CHARGE EXCHANGE IONS PRODUCED BY AN ION PROPULSION SYSTEM

In this paper, we present observations of charge exchange ions generated by the ion propulsion system (IPS) on the Deep Space One (DS1) spacecraft . We show that the equilibrium flux of charge exchange ions correlates well with IPS thrust levels, but that the flux requires approximately 4 hours to build up to equilibrium value after the start of IPS operation. In time of flight mass spectra, these ions appear as a broad peak which is consistent with a mixture of singly charged xenon and molybdenum and doubly charged xenon. We can not directly distinguish between these species, since the instrument was not operating at its designed high voltage levels during 1999. The instrument will operate at higher voltages during 2001, which should allow us to determine the composition of these ions. In addition, the data clearly show the presence of N+ at times when ion propulsion system and the spacecraft's hydrazine reaction control thrusters both in use.