Plasma Analyzer for Measuring Spacecraft Floating Potential in LEO and GEO

A design for a plasma analyzer for measuring spacecraft floating potential is described. The proposed Plasma Analyzer for Space Science (PASS) would use two methods simultaneously to determine spacecraft charge. Floating potential to kilovolts negative may be determined by the energy analysis of positively charged particles (ions) through the low energy ion cutoff method. Floating potentials from a few tens of volts negative to the highest positive potentials expected may be measured though the electron-spectroscopic method. The use of two charge-sensing techniques should allow a large range of both positive and negative floating potentials to be measured. The simultaneous use of two dissimilar methods enables the refinement of both methods and should improve the reliability of spacecraft floating potential measurement. PASS should be able to determine spacecraft floating potential in both low Earth orbit and geosynchronous Earth orbit from -10 kV to the largest positive floating potential expected. Based on what was learned from the development of the Spacecraft Charge Monitor, PASS should have superior performance in energy resolution, geometric factor, and data-gathering efficiency compared to charged particle energy analyzers that have been used in the past.