Stephenson_2011abstr

Copyright © 2011 by Gary V. Stephenson. Published by the Mars Society with permission.

M2M XNAV:

X-ray Pulsar Navigation for Missions to Mars

Gary V. Stephenson

Linquest Corporation, Los Angeles, CA

425-443-8651, gary.stephenson@linquest.com

ABSTRACT
While X-ray pulsar navigation (XNAV) has been studied intensively over the past decade, working space based X-ray detectors have thus far been limited to dedicated missions, payloads, and demonstrations. The application of X-ray detectors to XNAV applications still awaits much reduced volume, mass, and complexity in X-ray detectors before becoming a practical reality.

In the present paper mission operational scenarios of typical missions to Mars (M2M) are used in conjunction with the inherent characteristics and limitations of X-ray pulsar navigation to develop a reference architecture for an on board autonomous XNAV system that would serve to provide navigation control for Mars bound and Mars to Earth returning spacecraft. XNAV characteristics are presented, including pulsar source characteristics, important database parameters, a hardware approach, software algorithm characteristics, and proposed XNAV system characteristics, such as a possible Kalman filter implementation for comparing predicted time of arrival (TOA) with measured TOA. Software considerations include matching detections to pulsar database entries, conversion of detections from local time into Barycentric Coordinate Time (TCB), and the calculation of position updates based on these measurements.

Keywords: Pulsar, X-ray, Navigation, XNAV, Barycentric Coordinate Time, TCB, Time of arrival, TOA, Kalman, Filter.

PACS: 97.60.Gb, 95.55.Ka, 87.59.-e, 95.10.Eg, 95.10.Jk, 95.30.Sf, 84.40.Ua