Performance of the Psyche Electric Propulsion System during the First Cruise Phase

Psyche is the first mission to use Hall thrusters in interplanetary space. The first phase of cruise thrusting operations began in April 2024 and ended in September 2025, with almost 8,000 hours of operation and 5.4 MN-s of impulse provided to date. Here we review the operation and performance of the electric propulsion subsystem over that period. Thruster electrical telemetry have been nominal and within expectations. Thrust reconstructions for three of the thrusters have been within 2% of pre-launch expectations, with Thruster B overperforming due to an out-of-family behavior identified prior to cruise operations. Thruster A has the most operating time of all thrusters, and comparison of the in-space performance to that of the ground-based life test over similar time periods shows that although both decrease to 92% of the original thrust, the in-space thrust did so suddenly compared to the gradual decrease in the life test. Thruster swirl torque has been measured regularly for all thrusters during the cruise phase, and we show that the Thruster A swirl torque near the 3.8-kW power level was unchanged after 2,800 hours of operation. Finally, we describe a significant fault that occurred in the propellant feed system during the cruise phase, how it was diagnosed, and the continuation of the mission using redundant hardware.