Xibin Cao

Analytical approximate solutions to ground track adjustment for responsive space

This paper analyzes a civilian or military responsive space mission, in which a specific Earth site needs to be visited in a short time. Approximate analytical solutions for single and dual coplanar impulsive maneuvers to move from initial circular/elliptical orbit to final circular/elliptical orbit whose ground track passes over the Earth site are provided. The problem is solved by computing the semimajor axis of the final orbit by setting the transfer time equal in terms of Keplers equation and of Greenwich mean sidereal time (GMST). Using an unperturbed Keplerian model, a closed-form solution is obtained by solving a cubic polynomial. Then, by converting mean to osculating orbital elements, the linear J2 perturbed exact overflight solutions are obtained for impulses and corresponding time instants. Moreover, the exact overflight solutions are extended when using a conical sensor. Several numerical examples with various initial and final orbits are provided to validate this approach.

Optimal virtual center selection for formation flying maintenance

Purpose – The purpose of this paper is to propose a fuel‐optimal virtual centre selection method for formation flying maintenance in the J2 perturbed environment.Design/methodology/approach – Based on the relative orbital elements (ROE) theory, the J2 perturbed relative motions between different satellites in the formation are analyzed, and then the fuel‐optimal virtual centre selection issue for formation flying maintenance are parameterized in terms of ROE. In order to determine the optimal virtual centre, two theories are proposed in terms of ROE.Findings – Numerical simulations demonstrate that the fuel‐optimal virtual centre selection method is valid, and the control of the ROE of each satellite with respect to a virtual optimal centre of the formation is more efficient regarding the fuel consumption than the control of all satellites with respect to a satellite belonging to the formation.Research limitations/implications – The fuel‐optimal virtual centre selection method is valid for formation flyin...

Configuration, Orbit Design of InSAR Formation Based on Mean Elements

A mission requirements-based configuration method of interferometric synthetic-aperture radar (InSAR) formation to design dual-satellite formation by mean orbital elements is derived. The configuration and initial orbital elements of two coordinated running satellites InSAR formation are designed when system parameters, such as the resolution of slant distance, latitude domain of ground coverage area, and the side-looking angle of the synthetic-aperture radar (SAR) beam center, are given.

Fault-tolerant sliding mode attitude tracking control for flexible spacecraft with disturbance and modeling uncertainty:

This article investigates the attitude tracking control problem for a class of flexible spacecraft with a redundant four reaction wheels’ setting. In this study, inertia uncertainties, external disturbance, wheel torque saturation, and configuration misalignment are taken into account simultaneously. Two types of sliding mode controllers are presented to solve this design problem. First, supposing the norm upper bound of external disturbances, bounds of inertia, and input uncertainties are available, a terminal sliding mode attitude tracking control strategy is developed, where the controller and steering laws are synthesized together. Second, supposing these norm upper bounds are unavailable, an adaptive control law is designed to cope with attitude tracking problem. Under both control schemes, the system trajectory can be ensured to arrive on the specified sliding surface in finite time. Finally, an illustrative example is given to verify the effectiveness of the proposed attitude tracking control methodologies.

Robust Attitude Tracking Control for Spacecraft with Quantized Torques

The problem of spacecraft attitude tracking with limited communication to actuators is addressed in this paper. A hysteresis quantizer is employed to quantize the signal of control torque. The hysteresis quantizer requires low communication rate and avoids control chattering. An indirect (nonregressor-based) robust adaptive control scheme is proposed to deal with the effects of quantization error and external disturbances. The proposed control scheme together with the quantizer ensures global boundedness of all the signals in the closed-loop system and enables the attitude tracking error to converge toward a residual.