Session P4a: Methods and Algorithms for Timing Applications and Timescales

Towards Operational Ready Multi-Constellation PPP/IPPP Links for UTC Computation
G. Tagliaferro, Bureau International des Poids et Mesures
Location: Beacon B
Date/Time: Thursday, Jan. 25, 9:20 a.m.

Global Positioning System (GPS) Precise Point Positioning (PPP) is one of the most widespread and accurate ways to perform time transfer on a global scale.
Since 2009 it has been used by the BIPM time department, to link UTC(k) for UTC calculation. Other Global Navigation Satellite Systems (GNSSs) have been successfully used to perform time transfer in PPP mode. Furthermore, in the last years, PPP with integer ambiguity resolution (IPPP) has been shown to improve considerably the stability of time transfer. Both PPP and IPPP are possible thanks to the precise ephemerids computed by the different analysis centers of the International GNSS Service (IGS).
The BIPM time department is actively working on the evolution of its GNSS links. In this contribution, the performance of a novel combined GPS and Galileo PPP / IPPP solution is evaluated for the purpose of UTC computation.
The presented solution is based on the least squares adjustment using monthly batches of pseudorange and phase data and will make use of rapid IGS integer product ephemerids. The presentation will discuss the chosen parametrization, the GPS-Galileo intersystem biases, the use of sparse algebra routines, the ambiguity fixing and the performance of the novel links versus Two-Way Satellite Time and Frequency Transfer (TWSTFT) and other IPPP solutions.
Finally, day boundary discontinuities present in the IGS rapid clock solution will be discussed and a methodology to repair them will be presented.