The Time Equation of Light Propagation in XNAV

We discuss in detail the general relativistic effect in the X-ray sourcebased navigation for autonomous position determination program (XNAV). By using the post-Newtonian approximate method of the DSX scheme, we calculate the bending of light and the gravitational time delay under the 1PN metric, as well as the gravitational time delay under the 2PN metric, and finally obtain the high-accuracy time equation of light propagation in XNAV.