Drag-free control (DFC) is one of the key technologies for space-borne gravitational wave detectors. For the TianQin project, non-gravitational disturbances on the spacecraft must be suppressed by DFC. TianQin-1 is the first satellite for technology verification, whose main goal is to verify the disturbances reduction technologies. In this paper, the DFC requirement and preliminary analysis for the TianQin project are introduced, and then the design and the experimental validation with the TianQin-1 satellite is presented. In-orbit results show a successful validation of DFC and the residual acceleration of TianQin-1 satellite has been suppressed to 5×10-11 m/s2/Hz1/2 at 10 mHz versus 2×10-9 m/s2/Hz1/2 thruster noise.

Seismic noise is one of the main limits of performance validation experiments for space inertial sensor on the ground. A two-stage electrostatically controlled torsion pendulum was developed and used to investigate the performances of space inertial sensor for TianQin. To further suppress the seismic noise effect, a novel scheme that introduces another pendulum to suspend the electrode housing simultaneously is proposed. By choosing proper suspension for the electrode housing with respect to the original pendulum for the test mass, the relative motion between the test mass and the electrode housing is insensitive to seismic noise due to common mode rejection, and the disturbance on the inertial sensor caused by seismic noise can be suppressed about five orders of magnitude theoretically. Both theoretical analysis and experimental results show that the scheme can further suppress the seismic noise effect more than one order of magnitude.

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