Abstract: The Xray pulsar can provide navigation information of the position, velocity, attitude and time with highprecision autonomously for the spacecraft in the deepspace and nearEarth orbit. But for the spacecraft around the Earth, the pulsars are sometimes invisible due to the eclipse of the central body, so the visibility of pulsars becomes a key factor on the nearEarth navigation application of the Xray pulsars navigation (XPNAV). This paper analyzes the visibility of 30 pulsars picked for the 7 orbits of the Beidou System. The simulation results of the number of the visible pulsars in one day are obtained and the situations of the eclipse of the Sun, Erath and Moon in one year are also presented. The rules of the influence of the celestial bodies on the visibility of pulsars are summarized in this paper, which can provide a data support for the autonomous orbit determination and time keeping of the Beidou System by using the XPNAV.

Key words: Beidou navigation satellite system, Xray pulsar, visibility of pulsar, pulsars selection