Fixed Bias Probe Measurement of a Satellite Floating Potential

A simple sensor is described to measure satellite potentials. The proposed instrument consists of two small spherical Langmuir probes biased to different fixed voltages, from which currents are measured. A predictive model is constructed for spacecraft floating potentials by combining the orbital motion limited (OML) approximation for spherical probes, and a multivariate regression algorithm. Construction of the model is based on a training data set obtained from 3-D simulation results, covering a range of plasma parameters of relevance to satellites in low earth orbit (LEO) at midlatitudes. The model skill is then assessed by comparing predictions with potentials in a distinct validation data set. Owing to large satellite orbital speeds, fixed bias probes would provide measurements with higher temporal and spatial resolution than possible with sweep voltage probes.