RF signal impact study of an SPT

Stationary plasma thrusters (SPTs) are currently being tested and considered for use aboard next generation spacecraft for North-South stationkeeping, repositioning, and orbit transfer due to their high thrust efficiency and nearly optimal specific impulse (Isp). However, because the thruster's plume generates plasma densities with corresponding plasma frequencies approaching 3 GHz, consideration must be given to possible interactions with satellite electromagnetic systems (communication, navigation, remote-sensing). The plume potentially can degrade the EM link through attenuation as well as added amplitude or phase noise. We provide the physical mechanism and ray tracing modeling method to understand the possible amplitude modulation produced by the SPT thruster and experimentally quantify the rather significant plume impact to phase and amplitude for a signal at 1.575 GHz (GPS frequency) which is outside the theoretical limit of the modeling technique. (Author)

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