Atom-interferometry gravity gradiometry has been developed as a promising technique for future gravity gradiometric missions after GOCE due to its greater sensitivity in micro-gravity environments and constant performance over the measurement bandwidth. In this paper, a feasible method of spaceborne atom-interferometry gravity gradiometry is proposed by utilizing the free-fall condition of the cold atoms in space. Compared with GOCE, which shows an in-orbit noise performance of 10~20 mE/Hz^1/2, the scheme described in this paper would achieve a high sensitivity of 1.9 mE/Hz^1/2 for gravity gradients measurement by reducing the orbital altitude and optimizing the interrogation time for atom interferometry. The results show that the proposed scheme could significantly augment the spectral content of the gravity field in the degree and order of 280~316 and resolve the global gravity field with an improved accuracy of 0.2 cm@100 km and 0.85 cm@80 km in terms of geoid height, and 0.06 mGal@100 km and 0.3 mGal@80 km in terms of gravity anomaly after 1270 days of data collection.

A novel non-contact spacecraft architecture with the extended stochastic state observer for disturbance rejection control of the gravity satellite is proposed. First, the precise linear driving non-contact voice-coil actuators are used to separate the whole spacecraft into the non-contact payload module and the service module, and to build an ideal loop with precise dynamics for disturbance rejection control of the payload module. Second, an extended stochastic state observer is enveloped to construct the overall nonlinear external terms and the internal coupled terms of the payload module, enabling the controller design of the payload module turned into the linear form with simple bandwidth-parameterization tuning in the frequency domain. As a result, the disturbance rejection control of the payload module can be explicitly achieved in a timely manner with out complicated tuning in actual implementation. Finally, an extensive numerical simulation is conducted to validate the feasibility and effectiveness of the proposed approach.

In order to achieve the attitude maneuver performance of the noncontact close-proximity formation satellite architecture, this paper presents a compound control strategy with variable-parameter sliding mode control and disturbance observer-based feedforward compensation. Firstly, the variable-parameter sliding mode control is proposed to guarantee the attitude maneuver performance of the payload module. Secondly, the collision avoiding control with disturbance observer-based feedforward compensation is proposed to guarantee the synchronization of the two separated modules within the small air clearance constraint of the noncontact Lorentz actuator. Finally, a physical air-floating platform is established to verify the effectiveness of the proposed approach.