High-Current ESD Test of Advanced Triple Junction Solar Array Coupon

Abstract

A test was conducted on an Advanced Triple Junction (ATJ) coupon that was part of a risk reduction effort in the development of a high-powered solar array design by SSL. The ATJ coupon was a small, 4-cell, two-string configuration that has served as the basic test coupon design used in previous SSL environmental aging campaigns. The coupon has many attributes of the flight design; e.g., substrate structure with graphite face sheets, integrated by-pass diodes, cell interconnects, RTV grout, wire routing, etc. The objective of the present test was to evaluate the performance of the coupon after being subjected to induced electrostatic discharge testing at two string voltages (100 V, 150 V) and four array current (1.65 A, 2.0 A, 2.475 A, and 3.3 A). An ESD test circuit, unique to SSL solar array design, was built that simulates the effect of missing cells and strings in a full solar panel with special primary arc flashover circuitry. A total of 73 primary arcs were obtained that included 7 temporary sustained arcs (TSA) events. The durations of the TSAs ranged from 50 µs to 2.9 ms. All TSAs occurred at a string voltage of 150 V. Post-test Large Area Pulsed Solar Simulator (LAPSS), Dark I-V, and By-Pass Diode tests showed that no degradation occurred due to the TSA events. In addition, the post-test insulation resistance measured was > 50 G-ohms between cells and substrate. These test results indicate a robust design for application to a high-current, high-power mission application.

Tailoring Organic/Inorganic Interface Trap States of Metal Oxide/Polyimide toward Improved Vacuum Surface Insulation

“…ESD damage increases with the operating electric fields, hence rendering formidable challenges to the spacecraft operation with the increasing demand for high voltage and high power devices in the next-generation aerospace design. 18 This motivates innovative approaches to suppress SEEA and prevent ESD, especially designing new PI films with high surface insulation strength. Extensive attempts have been made to improve vacuum surface insulation, for example, creating microstructures on the surface, 23−25 coatings that facilitate surface charge dissipation, 26−28 and materials with low secondary electron yield (SEY).…”

“…It has been demonstrated that the cascade of secondary electrons (SEs) above the dielectric surface, also called secondary electron emission avalanche (SEEA), is one of the primary causes of the surface charging and discharging effects on spacecrafts. − The breakdown voltage of the vacuum-dielectric interface is much lower than the dielectric bulk and pure vacuum under the same insulation distance; , thus, the ESD will preferentially occur over the vacuum-dielectric interface (i.e., flashover) when the applied electric field exceeds a certain threshold. ESD damage increases with the operating electric fields, hence rendering formidable challenges to the spacecraft operation with the increasing demand for high voltage and high power devices in the next-generation aerospace design . This motivates innovative approaches to suppress SEEA and prevent ESD, especially designing new PI films with high surface insulation strength.…”

Arcing on Solar Generators by Collection of Ionospheric Plasma Currents

“…This IPG is generally observed on the front face of solar arrays when the spacecraft is negatively charged due to charging events such as geomagnetic storms and the coverglasses are less charged due to both photoemission and secondary electron emission. This condition triggers electrostatic discharges leading possibly to secondary arcs [6], [7], [8].…”

The characteristics of primary and secondary arcs on a solar array in low earth orbit

“…Satellite operational voltage has also increased to reduce power loss. The bus voltage of LEO spacecraft used to be 28 V or 42 V, and now the bus voltage of LEO spacecraft is up to 100 V or more [1,2]. The string voltages and string currents of solar arrays have also increased in satellite power systems.…”