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Cumulative electrostatic discharges (ESDs) on spacecraft solar cells result in the degradation of their performances. In this paper, silicon solar cells arc tested in inverted voltage gradient situation obtained in plasma. ENDs occurring on the cells are detected by both electrical and optical signatures. To be representative of flight ESDs. the test setup must avoid unwanted coupling with ground arcs. The degradation is then evaluated by measuring live current-voltage characteristic of the cell in darkness. The equivalent shunt resistance allows quantifying this degradation, which can he attributed to material deposition in the cell edge or to local cell carbonization due to arcing. Visual inspection of the cells allows us to correlate END location and local degradation of the cell. the important parameter for solar cell degradation is the amount of energy dissipated during the discharge. A model of the plasma expansion from the cathode spot is compared to measurement. This model explains the current rise during the first phase of the discharge, which is the value for normal ESDs and coupling with ground ESDs. [ABSTRACT FROM AUTHOR]

A good representativeness of the test setup used for the qualification of solar arrays is fundamental. We know now that the fiashover current involved in the electrostatic discharge is related with the total dielectric surface neutralized during the electrostatic discharge. This paper presents experiments on samples of different sizes, performed in a large vacuum chamber, JONAS, installed in ONERA/DESP, Toulouse, France. The samples are tested in the inverted voltage gradient configuration obtained with electrons. We observed that secondary arcs obtained on a large sample (i.e., with a long fiashover) had much longer durations than those on a small sample, i.e., the flashover is a critical parameter for secondary arc initiation and sustainment. [ABSTRACT FROM AUTHOR]

ONERA plasma tank JONAS is populated of drifting Ar+ argon ions representative of Low Earth Orbit environment, produced by a Kaufman source, and slow ions created by charge exchange with the background pressure of argon. When testing a mock-up or space equipment in this tank, it is often important to determine the drifting and slow ion densities in various locations. The orbital and radial motion models are compared to experimental current-voltage measurements and to numerical results. In the range of parameters used in this paper, the radial motion model is more adapted than the orbital-motion-limited model to determine slow ion density. Nevertheless, the number of measurements is necessarily limited and discriminating between fast and slow ions is not easy. A complementary approach consists in performing a numerical simulation of the plasma dynamics in the tank. Provided the modeled physics is validated, and the modeling is calibrated through measurements, this approach supplies fast and slow ion densities everywhere with an acceptable factor of uncertainty. This approach has been followed by characterizing in detail a given plasma configuration in JONAS and modeling it with Spacecraft Plasma Interaction Software open source code. The mock-up was a simple plate. We measured the plasma characteristics through numerous current-voltage sweeps and current space profiles at given probe potential. The modeling was based on fast ion beam measurements close to the source and the residual pressure. [ABSTRACT FROM AUTHOR]