The Space Technology 7 Disturbance Reduction System ( ST7-DRS ) is a NASA technology demonstration payload that operated from January 2016 through July of 2017 on the European Space Agency ’ s LISA Pathfinder spacecraft .
The joint goal of the NASA and ESA missions was to validate key technologies for a future space-based gravitational wave observatory targeting the source-rich milliHertz band .
The two primary components of ST7-DRS are a micropropulsion system based on colloidal micro-Newton thrusters ( CMNTs ) and a control system that simultaneously controls the attitude and position of the spacecraft and the two free-flying test masses ( TMs ) .
This paper presents our main experimental results and summarizes the overall the performance of the CMNTs and control laws .
We find that the CMNT performance to be consistent with pre-flight predictions , with a measured system thrust noise on the order of 100 \textrm { nN } / \sqrt { \textrm { Hz } } in the 1 \textrm { mHz } \leq f \leq 30 \textrm { mHz } band .
The control system maintained the TM-spacecraft separation with an RMS error of less than 2 nm and a noise spectral density of less than 3 \textrm { nm } / \sqrt { \textrm { Hz } } in the same band .
Thruster calibration measurements yield thrust values consistent with the performance model and ground-based thrust-stand measurements , to within a few percent .
We also report a differential acceleration noise between the two test masses with a spectral density of roughly 3 \textrm { fm } / \textrm { s } ^ { 2 } / \sqrt { \textrm { Hz } } in the 1 \textrm { mHz } \leq f \leq 30 \textrm { mHz } band , slightly less than twice as large as the best performance reported with the baseline LISA Pathfinder configuration and below the current requirements for the Laser Interferometer Space Antenna ( LISA ) mission .