Preliminary analysis and performance evaluation of the XNAV technique

Pulsar-based Navigation is an emerging technique to help deep space positioning. The idea, alike GNSS, is to make use of beacons in well-known locations to compute the kinematic state of a space vehicle equipped with suitable receivers. Opposite to GNSS, these sources of signal are not man-made while found in nature, and offered by peculiar stars offering a typical, extremely precise emission pattern, i.e. the X-ray pulsars. The paper quickly recalls the fundamental concepts for this technique, then reports some interesting relations allowing to select the better sources and to evaluate the attainable accuracy. After presenting the fixing procedure, some more original discussion about the geometric dilution of precision is included, together with results useful for a preliminary analysis.