Autonomous and Precise Navigation of the PROBA-2 Spacecraft

PROBA-2 is the second technology demonstration mission within the project for onboard autonomy of the European Space Agency (ESA). Besides other instruments and sensors, the micro-satellite will be equipped with two new types of global positioning system (GPS) receivers. These will support the spacecraft operations and demonstrate recent advances in the field of autonomous real-time navigation and offline orbit determination for micro-satellites. The paper provides an overview of the key PROBA-2 navigation elements and discusses their scope and capabilities. Special attention is given to the Phoenix-XNS miniature GPS receiver and its embedded navigation function which are presented along with a discussion of the employed filtering and processing algorithms. The impact of PROBA-2 attitude changes on the GPS tracking is analyzed and the employed strategies for minimizing possible outages are presented. Hardware-in-the loop simulations in a signal simulator testbed are used to demonstrate the feasibility of 1 m level real-time navigation using a single-frequency GPS receiver and to demonstrate the overall robustness of the PROBA-2 onboard navigation