next-generation 400-V high-voltage solar array technology. All tests were performed in a vacuum chamber with a plasma source. An inductance‐capacitance‐ resistance circuit was used to simulate the arc current that would flow by collecting electric charge stored on cover glasses. Arcs were repeated until the solar array coupon showed degradation of electrical output. The locations, current waveform, and voltage waveforms of all the arcs during the tests were recorded. The electrical output of the coupon was measured without opening the vacuum chamber. The arc that damaged a solar cell was identified; the cell was damaged by only one arc, which occurred at the edge of the cell.

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.

International Round-Robin Tests on Solar Cell Degradation Due to Electrostatic Discharge

Teppei Okumura∗ Japan Aerospace Exploration Agency, Tsukuba 305-8505, Japan Mengu Cho Kyushu Institute of Technology, Kitakyushu 804-8550, Japan Virginie Inguimbert ONERA, 31055 Toulouse, France Denis Payan Centre National d’Etudes Spatiales, 31401 Toulouse, France Boris Vayner Ohio Aerospace Institute, Cleveland, Ohio 44142 and Dale C. Ferguson∗∗ U.S. Air Force Research Laboratory, Albuquerque, New Mexico

Environmental Effects on Solar Array Electrostatic Discharge Current Waveforms and Test Results

A solar array electrostatic discharge ground test is necessary to assure spacecraft reliability in orbit. Laboratory experimentswere carried out to characterize an electrostatic discharge currentwaveformwith different background pressures and charging environments to identify the importance of the test setup. The waveform strongly depended on the background pressure. This difference can affect the result of the solar cell degradation test. However, in the case of the secondary arc test, the difference of the primary arc current waveform did not affect the duration of the secondary arc. The current available from a power supply mostly determined the duration of the secondary, irrespective of the test environment.Methods to control the primary arc current supplied by an external capacitance are proposed.

Influence of Power Supplies on the Secondary Arc Test of Solar Arrays

A secondary arc test is necessary to improve the design reliability of a solar array. To simulate the power generation of solar arrays, various power supplies are employed for the ground tests. Solar arrays that are illuminated by a light source are the most ideal power supply for the ground test in terms of their impedance. Laboratory experiments were carried out to investigate the appropriateness of a solar array simulator and a current regulative diode power supply for the secondary arc test. There was little difference among the waveforms and the secondary arc duration obtained by a real solar array, the solar array simulator, and the current regulative diode power supply, except the small difference in the rush current at the beginning of the secondary arc and the temporary blackout after the secondary arc. The solar array simulator and the current regulative diode power supply are both acceptable as a power supply for the secondary arc test. The minor difference is associated with the output capacitance of each power supply, which exists even for the real solar array.

Initial results from Primary Arc effects on solar cells at LEO (PASCAL) flight experiment

Repeated low power, or primary arcing, may adversely affect the performance of space solar cells. The cumulative effects of primary arcing on common solar cell performance parameters has been the subject of numerous ground studies in simulated plasma environments. The Primary Arc effects on Solar Cells At LEO (PASCAL) flight experiment is presently active aboard in the International Space Station (ISS) and characterizing such effects in-orbit for numerous state-of-the-art space solar cells with initial results presented herein.

Investigation on Space Environmental Degradation Effects of Solar Cell Coverglass

Based on the ground-based simulation for space irradiation environment, the degradation of CMG100-AR solar cell coverglasses produced by Qioptiq was conducted by thermal cycling at the range -160°C to +110°C, 50-keV protons irradiation, 500-keV electrons irradiation, ~ 4000 equivalent solar hours vacuum ultraviolet (UV) irradiation, and their multifactors radiation in sequence. The key parameter related to surface charging of virgin and degraded coverglasses, total electron emission yield (TEEY), was measured and discussed. The Monte Carlo simulation, infrared spectroscopy, UV-visible-near-infrared spectroscopy, and X-ray photoelectron spectroscopy spectrum were used to disclose the damage mechanism and its influence on TEEY.

Laboratory Test Campaign for ISO Standardization of Solar Array ESD Test Methods

An electrostatic discharge (ESD) on a solar array causes a serious damage for a satellite. The effective ground test is required to ensure a safety of the satellite. To establish the ground test method, an international project is being proceeding by Japan, Europe and US. In the project three types of test coupons are used for verification of plasma propagation, degradation of cell and occurrence of secondary arc, respectively. This paper introduces ESD test methods, experimental systems and experimental results in Kyushu Institute of Technology of Japan.

Temperature Effect on Primary Discharge Under Simulated Space Plasma Environment

Electrostatic discharge tests on solar array coupon of spacecraft were carried out to investigate the effect of temperature on the discharge frequency and threshold voltage of discharge inception. The tests were carried out under a plasma environment (low Earth orbit) and a high-energy electron beam environment (geosynchronous orbit). The discharge frequency increased with decreases of temperature, regardless of environment. The threshold voltage of discharge inception did not depend on the temperature, regardless of environment. These results show that we do not need to take into account the temperature effect on threshold voltage to estimate the number of discharges in orbit. However, the electrical material parameters, such as volume conductivity, change with the temperature. Therefore, we do need to monitor the temperature in the charging analysis.

Degradation of Cu(In, Ga)Se 2 thin-film solar cell due to electrostatic discharge

The discharge tests on CIGS arrays were performed in a vacuum chamber which simulates the plasma environment in low Earth orbit and the high-energy electron environment in geostationary orbit. Although no dielectric parts exist on CIGS array, the discharge occurred on the surface and caused cell degradation. The discharge track worked as a leak resistance. To avoid discharge on the surface, it is necessary to cover CIGS array with a transparent film.