Synchronizing of Multiple Time-of-Arrivals for Pulsar-Based Navigation

Abstract

Spacecraft can observe multiple sources to achieve the goal of absolute position determination in pulsar-based navigation. In this paper, we draw attention to the problems associated with synchronizing of multiple time-of-arrival (TOA) measurements. The importance of this for navigation performance is not fully appreciated. Based on high-precision pulsar timing models, we establish the linear pulse phase measurement equation for near-Earth spacecraft and deduce the formulae of apparent pulse frequency (APF). We also develop the TOA synchronization model that uses APF to propagate pulse phases. We apply this model in numerical simulations that implement the extended Kalman filter (EKF) to estimate navigation states for geostationary (GEO) satellites. The results show that our model can effectively control navigation errors after TOAs are synchronized properly. We expect that the TOA synchronization technique presented in this paper may be useful for performance improvement of pulsar-based navigation.