Spacecraft Charging: Meteosat Experience,

Abstract : Charging monitors on Meteosat 2 have given a large amount of very specific information about the interaction of the Meteosat 2 spacecraft with the plasma environment at geosynchronous orbit. Principal results so far include: 1) Differential charging occurs when part or all of the spacecraft is permanently in shadow and when there is a net flux of electrons to the spacecraft, 2) In an eclipse the current balance can charge from a triple root to a single root solution with a small charge in spectrum as had been predicted, 3) The level of differential voltages between adjacent parts of the spacecraft can be clamped at the relatively low voltage of the second cross-over point in the secondary emission yield curve (approx. volts), 4) Despite being inside a 1 metre long, conducting baffle the radiometer mirror caused significant charging of the spacecraft, 5) Although most of the anomalies of Meteosat 2 are probably not associated with arcing they do have a natural cause, 6) Where it is not possible for the outer surface of a spacecraft to be conducting, the harmful effects of differential charging can be reduced by use of materials with high secondary emission coefficients, 7)An electron albedo index, based on empirical values of secondary emission coefficients and backscatter ratios has been reasonably in determining the liability of the spacecraft to charging.