The term XNAV (X-ray navigation) is used to describe a variety of means of using celestial X-ray source observations for spacecraft attitude, position, velocity, and time determination. Several classes of source observations can be utilized for different aspects of the navigation process, as shown below.
- Pulsar Source Observations: time of arrival and phase (absolute navigation and time correction)
- Aperiodic Source Observations: noise intensity correlation across platforms (relative navigation and timing)
- Bright Source Observations: occultation by atmospheres or bodies (position and attitude determination)
- Bright Source Observations: X-ray band star camera (attitude determination)
For this paper the focus will be primarily on the exploitation of pulsar source observations as position, velocity, and time references.
Graven, P., J.T. Collins, J.E. Hansen and S.I. Sheikh. 7th International ESA Conference on Guidance, Navigation & Control Systems. Tralee, County Kerry, Ireland. June 2–5, 2008.