High accuracy autonomous navigation of GNSS using X-Ray pulsar based navigation

Autonomous navigation of Global Navigation Satellite Systems (GNSS) can be realized with the newly developed X-ray pulsar navigation (XNAV). XNAV is an autonomous navigation method using the periodic signals of X-ray pulsars. Based on the reference point of phase comparison, the concepts of three XNAV modes are defined: standard mode, incremental mode, and relative mode. Their performances and requirements in the navigation of GNSS are examined, and the last two modes are recommended for their immunity to clock error and low requirement on pulsar timing model. Integrated navigation consists of XNAV and crosslink measurement is proposed to improve the navigation accuracy. Simulations are conducted to examine the effects of XNAV modes, pulsar number, estimation methods and clock error on navigation accuracy. The results show that when using XNAV alone in GNSS, only 2 pulsars are sufficient for total observability, and a positioning accuracy within 80 m can be achieved; when using integrated navigation, only 1 pulsar is needed to achieve a positioning accuracy within 4 m. The limitations and benefits of XNAV in GNSS are analyzed, based on the analysis and simulation results, XNAV is considered as a very promising autonomous navigation method for GNSS.