Navigation and coordination control system for formation flying satellites

This paper presents the design of a guidance, navigation and control (GNC) system for formation flying satellites in low Earth orbit. An innovative estimation approach employs a common extended Kalman filter (EKF) for the spaceborne autonomous control mode, which includes the J2 perturbations. A nonlinear least squares method is adopted for the ground-in-the-loop control mode. As a result, the navigation system can provide relative orbit information with a position accuracy of 3cm and a velocity accuracy of 0.2mm/s. The coordination control concept is detailed based on the relative orbital elements. Therefore, a three impulse method for configuration control is put forward which is simple and easy for engineer implement. Finally, an overview of the processor-in-the-loop testbed is given, which enables a seamless transition to real-time software simulations as well as hardware-in-the-loop simulations. The validation shows the simplicity and effectiveness of the navigation and control algorithms.