Observations of the Effect on Spacecraft Function and Communications by the ESEX 26kW Ammonia Arcjet

Abstract : Tests designed to detect the influence of operating the Electric Propulsion Space Experiment (ESEX) 26 kW ammonia arcjet on normal spacecraft communications and operations showed. Two on-board antennas sensitive to the 2, 4, 8, and 12 GHz frequencies detected no increase in signal amplitude that is clearly identifiable with arcjet operation. Analysis of the bit-error rate (BER) tests, a sensitive diagnostic for quantitatively measuring the effect of the arcjet plume on ground/spacecraft round trip communication, revealed no obvious correlation between arcjet operation and the observed increases in bit-error rate. Finally, a series of qualitative observations consistently indicated the benign nature of arcjet operation on normal spacecraft events. For example, commands uplinked without abnormal rejection rate and telemetry downlinked successfully during arcjet operation.