The SPEAR-1 experiment: high voltage effects on space charging in the ionosphere

The SPEAR-1 rocket payload, flown on December 13, 1987, exposed biased conducting spheres at potentials of tens of kV to the ambient space environment at altitudes as high as 370 km (apogee) in the night-time ionosphere. Small chamber tests of the mock-up demonstrated the conditions for breakdown caused by sphere bias, magnetic field, chamber size, and secondary emissive properties of the chamber wall. In flight the failure to expose the payload's plasma contactor to the ionosphere caused a bipolar operation with interacting sheaths from both the payload body and the biased conducting spheres. During sphere biasing no breakdowns occurred above 100 km, and the plasma sheath controlling the flow of currents from the ionosphere behaved as a linear resistance with a value in the 100s of kilo-ohms. >