Contaminated Sweeping Langmuir Probes on Sounding Rocket Platforms

Sweeping Langmuir Probes (SLPs) are one of the most commonly used probes on sounding rocket missions. They offer measurements of plasma density, electron temperature, and both relative and absolute payload charging. One of the major implementation challenges, however, is contamination on the surface of the probe such that collected IV curves become distorted. This distortion can result in deflated densities, inflated temperatures, and erroneous charging measurements. This dissertation aims to expand our understanding of contamination's impact on SLP data and offer new mitigation methods appropriate for the sounding rocket platform. SPICE, Simulation Program with Integrated Circuit Emphasis, is used to simulate a contaminated Sweeping Langmuir Probe onboard a sounding rocket. The results are used to characterize regimes of contamination effects and assess the reliability of data analysis techniques for all reasonable contamination layer properties. This work also conducts the first in-depth analysis of charge accumulation across the layer, addressing observed behaviors in SLP in-situ data. The inclusion of this property has major implications on our understanding of contaminated probe behavior, as there are no applied sweep rates that are effective in bypassing all contamination effects. This result also suggests that a lack of apparent distortion is not an appropriate metric for probe cleanliness. SPICE simulations and in-situ data from the APEP (Atmospheric Perturbations around Eclipse Path) sounding rocket mission demonstrate the impacts of voltage sweep profiles on contaminated probes. These design considerations made prior to launch can have irreversible and detrimental effects on the SLP's behavior. We use simulation results to present the most favorable sweep profile to mitigate these effects. Finally, methods have been presented in the literature to extract the contamination layer's properties during post-flight analysis, but they rely on underlying assumptions that fail when charge accumulation is considered. We use simulation to test the reliability and practicality of this method for the range of expected layer properties. In most cases, the associated error for both contamination resistance and capacitance is outside acceptable limits, and both values are severely underestimated.