An external reference system suitable for deep space navigation can be
defined by fast spinning and strongly magnetized neutron stars, called pulsars.
Their beamed periodic signals have timing stabilities comparable to atomic
clocks and provide characteristic temporal signatures that can be used as
natural navigation beacons, quite similar to the use of GPS satellites for
navigation on Earth. By comparing pulse arrival times measured on-board a
spacecraft with predicted pulse arrivals at a reference location, the
spacecraft position can be determined autonomously and with high accuracy
everywhere in the solar system and beyond. The unique properties of pulsars
make clear already today that such a navigation system will have its
application in future astronautics. In this paper we describe the basic
principle of spacecraft navigation using pulsars and report on the current
development status of this novel technology.Comment: 22 pages, 12 figures, 2 tables, to be published in the proceedings of
the workshop "Relativistic Positioning Systems and their Scientific
Applications", held on 19-21 Sept. 2012, Brdo near Kranj, Sloveni