Spacecraft Navigation and Timing Using X-ray Pulsars

Pulsars are unique celestial sources that produce distinctive, periodic signals. Since their discovery, they have been considered as potential navigation aids and timing beacons to form a reference coordinate system and universal time scale. Further study of these astronomical objects has shown that their pulse timing can achieve sub-microsecond level performance, and interest and research into these sources has grown to conceive a fully autonomous navigation and timing system for deep space vehicles. Sources that radiate within the X-ray band of the electromagnetic spectrum have high potential for creating a practical spacecraft navigation solution, which includes accurate time and position determination onboard a space vehicle using the precisely periodic sources, and precise attitude determination using both pulsating and steady sources. This paper provides an overview of spacecraft navigation methods and various research and results that have evolved since the concept of X-ray pulsar-based navigation was first proposed.