The Spacecraft Charging and Instrument Calibration Laboratory (SCICL) is now operational at Kirtland AFB, Albuquerque, NM. SCICL is a comprehensive one-stop shop for testing R&D spacecraft solar array coupons, novel materials, dielectric charging, and modeling of spacecraft effects from relevant materials. Electron guns of up to lOOkeV or LEO plasma sources reproduce the charging environment Characterization of sample charging and the chamber environment is done through TREK probes and plasma probes mounted on an up-to four axes of motion system. In addition to the ISO-11221 testing, a round-robin test has begun with SCICL and other US charging laboratories to characterize the rate of spacecraft discharging through the so-called "flashover" current The rate of discharge through the fiashover determines the ESD current waveform. If the expanding plasma completely discharges all dielectrics, all of the spacecraft surface capacitances will add to the total discharge current and energy. If the expanding plasma discharges surfaces only slowly and incompletely, the currents will be less and the total energy released will be less. Finally, if the ESD arc-current stops before all the surfaces are discharged, the total discharge energy will be severely curtailed. Thus, the expansion rate of the flashover plasma and the degree to which it discharges surfaces can mean the difference between a rapid, high current event, which may lead to power system disruptions, damaged solar cells, or even a sustained discharge on solar array surfaces or a slow, low current event, which leads to no disruptions or damage. During the flashover ESD, the plasma environment is expected to change in density by several orders of magnitude in a span of microseconds. In order to characterize this highly dynamic plasma environment, a series of triple-Langmuir probes are proposed. Design and implementation of the triple-Langmuir probes are considered, including the possibility of log-response probes.
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