Payload environment and gas release effects on sounding rocket neutral pressure measurements

Abstract

The Space Physics Experiments Aboard Rockets-3 sounding rocket carried a payload that performed active experiments to diagnose the physical mechanisms and test the effectiveness of several grounding schemes, to study high-voltage bias effects on the performance of solar cells, and to monitor the undisturbed plasma and neutral gas environment of the payload. As a part of that payload, the neutral pressure gauge obtained measurements of the pressure surrounding the payload both during and between the various active experiments. Neutral pressure results show a pressure elevated by as much as two orders of magnitude over atmospheric model-derived pressures for the entire flight. Neutral pressure measurements indicate that gas released during neutral gas (argon) releases, which was one of the mechanisms for grounding the payload, and attitude control system thruster firings (nitrogen) may be displacing the ambient gas, at least from the vantage point of the neutral pressure gauge. The prerelease ambient pressure appears to be the determining factor for whether a gas release causes an increase or decrease in the ambient pressure. Also, the decay time associated with these gas releases, or the time it takes for the measured pressure to return to ambient, is on the order of a few tenths to a few hundredths of a second once the gas valves are shut.