A vehicle using XNAV would compare received X-ray signals with a database of known pulsar frequencies and locations.
[4] The Advanced Concepts Team of ESA studied in 2003 the feasibility of x-ray pulsar navigation[5] in collaboration with the Universitat Politecnica de Catalunya in Spain.
After the study, the interest in the XNAV technology within the European Space Agency was consolidated leading, in 2012, to two different and more detailed studies performed by GMV AEROSPACE AND DEFENCE (ES) and the National Physical Laboratory (UK).
[6] In 2014, a feasibility study was carried out by the National Aerospace Laboratory of Amsterdam, for use of pulsars in place of GPS in navigation.
[15] Finally, it has been suggested that advanced extraterrestrial intelligence might have tweaked or engineered millisecond pulsars for the goals of timing, navigation and communication.