Dawn Ion Propulsion System: Initial Checkout After Launch

摘要

The first 80 days after launch of the Dawn mission were dedicated to the checkout of the spacecraft with a major emphasis on the ion propulsion system. All three ion thrusters, all three thruster-gimbal assemblies, both power processor units, both digital interface and control units, and the entire xenon feed system were completely checked out, and every component was found to be in good health. Direct thrust measurements agreed well with preflight expected values for all three thrusters over the entire throttle range. Measurements of the thruster-produced roll-torque verified that each thruster produced less than the maximum allowed value of 60 μNm at full power. Thruster electrical operating parameters and power processor unit efficiencies also agreed well with preflight expected values based on acceptance test data. Two of the three ion thrusters were fully checked out within 30 days after launch. Checkout of all three thrusters was completed 64 days after launch. Deterministic thrusting with the ion propulsion system began on 17 December 2007.