Description: The Microcosm X-ray pulsar-based navigation and timing (XNAV) team will provide the software and modeling infrastructure for NASA to support XNAV operations, focusing on detailed X-ray source modeling. These models can be used to evaluate the potential of using measurements of photon energy and/or aperiodic sources to improve XNAV performance. Key goals are: characterize X-ray sources for navigation purposes; automate pulse shape catalogue tools; automate XNAV/pulsar noise prediction tools; aperiodic source evaluation; photon energy performance enhancement; create integrated catalogs of XNAV guide stars and XNAV-applicable aperiodic sources; identify and document the key periodic X-ray source characteristics impacting the performance of the XNAV instruments and system. This comprehensive characterization categorizes and provides the necessary parameters regarding these celestial sources that make them beneficial for spacecraft navigation. Based upon past research work, specific information about each unique X-ray source must be attained in order for the source to yield its optimum capabilities. We will identify the appropriate parameters for characterizing aperiodic or transient sources for their use in navigation. Additionally, the existing X-ray source catalogue will be updated and enhanced. Phase II will focus on implementing these source models in detailed XNAV simulations and potentially creating flight software versions of these models.

Benefits: The primary non-NASA XNAV applications would be to provide primary or secondary navigation services for DoD missions. For MEO, GEO, HEO, and even cis-lunar missions, where GPS has limited availability, XNAV can provide primary autonomous navigation capability. In addition, XNAV could provide an essential backup navigation capability for missions that normally rely on GPS, but have a need for continuity of operations in the event of loss or denial of GPS. These applications were being actively studied through DARPA's first XNAV program in 2004-06, and key Microcosm team members had strong ties to that program. All of these potential XNAV users would require up-to-date almanac information to support on-going operations.

XNAV is a game changing technology for NASA, enabling new missions, providing navigation autonomy and redundancy and offering a path to reduce the scheduling demands on DSN, a valuable NASA asset. There are several promising NASA applications for XNAV where the improvements in navigational accuracy will either enable new missions, or reduce their costs, including missions to the outer planets, and non-planetary missions to deep space. Missions to Mars and the moon can take advantage of the autonomous navigation capabilities of XNAV, providing redundancy and reducing the need for regular DSN contacts, lessening the burden on this over-taxed system, The new software tools proposed will support XNAV mission analysis and flight software implementation. The X-ray source almanac development and maintenance associated with this project would be required to support all of these applications.