Impact of anode layer thruster plumes on satellite communications
Microwave interferometry was used to investigate the impact of the plume of a D-55 anode layer thruster on satellite communications. A 17 GHz microwave signal was transmitted through the plume in order to measure phase shift and signal attenuation at various axial positions and discharge voltages. At 0.25 m from the thruster exit plane, a centerline phase shift of 37° was measured with a half-angle at full width half maximum of 22° for the nominal 300 V discharge. At 1.00 m, the phase shift had decreased to 20° and the half-angle to 13.5°. Signal attenuation measurements showed attenuations of -1.0 dB to -1.4 dB near centerline, but in a double peaked structure that appeared to reflect the annular nature of the plume. Increasing the discharge voltage had no measurable effect on either the phase shift or signal attenuation. Electron number density distributions were calculated by Abel inverting the signal phase shift. For the 300 V discharge, the centerline number density decreased from 1.0*1011 cm-3 at 0.25 m to 2.1*1010 cm-3 at 1.00 m. Analysis of the distributions indicates that electrons are not focused by increasing discharge voltage.
