Ion emission to actively control the floating potential of a spacecraft

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Ion emission to actively control the floating potential of a spacecraft

Schmidt, R. / Arends, H. / Nikolaizig, N. / Riedler, W.

Abstract Charging of the outer surface of a spacecraft in orbit has occasionally a severe impact on the science return from the instruments. The ISEE and GEOS spacecraft have shown that in their orbits potentials of, respectively, up to +50 and ≥ +8 V are not uncommon and make it practically impossible to measure the very cold component of the ambient plasma. They also have interfering effects on the electirc field measurements. With active neutralization of the electrostatic surface charge more accurate measurements are feasible. We report on the development of an active emission system for future magnetosPheric missions. Emitting energetic particles (3–5 keV) and simultaneously measuring the actual surface potential by an electric field instrument we aim at clamping the spacecraft potential to 1–2 V above the local plasma potential for most of the expected plasma conditions. Negative potentials (eclipses) will not be controlled as the payload will be inoperative. Our method requires that all surfaces be conductive.