3.2.2 Assembly Level Requirements Most requirements imposed at the assembly level are related to environmental interactions. A summary of the most important environmental parameters is shown in the table below. The first column identifies the environmental factor, the second the resulting effects, the third the desired result of a technological solution, and the fourth column indicates the orbits where each specific environmental effect is important. New solar array requirements result from advances in technology, not changes in the environment. For example, the mechanical and optical damage from micrometeoroid impacts is well known and does not present any particular problem. However, as bus voltages rise (to 50 volts for telecommunications satellites and 120 volts for COLUMBUS) a new electrical failure mode has become a problem. Ground simulation tests have shown that the small volume of plasma generated by very small micrometeoroids is sufficient to trigger an arc discharge between the high voltage cell strings and the substrate or the wiring on the back of the panel. This arc could result in the short circuiting of complete sections. In LEO, similar plasma effects can be important at bus potentials above 100 volts. Long lifetime specifications are also important requirement drivers. Desired lifetimes of up to 10 years in LEO and GEO are now common. This means the solar cell interconnects and busbars must survive up to 30,000 thermal cycles from -100° to +100°C.
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