Characterization of Pulsar Sources for X-ray Navigation

TL;DR

This paper discusses the development and potential of X-ray pulsar navigation using NICER/SEXTANT, highlighting measurement error factors, catalog properties, and prediction challenges for autonomous space navigation.

Contribution

It introduces the SEXTANT system for real-time X-ray pulsar navigation and analyzes factors affecting its accuracy and future catalog growth.

Findings

Measurement errors depend on source/background count rates and pulse profiles.

The SEXTANT pulsar catalog's properties influence navigation accuracy.

Prediction of pulse arrival times is affected by interstellar effects and timing noise.

Abstract

The Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) is a technology demonstration enhancement to the Neutron Star Interior Composition Explorer (NICER) mission, which is scheduled to launch in 2017 and will be hosted as an externally attached payload on the International Space Station (ISS). During NICER's 18-month baseline science mission to understand ultra-dense matter through observations of neutron stars in the soft X-ray band, SEXTANT will, for the first-time, demonstrate real-time, on-board X-ray pulsar navigation. Using NICER/SEXTANT as an example, we describe the factors that determine the measurement errors on pulse times of arrival, including source and background count rates, and pulse profile shapes. We then describe properties of the SEXTANT navigation pulsar catalog and prospects for growing it once NICER launches. Finally, we describe the factors affecting the prediction of pulse arrival times in advance, including variable interstellar propagation effect and red timing noise. Together, all of these factors determine how well a particular realization of an X-ray pulsar-based navigation system will perform.