A Flexible Ephemeris Representation for GNSS and Alternative PNT Signal Sources Using B-Splines

Mikaela Dobbin and Penina Axelrad

Peer Reviewed

Abstract: Most global navigation satellite systems (GNSSs) ephemeris representations require straightforward, albeit specialized algorithms to compute the transmitter position at a time of interest. As potential positioning, navigation, and timing (PNT) signal sources expand beyond medium Earth orbit, these representations must be modified to capture the dynamics of the host platforms. This work introduces the use of B-splines as a flexible framework to represent transmitter ephemerides that are applicable to any orbital or airborne regime and host platform. With this approach, the user equipment implements a simple, generic algorithm to compute transmitter positions from the B-spline representation that require no orbit or platform specific models. Here we propose a B-spline ephemeris approach in which we compare the required navigation message length and fit accuracy to the legacy Global Positioning System (GPS) broadcast for use with medium Earth orbit transmission. We also demonstrate the applicability of this approach for a PNT satellite in low Earth orbit.
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