Noise analysis for X-ray navigation systems

Much as the Global Positioning System has ushered in an era of autonomous navigation on a global scale, X-ray navigation (XNAV) offers the possibility of autonomous navigation anywhere in the solar system. X-ray astronomers have identified a number of X-ray pulsars whose pulsed emissions have stabilities comparable to atomic clocks. X-ray navigation uses phase measurements from these sources to establish autonomously the position of the detector, and thus the spacecraft, relative to the solar system barycenter. This paper describes the development of a general noise model for X-ray navigation instruments. Key noise terms are identified and simple analytic expressions provided for each. This noise model is used to predict the performance of a typical XNAV system that could be used as the primary navigation resource on missions, including those beyond the orbit of Jupiter.