The LISA Pathfinder (LPF) Mission, a joint ESA-NASA mission, is a demonstration mission of technologies needed for future laser interferometry gravity wave observatory missions. Such missions would consist of multiple spacecraft flying in formation with each spacecraft surrounding a proof mass at the end of a laser interferometer leg. The spacecraft is used to shield the proof mass from disturbances such as the solar wind. Among the technologies to be demonstrated on LPF are micro-propulsion thrusters that are part of the Disturbance Reduction System (DRS) designed to maintain the spacecraft position relative to the proof mass within 10 nm. Both cesium Field Emission Electric Propulsion (Cs-FEEP) thrusters and Colloid Micro-Newton Thrusters (CMNT) are candidate micro-propulsion technologies for these missions. It is possible that both Cs-FEEP and CMNT thrusters may be flown on the same spacecraft in a future mission. If both types of thrusters are flown on the same spacecraft it is likely that a neutral cesium flux from the Cs-FEEP will impinge on the CMNT. A monolayer of cesium on the CMNT insulator would cause the impedance between electrodes to decrease below the 10 Gil level required for the thruster to operate properly. Modeling and testing was performed to determine if cesium exposure would cause the CMNT insulator impedance to decrease enough to cause a failure or degraded CMNT performance. Cesium exposure testing of a CMNT was performed at ESTEC. The test conditions were more severe than the conditions expected in space during a mission. The CMNT passed the test with full operational capability indicating that cesium exposure would not be a problem during a mission.
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