Ionospheric Plasma Electron Density Measurement and Theory Using Impedance Probe Techniques

The ionosphere plays a critical role in how radio frequency (RF) signals, like those used in Global Position System (GPS) satellite communications, travel through space. Disturbances in the ionosphere, such as equatorial plasma bubbles (EPB), scatter these signals and cause communication dropouts or navigational errors. To study these conditions, spacecraft use instruments that measure the surrounding plasma directly. One of these instruments is an impedance probe, which applies a small electrical signal to a sensor and determines electron density from the measured impedance. This thesis improves the modeling and interpretation of impedance probe measurements. A numerical method is developed that uses electric field data from computer simulations to calculate the impedance of realistic probe and spacecraft geometries. The influence of the sheath on the probe’s resonant frequencies is analyzed, and the results are compared to measurements from the Scintillation Prediction Observation Research Task (SPORT) satellite mission. The comparison shows that sheath effects have no effect on the measurement for plasma density, but need to be understood when comparing real-world data to theory. A new impedance probe circuit is also designed and tested to expand the measurement range and improve accuracy. These developments contribute to better electron density measurements.