Title of Thesis: APPLICATION OF X-RAY PULSAR NAVIGATION: A CHARACTERIZATION OF THE EARTH ORBIT TRADE SPACE

Title of Thesis: APPLICATION OF X-RAY PULSAR NAVIGATION: A CHARACTERIZATION OF THE EARTH ORBIT TRADE SPACE Wayne Hong Yu, Master of Science, 2015 Thesis directed by: Dr. Liam Healy Department of Aerospace Engineering The potential for pulsars as a navigation source has been studied since their discovery in 1967. X-ray pulsar navigation (XNAV) is a celestial navigation system that uses the consistent timing nature of X-ray photons from milli-second pulsars (MSP) to perform space navigation. Much of the challenge of XNAV comes from the faint signal, availability, and distant nature of pulsars. This thesis is the study of pulsar XNAV measurements for extended Kalman filter (EKF) tracking performance within a wide trade space of bounded Earth orbits, using a simulation of existing X-ray detector space hardware. An example of an X-ray detector for XNAV is the NASA Station Explorer for X-ray Timing and Navigation (SEXTANT) mission, a technology demonstration of XNAV set to perform on the International Space Station (ISS) in 2016. The study shows that the closed Earth orbit for XNAV performance is reliant on the orbit semi-major axis and eccentricity as well as orbit inclination. These parameters are the primary drivers of pulsar measurement availability and significantly influence the natural spacecraft orbit dynamics. Sensitivity to initial orbit determination error growth due to the scarcity of XNAV measurements within an orbital period require appropriate timing of initial XNAV measurements. The orbit angles of argument of perigee and right ascension of the ascending node, alongside the other orbit parameters, complete the initial cadence of XNAV measurements. The performance of initial XNAV measurements then propagates throughout the experimental period. APPLICATION OF X-RAY PULSAR NAVIGATION: A CHARACTERIZATION OF THE EARTH ORBIT TRADE SPACE