  Usually, positions of spacecraft on interplanetary or deep space missions are
determined by radar tracking from ground stations, a method by which
uncertainty increases with distance from Earth. As an alternative, a spacecraft
equipped with e.g. an X-ray telescope could determine its position autonomoulsy
via onboard analysis of X-ray pulsar signals. In order to find out which
pulsars are best suited for this approach and what accuracy can be achieved, we
build up a database containing the temporal emission characteristics of the ~
60 X-ray pulsars for which a pulsed radiation has been detected by mid 2010.
